United States Health Eite^ts
Environmental Protection L/-.'->oid'(,iy
Agency Cincinnati OH
Research and Development
'/EPA Wastewater
Aerosols
and Disease
Do not remove. This document
should be retained in the EPA
Region 5 Library Collection.
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EPA-600/9-80-028
December 1980
Wastewater Aerosols
and Disease
Proceedings of a Symposium
September 19-21, 1979
Sponsored by the
Health Effects Research Laboratory
Edited by
H. Pahren and W. Jakubowski
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
This document is available to the public through the National Technical Information Service,
Spnnfield, Virginia 22161.
230 South Dearborn Str-t
Ch'wgo, Illinois 60504
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DISCLAIMER
This report has been reviewed by the Health Effects Research
Laboratory, U.S. Environmental Protection Agency, and approved for
publication. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
U,S. Environmental Protection Agency
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Ill
FOREWORD
The U.S. Environmental Protection Agency was created because of
increasing public and government concern about the dangers of pollu-
tion to the health and welfare of the American people. Noxious air, foul
water, and spoiled land are tragic testimony to the deterioration of our
national environment. The complexity of that environment and the in-
terplay between its components require a concentrated and integrated
attack on the problem.
Research and ^development is that necessary first step in problem
solution; it involves defining the problem, measuring its impact, and
searching for solutions. The primary mission of the Health Effects Re-
search Laboratory in Cincinnati (HERL) is to provide a sound health
effects data base in support of the regulatory activities of the EPA. To
this end, HERL conducts a research program to identify, characterize,
and quantify harmful effects of pollutants that may result from exposure
to chemical, physical, or biological agents found in the environment. In
addition to the valuable health information generated by these activities,
new research techniques and methods are being developed that contrib-
ute to a better understanding of human biochemical and physiological
functions and how these functions are altered by low-level insults.
These proceedings represent an attempt to publish current knowledge
on the human health aspects of exposure to microbial aerosols from
wastewater treatment plants. With a better understanding of these
health effects, design engineers, municipal officials, and persons in-
volved with regulatory decisions can make more informed judgments on
the siting and operation of such plants.
R. J. GARNER
Director
Health Effects Research Laboratory
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iv
PREFACE
Many wastewater treatment plants are constructed in urban areas
close to residential areas. These systems generally contain aeration bas-
ins or trickling niters where there is an opportunity for small droplets of
wastewater to be emitted. These droplets, which could contain a bacter-
ium or virus, evaporate very rapidly to yield small droplet nuclei known
as aerosols.
A number of persons have investigated the types of organisms emitted
and their concentration in the air as a function of distance from the
treatment plant. These microorganisms travel passively with the wind,
and their concentration decreases with time and distance as a result of
atmospheric dispersion, die-off, and deposition. The potential for plant
workers and nearby residents to inhale viable organisms certainly exists.
However, there has never been a systematic investigation to confirm or
negate the existence of a health hazard from these viable wastewater
aerosols.
With this background, the Health Effects Research Laboratory of the
U.S. Environmental Protection Agency arranged for several epidemiol-
ogical studies to gather information on health effects associated with
aerosols from uncovered wastewater treatment plants. These studies
were conducted by personnel from universities or research institutions.
The purpose of this symposium was to present and discuss the results
, of the epidemiological studies, as well as related health topics which
could aid in understanding the findings. The symposium brought to-
gether interested persons from several countries, who contributed freely
and provided an opportunity to summarize the current knowledge in a
single publication.
The proceedings are organized according to the format of the sympos-
ium into six main sections addressing the topics of contaminants, health
fundamentals, population studies, occupational studies, and aerosol
suppression and providing an assessment. In many cases, the proceed-
ings papers are more comprehensive than the symposium presentations
to provide a more thorough coverage of a given topic. Edited discus-
sions are included with the papers, and an attempt was made to identify
each questioner. A list of registrants is presented to allow the reader to
contact any participant for further information.
HERBERT R. PAHREN
WALTER JAKUBOWSKI
Editors
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ABSTRACT
The Health Effects Research Laboratory of the U.S. Environmental
Protection Agency sponsored a Symposium on Wastewater Aerosols
and Disease on September 19-21, 1979, in Cincinnati, Ohio.
This symposium brought together scientists, engineers, physicians,
and public health officials from all over the world to present and discuss
current state-of-knowledge on human health aspects of exposure to mi-
crobiological agents emitted as aerosols from wastewater treatment
plants. Sessions on the nature of the contaminants, health aspects, epi-
demiological studies, and aerosol suppression and a panel discussion
assessing the information were held. The proceedings consist of 22 in-
vited papers and associated discussions.
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VI
ACKNOWLEDGEMENTS
The assistance of the many individuals who contributed to the success
of this symposium and the timely completion of the proceedings is grate-
fully acknowledged. Special appreciation is due to the speakers, for the
quality of their presentations and promptness in submitting their papers,
the session chairmen, and the many participants who contributed to the
discussions.
We also wish to acknowledge the assistance of JACA Corp. and the
EPA Center for Environmental Research Information in providing the
many administrative services in connection with arranging the sympos-
ium and issuing the proceedings. We are also indebted to Lon Winches-
ter for handling the distribution of publications and typing in connection
with the proceedings.
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vii
CONTENTS
Foreword Hi
R. J. Garner
Preface iv
H. R. Pahren, W. Jakubowski
Abstract v
Acknowledgments vi
Keynote Address xi
H. L. Longest
SESSION I: CONTAMINANTS 1
S. A. Schaub, Session Chairman
Methods for Detecting Viable Microbial
Aerosols 1
K. F. Fannin
Indicators and Pathogens in Wastewater
Aerosols and Factors Affecting Survivability 23
C. A. Sorber, B. P. Sagik
Nonviable Contaminants from Wastewater:
Hexachlorocyclopentadiene Contamination
of a Municipal Wastewater Treatment Plant 36
J. R. Kominsky
A Model for Predicting Dispersion of
Microorganisms in Wastewater Aerosols 46
D. E. Camann
SESSION II: HEALTH ASPECTS 71
R. B. Dean, Session Chairman
Infection and Resistance: A Review 71
J. P. Phair
Infection with Minimal Quantities of
Pathogens from Wastewater Aerosols 78
D. O. diver
Responses to Wastewater Exposure
with Reference to Endotoxin 90
R. Rylander, M. Lundholm
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V1H
Health Effects of Nonmicrobiological
Contaminants 99
/. B. Lucas
Epidemiologic Approach to Disease
Assessment 109
R. K. Miday
SESSION III: POPULATION STUDIES 117
S. Poloncsik, Session Chairman
Acute Illness Differences with Regard
to Distance from the Tecumseh, Michigan,
Wastewater Treatment Plant 117
K. F. Fannin, K. W. Cochran,
D. E. Lamphiear, A. S. Monto
Health Effects from Wastewater Aerosols
at a New Activated Sludge Plant: John
Egan Plant, Schaumburg, Illinois 136
D. E. Johnson, D. E. Camann, J. W. Register,
R. J. Prevost, J. B. Tillery, R. E. Thomas,
J. M. Taylor, J. M. Hosenfeld
Wastewater Aerosol and School Attendance
Monitoring at an Advanced Wastewater
Treatment Facility: Durham Plant, Tigard, Oregon 160
D. E. Camann, D. E. Johnson,
H. J. Harding, C. A. Sorber
Health Effects of Aerosols Emitted
from an Activated Sludge Plant 180
R. L. Northrop, B. Carnow, R. Wadden,
S. Rosenberg, A. Neal, L. Scheaff,
J. Holden, S. Meyer, P. Scheff
SESSION IV: OCCUPATIONAL STUDIES 228
J. P. Phair, Session Chairman
Epidemiological Study of Wastewater
Irrigation in Kibbutzim in Israel 228
H. I. Shuval, B. Fattal
Health Effects of Occupational Exposure
to Wastewater 239
C. S. Clark, G. L. Van Meer, C. C. Linnemann,
A. B. Bjornson, P. S. Gartside, G. M. Schiff,
S. E. Trimble, D. Alexander, E. J. Cleary,
J. P. Phair
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Worker Exposure to Organic Chemicals at an
Activated Sludge Wastewater Treatment Plant 265
V. J. Elia, C. S. Clark, V. A. Majeti,
T. Macdonald, N. Richdale
Disease Rates Among Copenhagen Sewer Workers 274
R. B. Dean
Sewage Treatment Plant Workers and Their
Environment: A Health Study 281
L. Sekla, D. Gemmill, J. Manfreda,
M. Lysyk, W. Stackiw, C. Kay,
C. Hopper, L. Van Buckenhout,
G. Eibisch
Interim Report on a Mortality Study
of Former Employees of the Metropolitan
Sanitary District of Greater Chicago 295
P. S. Gartside, B. Specker,
P. E. Harlow, C. S. Clark
SESSION V: AEROSOL SUPPRESSION 302
O. J. Sproul, Session Chairman
Suppression of Aerosols at a
Wastewater Reclamation Plant 302
C. Lue-Hing, J. O. Ledbetter, S. J. Sedita,
B. M. Sawyer, D. R. Zenz, C. W. Boyd
Effectiveness of Aerosol Suppression
by Vegetative Barriers 324
/. C. Spendlove, R. Anderson, S. J. Sedita,
P. O'Brien, B. M. Sawyer, C. Lue-Hing
SESSION VI: ASSESSMENT 339
H. R. Pahren, Session Chairman
Assessment of Health Effects, Panel Discussion 339
L. J. McCabe, C. Lue-Hing,
M. Singal, C. S. Clark
REGISTRATION LIST 355
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KEYNOTE ADDRESS
Henry L. Longest
Deputy Assistant Administrator
Water Program Operations
U.S. Environmental Protection Agency
Washington, D.C. 20460
Waste water Aerosols:
Is The Challenge Only Scientific?
ABSTRACT
This paper discusses the challenges of wastewater aerosols. Are those challenges only
scientific? The author believes the answer to that question is no.
Scientists are responsible for conducting research, obtaining data, interpreting data, and
drawing conclusions based on that data. However, the scientist's role does not end when
results of his or her work are published. On the contrary, the published report becomes an
extension of the scientist when it influences decisionmakers.
Since conclusions in research reports may be used to set policy, the scientist should be
aware of challenges other than the scientific challenge when he conducts research. Those
other challenges are: 1) risks; 2) costs to put the research into effect; and 3) the need to
make explicit recommendations based on research results.
Other challenges of aerosols are particularly important to the Environmental Protection
Agency's Construction Grants program. Decisions made based on results of aerosol stud-
ies could significantly increase costs of projects funded through that program. This empha-
sizes the need for the scientific community to be aware of the implication of their studies
and to recognize all challenges of the aerosol issue.
I am delighted to speak to this particular group since I have seen your
work influence agency policy. I know you will find the information
presented here interesting and useful.
We are going to review research on wastewater aerosols and disease.
Now, why is it important to stand back and take a look at the research
done on aerosols? I believe, basically, there are three major reasons.
First, it is important to be aware of the work of other researchers.
Knowledge of other research approaches, other analytical techniques,
and other research results—all help us better understand the problems
and the issues.
Second, it is important to take a look at this research so future re-
search can be planned. Knowledge of what research has already been
done can help prevent duplication. Then, too, it can help us plan future
research.
And, third—personal contact—meeting the people who conduct the
research. So often, important information does not find its way into a
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xii
report. This information can be shared through contact with the people
who did the research.
Let me start the program by asking a question. Does the scientist face
only a scientific challenge in research on aerosols? I believe the answer
to that question is no.
I have heard some scientists say they are not politicians, administra-
tors, or regulators; they are only concerned with the scientific aspects of
an issue. I do not agree with that statement. Scientists are responsible
for conducting research, obtaining data, interpreting data, and drawing
conclusions based on that data. However, the scientist's role does not
end when the results of his or her work are published. On the contrary,
the published report becomes an extension of the scientist when it influ-
ences decisionmakers.
Often, decisionmakers use the scientist's conclusions as a basis for
setting policy. So the scientist must realize the practical implications of
his work, especially when results are published. This is not to say that
research purely for its own sake is bad. But the scientist should recog-
nize that he does not operate in a vacuum—policymakers may use his
results to set policy that affects everyone, including the scientist him-
self. In those situations, the scientist's role is clearly more than just
scientific.
What are some of the other challenges that scientists face? Let me
illustrate them by talking about research results on wastewater aerosols.
Some research indicates that aerosols may pose a health hazard to
people exposed to them. Other results indicate aerosols do not pose a
health hazard, and still other results are inconclusive. For scientists to
say at this time that we should take all precautions to protect people
from the health hazards of aerosols does not recognize other parts of the
aerosol issue. It does not take into account the acceptable risks from
exposure to aerosols; it does not take into account how much it will cost
to provide protection; and it does not take into account the construction
delays on wastewater treatment plants caused by a lack of agreement on
whether aerosols are a health hazard. The statement recognizes only
that some people exposed to aerosols become sick even though the
cause of the illness may be something besides aerosols. So the other
challenges to scientists are: 1) to consider the risks; 2) to recognize the
costs to put the research results into effect; and 3) the need to make
explicit recommendations based on research results.
Risks are a very important challenge of the wastewater aerosol issue.
If all precautions were taken to protect people from the health hazards
of aerosols, then we would assume that no exposure to aerosols is
acceptable. That would be the ultimate protection and no risks would be
allowed. Do we really need this ultimate protection from wastewater
aerosols?
W. W. Lowrance,* in his book "Of Acceptable Risk: Science and the
Determination of Safety" defines risk as "a measurement of the
probability and severity of harm to human health." He further states,
"This definition emphasizes the relativity and judgmental nature of the
*Lowrance, W. W. 1976. Of Acceptable Risk: Science and the Determination of Safety.
William Kaufman, Inc., Los Altos, California.
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xiii
concept of safety. It also implies that two very different activities are
required for determining how safe things are: measuring risk, an objec-
tive but probabilistic pursuit; and judging the acceptability of that risk
(judging safety), a matter of personal and social values judgment."
The scientist is responsible for measuring the risks. To do that, the
scientist should collect enough data so that he or she can determine
exposure-effect and exposure-response relationships. Without that ex-
posure-effect data those relationships are difficult to assess. And without
those relationships, judging the acceptability of the risk is even more
difficult.
After the scientist measures the risk and determines the exposure-
effect and exposure-response relationships, the policymaker judges
whether this risk is acceptable and sets standards to protect the public.
The scientist's role in setting standards assures that the information on
which these standards are based is sound and not the result of specula-
tion and different opinions. That is very important. It emphasizes the
need for the scientist to be aware of what will be done with the results of
his work. An assessment of risks is an important aspect of any research.
It is especially important in research on wastewater aerosols and other
health-related issues.
Costs to implement the research results are also an important chal-
lenge. As most of you know, I am the National Program Manager of
EPA's Construction Grants program. We give communitfes grants to
help them build new wastewater facilities and to upgrade old wastewater
facilities. So I am acutely aware of the impact of costs on the construc-
tion of wastewater facilities. Let me illustrate with an example that
relates to the aerosol issue.
The North Shore Sanitary District received a grant from EPA to up-
grade the Clavey Road Wastewater Treatment Plant in Highland Park,
Illinois, and to expand the capacity of that plant from about 4*/2 mgd
to about 18 mgd. During that time it took to plan, design, and construct
the Clavey Road plant, areas adjacent to the plant developed. Residents
who lived near the plant became concerned about the potential odor
problem and the potential health hazards of aerosols from the treatment
plant. They sued to make the North Shore Sanitary District do some-
thing about those potential problems.
As a result of litigation, the Sanitary District installed odor control
equipment and covered all the treatment plant units, including six large
retention basins. It cost over $8V2 million to cover those units. That was
about 24% of the total capital costs for upgrading and expanding the
entire treatment plant.
This illustrates the enormous cost to protect people from the potential
hazards of aerosols. Those costs are even more staggering when you
consider that not all researchers and health authorities agree there are
any health hazards from exposure to wastewater aerosols.
EPA's 1978 Needs Survey says there will be about 23,000 wastewater
treatment plants in the United States by the year 2000. Of these plants,
285 will have a flow rate between 10 mgd and 50 mgd. The cost impact on
EPA's Construction Grants program just to cover that slightly more
than \% of the total number of treatment plants for aerosol protection
would be severe. That impact would also be felt by the communities that
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XIV
have to pay both the local share of an EPA-funded project and the
operation and maintenance costs of that project. So—to repeat—the
scientist must be aware that his research results do have a cost impact
when they are used to set policy.
The last challenge I want to talk about concerns the recommendations
a scientist makes based on the results of his research.
When I was the Water Division Director at EPA's Region V office in
Chicago, we initiated the O'Hare Aerosol Suppression Study. That
study was in response to a proposal that aerosol suppression equipment
be installed at the O'Hare wastewater treatment plant because of the
health hazard posed by the aerosols. Before we approved that proposal,
we required that the aerosol issue be studied.
Phase 1 of that study is nearly complete. We are collecting back-
ground samples of the ambient air around the O'Hare plant and analyz-
ing them for bacteria. When the plant begins operation, we will collect
more samples and analyze them for bacteria. Results of the two sam-
pling programs will be compared to see whether the aerosol suppression
equipment is justified. They will also be compared with findings of other
research.
The approach taken at the O'Hare plant is a good one. It insists that
the hazard be verified before we spend a lot of money for control equip-
ment. But it also requires that the scientists who conduct the sampling
study make scientific recommendations based on the results of the
study. The challenge for the scientist is to make explicit recommenda-
tions and to support those recommendations at all times.
That challenge applies to all researchers and not just those involved in
the O'Hare study. For example, EPA is involved in an issue of what
concentration of cadmium should we allow in sludges applied to the
land. Some research reports indicate that the concentration should be a
certain value. Researchers who prepared those reports indicate, when
you talk to them, that a different value may be acceptable. This "con-
flict" is a major problem. Some researchers in this situation did not
make explicit recommendations that they could continue to support
without expansion or clarification when questioned. This leads to con-
flicting statements regarding published reports and possibly conclusions
not supported by actual data.
As you listen to the speakers at this symposium, I hope you will
remember the question I asked at the beginning of my talk: Is the chal-
lenge of wastewater aerosols only scientific? I hope you will ask the
question when you go back to your offices and plan future research on
aerosols. I also hope you will keep in mind the challenges I have dis-
cussed. Beside the scientific challenges, remember the other challenges
—risk factors, cost impacts, and explicit recommendations. Decisions
will be made—you should participate!
DISCUSSION
SPEAKER: I like to think of myself as a very pragmatic scientist. I
am also a professional school teacher. I have taught my students that we
scientists are to cooperate with each other, to be interdependent, and to
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XV
share our knowledge. Then when I met the world of reality; I found out
that wasn't the case. I am ashamed of our groups of scientists. Each one
seems to have his own little empire, and we don't seem to be able to get
together anymore. Perhaps it is just the trend of the nation.
MR. LONGEST: What I tried to do here was to stimulate you and
challenge you. I recognize the pressure the scientist is under when put-
ting his or her name to a document that goes out and may be used in a
court case.
The point that I am trying to get across is that I feel very strongly that
the scientist cannot just walk away and say, "Well there are my scien-
tific conclusions." I do recognize the position that the scientists are in.
But decisions are being made daily, whether the data are good or not.
The better you can help us in terms of explicit recommendations based
on the best information you have, recognizing that you may not find that
information completely to your satisfaction, the better our output will
be. You might be amazed at how many decisions are made on informa-
tion that is much less complete than what you are providing. You are
part of the decisionmaking process; I encourage you to remain a part of
the process and recognize that these decisions are going to be made.
DR. SPENDLOVE: As scientists, we are required to characterize
the aerosols. I think the crux of the whole situation is the risk question. I
would like to ask if you would give us a little more information on risk,
and what you are willing to define in terms of risk. I would like to hear a
little bit more of what your definition of risk means.
MR. LONGEST: I am certainly not going to answer that loaded
question, but I will talk around it for a minute. I think the key thing is
that many times the aerosol issue is used instead of another reason. I
won't name the specifics, but I know of several facilities where there is
no doubt in my mind that the aerosol risk is not the issue. The issue is,
"I don't want a sewage treatment plant in my backyard.''
So what I am trying to say is let's first determine if there is a risk for
the treatment plant neighbors. If so, let's say what that risk is, relative to
the risk of the operators working in the sewage treatment plant. That
must be considered. Then we should determine if that risk is the same as
or different than that for the person who lives 1,000 yards from the
sewage treatment plant.
Without giving some types of explicit recommendations, I am not
talking in terms of life lost but specifically about the proven chances of
someone getting ill from living near a sewage treatment plant, comparing
that chance with the cost, and then finding out if there really is a health
issue in that particular situation, or whether it is just an excuse to stop
treatment plant construction in somebody's backyard.
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Methods For Detecting Viable Microbial Aerosols
KerbyF.Fannin*
Life Sciences Research Division
IIT Research Institute
Chicago, Illinois
ABSTRACT
Aerosols formed during processes of wastewater treatment can contain viable microorgan-
isms that survive transport to distant locations from the site of origin. Detection of such
viable microbial aerosols under field conditions requires the application of reliable metho-
dologies capable of attaining acceptable sensitivity levels. These acceptable levels should
be determined before initiation of sampling activities. Determination of low-level concen-
trations of viable microbial aerosols in the ambient environment requires sampling at
relatively high air flow rates for long time periods.
Aerosol collection concepts such as sedimentation, filtration, impingement, precipita-
tion, centrifugal separation, or inertial impaction may be employed, provided the sampling
devices can be sterilized and can maintain the viability of collected organisms without
permitting growth. Widely used samplers such as all-glass impingers and multistaged
impactors are suitable for detecting high microbial aerosol concentrations but, due to their
relatively low sampling rates, may not be applicable when very low microbial aerosol
levels are anticipated. For applications requiring greater air sampling sensitivity, devices
with higher air sampling rates have been developed. These "large volume air samplers"
include inertial impactors, electrostatic precipitators, and centrifugal separators, each
with unique advantages and disadvantages. Among the criteria that should be considered
in viable microbial aerosol sampler selection are: collection efficiency, sampling sensitiv-
ity, reliability, ease of sterilization, maintenance of collected sample viability, ease of
sample assay, remote operation capability, particle size discrimination, and cost.
Studies with appropriate sampling devices require implementation of a vigorous quality
assurance program in both the field and analytical laboratory. Meaningful data interpreta-
tion may require consideration of basic meteorological parameters as well as the limita-
tions of the methodologies employed.
*Present address:
Institute of Gas Technology
IIT Center
Chicago, Illinois 60616
Domestic sewage can be a source of potentially pathogenic bacteria,
viruses, parasites, and fungi that may initiate infections in susceptible
hosts upon exposure (1,2). Such exposure may occur through direct
sewage contact; contact with contaminated fomites; ingestion of con-
taminated water or food; or inhalation, ingestion, or contact with mi-
croorganism-containing sewage aerosols. The occurrence of microor-
ganisms in sewage aerosols has been demonstrated, and the reports of
many of these investigations have been reviewed (3). Existing studies
have focused upon evaluation of the aerosols emitted by such wastewa-
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2 Wastewater Aerosols and Disease/Contaminants
ter treatment processes as activated sludge, trickling nitration, and land
application by spray irrigation. Inherent characteristics of each treat-
ment process determine the method of aerosol generation.
The process of activated sludge treatment, for example, generates
small bubbles by diffused air aeration that rise through the sewage depth
in the aeration tank to the surface boundary. The formation of sewage
aerosols during aerobic wastewater treatment and their emission as
mists or droplets have been demonstrated (4). Rising bubbles can adsorb
and concentrate suspended bacteria and viruses while moving toward a
liquid surface (5,6). At the surface boundary, a film containing microor-
ganisms is disrupted by the rising bubbles which burst, releasing tiny
aerosol droplets containing the bubble-adsorbed, as well as the surface
film-associated, microorganisms. The characteristics of aerosols gener-
ated by processes of spray irrigation are affected by machinery design as
well as by prevailing meteorological conditions (7). Spray irrigation
equipment produces large quantities of respirable aerosols whose num-
ber increases as a function of windspeed and length of time exposed to
the wind. (8). During treatment by trickling filtration, impacting sewage
onto rocks within the trickling filter unit causes a splashing effect, result-
ing in sewage aerosol formation (9). The nearly instantaneous evapora-
tion which may occur as these droplets become suspended in air leaves a
dried residue referred to as a droplet nucleus (10), subject to downwind
dispersion dependent on its size, density, and on prevailing meteorologi-
cal conditions. The net effect of sewage-borne aerosol formation is that
procedures of water pollution abatement become potential contributors
to air pollution problems that should be assessed in terms of exposure
risks and effects on human health.
The purpose of this presentation is to review and present some con-
cepts behind the design and implementation of field studies for ambient
viable microbial aerosol detection from facilities such as wastewater
treatment operations.
FIELD STUDY INITIATION
Approach
Field studies of microbial aerosols, initiated as specific research in-
vestigations or as monitoring programs intending to answer questions
with health, political, economic, or regulatory implications, are depend-
ent upon the clarity of proposed objectives for their ultimate success.
These objectives are the basis of study site selection, experimental de-
sign, methods selection, and monitoring strategies. The study site selec-
tion is also dependent upon factors such as physical accessibility, coop-
eration of local governmental officials, and density and location of a
potentially exposed population. Since the study objectives may require
aerosol concentration discrimination on the basis of time, location, sea-
son, particle size, or atmospheric stability, an experimental design may
require utilization of several sampling instruments at numerous loca-
tions at specified time intervals. Determination of both sampling fre-
quency and number of sampling locations should be made in an effort to
obtain statistically reliable data. A compromise between either sampling
frequency or number of sampling locations may, however, be required
when resource limitations are a factor.
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KerbyF. Fannin 3
Sampling Sensitivity
Guidelines regarding required microbial aerosol detection sensitivities
have not been defined. As a result, air sampling volumes collected dur-
ing specific field studies are often based upon the constraints of existing
sampling methodologies and may be below the sensitivities required for
detection of low-level aerosols. The significance of nonpositive observa-
tions is dependent upon the proportion of the total air volume being
sampled, which is very small in open air, and upon the efficiency of the
collection and assay systems. With this in mind, negative observations
must be interpreted in view of the detection sensitivities attained. Prior
to initiating a field sampling program, the investigator should determine
a level of acceptable sampling sensitivity at which negative observations
will be interpreted as inconsequential.
A level of acceptable risk of exposure, and resultant sampling sensi-
tivity, to microbial aerosols has not yet been determined but may be
based upon either individual or population exposure. That is, either the
exposure of an individual over a limited time period (11) or that of a
susceptible population of a certain size and density may be emphasized
in such risk determinations. With the latter approach, introduction of an
infection into a population via droplet nuclei and subsequent transmis-
sion by effective contact between susceptible and infected individuals
should be considered (12).
VIABLE MICROBIAL AIR SAMPLING INSTRUMENTATION
Description of Representative Samplers
Background
While health effects can be assessed by epidemiological methods,
determination of risks of exposure requires the application of reliable
methodologies capable of detecting airborne microbial contaminants at
acceptable sensitivity levels. Sample collection from open air is compli-
cated by a high dilution factor for dispersed particulates. Consequently,
attaining the sensitivity required for detecting source-related infectious
microbial aerosols at the threshold of acceptable risk may require sam-
pling at relatively high air flow rates for long time periods. Extensive
instrumentation, based on widely varying concepts, has been developed
for detecting viable microbial aerosols. Each device has unique charac-
teristics which often result in differences in collection efficiencies for
aerosols in certain size ranges, sampling capacities, and operational cap-
abilities that make comparisons of data collected with different samplers
or under differing conditions very difficult. Although an attempt was
made to recognize certain low-volume samplers as standards for studies
in aerobiology (13), the need for samplers of greater sensitivity for field
studies has resulted in the development of nonstandard large volume air
samplers based upon different collection concepts. The principle aerosol
collection concepts which have been used in aerobiology are sedimenta-
tion, filtration, impingement, impaction, and cyclone scrubbing. Typical
examples of the application of each concept for viable microbial aerosol
collection are presented in Table 1.
-------
Wastewater Aerosols and Disease/Contaminants
Type of sampler
Sedimentation
Open petri dish
Collection
Medium
Agar surface
Air sampling
capacity
Low
Comment
Simple, inexpensive, non-quantitative,
Filtration-
Membrane filter
Electrostatic
Precipitation-
Litton Model M
LEAP
Centrifugal separation.
Cyclone scrubber
Impingement'
All-glass impinger
Multistage impinger
Membrane
Compatible fluid
Compatible fluid
Compatible fluid
Compatible fluid
Multislit impinger Compatible fluid
Impaction
Slit sampler
Multistage impactor
Agar surface
Agar surface
favor particles with high settling
velocity
Low Simple, relatively inexpensive, viability
losses due to desiccation of fragile
organisms
High Complex, expensive, electrical arcing
sterilization difficult, efficient
High Simple, relatively inexpensive, opera-
tion subject to relative humidity vari-
ations, autoclavable
Low Simple, inexpensive, dependable
Low Simple, relatively inexpensive, size
classification
High Complex, expensive, undependable,
sterilization difficult, efficient for large
particles
Low Simple, particle time discrimination
Low Simple, relatively expensive, particle
size discrimination, dependable
Table 1. Selected Viable Microbial Aerosol Sampling Concepts and
Instruments
Sedimentation
Settling plates (Figure 1) offer a simple and inexpensive method of
microbial aerosol collection. The aerosol particles are permitted to settle
on a nutritional agar-based medium contained within petri dishes. Fol-
lowing incubation, colonies are counted and the general level of contam-
ination for a defined time period is assessed. This procedure, used for
both intramural and extramural aerosol sampling (14,15), has been sug-
gested as a standard method for detection of bacteria in ambient air (16).
Although this method determines the number of viable particles which
adhere to the exposed plate, their impaction onto the agar surface de-
pends upon the air flow velocity and angle as well as the particle size and
density (17). Large particles of greater density have a higher settling
velocity than smaller particles of lower density (18) and are, conse-
quently, collected more efficiently. Since smaller particles are more
likely to achieve deep lung penetration than are larger ones (19), the
value of microbial aerosol collection by sedimentation in the assessment
of the risk of respiratory infection is limited by its failure to detect more
minute aerosols.
Filtration
Filtration (Figure 2) offers another simple and relatively inexpensive
commercially available means of efficient removal of microorganisms
-------
KerfoyF. Fannin
Figure 1. Nutrient Agar-Filled Settling Plate with Collected Microorgan-
isms
Figure 2. Membrane Filter Aerosol Sampler
-------
6 Wastewater Aerosols and Disease/Contaminants
from an airstream. The applicability of filtration devices such as cotton
(20), soluble gelatin (21), or membrane filters (22) as viable microbial
aerosol samplers is determined by characteristics of the study organ-
isms. Stable microorganisms such as Bacillus subtilus var. niger spores,
for example, can be efficiently recovered by filtration (23) while the
recovery of viable vegetative Serratia marcescens has been shown to be
as low as 0.1% to 2% under certain conditions (24). Viability losses due
to desiccation of fragile organisms makes use of filter samplers impracti-
cal for long-term or large-volume sampling applications.
Impingement
As used in this presentation, impingement refers to striking into rather
than onto a collection medium. Liquid impinger samplers are used to
determine the number of viable microorganisms in aerosols, rather than
the number of viable aerosol particles (25). The all-glass impinger (AGI)
(Figure 3) is a simple, inexpensive, easily sterilized device (26) designed
for isokinetic sampling of dynamic aerosols (27) at 0.0125 m3/min by
high speed impingement into a collecting medium. The AGI-30 (having a
jet-to-base distance of 30 mm) was recommended as a standard sampler
by a committee of aerobiologists (13). To minimize microorganism re-
atomization (28) and vegetative cell destruction (29) during the high
speed impingement process, low speed bubbling and washing samplers
such as the midget impinger, fritted bubbler (27), and tangential impin-
gers (25,30) were developed. A preimpinger (31), for use with the AGI,
and a multistaged liquid impinger (26) have been used for aerosol size
discrimination.
Impinger sampling fluid is under low pressure and tends to evaporate
quickly and freeze in cool dry air (32). Changes in fluid pH, volume, and
osmotic pressure can occur during liquid impingement necessitating
sampling time restrictions (33). Relatively low air sampling rates and
short permissible sampling durations limit the sensitivity of impinger
samplers. To increase impinger sampling capacity and, hence, sensitiv-
ity, multiple devices were run in parallel (34), multiple jet impingers
used (35), a continuous impinger constructed (36), and a large volume
multi-slit impinger (MSI) developed (37).
The MSI, which collects aerosol particles at an air sampling rate of
about 1 m3/min by inertial impaction into a liquid film-coated rotating
disc, has been used in field studies of wastewater-generated microbial
aerosols (38). Although the MSI collection efficiency, compared to an
AGI-30, was reported to be 82% for S. marcescens and 78% for B.
subtilus var. niger spores (37), ". . .reliability, maintainability and porta-
bility were considered to be of less importance. . ."in the MSI design
than demonstrating the theory of operation (39). In addition to difficul-
ties in field dependability (38), the MSI does not lend itself to conven-
tional sterilization procedures prior to sample collection.
Electrostatic precipitation
Microbial aerosols carrying a charge can be collected with relatively
high efficiency by drawing them over an oppositely charged agar surface
(40,41,42,43). The concept of aerosol collection by electrostatic precipi-
tation onto a wetted surface has been employed in the development of
-------
Kerby F. Fannin 1
large volume air samplers with air sampling rate capacities ranging from
about 1 to 10 m3/min. Both the Litton Model M (LVAS) (44) (Figure 4)
and the Environmental Research Corporation LEAP (45) electrostatic
Figure 3. All-Glass (mpinger-30
-------
Wastewater Aerosols and Disease/Contaminants
Figure 4. Litton Large Volume Air Sampler
-------
KerbyF. Fannin 9
precipitator large volume air samplers have been used in field studies of
wastewater-generated microbial aerosols (38,46).
A comparative evaluation of the MSI and the LVAS showed that their
percent efficiencies, based upon the AGI-30, were affected by the organ-
isms studied. For S. marcescens, for example, the LVAS has a 95%
efficiency rating compared to 90% for the MSI. Conversely, with B.
subtilus var. nlger, the LVAS was 74% and the MSI was 86% as efficient
as the AGI-30 (44). Other studies have shown electrostatic precipitation
to be less effective than liquid impingement for detecting viable airborne
viruses (43,47). Such observations have been attributed to electrostatic
precipitator-generated ozone (43), or to rapid evaporation of polar liq-
uids, enhanced by electric current, or by a critical concentration of
unipolar air ions (48).
The LVAS has been found to be effective for bacterial, viral and
rickettsial aerosols when conventional sampling was not suitable, as
with very dilute concentrations, and is most effective in still air when
operated in a level position, constantly monitored by a trained techni-
cian, and not subjected to electric current fluctuations (49). In addition
to being difficult to sterilize by conventional methods, problems with
sampling fluid evaporation and quantitation exist with the large volume
air samplers (50).
Cyclone scrubbing
The viable microbial aerosol cyclone scrubber samplers (Figure 5)
collect airborne particles by tangential impingement into a continuous
fine fluid film created as a mist is impacted into the sampler wall. The
fluid film travels spirally to a reservoir where it is collected by slight
suction. Such devices, constructed of glass, plastic, or stainless steel,
have air sampling rates up to about 0.95 m3/min and fluid flow rates from
1 to 4 ml/min (23,44,51,52). The scrubbing liquid, supplied either by
peristaltic or screw-driven syringe pumps, is subject to water loss due to
evaporation which may require replacement.
Available data (Figure 6) demonstrate that cyclone scrubber efficien-
cies are variable and dependent upon aerosol particle size, specific test
organism, and collection fluid (52). Average efficiencies (AGI-30 refer-
ence) are reported to be 63% to 133% for B. subtilus var. niger, depend-
ing upon sampler configuration, particle size, and collecting fluid. Vege-
tative bacteria are more sensitive to collecting fluid composition
variations than are bacterial spores. While 0.06% Tween 80 solution
enabled relatively high recovery efficiencies for B. subtilus var. niger
spores (23), for example, it was found to be toxic to the S. marcescens
and Escherichia coli collected in a reference AGI-30 (52). Cyclone
scrubber samplers lend themselves to sterilization by conventional proc-
esses and have been used in field studies for recovery of wastewater-
generated viral aerosols (53). In the field, cyclone scrubbers are rela-
tively easy to operate, compared to other existing large volume air sam-
plers, but may require continual monitoring and fluid adjustments during
sample collection.
-------
10 Wastewater Aerosols and Disease/Contaminants
Figure 5. Glass Cyclone Scrubber Sampler
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12
Wastewater Aerosols and Disease/Contaminants
Impaction
After acceleration to sufficient inertia to leave an airstream, aerosol
particles can be impacted onto a collecting medium surface. This con-
cept is used for simultaneous sampling and size analyses with the cas-
cade impacter (54). This device, consisting of a series of four jets and
slides, accelerates the aerosol with progressively smaller jets, permitting
collection of progressively finer particles. Subsequent modifications of
the cascade impactor have been used for collecting and sizing both
bacterial and viral aerosols (55,56) (Figure 7). Acceleration through slits
or jets of critical size and distance from the impaction surface is widely
used for collection of microbial aerosols onto agar media. Examples of
such devices include slit (Figure 8) and multistaged impactors (Figure 9).
The most common forms of both instruments sample at a rate of about
Figure 7. Modified Cascade Impactor
-------
Kerby F. Fannin
13
Figure 8. Slit Sampler
0.028 m3/min. With the slit sampler, airborne particles are collected onto
a slowly rotating agar surface for time discrimination of microbial aero-
sol concentrations (57,58) while the multistaged impactor, such as that
developed by Andersen (59), permits aerodynamic particle sizing by
impaction onto the surface of^staged agar-containing plates at increasing
velocities. Wide acceptance of this multistaged impactor led to its rec-
ommendation as a standard sampler for collection of airborne microor-
ganism-containing particles (13).
The sampling capacity of both the slit sampler and multistaged impac-
tor is limited by their relatively low air sampling rates and by observa-
tions of decreased collected organism viability during prolonged sam-
pling periods (60,61). The sampling period in both samplers can be
extended without affecting the viability of collected organisms by apply-
ing an evaporation retardant to the agar surface (62). To further increase
the air sampling capacity of agar impactors, larger volume instruments
-------
14
Wastewater Aerosols and Disease/Contaminants
STAGE NO
JET SIZE
JET VELOCITY
STAGE 1
0 0465" DIA
3 54 FT/SEC
STAGE 2
0 0360" DIA
5 89 FT/SEC
STAGE 3
00280" DIA
9 74 FT/SEC
STAGE 4
0 0210" DIA
17 31 FT/SEC
STAGE 5
00135" DIA
41 92 FT/SEC
STAGE 6
0 0100" DIA
76 40 FT/SEC
Figure 9. Andersen Multistaged Impactor Sampler
have been developed. The Cassella multi-slit impactor, designed for
sampling up to 0.7 m3/min and the Pagoda multistaged impactor, re-
ported capable of sampling particles into distinct size ranges at rates up
to 1 m3/min, were described by May (63).
Modifications of agar impactor samplers for field sampling have
stressed the importance of inlet design and alignment relative to the
wind. Inlet removal, redesign of the jet pattern, addition of another
stage, and horizontal alignment of the multistaged impactor have, for
example, been recommended (64). A slit sampler designed to sample
-------
KerbyF. Fannin 15
horizontally into the wind with tolerable deviation from isokinetic sam-
pling at windspeeds up to 10 m/sec with an air sampling rate of 0.02 m3/
min was described (61). A major disadvantage of these field-modified
samplers is that they still lack the sensitivity required for very dilute
microbial aerosol concentrations. A major limitation of agar impactor
samplers in general is that they are best suited for enumeration of mi-
croorganism-containing particles rather than for total bacteria or vi-
ruses, for which a liquid medium would be better suited.
Sampler Selection
Depending upon the objectives of the particular study, several types
of samplers may be required for simultaneous sampling. If, for example,
high sensitivity as well as particle size and time discrimination are re-
quired, such devices as large volume air samplers, multistaged impac-
tors, and slit samplers may be employed. In practice, each sampler has
unique advantages and disadvantages which should be considered prior
to sampler selection or data interpretation. Prior to selecting specific
sampling methodologies, consideration should be given to criteria such
as: (1) collection efficiency; (2) sampling sensitivity; (3) reliability; (4)
ease of sterilization; (5) maintenance of collected sample viability; (6)
ease of sample assay; (7) ease of operation; (8) remote operation capa-
bility; (9) particle size discrimination; and (10) cost. Using these criteria,
a sampler can be evaluated to determine its applicability for a specific
field study.
Conventional aerobiological sampler evaluations, performed by rela-
tive rather than absolute methods, determine microbial aerosol collec-
tion efficiencies as a percentage of that observed in a reference sampler.
The sensitivity of a particular sampler is directly related to its collection
efficiency and to other operational parameters. The sensitivity of var-
ious samplers under specified conditions can be compared by determin-
ing a value which could be referred to as a coefficient of sensitivity
defined as:
~c CE x R x D
Co =
V
where:
CS = coefficient of sensitivity
CE = collection efficiency (% of reference sampler)
R = air sampling rate (m3/min)
D = sampling duration capability (min)
V = final volume of collection medium (ml).
The CS value increases with collection efficiency, air sampling rate,
sampling duration capability, and with reductions in the final collection
fluid volume required for assay. One way to reduce this final collection
fluid volume is recirculation during the sampling process. Depending
upon the organisms collected, however, such a practice could result in
some viability losses which would, in turn, reduce the estimated viable
microorganism collection efficiency.
-------
16 Wastewater Aerosols and Disease/Contaminants
The reliability, ease of sterilization, ease of operation, and remote
operation capacity vary substantially among existing viable microbial
aerosol samplers. Sampler reliability, which is related to the dependabil-
ity and robustness of individual components, is of critical importance in
the field when replacement parts and repair services are not available.
Samplers designed with heat-sensitive components integrally associated
with aerosol collection or sample moving systems do not lend them-
selves to sterilization by conventional steam autoclaving procedures and
may require the selection and evaluation of other means of sterilization.
Independent sampler operation during field studies requires varying de-
grees of operator training. Such devices as slit samplers, for example,
are relatively simple to operate compared to electrostatic precipitator
large volume air samplers and, consequently, require substantially less
intensive personnel training prior to field use. Although, in practice,
most viable microbial samplers require some attention in the field, those
with greater remote operation capacity offer more versatility for field
use than those which require constant attention.
The kind of sampler chosen depends upon the study objectives and
the assay procedures. If, for example, an objective is to assess risks of
respiratory infections, then a sampler classifying the microbial aerosol
according to particle size should be employed. Although agar-based
samples are easy to assay for certain kinds of bacteria or fungi, samplers
employing a liquid collecting medium permit versatility by enabling both
sample dilutions and greater assay technique versatility. Bacteria and
viruses, for example, may be assayed from the same liquid medium
sample. During sample collection, transport, and assay, an environment
compatible with the survival of specific kinds of organisms should be
employed. Generally, this requires continuous hydration of the organ-
isms in a collection medium at a temperature compatible with organism
survival, but not growth.
The cost of viable microbial aerosol samplers varies substantially.
Glass impinger samplers are, for example, inexpensive while the cost of
certain large volume electrostatic precipitators is relatively high. When
resource limitations are a factor, relative costs must be considered in the
sampler selection process.
FIELD STUDY IMPLEMENTATION
Field Sampling
All sample and data analyses, interpretations, and conclusions are
dependent upon the reliability and validity of the sample collection proc-
ess. If the sampling process is questionable, then subsequent analyses
and inferences may be meaningless. Collection of an accurate and repre-
sentative air sample can be a very complicated task requiring participat-
ing personnel who are both versatile and dedicated, having some me-
chanical aptitude as well as basic training in applied microbiology and air
sampling methods.
Along with the problems of selecting instrumentation and personnel,
the procedures employed in the field must be carefully planned. If re-
sources are limited, a smaller number of sensitive samples may be of
greater value to project objectives than a large number of insensitive
-------
Kerby F. Fannin 17
samples. The representativeness of a particular sample will be affected
by air sampling velocities, sampler inlet orientation, and windspeed and
direction fluctuations. Under normal ambient conditions, isokinetic
sampling is very difficult and impractical to achieve (54). In addition to
sample collection difficulties, other logistical problems such as electrical
supply requirements, frequent sampler breakdowns in the field, main-
taining sampler sterility, field communication, transportation of sam-
pling equipment at the field site, and transport of collected samples to
the laboratory for assay have been noted (11) and must be considered.
Sample handling during the sampling process and transport to the labo-
ratory for assay must be done to minimize the possibility of contamina-
tion and microbial die-off or growth.
Sample Assay and Enumeration
When available, standard procedures should be employed for the as-
say of specific microbiological parameters (65,66). Precise methods for
sample analyses are affected by sampling fluid composition and required
detection sensitivities. Samples collected on an agar-based medium, for
example, may only require incubation prior to enumeration whereas
those collected in a liquid medium may, depending on the test organism,
require simple dilution and plating, filtration, or elaborate processing
procedures prior to assay.
Microbial aerosol concentrations are expressed as detectable assay
units/m3 of air. Enumeration can be based upon direct counts or multi-
ple tube dilution methods, such as the most probable number (mpn)
procedures, for estimation of the number of detectable assay units per
sample volume. Application of multiple tube dilution procedures has
been shown, in some instances, to be more sensitive than direct enumer-
ation methods for detecting certain microorganisms (67). Selection of
specific enumeration procedures, however, may be based upon specific
project objectives, assay methods, and sensitivity requirements.
Microbial aerosol concentrations from fluid medium samplers can be
determined by:
^ N V
A R x D
where:
C = concentration of detectable microbial units/m3 air (e.g., cfu/m3)
N = number of detectable microbial units (e.g., cfu, mpn pfu)
A = portion of sample assayed (ml)
V = final volume of collection fluid (ml)
R = air sampling rate (m3/min)
D = sampling duration (min).
For agar-based medium samplers, A and V may be omitted unless only a
portion of the total sample is to be counted. In such a case, the volume
of air/cm2 agar surface are would be used in concentration calculations.
If the sampler collection efficiency is known, then the C value should be
appropriately corrected.
-------
18 Waste water Aerosols and Disease/Contaminants
Quality Assurance
Methods for detecting viable microbial aerosols are not yet standard-
ized. Consequently, there may be considerable variation between the
results among investigators using different sampling or assay proce-
dures. The efficiency of viable microbial air samplers depends upon a
number of operational parameters, including air sampling and fluid flow
rates, wind velocity and direction fluctuations, aerosol particle size and
density variations, as well as the overall efficiency of the sampler itself.
The efficiency of specific samplers may be determined relative to a
reference sampler under experimental conditions for aerosols having
known characteristics. Such determinations, however, are relative and
not absolute. Under varying conditions, such as those encountered in
the field, true sampling efficiencies cannot easily be ascertained.
Prior to use and periodically throughout the project, each sampler
should be calibrated to determine air flow rates using a precalibrated
mass flow meter or anemometer. All samplers should be numbered and
each collected sample identified with a particular instrument. Controls
for verification of field sampler sterility and laboratory assay procedures
should be employed where appropriate. In addition to quality assurance
procedures required for the specific project, recommended laboratory
and assay procedures (65. 66) should be adhered to where applicable.
Data Analyses and Interpretation
Data from a field study of microbial aerosol concentrations may be
collected under a wide range of meteorological conditions, each having
effects on microbial survival, dispersion of heterogeneously-sized aero-
sols, and aerosol sampling efficiencies that may be either known or
unknown to the investigator. The validity of statistical analyses of such
data requires that basic underlying assumptions, such as homoscedastic-
ity and normality of the test populations, be met. If such assumptions
can neither be verified nor assumed because of uncontrolled field study
variables, then alternatives to conventional parametric analysis should
be considered. Data interpretation must take into account the limitations
of the methodologies employed to obtain the information.
ACKNOWLEDGEMENT
This work was supported by U.S. Environmental Protection Agency
Grant No. R805864-01. The thoughtful discussions of Stanley Vana are
gratefully acknowledged.
References
1. Akin, E. W.. W. Jakubowski, J. B. Lucas, and H. R. Pahren. 1978. Health hazards
associated with wastewater effluents and sludge; microbiological considerations In
Proceedings of the Conference on Risk Assessment and Health Effects of Land Appli-
cation of Municipal Wastewater and Sludges. B. P Sagik and C. A. Sorber. eds The
University of Texas at San Antonio.
2. Wang, W. L. L., and S. G. Dunlop. 1954. Animal parasites in sewage and irrigation
water. Sew. Ind Waste. 26:1020-1032.
3. Hicke). J. L. S., and P. C. Heist. 1975. Health significance of airborne microorganisms
from wastewater treatment processes. Part 1. Summary of investigations. Jour Water
Poll. Control Fed.. 47:2741 -2751
-------
Kerby F. Fannin 19
4. Woodcock, A. H. 195?. Bursting bubbles and air pollution. Sew. Ind. Waste. 27:1189-
1192.
5. Blanchard, D. C., and L. Syzdek. 1970. Mechanism for the water-to-air transfer and
concentration of bacteria. Science. 170:626-628.
6. Baylor, E. R., V. Peters, and M. B. Baylor. 1977. Water-to-air transfer of \irus
Science. 197:763-764.
7 Hennessey, J., G. Raynor, and M. Small. 1975 An Evaluation of Spray Distribution b>
Land Irrigation Machmer> Utilized for Land Disposal of Waste water. Brookhaven
National Laboratories to LT.S Arm> Medical Research and Development Command.
Washington. D.C
8 Raynor, G. S., and J. V. Hayes. 1976. Aerosol production by irrigation equipment used
for land application of wastewater Am. Inditst. Hygiene Assoc. Jour.. Sept.:526-536
9. Adams, A. P., and J. C. Spendlove. 1970 Coliform aerosols emitted by sewage treat-
ment plants. Science. 169:1218-1220.
10. Riley, R. L. 1974 Airborne infection. Am. Jour. Med.. 57:466-475.
11 Schaub, S. A., J. P. Glennon, and H. T. Bausum. 1978 Monitoring of microbiological
aerosols of wastewater sprinkler irrigation sites. In' Proceedings of an International
Symposium on Land Treatment of Wastewater. U.S Army Cold Regions Research
and Engineering Laboratory. Hanover. New Hampshire.
12 Riley, R. L., and F. O'Grad>. 1961 Airborne Infection The MacMilhan Compan>.
New York.
13. Brachman, P. S., R. Ehrlich, H. F. Eicbenwald, V. J. Cabelli, T. W. Kethley, S. H.
Madin, J. R. Malt man. G. Middlebrook, J. D. Morton, I. H. Silver, and E. K. Wolf.
1964 Standard sampler for the assa> of airborne microorganisms Science. 144:1295
14 Gould, J. C. 1970. Airborne pathogenic bacteria in a tissue transplant unit In. Aero-
biology • Proc. Third Internal. S>mp.. I H. Silver, ed. Academic Press. London.
15 Baylor, E. R., M. B. Baylor, D. C. Blanchard, L. D. Syzdek, and C. Appel. 1977 Virus
transfer from surf to wind. Science. 198:575-580.
16. Fischer, G., S. Forde, and M. Nehez. 1972. Contribution to the standardization of
bacteria counts in ambient air by means of microbiological sedimentation studies Z.
GesamteHyg. Ihre Grenigehiete. 18:267-273.
17. Sykes, G. 1970. The control of contamination in sterile areas. In: Aerobiology: Proc.
Third Internal. Symp.. I. H. Silver, ed. Academic Press. London
18. Dinunick, R. L. 1969 Mechanics of aerosols. In: An Introduction to Experimental
Aerobiology. R. L. Dimmickand A. B Akers. eds Wiley-Interscience. New York
19. Hatch, T. F. 1961. Distribution and deposition of inhaled particles in respiratory tract.
Bacterial. Rev.. 25:237-240.
20. Woll, H. W., P. Skaliy, L. B. Hall., M. M. Harris, H. M. Decker, L. M. Buchanan, and
C. M. Dahlgren. 1959 Sampling Microbial Aerosols. Publ. Health Mono No. 60
(Publ. No. 686). U.S. Govt. Printing Office.
21. Noller, E., and J. C. Spendlove. 1956. An appraisal of the soluble geletm foam filter as
a sampler for bacterial aerosols Appl Microbiol.. 4:300-306.
22. Ehrlich, R. 1960 Application of membrane filters In: Advances in Applied Microbiol-
ogy Vol. 2. W. Umbreit. ed. Academic Press. New York
23. Buchanan, L. M., J. B. Harstad, J. C. Phillips, E. Lafferty, C. M. Dahlgren, and H. M.
Decker. 1972 Simple liquid scrubber for large-volume air sampling Appl. Microbiol .
23:1140-1144.
24 Goetz, A. 1953. Application of molecular filter membranes to the analy sis of aerosols.
Am. Jour. Publ. Health. 43:150-157.
25 May, K. R., and G. J. Harper. 1957 The efficiency of \anous liquid impinger samplers
in bacterial aerosols Brit. Jour. Ind. Med.. 14:287-297
26. May, K. R. 1966. Multistage liquid impinger Bacterial. Rev . 30:559-570.
27 Tyler, M. E., and E. L. Shipe. 1959. Bacterial aerosol samplers. I Development and
evaluation of the all-glass impinger Appl. Microbiol . 7-337-349
28. Cown, W. B., T. W. Kethley, and E. L. Fincher. 1957 The critical orifice impinger as a
sampler for bacterial aerosols. Appl Microbiol.. 5:119-124
29 Tyler, M. E., E. L. Shipe, and R. B. Painter. 1959 Bacterial aerosol samplers III.
Comparison of biological and phy sical effects in liquid impinger samples Appl Micro-
biol 7:355-362
30. Shipe, E. L., M. E. Tyler, and D. N. Chapman. 1959. Bacterial aerosol samplers. II
Development and evaluation of the Shipe sampler Appl Microbiol . 7'349-354
-------
20 Wastewater Aerosols and Disease/Contaminants
31. May, K. R., and H. A. Druett. 1953 The preimpinger, a selective aerosol sampler.
Brit. Jour. Ind. Med . 10:142-151.
32. Anderson, J. D., and C. S. Cox. 1967. Microbial survival. In: Airborne Microbes,
Seventeenth Symp. Soc. Gen. Microbiol., P. H. Gregory and J L. Monteith, eds.
Cambridge University Press, London.
33. Hyslop, N.St.G. 1972. Observations on pathogenic organisms in the airborne state.
Trap. Anim. Health Prod., 4:28-40.
34. Hyslop, N.St.G. 1965. Airborne infection with the virus of foot-and-mouth disease.
Jour. Comp. Path, and Therap., 75:119-126.
35. Thome, H. V., and T. M. Burrows. 1960. Aerosol sampling methods for the virus of
foot-and-mouth disease and the measurement of virus penetration through aerosol
filters. Jour. Hyg , Camb., 58:409-417.
36. Goldberg, L. J., and H. M. S. Watkins. 1965. Preliminary studies with a continuous
impinger for collection of bacterial and viral aerosol samples. In: A Symposium on
Aerobiology, R. L. Dimmick, ed., Nav Biol. Lab., Naval Supply Center, Oakland,
California.
37 Buchanan, L. M., H. M. Decker, D. E. Frisque, C. R. Phillips, and C. M. Dahlgren.
1968. Novel multi-slit large-volume air sampler. Appl. Microbiol., 16:1120-1123.
38. Fannin, K. F., J. C. Spendlove, K. W. Cochran, and J. J. Gannon. 1976. Airborne
coliphages from wastewater treatment facilities Appl Environ Microbiol.,
31:705-710.
39. Peterson, C. M. 1971. Biological sampling system operating principle, operating in-
structions and design considerations. Report No. 7117. Dept. of Army, Ft Detrick,
Frederick, Maryland.
40. Berry, C. M. 1944. An electrostatic method for collecting bacteria from the air. U.S
Publ. Health Rpts., 56:2055-2051.
41. Luckiesh, N., A. N. Taylor, and L. L. Holladay. 1946. Sampling devices for airborne
bacteria Jour. Bacterial ,52:55-65.
42 Houwink, E. H., and W. Rolvink. 1957. The quantitative assay of bacterial aerosols by
electrostatic precipitation. Jour. Hyg., 55:544-563.
43. Morris, E. J., H. M. Darlow, J. F. H. Peel, and W. C. Wright. 1961. The quantitative
assay of mono-dispersed aerosols of bacteria and bacteriophage by electrostatic pre-
cipitation. Jour. Hyg., Camb., 59:487-496.
44. Decker, H. M., L. M. Buchanan, D. E. Frisque, M. E. Filler, and C. M. Dahlgren. 1969.
Advances in large-volume air sampling. Contam. Control, 8:13-17.
45. Lundgren, D., and L. Graf. 1964. Development of an aerosol collector for use in a
microbiological aerosol detection system. Report No. 2548. Litton Systems, Inc.,
Applied Science Div., St. Paul, Minnesota.
46. Johnson, D. E., D. E. Camann, C. A. Sorber, B. P. Sagik, and J. P. Glennon. 1978.
Aerosol monitoring for microbial aerosols near a spray irrigation site. In: Proceedings
of the Health Effects of Land Application of Municipal Wastewater and Sludges, B. P.
Sagik and C. A. Sorber, eds. The Center for Applied Research and Technology, The
University of Texas at San Antonio.
47. Hyslop, N.St.G. 1970. The epizootiology and epidemiology of foot-and-mouth disease.
In: Advances in Veterinary Science Academic Press, Inc., New York.
48. Hyslop, N.St.G. 1971. Factors influencing the epidemiology and epizootiology of air-
borne disease. Jour. Am. Vet. Med. Assoc.. 159:1500-1507.
49. Curtis, J. J. 1969. An evaluation of two large-volume air sampling devices. Appl
Aerobiol. Div., Fort Detnck, Frederick, Maryland.
50. Gerone, P. J., R. B. Couch, G. V. Keefer, R. G. Douglas, E. B. Derrenbacher, and V.
Knight. 1966. Assessment of experimental and natural aerosols. Bacterial. Rev.,
30:576-584.
51. Errington, F. P., and E. O. Powell. 1969 A cyclone separator for aerosol sampling in
the field. Jour. Hyg., Camb., 67:387-399.
52. White, L. A., D. J. Hadley, D. E. Davids, and R. Naylor. 1975. Improved large-volume
sampler for the collection of bacterial cells from aerosol. Appl. Microbiol.,
29:335-339.
53. Teltsch, B., and E. Katzenelson. 1978. Airborne enteric bacteria and viruses from
spray irrigation with wastewater. Appl. Environ. Microbiol , 35:290-2%.
-------
Kerby F. Fannin 21
54. May, K. R. 1945. The cascade impactor: an instrument for sampling coarse aerosols.
Jour. Sci. Instruments, 22:187-195.
55. Sonkin, L. S. 1950. Application of the cascade impactor to studies of bacterial aero-
sols. Am. Jour. Hyg., 51:319-342.
56. Harstad, J. B. 1965. Sampling submicron T-l bacteriophage aerosols. Appl. Micro-
biol., 13:899-908.
57. Bourdillon, R. B., O. M. Lidwell, and J. C. Thomas. 1941. A slit sampler for collecting
and counting airborne bacteria. Jour. Hyg., 41:197-224.
58. Decker, H. M., and M. E. Wilson. 1959. A slit sampler for collecting airborne microor-
ganisms. Appl. Microbiol., 2:267-269.
59. Andersen, A. A. 1958. New sampler for the collection, sizing, and enumeration of
viable airborne particles. Jour. Bacterioi, 76:471-484.
60. Kuehne, R. W., and H. M. Decker. 1957. Studies on continuous sampling of Serratia
marcescens using a slit sampler. Appf. Microbiol., 5:321-323.
61. Andersson, R., Bergstrom, and B. Bucht. 1973. Outdoor sampling of airborne bacteria,
results and experiences. In: Airborne Transmission and Airborne Infection. IVth
Internal. Symp. on Aerobiology, J. F. Ph. Hers and K. C. Winkler, eds. John Wiley
and Sons, New York.
62. May, K. R. 1969. Prolongation of microbiological air sampling by a monolayer on agar
gel. Appl. Microbiol., 18:513-514.
63. May, K. R. 1973. Developments in high volume sampling of aerosols. In: Airborne
Transmission and Airborne Infection. IVth Internal. Symp. on Aerobiology, J. F. Ph.
Hers and K. C. Winkler, eds. John Wiley and Sons, New York.
64. May, K. R. 1964. Calibration of a modified bacterial aerosol sampler. Appl. Micro-
biol., 12:37-43.
65. Standard Methods for the Examination of Water and Wastewater. 14th Ed. 1975.
American Public Health Associalion, Washington, D.C.
66. Bordner, R., J. Winter, and P. Scarpino. 1978. Microbiological methods for monitoring
the environment: water and wastes. EPA-600/8-78-017. U.S. Environmental Proleclion
Agency, Cincinnati, Ohio.
67. Hoff, J. C., and W. Jakubowski. 1966. Applicalion of an endpoint dilution melhod to
bacteriophage assay. Appf. Microbiol. 14:468-469.
DISCUSSION
MR. JAKUBOWSKI: The sensitivity of the concentrating method
seems to be a key item for interpreting biologic and epidemiologic data.
It seems that we do not have clear guidelines on how we can arrive at
acceptable sensitivity. I wonder if you would care to offer any com-
ments on how we can arrive at what would be an acceptable level of
sensitivity?
DR. FANNIN: My comment was that I haven't arrived at an accept-
able sensitivity, but I suggested that this be based upon exposure, either
to a population or to an individual, over a limited time period. This is a
very difficult problem. If we are sampling something by using a teaspoon
that may require use of a bucket, we have to evaluate what that sample
from a teaspoon actually means.
The important thing is to evaluate what a low level concentration
means to a population. I am not prepared to make a statement as to what
is an acceptable concentration of specific organisms.
DR. FLIERMANS: I think it is important, if you are talking about
sampling, to talk about methods for detecting organisms. I think that is a
mutually important aspect. One has to consider all methods. Indirect
methods, that is, plating the organisms on some kind of medium, inhibits
other organisms and may even inhibit the ones that you are dealing with.
Would you care to comment on some of the direct methods?
DR. FANNIN: By direct procedures, what are you referring to?
-------
22 Wastewater Aerosols and Disease/Contaminants
DR. FLIERMANS: I am referring to things like fluorescence, look-
ing at total numbers, looking for specific organisms that you are dealing
with. The sensivitity to these kinds of things could be very low.
DR. FANNIN: I am familiar with these methods, and I am also
aware that these have been used in other investigations. Primarily, to my
knowledge, much of the effort has been related to detecting viable or-
ganisms as determined by their ability to grow, rather than detecting the
antigen itself in the sample.
I acknowledge that this is a very effective method of detecting
organisms.
MR. WITHAM: Was your study based on any of your own data?
DR. FANNIN: This is an overview, a presentation of various meth-
ods as an introduction to this particular symposium. It is not based upon
our data.
DR. WITHAM: Have you actually come across a sampler with
which you can unequivocally collect viral data?
DR. FANNIN: Yes. The use of a sampler is dependent upon the
concentration of the viruses in the aerosol, but there are many samplers
which have been demonstrated to be quite effective in the collection of
virus. Yes, that is not a difficult task, but at very low level concentra-
tions it becomes a difficult task.
DR. SCHAUB: Thank you very much, Dr. Fannin. That was a most
interesting presentation. I think that it increases everyone's awareness
of the potential problems in dealing with sampling of aerosols, a very
sophisticated and complex problem, and there is still a lot of work that
needs to be done on it before we can really come up with some totally
satisfactory conclusions about the efficacy of aerosol sampling.
-------
23
Indicators and Pathogens in Wastewater Aerosols
and Factors Affecting Survivability
Charles A. Sorber and B. P. Sagik
The Center for Applied Research and Technology
The University of Texas at San Antonio
San Antonio, Texas 78285
ABSTRACT
This paper attempts to consolidate the information available on wastewater microbiolog-
ical aerosols. Organisms of concern which have been isolated from wastewater are identi-
fied. Where available, information on their probable survival in aerosols is presented. Data
is evaluated as to the relative survival rates of pathogens and traditional indicator organ-
isms. Further, the paper delineates those areas where more work is required, for example
in the identification and selection of (an) appropriate organism(s) and sampling methods
permitting routine monitoring of wastewater aerosols in cases where this is considered
necessary.
The potential health effects of wastewater aerosols continue to be of
concern, based both on the numbers of pathogens found in wastewater
and on still inadequate information on minimal infectious doses of those
pathogens, particularly viruses. This concern has been exacerbated by
the increasing trend to operate wastewater land application facilities in
populated areas, especially as urban sprawl continues to engulf existing
conventional treatment facilities.
Studies seeking to resolve some of the questions regarding aerosol-
ized wastewater have addressed, in turn, the concentration and fate of
pathogens in sewage, the effect of various wastewater treatment unit
processes on the organisms of concern, the amount of wastewater aero-
solized, the immediate effect of aerosolization on the organisms (aerosol
shock or aerosol impact), and the biological decay of the organisms
during transport as aerosols. As knowledge of the concentration and
extent of the transport of these organisms has increased, greater empha-
sis now must be placed on the more difficult question: What is the level
of risk associated with various concentrations of these aerosols?
This paper seeks to consolidate, in review form, the information avail-
able on wastewater microbiological aerosols. It attempts to evaluate the
factors which affect the survival of aerosolized microbes, with particu-
lar attention to their potential health effects. Field data are considered in
an effort to identify one or more indicator organisms to be used in
monitoring wastewater aerosols.
-------
24
Wastewater Aerosols and Disease/Contaminants
PATHOGENS IN WASTEWATER
The concentration of microorganisms in domestic sewage is influ-
enced by a complex of several factors including demography as well as
seasonally. The array of potentially pathogenic microorganisms encom-
passes bacteria, helminthic parasites, protozoans, and viruses (Table 1).
The presence and survival of these major groups of pathogens in waste-
water have been reviewed by Foster and Engelbrecht (1), and more
recently, Akin and his associates (2), and Sproul (3). Whereas patho-
genic organisms such as Salmonella typhosa have a relatively short
survival time in wastewater, other pathogens, including Mycobacterium
spp., Ascaris ova, and certain enteric viruses, appear to be highly resis-
tant to environmental stress.
Table 1. Selected Organisms of Health Concern That May Be Present
in Sewage from U.S. Communities (2)
Organisms
Disease
Reservoir(s)
Bacteria
Salmonella
(Approx 1,700 types)
Shigella (4 spp )
Eschenchia colt
(enteropathogenic types)
Enteric viruses
Enteroviruses
(67 types)
Rotaviruses
Parvovirus-hke agents
(at least 2 types)
Hepatitis A virus
Adenoviruses
(31 types)
Protozoa
Balantidium coli
Enfamoeba histolytica
Giardia lamblia
Helminths'
Nematodes (Roundworms)
Ascaris lumbricoides
Ancylostoma duodenale
Necator amencanus
Ancylostoma braziliense (cat hookworm)
Ancylostoma canmum (dog hookworm)
Entembius vermicularis (pmworm)
Strongyloides stercoralis (threadworm)
Toxocara cati (cat roundworm)
Toxocara cants (dog roundworm)
Tnchuris tnchiura (whipworm)
Cestodes (tapeworms)
Taenia sagmata (beef tapeworm)
Taenia so/ium (pork tapeworm)
Hymenolepis nana (dwarf tapeworm)
Echinococcus granulosus (dog tapeworm)
Echinococcus multtloculans
Typhoid fever
Salmonellosis
Shigellosis
(bacillary dysentery)
Gastroenteritis
Gastroenteritis, heart
anomalies, meningitis,
others
Gastroenteritis
Gastroenteritis
Infectious hepatitis
Respiratory disease,
conjunctivitis, others
Balantidiasis
Amebiasis
Giardiasis
Ascanasis
Ancylostomiasis
Necatonasis
Cutaneous larva migrans
Cutaneous larva migrans
Enterobiasis
Strongyloidiasis
Visceral larva migrans
Visceral larva migrans
Trichunasis
Taeniasis
Taemasis
Taeniasis
Unilocular
echmococcosis
Alveolar hydatid disease
Man, domestic and
wild animals, and birds
Man
Man, domestic animals
Man, possibly lower
animals
Man, domestic animals
Man
Man, other primates
Man
Man, swine
Man
Man, domestic and
wild animals
Man, swine''
Man
Man
Cat
Dog
Man
Man, dog
Carnivores
Carnivores
Man
Man
Man
Man, rat
Dog
Dog, carnivore
-------
Charles A. Sorter and B. P. Sagik
Table 2. Removal of Organisms by Conventional Wastewater
Treatment (3)
25
Treatment
Plain sedimentation
Trickling filters
Activated sludge
Agent
Viruses:
Polio 1
Polio 1,2, 3
Parasites
Beef tapeworm eggs
E histolytica cysts
Bacteria:
Mycobacterium tuberculosis
Coliform
Viruses:
Coxsackie A9
Echovirus 12
Polio 1
Mixed (natural)
Parasites:
Beef tapeworms eggs
E. histolytica cysts
Bacteria
Mycobacterium tuberculosis
S. typhosa
Coliform
Ps. aeruginosa
Cl. perfnngens
Viruses:
Coxsackie A9
Polio 1
Mixed (native)
Polio 1,2, 3
Parasites
Beef tapeworm eggs
E histolytica cysts
Bacteria
Salmonella typhosa
Vibrio cholera
Mycobacterium tuberculosis
Coliform
Fecal Streptococci
Removal (%)
0
*to69
0-12
50
Oto*
50
27-96
94
83
85
•to 69
30
*
90-999
45
72
98
+74 (increase)
92
96-99
79-94
53-71
76-90
0
*
86-99
96-100
90 +
97
96
Test System
bench
plant
plant
bench
plant
plant
bench
bench
bench
bench
plant
bench
plant
bench
plant
plant
plant
plant
plant
bench
bench
plant
plant
bench
plant
bench
bench
bench
bench
bench
* Incomplete
Several papers have explored various aspects of trie-potential public
health effects of wastewater treatment processes (1-9). However, before
a rational assessment can be made regarding the degree of health risk
posed by wastewater aerosols, the fate and distribution of pathogenic
and indicator microorganisms between the solid and liquid phases of
wastewater as a function of wastewater treatment must be considered
(Table 2). Primary treatment alone does not significantly reduce the
pathogen load in domestic wastewater, although primary sludges jnay
contain large numbers of parasite eggs. The sludge biomass generated
by conventional secondary treatment, however, may be expected to
contain a major portion of that microbial population which has been
removed from the incoming wastewater.
-------
26 Waste water Aerosols and Disease/Contaminants
Table 3. Results of Bacterial Screens at Several Wastewater Treatment
Facilities
(cfu/100ml)
Pleasanton" Portland'1 Chicago'' Kerrville"
Citrobacter
Clostridium
Edwardsiella
Enterobacter
Escherichia
Klebsiella
Leptospira
Mycobactenum
Providencia
Serratia
Staphylococcus
Fecal coliform
Total colrform
Total plate count
• 50 x 10-'
28 x 102
<50 x 10"
30 x 10'
1 0 x 10"'
60 x 10s
46 x 103
70 x 10-
10x10'
<50 x 10-
30 x 10s
1 0 x 10'
11x10"
58 x 10"
66 x 103
50 x 10-
67 x 103
37 x 10"
13x10'
<33 x 103
66 x 103
33 x 102
53 x 10-
1 8 x 10s
48 x 10'
<30 x 102<
1 5 x 103
<30 x 10"
20 x 10-
•-30 x 10"
1 Ox 105
24 x 103
1 3 x 10s
<30x 103'
<30 x 102'
20 x 10s
1 0 x 10s
37 x 10'
82 x 10'
>6.7 x 102
>1 2x10-
53 x 10s
1 4 x 104
10x10'
67 x 10!
87 x 103
81 x 10-
1 4 x 10s
"Ponded secondary effluent
h Aeration basin
• None detected
Analyses in our laboratory of several large-volume samples from
wastewater treatment facilities have yielded confirmed isolates of spe-
cies of Clostridium, Enterobacter, Escherichia, Klebsiella, Leptospira,
Mycobacterium, Providencia, and Staphylococcus as shown in Table 3.
It should be noted that the levels of these organisms vary considerably.
Bacterial pathogen concentrations in treated wastewater have been re-
ported over a wide range. Tables 3 and 4 provide examples of the rela-
tive numbers of selected pathogens and indicator organisms from recent
field studies. The data in Table 4 were from a very extensive study
which investigated a secondary wastewater treatment plant effluent used
in spray irrigation (10). Similar data have been developed for aeration
basins at operating activated sludge treatment facilities (11,12).
Table 4. Relative Numbers of Selected Microorganisms in the Effluent
Wastewater Samples (10)
Microbiological
parameter
Standard plate count
Total coliform
Pseudomonas
Fecal coliform
Klebsiella
Coliphage
Streptococci
Clostndium perfrmgens
Enteric viruses (5 day)
Concentration
units
No./ml
mfc/ml
cfu/ml
mfc/ml
cfu/ml
pfu/ml
ctu/ml
mpn/ml
pfu/ml
Geometric
mean
699,000
7,480
1,050
795
388
224
673
539
0017
Ratio of
total coliform
934
1 000
0140
0106
0052
0030
0009
0.007
0.000002
The numbers of viruses reported in domestic wastewaters also vary
widely and will depend on the virus-detection techniques employed.
-------
Charles A. Sorter and B. P. Sagik 27
Shuval (13) reported average effluent recoveries for different communi-
ties from about 500 plaque forming units (pfu)/l to over 1600pfu/l. Other
reports have indicated concentrations of up to 7000 PFU/1 for raw se-
wage to about 50 pfu/1 for chlorinated secondary effluent (8,14).
Concentration of the microbial population into the secondary biomass
makes it essential to implement sludge-processing practices that can
diminish the concentrations of pathogenic bacteria, of helminth ova, and
of viruses. Anaerobic sludge digestion, aerobic sludge stabilization, lime
stabilization, composting, and sludge lagooning are among the more
popular methods for treating waste sludges. A summary of treatment
effectiveness of some of these processes in pathogen removal can be
found in Table 5.
An Environmental Protection Agency report on microbial survival
during anaerobic digestion indicated that while coliform populations are
reduced greatly, other pathogens, such as Mycobacterium and Ascaris
ova, can withstand prolonged digestion (16). Several laboratory studies
have reported the fate of selected viruses during anaerobic digestion
Table 5. Municipal Wastewater Treatment Plant Inactivation of Patho-
gens in Sludges (15)
Treatment Range of Effectiveness
Lime Kills pathogenic bacteria; highly effective at high pH (>11 5)
Heat—pasteurization Destroys pathogens at 70°C for 112 to 1 hour
Composting Mechanical pathogen-free after 1 day, spores 1 week
Contour: pathogen free after 1 week
Anaerobic digestion Bacteria: reduced at approximately natural die-off rate
Helminth ova: at least 1 month for destruction
Cysts: destroyed in 10 days at 30°C
Virus, some survive long periods
Aerobic digestion Reduces pathogens to low numbers
(17,18). Inactivation rates ranged from 74.9%/day for Echovirus 11 to
90%/day for poliovirus to 97%/day for Coxsackievirus A-9 usingxadded
free test viruses. Much slower rates were observed using solids-incorpo-
rated poliovirus (19). While significant pathogen reductions can be
achieved by anaerobic digestion, actual field digesters appear to be less
efficient, owing, undoubtedly, to the continuous input of contaminated
raw sludges coupled with probable short-circuiting and incomplete mix-
ing (20).
Generally, disinfection (specifically chlorination) of effluents before
discharge provides the last step in the treatment scheme. Difficulties
arise in comparing published results of chlorination studies because of a
lack of specific information on initial chlorine dosage, reaction tempera-
ture, pH, and the level of organic or inorganic nitrogenous compounds
present. Selected microorganisms, including some species of Mycobac-
-------
28 Wastewater Aerosols and Disease/Contaminants
terium, amebic cysts, and certain enteric viruses (among them the agent
of waterborne hepatitis), are reported to be more chlorine-resistant than
are indicator coliform organisms (3).
Thus, the treatment train, without disinfection of the effluent, can be
relatively effective in reducing the levels of most microorganisms. It is
probable, however, that biological treatment leaves not less than 1 to
10% of Salmonella, Mycobacterium and some human enteric viruses in
the wastewater effluent.
WASTEWATER AEROSOLS
Those particles in the size range 0.01 to more than 50jxm, which are
suspended in air, are defined as aerosols. Potentially pathogenic aero-
sols are generated as a result of the physical processes of aerating,
trickling, and spraying wastewaters and sludges. The density of mi-
croorganisms in aerosols is a function of the density of a specific organ-
ism in the wastewater, aeration basin, or sludge; the amount of material
aerosolized; the effect of aerosol shock (impact); and, finally, biological
decay of the organisms with distance in the downwind direction
(8,11,21,22).
A number of studies have been conducted in an attempt to identify
quantitatively the levels of microorganisms emitted in aerosols gener-
ated by wastewater spray irrigation and other wastewater treatment
processes (11,21-30). In attempting to interpret these data an important
consideration is the quantity of a particular pathogen required to initiate
an infection in individuals. This probably is the most difficult factor to
assess. Over the past few years, quantitative procedures for enumerat-
ing pathogen levels in aerosols have been developed. Unfortunately,
equally sensitive real-time epidemiological procedures have not kept
pace. Recently, Pipes (31) edited a volume containing a summary of
published infectivity data for several pathogenic bacteria and for polio-
virus vaccine. These data, in part, are derived from studies using labora-
tory strains in healthy volunteers. As such, they may have limited rele-
vance to the problem under discussion here.
Factors Affecting Survival
Aerosol Impact
Immediately after aerosolization, numerous environmental factors
have an impact on the viability of aerosolized organisms. The individual
effects of relative humidity, temperature, and sunlight, on selected or-
ganisms, have been described elsewhere (8). These initial die-off factors
in the aggregate have been referred to as aerosol shock or aerosol
impact.
In an early study on bacterial aerosols at a spray irrigation site, the
initial impact factors were reported to contribute to a 0.5 logic loss in
concentration of the test bacterial group (26). In another study using
exogenously introduced f2 bacteriophage, similar results were observed
(21). A recent, more definitive study explored a wider range of patho-
gens and indicator organisms (27,32). The relative aerosolization sur-
vival (the relative importance of initial aerosol shock) for these organ-
isms is presented in Table 6 for each microbiological entity measured.
The ratio of the aerosol to wastewater population concentrations at the 5
-------
Charles A. Sorter and B. P. Sagik
29
Table 6. Geometric Means and Ratios of Wastewater and Aerosol Con-
centrations of Microbiological Parameters (32)
Geometric
Mean
Wastewater
Cone.
(no./ml)
Geometric Mean Aerosol
Concentrations
(no./m'of Air)
Aerosol/Wastewater Ratio
of Geometric
Mean Concentrations
Upwind
Downwind
Downwind
FIRST RUNS
Standard
plate count
Total coliform
Fecal coliform
Cohphage
Fecal
streptococci
699,000
7,500
800
220
67
Pseudomonas 1 ,050
Klebsiella
Clostridium
pertnngens
SECOND RUNS
Standard plate
count
Total coliform
Cohphage
Fecal
streptococci
Mycobactena
Enterovirus
390
54
150,000
4,900
290
34
46
012
805
< 05
< 0.3
< 01
< 0.6
< 15
< 5
< 09
Upwind
300
< 02
< 01
015
0.30
5-20 m
2,570
57
1 0
034
1 4
72
< 5
1.5
100-200 m
880
1 2
< 03
018
1 9
43
< 5
1 1
Downwind
50m
450
252
0.51
034
080
0014
100m
330
0.59
023
029
082
5-20 m
0.0037
00008
0.0013
00012
0.021
0068
<001
0027
100-200 m
0.0013
00002
< 0.0004
00006
0028
0.011
<001
0020
Downwind
50m
0.0028
00005
00017
0.0100
00176
011
100m
0.0021
0.0001
00008
0.0085
00178
to 20 m distance should indicate the relative survival of the microbes
through the initial environmental impact associated with aerosolization.
Most of the pathogenic bacteria (Pseudomonas, Streptococcus, Clostri-
dium perfringens, Mycobacterium) were substantially less affected by
the initial aerosol shock than were the indicator organisms and coli-
phage. Klebsiella was found to be more subject to initial shock than
were the other pathogenic bacteria. However, the absolute extent of its
susceptibility is not known because the aerosol concentration of this
genus was below detection limits. Enteroviruses (at 50 m) were found to
be least affected by aerosol shock (27).
Biological Decay
Several factors contribute to biological die-off or decay, including
ultraviolet radiation, temperature, and relative humidity. The relative
magnitude of biological decay or microbiological depletion with distance
from the aerosol source has been evaluated. This was accomplished by
first normalizing the observed aerosol microorganism concentration us-
ing the source concentration for a particular organism. The mean close-
downwind (5 to 20 m) aerosol concentration of that organism can give a
reasonable estimate (post aerosol impact) of the aerosol concentration at
-------
30 Wastewater Aerosols and Disease/Contaminants
20 m from the wet-line edge. The rate of microbiological decay can be
obtained by determining the change between the close-downwind con-
centration and that of some further downwind point, for example 100 m.
This technique was applied to four representative microbiological
measurements (standard plate count, total coliform, Pseudomonas, fe-
cal Streptococcus). The standard plate count and total coliform parame-
ters exhibited a rate of microbiological decay that was quite rapid,
amounting to about one order of magnitude in 100 m for total coliform
and about half an order of magnitude in 100 m for a standard plate count.
The latter corresponds to previously published data (26). There was
virtually no effect on Pseudomonas, and the decay of fecal Streptococ-
cus with distance was very slight.
As a methodology for detecting low levels of enteric viruses in waste-
water aerosols has only recently been described (33), the aerosolized
level for these viruses was obtained at only one distance (50 m) and for
only two samples. Therefore, the calculation of decay was not possible
(27). However, significant decay for enteric viruses is considered un-
likely at any reasonable distance from the spray source.
Indicator Organisms
Another consideration in the overall evaluation of field data is the
choice of an indicator organism. This can be approached by evaluating
the ratio of indicator organisms to pathogenic organisms. After adjust-
ing the data from one extensive field study to common units, this com-
parison was made (27). Table 4 presents the ratio of each parameter's
geometric mean to the total coliform geometric mean. The four selected
pathogenic bacteria, fecal coliform, and coliphage all lie within one and
one-half orders of magnitude of each other. The observed virus concen-
trations in the effluent samples were at least three orders of magnitude
less than those of any bacterial pathogen.
Wastewater monitoring for potential microbiological health hazards
traditionally focuses on the concentrations of indicator organisms, such
as total coliforms, fecal coliforms, and the standard plate count. These
easily-assayed microbial groups are plentiful in domestic wastewater.
The presence of fecal coliforms in the aquatic environment is consid-
ered as indicative of the possible presence of associated pathogenic
bacteria and human viruses (Table 7). The pathogens are themselves
difficult to assay and seldom occur at readily detectable concentrations.
Thus, the substantially higher concentrations of total coliform and stan-
dard plate count found in the aeration basins (relative to the effluent
ponds) are taken to indicate the existence of relatively higher aeration
basin concentrations of pathogens such as human enteroviruses, Kleb-
siella, Pseudomonas, Mycobacterium, and fecal Streptococcus.
The sample data base in the study conducted at Pleasanton, California
cited above (27), consisted of 47 daily effluent composite samples and
seven grab samples. Summary statistics calculated for each of the ten
indicator and pathogenic microbiological parameters can be found in
Table 6. Various statistical techniques were used to evaluate these data,
and in each case very poor correlation was shown between the patho-
-------
Charles A. Sorter and B. P. Sagik 31
Table 7. Waterborne Outbreaks (1973-1976) Correlated With Indicator
Bacteria Occurrences (31)
Caustive agent Water supply Indicator occurrence
Shigella Richmond Heights, FL Excessive fecal coliform
Salmonella typhosa Homestead, FL Excessive coliform
Toxigenic E. co/i Orator Lake Nat Park, OR Excessive coliform
Intestinal agent (not identified) Girls camp in PA 324 fecal coliform/100 ml
Shigella Church Camp in Ml Excessive fecal coliform
Intestinal agent (not identified) Camp Grounds, ID 190 total colrform/100 ml
Shigella River bathing area, Dubuque, IA 17,500fecalcoliform/100ml
gens and any of the customary indicator organisms. On the other hand,
there was good correlation between total coliform and fecal coliform.
The daily concentrations of each type of microorganism in the Pleas-
anton pond effluent varied at least tenfold and sometimes over one hun-
dredfold during the study period. However, the observed changes in the
traditional indicator organism concentrations had virtually no relation to
the daily changes in the pathogen concentrations. Thus, the use of
wastewater indicator organisms such as total coliform or fecal coliform
for daily monitoring of effluent quality was inadequate as a means of
detecting significant changes in bacterial pathogen concentrations. At
the same time it does not appear from these data that coliphage would
have been a good choice for monitoring viruses.
We hasten to note, however, that Fannin and his coworkers (29) have
proposed the use of coliphages as indicators of aerosolization from
wastewater treatment plants. From the data obtained by these research-
ers, it was suggested that one could estimate animal virus levels by use
of coliphages. In a later paper, Fannin and his colleagues (34) concluded
that wastewater treatment facilities could serve as a continuous source
of low level animal virus aerosols. They noted that phages were more
stable than coliforms in the airborne state and, therefore, more accept-
able as indicators of airborne animal virus concentrations. That phages
are more stable in wastewater aerosols than are members of the coliform
group appears to be borne out by extensive field data; that their stability
approaches that of human viruses has yet to be substantiated.
Engelbrecht and his associates (35-37) have been concerned with iden-
tifying an alternative to coliform bacteria as indicators of fecal contami-
nation. They have found Mycobacterium phlei, Mycobacterium avium,
and a yeast (Candida parapsilos) to be among the more promising candi-
date organisms. These organisms have been known to survive prolonged
contact with disinfectants. The data presented in Table 6 suggest that
Mycobacterium and fecal Streptococcus are quite hardy in wastewater
aerosols as well.
In selecting an indicator organism one must consider, among other
things, the ability of the organism to survive in the environment of
concern (aerosolized wastewater or sludge), the relationship of level of
indicator organism to pathogen concentration, and the ease and speed
with which the presence of the organism can be determined quantita-
tively. Current data suggest that of all the proposed indicators, fecal
Streptococcus most closely satisfies these criteria for aerosolized
wastewaters.
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32 Wastewater Aerosols and Disease/Contaminants
SIGNIFICANCE OF DATA AND CONCLUSIONS
Unfortunately, there have been few studies conducted in the United
States designed to evaluate the epidemiological significance of wastewa-
ter aerosols from a spray irrigation site. Obtaining quantitative aerosol
data, together with the development of predictive models, provides only
part of the necessary information. The next, and perhaps most impor-
tant, step involves putting this information to direct use through deter-
mination of the effects of these aerosols on humans. Clark and his
associates (38) have summarized the results thus far of an ongoing ser-
oepidemiological study of treatment plant workers and obtained evi-
dence only of increased subclinical viral infections. Workers exposed to
dried wastewater dusts were reported by Mattsby and Rylander (39) to
have higher incidences of work-related fevers, diarrhea, and other
symptoms consistent with endotoxin exposure. Fannin and his cowork-
ers (40), as reported by Kowal and Pahren (41) found increased risk of
respiratory and gastrointestional illness in persons living within 600 m of
an activated sludge wastewater treatment plant in Tecumseh, Michigan,
but related this to socioeconomie factors. In contrast, no health hazards
were detected by Johnson and his associates (12) for persons living
beyond 400 m of a Chicago area wastewater treatment plant or for
school children active within 100 m of a Portland area wastewater treat-
ment plant (11).
Considerable question remains as to the level of risk to be associated
with microbiological aerosols from wastewater treatment operations in
the United States, including spray irrigation. These uncertainties are
compounded by the dependence of the concentration of organisms in
the aerosols upon the demographic and socioeconomie structure of the
community, the type of wastewater treatment provided, the method of
application, and the prevailing meteorological conditions. Data from
several field studies suggest that of the potential indicator organisms,
fecal Streptococcus may represent the most logical choice at this time
for monitoring aerosolized wastewaters.
References
1. Foster, D. H., and R. S. Engelbrecht. 1973. Microbial hazards in disposing of wastewa-
ter on soil. In: Recycling Treated Municipal Wastewater and Sludge through Forest
and Cropland, W. E. Sopper and L. T. Kardos, eds. Pennsylvania State University
Press, University Park. pp. 247-270.
2 Akin, E. W., W. Jakubowski, J. B. Lucas, and H. R. Pahren. 1978. Health hazards
associated with wastewater effluents and sludge: microbiological considerations. In:
Risk Assessment and Health Effects of Land Application of Municipal Wastewater
and Sludges, B. P. Sagik and C. A. Sorber, eds. Center for Applied Research and
Technology, The University of Texas at San Antonio, pp. 9-25.
3. Sproul, O. 1978. The efficiency of wastewater unit processes in risk reduction In: Risk
Assessment and Health Effects of Land Application of Municipal Wastewater and
Sludges, B P. Sagik and C. A. Sorber, eds. Center for Applied Research and Technol-
ogy, The University of Texas at San Antonio, pp. 282-296.
4. Gleason, T. L., F. D. Kover, and C. A. Sorber. 1977. Health effects—land application
of municipal wastewater and sludge. In: Disposal of Residues on Land. Information
Transfer Inc., Rockville, Maryland, pp 203-210.
5 Hickey, J. L. S., and P. C. Reist. 1975. Health significance of airborne microorganisms
from wastewater treatment process. I Summary of investigations. Jour. Water Poll.
Control Fed., 47:2741-2757.
-------
Charles A. Sorter and B. P. Sagik 33
6. Hickey, J. L. S., and P. C. Re 1st. 1975. Health significance of airborne microorganisms
from wastewater treatment processes. II. Health significance and alternatives for
action. Jour. Water Poll. Control Fed., 47:27'58-2773.
7. Sepp, E. 1971. The Use of Sewage for Irrigation—a Literature Review. Bureau of
Sanitary Engineering, State of California.
8. Sorber, C. A., S. A. Schaub, and H. T. Bausum. 1974. An assessment of a potential
virus hazard associated with spray irrigation of domestic wastewaters. In: Virus Sur-
vival in Water and Wastewater Systems, J. F. Malina and B. P. Sagik, eds. Center for
Research in Water Resources, University of Texas at Austin, pp. 241-252.
9. Sorber, C. A., and K. J. Guter. 1975. Health and hygiene aspects of spray irrigation.
Amer. J. Publ. Health, 65:47-52.
10. Sorber, C. A., B. P. Sagik, and B. E. Moore. 1979. Aerosols from municipal wastewa-
ter spray irrigation. In: Utilization of Municipal Wastewater and Sludge Recycling on
Forest and Disturbed Land, W. Sopper and S. Kerr, eds. The Pennsylvania State
University Press, University Park. pp. 255-263.
11. Johnson, D. E., D. E. Camann, H. J. Harding, and C. A. Sorber. 1979. Environmental
monitoring of a wastewater treatment plant. EPA-600/1-79-027, U.S. Environmental
Protection Agency, Cincinnati, Ohio.
12. Johnson, D. E., D. E. Camann, J. W. Register, R. J. Prevost, J. B. Tillery, R. E.
Thomas, J. M. Taylor, and J. M. Hosenfeld. 1978. Health implications of sewage
treatment facilities. EPA-600/1-78-032. U.S. Environmental Protection Agency, Cin-
cinnati, Ohio.
13. Shuval, H. I. 1970. Detection and control of enteroviruses in the water environment.
In: Developments in Water Quality Research, H. I. Shuval, ed. Ann Arbor Science
Publishers, Ann Arbor, Michigan.
14. Berg, G. 1978. Viruses in the environment: assessment of risk. In: Risk Assessment
and Health Effects of Land Application of Municipal Wastewater and Sludges, B. P.
Sagik and C. A. Sorber, eds. Center for Applied Research and Technology, The
University of Texas at San Antonio, pp. 216-225.
15. Dorcey, A. H. J., and R. S. Howe. 1978. Public choice and the land application of
municipal wastewaters and sludges. In: Risk Assessment and Health Effects of Land
Application of Muncipal Wastewaters and Sludges, B. P. Sagik and C. A. Sorber, eds.
Center for Applied Research and Technology, The University of Texas at San Anto-
nio, pp. 303-324.
16. Environmental Protection Agency. 1974. Process design manual for sludge treatment
and disposal. EPA 625/1-74-006.
17. Bertucci, J. L., C. Lue-Hing, D. R. Zenz, and S. J. Sedita. 1975 Studies on the
inactivation rates of five viruses during anaerobic sludge digestion. Report No. 75-21.
Department of Research and Development, Metropolitan Sanitary District of Greater
Chicago.
18. Ward, R. L., and C. J. Ashley. 1976. Inactivation of poliovirus in digested sludge
Appt. Environ. Microbioi, 31:921-930.
19. Sanders, D. A., J. F. Malina, Jr., B. E. Moore, B. P. Sagik, and C. A. Sorber. 1979.
Fate of poliovirus during anaerobic digestion. Jour. Water Poll. Control Fed.,
51:333-343.
20. Moore, B. E., B. P. Sagik, C. A. Sorber. 1978. Land application of sludges: minimizing
the impact of viruses on water resources. In: Risk Assessment and Health Effects of
Land Application of Municipal Wastewater and Sludges, B. P. Sagik and C. A. Sor-
ber, eds. Center for Applied Research and Technology, The University of Texas at
San Antonio, pp. 154-167.
21. Bausum, H. T., S. A. Schaub, and C. A. Sorber. 1976. Viral and bacterial aerosols at a
wastewater spray irrigation site. Presented at the 76th Annual Meeting, American
Society for Microbiology, Atlantic City, New Jersey.
22. Katzenelson, E., and B. Teltch. 1976. Dispersion of enteric bacteria by spray irrigation
Jour. Water Poll. Control Fed., 48:710-716.
23. Ledbetter, J., and C. Randall. 1965. Bacterial emissions from activated sludge units.
Ind. Med. Surg., 34:130-133.
24. Napolitano, P., and D. Rowe. 1966. Microbial content of air near sewage treatment
plants. Water and Sew. Works, 113:480-483.
25. Randall, C. W., and J. O. Ledbetter. 1966. Bacterial air pollution from activated
sludge units. Amer. Ind. Hygiene Assoc. Jour., 27:506-519.
-------
34 Wastewater Aerosols and Disease/Contaminants
26. Sorber, C. A., H. T. Bausum, S. A. Schaub, and M. J. Small. 1976. A study of bacterial
aerosols at a wastewater irrigation site. Jour. Water Poll. Control Fed., 48:2367-2379.
27. Camann, D. E., C. A. Sorber, B. P. Sagik, J. P. Glennon, and D. E. Johnson. 1978. A
model for predicting pathogen concentrations in wastewater aerosols. In: Risk Assess-
ment and Health Effects of Land Application of Municipal Wastewater and Sludge, B.
P. Sagik and C. A. Sorber, eds. Center for Applied Research and Technology, The
University of Texas at San Antonio, pp. 240-271.
28. Adams, A. P., and J. C. Spendlove. 1970. Coliform aerosols emitted by sewage treat-
ment plants. Science, 169:1218-1220.
29. Fannin, K. F., J. C. Spendlove, K. W. Cochran, and J. J. Gannon. 1976. Airborne
coliphages from wastewater treatment facilities. Appl. Environ. Microbiol.,
31:705-710.
30. Glaser, J., and J. Ledbetter. 1967. Sizes and numbers of aerosols generated by acti-
vated sludge aeration. Water and Sew. Works, 114:219-221.
31. Pipes, W. O., ed. 1978. Water Quality and Health Significance of Bacterial Indicators
of Pollution. Drexel University, Philadelphia.
32. Johnson, D. E., D. E. Camann, C. A. Sorber, B. P. Sagik, and J. P. Glennon. 1978.
Aerosol monitoring for microbial organisms near a spray irrigation site. In: Risk
Assessment and Health Effects of Land Application of Municipal Wastewater and
Sludges, B. P. Sagik and C. A. Sorber, eds. Center for Applied Research and Technol-
ogy, The University of Texas at San Antonio, pp. 231-239.
33. Moore, B. E., B. P. Sagik, and C. A. Sorber. 1979. Procedure for the recovery of
airborne human enteric viruses during spray irrigation of treated wastewater. Appl
Environ. Microbiol., 38:688-693.
34. Fannin, K. F., J. J. Gannon, K. W. Cochran, and J. C. Spendlove. 1977. Field studies
on coliphages and coliforms as indicators of airborne animal viral contamination from
wastewater treatment facilities. Water Research, 11:181-188.
35. Engelbrecht, R. S., D. H. Foster, M. T. Masarik, and S. H. Sai. 1974. Detection of new
microbial indicators of chlorination efficiency. In: Proceedings Second AWWA Water
Quality Technology Conference, Paper No. X.
36. Engelbrecht, R. S., and E. O. Greening. 1978. Chlorine resistant indicators. In: Indica-
tors of Viruses in Water and Food, G. Berg, ed. Ann Arbor Science Publishers, Inc.,
Ann Arbor, Michigan, pp. 243-265.
37. Engelbrecht, R. S., and C. N. Haas. 1978. Acid-fast bacteria and yeasts as disinfection
indicators: enumeration methodology. In: Proceedings Fifth AWWA Technology
Conference, Paper 2B.
38. Clark, C. S., G. M. Schiff, C. C. Linnemann, G. L. Van Meer, A. B. Bjornson, P. S.
Gartside, C. R. Buncher, J. P. Phair, and E. J. Cleary. 1978. A seroepidemiologic
study of workers engaged in wastewater collection and treatment. In: State of Knowl-
edge in Land Treatment of Wastewater, Volume 2, H. L. McKim, ed. U.S. Army
Corps of Engineers, CRREL, Hanover, New Hampshire, pp. 263-269.
39. Mattsbj, I., and R. Rylander. 1978. Clinical and immunological findings in workers
exposed to sewage dust. J. Occup. Med., 20:690.
40. Fannin, K. F., et at. 1978. Health effects of a wastewater treatment system. EPA-600/
1-78-062. Environmental Protection Agency, Cincinnati, Ohio.
41. Kowal, N. E., and H. R. Pahren. 1979. Health effects associated with wastewater
treatment and disposal—literature review. Jour. Water Poll. Control Fed.,
51:1301-1315.
DISCUSSION
MR. JAKUBOWSKI: The data that you presented on aerosol shock
was derived as a result of spray irrigation. Is aerosol shock something
that one would expect to occur in a wastewater treatment plant?
DR. SORBER: Certainly.
MR. JAKUBOWSKI: Is there any data available to indicate that aer-
osol shock is of the same magnitude as what is observed with spray
irrigation?
DR. SORBER: David Camann might get into this in his modeling
paper a little later. He just indicated that it has been difficult to separate
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Charles A. Sorter and B. P. Sagik 35
the factors between the different places. We don't have the same kind of
data for the wastewater treatment plant.
MR. JAKUBOWSKI: So you believe that the situation with regard
to the standard indicators also holds up for aerosols in wastewater treat-
ment plants and that there would be no correlation between indicators
and pathogens?
DR. SORBER: I think that you can see that in the downwind data
from the sewage treatment plant's aeration basins. The difficult problem
is that with the aeration basins it is hard to identify that portion of the
wastewater which has been aerosolized. The aerosolization efficiency
component is not as readily obtainable from an aeration basin as it is
from a spray source. In fact, I would think that it is far lower because of
the design and construction of the aeration basin.
DR. WARD: I realize there are going to be a lot of possible indica-
tors that people are going to be looking at for years. One of the most
promising ones, as far as viruses go right now, comes out of the study
that is being carried out at Utah State University by Dr. Rex Spendlove.
This study concerns reoviruses, and it appears that it is probably the
best virus indicator there is. The reason for this is that reovirus is found
in the highest numbers by the method he uses to detect it. It is found
consistently, throughout the year, in high numbers. Reovirus is hardier
than the other viruses. So this indicator looks like a good one for future
studies in wastewater. I think it would be good to have this kind of a
study done with aerosol as well.
DR. SPENDLOVE: Rex Spendlove and I are working with a gradu-
ate student, Jack Adams, Ph.D., in the subject you just referred to. We
are finding that the problem with reovirus is that it is very stable once it
gets airborne, but it has a low aerosol efficiency. We get a lot of death
immediately. I don't know how this compares to some of the other
viruses, but once it is aerosolized it is very stable.
DR. LUND: I would like to know what evidence you have for aero-
sol shock?
DR. SORBER: The evidence is based on collection efficiency. It is a
very good question. The evidence that we have is based on collection
efficiencies of the samplers involved in aerosol chambers, not unlike
some of the data that Dr. Fannin showed earlier in the first presentation.
There has always been considerable question as to how efficient these
samplers are.
DR. SCHAUB: I think that everybody can see that there are some
problems with our basic group of indicator organisms, or at least poten-
tial problems. These organisms should be further examined to see
whether or not they really typify the pathogens which are going to be
associated with wastewater aerosols.
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36
Non viable Contaminants from Waste water:
Hexachlorocyclopentadlene Contamination of a
Municipal Wastewater Treatment Plant
John R. Kominsky
Hazard Evaluations and Technical Assistance Branch
Division of Surveillance, Hazard Evaluations, and Field Studies
National Institute for Occupational Safety and Health
Cincinnati, Ohio 45226
ABSTRACT
Municipal wastewater systems have been the repositories of virtually every chemical
known to be produced by man. Sewage sludge and wastewaters have been shown to
contain numerous toxic contaminants, among them heavy metals, persistent pesticides,
and a myriad of other halogenated hydrocarbons. Until recently, there have been few
reports of exposure of sewage workers to toxic chemicals. This report describes an epi-
sode of acute exposure of sewage workers to the industrial chemical, hexachlorocyclopen-
tadiene. Hexachlorocyclopentadiene is an intermediate compound in the manufacture of
pesticides, including aldrin, dieldrin, and Kepone. This episode supports the fact that
sewage workers, who are known already to be at increased risk of exposure to infectious
agents, must also be considered at risk of exposure to toxic chemicals. As increasing
volumes of industrial effluents are channeled each year through municipal wastewater
treatment plants, there will be an increasing potential for both acute and chronic exposure
of sewage workers to these toxicants. This source of occupational disease deserves con-
tinuing evaluation.
More than 1000 new chemical compounds are developed each year in
the United States and are related to the approximately 30,000 chemicals
and 2 million mixtures, formulations, and blends already in commercial
use (1). It appears inevitable that one of the side effects of progress, with
its improved standards of living, will be a continued increase in the vast
array and complexity of the new chemical compounds entering the
wastewater streams. These chemicals for use in domestic, industrial,
and business establishments will, through manufacture or use, eventu-
ally find their way to the municipal sewerage systems creating a poten-
tial for toxic exposures to wastewater treatment plant workers in addi-
tion to a more general problem of environmental contamination.
In the past few years there have been significant efforts toward deter-
mining the nature and concentrations of chemical contaminants in
wastewaters. These efforts have shown that wastewaters contain nu-
merous contaminants, among them heavy metals, chlorinated hydrocar-
bon pesticides, and a myriad of other organic compounds (2-13). Few
studies, however, have characterized the nature of these nonviable con-
taminants that are emitted into the atmosphere via aerosolization from
wastewater treatment facilities, such as trickling filters and the aeration
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John R. Kom/nsky 37
basins of activated sludge processes. A study conducted by Soldano et
al. (14) concludes that sewage treatment facilities are a source of air-
borne organo-mercury compounds, as well as elemental mercury. The
aeration basins of activated sludge units are reported to be sources of
aerosolized elemental Hg, Pb, and Cd (15), and gaseous NHa (16). Car-
now et al. (17) conducted a detailed study to determine whether or not
an activated sludge plant was posing a health hazard to a Chicago com-
munity. Twenty nonviable contaminants were monitored including five
gases (NHa, C12, NO2, H2S, and SO2) and 15 associated with suspended
particulate matter (particulate (SO4)=, (NO3)=, V, Cr, Mn, Ni, Cu, As,
Se, Cd, Sn, Sb, Hg, and Pb). The study concluded that the plant was not
having a detectable adverse health effect on residents potentially ex-
posed to the nonviable aerosols emitted. Unfortunately, these studies,
did not include any consideration of the health effects on sewage work-
ers potentially exposed to these nonviable contaminants. Exposures of
sewage workers to H2S, CHi, CO2, and NHs produced from the biologi-
cal degradation df typical domestic waste is well documented (18-21).
Much of the information on exposures of sewage workers to organic;
chemicals of industrial origin has been gathered as a result of accidental
or unauthorized discharge of these substances into the sewerage system
(22-26). This paper will describe one such episode of acute exposure of
sewage workers to the industrial chemical, hexachlorocyclopentadiene
(HCCPD) (27). The source of HCCPD was traced to the unauthorized
discharge of the compound into a municipal sewer line. HCCPD is ex-
tremely toxic by dermal, oral, and inhalation routes of exposure (28). In
animals, prolonged intermittent exposure to vapor concentrations at
0.15 ppm led to slight liver and kidney damage. Exposure to higher
concentrations caused diffuse degenerative changes of the brain, heart,
adrenal glands, liver, and kidneys (29). The long-term effects of a tran-
sient exposure are unknown.
BACKGROUND
Sometime during March 1977, an unidentified material began entering
the Morris Forman Wastewater Treatment Plant located along the banks
of the Ohio River in Louisville, Kentucky. Epidemiologic evidence
(Figure 1) suggests that the material may have entered the facility as
early as March 14, when there were concurrent above-background-level
increases in detection of an objectionable odor and in symptoms (22).
The facility operated by the Metropolitan Sewer District (MSD) em-
ploys approximately 200 persons and provides primary and secondary
treatment for about 97% of the residential and industrial sewage gener-
ated by the City of Louisville and Jefferson County. The plant has a
capacity of 105 mgd with a peak storm flow capacity of 338 million
gallons.
On March 26, four MSD employees, using steam, attempted to re-
move an odoriferous, highly viscous, and sticky substance from the bar
screens and grit collection systems. This attempt produced a blue haze
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38
Wastewater Aerosols and Disease/Contaminants
02 4 6 8 10 12 14 16 18 20 22 24 26 28
Figure 1. Employees Noticing Unusual Odor at Plant, by Day
which permeated the primary treatment area and caused about 20 work-
ers to seek medical treatment for tracheobronchial irritation. On March
27, following a heavy rain, the operating personnel observed a blue haze
hovering over the grit collection channels and an objectionable odor
throughout the primary treatment area including the basements of the
buildings containing the sludge-pumping equipment. On March 29, the
plant was closed when analysis showed the wastewater to be chemically
contaminated with HCCPD and octachlorocyclopentene (OCCP). Al-
though airborne concentrations of these chemicals at the time of expo-
sure were unknown, subsequent air monitoring showed the relative air-
borne concentrations of HCCPD to be much greater than OCCP (27).
Four days after the plant closed, HCCPD concentrations in the screen
and grit chambers ranged from 270 to 970 ppb. Airborne HCCPD con-
centrations of the blue haze generated by cleanup procedures measured
19,200 ppb. By comparison, the American Conference of Governmental
Industrial Hygienists (1978) recommends an 8-hour time-weighted aver-
age threshold limit value of 10 ppb with a short-term 15-minute exposure
limit of 30 ppb (30).
Aside from the danger to workers at the plant, other major concerns
at the time were for the residents of the area and cities downstream that
use the river as a source of water (Figure 2). Air quality monitoring
stations, established by the U.S. Environmental Protection Agency
(EPA) around the perimeter of the plant and along contaminated sewer
lines, indicated that there was no inhalation hazard to the residents of
the area. EPA advised that several cities downstream within about 200
-------
John R. Kominsky 39
ILLINOIS
LOUIS-
VILLE
MI EVANSVILLE
ERNON
KENTUCKY
IGOLCONDA
Figure 2. Area Affected by Chemical Wastes
miles, including Henderson, Kentucky; Evansville and Mt. Vernon, In-
diana; and Golconda, Illinois, add activated carbon to their maximum
capability as a precautionary measure until the potential danger period
passed. They also recommended that these cities determine the concen-
trations of HCCPD and OCCP in the raw and treated finished waters.
EPA's involvement has been fully presented by Carter (31).
In the episode reported here, the Hazard Evaluations and Technical
Assistance Branch of the National Institute for Occupational Safety and
Health (NIOSH) served as the primary agency in safeguarding the
health and safety of the workers involved in decontaminating the treat-
ment plant and its contributory sewer lines. Some of the medical and
environmental data collected by NIOSH personnel are presented.
MEDICAL ACTIVITIES
The medical activities included questionnaires, physical examina-
tions, blood and urine tests, and review of medical records. A question-
naire was distributed to all employees in May as a follow-up to a similar
questionnaire utilized April 1 to 2, 1977, by the Center for Disease
Control (22). The NIOSH questionnaire sought information on type and
duration of symptoms. The physical examination was directed toward
signs of irritation of the skin, mucous membranes, and lungs. Blood
specimens were collected and analyzed for complete blood count with
differential, serum glutamate oxalacetate transaminase, lactate dehydro-
genase, alkaline phosphatase, total bilirubin, albumin, total protein, uric
acid, blood urea nitrogen, cholesterol, creatinine, phosphorus, and cal-
cium. Urine specimens were collected for a routine urinalysis. Medical
records were reviewed for the 90 employees seen by the plant physician
during the period from about March 15 to May 15, 1977.
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40 Wastewater Aerosols and Disease/Contaminants
ENVIRONMENTAL EVALUATION AND HAZARD
CONTROL ACTIVITIES
Environmental Monitoring
The workers' airborne exposures to HCCPD and OCCP were concur-
rently monitored using both personal and work area sampling tech-
niques. The compounds were collected on preextracted Chromosorb 102
(20-40 mesh) packed into 7 cm long 4 mm I.D. glass tubes using vacuum
pumps operating at either 0.05 or 0.21/min. The analytes were desorbed
from the Chromosorb 102 with CS2 and analyzed using a gas chromato-
graph equipped with a flame ionization detector (32).
Personal Protective Equipment
The cleanup crew, composed of employees with no or minimal prior
exposure to the contaminated sewage, was thoroughly trained in the use
and limitations of required personal protective equipment. The type of
protective equipment used varied with the conditions of exposure. For
example, the workers involved with high-pressure water cleaning of the
screen and grit chambers wore full-suit airline respirators consisting of a
0.006-gauge polyvinyl chloride slipover jacket with sealed-on hood and
detachable gloves, and trousers with sealed-on boots. Other surface
personnel involved with general plant cleanup operations wore either a
NIOSH-approved half-or full-face pesticide-removing chemical car-
tridge respirator. They also wore disposable plastic coveralls or two-
piece rubber suits, gloves, rubber boots, or whatever combination of
personal protective equipment was necessary to prevent skin contact
with the contaminants. Workers involved in decontamination of the
main interceptor sewer wore open-circuit self-contained breathing res-
pirators. The breathing air was supplied by an approximately 350 cu ft
2400 psi cylinder attached to each worker's Bobcat® or Caterpillar®
tractor. The tractors were used to sequentially push the HCCPD con-
taminated sewage along the sewer floor to a point for removal by a
crane. These workers also wore disposable plastic coveralls taped at the
neck and wrists, disposable plastic gloves, and butyl rubber hip boots.
MEDICAL FINDINGS
Questionnaire
Usable responses were received from 177 treatment plant employees
(23 females, 154 males). Table 1 shows the type and frequency of symp-
toms reported immediately prior to plant closure (March 29). Many of
these employees still reported symptoms as late as 6 weeks after expo-
sure. Particularly frequent were reports of headache (18%), persistent
fatigue (15%), chest discomfort (13%), skin irritation (10%), and cough
(9%). The symptoms reported in Table 1 occurred in workers of all job
categories and in all work areas. The highest number of symptoms were
reported by workers in the primary treatment area and general mainte-
nance personnel.
Medical Examinations
A review of medical records for 90 employees seen by the plant physi-
cian from mid-March to May 15 showed similar symptoms of headache
-------
John R. Kominsky 41
Table 1. Percent of 177 Employees with Symptoms—Questionnaire
May 1977
Symptom
Eye irritation
Headache
Chest discomfort
Fatigue
Sore throat
Cough
Nausea
Skin irritation
Last 2 weeks
March
62
55
34
34
30
24
22
21
Persistence after onset
1 Day
40
45
30
31
25
21
18
17
1 Week
25
28
23
26
11
14
13
13
May
9
18
13
15
5
9
6
10
and mucous membrane and respiratory tract irritation. In addition, sev-
eral unusual symptoms were reported by persons with a history of
acute, high-level exposure including: one report of "burning feet" asso-
ciated with sludge-related boot deterioration; three reports of "sunburn-
like facial irritation;" seven reports of rashes on exposed areas of skin;
and seven reports of transient confusion or "memory loss." These last
symptoms were not accompanied by other neurological complaints and
were not associated with physical signs of neurological impairment.
Twenty-eight exposed persons received chest x-rays, none of which
showed acute changes. Sixteen of these 28 had arterial blood gas tests,
all of which were considered normal. Twenty-two of these 28 persons
also had pulmonary function testing with no pattern of abnormality
observed.
Because of unexpected changes in MSB personnel during the cleanup
operations, NIOSH could not conduct preexposure and serial postexpo-
sure monitoring of all 97 cleanup crew members. Consequently, preex-
posure monitoring was only conducted on 52 (54%) of the 97 total
cleanup crew members. Laboratory tests showed no significant abnor-
malities in renal function tests, complete blood counts, or urinalyses.
Table 2. Abnormalities for 18 of 97 Cleanup Workers
Laboratory Test
Serum Glutamate
Oxalacetate Transaminase
Serum Alkaline Phosphatase
Serum Total Bilirubin
Serum Laclate Dehydrogenase
Abnormal Results
Normal Range Range No."
7-40 mU/ml 40-49
50-59
60-69
70-79
80-89
90-99
30-100 mU/ml 100-109
110-119
120-129
0.15-1.0mg/% 1.0-19
1 00-225 mU/ml 230-239
5
1
4
0
1
1
3
1
1
1"
1
"For individuals with more than one serial blood test, only the most abnormal result is tabulated
* Associated with a serum glutamate oxalacetate transammase result of 66
-------
42 Wastewater Aerosols and Disease/Contaminants
Several minimal-to-mild abnormalities did appear, however, in liver
function studies (Table 2). The abnormalities shown were distributed
among 18 (19%) of the 97 cleanup crew members; eight persons had
abnormalities on more than one occasion. Seven persons showed a rise
in serum glutamate oxalacetate transaminanse that seemed temporally
related to exposure to contaminated sewage; all of these persons also
had physical signs of mucous membrane irritation.
ENVIRONMENTAL FINDINGS
Table 3 shows the potentially toxic concentrations of HCCPD and
OCCP measured during cleanup of the plant's main interceptor sewer.
Only one laboratory abnormality (a total bilirubin of 1.4 mg/100 ml
serum) was noted among the 12 maximally equipped men involved in
this effort, indicating the protective value with respect to acute effects of
properly used safety equipment.
Table 3. Air Measurements in Main Interceptor Sewer May 3-28,1977
Concentration Data (ppb)
Chemical Type of sample No of samples Mean Median Range
HCCPD
HCCPD
OCCP
OCCP
P"
WA<>
P
WA
19
41
19
41
1,518
1,446
142
185
960
1,286
91
189
21-3,833
131-4,286
3- 472
17- 416
"Sample collected at external surface of worker wearing respirator
''Sample collected in work area on other than external surface of worker
DISCUSSION
In this study the wastewater treatment plant workers experienced
headache and mucous membrane, skin, and respiratory tract irritation
after they were exposed to vapors from sewage contaminated with in-
dustrial chemical wastes. Their symptoms were consistent with the
known toxic properties of HCCPD, and the distribution of symptoms
coincided in time and place with the distribution of HCCPD. Although it
was determined that HCCPD was the compound present in the highest
airborne concentration, OCCP, a related compound with relatively un-
known toxicity, was also present and may have contributed to symptom
production.
This episode as well as the Kepone and PCB incidents confirms the
fact that sewage workers already known to have increased exposure to
infectious agents (33-36) are also at risk of exposure to toxic nonviable
contaminants from wastewaters. As increasing volumes of chemically
complex industrial effluents are channeled each year through municipal
wastewater treatment plants, there will be an increasing potential for
both acute and chronic exposure of sewage workers to chemicals having
varied toxicologic characteristics. The acute effects from exposure may
be readily recognizable, but the effects of long-term, low-level exposure
are not known or at best only conjecture. The question of exposure to
nonviable contaminants and worker health deserves continuing
evaluation.
-------
John R. Kominsky 43
ACKNOWLEDGEMENTS
The author gratefully acknowledges the assistance of D.L. Morse,
M.D. (University of Rochester School of Medicine), C.L. Wisseman,
III, M.D. (Duke University School of Medicine), T.W. DeMunbrum,
M.D. (Louisville, Kentucky), and the more than 35 NIOSH people who
provided invaluable field or laboratory assistance. Special thanks are
offered to industrial hygienists R.L. Ruhe and G.L. White; physician M.
Singal; and chemists L.K. Lowry and C. Neumeister.
References
1. V. S. Environmental Protection Agency. 1976. Core activities of the office of toxic
substances (Draft Program Plan). EPA Publication 560/4-76-005. Office of Toxic Sub-
stances, Washington, D.C.
2. U. S. Environmental Protection Agency. 1977. Preliminary survey of toxic pollutants at
the Muskegon wastewater management system. Robert S. Kerr Research Laboratory,
RSK, ERL, Ada, Oklahoma.
3. U. S. Environmental Protection Agency. 1978. Contaminants associated with direct and
indirect reuse of municipal wastewater. EPA Publication 600/1-78-019. Health Re-
search Laboratory, Cincinnati, Ohio.
4. Blakeslee, P. A. 1973. Monitoring considerations for municipal wastewater effluent and
sludge application to the land. In: Proc. of the Joint Conference on Recycling Munici-
pal Sludges and Effluents on Land, Champaign, Illinois, July 9-13, 1973.
5. MyteUta, A. I. et al. 1973. Heavy metals in wastewater and treatment plant effluents.
Jour. Water Poll. Control Fed., 45:1859.
6. Wood, D. K., and G. Tchobanoglous. 1975. Trace elements in biological waste treat-
ment. Jour. Water Poll. Control Fed., 47:1933.
7. World Health Organization International Reference Center for Community Water Sup-
ply. 1975. Report of an international working meeting, health effects relating to direct
and indirect reuse of wastewater for human consumption. Technical Paper Series No.
7.
8. McCaUs, T. M., J. R. Peterson, and C. Lue-Hing. 1977. Properties of agricultural and
industrial wastes. In: Soils for Management of Organic Wastes and Wastewaters. Soil
Science Society of America, American Society of Agronomy, Crop Science Society of
America, Madison, Wisconsin.
9. Saleh, F. Y. 1976. Selected organic pesticides occurrence, transformations removal
from Dallas domestic wastewater. Ph.D. Dissertation. University of Texas at Dallas.
10. Glaze, W. H., and J. E. Henderson. 1975. Formation of organochlorine compounds
from the chlorination of a secondary effluent. Jour. Water Poll. Control Fed., 47:251.
11. Jones, R. A., and G. F. Lee. 1978. Chemical agents of potential health significance for
land disposal of municipal wastewater effluents and sludges. In: Proceedings of the
Conference on Risk Assessment and Health Effects of Land Application of Municipal
Wastewater and Sludge, B. P. Sagik and C. A. Sorber, eds. University of Texas at San
Antonio, pp. 27-60.
12. U. S. Environmental Protection Agency. 1977. Survey of two municipal wastewater
treatment plants for toxic substances. U.S. EPA Wastewater Research Division, Mu-
nicipal Environmental Research Laboratory, Cincinnati, Ohio.
13. U. S. Environmental Protection Agency. 1975. Suspect carcinogens in water supplies—-
Interim Report. Office of Research and Development, Washington, D.C.
14. SoMano, B. A., P. Bien, and P. Kwan. 1975. Airborne organo-mercury and elemental
mercury emissions with emphasis on central sewage facilities. Atmos. Environ.,
9:941.
15. Johnson, D. E., et al. 1978. Health implications of sewage treatment facilities. EPA
Publication 600/1-78-032. Health Effects Research Laboratory, Cincinnati, Ohio.
16. Mdamed, A., and C. SaUternik. 1970. Removal of nitrogen by ammonia emission trom
water surfaces. In: Developments in Water Quality Research, H. I. Schwal, ed. Ann
Arbor-Humphrey Science Publishers, Ann Arbor, Michigan.
17. Carnow, B., et a). 1979. Health effects of aerosols emitted from an activated sludge
plant. EPA Publication 600/1-79-019. Health Effects Research Laboratory, Cincinnati,
Ohio.
-------
44 Wastewater Aerosols and Disease/Contaminants
18. Huang, J. Y., G. E. Wilson, and T. Schroepfer. 1979. Evaluation of activated carbon
adsorption for sewer odor control. Jour. Water Poll. Control Fed., 51:1054.
19. Smith, R. P., and R. E. Grosselin. 1979. Hydrogen sulfide poisoning. J. Occup. Med.,
21:93.
20. Williams, H. I. 1958. Carbon dioxide poisoning: report of eight cases and two deaths.
Brit. Med. J., 2:1012.
21. Henderson, Y., and H. W. Haggard. 1943. Noxious Gases and the Principles of Respir-
ation Influencing Their Action. 2nd Ed. Reinhold Publishing Corp., New York, New
York.
22. Morse, D. L., J. R. Kominsky, C. L. Wisseman, and P. J. Landrigan. 1979. Occupa-
tional exposure to hexachlorocyclopentadiene: how safe is sewage? J. Amer. Med.
Assoc., 241:2177.
23. Clark, C. S., V. A. Majeti, and V. J. Elia. 1979. Urine screening of workers exposed to
toxic waste chemicals in a municipal wastewater treatment plant. In: Annual Report—
Center for the Study of the Human Environment. Department of Environmental
Health, University of Cincinnati, pp. 224-227.
24. Elia, V. J., C. S. Clark, and V. A. Majeti. 1979. Evaluation of worker exposure to
organic chemicals at municipal wastewater treatment facilities. Annual Report—Cen-
ter for the Study of the Human Environment. Department of Environmental Health,
University of Cincinnati, pp. 228-232.
25. Center lor Disease Control. 1978. Polychlormated biphenyl exposure—Indiana. Morb
and Mort. Wkly. Rpt. 27:99.
26. Raloff, J. 1976. The Kepone episode. Chem., 49:20.
27 Kominsky, J. R., and C. L. Wisseman. 1978. Morris Forman Wastewater Treatment
Plant. Technical Assistance Report No. TA 77-39. Hazard Evaluations and Technical
Assistance Branch, Division of Surveillance, Hazard Evaluations and Field Studies,
National Institute for Occupational Safety and Health, Cincinnati, Ohio.
28. Patty, F. A. 1963. Industrial Hygiene Toxicology. Volume II. Interscience Publishers,
New York pp. 1360-1361.
29 Treon, J. F., F. P. Cleveland, and J. Cappel. 1955. The toxicity of hexachlorocyclo-
pentadiene. A.M.A. Arch. Ind. Health, 11:459.
30. American Conference of Governmental Industrial Hygienists. 1978. Threshold Limit
Values for Chemical Substances and Physical Agents in the Workroom Environment
with Intended Changes for 1978. Cincinnati, Ohio.
31. Carter, M. R. 1977. The Louisville incident. In: 1977 National Conference on Com-
posting of Municipal Residues and Sludges. Information Transfer Inc., August 23-25,
1977.
32. Neumeister, C. E., and R. W. Kurimo. 1978. Determination of hexachlorocyclopenta-
diene and octachlorocyclopentene in air. Presented at the 1978 American Industrial
Hygiene Conference. Prepared by Measurements Support Branch, Division of Physi-
cal Sciences and Engineering, National Institute for Occupational Safety and Health,
Cincinnati, Ohio.
33. Clark, C. S., E. J. Cleary, G. M. Schiff, et al. 1976. Disease risk of occupational
exposure to sewage. J. Environ. Eng. Div., 102:375.
34. Clark, C. S., A. B. Bjornson, G. M. Schiff, J. P. Phair, et al. 1977. Sewage workers'
syndrome. Lancet, 1:1009.
35 Rylander, R., K. Anderson, L. -Belin, C. Berflund, et al. 1976. Sewage workers' syn-
drome. Lancet 2:478.
36. Dean, R. B. 1978. Assessment of disease rates among sewer workers in Copenhagen,
Denmark. EPA-600/1-78-007. Health Effects Research Laboratory, U. S. Environ-
mental Protection Agency, Cincinnati, Ohio.
DISCUSSION
MR. HAYMES: I am most interested in the prospects for followup.
MR. KOMINSKY: At this time NIOSH does not intend to conduct
any medical follow-up on the workers. Prior to leaving the site we out-
lined to the MSD a plan that should be used for medical monitoring of
these workers. We left the follow-up to MSD.
DR. BETTINGER: Regarding your closing conclusion about the po-
tential increasing exposure of workers in municipal treatment plants to
-------
John R. Kominsky 45
these chemicals in the future, the regulations for the Resource Conser-
vation and Recovery Act about to be promulgated, and the manufac-
turer notification discussion in Section Five of the Toxic Substances
Control Act, do you really think that in the future the industrial complex
will be allowed to widen groups of materials into treatment plants, as
you have suggested, or do you think, perhaps, this may be a diminishing
problem?
MR. KOMINSKY: I said accidental or unauthorized discharge. It
appears that we are having problems in sewage treatment plants con-
cerning worker health resulting from acute exposures to unauthorized
discharges. This is something that regulations cannot control. So I
would say that this must be a consideration in the future. But as far as
discharge of chemicals by industry on a daily basis in an uncontrolled
fashion, I would say it will not increase.
DR. WARD: What happened to the sewage during the time that the
plants were broken down? Did it go in the river?
MR. KOMINSKY: Correct. During the period of closure approxi-
mately 1 mgd of raw sewage was directed to the river. Fortunately,
because of the solubility characteristics of hexa, much hexa was not
leaving the contaminated sewer lines. But obviously EPA was monitor-
ing the river.
DR. WARD: I realize that not much can be done about this, nor is it
your job to do it when something like this happens. However it points
out some of the different risks that we are looking at, where, normally,
you are down to zero levels or close to that and then suddenly you are up
to levels that wipe out the advantages of anything you might have done
for the last 25 years.
MR. KOMINSKY: That is very true.
-------
46
A Model for Predicting Dispersion of
Microorganisms in Wastewater Aerosols
David E. Camann
Senior Research Analyst
Southwest Research Institute
Department of Environmental Sciences
P.O. Drawer28510
San Antonio, Texas 78284
ABSTRACT
A dispersion model framework for predicting the viable airborne concentrations of spe-
cific microorganisms dispersing from a nearby source of wastewater aerosols is presented.
Estimates and estimation procedures for key model parameters such as the viability decay
rate were developed from field monitoring data. In the specific model applicable to spray
irrigation, model parameters representing aerosolization efficiency and the initial aerosol
impact effect on microorganisms were also evaluated. The procedure for predicting down-
wind microorganism levels is illustrated using several examples.
Model validation using indicator organisms at two other spray irrigation sites implies the
model predictions have order-of-magnitude accuracy and precision within several hundred
meters of the source. The applicability of the model to estimating the dose of microorgan-
isms inhaled by humans in the vicinity of a wastewater aerosol source is considered.
Background
The study of man-made air pollution and chemical and biological war-
fare defenses has fostered the development in the last quarter century of
sophisticated mathematical models for describing the atmospheric diffu-
sion of inert gases and small particle aerosols (<20 |j.m in diameter).
These models are generally a cost-effective replacement of direct field
monitoring as a means of estimating pollutant aerosol concentrations
downwind from point sources. They also permit assessments of the
effects of new sources and of the effectiveness of possible control strat-
egies on existing sources. In these models, the pollutant concentration in
air at a distance downwind and along the centerline from a constantly
emitting pollutant source may be represented in the general form
Cd = Q«Dd + B (Equation 1)
as described in Figure 1.
For estimating short-term (averaging time <30 minutes) pollutant con-
centrations downwind of the source, the diffusion factor Dd is generally
expressed in the Gaussian form depicted in Figure 2. The Gaussian
model assumes that diffusion of pollutant from the point source during
its transport downwind leads to a Gaussian (i.e., normal) distribution of
the pollutant concentration in both the crosswind (y) and vertical (z)
directions about the downwind centerline (x-axis). Gaussian models
have been derived, parameterized, and popularized by Cramer (1-3),
-------
David E. Camann
47
where
Cd = Pa + B
Pd = Q-Dd
and d =downwind distance (m)
Cd=poHutant air concentration at d (mass/m3)
Pd = model prediction of pollutant air concentration conning from
the source (mass/m3)
B=background air concentration of pollutant (mass/m3)
Q=source strength (i.e., pollutant emission rate) (mass/sec)
Dd =drttusion factor at d (sec/m3)
Figure 1. General Form of Atmospheric Diffusion Models
(x, —y,z)
(x,-y,0)
Dd(y,z) =
2nuoyoz
where x = distance in downwind direction, (m)
y = distance in cross-wind direction, (m)
z = distance in vertical direction, (m)
u = mean wind speed, (m/sec)
o - standard deviation of plume concentration distribution in the crosswind
direction, (m)
oz = standard deviation of plume concentration distribution in the vertical
direction, (m)
H = height of plume center-line, (m)
Rgure 2. Gaussian Form of the Diffusion Factor Dd
-------
48 Wastewater Aerosols and Disease/Contaminants
Hay (4,5), Pasquill (6), Gifford (7), and Turner (8), among others (9).
Appropriate adjustments can be made to the basic model to account for
various phenomena when their effects become significant (8,10,11).
Such phenomena include plume rise, gravitational settling as a function
of particle size, pollutant decay with time, reflection and/or deposition
at horizontal mixing boundaries (such as the ground or a temperature
inversion), and precipitation scavenging (i.e., wash-out). Gaussian mod-
els have been validated (12,13), are recommended (14), and are currently
in wide use.
At downwind distances that have the same order of magnitude as the
dimensions of the aerosol source, the pollutant concentration pattern
due to atmospheric diffusion depends strongly on the configuration of
the aerosol source. Typical normalized isopleths of the diffusion factor
Dd of the Gaussian model are presented in Figure 3 for point, line, and
area sources of wastewater aerosols.
The dispersion of microorganisms in wastewater aerosols can also be
predicted using Gaussian models, provided factors are included to take
into account the die-off characteristics of the microorganisms. A biologi-
cal exponential decay factor e^3" is usually proposed (15,16) to account
for microorganism inactivation with increasing aerosol age due to envi-
ronmental stress (e.g., solar irradiation or dessication), where
ad= d/u = aerosol age (sec) at distance d, and
X. = viability decay rate of the microorganism, (sec-1) (\<0)
Viability decay rates have been estimated for various microorganisms
under various conditions in controlled chamber tests (17,18). An addi-
tional die-off effect I occurring immediately upon aerosolization of the
microorganisms has been observed (19). Its magnitude has been esti-
mated for the standard plate count of total viable bacterial particles from
a field study at a spray irrigation site (20). By incorporating these factors
into the Gaussian model to account for the observed die-off characteris-
tics of relevant groups of microorganisms, one obtains the microbiologi-
cal dispersion model.
THE MICROBIOLOGICAL DISPERSION MODEL
The microbiological dispersion model was originally developed (21) as
a model for microorganism dispersal in the wastewater aerosols pro-
duced when wastewater is applied to land by spray irrigation.* The
notation for representing the factors comprising the model has since
been revised (22) and generalized (23) for application to other sources of
wastewater aerosols.
General Form of Model
The general form of the microbiological dispersion model may be
represented as
Cd = Q'Dde*3* + B (Equation 2)
This general form can be used to predict microorganism concentrations
in the vicinity of sources which have aerosol formation processes too
*It is U.S. EPA policy to promote use of land treatment processes to reclaim and recycle
municipal wastewater. Slow rate application of wastewater to land by spray irrigation
(also termed sprinkler irrigation) is perhaps the most popular application method.
-------
David E. Camann
49
(a) POINT SOURCE:
-20
CROSSWIND DISTANCE (meters!
(b) LINE SOURCE:
1000
-500 -250
(c) AREA SOURCE:
I00 200
DISTANCE (m«ttnt
Figure 3. Diffusion Patterns Dd for Various Source Configurations
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50 Wastewater Aerosols and Disease/Contaminants
complex to postulate an estimable mathematical model for the source
strength Q. Various sewage treatment units, including aeration basins,
trickling filters and aerated surge basins, and cooling towers utilizing
wastewater are examples of wastewater aerosol sources for which the
general forms given by Equation 2 may be appropriate. For the general
form of the model, the source strength Q is usually estimated by field
sampling the wastewater aerosol just downwind of the source.
Spray Irrigation Form
For some processes of generating wastewater aerosols, the compo-
nents of a model of the aerosol-generating process can be estimated
separately. A more detailed form of the microbiological dispersion
model in which a suitable aerosol formation model replaces Q is then
preferable. Land application of wastewater by spray irrigation is one
such process.
The spray irrigation form of the microbiological dispersion model is
presented in Figure 4. Here the source strength Q is represented as the
product W«F»E»I of the wastewater concentration (W), the flow rate (F)
of wastewater being sprayed, the aerosolization efficiency (E), and the
initial microorganism impact (I). Substitution for Q in Equation 2 yields
a microbiological dispersion model for wastewater aerosols generated
by spray irrigation:
Cd = W»F-E-I»Dd»eXa« + B (Equation 3)
With suitable estimates of the model parameters (W, F, E, I, Dd, \ and
B), Equation 3 can be used to predict microorganism concentrations in
the vicinity of a spray irrigation site, with little or no requirement for
field sampling the wastewater aerosol at the site.
(a) GENERAL FORM:
Ca = Pd +B
where Pd =
(b) SPRAY IRRIGATION FORM:
Cd = Pd + B
where Pd = W-F-E-l-Da-e^o
Q =WF-E*I
W = microorganism concentration in the wastewater (cfu/L)
F = flow rate of wastewater being sprayed (L/sec)
E = aerosolization efficiency factor (i.e., the fraction of sprayed wastewater that becomes
aerosol) (O 0)
Figure 4. The Microbiological Dispersion Model
-------
David E. Camann 51
ESTIMATING THE PARAMETERS E, I, X, B, AND Q
The usefulness of the microbiological dispersion model is enhanced
because the values of the model parameters E, I, and X appear to be
relatively independent of the site at which the wastewater aerosol was
generated. The estimates of E, I, X, and B given in this section were
derived from five field sampling studies. The primary field study (22,24)
involving 77 aerosol runs was conducted by Southwest Research Insti-
tute at a sprinkler irrigation site in Pleasanton, California, that sprayed
1.4mgd (5.3 x 106 I/day) of unchlorinated secondarily-treated wastewa-
ter. Additional data were obtained from smaller field sampling studies of
two activated-sludge aeration basins [Egan Plant, Schaumburg, Illinois
(25,26) and Durham Plant, Tigard, Oregon (27,23)] and of two other
sprinkler irrigation systems [Fort Huachuca, Arizona (20,28) and Deer
Creek Lake State Park, Ohio (29)].
Aerosolization Efficiency E
In the spray irrigation studies, dye aerosol samples were collected
downwind after injecting a fluorescent dye into the wastewater. The
aerosolization efficiency E was determined as the ratio of the dye aero-
sol concentration sampled downwind to the diffusion model prediction
at that location calculated assuming all of the dyed wastewater had been
aerosolized. The estimates obtained for the proportion of wastewater
that was aerosolized during the spray irrigation are presented in Table 1.
The median estimate at each of the three sites was about 0.003 (i.e.,
0.3% of the sprayed wastewater evaporated before reaching the
ground). However, the estimates from individual dye runs varied by
over an order of magnitude, depending upon meteorological conditions
which affect the evaporative capability of the air. The regression equa-
tion shown in Figure 5 was developed from the Pleasanton data. Eighty
percent of the variation in aerosolization efficiency at Pleasanton can be
explained by this equation in which log E increases substantially with
the ambient temperature and slightly with the product of wind velocity
and solar radiation. This equation appears adequate to predict E for
spray sites using rotating impact sprinklers.* With a revised constant
based on several dye runs, modified equations could be developed for
other types of sprinkler equipment.
Table 1. Estimates of Aerosolization Efficiency E
Distribution of E values (percentites)
Site of spray irrigation
Pleasanton, CA
Fort Huachuca, AZ
Deer Creek Lake, OH
No of dye runs 10%
17 0.09%
3
4
25% 50%
(median)
0.19% 0.33%
0.29%
0.47%
75%
0.64%
90%
1.8%
'Rotating sprinklers with Rainbird® impact nozzles were used at all three spray irrigation
sites.
-------
52 Wastewater Aerosols and Disease/Contaminants
LogIOE = 0.0311 + 0.000096 u • r - 3 10
where t — air temperature, °C
u = wind speed, m/sec
r = solar radiation, W/m2
FP = 0.80
Figure 5. Prediction Equation for E at Pleasanton
Microorganism Impact I
The pattern of die-off of a microorganism with distance during an
aerosol run, after accounting for aerosolization efficiency, was used to
estimate the microorganism impact I and the viability decay rate X. of the
microorganism during the run. I and \ were estimated from the intercept
and slope parameters, respectively, of the simple linear regression of the
log concentration pattern In (w.'p.E'Dd) on aerosol age (22).
The distributions of the impact estimates obtained for each microor-
ganism from the Pleasanton data are presented in Table 2. Preliminary
analysis (22) suggested reduced initial survival (i.e., low I values) may
be associated with low relative humidity, high wind velocity, and a large
temperature difference between the wastewater and the air, but no defi-
nite relationship has yet been established. From the differences in their I
value distributions, it is apparent that microorganisms vary markedly in
their ability to survive the initial shock of aerosolization.
Table 2. Estimates of Microorganism Impact I at Pleasanton
No. of
Distribution of I values (percentiles)
aerosol runs 10%
Fecal coliforms
Total cdiforms
Standard plate count
Coliphage
Mycobacterta
Ctostrkfum perfnngens
Fecal streptococci
Pseudomonas
Enteroviruses
13
44
33
43
8
11
31
13
2
0.016
0.036
0.017
0.27
25%
0.068
0.060
0.11
0.094
077
024
0.71
1.7
40%
0.13
0.19
0.18
0.97
50%
(median)
0.13
0.16
021
0.34
0.89
1.2
1.7
14
40°
60%
0.23
0.24
0.52
2.7
75%
0.58
0.55
0.35
091
2.1
6.5
6.1
73
90%
1.1
1.2
1.8
32
"Approximate value
Viability Decay Rate \
Table 3 gives the distributions of viability decay rates for each mi-
croorganism derived from the Pleasanton data. Frequently, microorgan-
ism die-off with aerosol age could not be detected (\ = «) at Pleasanton,
especially for such hardy microorganisms as fecal streptococci, Pseudo-
monas, and mycobacteria. Preliminary analysis (22) implied viability
decay may be more rapid with high solar radiation, high temperatures,
and middle-to-low relative humidities, but no definite relationship has
been established.
The distribution of viability decay rates for the Pleasanton spray irri-
gation system were compared (23) to the limited distributions obtained
-------
David E. Camann
53
from sampling the Durham aeration basin (Table 4). At the 0.10 signifi-
cance level, no significant \ differences were found between sites for
any microorganism by the two-sample Kolmogrov-Smirnov test (30) of
distributional differences or by the signed ranks test (31) of shifts in
location. The inability to detect a significant difference may be due to the
variability in X and limited number of X estimates (six per microorgan-
ism) available for the Durham site.
Table 3. Estimates of Viability Decay Rate \ at Pleasanton
No. of
Distribution of A. (sec-1) values (percentites)
aerosol runs 10%
Total conforms
Fecal coliforms
Cdiphage
Ctostridium perfringens
Standard plate count
Mycobacteria
Pseudomonas
Fecal streptococci
44
13
43
11
33
8
13
31
-0.23
-0.19
-0.11
-0.10
-0.12
-0.15C
-0.08
-0.06
25%
-0.094
-0.070
-0.051
-0.039
-0.020
-0.009b
-0.00&
-0.006"
40% 50% 60% 75% 90%
(median)
-0.050 -0.032 -0.020 -0.004 «
-0.023
-0.029 -0.011
-0.004b
-0.006 -0.004*
a
a
a
a
a a a a
" Indeterminate viability decay rate; for model calculations,
6 Questionable value, perhaps indistinguishable from zero
1 Approximate value (extrapolated)
1 may be presumed to represent the value 0.0
Background Concentration B
The standard procedure for estimating the background air concentra-
tion of a microorganism in a wastewater aerosol monitoring study is to
take samples upwind of the aerosol source simultaneously with samples
taken downwind during an aerosol run. B may then be computed as the
geometric mean of the upwind concentration values over all the aerosol
runs performed. Using this approach, background concentrations of
prevalent and relevant microorganisms were computed from the various
field monitoring studies and are presented in Table 5. There is consider-
able variation in the background concentration from site to site as shown
by the geometric means in Table 5. However, there also is substantial
variation in the measured upwind concentration from one run to another
at the same site. Ambient background concentrations of potentially
pathogenic microorganisms are difficult to establish accurately because
they are usually below the lower detection limit of any sampling-assay
protocol available for the aerosol monitoring effort.
Table 4. Comparison of Viability Decay Rates at Two Sites
Viability decay rate \(sec-») —25th percentile
Total coliforms
Coliphage
Mycobacteria
Fecal streptococci
Pleasanton
spray irrigation
-0.094
-0.051
-0.009
-0.008
Durham, OR
Sewage Treatment Plant
(6 aerosol runs)
-0.06
-0.05
-0.06
-0.05
Significant
difference?
No
No
No
No
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54 Wastewater Aerosols and Disease/Contaminants
Table 5. Background Concentrations B at Various Sites
Geometric mean background concentration0 (cfu/m3)
Spray Irrigation sites Sewage Treatment Plants
Pteasanton Ft. Huachuca Deer Creek Egan, Chicago Durham, OR
Standard plate count
Total colitorms
Fecal conforms
Coliphage (pfu)
Fecal streptococci
Mycobacteria
Pseudomonas
460
01
0.02
0.01
0.2
02
3
41 89
1.3 —
— —
— —
— —
— —
— —
2,100
0.6
0.1
0.01
<1
—
<2
<0.01
—
<0.02
0.03
<0.01
<2
" "Background" measurements taken at upwind locations during aerosol runs
Source Strength Q
Practical difficulties usually make it impossible to estimate the source
strength Q in the general form of the microbiological dispersion model
by field sampling the microorganism concentration C0 of the wastewater
aerosol right at its source. In these situations, Q and X can be estimated
by field sampling the wastewater aerosol simultaneously at two dis-
tances di and d2 downwind of the source. The two downwind sampling
distances should be sufficiently close to the source that the sampled
microorganism air concentrations Ci and €2 both clearly exceed the
background concentration B. However di and d2 must also be suffi-
ciently separated that their aerosol ages ai and a2 are substantially dif-
ferent. When these conditions are met, a point estimate of the viability
decay rate \ for the field sampling run can be obtained by evaluating
Equation 2 at the two sampled distances:
= ln[(CI-B)/DI]-ln[(C.-B)/DJ
The \ point estimate determined from Equation 4 may disguise consid-
erable uncertainty in the estimate, particularly if ai - a2 is small, if Ci or
Cz are not appreciably greater than B, or if the uncertainties in (Ci-B)/
DI or (C2-B)/D2 are relatively large. The X. estimate from Equation 4
should be compared to the microorganism's A. distribution given in Table
3 to determine whether the X. point estimate appears realistic. Because
of the uncertainty in its value, the X. estimate from equation 4 will often
be inadequate for predicting microorganism aerosol concentrations at
downwind distances much greater than the sampled distances.
The source strength Q and the air concentration C0 of microorganisms
at the source that survived aerosolization can be estimated for this sam-
pling run using the \ estimate:
Q = ( Clp'i B ) e-** (Equations)
C0 = B + QD0 (Equation 6)
The accuracy of the source air concentration estimate may suffer
because complex source geometry and source turbulence often make it
difficult to accurately estimate the diffusion factor at the source (i.e., D0)
and at small downwind distances.
-------
David E. Camann 55
CONCENTRATION PREDICTIONS USING THE MODEL
Spray Irrigation Model
Calculation Procedure
The following steps comprise the procedure for applying the spray
irrigation form of the microbiological dispersion model (Equation 3) to
predict aerosol concentrations in the vicinity of a spray irrigation site:
1. Choose the centerline downwind distance and weather conditions to
be evaluated. Calculate the aerosol age ad at distance d.
2. Select a relevant microorganism and measure its typical concentra-
tion W in the wastewater before it becomes aerosolized. W should be
determined as the geometric mean of assays for the microorganism
from several samples of the wastewater.
3. Determine the total flow rate F of wastewater being applied to land
through the spray irrigation system; F is usually measured at the
pump.
4. Estimate the background concentration B of the microorganism in
the air.
5. Apply a suitable air pollutant dispersion model to calculate Dj based
on such site-specific information as the configuration of the aerosol
source(s), weather conditions, local topography, and distance to the
downwind location.
6. Select an aerosolization efficiency value E appropriate for the type of
spray system, operating spray pressure, and weather conditions, per-
haps by using the equation in Figure 5.
7. Select appropriate values of I and X. for the microorganism, consider-
ing the weather conditions. In the absence of established weather
relations, percentiles in Tables 2 and 3 ranging from the 25th percen-
tile to the 75th percentile may be chosen: the 25th percentile for very
adverse conditions (high solar radiation, perhaps), the 50th percentile
for typical conditions, and the 75th percentile for very favorable
conditions (warm, humid nights, perhaps).
8. Calculate the predicted centerline air concentration Pd at distance d
produced by the aerosol source(s) and the downwind air concentra-
tion Cd by using Equation 3.
Prediction Example—Pleasanton Residential Area
As an example of the calculation procedure, the spray irrigation
model was used to make rough estimates of the aerosol concentrations
of total coliforms, mycobacteria, and human enteroviruses to which the
nearest residents to the spray fields in Pleasanton, California were typi-
cally exposed during summer. These residents lived in a subdivision, the
closest edge of which was located about 650 east and southeast of the
edge of the spray fields.
Two cases were considered: 1) nighttime (perhaps corresponding to
maximal exposed concentration when downwind); and 2) midday (per-
haps corresponding to the minimal exposed concentration when down-
wind). The meteorological conditions and site layout used as model
inputs for both cases are presented in Table 6. Sample computations for
total coliforms and enteroviruses at night are provided in Table 7 show-
ing the model parameter values obtained using the preceding calculation
-------
56
Wastewater Aerosols and Disease/Contaminants
Table 6. Meterological Conditions and Site Layout for Spray Irrigation
Prediction Examples
Meteorological Conditions
Summer night
Summer midday
Air temperature, t
Relative humidity
Solar radiation, r
Wind velocity, u
Stability class
Mixing height
Site Layout
Sprinkler type
Sprinkler configuration
Number of sprinklers
Inhabited area
Direction of sprinklers
Distance from edge of sprinklers, d
Aerosol age, a (summer night)
Aerosol age, a (summer midday)
20°C
70%
OW/m2
2m/sec
E
30m
Pleasanton, CA
Rainbird0 impact
Line-Fig. 3(b)
52
Subdivision
EandSE
650m
325 sec
162.5 sec
30°C
40%
LOOOW/m2
4m/sec
B
High
Deer Creek Lake, OH
Rainbird® impact
Rectangular grid-Fig. 3(c)
96
Campsite
NE
700m
350 sec
175 sec
procedure. In the absence of predictive relationships for I and X, the
60th percentile of the I and X distributions was chosen as appropriate for
the nighttime case; the 40th percentile was selected for the midday case.
With aerosol ages as large as in these examples, the exponential decay
term e^ad based on an uncertain X value often predominates the calcula-
tion. Hence, the predicted concentration Pa may disguise substantial
uncertainty as to its proper value.
In Table 8, the resulting model predictions of the centerline concen-
tration are compared to the background concentrations B measured at
Pleasanton. For total coliforms and mycobacteria, the model-predicted
concentrations entering the residential area are less than the measured
background concentrations, even during the nighttime case. The model
Table 7. Examples of the Spray Irrigation Model Calculation Procedure:
Approximate Concentrations in Inhabited Area When Down-
wind on a Summer Night
Site/inhabited area:
Microorganism group:
Model parameters
W
F
E
F
x°
Pd = W-F-E.|.Dd.eA.a
B
Cd = Pd -t- B
Pleasanton, CA subdivision
Total coliforms Enteroviruses
10,000,000 cfu/l
70 I/sec
0.0033
0.23
0.00001 7 sec/m3
-0.02 sec-1
« 0.01 cfu/m3
0.1 cfu/m3
0.1 cfu/m3
50pfu/l
70 I/sec
0.0033
60"
0.00001 7 sec/m3
-0.002^ sec-1
0.006 pfu/m3
0. cpfu/m3
0.006 pfu/m3
Deer Creek Lake, OH
campsite
Total coliforms
180,000 cfu/l
30 I/sec
0.0047
0.23
0.00002 sec/m3
-0.02 sec-1
0.0001 cfu/m3
0.1C cfu/m3
Ocfu/m3
' 60th percentile selected for these meteorological conditions
' Extrapolated value
- Little basis for a numerical estimate
-------
David E. Caniann 57
Table 8. Summary of Approximate Predicted Centerline and Back-
ground Concentrations in Spray Irrigation Examples
Pteasanton, CA Subdivision
Total coliforms (cfu/m3)
Mycobactena (cfu/m3)
Enteroviruses (pfu/m3)
Deer Creek Lake, OH campsite
Total conforms (cfu/m3)
Fecal streptococci (cfu/m3)
Summer night
0.01
0.09
0.006
0.0001
0.005
Pd
Summer midday
0.001
0.06
0.002
7x10-"
0.0009
B
Background
0.1
0.2
0.1°
0.2°
"Little basis for a numerical estimate
predictions suggest that, at these residential distances, the downwind air
concentrations of hardy but relatively rare wastewater microorganisms
such as the enteroviruses may equal or exceed those of prevalent waste-
water indicator microorganisms such as total and fecal coliforms.
Prediction Example—Deer Creek Lake Campsite
As another example, rough estimates were also made of the microor-
ganism levels to which campers are exposed in the summer at a campsite
located a minimum of 700 m northeast of a wastewater spray irrigation
site at Deer Creek Lake, Ohio. Both a nighttime and a midday case were
considered using the meteorological conditions and site layout listed in
Table 6 as model inputs. A sample computation for total coliforms at
night is presented in Table 7. The approximate centerline concentrations
of total coliforms and fecal streptococci predicted to be entering the
campsite when it is downwind of the spray field are summarized in Table
8. Because the aerosol ages are relatively large, the computed value of
Pd may hide the considerable uncertainty as to its actual value. Notice
that the predicted exposure concentrations from the wastewater spray
source are considerably less than the presumed background concentra-
tions surmised from the field monitoring at Pleasanton (Table 5).
General Form of Model Supplemented by Field Sampling
Calculation Procedure (Two Downwind Sampler Distances)
The distribution of microorganism concentrations near any wastewa-
ter aerosol source can be predicted using the following procedure. A
limited field sampling program is necessary. It should consist of several
sampling runs involving simultaneous air samples taken upwind and at
two (preferably three or more) separated downwind distances. Each
sampling run provides an estimate of X, Q, and a downwind concentra-
tion prediction Pd. However, Pd depends largely on X for downwind
distances larger than the sampled distances, and the estimate of \ may
be very imprecise. Thus, this procedure is not recommended for predict-
ing the distribution of Pd at large downwind distances. The procedure is
as follows:
-------
58 Wastewater Aerosols and Disease/Contaminants
1. Choose the centerline downwind distance d, the relevant microorgan-
ism^), and the general weather conditions to be evaluated.
2. Conduct several field sampling runs for the relevant microorgan-
ism^) under the chosen weather conditions. During each sampling
run, the microorganisms' air concentrations should be simulta-
neously monitored upwind and at two (or more) separated but rela-
tively short downwind distances di and d2 from the wastewater aero-
sol source.
3. Estimate the background concentration B for each microorganism
during each run from the upwind samples.
4. Determine the measured downwind concentrations Ci and C2 of each
microorganism and the aerosol ages ai and a2 at the downwind sam-
pler distances.
5. Apply an appropriate air pollutant dispersion model to calculate D1;
D2, and Da, based on such site-specific information as the configura-
tion of the aerosol source, the weather conditions, local topography,
the downwind sampler distances dt and d2, and the downwind dis-
tance d of the prediction.
6. Compare the microorganism viability decay rate X during the sam-
pling run as computed from Equation 4 with the X. distribution of the
microorganism shown in Table 3. Select an appropriate estimate for
\based on the available information.
7. Estimate the source strength Q during the sampling run from Equa-
tion 5.
8. Calculate the predicted air concentration Pd emanating from the aero-
sol source to the centerline distance d during the sampling run, and
the total air concentration there (Cd) using Equation 2.
Prediction Example—Durham Elementary School
To illustrate the calculation procedure for the general form of the
microbiological dispersion model, an example is given for an aeration
basin. The model was used to make very rough estimates of the aerosol
concentrations of mycobacteria and other bacteria to which children
may have been exposed while attending an elementary school located
about 450 m northeast of the aeration basin of the Durham Wastewater
Treatment Plant, Tigard, Oregon. When the school was downwind of
the aeration basin,the days were cool and often rainy. Table 9 displays
the calculation procedure for predicting the mycobacteria aerosol con-
centration at 450 m downwind during one field sampling run performed
under cool humid conditions. The distribution from the six aerosol runs
of predicted aerosol concentrations of total coliforms, mycobacteria,
and fecal streptococci at the distance of the school downwind is con-
trasted with the background concentration in Table 10. There is broad
variation in the predicted concentrations of each microorganism at the
school distance. For relatively large aerosol ages the exponential factor
e\a,, predominates the Pd calculation. Consequently, the considerable
uncertainties in the point estimates X. from Equation 4 are magnified in
the calculation of Pd for sizable downwind distances.
-------
David E. Camann 59
Table 9. Example of Calculation Procedure for General Form of Model
Supplemented by Field Sampling
Site layout
Wastewater Aerosol Source Aeration Basin
Inhabited Area Elementary School
Direction from Source NE
Distance from Source, d 450m
General Weather Conditions Cool Days, Often Rainy
Relevant Microorganism Myoobactena
Field Sampling Run
Date 3-9-78
Time 1040-1110
Air Temperature 10°C
Relative Humidity 65%
Cloud Cover in Eighths 5
Solar Radiation 98W/m2
Mean Wind Speed, u 2.1 m/sec
Mean Wind Direction 15°
Wind Direction Range 310° to 50°
Background Air Concentration, B <0.01 cfu/m3
Locations: Sampler 1 Sampler 2 Prediction
Distances, d dt=37m d2=82m d=450m
Aerosol Ages, a a,=18sec 32=39sec ad=214sec
Diffusion Factors, D D,= 0.0073 sec/m3 Ds= 0.0025 sec/m3 Dd= 0.00024 sec/m3
Sampled Air Concentrations, C C,= 9.3 cfu/m3 C,= 1.3 cfu/m3
Viability Decay Rate,X.(eq. 4) -0.040 sec-1
Source Strength, O. (eq. 5) 610 ctu/sec
Pd = 6'D,je tad 0.00003 cfu/m3
Cd = Pd + B <0.01 cfu/m3
VALIDITY OF SPRAY IRRIGATION MODEL
PREDICTIONS NEAR THE SOURCE
The predictive value of the spray irrigation model has been investi-
gated through a validation study (22) in which model-predicted aerosol
concentrations were compared against field-sampled downwind aerosol
concentrations corrected for the background concentration.
Validation Procedure
Sampled aerosol data were taken from the field studies at Deer Creek
Lake and Fort Huachuca and from the Pleasanton runs not used in
developing the model. Predictions were made for each sampler distance
Table 10. Distribution of Model Predictions at School Distance from
Durham Aeration Basin
Total conforms (cfu/m3)
Mycobacteria (cfu/m3)
Fecal streptococci (cfu/m3)
25%
5x10-7
2x10-"
2x10-6
P4SO
50%
5x10-5
4x10-5
3x10-4
75%
0.002
0.2
0.03
B
Background
<0.01
<0.01
0.03
-------
60 Wastewater Aerosols and Disease/Contaminants
Table 11. Validation Data for Spray Irrigation Model
Number of pairs of predicted (Pd) and measured (Cd-B) values
Standard plate count
Total conforms
Fecal coliforms
Cdiphage
Fecal streptococci
Pleasanton
6
8
5
5
8
Ft. Huachuca
45
24
1
15 (seeded)
0
Deer Creek
34
0
0
0
0
Total
85
32
6
20
8
during each run using the calculation procedure described above for the
spray irrigation model. The amount of validation data is shown in Table
11. Enough field data were available to thoroughly test the model predic-
tions for the standard plate count within 200 m of the wastewater spray
source, when a variety of sampling and analytical procedures were used.
Useful evaluations were obtained for total coliforms and coliphage
nearer the source. However, the predictive ability of the model for
potentially pathogenic microorganisms remains untested at sites other
than Pleasanton.
Because most of the field data utilized were obtained within 50 m of
the spray source, this model validation emphasizes the adequacy of the
model parameters E and I rather than X. Since the estimates of X vary
widely, both the accuracy and precision of the model predictions are
likely to deteriorate with distance from the spray source.
Accuracy
The ratio of the predicted to the measured concentration, Pd/ (Cd-B),
was used to evaluate prediction accuracy. Predictions of the model were
quite accurate when the sprayed wastewater did not contain residual
chlorine, as Table 12 indicates. The predictions Pa for most microorgan-
isms tended to be slightly smaller than the net measured aerosol concen-
trations (Cd-B), averaging 64% of the net measured value for standard
plate count and 73% for total coliforms and coliphage. The total coli-
form and coliphage predictions exhibited no significant bias. While the
prediction underestimates for standard plate count, and fecal coliforms
are statistically detectable, their small magnitude (i.e., about a factor of
Table 12. Accuracy of Spray Irrigation Model Predictions Near the
Source
Predicted/measured Assessment of
geometric mean prediction bias
Total coWor ms 0.73 Unbiased
Coliphage 0.73 Unbiased
Standard plate count 0.64 Slight underpredidion
Fecal coliforms 0.40 Slight underprediction
Fecal streptococci 4.2 Unknown
-------
David E. Camann 61
Table 13. Spray Irrigation Model Underprediction of Standard Plate
Count for Chlorinated Wastewater Aerosols
High chlorinatkxi
Lowchlorination
Unchlorinated
Total residual chlorine
6ppm
0.2 ppm
<0.1 ppm
Predicted/measured
geometric mean
0.006"
0.55
0.76
0 Approximate value
2) is insignificant in most model applications. As Table 13 illustrates,
model predictions substantially underestimated the net measured aero-
sol concentrations of the standard plate count when the sprayed waste-
water contained high levels of residual chlorine.
Table 14. Precision of Spray Irrigation Model Predictions Near the
Source
Discrepancy between predicted
and measured values
Factor Percentage below
geometric mean a factor of 5
Standard plate count 2.7 77
Coliphage 2.9 80
Total coliforms 4.4 71
Fecal conforms 4.9 71
Fecal streptococci 4.9 60
Precision
The discrepancy factor, defined as the larger of (Cd-B)/Pd and P
-------
62 Wastewater Aerosols and Disease/Contaminants
Applicability of Model Predictions
Spray Irrigation Form
The preceding validation study suggests that the spray irrigation
model may be used to predict outdoor microorganism aerosol concentra-
tions near land application systems which use rotating impact sprinklers
to apply wastewater that contains no residual chlorine. When the waste-
water has a low level of residual chlorine (0.1 to 0.4 mg/1), the model
predictions appear to be valid for the standard plate count of aerobic and
facultative anaerobic heterotrophic bacteria; presumably they are also
valid for the hardier individual microorganisms. With present microbiol-
ogical aerosol sampling and assay methods, it is generally impractical to
sample wastewater aerosols for microorganisms beyond 100 or 200 m
from their source. It appears that the spray irrigation model can be used
to estimate the aerosol levels of specific pathogens and the traditional
indicators to downwind distances of perhaps 400 to 1,000 m from the
wastewater spray source, depending upon the precision required in a
given application.
As Tables 6, 7, and 8 illustrate, one application of this model is to
predict the concentration of potential pathogens inhaled by irrigation
workers and residents in the vicinity of wastewater irrigation sites that
use sprinklers. Determination of the microorganism doses which sub-
jects inhale (or are otherwise exposed to) during epidemiological studies
of the health effects of wastewater aerosols is an application of particu-
lar relevance to this symposium; it is discussed further below. Another
potential application is to evaluate the public health risks posed by exist-
ing and planned land application systems which use sprinklers, relative
to those risks posed by other methods of wastewater treatment.
General Form of Model
As Tables 9 and 10 illustrate, the general form of the microbiological
dispersion model can be used in combination with limited field sampling
programs to predict the distribution of downwind concentrations ema-
nating from other sources of aerosolized microorganisms. These
sources include the aeration basins and trickling filters of sewage treat-
ment plants and the cooling towers that circulate municipal wastewater.
However, the uncertainties associated with the viability decay rates
estimated during the field sampling runs may preclude obtaining realistic
model predictions when extrapolating beyond 200 to 500 m from the
source.
Factors Limiting Model Applicability
The Viability Decay Rate X
Distance limitations must be placed on the model predictions primar-
ily because of uncertainty regarding the proper viability decay rate. For
rapid viability decay rates and/or for large aerosol ages, the exponential
decay term predominates the model calculation of the predicted down-
wind concentration. To obtain reliable and measurable microorganism
aerosol concentrations, field sampling runs to estimate the viability de-
cay rate must be performed so close to the source that only a limited
span of aerosol ages can be sampled. Consequently, field sampling can-
-------
David E. Camaiui 63
not detect slow viability decay, and field measurement uncertainties
may exaggerate estimates of rapid viability decay. This contributes to
the wide distribution of viability decay rates presented in Table 3 and the
erratic point estimates obtained using Equation 4. For this reason, only
the middle of the viability decay rate distributions given in Table 3 can
be recommended for making downwind predictions using the microbiol-
ogical dispersion model.
Laboratory studies using controlled aerosol chambers can provide
more precise and repeatable estimates of bacterial and viral viability
decay than can field studies. However, laboratory estimates of viability
decay may not be applicable to predictions in the field. The enclosed air
traditionally employed in controlled chamber tests in the laboratory pro-
duces much slower viability decay in both bacteria (32,33) and viruses
(34) than does ordinary outside air. Air pollutants [perhaps the gaseous
ozone-hydrocarbon complexes found in smog (35,36)] may cause these
bactericidal and viricidal effects. The viability decay rates which Ben-
bough and Hood (34) obtained by exposing laboratory strains to outdoor
air for one hour were:
E. coll MRE 162: -0.00005 sec"1 to -0.0008 sec"1
Tl coliphage: -0.0002 sec"1
T7 coliphage: -0.0003 sec"1 to -0.0005 sec"1
Semliki Forest arbovirus: -0.0002 see"1 to -0.0003 sec-1
The microorganisms were shaded from direct sunlight in ambient air
at relative humidities between 75 and 96% and at temperatures between
2° and 12°C. Even these viability decay rates for open air are much less
rapid than the corresponding coliform and coliphage rates obtained from
the Pleasanton field study (see Table 3). This may reflect the environ-
mental conditions at Pleasanton which were in many respects more
hostile to microorganism survival: solar radiation middle-range relative
humidity, generally higher temperature, and wastewater as the pre-aero-
solization medium. However, the wide day-to-day variation in the via-
bility decay rates of total coliforms and fecal coliforms at Pleasanton is
in agreement with the wide day-to-day variation in E. coll viability decay
reported by Benbough and Hood.
Selecting Values of I and X
A reliable procedure is needed for selecting values of the model para-
meters I and X when predicting microorganism aerosol concentrations
using the spray irrigation model. There are preliminary indications in the
Pleasanton data supported by considerable published data (37, 19, 38)
that the I and X values for a microorganism depend upon ambient atmos-
pheric conditions such as relative humidity (19), ultraviolet solar radia-
tion, and temperature (18). A multivariate regression analysis should be
conducted to investigate the relationship of I and X to measured environ-
mental variables such as air temperature, relative humidity, solar radia-
tion, wind speed, air pollutant indices, and wastewater total suspended
solids and total organic carbon. If reasonable and consistent predictive
regression equations could be developed for at least some of the moni-
tored microorganisms, the predictive ability of the spray irrigation
model at moderate downwind distances would be enhanced.
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64 Wastewater Aerosols and Disease/Contaminants
Insights from the I and \ Estimates
The distributions of values of the microbiological parameters I and
X. of the model provide insights regarding the monitored microorgan-
isms that are relevant to applied environmental and public health
microbiology.
The microorganism impact factor I was intended to represent the
fraction of microorganisms that, having entered the aerosol state, sur-
vive the shock of aerosolization. Impact factors exceeding 1.0 were not
anticipated because such high I values would suggest that more microor-
ganisms survived than the total that were aerosolized. However, perusal
of Table 2 reveals that I values above 1.0 frequently occurred. These
data suggest that high I values are characteristic of most of the potential
pathogens studied at Pleasanton and that I measures additional effects
beside initial survival through the aerosolization process. The mechani-
cal splitting of clumped microorganisms into multiple colony-forming
units during the processes of aerosolization or sampling is one additional
effect which might also be measured by I (21, 19). Underestimation of
the pathogen concentrations in wastewater is another possibility (21).
Several other less likely possibilities have also been proposed (22).
Comparing the microorganism impact and viability decay values of
the different microorganisms indicates their relative ability to survive
wastewater aerosolization. By comparing a fixed mid-range percentile
(e.g., the 50th percentiles of the microorganism I distributions in Table 2
or the 25th percentiles of the micorganism \ distributions in Table 3), it
can be seen that some microorganisms are much hardier than others.
The indicator microorganisms commonly used to indicate wastewater
pathogenicity (i.e., total coliforms, fecal coliforms, the standard plate
count, and coliphage) do not survive wastewater aerosolization nearly
as well as do most of the potential pathogens studied (especially human
enteroviruses, Pseudomonas, and fecal streptococci). Thus, the tradi-
tional "microbiological wastewater indicators," especially total coli-
forms and fecal coliforms, are actually very poor indicators of the path-
ogenic hazard posed by wastewater aerosols. The use of most of the
traditional indicator organisms in field studies to monitor wastewater
aerosols may result in unrealistically low estimates of the aerosol levels
of potential pathogens.
On the other hand, fecal streptococci may be a better indicator for
wastewater aerosol monitoring (39) due to the relative ease of their
assay, their prevalence in wastewater, and their survival through waste-
water aerosolization and in the aerosol state. However, because fecal
streptococci are frequently present at variable levels in background aer-
osol samples, the detection of low levels of aerosolized fecal strepto-
cocci downwind does not necessarily implicate the investigated waste-
water aerosol as the source of the sampled fecal streptococci.
Use of the Model to Estimate Human Exposure to Wastewater
Aerosol Microorganisms
The process by which the viable airborne microorganisms in wastewa-
ter aerosols are inhaled and initiate infection may involve as many varia-
bles (40,41) as does the aerosolization and transport process. The dose
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David E. Camann 65
of viable microorganisms that are inhaled can be estimated using the
microbiological dispersion model as outlined below. However, the limi-
tations of dose estimation should be recognized so that calculated in-
haled doses are given suitably modest interpretations.
Inhaled Dose
The dose of a specific airborne microorganism from a wastewater
aerosol source that is inhaled by a person in the vicinity during the time
interval t = to to t = ti, may be estimated from an integral (16):
Inhaled Dose = f ' P (t) (Breathing Rate) dt, (Equation 7)
provided the microbiological dispersion model prediction P(t) follows
the person's movement throughout the time interval (i.e. P(t) is the
predicted air concentration at the person's location at time t).
Examples of a simplified calculation of the approximate highest daily
dose inhaled in a year by children attending the school next to the
Durham plant are given in another symposium paper (27).
Limitations of the Dose Estimate
It would be desirable to calculate the dose of the specific agent re-
sponsible for the illness or infection being investigated. However, per-
centiles of the model parameters I and \ are available only for the
groups of microorganisms shown in Tables 2 and 3. For example, if
seroconversion to Echovirus 29 were occurring in the nearby popula-
tion, one could only use the I value for the entire group of enteroviruses
and would be forced to guess a value for\. Furthermore, there are
analytical difficulties in determining the concentration W of a specific
agent in wastewater (42). Consequently, the dose estimates will gener-
ally apply to a group of microorganisms which includes the specific
agent of interest.
It is difficult to calculate P(t) accurately. The limitations of the micro-
biological dispersion model predictions are discussed above. In addi-
tion, a person is a very mobile receptor. His path of movement during
the period under investigation is often impossible to reconstruct and is
difficult even to characterize, unless he has kept an hourly log or daily
diary of his activities. Another complication, usually of lesser signifi-
cance, is temporal variation in the wastewater aerosol source strength
due either to periodic operation or to diurnal fluctuations of the source.
Most people spend the majority of their time indoors. This simplifies
the "mobile receptor" problem, but introduces another. The parameters
of the microbiological dispersion model are based on field studies of
outdoor aerosol concentrations; its predictions are presumably applica-
ble to exposure outdoors rather than indoors. In some situations, indoor
doses may approximate outdoor doses. Spendlove (43) found that the
aerosol dose of a hardy microorganism received by inhabitants within a
single-story residential dwelling without airconditioning is essentially
the same as outside the building, presumably when the outdoor concen-
tration is high and relatively constant over time periods exceeding 1
hour.
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66 Wastewater Aerosols and Disease/Contaminants
When inhaled, the size of a microorganism-laden aerosol particle af-
fects the depth of its penetration into the respiratory tract (40). Depth of
penetration influences the likelihood of infection. Field sampling studies
of wastewater aerosols (29, 20) have shown that the majority of particles
containing microorganisms are in the range of pulmonary deposition
(less than 5 p.m in diameter) and that viable particles are distributed
throughout the respirable range.
From a public health perspective, it is desirable that the dose com-
puted be the number of infective microorganisms, (i.e., those capable of
invading the host and proliferating to initiate infection). However,
Equation 7 utilizes the microbiological dispersion model prediction
which is based on air and wastewater sample assays for the microorgan-
ism. Thus, the dose calculated from Equation 7 is the number of viable
microorganisms (i.e., those capable of in vitro reproduction). Labora-
tory studies suggest (16) that the environmental stresses associated with
aerosol aging may damage aerosolized microorganisms so that their in-
fectivity sometimes diminishes more rapidly than their viability.
Feasible Applications in Population Studies
In light of the limitations just described, it is suggested that use of
inhaled doses calculated using the microbiological dispersion model and
Equation 7 be cautious and judicious. Applications that utilize the calcu-
lated doses merely to rank the level of human exposure appear to be
more tenable than those based on the calculated magnitude of the dose.
In population studies of infectious disease health effects, there are sev-
eral feasible applications.
The dose inhaled by each human subject or each household of sub-
jects can be estimated from Equation 7 in order to classify the subjects
into several groups based on the calculated level of their wastewater
aerosol exposure. The health responses (whether symptomatic, serol-
ogic, or clinical) among the subjects can then be analyzed both within
groups and between groups to investigate possible dose-response
relationships.
Another potential application is in etiologic case studies of infectious-
disease outbreaks which may have a wastewater aerosol origin. A diary
of activities that recorded unusual exposure situations might be a pre-
requisite for the calculation of inhaled dose to be useful in such etiologic
investigations.
ACKNOWLEDGMENT
Much of the research on which this paper is based was supported by
the U.S. Army Medical Research and Development Command and the
U.S. Environmental Protection Agency under Contract DAMD 17-75-C-
5072, "Evaluation of Health Effects Associated with the Application of
Wastewater to Land."
References
1. Cramer, H. E. 1957. A practical method for estimating the dispersion of atmospheric
contaminants. In: Proc. First Natl. Conf. on Appl. Meteorol. C. Amer. Meteorol. Soc.
pp. 33-35.
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David E. Camann 67
2. Cramer, H. E. 1959. A brief survey of the meteorological aspects of atmospheric
pollution. Bull. Amer. Meteorol. Soc. 40:165-171.
3. Cramer, H. E. 1959. Engineering estimates of atmospheric dispersal capacity. Amer.
Ind. Hyg. Assoc. J., 20:183-189.
4. Hay, J. S. and F. Pasquill. 1957. Diffusion from a fixed source at a height of a few
hundred feet in the atmosphere. J. Fluid Mech., 2:299-310.
5. Hay, J. S. and F. Pasquill. 1959. Diffusion from a continuous source in relation to the
spectrum and scale of turbulence. In: Atmospheric Diffusion and Air Pollution, Ad-
vances in Geophysics, 6, F. N. Frenkiel and P. A. Sheppard, eds. Academic Press,
New York. pp. 345-365.
6. Pasquill, F. 1961. The estimation of the dispersion of windborne material. Meteorol.
Mag., 90:33-49.
7. Gilford, F. A. 1961. Uses of routine meteorological observations for estimating atmos-
pheric dispersion. Nuclear Safety, 2:47-51.
8. Turner, D. B. 1970. Workbook of atmospheric dispersion estimates. Publication AP-
26. U.S. Environmental Protection Agency, Research Triangle Park, North Carolina.
9. Veigele, W. J. and J. H. Head. 1978. Derivation of the Gaussian plume model. J. Air
Poll. Control Assoc., 28:1139-1141.
10. Briggs, G. A. 1971. Some recent analyses of plume rise observations. In: Proceedings
of the Second International Clean Air Congress. Academic Press, New York. pp.
1029-1032.
11. Cramer, H. E., J. R. Bjorklund, R. K. Dumbauld, J. E. Faulkner, and F. A. Record.
1972. Development of dosage models and concepts. Deseret Test Center Report DTC-
TR-72-609. U.S. Army, Ft. Douglas, Utah.
12. Guzewich, D. C. and W. J. B. Pringle. 1977. Validation of the EPA-PTMTP short-term
Gaussian dispersion model. J. Air Poll. Control Assoc., 27:540.
13. Guldberg, P. H. and C. W. Kern. 1978. A comparative validation of the RAM and
PTMTP models for short-term SO2 concentrations in two urban areas. J. Air Poll.
Control Assoc., 28:907-910.
14. Monitoring and Data Analysis Division. 1977. Interim guideline on air quality models.
Environmental Protection Agency, OAQPS 1.2-080. U.S. Environmental Protection
Agency, Research Triangle Park, North Carolina.
15. Dimmick, R. L. and R. J. Heckly. 1969. Theoretical aspects of microbial survival. In:
An Introduction to Experimental Aerobiology, R. L. Dimmick and A. B. Akers, eds.
Wiley-Interscience, New York. pp. 347-374.
16. Akers, A. B. and W. D. Won. 1969. Assay of living, airborne microorganisms. In: An
Introduction to Experimental Aerobiology, R. L. Dimmick and A. B. Akers, eds.
Wiley-Interscience, New York. pp. 59-99.
17. Harper, G. J. 1961. Airborne microorganisms: survival test with: four viruses. Jour.
Hyg., 59:479-486.
18. Kethley, T. W., E. L. Fincher, and E. B. Cown. 1957. The effect of sampling method
upon the apparent response of airborne bacteria to temperature and relative humidity.
Jour. Infect. Dis., 100:97-102.
19. Hatch, M. T. and H. Wolochow. 1969. Bacterial survival: consequences of the airborne
state. In: An Introduction to Experimental Aerobiology, R. L. Dimmick and A. B.
Akers, eds. Wiley-Interscience, New York, pp. 267-295.
20. Sorber, C. A., H. T. Bausum, S. A. Schaub, and M. J. Small. 1976. A study of bacterial
aerosols at a wastewater irrigation site. Jour. Water Poll. Control Fed., 48:2367-2379.
21. Camann, D. E., C. A. Sorber, B. P. Sagik, J. P. Glennon, and D. E. Johnson. 1978. A
model for predicting pathogen concentrations in wastewater aerosols. In: Proceedings
of the Conference on Risk Assessment and Health Effects of Land Application of
Municipal Wastewater and Sludges. University of Texas at San Antonio, December
12-14, 1977. pp. 240-271.
22. Johnson, D. E., D. E. Camann, J. W. Register, R. E. Thomas, C. A. Sorber, M. N.
Guentzel, J. M. Taylor, and H. J. Harding. 1980. The evaluation of microbiological
aerosols associated with the application of wastewater to land: Pleasanton, California.
EPA-600/1-80-015. U.S. Environmental Protection Agency, Cincinnati, Ohio.
23. Johnson, D. E., D. E. Camann, H. J. Harding, and C. A. Sorber. 1979. Environmental
monitoring of a wastewater treatment plant. EPA-600/1-79-027. U.S. Environmental
Protection Agency, Cincinnati, Ohio.
24. Johnson, D. E., D. E. Camann, C. A. Sorber, B. P. Sagik, and J. P. Glennon. 1978.
Aerosol monitoring and microbial organisms near a spray irrigation site. In: Proc.
-------
68 Wastewater Aerosols and Disease/Contaminants
Conference on Risk Assessment and Health Effects of Land Application of Municipal
Wastewater and Sludges. University of Texas at San Antonio, December 12-14, 1977.
pp. 231-239.
25. Johnson, D. E., D. E. Camann, K. T. Kimball, R. J. Prevost, and R. E. Thomas. 1980.
Health effects from wastewater aerosols at a new activated sludge plant: John Egan
Plant, Schaumburg, Illinois. In: Proc. National Symposium on Wastewater Aerosols
and Disease. U.S. Environmental Protection Agency, Cincinnati, Ohio, September
19-21, 1979.
26. Johnson, D. E., D. E. Camann, J. W. Register, R. J. Prevost, J. B. Tillery, R. E.
Thomas, J. M. Taylor, and J. M. Hosenfield. 1978. Health implications of sewage
treatment facilities. EPA-600/1-78-032. U.S. Environmental Protection Agency, Cin-
cinnati, Ohio.
27 Camann, D. E., H. J. Harding, and D. E. Johnson. 1980. Wastewater aerosol and
school attendance monitoring at an advanced wastewater treatment facility: Durham
Plant, Tigard, Oregon. In: Proc. National Symposium on Wastewater Aerosols and
Disease. U.S. Environmental Protection Agency, Cincinnati, Ohio, September 19-21,
1979.
28. Bausum, H. T., S. A. Schaub, and K. F. Kenyon. 1978. Viral and bacterial aerosols at a
wastewater spray irrigation site. Technical Report 7804. U.S. Army Medical Bioengi-
neering Research and Development Laboratory, Ft. Detrick, Maryland.
29. Bausum, H. T., B. E. Brockett, P. W. Schumacher, S. A. Schaub, H. L. McKim, and R.
Bates. 1978. Microbiological aerosols from a field source during sprinkler irrigation
with wastewater. In: Proc. International Symposium on State of Knowledge in Land
Treatment of Wastewater. Vol. II. U.S. Army Corps of Engineers, Hanover, New
Hampshire, August 20-25. pp. 273-280.
30. Lindgren, B. W. 1962. Statistical Theory. MacMillan, New York. pp. 335-336.
31. Snedecor, G. W. and W. G. Cochran. 1%7. Statistical Methods. 6th Ed. Iowa State
University Press, Ames, Iowa. pp. 128-129.
32. May, K. R. and H. A. Druett. 1968. A microthread technique for studying the viability
of microbes in a simulated airborne state. J. Gen. Microbiol., 51:353-366.
33. Hood, A. M. 1971. An indoor system for the study of biological aerosols in open air
conditions. Jour. Hyg., 69:607.
34. Benbough, J. E. and A. M. Hood. 1971. Viricidal activity of open air. Jour. Hyg.,
69:619-626.
35. Druett, H. A. and L. P. Packman. 1968. Sensitive microbiological detector for air
pollution. Nature, 218:699.
36. Dark, F. A. and T. Nash. 1970. Comparative toxicity of various ozonised olefins to
bacteria suspended in air. Jour. Hyg., 68:245.
37. Harper, G. J. 1963. The influence of environment on the survival of airborne virus
particles in the laboratory. Archiv fur Die Gesamte Virusforschung, 13:64-71.
38. Akers, T. G. 1969. Survival of airborne virus, phage and other minute microbes. In:
An Introduction to Experimental Aerobiology, R. L. Dimmick and A. B. Akers, eds.
Wiley-Interscience, New York. pp. 296-339.
39. Sorber, C. A. and B. P. Sagik. 1980. Indicators and pathogens in wastewater aerosols
and factors affecting survivability. In: Proc. National Symposium on Wastewater
Aerosols and Disease. U.S. Environmental Protection Agency, Cincinnati, Ohio, Sep-
tember 19-21, 1979.
40. Pappagianis, D. 1969. Some characteristics of respiratory infection in man. In: An
Introduction to Experimental Aerobiology, R. L. Dimmick and A. B. Akers, eds.
Wiley-Interscience, New York. pp. 390-406.
41. Phair, J. 1980. Host defense mechanisms relevant to infection. In: Proc. National
Symposium on Wastewater Aerosols and Disease. U.S. Environmental Protection
Agency, Cincinnati, Ohio, September 19-21, 1979.
42. Guentzel, M. N. 1978. Potential impact on water resources of bacterial pathogens in
wastewater applied to land. In: Proc. Conference on Risk Assessment and Health
Effects of Land Application of Municipal Wastewater and Sludges. University of
Texas at San Antonio, December 12-14, 1977. pp. 180-194.
43. Spendlove, J. C. 1975. Penetration of structures by microbial aerosols. Devel. Indust.
Microbiol., 16:427-436.
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David E. Camann 69
DISCUSSION
DR. SPENDLOVE: Dave, I think you have done a wonderful job in
trying to pull together a number of parameters. I suggest that you in-
clude a penetration parameter.
MR. CAMANN: Yes, I believe you have done some work on that in
the biological warfare program. We are planning to do that in future
studies in order to get a handle on it.
DR. SPENDLOVE: I can give you a reference on a model that I
worked on with penetration, if you are interested.
MR. CAMANN: Yes, I am.
DR. SPENDLOVE: I thought that your reason for impact factors
exceeding one was right on line. Of course, we are dealing with a situa-
tion here that does not have a negative I index, and I think that it is easy
to explain why you get a high value with a breakup in the particles.
MR. CAMANN: Yes. That could be true. We have identified about
five possible hypotheses, that being one of them. We have no basis for
choosing among them at this point.
DR. SPENDLOVE: The other thing: your E values seemed awfully
strong to me, for spray irrigation particularly. Did you define those on
the basis of respirable particles?
MR. CAMANN: No, this was based on the use of a dye tracer and
the assumption that the microorganisms had the same characteristics of
aerosol formation as did the dye. A rotamine WT dye was used in the
Pleasanton study. I am not sure which dye they used on the Army
studies.
DR. SPENDLOVE: Generally, efficiency is based on the percentage
of respirable particles that are produced.
DR. FANNIN: I am wondering if you feel that with the unexpected I
value of 40 for the enterovirus, it is appropriate to make any prediction
as to the enterovirus concentration at the distances that you predicted.
MR. CAMANN: I did put an approximation on the 40 because it is
only based on two aerosol runs, one of which gave a value of I of
approximately 10, I believe, and the other, approximately 70. So it is
quite an approximation. The problem is that it takes a very extensive
aerosol monitoring program to come up with any value, and we simply
do not have enough data to be sure of the true value.
DR. WARD: I assume that this is probably one of your five explana-
tions, but I think about a year and a half ago an article came out in
Science that suggested that microorganisms are concentrated to higher
magnitude in the spray. Are you aware of that article?
MR. CAMANN: I am not aware of it. I would like to see it. In talking
to various people we have been speculating on various reasons since we
have started finding these values higher than one. I do have a summary
of these five hypotheses in one of my papers.
DR. FLIERMANS: How do you deal with the virulence factors as-
sociated with these various organisms? An organism that has recently
passed through a host of some sort is more virulent than one that has
not. How do you deal with that in the model?
MR. CAMANN: I have not attempted to deal with that, as you can
see. We are more or less just taking what comes out of an aerosol source
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70 Wastewater Aerosols and Disease/Contaminants
and projecting that into an exposure setting. As far as the virulence
factor goes, I have not tried to work in anything on that.
DR. LUE-HING: What was the population of viruses in the sewage
work?
MR. CAM ANN: I would have to defer to Chuck Sorber. It was just
a wastewater sample and a measurement of total enteroviruses, I
believe.
DR. SORBER: The mean virus concentration in the wastewater that
was sprayed was 17 pfu/1. There was quite a range on it.
DR. SPENDLOVE: Regarding the virulence question, of course this
is an extremely complex parameter to have to deal with, there has been
some work with it. They have to be studied with each individual organ-
ism. There has been considerable work done with Pasteurella tularensis,
as some of you may know, and models that deal with that concentration
downwind deal with it in virulence decay situations, the same as viabil-
ity decay. Of course the virulence does decay with travel downwind,
with that particular organism. I am assuming it also decays with the
intestinal organisms in very much the same way.
DR. SCHAUB: One of the things I am encouraged about from this
particular study that Dave has done is that an individual source, a line
source, and a field source were actually looked at after the model was
set up, and there was at least within an order of magnitude capability in
predictability of the aerosol dispersion. I think that is significant. I think
we are making progress in terms of identifying the downwind migration
of these aerosols.
DR. LUE-HING: When we make predictions of aerosols, the people
who have to relate to them are somewhat out of practice. State how
imprecise some of the data are. When you write your conclusions you
certify what that means. If they mean nothing don't write them, because
if you do, somebody will believe them and use them.
MR. CAMANN: I think the point that has to be raised, though, is
that we have to start quantifying doses. In the case studies that will be
presented, we need to start quantifying doses even if they are very
approximate and indicate the uncertainty in the measurement; but when
we have health effects or no health effects, we should give some idea of
the dose of exposure that we are talking about, whenever possible. I
agree that we definitely need to spell out how imprecise those numbers
are.
DR. LUE-HING: I am glad you agree. It is meaningless except if an
expert wants to use it.
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71
Infection and Resistance: A Review
John P. Phair
Section of Infectious Disease and Hypersensitivity
Dept. of Medicine
Northwestern University Medical School
Chicago, Illinois 60611
ABSTRACT
The relationship of infection and host defenses has provided much of the impetus for the
development of the science of immunology. Leukocytes play a central role in determining
the status of a host's ability to defend against or control infection in collaboration with a
variety of serum proteins. Defective function in any one of three types of white cells, the
polymorphonuclear leukocyte, the lymphocyte, or the phagocytic mononuclear cell, has
been associated with a distinctive pattern of infection. In addition, congenital and acquired
deficiencies of serum complement increased vulnerability to infection The objective of
this presentation is to review the'function of these cells and proteins and current concepts
of host resistance to infection
Historically, attempts to develop means of prevention and treatment
of diseases due to microorganisms provided the stimulus for the science
of immunology in the 19th century. With increased knowledge of the
relationship of the host to bacteria, it is recognized that parasitism of a
host can result in a symbiotic relationship, destruction of the parasite, or
death of the host and subsequently of the invading microorganisms. The
determinants underlying the outcome include host mechanisms, which
distinguish self from nonself, and protective or "virulence factors"
evolved by microorganisms which enhance their survival.
Disease results if virulence factors overwhelm host defenses and,
paradoxically, as a consequence of the host's recognition of nonself.
Thus, tissue injury can be produced by the inflammatory and immune
response evoked by bacteria, fungi, or viral invaders. For example, the
initial parasitism by the dengue virus results in a relatively mild illness
but provokes an immune response which is responsible for a serious
illness with hemorrhagic complications, shock, and a high mortality fol-
lowing a second infection with a serotypically related but different
dengue virus (1).
The specific immune response is genetically determined (2). In addi-
tion, alterations in immunity are associated with age. Successful influ-
enza vaccination may require two inoculations in the elderly (3,4), and
immunization with bacterial polysaccharide vaccines is less successful
in children under 12 months of age (5). The nonspecific inflammatory
response is also altered with age, intercurrent disease or therapy, and by
specific genetically determined abnormalities.
Unique characteristics of a specific parasitic and host interaction also
determine production of illness. Thus a lower inoculum of Salmonella
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72 Wastewater Aerosols and Disease/Health Aspects
typhosa will result in typhoid fever in the unimmunized host than in the
immunized individual (6).
Resistance to infection is determined, therefore, by multiple factors,
and although this presentation will examine in detail the cellular re-
sponse to infection, it must be emphasized that nonspecific barriers are
also important components of resistance. Such barriers include skin,
mucous membranes, respiratory epithelium, and gastric acid. Breaks in
these barriers due to trauma, surgery, disease, or environmental toxins
increase susceptibility to infection.
Host responses to microorganisms which have breached the external
barriers are dependent upon a diverse group of cells, the leukocytes.
Defective function of any of three cells, the polymorphonuclear neutro-
phil, the lymphocyte, or the monocyte (macrophage), has been asso-
ciated with specific patterns of infections. Defects in number and func-
tion of these cells and the infections associated with these deficiencies
will be discussed. For purposes of presentation, each cell will be consid-
ered separately, but it is good to emphasize that the response to infec-
tion involves a complex interaction of all three cells, their function, and
their extracellular products.
THE POLYMORPHONUCLEAR NEUTROPfflL (PMN)
The PMN, an efficient phagocytic cell, is central to the host's ability to
control infection by bacteria (7). To accomplish the task of disposing of
invading microorganisms, PMN must be produced in adequate numbers
by the bone marrow, enter the vascular space, leave the intravascular
compartment, and arrive at the site of bacterial invasion. The peripheral
blood contains the majority of neutrophils available for delivery to tis-
sue. Approximately one-half to two-thirds of these cells are in the so-
called marginal pool and are not detected by the usual white blood
counts. The neutrophils of the marginal pool cross the endothelial lining
of the vascular bed, enter the extravascular space, and emigrate to
tissue sites invaded by bacteria. Adherence of neutrophils to endothelial
cells is necessary before this diapedesis occurs (8). Neutrophil adher-
ence is enhanced in disease states and is characterized by inflammation;
conversely, adherence is depressed when patients are receiving anti-
inflammatory agents or after acute ingestion of alcohol.
In vivo inflammatory stimuli produce an emigration of PMN and
mononuclear cells into tissue. The normal entry of leukocytes into a skin
window is sequential: after a latent period of two hours, PMN are first
noted; by 12 hours, the peak PMN response is achieved; and by 24
hours, the predominant cell is mononuclear. Entry of neutrophils to an
area of inflammation is depressed in neutropenic states (less than 1500/
mm3), leukemia, acidosis, with corticosteroid therapy, and following
acute alcohol ingestion (9,10,11).
Once in the tissue space, PMN, which are motile, must be attracted to
the site of microbial invasion. This directed response is determined by
the cell's ability to detect and respond to chemotactic stimuli. Such stim-
uli are generated by most bacteria (12) and by soluble factors produced
as a result of complement activation (13). In certain families, deficien-
cies of the complement components C3 and C5 have been associated
with repeated infections (14). These patients may be thought of as hav-
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JohnP.Phair 73
ing a defective chemotactic response due to abnormalities in the milieu
in which the PMN must function. Similar complement deficiencies and
defective neutrophil responses have been noted in cirrhotic patients
(15). Production of circulating inhibitors of PMN chemotaxis have been
demonstrated in the serum of patients with Hodgkin's disease and carci-
noma of the lung (16). In addition, children with eczema, excessive
circulatory IgE, and impaired leukotactic responses thought to be due to
the effects of histamine on PMN motion have been reported (14). In
contrast to these humoral perturbations, intrinsic abnormalities of neu-
trophil function have been described in children with the lazy leukocyte
syndrome, in diabetics, and in near relatives of diabetic patients whose
cells do not respond to chemotactic stimuli (14).
Neutrophils, once in contact with the invading microorganisms, must
engulf and subsequently kill the invader intracellularly. Phagocytosis of
some microorganisms, classically encapsulated pyogenic organisms, re-
quires the presence of adequate serum opsonins, such as specific anti-
body (see below), or complement, or both (7). Poor opsonization has
been associated with defective conversion of the third component of
complement by insulin, a measure of the alternate complement pathway
function. C3- and C5- deficient kindreds are vulnerable to gonococcemia
and meningococcemia (14). Sera from patients with a deficiency of C2
poorly support phagocytosis of Staphylococcus aureus while continuing
to provide adequate opsonization of the gram-negative bacterium, Es-
cherichia coli (17). This recent observation and other studies emphasize
the complex relationship between specific components of the opsonic,
phagocytic, and bacterial systems (18).
The killing of bacteria by PMN involves both oxidative bactericidal
mechanisms and release of cationic proteins from cytoplasmic granules
into the phagolysosome containing the bacteria (7). The oxidation mech-
anisms involved include uptake of O2 and of glucose, a production of
CO2, H2O2 (singlet and superoxide), and the fixation of a halide by the
enzyme, myeloperoxidase. In vitro killing of ingested organisms is ac-
complished within minutes; digestion is a longer process.
Characteristically, deficits in number or function of the PMN results
in infection by S. aureus, endogenous aerobic, and anaerobic gram-
negative bacilli or fungi. Pneumonia, visceral abscess, perirectal ab-
scess, deep pharyngeal infections, and bacteremia are common. If the
defect is not transient, these infections recur. Successful treatment re-
quires adequate surgical drainage when possible and prolonged courses
of bactericidal antibiotics.
THE LYMPHOCYTE
The lymphocyte has been established as the major cellular element in
the immune response. Schematically, two populations of lymphocytes
have been delineated: immunoglobulin-(antibody) secreting cells (B-
cells) and the thymus-dependent cells (T-cells) (19). Thymus-dependent
cells mediate host-versus-graft reactions, contact-sensitivity reactions,
and other manifestations of cellular immunity. Certain T-lymphocytes
also can function as helper cells in the production of antibody by B-
lymphocytes. T-lymphocytes also regulate the immune response
through suppressor effects and production of lymphokines which modu-
late macrophage function.
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74 Wastewater Aerosols and Disease/Health Aspects
B-CELLS
Immunoglobulins, the secretory products of B-lymphocytes, exist in a
variety of classes in serum and in body secretions. IgG and IgM appear
to mediate the majority of immune reactions concerned with defense
against microbiologic agents such as opsonization, complement fixation,
and viral and toxin neutralization. Specific IgA, induced by infection or
local immunization, prevents adherence of virus or bacteria to mucosal
surfaces (20). The function of IgD is unknown, but it may act as a
surface receptor on B-lymphocytes that combines with antigen to trigger
specific antibody production (21). Reagin of IgE mediates immediate
allergic reactions by triggering the release of vasoactive substances from
mast cells following interaction of allergens with specific mast cell-
bound IgE. It has been postulated that its defensive role is to control
parasitic infection or to amplify host responses to foreign antigens
crossing mucosal surfaces.
The underlying cause of the wide variety of B-lymphocyte deficien-
cies varies (14). In X-linked hypogammaglobulinemia, there is an ab-
sence of B-lymphocytes. In contrast, some cases of common variable
immunodeficiency appear to be the consequence of overactive suppres-
sor cells, which depress B-lymphocyte function. In addition, a few chil-
dren with defects in purine metabolism, transcobalamin II deficiency,
and hypoxanthineguanine phosphoribosyl transferase (Lesch-Nyhan
syndrome) have been described with B-lymphocyte abnormalities. The
infections seen with hypogammaglobulinemia are classically those in
which antibody is required to overcome bacterial-antiphagocytic factors
such as the capsular polysaccharide of Haemophilus influenzae. Second-
ary hypogammaglobulinemia occurs with chronic lymphocytic leuke-
mia, the paraproteinemias, multiple myeloma, and some cases of non-
Hodgkin's lymphoma.
T-CELLS
Thymus-dependent lymphocytes make a complex contribution to host
defense (23). Cooperation between T- and B-cells is required for matura-
tion of antibody production by B-cells, i.e., the production of IgG fol-
lowing initial secretion of IgM. IgA and IgE also require interaction
between T-helper and B-cells. Some antigens such as polysaccharides
are thymus-independent and elicit antibody responses in the absence of
T-B-cell cooperation, however, the majority of microorganisms with
their complex structure induce thymic-dependent immune response. A
subset of T-cells inhibit antibody production. Other T-cells suppress
effector functions of T-lymphocytes. The role of suppressor T-cells in
mediating tolerance to foreign antigens and enhancement of tumor or
homograft survival remains under investigation (24).
In vitro sensitized T-lymphocytes produce, upon appropriate anti-
genie stimulation, a number ot soluble factors, the lymphokines, which
are thought to mediate cellular immunity (22). The biologic significance
of these products is thought to be an amplification of host recognition of
a foreign antigen. It has been demonstrated that few specifically sensi-
tized lymphocytes (less than 5% of the total cells involved) provoke a
significant inflammatory response upon challenge by antigen. This am-
plification is theoretically mediated by the soluble products of T-lym-
phocytes, which attract macrophages, retain them at the appropriate
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JohnP. Pfiair 75
site, and increase their bactericidal capacity. These effects are nonspe-
cific and have been shown to affect macrophages derived from nonsensi-
tized hosts. Other lymphokines attract neutrophils. In addition to inter-
acting with phagocytic cells, lymphokines have been identified that
induce a mitogenic response in nonsensitized lymphocytes, thus provid-
ing more cells at the immunoinflammatory focus. A transfer factor con-
verts nonsensitive lymphocytes to an antigen-responsive state, again
amplifing the response. Finally, T-lymphocytes release interferon, an
antiviral substance, either following exposure to specific antigens or
nonspecifically, following exposure to mitogens. Defects in thymus-de-
pendent responses are due to multiple causes (14). Congenital thymic
aplasia (the DiGeorge syndrome) represents a failure of normal em-
bryologic development of the thymus and parathyroid glands from the
third and fourth pharyngeal pouches. The prototype of a combined T-
and B-lymphocyte disorder, severe combined immunodeficiency dis-
ease, in contrast to the DiGeorge syndrome, represents failure of the
stem cell of both T- and B-lymphocytes to differentiate normally or,
alternatively, represents a deficiency of the enzyme adenosine deami-
nase. Depressed cellular immune responses are also found in a number
of neoplastic diseases. Hodgkin's disease represents the best example of
a neoplastic disease in which T-lymphocyte dysfunction has been dem-
onstrated. Similar depression has been noted in disseminated infections
due to intracellular organisms, such as in lepromatous leprosy, tubercu-
losis, and histoplasmosis. Acute viral and pyogenic bacterial infections
have been associated with transient dysfunction of T-lymphocyte re-
sponses. Lack of in vitro lymphocyte responsiveness and depressed skin
reactivity have been noted in aged individuals and patients with protein-
calorie malnutrition.
Infection by intracellular pathogens such as fungi, herpes virus, and
mycobacterium result from depression of cellular immunity. Correlation
of T-cell dysfunction and such infection has been clearly established in
Hodgkin's disease, in patients receiving cytotoxic therapy for neoplastic
disease, or in patients receiving immunosuppressive therapy to control
host-versus-graft reactions. latrogenic interference with cell-mediated
responses has been one of the major limitations of cytotoxic and immu-
nosuppressive therapy.
THE MONONUCLEAR PHAGOCYTE
The third cell that is involved in host defenses against microorganisms
is the phagocytic monocyte or macrophage (25). These cells, which are
derived from the bone marrow, are located in the peripheral blood
(monocytes) or in tissues (macrophages). They are fixed in specific or-
gans, lining the sinuses of liver and spleen and the pulmonary alveoli.
Monocytes can leave the vascular compartment, enter the tissues, and
participate in cell-mediated reactions described above. With appropriate
stimulation, the number of mononuclear phagocytic cells in the liver can
be greatly expanded by both proliferation and recruitment of blood
monocytes.
Macrophages have receptors for IgG and complement that enhance
adherence of opsonized particles and facilitate ingestion. They also are
capable of nonimmune phagocytosis. Phagocytosis and ingestion of an-
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76 Wastewater Aerosols and Disease/Health Aspects
tigen by mononuclear cells presumably play important roles in the prep-
aration and presentation of antigen to lymphocytes, a precondition for
the immune response. In addition, macrophage products or cell-to-cell
contact between macrophages and lymphocytes facilitates lymphocyte
responses to antigen and to mitogens.
Mononuclear cells produce a metabolic burst following ingestion of
bacteria, which is dependent upon hexose monophosphate shunt activa-
tion. Killing of bacteria in these cells may involve H2O2 production and
fixation of halide, as in PMN. Enzymes in macrophages include hydro-
lases, also found in PMN, which are involved in the digestion of ma-
cromolecules. The cationic proteins of neutrophils, which are bacterici-
dal, are lacking.
Certain bacteria have evolved the ability to survive within macro-
phages. The tubercle bacillus, for example, can survive and replicate
intracellularly. Other organisms also resist killing unless coated with
antibody; this emphasizes the intimate relationship between lympho-
cytes or products of lymphocytes and the phagocytic mononuclear cell.
Dysfunction of the mononuclear leukocytes has been demonstrated in
chronic granulomatous disease, in certain hematologic neoplasmas, in
malacoplakia, and in association with corticosteroid therapy. Dissemi-
nated infections due to intracellular pathogens may represent an exam-
ple of intrinsic dysfunction of this system of phagocytes. However, a
failure of macrophage-lymphocyte interaction, or a lymphocytic defect,
could mimic an intrinsic defect in macrophage function.
Diseases that are associated with proliferation of monocytes, as mani-
fested by peripheral blood monocytosis or enlargement of the spleen
and liver, include chronic infections such as subacute bacterial endocar-
ditis, tuberculosis, neoplastic disease such as Hodgkin's disease or mye-
lomonocytic leukemia, hemolysis, inflammatory bowel disease, collagen
vascular disease, and chronic diseases associated with granuloma for-
mation of unknown etiology. The nature of the stimulus causing the
hyperplasia of this cell type is unknown.
RELEVANCE OF CELL DEFECTS TO INFECTION
Increased understanding of the function of PMN, lymphocytes, and
mononuclear phagocytes has emphasized the complex nature of host
defenses. Although patterns of infection can be associated with a spe-
cific defect, the most common clinical problem is infection in a host with
a combination of defects. Thus, the patient with Hodgkin's disease may
have depressed T-cell function and be receiving cytotoxic agents which
induce neutropenia and corticosteroids which alter PMN and mononu-
clear cell function. In addition, the patient may be malnourished second-
ary to anorexia and be receiving treatment through an intravenous line
which provides a portal of entry for bacteria. Less dramatically, elderly
patients have alterations in cellular immunity, changes in immunoglobu-
lins, a poor response to vaccination, and depressed PMN function.
The number of conditions or diseases associated with alterations in
host defense mechanism is long and becoming longer (14). The challenge
is to relate clearly the in vitro demonstration of a defect with increased
susceptibility to infection and to find acceptable methods for correcting
the relevant deficiency.
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JohnP.Phair 77
References
1. Halstead, S. B. 1970. Observations relating to pathogenesis of dengue hemorrhagic
fever: VI. Hypothesis and discussion. Yale J. Biol. Med., 42:350.
2. Bach, F. H. and J. J. van Road. 1976. The major histocompatibility complex. Genetics
and biology. New England Jour. Med., 295:927.
3. Mackenzie, J. S. 1977. Influenza subunit vaccine: antibody response to one and two
doses of vaccine and length of response with particular reference to the elderly. Brit
Med. J., 1:200.
4. Phair, J., C. A. Kauffman, A. Bjornson, L. Adams, and C. Linneman, Jr. 1978. Failure
to respond to influenza vaccine in the aged: correlation with B-cell number and func-
tion. J. Lab. and Clin. Med., 92:822.
5. Makela, P. H., H. Pel tola, H. Kayhty, J. Jousimies, O. Pettay, E. Ruoslaht, A. Sivonen,
and O-V. Renkonin. 1977. Polysaccharide vaccine of group A. Neisseria meningitides
and Haemophilus influenzae type B. A field trial in Finland. Jour. Infect. Dis.,
136:543.
6. Hornick, R. B., S. E. Greisman, F. E. Woodward, H. L. Dupont, A. T. Dawkins, and
M. J. Snyder. 1970. Typhoid fever. Pathogenesis and immunologic control. New Engl.
Jour. Med.,283:686-739.
7. Stossel.T.P. 1974. Phagocytosis. New Eng. Jour Med., 290:717, 774, 883.
8. MacGregor, R. R., E. J. Macaraks, and N. A. Kefalides. 1978. Comparative adherence
of granulocytes to endothelial monolayers and nylon fiber. J. Clin. Invest., 61:697.
9. Dale, D. C., and S. M. Wolff. 1971. Skin windows studies of the acute inflammatory
response of neutropenia patients. Blood, 38:138.
10. Perrillie, P. E., and S. C. Finch. 1964. Quantitative studies of the local exudative
reaction in acute leukemia. J. Clin. Invest., 43:425.
11. Brayton, R. G., P. E. Stokes, M. S. Schwartz, and D. B. Louria. 1970. Effect of
alcohol and various diseases on leukocyte mobilization, phagocytosis and intracellu-
lar bacterial killing. New Eng. Jour. Med., 282:123.
12. Ward, P. A., I. H. Lepow, and L. J. Newman. 1968. Bacterial factors chemotactic for
polymorphonuclear leukocytes. Am. J. Path.,52:725.
13. O'Flaherty, J. T., and P. A. Ward. 1979. Chemotactic factors and the neutrophil.
Seminars in Hem., 16:163.
14. World Health Organization Report. 1979. Immunodeficiency. Clin. Immunol. and Im-
munopath., 13:297-359.
15. DeMeo, A., and B. Anderson. 1972. Defective chemotaxis associated with a serum
inhibitor in cirrhotic patients. New Eng Jour. Med., 286:735.
16. Maderazo, E. C., T. F. Anton, and P. A. Ward. 1978. Serum associated inhibition of
leukocytes in humans with cancer. Clin. Immunol. and Immunopath., 9:166.
17. Repine, J. E., C. C. Clawson, and P. S. Friend. 1977. Influence of a deficiency of the
second component of complement on the bactericidal activity of neutrophils in vitro.
J. Clin. Invest.,59:802
18. Guckian, J. C., W. D. Christensen, and D. P. Fine. 1978. Evidence for quantitative
variability of bacterial opsonic requirements. Inf. and Imm., 19:822.
19. Greaves, M. F., J. J. T. Owen, and M. C. Raff. 1973. T and B lymphocytes: origins
properties and roles in immune response. In: Excerpta Median, Amsterdam. Ameri-
can Elsivier Publ., New York.
20. Tomasi, T. B. 1970. Structure and function of mucosal antibodies. Ann. Rev. Med.,
21:281
21. Vitetta, E. S., and J. W. Uhr. 1974. Immunoglobulin receptors revisited. A model for
the differentiation of bone-marrow derived lymphocytes is described. Science,
169:964.
22. Goetzl, E. J. 1977. Mast cell mediated reactions of host defense and tissue injury.
Inflammation. 2:239.
23. Waksman, B. H. 1979. Cellular hypersensitivity and immunity. Conceptual changes
the last decade. Cell. Imm., 42:155.
24. Waldmann, T. A., and S. Broder. 1977. Suppressor cells in the regulation of the
immune response. In: Progress on Clinical Immunology, S. Schwartz, ed. Graue &
Stratton, New York.
25. Cline, M. J. 1975. Monocytes and Macrophages: The White Cell. Harvard University
Press, Cambridge, Massachusetts.
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78
Infection with Minimal Quantities of Pathogens
from Wastewater Aerosols
Dean O. Cliver
Food Research Institute (Department of Food Microbiology and
Toxicology), World Health Organization Collaborating Centre on Food
Virology, and Department of Bacteriology; College of Agricultural and
Life Sciences; University of Wisconsin, Madison, Wisconsin 53706
ABSTRACT
Raw wastewater invariably contains human pathogens. These pathogens are a threat to
public health to the degree that: 1) susceptible people are actually exposed to them; 2) an
infection results from the exposure; and 3) disease results from the infection. To be
considered in the present discussion, the pathogen must also have been disseminated in an
aerosol at some point between the raw sewage and the susceptible person. Of the human
pathogens which occur in aerosols from sewage treatment or application, some may be
capable of infecting directly upon inhalation. More concern has usually been directed to
the potential deposition of airborne pathogens upon food crops or on other surfaces to
which people are exposed. Few data indicate that people have actually become ill because
of aerial dissemination of pathogens from wastewater; however, negative epidemiologic
evidence is even less persuasive than most other kinds of negative evidence. Prudence
dictates that people should not venture closer than necessary to a source of wastewater
aerosol, yet people visiting sewage treatment plants regularly stand in the aerosol cloud of
the activated sludge tanks without perceptible ill effects. Wastewater probably should not
be sprayed directly onto vegetables that are to be consumed by humans, but aerosols (in
the strict sense of the word) apparently are not a very efficient means for disseminating
wastewater-borne pathogens.
This symposium is evidence of the concern that exists regarding health hazards asso-
ciated with wastewater aerosols. Aerosols are a result of using some effective and energy-
efficient methods of wastewater treatment and disposal. Concern over health hazards
seems to have been based largely upon some worst-case assumptions about the effects of
exposure to aerosols. In addressing my assigned topic, I do not intend routinely to assume
the worst case.
PATHOGENS IN WASTEWATER AEROSOLS
The domain of this paper is the dependence of human infection and
disease upon dose, where the infectious agent is present in a wastewater
aerosol. The infectious agents which are in wastewater and may be a
threat to human health are essentially those produced in the human
intestines. These agents occur in wastewater through the agency of the
water carriage toilet, which itself generates aerosols when flushed (1,2).
It seems clear that this and virtually all subsequent chances of dissemi-
nating pathogens in wastewater aerosols could be avoided if an alterna-
tive to the water carriage toilet could be developed for feces disposal.
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Dean O. C/iver 79
Levels of Pathogens in Wastewater
If feces are carried by wastewater, then bacteria, viruses, and proto-
zoan and metazoan parasites are likely or certain to be present, depend-
ing on the size of the population served and, to a limited extent, the
season. The incidence of most of these agents in human feces has been
quite thoroughly summarized by Geldreich (3). The dilution factor for
feces in household or community sewage will fall somewhere in the
range of 1,000 to 10,000. The derivation of these factors will not be
discussed here, but it does seem worth noting that the ten-fold range of
uncertainty that is included here is at least as precise as the estimates for
the levels of most organisms in the feces themselves. For organisms
which are part of the normal intestinal flora, initial numbers in sewage
should be lower than those in feces by factors of 1,000 to 10,000. Be-
cause any given pathogen is absent from the intestines of most members
of a community on any given day, the initial level of the pathogen in
sewage must be estimated from the level of the pathogen in positive
stools, reduced by the dilution factors just quoted, and reduced further
by the proportion of the donor population that does not harbor the agent
in question. A pathogen present in the feces of 1 to 10% of members of a
community at a level of 108/g might occur in raw sewage at levels of 105
tolO7/!.
Wastewater Aerosols
In a properly designed and operated sewer system, the raw sewage
spends relatively little time in transit between the source and the treat-
ment plant. The actual time might range from an hour to something less
than a day, depending on the size of the system. There should be little
microbial action or loss of sediment during that time, though a small loss
of pathogen titer might occur at the moderate temperatures of sewage.
Any aerosols produced in transit would be a risk only to those whose
occupation took them into the sewers.
The foci of attention, from the standpoint of aerosol production,
must be the sewage treatment plant (principally during aerobic second-
ary treatment) and disposal sites where spray application is practiced.
Aerosol generation and decay are the domain of others at this sympos-
ium. A few brief generalizations will suffice here. First, pathogen levels
in wastewater during secondary treatment may be only slightly less than
those in raw sewage, whereas those in treated wastewater or digested
sludge at an application site should be significantly reduced. Also, the
degree of exposure to the aerosols should generally be greatest for
workers at the site, less for visitors to the site, and less still for those
who live near the site.
INFECTION VIA AEROSOLS
Persons exposed directly to aerosols might become infected either
because inhalation led immediately to a respiratory infection or because
respiratory mucus laden with trapped pathogens was swallowed so that
infection took place in the digestive tract. Aerosols might also settle on
food or water and lead to infection via the digestive tract. With the
possible exception of Mycobacterium tuberculosis, few agents which
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80 Wastewater Aerosols and Disease/Health Aspects
can infect the lungs are known to occur with significant frequency in
sewage. A few of the enteric viruses in sewage may be able to infect the
upper respiratory tract. However, it appears that sewage aerosols have
principally to be considered yet another of the many means by which
fecal-oral transmission of enteric pathogens may occur.
One can follow this train of assertions to the conclusion that a given
quantity of pathogen in a sewage aerosol should represent a threat to
public health no greater than that of the same quantity of pathogen
ingested with any vehicle. A possible exception to this is the finding of
Darlow et al. (4) that lethal infections in mice were produced by consid-
erably smaller doses of Salmonella typhimurium when inhaled than
when ingested. The conclusion drawn is undoubtedly valid, but it may
well be irrelevant to human health. Pulmonary salmonellosis is virtually
unknown in humans, although those who work in the poultry industry
must have their respiratory tracts challenged even more frequently with
airborne Salmonella spp. than with the agent of ornithosis, which is
frequently transmitted to them in this way.
If enteric pathogens are not uniquely infectious by the aerosol
route, then any available data on peroral infectivity of these agents
should be pertinent to the present question. There are at least some data
for bacteria, viruses, and protozoa. Most of the controlled experiments
that have been reported were done with healthy young men as subjects;
the results may be applicable to the rest of humanity only with some
reservations. A few incidental reports are also worth noting.
Infection
Infection can be defined as the establishment and propagation of an
agent in a host. Infection by an enteric agent can frequently be con-
firmed by showing that more of the agent is shed in the stool than what
was originally fed to the host; infection can also be inferred if the host
begins to produce antibodies against the agent that was administered.
An infectious dose of an agent is the quantity that produces infection.
Disease
For the present discussion, disease can best be defined as a state of
abnormality that results from infection of a host. The ability of an infec-
tious agent to induce disease in a host may be called virulence or patho-
genicity, and the process of disease production is termed pathogenesis.
One might define the pathogenic dose of an infectious agent as the
quantity that produces disease. For nonpathogenic species and for at-
tenuated agents such as the oral poliomyelitis vaccine viruses, there
should be no such thing as a pathogenic dose; an infinite quantity of the
infectious agent should fail to produce disease in the infected host. At
the other extreme, there are agents (not necessarily of enteric origin) so
virulent that virtually every infection will induce at least some signifi-
cant abnormality in the host. Many agents produce infections that give
rise to illness only on occasion. One might well suppose intuitively that
pathogenesis by such agents is dose-dependent, i.e., that some larger
quantity of the agent is required to induce disease than that which pro-
duces infection. As it happens, I have been unable to find clear experi-
mental evidence that this is true for any agent which might infect via
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Dean O. Cliver 81
wastewater. It appears, instead, that the likelihood that infection by one
of these organisms will result in disease depends upon the interaction of
the agent's virulence, the host's resistance, and chance, but probably
not to any significant degree upon a dose greater than that which sufficed
to produce infection.
Host Factors
The human body is more complex than any of its parasites, so it is not
surprising that a great many determinants of the host-parasite relation-
ship originate in the host. Despite the acknowledged significance of
these host factors, most of them are as yet poorly understood. A brief
survey of the scope of these seems appropriate, but any extensive dis-
cussion would likely consist more of platitudes than of facts.
Protozoan parasites and the majority of enteric bacteria and viruses
show a high order of species and tissue specificity. Recognition factors
for viruses may consist of specific receptors on the plasma membranes
of appropriate host cells, but other factors are undoubtedly also in-
volved. The means by which enteric bacteria and protozoan parasites of
man recognize distinctive features of the environment in the human
intestines as correct are largely unknown. This is unfortunate, inasmuch
as the practical importance of these phenomena to sewage treatment and
disposal is enormous. More research on the subject is certainly needed,
but it will be very difficult to do because use of human subjects is
increasingly constrained, and research with any nonhuman species is
subject to criticism for that reason alone.
Immunity, another major host factor, has come to be relatively well
understood in recent years. That is, a great deal has been learned of how
an infectious agent evokes a humoral or cellular immune response in a
host. The immune response to an enteric virus infection may provide the
host with relatively solid and durable protection against that type of
virus, perhaps for the life of the host. Immunity against enteric bacteria
is apparently less durable, and the immune response against protozoan
parasites evidently offers relatively little protection against reinfesta-
tion.
Between the species and tissue specificity factors (which are innate
and more or less constant) and immunity (which is acquired after experi-
ence with an infectious agent) there is a spectrum of factors categorized
as "resistance." Though resistance has meaning only in relation to in-
fectious agents, resistance is presumably something the host either does
or does not have before the encounter with an infectious agent. Resist-
ance to infection may be enhanced by the presence in the host of a
competing normal microbial flora and may be diminished by the pres-
ence of a second infectious agent. Most aspects of resistance are very
poorly characterized: some appear to be intrinsic to the host's own
organism, whereas others are said to be derived from such exogenous
sources as chicken soup. Stress and nutrition are undoubtedly
influential.
Specificity and immunity are probably the host factors most effec-
tive in determining whether an infection takes place; whereas the resist-
ance factors, and in some cases immunity, are the principal determi-
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82 Wastewater Aerosols and Disease/Health Aspects
nants of the course of an infection once it has begun. All of the agents
under consideration here infect by way of the digestive tract. Some may
remain there and cause disease, but others must work their way from the
digestive tract to other parts of the body if disease is to ensue. There-
fore, the outcome of an infection by one of the latter type agents may be
determined by how effectively the infection is confined to the intestines,
rather than by how rapidly the body suppresses the infection entirely. It
is this least-characterized category of host resistance factors that I be-
lieve includes the major determinants of whether infection by a patho-
gen results in disease.
PERORAL INFECTION WITH MINIMAL DOSES
Studies of peroral infection by bacteria and viruses have been sur-
veyed elsewhere (5). I shall cite a few studies here but will not attempt
an exhaustive review.
Bacteria
The genus Salmonella has attracted much attention because it is rela-
tively frequently transmitted through food and water. Early studies had
indicated that Salmonella infection would usually result only if millions
of viable cells were ingested, but more recent research has demon-
strated infections with smaller doses in some instances. A study in
which S. typhi was fed to volunteers makes the unfortunate error of
reporting results in infectious doses when the text makes it plain that
those who were infected but not ill were scored as negative (6). Rates of
illness observed at different numbers of organisms administered were
0% at 103, 28% at 10s, 50% at 107, and 95% at 109. Typhoid is a systemic
disease; in the light of what was said above concerning host factors and
pathogenesis, it is perhaps significant that the ten thousandfold increase
in dose from 105 to 109 produced a reduction of median incubation
period from 9 days to 5 days, which may not have been significant in
view of the wide ranges quoted for the incubation periods in each group.
S. cubana, present as a contaminant in a carmine dye (7) preparation
used to measure intestinal transit times on a hospital ward for patients
with gastrointestinal problems, caused illness when approximately
15,000 cells were ingested. Unlike those used as research volunteers,
these people spanned a great range of ages, and many were debilitated
by another existing illness before they ingested the S. cubana.
A more normal sample of the public was recently exposed to choco-
late caster eggs and rabbits contaminated with S. eastbourne (R. H.
Deibel, Department of Bacteriology, University of Wisconsin-Madison,
personal communication, 1979). Healthy adults and children developed
Salmonella gastroenteritis after eating candy contaminated with levels
of < 1 to 100 organisms/100 g.
Infection and disease may follow ingestion of very small numbers of
Shigella organisms. In volunteer studies, the numbers of subjects in-
fected or made ill by small doses of highly virulent Shigella flexneri 2A
were roughly comparable (8). About 25% were infected and made ill
after ingesting 180 cells; infection rates were roughly level, in the range
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Dean O. Cliver 83
of 50 to 70%, with doses of 5,000, 10,000, and 100,000 organisms. De-
spite the extreme infectivity and virulence of this organism, it appears
that at least 30% of the volunteers were insusceptible to it. This insus-
ceptibility was presumably the result of previous exposure to the organ-
ism (or to one of its immunologic relatives); yet the presumed prior
exposure must not have resulted in a high level of humoral antibody,
inasmuch as serum antibodies were measured, and a high level of preex-
isting antibody would almost certainly have disqualified a volunteer
from participation in the study. Host factors, yet to be defined, were
undoubtedly at work.
In a study that involved smaller numbers of subjects, one out of 10
subjects who were fed cells of an invasive strain of Shigella dysenteriae
1 became ill (9). The proportion of subjects made ill appeared to increase
with larger doses, but one of six who received 10,000 cells (the highest
level of this strain administered) remained well. Infections unaccompan-
ied by illness were recorded as negative results; doses of 106 or more
cells of noninvasive strains were said to have been tolerated. Mean
incubation periods were reported for illnesses caused by the invasive
strain and did not appear to vary as a function of dose over the range
tested.
Two invasive strains of enteropathogenic Escherichia coli were used
in another human volunteer study (10). The results are somewhat diffi-
cult to evaluate because of the style of reporting. One strain caused
infections in some of the recipients of doses of 104 and 106 cells, but
disease was not seen with doses less than 108. The other strain appeared
to be less infectious but more virulent. This study is the only one of
those considered which seems to show some indication of a dose effect
inpathogenesis. Unfortunately, one of the experimental groups seemed
to have included more ill persons than could be shown to have been
infected by the criteria that were applied.
It appears that there are bacteria which can occasionally cause infec-
tion and disease upon ingestion of 10 organisms or less. With other
species, infections were seen only in persons who had ingested at least
104 organisms. However, given the small numbers of persons involved
in a human volunteer study, it may be that if an infection resulted when
one subject ingested 10,000 organisms, one infection would also have
resulted among 10,000 persons, each of whom ingested one organism.
There are ordinarily fewer illnesses than infections, but this does not
necessarily indicate that more organisms must be ingested to cause dis-
ease than the number that causes infection. Where more illnesses than
infections are seen, some skepticism is in order.
Viruses
Human volunteer studies of peroral infection with viruses have been
done quantitatively only with vaccine polioviruses. Even so, the quanti-
ties of virus administered have been expressed in terms of tissue culture
infectious doses which bear an uncertain relationship to numbers of
viral particles. The studies done with vaccine polioviruses afford only
slightly more accurate estimates of virus dosage than studies with Hepa-
titis A in which dosages were expressed as dilutions of infectious human
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84 Wastewater Aerosols and Disease/Health Aspects
stool. The vaccine polioviruses are attenuated to a degree that precludes
comparisons of the infectious dose and the pathogenic dose.
Human studies involving the vaccine polioviruses have been reviewed
elsewhere (5). Studies in which infections resulted after ingesting from
one to 20 tissue culture doses of vaccine poliovirus have been reported
from the Wistar Institute (11,12,13); whereas others have reported infec-
tions only after 103-5 or more tissue culture doses were ingested by large
numbers of subjects. Obviously, there was no means of determining the
pathogenic dose.
At least two pertinent studies of peroral infection by other enterovi-
ruses have been done with experimental animals. Coxsackievirus B5
produced illness (which was the criterion of infection) when newborn
mice ingested between 102 and 103 tissue culture doses (14). From the
standpoint of relevance to our present topic, the most positive aspect of
this study was that it was done with a virulent human enterovirus, and
the most negative feature was that the mouse is not known to be the
homologous host species for this virus.
My own group at the University of Wisconsin-Madison has done
some yet-to-be-published work* in which porcine enteroviruses were
administered perorally in water to young weanling pigs. Virulent strains
of two different serotypes were used to challenge animals that were fed
a "human" diet and maintained in individual isolators. Many infections,
but no disease, resulted. With porcine enterovirus type 3 (Strain ECPO
6), infections were seen only in animals which received at least 1,000
plaque-forming units (pfu) of the virus, administered either as a single
dose or given in aliquots on 4 successive days. Infections with type 7
(Strain O5I) occurred with doses as low as 350 pfu. The apparent cumu-
lation of risk when a dose was subdivided and given over several days'
time made it seem that there was no absolute minimum quantity of virus
which must be ingested at once for infection to occur.
A tissue culture dose of an enterovirus, whether scored on the basis of
plaque formation or of cytopathic effect, is equivalent to 10 to 1,000
virus particles. Unfortunately, none of the virologic studies discussed
above included enumeration of virus particles, so there is no absolute
basis on which to compare doses among studies or between viruses and
other types of infectious agents. No viruses of groups other than the
enteroviruses seem yet to have been used in peroral infectivity studies.
Protozoa
Human volunteers received cysts of Endamoeba (now Entamoeba)
coli and of Giardia lamblia perorally in two studies published 25 years
ago (15,16). One of eight volunteers who each received a single Enta-
moeba cyst became infected; the proportion of subjects infected by
larger doses was greater, to a maximum of two out of two at a dose of
104 cysts. None of five volunteers who ingested a single Giardia cyst
became infected; but all volunteers given doses from 10 to 106 were
infected, except for 14 of a group of 20 at a dose of 25 cysts.
The biological or morphological unit of dose in these experiments was
the cyst. When small numbers were given, cyst counts could be verified
*Report no. EPA 600/1-80-005.
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Dean O. diver 85
directly by microscopic inspection before administration. No illnesses
resulted, even among those who got large numbers of Giardia cysts.
MATHEMATICAL MODELING
All who deal with these kinds of problems aspire to a mathematical
model that could be used both descriptively to summarize research re-
sults and prospectively in making risk assessments. An idea model
would include at least three elements: a biological or morphological unit
of the infectious agent, a target unit of the potential host organism, and a
functional or probabilistic unit based on observed effect.
The biological or morphological unit of the infectious agent should be
a single viral particle, bacterial cell, or protozoan cyst. These obviously
differ greatly in the accuracy with which they can be counted. One
could, if desired, ensure that every dose administered contained one
protozoan cyst or that the average dose administered contained one
bacterial cell, but it would be very difficult to estimate the number of
particles in a small dose of virus with any accuracy. This difference
exerts a significant effect upon the choice of a probability model that
could be applied most efficiently to each of the three classes of infec-
tious agents. There is also the problem that, to the degree that one can
actually see and count morphologic units of the infectious agent, it is
frequently impossible to determine whether these are viable, in the
sense of being capable of carrying out their biological potential as infec-
tious agents.
The target unit of the potential host organism presents problems of
definition. The descriptive statistics of volunteer studies with young
adult males sometimes necessitate a retrospective definition of suscepti-
bility, as was mentioned previously. Prospective analyses require that
the target unit be redefined to include all ages and states of health among
persons in the population at risk. This definition cannot be done out of
the context of the end effect that is being observed : persons who are not
necessarily more susceptible to infection than the average may be signif-
icantly more likely than average to become ill if they are infected.
Finally, there is the problem of defining the functional or probabilistic
unit of the effect that is being observed. As was mentioned previously,
an infectious dose is one which produces infection, and infection may be
defined in terms of prolonged shedding of the infectious agent or of
development of humoral immunity against it. A pathogenic dose might
be defined as the quantity of an infectious agent which produces specific
symptoms of disease in the recipient. These definitions are apparently
straightforward, but unfortunately there are data from specific groups in
published human volunteer studies where the number of ill subjects
exceeds the number infected, based on the criteria just stated.
Given all the problems in defining the variables in the system, it seems
clear that no perfectly rigorous probability function for evaluating an
infectious dose is attainable. For other reasons discussed previously,
the calculation of a pathogenic dose apart from the infectious dose may
well be a trivial exercise. It seems reasonable to conclude on the face of
the matter that no useful mathematical model can be attained at this
time. Nevertheless, applications of the Poisson formula and its deriva-
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86 Wastewater Aerosols and Disease/Health Aspects
live binomial distribution have succeeded remarkably in comparable
situations in the past.
The distribution of infections is a quantal, all-or-none proposition, in
spite of any problems there may be in defining the variables in the
system. The Poisson formula provides a valid empiric means of analyz-
ing data involving quantal variables (17) and serves as the basis for the
multiple tube method of estimating coliform organisms in water and
wastewater on the basis of most probable number. Applications of the
Poisson distribution in quantitative virology have been well reviewed by
Sobsey (18). In its simplest derivative, the Poisson formula can provide
a point estimate of the peroral infectious dose by finding the negative
Napierian logarithm of the fraction of those challenged with a given
dose who do not become infected. Other derivatives of the formula
allow one to calculate confidence intervals and to make projections of
cumulated risk of infection after repeated small doses of an infectious
agent. An alternative approach is to calculate the dilution in a geometric
series which will cause infections in 50% of the recipients: there are
convenient procedures for computing these 50% endpoints, but the re-
sults are of limited value in prospective applications.
RISK ASSESSMENT
Earlier I mentioned some worst-case assumptions that have often
been made by others. I shall not attempt to deal with them individually
here, but I think it is important to point out that a great many hypotheses
have become common knowledge through frequent repetition, without
ever really having been tested experimentally. This is undoubtedly the
point at which to insert the standard plea for further research. I shall
depart from expectations only to the extent of suggesting that first prior-
ity be given to studying the course of peroral (rather than aerosol) infec-
tions initiated by minimal doses of enteric agents and to characterizing
the host factors that determine whether infection leads to disease.
No mathematical approach that is presently available will yield a valid
assessment of the absolute probability that someone will be infected as a
result of exposure to wastewater aerosols. Some estimates of the rela-
tive probability of infection appear possible; but it must also be remem-
bered that disease is not guaranteed to result from infection, for the
reasons discussed previously.
An important point to be made with respect to disease transmission
via wastewater aerosols is that there is probably nothing about dissemi-
nation in aerosols that enhances the pathogenic potential of an infec-
tious agent in wastewater. The infectious agents discussed here are
largely produced in people's intestines and are generally unable to multi-
ply in sewage. Therefore, the quantities of infectious agents that are
present in the sewage and might be present in sewage aerosols will
almost never exceed those that were present at the time the feces were
voided. Many factors discussed earlier and by others at this symposium
may result in reduction of pathogen levels, but there is no means by
which most pathogens might increase.
Nevertheless, there will certainly be pathogenic infectious agents in
wastewater aerosols. These are not known to be able to infect the lungs
directly, so these agents represent a threat to human health principally in
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Dean O. diver 87
that they might be trapped in respiratory mucus and then swallowed or
that they might settle on food or water and be swallowed. Either of these
hypothetical modes of transmission is relatively indirect and is probably
less efficient than contact in disseminating enteric agents. There is a
dearth of experimental or epidemiologic evidence to suggest that the
quantities of pathogens in wastewater aerosols are an imminent danger
to those exposed to them. Prudence dictates that food and water should
not be allowed to become contaminated by wastewater aerosols. On the
other hand, my classes and other visitors frequently are exposed di-
rectly to aerosols from the activated sludge aeration units and other
processes at the Madison Metropolitan Sewage Treatment Plant, and I
would not continue to take groups there (nor would the plant continue to
accept visitors) if there was any indication that illness was resulting.
CONCLUSIONS
Infectious agents of human intestinal origin, including bacteria, vi-
ruses, and probably parasite cysts, are present in wastewater aerosols
and have a hypothetical potential to cause disease. Although a single
biological unit (bacterial cell, viral particle, or protozoan cyst) of an
agent may be capable of causing an infection, the single unit of most
infectious agents almost never does produce infection, and substantial
probabilities of infection are associated only with substantial numbers
of biologic units. If infection does occur, the likelihood that disease will
result from the infection depends first on the virulence of the infecting
agent and second upon an array of host factors but probably very little
upon the size of the dose by which infection was initiated. Sewage
aerosols are probably a relatively inefficient means of transmitting en-
teric infections and are not uniquely likely to lead to disease in the public
at risk. The significance of occupational risk can best be determined by
prospective epidemiologic studies.
References
1. Darlow, H. M., and W. R. Bale. 1959. Infective hazards of water closets Lancet.
1:1196-1200.
2. Gerba, C. P., C. Wallis, and J. L. Melnick. 1975 Microbiological hazards of household
toilets: Droplet production and the fate of residual organisms Applied Microbiol ,
30:229-237.
3. Geldreich, E. E. 1978. Bacterial populations and indicator concepts in feces, sewage,
stormwater and solid wastes. In: Indicators of Viruses in Water and Food, G. Berg,
ed Ann Arbor Science, Ann "Arbor, Michigan, pp. 51-97.
4. Darlow, H. M., W. R. Bale, and G. B. Carter. 1961 Infection of mice by the respira-
tory route with Salmonella typhimurium. Jour Hygiene, 59:303-308.
5. Safe Drinking Water Committee, National Research Council. 1977. Drinking Water and
Health. National Academy of Sciences, Washington, D C.
6. Hornick, R. B., S. E. Greisman, T. E. Woodward, H. L. Dupont, A. T. Dawkins, and
M. J. Snyder. 1970. Typhoid fever: pathogenesis and immunologic control. New En-
gland Jour. Med., 283:686-691.
7. Lang, D. J., L. J. Kunz, A. R. Martin, S. A. Schroeder, and L. A. Thomson. 1967
Carmine as a source of nosocomial salmonellosis. New England Jour. Med .
276:829-832.
8. Dupont, H. L., R. B. Hornick, M. J. Snyder, J. P. Libonati, S. B. Formal, and E. J.
Gangarosa. 1972. Immunity in shigellosis. II Protection induced by oral live vaccine
or primary infection. Jour. Infect. Dis., 125:12-16
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88 Wastewater Aerosols and Disease/Health Aspects
9. Levine, M. M., H. L. Dupont, S. B. Formal, R. B. Hornick, A. Takeuchi, E. J. Ganga-
rosa, M. J. Snyder, and J. P. Libonati. 1973. Pathogenesis of Shigella dysenteriae 1
(shiga) dysentery. Jour. Infect. Dis., 127:261-270.
10 Dupont, H. L., S. B. Formal, R. B. Hornick, M. J. Snyder, J. P. Libonati, D. G.
Sheahan, E. H. Labrec, and J. P. Kalas. 1971. Pathogenesis of Escherichia coli diar-
rhea. New England Jour. Med., 285:1-9.
11 Koprowski, H., T. W. Norton, K. Hummeler, I. Stokes, A. D. Hunt, and A. Flack. 1956.
Immunization of infants with living attenuated poliomyelitis virus. J Am. Med. As-
soc., 162:1281.
12. Plotkin, S. A., and M. Katz, 1967 Minimal infective doses of viruses for man by the
oral route. In: Transmission of viruses by the water route, G Berg, ed. interscience,
John Wiley and Sons, New York. pp. 151-166
13. Katz, M., and S. A. Plotkin. 1967. Minimal infective dose of attenuated poliovirus for
man. Am. Jour. Pub. Health, 57:1837-1840.
14 Loria, R. M., S. Kibrick, and S. A. Broitman. 1974. Peroral infection with group B
coxsackievirus in the newborn mouse: a model for human neonatal infection. Jour
Infect. Dis., 130:225-230.
15. Rendtorff, R. C. 1954. The experimental transmission of human intestinal protozoan
parasites. I. Endamoeba coli cysts given in capsules. Am. Jour. Hyg. 59:196-208.
16 Rendtorff, R. C. 1954 The experimental transmission of human intestinal protozoan
parasites II. Giardia lamblia cysts given in capsules. Am. Jour. Hygiene, 59:209-220
17 Chang, S. L., G. Berg, K. A. Busch, R. E. Stevenson, N. A. Clarke, and P. W. Kabler.
1958. Application of the "most probable number" method for estimating concentra-
tions of animal viruses by the tissue culture technique. Virology, 6:27-42.
18. Sobsey, M. D. 1976. Field monitoring techniques and data analysis. In: Virus aspects
of applying municipal wastes to land, L. B. Baldwin, J. M. Davidson, and J. F.
Gerber, eds. Center for Environmental Programs, University of Florida, Gainesville.
pp. 87-96.
DISCUSSION
MR. McCABE: I would like Dr. Phair to comment on Dr. diver's
remarks about the respiratory pathway. Do you see it the same way?
DR. PHAIR: I think Dr. diver's remark is a fair generalization that
the data on inhalation of enteropathogens as a significant mechanism of
disease production are not very good.
DR. LUND: I would like to challenge that.
DR. PHAIR: Good.
DR. LUND: The highest production of virus is in the tissues of the
upper respiratory tract, and if you go through the respiratory tract to the
stomach you might bypass that area. For instance, you know in the days
of the polio epidemics, people who had their tonsils removed had a
higher risk of polio than others. I think that there might be such a thing
as bypass and it might make a difference because of it.
DR. PHAIR: Just one thing that persuades me that that is not a major
mechanism in natural infection is the finding, during the early polio
vaccine trials, that minimal doses did not result in infection in the phar-
ynx but rather in the intestine; quite large doses of the oral polio vaccine
virus did infect the pharynx and then the intestine. But it looked as
though the pharynx, in those studies, was less sensitive to virus than
the intestine.
Suport for Dr. Lund's point has been found in at least one situation
where there has been aerosolization of contaminated blood in dialysis
units. There have been hepatitis B outbreaks associated with that sort of
thing where a centrifuge, or something of that nature, broke. So it is not
unheard of, but I think I agree with Dr. diver that it is not a major risk,
except under unusual circumstances.
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Dean O. Oiver 89
DR. GERBA: In terms of aerosol transmission, if I remember the
literature correctly, individuals are susceptible to infection through aer-
osol transmission. I believe there were slides indicating that the infec-
tive dose was even lower with aerosol exposure. I don't think we should
forget that any of these, especially viruses, can be transmitted by the
respiratory route. In looking at aerosols we shouldn't exclude an organ-
ism just because it is an enteropathogen and say it can't be infective by
aerosol transmission.
In terms of infectious dose, rather than the aerosol dose inhaled,
aerosols settling out on surfaces can result in the transmission of disease
by the aerosol route indirectly by touching contaminated surfaces. I
think these things should be also taken into consideration when talking
about aerosols.
DR. CLIVER: With regard to aerosols settling on surfaces, I did
explicitly mention that. That is one of the possible routes by which these
things might be transmitted. One of our concerns is to keep the stuff off
the food.
I was not able to find anything indicating that Shigella did infect by the
aerosol route more efficiently. I did find one article on Salmonella typhi-
murium which I didn't find persuasive because I know how many Sal-
monella spp. are in aerosols in poultry slaughter plants versus a true
respiratory agent such as the ornithosis agent. We know of no outbreaks
in poultry slaughter plants where the same workmen are exposed to
these aerosols.
If they have the agent of ornithosia in their body they are going to get
a pulmonary infection, but one does not see pulmonary salmonellosis
except, perhaps, in severely debilitated people.
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90
Responses to Wastewater Exposure
with Reference to Endotoxin
Ragnar Rylander
Monica Lundholm
Department of Environmental Hygiene
University of Gothenburg
Gothenburg, Sweden
ABSTRACT
Workers at six sewage treatment plants in Sweden were the subjects, and workers at
drinking water plants were controls for an investigation attempting to evaluate the pres-
ence of clinical symptoms among workers at conventional sewage treatment plants. Tests
to determine the possible presence of a chronic infection or reaction caused by endotoxin
exposure were applied, and the number of airborne gram-negative bacteria was calculated
at various sites in the working places. Results showed that a high number of airborne
gram-negative bacteria may be present at sewage treatment plants. Gastrointestinal tract
symptoms were observed to be widespread, while fever and eye inflammation were less
frequent. Numbers of white blood cells were not increased among nonsmoking subjects. A
tendency to an increase of the IgG level was seen in subjects, as well as increased
excretion of fibrinogen degradation products in urine. As there are high levels of gram-
negative bacteria and bacterial endotoxins present in the sewage plant environment, it is
suggested that symptoms are caused by exposure to airborne endotoxins.
A previous investigation has demonstrated that workers in a sewage
treatment plant suffered from occasional episodes of chill, fever, and
malaise (1,2). In that particular plant, the sewage sludge was heat-
treated and transformed into a powder. When workers were exposed to
the dust during handling of the mechanical equipment, acute symptoms
of fever and eye inflammation appeared a few hours afterwards.
The present investigation was undertaken to evaluate the presence of
clinical symptoms among workers in conventional sewage treatment
plants. Based upon previous experience, tests to evaluate the possible
presence of a chronic infection or a reaction due to endotoxin exposure
were applied. The number of airborne gram-negative bacteria was deter-
mined at different working sites in the plants.
MATERIAL AND METHODS
The investigation was performed at six different sewage treatment
plants in Sweden. The plants incorporated indoor as well as outdoor
basins and other installations. Persons working at drinking water plants
served as controls. An interview investigation was performed among the
employees who were working in the plant at the time of the investigation
and had been employed for at least 8 months. Practically all employees
so selected participated in the investigation; only two refused.
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Ragnar Rylander and Monica Lundholm 91
The interview comprised general questions regarding length of em-
ployment, previous employments, smoking habits, and general health.
Specific questions were posed concerning the presence of workplace-
related eye inflammation, attacks of fever, and symptoms from the gas-
trointestinal tract or the skin. Blood samples were taken to determine
the number of white blood cells and their distribution, the number of
thrombocytes, and the amount of serum immunoglobulins. Fibrinogen
degradation products (FDP) were determined in urine. With the ELISA
technique, antibodies were determined against a pool of 10 common
gram-negative Escherichia coli endotoxins or against endotoxins pre-
pared from gram-negative bacterial strains isolated from sewage water.
The investigated group of employees is illustrated in Table 1. The total
material comprised interviews from 262 persons and blood samples from
236. Forty-one persons were interviewed in the drinking water plants
and 199 in the sewage treatment plants. The mean age and number of
years employed were slightly higher among personnel at the drinking
water plants. The proportion of smokers was 56% at the drinking water
plants as compared to 44% at the sewage treatment plants.
Table 1. Workers Investigated in Drinking Water and Sewage Treat-
ment Plants
Water Sewage
Interviewed N
Blood samples N
Mean age
Years employed
% smokers
41
41
47±13"
13±11
56
199
181
40±12
7±7
44
a± indicates standard deviation
The number of airborne gram-negative rods was determined using a
six-stage Andersen sampler with Drigalski agar selective for gram-nega-
tive rods. The number of bacterial colony forming units (cfu) was
counted after incubating the agar plates at 30 or 35°C during 48 hours.
In certain of the measurements, parallel samples were taken. One
sample was incubated as above, and the agar plates from the other
sample were crushed in saline and serial dilutions were prepared of the
slurry. The number of colonies was counted after incubation on Drigal-
ski agar plates.
Different species of gram-negative bacteria were identified using the
oxidation fermenting characteristics. Fermenting species were identified
using the API system. Oxidative species were identified using biochemi-
cal and immunological techniques. No determinations of pathogens
were made. The determinations of airborne bacteria were made at var-
ious working sites in the plants. Several determinations were made at
each site, and the measurements were performed on two or more work-
ing days.
RESULTS
The determinations of airborne gram-negative bacteria in different
parts of the sewage treatment plants demonstrated that the number of
colony forming units ranged from 10 to more than lO^m3 of air. The
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92 Wastewater Aerosols and Disease/Health Aspects
highest values were reported near installations where aerosolization of
the water took place, such as aerating basins and sludge pressing units.
The number of colony forming units at sedimenting basins was low. In
the drinking water plants, the number of bacteria was very low.
The gram-negative bacteria were mainly various strains of Enterobac-
ter, Klebsiella, and Pseudomonas spp. The proportion of E. coli was less
than 10% in most of the measurements, and in many of the samples E.
coli could not be detected.
Comparisons between the number of viable organisms as detected by
the Andersen sampler directly (cfu) and the number found after crushing
the agar plates are reported in Table 2. The number of bacteria detected
directly comprised less than 1% of the number found when the agar
plates were crushed.
Table 2. Number of Viable Airborne Gram-Negative Rods by Direct
Outgrowth on Andersen Sampler Agar Plates (cfu) and After
Crushing and Suspending Slurry in Liquid (Dispersed)
cfu 2 7±(0.6)<"
dispersed 464
Vindicates standard deviation
The symptoms reported by the employees are seen in Table 3. The
proportion of workers reporting fever and symptoms from the eye or the
skin was slightly larger among the sewage treatment workers.
Table 3. Symptoms Reported by Workers in Drinking Water and
Sewage Treatment Plants
Subjective symptoms (%)
Water Sewage
Employees N
fever
eye
skin
diarrhea
41
0
2
2
2
199
2
6
8
32
Concerning diarrhea or acute gastrointestinal symptoms, 32% of all
the workers in the sewage treatment plants reported such symptoms, as
compared to 2% in the drinking water plants. These symptoms were
reported to occur particularly in connection with dirty working opera-
tions such as cleaning the bottom of basins or repairing pumps. They
were more frequent when the employee returned to work after a pro-
longed absence, such as after holidays. The frequency of symptoms
varied greatly—some reported that the symptoms were present a few
times per year or less and others reported that they occurred almost
every month.
The gastrointestinal symptoms developed a few hours after the partic-
ular exposure, lasted throughout the night, and usually disappeared the
following morning. They were not accompanied by increases in fever or
a headache.
Determinations of the number of white blood cells (Table 4) showed
that among the employees at the drinking water plants, smokers had an
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Ragnar Rylander and Monica Lundholm 93
increased number as compared to nonsmokers (p < 0.1%). No differ-
ence was found between the nonsmokers in drinking water and sewage
Table 4. Number of White Blood Cells (x KF/ml) Among Workers in
Drinking Water and Sewage Treatment Plants
Nonsmokers Smokers
Water 5.6±1.2a 8.9±2.7
Sewage 5.5±1.4 7.2±2.1
"± indicates standard deviation
treatment plants. The number of white blood cells among smokers in
sewage treatment plants was slightly lower than among smokers in
drinking water plants (p < 1%). No differences were noted with relation
to the distribution of the various types of white blood cells.
Regarding thrombocytes, no differences were found between non-
smokers and smokers or between workers in water and sewage plants.
Table 5 reports the amount of serum immunoglobulins among the
investigated employees. Nonsmoking employees in sewage treatment
plants had slightly higher values of IgG, IgM, and IgA as compared to
nonsmokers in drinking water plants. The differences were, however,
not statistically significant. No significant differences were found be-
tween the other groups of employees.
Table 5. Serum Immunoglobulins (mg/ml) Among Workers in Drinking
Water and Sewage Treatment Plants
IgG
igM
igA
Water
Nonsmokers
11.4±3.1a
1.3±07
21±1 0
Smokers
11.7±2.4
1.4±05
21+08
Sewage
Nonsmokers
13.0±3.4
1.8±0.8
2.3±09
Smokers
12.0±3.0
1.6±07
2.2±1 0
a± indicates standard deviation
Table 6 reports the proportion of workers having an excretion of FDP
in excess of 10 mg/1 of urine. Among workers in drinking water plants, a
larger extent of the smokers had increased values (p < 0.1%). For
nonsmokers, the extent of employees with an increased level of FDP
was higher in the sewage treatment plants (p < 0.1%).
Regarding antibodies to E. coli endotoxin or endotoxin from the gram-
negative bacteria found in the sewage treatment plants, no differences
were detected between serum antibody levels among workers in drink-
ing water and sewage treatment plants.
Table 6. Percent of Workers in Drinking Water and Sewage Treatment
Plants with Urine FDP Higher Than 10 mg/1
Nonsmokers Smokers
Water 6 22
Sewage 33 24
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94 Wastewater Aerosols and Disease/Health Aspects
COMMENTS
The present investigation demonstrates that a large quantity of air-
borne gram-negative bacteria may be present in the sewage plant envi-
ronment. The bacteria species were mainly of the kind normally present
on vegetation. The same species are found in other industries where
organic material is aerosolized, such as in cotton mills.
The data further demonstrate that determinations of the number of
airborne viable organisms made using a particle impactor technique un-
derestimate the true number of organisms by a factor of 102 to 103. This
error is important if one wants to relate effects observed among the
exposed workers with any parameter related to the number of bacteria
such as the amount of toxins.
The reason for the discrepancy in bacterial numbers is that, with the
Andersen sampler, a count is made of the number of particles on agar
plates from which bacteria grow. Each particle can consist of a single
bacterium (impacting mainly on the last plate in the sampler) or aggre-
gates of bacteria (impacting mainly on the first plates). Thus, the number
of colony forming units is not always related to the true number of
airborne viable organisms in the sample of air studied.
The gram-negative bacteria present in the air of the sewage treatment
plants contain capsular lipopolysaccharides—endotoxins. These may
cause a variety of biological effects, even at low levels of exposure. No
extensive determinations of the amount of bacterial endotoxins in the air
of sewage treatment plants have been performed. Determinations of
endotoxin levels in treated wastewater sometimes used for irrigation or
cleaning purposes demonstrate levels of around 5 ^g/ml. If a quantity
equivalent to 1 ml were to be inhaled during a few hours, the endotoxin
dose required to produce fever would be exceeded by at least five times.
Subjective symptoms and eye inflammation among workers exposed
to products of sewage were reported already by Rammazzini (3).
Symptoms from the gastrointestinal tract were present among a high
proportion of the workers in the sewage treatment plant. Such symp-
toms were not reported in the previous investigation on workers in the
plant with sewage dust (1). Other symptoms such as fever and eye
inflammation found in the sewage sludge drying plant were less frequent
among workers investigated here.
A possible explanation for this difference in symptoms is related to
the particle size distribution of the aerosols in the two types of sewage
plants. In the plant with sewage dust, the particles were small, which
allowed for penetration down into the alveolar region of the lungs. In the
plants investigated here, the largest amount of particles was of a large
size range, demonstrated by the fact that the majority of the particles
impacted on the first agar plates in the Andersen sampler. This size
favors deposition in the upper part of the respiratory tract with subse-
quent rapid clearance down into the gastrointestinal tract. Further stud-
ies are required to verify this hypothesis.
Gastrointestinal symptoms have also been found in a study on Danish
sewer workers and in a small study among workers exposed to dust and
sludge in a composting plant (4). In that plant, sewage and household
garbage were milled together and subsequently stored until biological
-------
Ragnar Rylander and Monica Lundholm 95
degradation occurred. Workers were exposed to large numbers of gram-
negative bacteria mainly originating from the household garbage.
From a clinical point of view, the symptoms are different from those
caused by infections of a viral or bacterial origin.
The number of white blood cells was increased among smokers as
compared to nonsmokers. This is in accordance with findings from pre-
vious investigations. The sewage plant environment did not affect the
number of white blood cells among nonsmokers. This indicates that, at
least among the group observed, an important indicator of infection
could not be demonstrated.
With relation to immunoglobulins, only a tendency to an increased
IgG level was found among nonsmokers in sewage treatment plants as
compared to nonsmokers in the drinking water plants. The previous
investigation on workers exposed to sewage sludge dust demonstrated a
significant increase in the IgG levels (2). The exposure was thus prob-
ably less among the group of workers investigated here.
The extent of workers having an increased excretion of FDP was
influenced both by smoking and the sewage plant environment. An in-
creased excretion of FDP indicates a general inflammatory response
somewhere in the body. It is conceivable that a continuous injury to the
lung due to inhaled tobacco smoke could be the reason for the increased
amount of FDP excreted among smokers. The increase among non-
smoking workers in the sewage treatment plant also indicates an inflam-
matory response although the site of action cannot be determined.
In parallel to this it is worth noting that increases in the serum trans-
aminase levels of workers in sewage plants have been observed in inves-
tigations from the United States and Sweden. This suggests that the liver
may be involved in the inflammatory response after exposure in the
sewage work environment. Systematic observations in relation to exact
exposure conditions at work and other factors which influence transami-
nase levels such as alcohol consumption are underway to further eluci-
date the significance of these findings.
Epidemiological studies can never yield information on casual rela-
tionships between an observed biological phenomenon and one particu-
lar factor in a complex environment. Also, the exposure conditions for
workers investigated here are not known in detail. Any suggestions as to
the agent responsible for the observed symptoms among sewage plant
workers must therefore remain hypothetical.
In view of the large amounts of gram-negative bacteria and bacteria
endotoxins present in the sewage plant environment, it is suggested that
the symptoms are caused by exposure to airborne endotoxins. The ef-
fects that appear are thus to be considered as toxic effects rather than a
traditional infection.
Endotoxins are known to act as general mitogens which could explain
the slight increase in IgG immunoglobulins found among sewage treat-
ment workers (5). Exposure to endotoxins will also cause polymorpho-
nuclear leukocytes to appear on epithelial surfaces such as the eye, as
seen in sewage dust workers. In cotton mills where endotoxin is present
in the air, a similar invasion of leukocytes takes place in the airways
(6,7).
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96 Wastewater Aerosols and Disease/Health Aspects
Exposure to large amounts of endotoxins could also explain the fever
reactions among workers exposed to sewage dust and diarrhea among
the workers in conventional plants. The liver detoxifies endotoxins, and
it is feasible that increased burdens of this substance may be reflected by
increased transaminase levels in the serum just as is the case after
alcohol consumption, for example.
Large numbers of airborne gram-negative bacteria have also been
demonstrated in cotton mills (8). The exposure conditions there differ
from those in the sewage treatment plants in that the workers are con-
stantly exposed to a high level over the whole week. Acute symptoms in
the form of fever and malaise are, however, found among cotton mill
workers when they initially start working in the mills (mill fever). This
symptomatology corresponds to the effect seen among workers in the
sewage dust plant.
In the present study, no investigation was made on the presence of
precipitating serum antibodies against different microbiological agents
present in the sewage treatment plant environment. However, no symp-
toms were reported which indicate that the effects would be an allergic
type response. Antibody liters against E. coli endotoxin or endotoxin
from the sewage plant gram-negative bacteria were not elevated among
sewage treatment workers as compared to workers in the drinking water
plant. This is in accordance with previous investigations which demon-
strate that endotoxins are not very potent antigens and produce an im-
mune response which is only of a relatively short duration.
The results from the present investigation cannot serve to judge the
risk for the development of some type of chronic disease after working
in a sewage water treatment plant for several years. As a matter of
principle, however, an exposure at work which causes both acute clini-
cal symptoms and systemic effects should be avoided, even if at present
it cannot be demonstrated that chronic effects will eventually appear.
References
1. Rylander, R., K. Andersson, L. Belin, G. Berglund, R. Bergstrom, L. Hanson, M.
Lundholm, and I. Mattsby. 1977. Studies on humans exposed to airborne sewage
sludge. Schwiezerische Medizinische Wochenschrift, 107:182-184.
2. Mattsby, I., and R. Rylander. 1978. Clinical and immunological findings in workers
exposed to sewage dust. J. Occup. Med. 20:690-692.
3. Rammazzini, B. 1964. Diseases of the Workers. (De Morbis Artificium, anno 1713.)
Hafner Publishing Company, New York.
4. Lundholm, M., and R. Rylander. Submitted for publication Bacteriological health
hazards for compost workers—a case report. J. Occup. Med.
5. Wolff, S. M. 1973. Biological effects of bacterial endotoxins in man. In: Bacterial
Lipopolysaccharides, E. H. Kass and S. M. Wolff, eds. Chicago University Press,
Chicago, pp. 251-256.
6. Merchant, J. A., J. Lumsden, K. H. Kilburn, et al. 1973. Dose response studies of
cotton textile workers. J. Occup. Med., 15:222-230.
7. Rylander, R., and M.-C. Snella. 1976. Acute inhalation toxicity of cotton plant dusts.
Brit. Jour. Ind. Med., 33:175-180.
8. Rylander, R., and M. Lundholm. 1978. The bacterial contamination of cotton and
cotton dust and effects on the lung. Brit. Jour. Ind. Med., 35:204-207.
DISCUSSION
DR. DEAN: Some of your data indicate that the sewage treatment
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Ragnar Rylander and Monica Lundholm 97
plant is insulting the workers lungs in much the same way that smoking
does. Is this an oversimplification?
DR. RYLANDER: I think at this stage I would be limited to saying
that the body is insulted so that an inflamatory response occurs, but we
do not at the present know if this really comes from the lungs. Otherwise
you are correct and there is an insult.
DR. PHAIR: In the initial plant where they dried the sludge and
there was dust, were there any respiratory symptoms at all in the work-
ers similar to what you see in farmers exposed to farm dust?
DR. RYLANDER: Unfortunately, we were not able to measure
those. The whole study in that plant was of an acute nature because they
were going to close it down due to a malfunction of the equipment. We
had to rush there and do the study in about a month's time and we never
had the opportunity to come back again.
If I may throw out a hypothesis or two, if we were ever going to go
back to the similar plant again, I would certainly look at respiratory
function measurement and I would particularly pay attention to diffu-
sion capacity measurements because there are studies from other envi-
ronments where people have been exposed to endotoxins and gram-
negative bacteria which clearly show that 4 to 12 hours after the expo-
sure there is a decrease in diffusion capacity, which returns to normal
about 24 hours later.
SPEAKER: Is it possible that working habits of sewage treatment
plant workers in Sweden are different from the working habits of work-
ers in the United States? For instance, many times I have visitors in my
plant and they ask me where the workers are because, many times, they
don't see people in my plant. We may have operators and maintenance
people on duty but if you walked around my building you wouldn't see
the people. Now, is that the case in Sweden or are those people exposed
to the tanks and filters for greater periods of time?
DR. RYLANDER: That is a very important question. By and large, I
would say that the working conditions do not differ. We see the same
thing, that is, if you walk into a plant it could be entirely empty and you
might not see anyone around to draw blood samples from. This explains
some of the irregularities in the symptoms because, clearly, we are
facing a situation where the workers are not reacting to the general
environment like in the cotton mills but they are reacting toward specific
situations in that working environment. One of our large goals in this
project is to try to help manufacturers to define where these danger
spots are. Adequate protection can then be taken by both sides.
Now, another problem relates to the finding of these symptoms and
this very much depends on how you phrase your questionnaire. For
example, you may go up to a worker and ask him (and this was an
experience that we had in the sludge dust plant), "Do you ever have a
disease?", and he may say no, or, "Are you ever absent from work
because you have a medical problem of some kind?", and he may say
no. Then we may say, "Do you have a fever in the afternoon?"; he
says, "Yes, I have fever in the afternoon and then I go and take a cold
shower."
MR. HAYMES: I agree that the smoke is a critical variable. First, I
would like to ask you how you classify smokers and nonsmokers?
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98 Wastewater Aerosols and Disease/Health Aspects
DR. RYLANDER: They were just classified as smokers and non-
smokers at that time. We felt that the material and the actual positive
findings were too limited to actually allow us to go into a deeper
analysis.
MR. HAYMES: If smoking turned out to be nonconfounding, given
that the proportions of smokers in both of those groups were not signifi-
cantly different, and if you pull the information in each group, water
versus sewage, might you have gotten a significant type of finding? I
would like to ask if you have tried it by pooling the analysis?
DR. RYLANDER: No, as a matter of fact, we haven't yet, but that
is a very good suggestion and we could probably do that.
MR. JAKUBOWSKI: Have you considered that we all have large
numbers of gram-negative organisms present in the intestines and, con-
sequently, we have endotoxins. How can the infection of what I would
assume would be a relatively small amount of additional endotoxins
result in the production of the symptoms of diarrhea?
DR. RYLANDER: I don't think I am prepared to answer in immu-
nological detail but, generally speaking, we do have a lot of gram-nega-
tives and endotoxins. But those are mainly the E. coli. We have very
little of the type of gram-negative bacteria that you find in the sewage
plant environment, which is Klebsiella and Enterobacter which derive
from the vegetation. Now, immunity against endotoxin is a crossover in
a sense because, if you have immunity against E. coli, you have a
certain immunity against others as well. It is certainly lower, or less,
which means that once you exceed a certain dose you may develop
symptoms. This is quite in contrary to the allergic response where you
develop a response even to very minute doses of the antigen. In this
case, I am suggesting that you need to dose a real group and then anyone
who receives that dose will react. We have been trying to discuss with
our ethics committee the possibility of running an experiment with peo-
ple who would swallow the endotoxin to see if they get diarrhea, but the
committee has not authorized it.
DR. LUE-HING: If I recall, you disputed current information about
people who are working in enclosed areas. Could you give details?
DR. RYLANDER: A general answer would be that there is no dif-
ference. It is entirely dependent upon the ventilation system. Enclosed
treatment plants generally had a very high quality in the air because they
invested a lot on ventilation, whereas some of the outdoor plants had
quite high levels. There was no correlation between symptoms and in-
door or outdoor areas.
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99
Health Effects of Nonmicrobiologic Contaminants
James B. Lucas
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio
ABSTRACT
The nonmicrobiologic contaminants of wastewater aerosol have received scant attention
in comparison to the rather intensive efforts made to characterize airborne microbiologic
hazards. While this dichotomy is normal in view of public concern over potential infec-
tious disease transmission, appreciation is slowly being gained that toxic gases and myriad
chemicals, both organic and inorganic, may also pose a significant hazard to wastewater
treatment workers and potentially to the general public in surrounding areas. A number of
acute disease episodes have already been reported as affecting occupationally-exposed
treatment plant personnel. Of more concern is the potential for chronic long-term effects
from repeated low-level exposure—exposure which may also have conceivable impacts
beyond plant confines. This paper discusses the known toxic effects of substances which
have been identified in various wastewaters or those which may be formed by the interac-
tion of chemical pollutants. Emphasis is placed on the respiratory route of entry and upon
the effects of systemic absorption. This paper seeks to put the general environmental
exposure hazard into a rational perspective based upon occupational experiences.
I am sure it is obvious to all that my discussion cannot begin to cover
every conceivable nonbiologic substance contained in wastewaters
which is possibly hazardous to man via the respiratory route. The occu-
pational hazards of sewer workers have long been recognized. Infec-
tious hazards aside, men working in sewer systems are commonly liable
to accidents causing physical injury, to drowning, poisoning, and to
gassing accidents, including the explosion of air containing CtU or gaso-
line vapor. Dr. Donald Hunter, the late Dean of English Occupation
Medicine, has aptly described sewer workers as "generally of small
build, cheery disposition, and almost fearless. What attracts them to the
job is the certainty of continued employment" (1). Obviously, persons
working at wastewater treatment plants are subject to substantially the
same risks as those actually working in the connector and interceptor
sewers. The fact (or possibility) that some of these same risks are faced
by the general population living in the vicinity of wastewater treatment
plants is far more nebulous and has only come under close study in
recent years.
I will try to confine my remarks to the pathophysiologic events asso-
ciated with identified hazards and real world problems which might, at
least on rare occasion, be found in the waste treatment plant environ-
ment. I will not try to be encyclopedic or even reasonably complete in
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100 Wastewater Aerosols and Disease/Health Aspects
my compendium—for more likely than not the next hazardous episode
achieving notoriety will be due to some previously unrecognized
contaminant.
Since we are concerned with substances entering the body via the
respiratory tract, I would like to take a few minutes to review and
summarize our anatomic and physiologic knowledge of this vital system.
The physiologist defines two types of respiration. The first is external
respiration, i.e., the act of or mechanisms of breathing. The second, or
internal respiration, refers to cellular respiration. This encompasses the
utilization of O2 at the cellular level with the production of energy,
growth, and the synthesis of cellular products such as enzymes and
hormones. In carrying out the functions, many waste metabolites are
formed, for example CO2, which are removed by the lungs. Nongaseous
wastes are, of course, primarily removed by the liver or kidney.
Blood serves as the medium of conveyance between the lungs and the
tissues. Whole blood is about 45% comprised of red blood cells which
contain hemoglobin. Each molecule of hemoglobin can combine with
two atoms of oxygen and carry them to the tissues. The noncellular
component of blood, the serum, transports waste CO2 as HCO3 to the
lung where the enzyme carbonic dehydrogenase converts the ion to
water and gaseous CO2.
The nose is the normal entry point for the air we respire and also
serves as the organ for the special sense of smell. The nose serves as a
filter and also warms and moistens air. Large particulates are trapped
here, and highly soluble compounds may dissolve in the mucous coating
and result in irritation.
The nose empties into the throat or pharynx, the muscular organ
common to both the respiratory and alimentary tracts. Toward the front
of the lower part of the pharynx is the larynx, through which air passes
into the trachea. The entry to the larynx is guarded by the epiglottis, a
valve, which prevents the entry of food or drink into the lower respira-
tory tract. The trachea or windpipe is about 5 in long and is made of
semirigid rings of cartilage and smooth muscle. At its lower end it di-
vides into two main bronchi, each of which enters the substance of the
lung before bifurcating repeatedly into smaller and smaller divisions.
There are 13 reduction divisions in all, and when inverted, the entire
bronchial structure resembles a tree with the trachea serving as the
trunk. The smallest divisions are called bronchioles and terminate into
alveolar ducts which are lined with small sac-like structures known as
alveoli. Each duct and associated alveoli resembles a bunch of grapes.
This terminal structure consists of only a single layer of squamous epi-
thelial cells since supporting structures, cartilage, and muscle, are lost
after the first five or six divisions. Each alveolus is surrounded by a
capillary network which is itself only one endothelial cell thick. It is
between these two cell layers that actual gas exchange occurs. Finally,
surrounding the lung and maintaining its general structure is a shiny
membrane known as the pleura. The lungs are enclosed in the thoracic
cavity or chest cage, which is made up of the ribs and associated mus-
cles. The inner surface of the chest cage is also lined with pleura, and
normally no space exists between the surfaces of the lung and thorax;
the opposing pleurae are held together by surface tension.
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James B. Lucas 101
The normal adult usually breathes about 16 to 18 times/min, and each
breath carries about one-half liter of air. However, only that air reaching
the alveolar ducts and alveoli, approximately 360 ml, is available for
gaseous exchange; that air filling the trachea, larynx, nose, etc. compris-
ing dead space. Toxic materials in the air may enter the respiratory
system as gases, vapors, fogs, fumes, or particulates and cause damage.
Adverse effects result from one of a number of potential mechanisms
(Table 1), and it should be remembered that these types of effects are
not mutually exclusive; for example, an agent may act both as an irritant
and also produce systemic intoxication due to absorption.
The simple asphyxiants prevent adequate oxygen from reaching the
lungs. They are essentially inert in the physiologic sense but can cause
death when men are exposed to them in closed spaces. Most of them are
heavier than air and accumulate, displacing the lighter oxygen. Espe-
cially dangerous in regard to these agents are tanks, tank cars, ship
holds, fermentation vats, old mines, and the like. Deep wells in waste-
water treatment plants may pose a similar hazard. The simple as-
phyxiants are important because they are common, and they can over-
come men quickly; artificial respiration is lifesaving if begun
immediately. The symptoms of oxygen lack are given in Table 2.
Chemical asphyxiators act even in the presence of oxygen by interfer-
ing with oxygen transported by the red cells (CO) or by poisoning the
enzyme system required for cellular respiration (cyanide).
To a great extent, respiratory tract irritation depends upon the solubil-
ity of the material. Highly soluble gases and substances dissolve in the
mucus membrane lining of the nose and throat resulting in upper respira-
tory tract irritation. In higher concentrations, this may be noticed almost
Table 1. Types of Respiratory Responses
Mechanism Example(s)
Asphyxia:
Simple Methane, N.,, He,, Ha, CO2
Chemical Cyanide, CO, HjS
Irritation NHb, CI2, phosgene, SO2, NOj
Absorption:
Systemic toxins Cd, benzene, Hg, trinitrotoluene
Anesthetics Chlorinated hydrocarbons, xylene, trichloroethylene
Deposition:
Pneumoconioses Silica, coal dust, asbestos
Benign pneumoconioses Sn, Ca, Ba
Allergy (immunologic):
Immediate (asthma) Wood and gram dusts, enzymes,
toluene diisocyanate, amino-
ethyterhanolamine
Hypersensrtivity pneumonitis Fungal spores growing in hay,
cork, bark, wood pulp,
compost, etc.; protein materials
Pharmaoologic (nommmunologic) Byssinosis, flax
Infection Psittacosis, anthrax, viruses?
Neoplasia:
Lung Bis-2-chloromethyl ether, Ni, As
Other sites Vinyl chloride, benzkjine
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102 Wastewater Aerosols and Disease/Health Aspects
Table 2. Symptoms of Oxygen Deprivation
Oxygen Concentration (%) System(s)
21 Normal
12-14 Increased respiration and pulse,
decreased coordination
10-12 Giddiness, cyanosis
8-10 DeathinSmin
4 Coma in 40 sec, convulsions,
respiratory paralysis, death
immediately. Upper tract irritation is almost always accompanied by eye
irritation as the materials dissolve in the fluid coating the conjunctival
membrane of the eye. These are among the most common complaints in
the occupational setting. Less soluble gases result in irritation of the
deeper structures of the lungs. For example, phosgene may cause no
symptoms for several hours after exposure but may then be manifest by
severe irritation as the damaged alveoli permit an influx of fluid from the
vascular system. This is termed pulmonary edema and is quite serious.
A second effect from this class of agents is chemical pneumonia result-
ing from the infiltration of cellular elements, particularly white blood
cells, and fluid into the alveoli. Very poorly soluble substances may pass
directly into the blood stream and result in systemic poisoning or anesth-
etic effects if the agent can cause central nervous system depression.
Thus, insoluble gases have little or no effect on the organs of respiration
but may produce severe systemic toxicity. Several of the most impor-
tant of these gases are described in Table 3. It is worth noting that
several of these are metalloid hydrides.
Let us turn our attention briefly to the potential problem of allergy.
Allergy has been defined as a modified response to a substance and
usually implies an adverse response as opposed to a protective or bene-
ficial one. The development of respiratory allergy depends to a large
extent upon the presence of certain poorly understood personal factors
which appear to be genetically determined. Thus, for any given expo-
sure only some persons will become allergic to the substance. About
15% of our population, called atopies, commonly develop allergic respir-
atory sensitivities. This tendency usually manifests itself early in life,
often in infancy, and usually as hay fever and/or asthma. It is true,
however, that some persons may not manifest sensitivities until later in
life. It is also true that predisposed persons will vary widely in the
concentration of allergen and number of exposures required to induce
allergy; some persons require years of exposure and others only a single
exposure. However, the critical point is that once allergic induction has
occurred, i.e., once a person has become sensitive to a substance, future
exposures to only extremely minute amounts are sufficient to provoke
allergic symptoms. Thus, the allergic response is largely dose independ-
ent. Exposures sufficient to cause symptoms are usually far less than
those required originally to induce the allergic state. Thus inhalant al-
lergy is a serious matter which often requires a change in occupation
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James B. Lucas 103
when the substance is a chemical or even a move to another area of the
country when the offending materials are botanic in origin.
Unlike allergic contact dermatitis, where the allergen is usually a
small and simple molecule, most inhalant allergens are large and com-
plex proteinaceous substances, often pollens, spores, molds, or organic
dusts, i.e., materials of natural origin. Since enormous quantities of
bacterial and mycotic organisms may grow in drying sludge, there may
be some potential hazard to workers and conceivably to other persons in
the neighborhood. However, these microorganisms are by no means
exclusively associated with sludge and are found widely in our general
environment. Therefore, it is not an easy matter to incriminate dried
sludge or compost as causative in the sporadic occurrence of such a
common disease as asthma. While respiratory allergy is usually due to
organic dusts, it is conceivable that aerosolized liquids containing appro-
priate allergens might result in sporadic allergic problems, although this
seems quite rare.
Four groups of contaminants are reported to occur commonly in typi-
cal sewer off-gas: group I, CO2; group II, solvents and other volatile
oils, including chlorinated hydrocarbons; group III, H2S; and group IV,
sulfides, alkylamines, and aldehydes (2). The concentration of CO2 com-
monly runs 2,000 to 12,000 ppm; the solvents about 500 ppm; H2S up to
15 ppm; and the group IV compounds 0.01 to 0.05 ppm. CPU has been
reported at levels of 41 to 460 ppm in a typical modern wastewater
treatment plant (3). The level of all these pollutants shows great day-to-
day and even hour-to-hour variation in concentrations.
CO2 is a simple asphyxiant, and levels of 15,000 ppm begin to result in
some physiological changes such as increased respiration. A concentra-
tion of 10% (100,000 ppm) can result in sufficient oxygen deficiency to
produce unconsciousness and death. The current federal standard is
5,000 ppm. CO2 is a heavy gas which accumulates at low levels and
displaces air. Generally, adequate ventilation is all that is required to
sufficiently protect workers.
Both individuals and industries contribute unintentionally (or other-
wise) gasoline, fuel oils, spent motor oils, and other lubricants to our
i
Table 3. Important Highly Toxic, Relatively Insoluble Gases
Agent Formula
Phosphine PHa
Stibine SbH.,
Carbon disulfide CSj
Nickel carbonyl Ni(CO)4
Arsine AsHa
Source(s)
Phosphide insecticides
Phosphorus explosives
Acids acting on antimony
Rayon, cellophane
manufacture
Nickel refining
Metal smelting and
refining
Effect(s)
Odor of decaying fish
CMS depression
Pulmonary edema
Cardiac arrest
Hemolytic anemia
CMS depression
Psychosis
Atherosclerosis
Pulmonary edema
Hemorrhage
Hemolytic anemia
Jaundice
Pulmonary edema
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104 Waste water Aerosols and Disease/Health Aspects
sewers. These hydrocarbons float and are relatively immiscible. Explo-
sion is an obvious hazard from these volatiles. Gasoline is irritating to
the skin, eyes, and mucous membranes, and the vapors may act as a
central nervous system depressant, with very high concentrations caus-
ing coma and respiratory failure. Hemorrhage of the pancreas, fatty
degeneration of the liver, and degeneration of the kidneys may also
occur (4). The composition of gasoline is so varied that a single federal
standard is not possible; n-heptane and n-hexane are usually present as
major ingredients, however. The latter compound has also resulted in
peripheral neuropathy as an effect of chronic exposure. The federal
standard for both compounds is 500 ppm (5). The 1978 American Con-
ference of Governmental Industrial Hygienists (ACGIH) lists a thresh-
old limit value (TLV) of 400 ppm for n-heptane and 100 ppm for n-
hexane as a result of the peripheral neuropathy that has been observed
(6). The aromatic hydrocarbon content is considerably more important
from a health standpoint than are the aliphatics. Benzene may be pres-
ent in gasoline in concentrations of up to several percent and is also
widely used as an industrial solvent. Acute benzene exposures, as with
most hydrocarbons, result in central nervous system depression. Death
may occur from large acute exposures as the result of ventricular fibril-
lation. Chronic exposures are also well-documented, and benzene is a
myelotoxic agent, i.e., it affects the formation of various blood cells in
the bone marrow. Blood counts may decrease dramatically and fatal
aplastic anemia ensue. It is now generally accepted that benzene is
leukemogenic, and the evidence that acute myelogenous leukemia may
result is now quite convincing. Recent work has also demonstrated an
increased incidence of chromosomal aberrations in association with
benzene myelotoxicity (7). These changes may last for years following
cessation of exposure and may give rise to the leukemic clones which
cause the resulting leukemia. Organolead and antiknock compounds
may also represent serious hazards. Tetraethyl and tetramethyl leads are
used singly or together as antiknock compounds in gasoline. Both alkyl
leads may rapidly penetrate the skin without local reaction and/or may
enter the body via inhalation of vapor. The effect may be lead encepha-
lopathy with hallucinations, delusions, convulsions, and toxic psy-
chosis. An early fatal outcome may result. Recovery may be very slow
but is usually complete. The federal standard for tetraethyl lead is 0.075
mg Pb/m3 and 0.070 mg Pb/m3 for the methyl compound (5).
Cd, Pb, and Hg levels in blood, feces, hair, and urine have been
examined in persons living in proximity to Chicago's John Egan waste-
water treatment plant (8). Preexposure levels were compared to those
found after the plant was fully operational. No statistically significant
increases in metal content were seen in any of the fluids or tissues
analyzed. Surprisingly, some metal values significantly declined during
the exposure period; i.e., fecal Cd and Pb, hair Cd and Hg, urine Pb and
Hg, and blood Hg. Five of these decreases were significant at the p
< 0.001 level. While there is no apparent explanation for these declines,
other than perhaps some differences in sample storage times or analysis
by different personnel, these results are, to say the least, reassuring, and
the data gives absolutely no support to any adverse sewage treatment
plant effect. This was anticipated since drinking water, food, and to-
-------
James B. Lucas 105
bacco represent the major pathways of exposure; even in heavily indus-
trialized areas the general public will have only relatively trifling expo-
sure via air. Thus, shifts in human metal content are far more likely to be
impacted by changes in dietary or tobacco habits or even seasonal varia-
tions in water drinking.
H2S, or sewer gas, is a serious risk to life whenever circumstances
permit high concentrations to develop. This hydride may occur when-
ever acidic solutions contact sulfides or from the anaerobic putrefaction
of sulfur-containing proteins. It is also found near volcanoes and in lead,
gypsum, coal, and sulfur mines where it is called "stinkdamp." Natural
gas from some oil fields, especially those associated with high sulfur
content crudes, may contain dangerously high concentrations. In addi-
tion, it is also found along with CS2 in emissions from the viscose
process used to manufacture rayon and cellophane. Being heavier than
air, the gas tends to accumulate in low pockets, mines, wells, etc. where
there is inadequate ventilation. At high concentrations, its toxic action is
virtually as rapid as any agent known; affected individuals drop and die
almost instantaneously. It is a leading cause of death in the workplace.
The action is comparable to cyanide with immediate respiratory paraly-
sis. Both compounds are potent inhibitors of cytochrome oxidase (9).
Typically, would-be rescuers are sequentially overcome trying to save
already unconscious fellow workers. In the past decade, a number of
such multiple tragedies have been reported: seven worker deaths in a
Chicago tannery (9), six in a Maine tannery (9), 11 in the holds of small
fishing vessels (10), six in a rendering plant in Ohio (11), and farm
workers overcome following the agitation of liquid manure systems (12).
Sulfmethemoglobin is formed from the normally small amount of meth-
emoglobin present in the blood, but this is not important pathologically
in acute poisoning cases. In fact, agents enhancing methemoglobin for-
mation such as NaNO2 are protective in H2S poisoning, since the sulf-
methemoglobin complex is tolerated and spontaneously decays with a
2-hour half-life to oxyhemoglobin and an unknown sulfur compound.
Low doses are irritant and cause symptoms appropriate to upper res-
piratory tract irritation, i.e., photophobia, sneezing, tearing, and sore-
ness of the mouth and throat. Exposures to 1,000 ppm may be rapidly
fatal, and some men may develop serious symptoms after prolonged
exposure to less than 100 ppm. Chemical conjunctivitis has frequently
been reported at levels below 20 ppm and the ACGIH recommends a
TLV of 10 ppm (13). The Federal Occupational Safety and Health Ad-
ministration sets 20 ppm as the acceptable ceiling concentration but has
not established an 8-hour time-weighted average. The lower limit for the
odor threshold is 0.02 to 0.03 ppm. Above 30 ppm the characteristic
rotten-egg odor is perceived as sweet, and above 100 ppm the sense of
smell is rapidly abolished. Olfactory fatigue also occurs with prolonged
exposure to lower levels, and the odor cannot be relied upon as a warn-
ing, especially of high concentration. H2S is not an accumulative poison;
and overcome individuals, once revived by resuscitative measures, have
no late sequelae. Hence, prompt recognition may be lifesaving. Air-
supplied respirators should be available wherever there is any potential
for H2S accumulation. In this way, the multiple casualties so commonly
reported for this agent may be avoided.
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106 Wastewater Aerosols and Disease/Health Aspects
Persons exposed to water containing pollutants may respire volatile
components contained in the polluted solution. This is an area that has
received scant attention to date, but it is evident that substantial expo-
sures may ensue; the Louisville episode (14) is a prime example. It is
possible to calculate theoretical air concentrations from the physical,
chemical, and thermodynamic properties in question (15). These calcu-
lations are based on the gas laws and apply to stable systems under
equilibrium conditions. Unfortunately, ideal equilibrium conditions do
not exist in the real world. Nonetheless, it is of some interest to compare
the idealized results with some actual measurements we recently made
in a plant whose well had become contaminated with benzene from a
nearby chemical landfill (Table 4).
Table 4. Comparison of an Estimated Benzene Concentration with
Measurements Made in an Actual Exposure Situation
Location/sample
Hypothetical estimation (15)
Plant tap water
Plant shower room with water running
Near plant wash basin with tap running
General workroom air during normal operations
Water
concentration
(ppm)
10.0
91
—
—
—
Vapor
concentration
(mg/m3)
0966
—
234
1.2
0.1
Using the commonly applied figure of 10 m3 for the ventilation rate
during a normal workday and assuming that all the benzene inhaled is
absorbed by the lungs, one can calculate an approximate daily dose of 1
to 10 mg attributable to air alone. To this an unknown amount from
percutaneous absorption should be added.
It is obvious from the Table that the actual conditions differed mark-
edly from the equilibrium situation, as might be anticipated. The data
also points out that under some special situations, especially where the
water is in agitation or undergoing aerosolization, the levels may consid-
erably exceed those anticipated by equilibrium conditions. Nonetheless,
the expected values are reasonably close to the observed, at least in
comparison to many orders of uncertainty that we commonly have to
work with in toxicology.
References
1. Hunter, D. 1969. The Diseases of Occupations. 4th Ed. Little, Brown and Company,
Boston, Massachusetts, p. 1121.
2. Thtotfewayte, D. K. B., and E. E. Goteb. 1972. The composition of sewer air. In:
Advances in Water Pollution Research, S. H. Jenkins, ed. Proceedings of the Sixth
International Conference held in Jerusalem June 18-23, 1972. Pergamon Press, Ox-
ford, pp. 281-289.
3. Huang, J. Y. C., G. E. Wilson and T. W. Schroepfer. 1979. Evaluation of activated
carbon adsorption for sewer odor control. Jour. Water Poll. Control Fed.,
51:1054-1062.
4. Tabenhaw, T. R., H. M. D. Utidjian, and B. L. Kawahara. 1977. Chemical hazards.
In: Occupational Diseases—A Guide to Their Recognition. DHEW (NIOSH) Publica-
tion No. 77-181. Section VII.
-------
James B. Lucas 107
5. Occupational Safety and Health Administration. 1974. Occupational Safety and Health
Standards, Federal Register, 39 (#125). Part II. Thursday, June 27, 1974.
6. American Conference of Governmental Industrial Hygfenfcts. 1978. Threshold Limit
Values for Chemical Substances and Physical Agents in the Workroom Environment
with Intended Changes for 1978. Cincinnati, Ohio.
7. Forni, A. M., A. Cappellini, E. Pacifico, and E. C. Vigliani. 1971. Chromosome
changes and their evolution in subjects with past exposure to benzene. Arch. Environ.
Health, 23:385-389.
8. Carnow, B., R. Northrop, R. Wadden, S. Rosenberg, J. Holden. A. Neal, L. Sheaff, P.
Scneff, and S. Meyer. 1979. Health effects of aerosols emitted from an activated sludge
plant. EPA-600/1-79-019. U.S. Environmental Protection Agency, Cincinnati, Ohio.
9. Smith, R. P., and R. E. Gosselin. 1979. Hydrogen sulfide poisoning. J. Occup. Med.,
21:93-97.
10. Center for Disease Control. 1978. Deaths from asphyxia among fishermen. Morb. and
Mort. Wkly. Rpt., August 25th: 309-315.
11. Center for Disease Control. 1975. Deaths at a rendering plant-Ohio. Morb. and Mort.
Wkly. Rpt., December 20th: 435-436.
12. Center for Disease Control. 1978. Death in a farm worker associated with toxic gases
from a liquid manure system-Wisconsin. Morb. and Mort. Wkly. Rpt., February 10th:
17.
13. American Conference of Governmental Industrial Hygienists. 1971. Documentation of
the Threshold Limit Values for Substances in Workroom Air. 3rd Ed. Cincinnati,
Ohio. pp. 132-133.
14. Morse, D. L., J. R. Kominsky, C. L. Wisseman, and P. J. Landrigan. 1979. Occupa-
tional exposure to hexachlorocyclopentadiene: how safe is sewage? J. Amer. Med.
Assoc., 241:2177-2179.
15. U. S. Environmental Protection Agency. 1979. Identification and evaluation of water-
borne routes of exposure from other than food and drinking water. EPA-440/4-79-016.
Office of Water Planning and Standards, Office of Water and Waste Management.
DISCUSSION
DR. LUCAS: I have a note from Dr. Dean. A minor point, but a very
valid one, where he is pointing out that a small molecule, SOa, gave him
the asthma. SO2 is an irritant, and any good irritant will predispose to an
asthmatic reaction. So, you are not allergic to SO2, but it sure can
produce asthma.
DR. GERBA: Have you ever considered interaction between irri-
tants and infectious disease? I know that some types of pesticides seem
to enhance susceptibility of certain types of viral infections in animals,
and tissue cultures had demonstrated that pesticides can enhance the
susceptibility to infection by certain RNA viruses. Have you ever con-
sidered this in evaluating the effects of cotton or other organic
substances?
DR. LUCAS: Yes, in a sense. We have had, for a number of years, a
streptococcus that is sufficient to produce a fatal illness. Mice get a fatal
pneumonia from this particular strain. We also expose similar groups to
certain airborne pollutants, and regardless of what the pollutant is, if it is
an irritant like any of the oxides of nitrogen, we do see a definite in-
crease in mortality using that particular animal model. However, I don't
think we have done any work with tissue culture.
DR. GERBA: In other words, you are saying it lowers the infectious
dose?
DR. LUCAS: In essence, I think one could draw that conclusion.
This would enhance the susceptibility to a severe illness.
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108 Wastewater Aerosols and Disease/Health Aspects
MR. WITH AM: Are you implying that the increase in amounts of
benzene that you found are due to the aerosols and thus increased
surface area?
DR. LUCAS: I am implying only that it comes from the water. There
is no benzene whatsoever used in this plant. We know the water in the
plant contains benzene. I thought it was simply an interesting compari-
son against some theoretical calculations under ideal equilibrium condi-
tions. I use benzene, really, just as an example. It happens to be a real
world example and one where we actually have some data and where
someone has gone through the trouble of running it through a rather
complicated mathematical formula to get some theoretical values for us.
There aren't many substances for which this has been done. I think this
is an area that needs substantial enlargement.
MR. WITH AM: In other words, the amount of benzene we have in
the air is all available from what is in the water. It seems like a tremen-
dous amount.
DR. DEAN: I might add a little bit to that. Benzene is really highly
soluble in water. You think of it as a hydrocarbon insoluble in water but
it is quite soluble, about 700 mg/1. If you heat water you will boil off a lot
of the benzene. Was your theoretical calculation based on room temper-
ature or hot water?
DR. LUCAS: Under standard conditions.
DR. DEAN: Okay, but this is hot water.
DR. LUCAS: But in the shower room it was hot water.
DR. DEAN: That would account for the difference very easily.
DR. LUCAS: But, unfortunately, most people don't take cold
showers.
-------
109
Epidemiologic Approach to Disease Assessment
Robert K. Miday
Chronic Diseases & Biostatistics Program
Field Studies Division
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio
ABSTRACT
Epidemiologic studies are the primary means of assessing potential adverse health effects
on populationsj:xposed to waste water aerosols. The investigations presented at this sym-
posium use many of the classic methods of infectious disease epidemiology to test associa-
tions between health status and wastewater exposure. The interpretation of the results of
these studies requires the understanding of some of the central epidemiologic issues com-
mon to many of the investigations. These issues include the following parameters: expo-
sure assessment, health status measurement, the determination of associations between
exposure and outcome, and the effects of confounding and bias.
Methods of exposure assessment have focused primarily on air monitoring techniques,
but the actual dose of pathogenic organisms received by the population at risk is depend-
ent on many host, environmental, and infectious agent factors which are difficult to quan-
tify. Variables measured to detect adverse health effects include parameters ranging from
serum antibody changes to illness diaries, each having certain strengths and shortcomings.
The determination of associations between wastewater exposures and health outcomes
has been made by analyzing dose-response relationships, control group comparisons, and
trends over time. Potential sources of confounding and bias must be considered in relation
to each epidemiologic approach. Study population sample size availability often is a limit-
ing factor in the design and conduct of epidemiologic studies.
The primary objective of this paper is to introduce principles that are
relevant to the design, performance, and analysis of epidemiological
studies conducted to test the hypothesis that exposure to wastewater
aerosols is associated with human disease. Because investigations car-
ried out to test this hypothesis utilize such a variety of designs and
methodologies and, therefore, include epidemiologic issues of a compre-
hensive nature, it will be necessary to focus on those issues which are
most critical to the assessment of the health studies to be presented at
this symposium. I will introduce epidemiologic concerns in relation to
the following areas: study design, disease ascertainment, exposure as-
sessment, major sources of confounding and bias, sample size, and
criteria for establishing causation. The purpose is to review some princi-
ples that should be addressed in the performance of sound studies so
that the research presented in the remainder of the session can be better
evaluated from an epidemiologic perspective. Because a rather wide
range of topics is to be covered, there is a resulting lack of depth of
discussion in many areas.
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110 Waste water Aerosols and Disease/Health Aspects
Study design is the first area of discussion. The majority of the waste-
water aerosol studies utilize a prospective cohort design. One definition
of a cohort is a group of individuals sharing a common experience, and
in this case the experience is presumed exposure to sewage aerosols.
The prospective approach implies that the cohort is followed forward in
time while disease status is determined. This design is unquestionably
the most appropriate one for the majority of investigations where acute
infectious diseases are the health outcome of major concern. Because
most infectious diseases are self-limited and of short duration, their
prevalence at any one point in time in the general population is low.
Even relatively common illnesses such as respiratory infections may
occur on the average less than one to several days per year in each
person. Therefore, in order to accumulate sufficient illness experience to
be able to compare two populations, it is necessary to follow the study
groups for an adequate period of time, which may be months or years,
depending upon the sample size chosen. By ascertaining illness that
develops in the groups, incidence rates for specific diseases and symp-
toms can be determined. The incidence of disease is the number of new
cases occurring in a population at risk per time period. One of the
greatest advantages of the prospective cohort designs is that illness
incidence rates can be most accurately estimated with this approach.
Alternative designs utilize a retrospective approach to measure illness
occurrence. This implies either using available medical records, or using
a questionnaire to ask individuals about illness during some recent past
time period. In certain instances where usable records such as school
absenteeism are available, a retrospective design can be more efficient.
Unfortunately, very few records exist on population groups that are
complete enough to be of value in measuring infectious diseases, which
means that a questionnaire approach is usually necessary. This entails
the major drawback of inaccurate subject recall. It is very difficult to
obtain accurate histories of short-duration symptoms and diseases. In
comparison, the advantage of a prospective study is the potentially com-
plete enumeration of illnesses and calculation of incidence rates. Also,
the control for confounding variables may be better with the prospective
approach. Disadvantages are the necessity to follow individuals for a
long time period, the difficult logistics, participant drop out, and
expense.
Regardless of the design chosen, all studies must utilize some method
of ascertaining and quantifying ill health in the population. Common
sources of morbidity data are shown in Table 1. Reportable diseases
refer to those specific diseases that are recorded by state health depart-
ments by requirement. Epidemic reports result from investigations of
Table 1. Sources of Morbidity Data
Reportable diseases
Epidemic reports
Hospital, clinic, and physician data
Public health laboratory reports
School absenteeism
Population-based health surveys
-------
Robert K. Miday 111
sporadic outbreaks of disease. Hospital clinic and physician data are
self-explanatory. Population-based health surveys refer to systematic
morbidity studies, such as the National Health Survey.
Because of serious limitations usually related to incomplete disease
ascertainment, these sources of data are generalJy not useful for con-
ducting investigations of hypotheses that small segments of the popula-
tion are at an increased risk of illness because of some exposure. The
exception is the category entitled population-based health surveys; most
of the wastewater aerosol investigations utilize some form of these sur-
veys in order to obtain health status of the study population.
These surveys are performed by selecting a representative sample of
the population, soliciting volunteers for participation, and proceeding to
collect the relevant demographic and medical data. Various methods are
utilized to obtain information about health status. In the prospective
cohort survey, an individual illness diary is frequently utilized to record
disease occurrence. This is usually done by having a member of each
household record for each day the occurrence of symptoms and illness
in every family member. While this appears straightforward, there are
important aspects of the recording process that can impact the results
obtained. First, it is necessary to define illness in such a manner that all
participants have the same general perception of illnesses to be re-
ported. This may vary considerably according to the instructions given
or amount of contact with the research team. The mechanism of report-
ing can influence the accuracy and completeness of reporting. Are dia-
ries merely collected periodically, or does someone regularly contact
each household to review the diary, answer questions, etc.? A more
frequent reporting and personal contact schedule would generally be
expected to yield more accurate results. Interviewer training is crucial
because the instructions, guidance, and enthusiasm given by interview-
ers could certainly influence the diligence with which diaries were kept.
Finally, symptoms and diseases must be abstracted from diary records
in a systematic, standardized manner.
Administering a questionnaire presents some different potential prob-
lems. A sound design is essential with adequate pretesting. The report-
ing interval refers to the retrospective time period of recall of illnesses.
It is important to know the length of time back to which people were
asked to recall illness because, as this time period increases, accuracy
decreases. Again, interviewer standardization and training is essential to
assure comparability of data.
An alternate method of infectious disease ascertainment is through
the use of serology. This technique involves the collection of a blood
sample, separation of the serum, and determination of the amount of
circulating antibodies to those specific microorganisms. A second sam-
ple is collected at a later time, usually weeks or months later, and the
antibody levels are again measured. A fourfold rise in an antibody titer
is generally considered indicative of infection with that specific agent.
Advantages of serological testing are listed in Table 2. Probably the
greatest advantage is that it is an objective measure of infection, a
laboratory procedure determined and applied in a standard manner. This
is in contrast to self-reporting and questionnaire data. Second, this tech-
nique identifies specific pathogens. Potentially, the particular agent can
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112 Waste water Aerosols and Disease/Health Aspects
Table 2. Advantages of Serologic Methods
Objective measure of infection
Identifies specific pathogen
Information on both clinical and subclmical infections
Integrates past infectious experience
Excellent measure of incidence
then also be identified in environmental samples such as wastewater
aerosols. Serology provides information on both clinical and subclinical
infections. Because many infectious agents produce infections without
any clinical symptoms in a large proportion of persons affected, a more
complete picture of the population's experience with that microbial
agent can be gained from serological surveys. Another advantage of
serology is the persistence of antibody levels for long periods of time.
This enables information to be gained about past infections. Finally, the
documentation of antibody-level increases is an excellent indication of
the incidence of an infection, as rates of occurrence of new cases can be
readily calculated.
In spite of these advantages, there are substantial limitations to the
use of serology (Table 3). First, it is suitable only for selected agents and
is not useful for all pathogens of interest in sewage aerosols. Second, it
is necessary to test specifically for the correct agent in the group stud-
ied. It is not a broad screen for infections but is utilized to identify
particular viruses and bacteria. Third, a pre- and post-infection serum
specimen is needed, necessitating blood-drawing at least twice from
each subject. The expense can be quite high when testing for multiple
agents. Finally, although documentation of an infection may be termed
an adverse health effect, it is not as clear, if very few or no symptoms
are present, how much of a hazard this represents to the exposed indi-
viduals. It can be argued that development of antibodies without any
perceptible clinical disease is not a health threat. Overall, serologic epi-
demiology appears to offer many distinct advantages for studying infec-
tious diseases in populations. Increased use of this method in future
research may be expected.
In addition to evaluating the health status of individuals studied, it is
essential to collect certain social, personal, and demographic informa-
tion (Table 4). The primary reasons for obtaining this information are to
further categorize healthy and ill individuals and to ensure that no con-
founding variable has been introduced. A confounder is a factor that is
related to both the disease outcome and the exposure and is differen-
tially distributed in the control and exposed populations. The simplest
example of a potentially confounding factor in these wastewater studies
is age distribution. We know that children experience higher rates of
most acute infectious disease than adults. Suppose that there are twice
as many subjects under age 12 in the exposed group than the unexposed
controls. Then it is obvious that a greater disease incidence in the ex-
posed group could result from this age difference alone, and age would
be termed a confounding variable. Four major sociodemographic varia-
bles are age, sex, race, and social class. All of these, particularly age and
social class, are related to illness incidence and therefore need to be
-------
Robert K. Miday 113
similarly distributed in the various exposure categories. If they are not
similarly distributed, there are methods of dealing with the problem
through stratification, adjustment, or multivariate analysis. Unfortu-
nately, it is commonly the case that, even when these variables are
measured in surveys, they are subsequently ignored during the analysis
of the data. Particular attention should be paid to the treatment of poten-
tially confounding variables in the assessment of the validity of findings
of these epidemiologic studies.
Bias is the systematic introduction of error into a study. The first
source in Table 5, sampling, refers to selection of the study population,
and not purely to statistical considerations. Ideally, the study groups
should be comparable in regard to all important factors except the risk
factor under consideration. The samples selected should also be repre-
sentative of the parent population. A randomizing technique is often
used to generate samples, but this does not ensure representative un-
biased samples. If a sampling scheme is used where selection may be a
problem, then the samples should certainly be examined for the distribu-
tion of all important variables to determine if the exposed and control
groups are alike. Closely related to sampling is the issue of nonparticipa-
tion or nonresponse. When the response rate is not high, that is, when it
is below 80 to 90% of those selected, there is always the concern that the
respondents differed in some important characteristic from the nonre-
spondents. Thus, the nonrespondents should be examined whenever
possible to determine their similarity or differences from the respond-
ents. Observer variation reflects the influence that the researchers have
Table 3. Limitations of Serology
Suitable only for selected agents
Need to test for correct agent
Need to test at correct time periods
Expense, logistics, inconvenience
Risk assessment interpretations
Table 4. Sociodemographic and Personal Variables
Age School attended
Sex Occupation
Race/ethnicity Length of residence
Social class Medical status
Income Immunizations
Education Travel
Table 5. Major Sources of Bias
Sampling
Nonparticipation or nonresponse
Observer variation
Errors of response
-------
114 Wastewater Aerosols and Disease/Health Aspects
on the responses of the study groups. This has been referred to pre-
viously as interviewer effects. Potentially, the study could be biased if a
particular interviewer is able to elicit more disease-reporting response
than other interviewers. Finally, errors of response refer to situations
where participants erroneously answer an illness question because of
misperception.
I will not discuss exposure assessment except to mention that this is
obviously a critical link in epidemiologic studies. If an increase in illness
had been found in a community group residing nearer a treatment plant
and if some increased levels of viable organisms could be measured in
the air, then we would certainly feel more confident about attributing
this to aerosol exposure. Unfortunately, sampling methodology has
many limitations, and it is currently very difficult to measure exposure
accurately in these situations.
Finally, when association is demonstrated between disease and expo-
sure, there are a number of explanations which would account for this
association other than a causal relationship. To evaluate the likelihood
that an association is causal, a set of criteria is used. These criteria are
briefly reviewed here, with particular attention to how they could be
applied to studies of wastewater aerosol health effects (Table 6). The
strength of the association is measured by the ratio of disease rates for
those with and without the exposure. Thus, if the incidence of a particu-
lar illness in a population exposed to aerosols were four times the inci-
dence in an unexposed population, the association would be much
stronger than in a situation where the incidence is only two times as
great in the exposed group, assuming the statistical significance is simi-
lar in both cases. The strength of the association reflects the magnitude
of the effect and is one of the most important causal indicators. Closely
related to this concept is the criteria of a dose-response relationship. Is
the magnitude of effects observed greater with a greater exposure? This
gradient would be examined around sewage treatment plants by relating
illness rates to geographic proximity or meteorological conditions. Oc-
cupational exposures would be expected to produce a greater risk than
general community exposures. The consistency of an association refers
to the persistence of effects from one study to another, under varying
conditions, and with the use of differing methodologies. Replication of
results adds strength to the idea that the association found is not a
chance result and not a spurious association resulting from confounding
or bias. Thus, it is important to examine the consistency of findings in
the various investigations to be presented at this symposium. The spe-
cificity of the association refers to the degree to which the effect is
Table 6. Elements of Causation
Strength of the association
Specificity of the association
Consistency of the association
Temporal relationships
Biological plausibility
Dose-response relationship
Experimental validation
-------
Robert K. Wd»y 115
always associated with the exposure and the extent to which the risk
factor predicts the occurrence of adverse effects. Specificity is related to
strength of association. Because the health effects measured in these
studies have a variety of causes, and because a single pathogenic agent
can cause multiple clinical syndromes, this criterion is not as crucial to
the establishment of a cause-and-effect relationship. However, the link-
ing of a specific disease to a specific exposure is one of the greatest
indicators of causation. Temporal factors are very important in the in-
vestigation of acute infectious disease. Is the time of occurrence of
disease logically related to the hypothesized exposure? In terms of com-
munity exposure to treatment plants one could ask: Is an increased
illness incidence related to the time of start-up of operation, or to times
of increased production of viable particles? An additional temporal con-
cern-with regard to infectious disease is the incubation period, defined as
the time from first exposure to onset of symptoms. Incubation periods
vary widely. While the common cold occurs in several days of exposure,
enteroviruses, which are of primary interest in sewage aerosols, have
incubation times of 1 to 2 weeks. It might, therefore, be possible to
relate a known acute exposure to subsequent illness after an appropriate
delay time. This would certainly provide strong etiologic evidence.
Biological plausibility is a very logical criteria for causation. Certain
infectious processes, such as respiratory and gastrointestinal diseases,
appear far more plausible than others, such as urinary tract infection,
where inhalation does not conform to any known pathogenic mech-
anisms. However, one must be cautious not to reject an association
merely because it does not obviously fit expected disease patterns.
The final criteria, experimental validation, is probably not directly
applicable to these epidemiologic investigations. An experimental situa-
tion that would certainly be feasible is a pre- and post-control technol-
ogy experiment. In this case, disease rates would be measured during
and following known exposure to determine if a decrease in illness was
associated with aerosol suppression.
In summary, I have mentioned a number of topics relevant to the
design and performance of epidemiologic studies of acute infectious
disease. In assessing the investigations to be presented at this sympos-
ium, one should be aware of these issues, as a sound epidemiologic
approach is essential to gathering data that will help to answer the funda-
mental questions regarding wastewater aerosol exposure and disease.
DISCUSSION
MR. McCABE: If the people are irate because of the "stinking
thing" across the street, how would you handle that?
DR. MIDAY: Well, I think that you have raised a very logical con-
cern, particularly when you are assessing illness by asking people when
they experience symptoms. In that situation, I think you would be very
limited and you will have to rely on whatever dose response relationship
you could hope to develop, plus the use of more objective measures.
The consistency of the disease and the confirmation of the diseases
reported with known pathogenic mechanisms would be very important
-------
116 Waste water Aerosols and Disease/Health Aspects
here. But you are correct that you have to be very careful in knowing
what influenced people when they were reporting their illness
experience.
DR. DEAN: This problem of epidemiological investigation looks
very good and very easy for a chemist. I know we were asked how we
could chemically determine what was in our advanced waste treatment
purified wastewater, and we looked at the chemistry and said we can't
possibly do it by chemistry. Let's ask the epidemiologist. I went down to
ask them and they had a nice conference going on in North Carolina and
they started off by saying that the epidemiology was so darn complicated
that they needed to know the chemistry before they could give us an
answer. This was passing the buck at its highest stage.
Actually, when you are trying to look for nothing you have to look
infinitely hard. We have to strike a balance between how much work we
are going to do and how important it is to find the answer.
DR. FLIERMANS: One thing that is important with serology is that
it tells you what but it doesn't tell you where.
DR. MIDAY: Yes, I didn't point that out very clearly, but you are
right. That is why it would be very important to know other factors that
would play a part in an individual developing an antibody response.
However, if you are studying a large population group and you see
definite patterns associated with geography or associated with other
exposures, then you can be much more confident that the exposure was
not obtained at some other place such as work, school, travel, etc.
DR. DEAN: Well, we have had a good start in today's program. I
think that today has helped us to find out how difficult it is to come up
with any answers at all, and the following days we will see how success-
ful people have been when they have looked for answers.
-------
117
Acute Illness Differences with Regard to Distance
from the Tecumseh, Michigan, Wastewater
Treatment Plant
K. F. Fannin1*
K. W. Cochran2
D. E. Lamphiear3
A. S. Monto3
*Life Sciences Research Division, IIT Research Institute
10 West 35th Street, Chicago, Illinois
'Departments of Epidemiology and of Pharmacology,
The University of Michigan, Ann Arbor, Michigan
department of Epidemiology, The University of Michigan
Ann Arbor, Michigan
ABSTRACT
Acute illness incidence differences with regard to distance from an activated sludge waste-
water treatment plant were determined from data obtained as part of a comprehensive
community health study conducted from 1965 to 1971 in Tecumseh, Michigan. The addi-
tive minimum discrimination information statistic was used to test for significant differ-
ences in the incidence of total, respiratory, and gastrointestinal illnesses among individu-
als dwelling in a series of 600 m concentric rings radiating from the wastewater treatment
plant
When specifying socioeconomic factors, education and income exerted an unequal
influence on illness incidence variation and, in general, such variations between geo-
graphic locations were found to be greatest in groups having the lowest income and
education. The group within the 2,400 m perimeter concentric ring, which had a higher
income and education level than the other groups, had a greater than expected incidence of
all illnesses. Differences in illness incidence occurred during the May through October
season at varying distances from the wastewater treatment plant, but persons within 600 m
had a greater than expected risk of respiratory and gastrointestinal illness. Persons dwell-
ing within 600 m of the plant had respiratory illnesses that exceeded those expected by
20% and 27%, and gastrointestinal illnesses that exceeded those expected by 78% and 50%
when specified for income and education, respectively. The data suggest that the higher
illness rates are related to higher densities of lower socioeconomic families rather than to
the wastewater treatment plant.
'Present address: Institute of Gas Technology, Chicago, Illinois 60616.
Centralized processes of wastewater treatment aid sanitation efforts
in populated areas throughout the world. Most of these processes pro-
duce aerosols that can become windborne and be carried from the site of
treatment. These aerosols can contain many of the chemical and biologi-
cal substances found in wastewater. It is well documented that bacterial
aerosols are emitted from these treatment processes and that they can
be carried varying distances from the site of origin, depending upon
-------
118 Waste water Aerosols and Disease/Population Studies
environmental conditions (1). Although existing methodology is below
the required sensitivity for the routine isolation of animal viruses from
the airborne emissions of wastewater treatment facilities (2), enterovi-
ruses have been reported from aerosols emitted from wastewater spray
irrigation processes (3,4).
Although the health significance of exposure to such emissions has
not been adequately determined, some evidence is available. Ledbetter
et al. (5) showed that wastewater treatment plant workers had a higher
incidence of influenza than water treatment plant workers, and Katze-
nelson et al. (6), in a retrospective study, showed that persons living in
agricultural communal settlements practicing wastewater spray irriga-
tion had a higher incidence of shigellosis, salmonellosis, typhoid fever,
and infectious hepatitis than those who lived in settlements that did not
irrigate with wastewater, although the mode of transmission (aerosols,
person-to-person contact with field workers, etc.) was not determined.
Before undertaking extensive epidemiological studies regarding the
health effects of wastewater treatment facilities, existing data were uti-
lized for the evaluation of these effects. The city of Tecumseh, Michi-
gan, was sele'cted as a study site because an intensive community health
study, conducted by the University of Michigan, provided an opportu-
nity to utilize uniquely comprehensive data on the epidemiological expe-
rience of an entire community.
The purpose of the study was: 1) to determine whether there are
differences in incidence of acute infectious illness, depending upon pop-
ulation dwelling distance from a wastewater treatment facility; and 2) to
determine the suitability of Tecumseh, Michigan, as a site for a long-
term prospective study regarding the influence of wastewater treatment
upon the health of exposed populations.
METHODS
Recruitment and Surveillance
Procedures for recruitment and surveillance have been previously
described by Monto et al. (7). The dwelling units of Tecumseh, Michi-
gan, were divided into 10 samples by stratified random sampling from
each of five geographic strata described by Napier (8).* This sampling
procedure resulted in 10 sets of households with characteristics exem-
plary of the entire community. Each of the households within the 10
samples was randomly ordered for visit by trained interviewers. For
purposes of a study of acute respiratory infections, 18 to 24 families
were introduced per sample, with exception of the first 6 months of the
study when 48 families were recruited per sample. This family recruit-
ment was interrupted during late 1966 upon completion of the tenth
sample and then resumed in March 1967. Until May 1967, eligible study
families contained parents under age 45 and at least one child of school
age or younger. After this date, as part of a chronic bronchitis study,
families containing older adults were gradually added using the methods
described. Data were obtained from the participating families regarding
health history, socioeconomic factors, employment locations, and
schools attended by all children.
*The last of the six strata described by Napier, scattered new construction found during
1959 and 1960, was not included in this study.
-------
:. F. Fannin, K. W. Cochran, D. E. Lamphiear, A. S. A/onto 119
Report of Acute Illness, Tecumseh Community Health Study
A Since last week has anyone in the family had a cold, a sore throat, or the flu or any other respiratory
illness? N Y
B Since last week has anyone in the family had an upset stomach or diarrhea' N Y
(If only Q B , ask questions in boxes D only )
1 Would you tell me about.
_'s illness, what was the trouble?_
When did this (cold, flu, upset stomach, etc) first bother ' Date
Was seen by a doctor because of it'
D NO D YES — What did the doctor say about it, did he give it a medical name?
4. Did_
. have any of the following symptoms'
faTI any fever' ... . . ..NY
° if known
(Hanychills? NY
[cT] a headache' . NY
d. an earache?. ... . . . NY
Fel any general aches or pains' . .NY
f. a stuffy or runny nose? . . . . NY
g. a sore throat? NY
h. swollen or tender glands? . N Y
i any hoarseness? . N Y
ITl Was in bed because of it?
l.acough?. . ...
k any phlegm from the chest'.
I any wheezy breathing? . .
m pain or discomfort on breathing?
CrTI any nausea or an upset stomach?
Pol any vomiting?
["p~1 any diarrhea?
fgT] burning, aching or redness of
the eyes?
OH any stiffness of the neck?
FsTI any other symptoms'
N Y
NO YES
In hospital
At home
'671 Aside from days in bed (if any) was away from
work/school or restricted in usual activities?
NO YES
T] Does the still bother ' NO YES
IF NO, when did it last bother ?
Specimens D NO Q YES
I nterviewer
Dates
Days
Date.
N Y
N Y
Figure 1. Questionnaire used in the investigation of acute infections in
Tecumseh (7) (Reprinted with permission).
After recruitment, each family was contacted weekly by telephone or
personal visit and a single respondent was questioned regarding the
occurrence of short-term illness within the family during the past week.
When illness was reported, the details of the specific event were re-
corded using the questionnaire shown in Figure 1. The respondent was
contacted during the weeks following the initial report and asked
whether the illness persisted and to describe the symptoms. The date of
illness termination, if any, was obtained and the respondent was ques-
tioned regarding other illness development within the family. An illness
occurring at least 2 days after a termination date was regarded as a new
event.
Study Population Selection
The study population was defined as those participants in the Univer-
sity of Michigan Tecumseh Community Health Study from 1965 to 1971
who resided in dwelling units at specific distance ranges from the Tec-
umseh wastewater treatment plant (WWTP), located in the southeast
-------
120 Waste water Aerosols and Disease/Population Studies
quadrant of the city (Figure 2). Dwelling units located within each of five
concentric rings and beyond, radiating from the plant in approximate
multiples of 600 m, were identified. The dwelling units within the study
area were primarily single family houses, although multiple family units
occurred at various locations within the area. Confirmation of dwelling
unit locations near concentric ring boundaries was made by site
visitation.
The population used in nonseasonal-related analyses included those
individuals who were contacted at least 50 weeks in a row with no
absences during 4 or more weeks. The illnesses included are those
whose onset occurred within this 50-week period. The entire population
on report from 1965 to 1971 was used for determination of illness inci-
dence rates per person year.
As used in this study, colder months included November through
April whereas warmer months included May through October. In each
case, the study population was defined as those persons on report for the
entire 26-week period, with no long periods (2 weeks or more) off report.
The illnesses included are those whose onset occurred during the
26-week period.
Illness Classification
Acute illnesses were grouped into three general categories: total, res-
piratory, and gastrointestinal. Data are reported as incidence rates and
as individual illness rates. Age-sex-distance-specific incidence rates
were determined by dividing the number of each kind of illness by the
number of person-years observed within each group. Age-sex-distance-
specific individual illness rates were calculated by number of illnesses
during report period per number of weeks on report.
Statistical Analyses
The objective of the statistical analyses was to determine whether the
incidence of illness varied with distance of the dwelling unit from the
wastewater treatment plant. Ancillary information for each respondent
included age, sex, education of the head of the household, and family
income.
The null hypothesis was that the proportion of persons in the high
incidence category was the same in the subsets defined by distance from
the index point. The distribution of respondents by age, sex, and family
income or education level varied from one distance category to another.
The test statistic for the null hypothesis was a chi-square goodness-of-fit
test in which the expected frequencies were computed by summing the
expected frequencies for each age and sex group. The test was condi-
tional upon the family income or education of persons observed in
each distance category.
Let Ogki be the observed number of individuals in the ith age-sex
group, in the jth distance interval from the index point, in illness cate-
gory k, and in family income or education level 1 where:
i = 1,2. . . , 18: where there are nine sex-specific age intervals
j = 1,2, . . , 6: the six distance intervals determined by the five concen-
tric rings about the index point.
-------
:Wastewoter Treorment /"~
Plant
i
<
ts
Figure 2. Lcx^ition of Wastewater Treatment Plant and 600 m Concen trie Rings in Tecumseh Study Area
-------
122 Wastewater Aerosols and Disease/Population Studies
k= 1,2: the illness categories where
1 : n or fewer illnesses in the interval
2: n + 1 or more illnesses in the interval where n was selected
for each analysis according to type of illness and duration of
interval.
1 = 1 ,2,3: the family income or education level, depending on the analy-
sis, where:
(Family Income)
1: less than $7 ,000
2: $7,000 to 9,999
3: $10,000 or more
(Education of Household Head)
1 : less than high school diploma
2: high school diploma
3: some college or college degree.
Then summing, the following counts were obtained:
0 j.. =SZSO,jki: the number of individuals in the jth ring
ikl
Oi... =SS.SOjjki: the number of individuals in the sample in the ith age-
jkl sex group
Oi.k. =SZ2 Ojjkj: the number of individuals in the age-sex group who are
jl in illness category k
O...i =S220 ijki: the number of individuals in income or education level
ijk j
Assuming, as specified by the null hypothesis, that illness category
was independent of distance from the index point, the expected number
of individuals in the ith age-sex group at family income or education
level 1 at distance j in illness category k was:
Thus, within the ith age-sex group, the expected number of individuals
in the jklth cross-classification was proportional to the marginal totals.
The expected number of persons at distance j in illness category k and at
family income or education level 1 was:
The hypothesis of equality of illness rates in the distance categories
for a given socioeconomic level was the conditional hypothesis for
fixed, but not specified, socioeconomic levels. The test was a joint test
on the three levels simultaneously. The test statistic was the sum of the
minimum discrimination information statistics, described by Kullback
(9) and Kullback et al. (10), for the three individual tests:
21 =221, =Z2ZOjk|ln Ojld
i i
-------
K. F. Fannin, K. W. Cochran, D. E. Lamphiear, A. S. Monto 123
with degrees of freedom 1G-1) (k-1), the sum of the degrees of freedom
for the individual tests. Significant departures of the observed from the
expected frequencies, as indicated by the test statistic, led to rejection
of the null hypothesis against the alternative of an association between
high illness rates and distance from the index point. To determine that,
among persons at family income or education level 1, the proportion in
the high incidence category was the same in all subsets as defined by
distance from the index point, a test was performed separately on each
level 1. The statistic was the minimum discrimination information statis-
tic,
Ajkl
distributed as chi square with (j-1) (k-1) degrees of freedom.
Wastewater Treatment Plant Description
The Tecumseh wastewater treatment plant (WWTP) was located in
the southeast quadrant of the city (Figure 2). The plant was at a lower
elevation than most of the populated study area and was surrounded by
deciduous trees on the east, west, and south. This plant processed ap-
proximately 1 mgd of wastewater by activated sludge secondary treat-
ment. Activated sludge had been in use since 1965, when the plant was
redesigned from a trickling filtration facility. Data that might have been
used to estimate the fecal contribution to the wastewater, such as total
or fecal coliform concentrations, were not available for the study pe-
riod. Wastewater flow rates for the study period were not available from
the Tecumseh WWTP, but available data were obtained from the Michi-
gan Department of Natural Resources.
RESULTS
Sewage Flow
Average monthly sewage flow rates at the Tecumseh WWTP ranged
between 0.64 and 1.18 mgd from 1965 to 1971. Data, however, were not
available for 1966, and some data for 1965, 1968, and 1969 are missing.
As shown in Figure 3, the lowest sewage flow rates were observed
during 1965 and the highest monthly average was seen in 1968. Although
flow rate fluctuations are observed, no consistent flow pattern is evident
among the study years.
Illness Incidence
Age-sex specific individual illness rates per person-year for the Tec-
umseh study population during 1965 to 1971 are presented in Figure 4. In
general, illness incidence rates were higher in females than in males and,
although demonstrating a slight increase at ages 20 through 30, varied
inversely with age in both sexes. The lowest incidence rates were ob-
served for the gastrointestinal illness classification.
Socioeconomic Distribution
Of the 4,889 study participants, data are available on 3,627 and 4,877
individuals for income and education, respectively, of the household
head. The distribution of individuals at specified distances from the
-------
1.2
1968
1971
o
0>
S 0.8
o:
5
O
L-
S, °'6
O
to
1965
I
" 0.4
c
o
0.2
(Broken Lines Indicate Incomplete Data)
I
sr
0.0
M
J
Month
Figure 3. Monthly Average Sewage Flow Rates for the Tecumseh,
Michigan, Wastewater Treatment Plant from 1965 to 1971
(Source: Michigan Department of Natural Resources)
!
3T
-------
6 -
5 -
Total Illness — Mole
Total Illness — Female
Respiratory Illness —Male
Respiratory Illness—Female
Gastrointestinal Illness—Mole
Gastrointestinal Illness — Female
--o-
50
Figure 4. Average Acute Illness Incidence/Person-Year in Tecumseh Study Area, 1965 to 1971
to
-------
126 \Vastewater Aerosols and Disease/Population Studies
WWTP having household heads with income or education within high,
moderate, and low income or education categories was examined. Fig-
ure 5 shows the percent excess [((observed-expected)/expected) x 100]
individuals in each income and education category in each concentric
ring from the WWTP. The figure illustrates that the highest percent
excess number of individuals in the lowest income and education classi-
fication are located within the 600 m perimeter concentric ring while
those in the highest income and education category are located within
the 2,400 m perimeter concentric ring.
ILLNESS INCIDENCE BY DISTANCE FROM
WASTEWATER TREATMENT PLANT
For analyses, the number of persons having four or more total, three
or more respiratory, or one or more gastrointestinal illnesses during the
report period was determined. Consequently, the number of persons
reported in the total illness category is not necessarily the sum of those
in respiratory and gastrointestinal illness classifications since the criteria
for inclusion within a specific group are based upon different numbers of
illness occurrences.
Table 1 illustrates the summed income- and education-specific infor-
mation statistic for illness occurrences at varying distances from the
WWTP. Significant education-specific illness incidence variations were
observed over the total study period in all three illness classifications
and during the colder months in the gastrointestinal illness classification.
Differences in income-specific respiratory illnesses were seen during all
study periods and in income-specified total illnesses during the entire
study period and during the warmer months.
Considering each family income and education classification sepa-
rately, Table 2 shows that illness incidence variations among persons
living in the six different concentric rings was greatest in those individu-
Table 1. Summed Income-and Education-Specific Information Statistic
for Illness Occurrence at Varying Distances from Wastewater
Treatment Plant"
Study Period
Illness Classification11
Total
Total
May-Oct.
Nov -Apr
1
2831'
2532'
21.20
E
5469^
2516
2460
Respiratory
I
2822'
2638'
25.59'
E
4998''
1569
19.80
Gastrointestinal
I
1942
2021
1965
E
25.06'
2437
3248''
"Based on illness occurrences at 600; 1,200; 1,800; 2,400; 3,000; and > 3,000 m from wastewater
treatment plant
''Number of occurrences included in each classification-
Illness
Total
Respiratory
Gastrointestinal
Total
>4
>3
>1
Study Period
May-Oct
>3
>2
>1
Nov -Apr
>3
>2
i1
'95% confidence level based on 15 degrees of freedom
d99% confidence level based on 15 degrees of freedom
-------
80 r O
70
60
in
in
0)
C _-.
= 50
8 40
01
u
X
u 30
I 20
0
1)
°- 10
A
V
-
-
"
_
-
L
-
-
Z\ Income
O Education
L Low
M Medium
H High
i O
X
A T
t I?9? T ?
^L M Hj VL M H^, VL M H^ VL M H7
1 I I 1
5
a
1
^
L
b
5y*
^i
g
9 S3
L
5
O 1
^ i J !
VL M H^ ^L M Hj '
\ \ :
12 18 24
Concentric Ring Perimeter (mXlOO)
30
>30
Figure 5. Percent Excess Education and Income of Household Head by Distance from Wastewater Treatment Plant
-------
128 Wastewater Aerosols and Disease/Population Studies
als in the lowest income and education classification. The differences for
total gastrointestinal illnesses were significant during all three study pe-
riods when specified for education. With the exception of the moderate
income total illness classifications, no significant illness variations were
seen at the higher income or education classification.
Table 2. Income- and Education-Specific Information Statistic for Ill-
ness Occurrence Differences at Varying Distances from
Wastewater Treatment Plant"
Income or
education
level
Low
Moderate
High
Illness Classification
Study
period
Total
May-Oct
Nov-Apr
Total
May-Oct
Nov -Apr
Total
May-Oct
Nov -Apr
Total
Income
1360-*
326
881
11 28<*
13 74<<
680
343
831
5.58
Education
41 59'
143V
1472<<
333
7.03
1 45
977
382
844
Respiratory
Income
13.92-'
628
15.32'
1052
10.27
735
379
984
291
Education
44.5CX
948
10.79
073
381
1 60
476
240
741
Gastrointestinal
Income
5.87
5.55
391
491
9.97
658
864
471
917
Education
17.11'
11 53d
22.49
243
766
3.25
5.52
518
674
"Based on illness occurrences at 600, 1,200, 1,800, 2,400; 3,000; and >3,000 m from wastewater
treatment plant
^Number of occurrences included in each classification
Illness
Total
Respiratory
Gastrointestinal
'Income
>$7,000
$7,000-9,999
.>$! 0,000
Study period
Total May-Oct
>4 >3
>3 >2
>1 >1
Education
Less than high school diploma
High school diploma
Some college or college degree
Nov -Apr.
>3
>2
>1
Level
Low
Moderate
High
''95% confidence level based on 5 degrees of freedom
•99% confidence level based on 5 degrees of freedom
Summation of education- and income-specific illnesses by distance
from the wastewater treatment plant was performed, and percent excess
[((observed-expected)/expected) x 100] illnesses for the entire study
period is shown in Figure 6. The greatest illness excesses were observed
for income-specified gastrointestinal illnesses within the 600 m concen-
tric ring and for total illnesses in the 2,400 m ring. Breaking down the
study period observations into the colder and warmer months, Figures 7
and 8 illustrate that excessive illnesses occurred unequally among con-
centric rings and between the two seasons. For both income- and educa-
tion-specific illnesses, the number observed exceeded those expected by
the greatest amount in the 600 m concentric circle during the warmer
months for respiratory and gastrointestinal illnesses. Respiratory ill-
nesses exceeded those expected by 20% and 27% whereas gastrointes-
tinal illnesses exceeded those expected by 78% and 50% when specified
for income and education, respectively. Differences of this magnitude
-------
80
7O
60
in
i/i
| 5O
E 40
O)
0
X
u 30
§ 20
0)
Q-
IO
A Income-Specific
O Education-Specific
T Total Illness
R Respiratory Illness
G Gastrointestinal Illness
~
-
9 S o2 2 ?? 9
T R G, VT R Gj ^T R Gv VT R Gj i^T ^R_ Gj
i i i 1 l
6 12 18 24 30
Concentric Ring Perimeter (mXlOO)
X
s
i
ES*
51
*
b
1
s
•-•
^j
fcq
B
A *
£ 0 A i'
vJ ^R_ Gy ^.
1 c^
>30 ^
§
Figure 6. Summed Income- and Education-Specific Illnesses: Percent
Excess by Distance from Wastewater Treatment Plant During
Study Period
-------
8O
70
60
vi
V)
01
^50
8
0)
30
£ 20
o
a>
°- 10
Income-Specific
Education-Specific
Total Illness
Respiratory Illness
Gastrointestinal Illness
Hf?
CO
o
12 18 24 30
Concentric Ring Perimeter (mXlOO)
Figure 7. Summed Income- and Education-Specific Illnesses: Percent
Excess by Distance from Wastewater Treatment Plant During
May to October
ft
I
ti
a
l
I
5"
>30
-------
70
60
in
in
o>
£ 50
A Income-Specific
O Education-Specific
T Total Illness
R Respiratory Illness
G Gastrointestinal Illness
40
o>
u
X
§ 20
i_
a>
0.
IO
12
18 24
Concentric Ring Perimeter (mXlOO)
30
Figure 8. Summed Income- and Education-Specific Illnesses: Percent
Excess by Distance from Wastewater Treatment Plant During
November to April
>30
C
I
CO
-------
132 Wastewater Aerosols and Disease/Population Studies
were not observed during the colder months nor during the entire study
period. Greater than the expected number of illnesses were consistently
observed within the 2,400 m WWTP concentric ring for all income- and
education-specific illnesses during the warmer and colder months as well
as during the entire study period.
DISCUSSION
The Tecumseh, Michigan, wastewater treatment plant is small relative
to those which serve larger metropolitan areas. This plant was selected
for use in this investigation because of its location within a comprehen-
sive community health study area and because it was not considered to
be uniquely different from activated sludge plants serving comparably
sized communities. Consequently, the observations made in this study
should not be considered unique to Tecumseh but to represent those
made with the participation of a highly cooperative community.
In this study, acute illness occurrences in 4,889 people living at six
different general locations from a wastewater treatment plant were ob-
served over a 7-year period. More than the expected number of persons
living closest to the wastewater treatment plant (within 600 m) experi-
enced income- and education-specific illnesses during May through Oc-
tober. As seen in Figure 5, persons dwelling within 600 m of the waste-
water treatment plant had both less education and lower incomes than
those dwelling in the more distal locations. The greater-than-expected
number of persons developing illnesses nearest the wastewater treat-
ment plant during the summer may be attributable to reduced levels of
sanitation within a lower socioeconomic group during a period of higher
enterovirus infection incidence. Melnick et al. (11) demonstrated the
seasonal distribution of enteroviruses while Monto and Cavallaro (12)
confirmed a higher late summer incidence of enteroviral infection in the
Tecumseh study population.
The population dwelling within the 2,400 m concentric ring was found
to have a consistently greater-than-expected incidence of all education-
and income-specific illnesses. The reasons for the greater illness inci-
dence within this group are not readily explainable with available evi-
dence. As shown in Figure 5, persons dwelling within the 2,400 m con-
centric ring had both higher education and income than did the other
study groups. There are no known sources of exposure in the 2,400 m
area that would increase the likelihood of increased acute illness.
Although the concentrations of potentially infectious organisms in the
Tecumseh sewage are not available for the study period, it is known that
potentially pathogenic bacteria and viruses, excreted by the contributing
community, survive transport to wastewater treatment facilities (13,14).
While the aerosols emitted from the Tecumseh wastewater treatment
plant were not characterized as part of this study, it is reasonable to
assume that this plant does emit aerosols containing potentially patho-
genic infectious organisms, as has been observed with other activated
sludge plants studied (1).
The exposure and potential for infection probability of a population to
the airborne emissions of a wastewater treatment plant is dependent
upon the concentration, survival, and dispersion of aerosolized infec-
tious organisms. It is likely that, if certain community illnesses were
-------
K. F. Fannin, K. W. Cochran, D. E. Lamphtear, A. S. Monto 133
attributable to the wastewater treatment plant, such occurrences may
not be strictly distance-dependent since local airflow disturbances affect
airborne dispersion in a manner not predictable with present methods of
estimating diffusion (15). The plant is located at a lower elevation than
the portions of the study area containing most of the population and is
surrounded on the east, south, and west by deciduous trees. Depending
upon wind direction, velocity, and atmospheric stability, surrounding
trees may act as a partial barrier for persons dwelling nearest the plant
while lofting the airflow, resulting in further downwind dispersion.
When exposure does occur, however, the significance of risks of infec-
tion is related to the size and density of the population. Evaluation of the
effects of such exposure is further complicated by variations of suscep-
tibility to infections and resultant illnesses within an exposed
population.
The results of this study suggest that high rates of illness transmission
in areas of high densities of lower socioeconomic families is a more
important factor in excess illness within a population than is proximity
to a small wastewater treatment plant. Excess illnesses within these
lower socioeconomic families during the warmer months exceed those
observed during the colder months. Higher than expected illness inci-
dence within the highest socioeconomic group, however, cannot be
readily explained.
Further prospective study should identify the factors associated with
suggested increased illness risks within specified groups. The influence,
if any, of the wastewater treatment plant should be determined by de-
tecting areas of probable exposure and resultant illness incidence. A
design permitting the estimation of community transmission parameters
would enable separation of the influence of the wastewater treatment
plant from other potential sources of transmission.
ACKNOWLEDGMENT
This study was supported by U.S. Environmental Protection Agency
Grant No. R-804973.
The cooperation of residents and officials of the City of Tecumseh is
gratefully acknowledged. We are thankful to Daniel Myers, Water Qual-
ity Division, Michigan Department of Natural Resources for providing
available sewage flow data. The computer programming assistance pro-
vided by Helen Ross is greatly appreciated. The contributions of Nelson
Meade and discussions of James Koopman are gratefully acknowl-
edged. This study is deeply indebted to the organizers and participants
of the Tecumseh Community Health Study.
References
1. Hkkey, J. L. S., and P. C. Reist. 1975. Health significance of airborne microorganisms
from wastewater treatment processes. Part 1: Summary of investigations. Jour. Water
Poll. Cont. Fed., 47:2741-2757.
2. Fannin, K. F., J. J. Gannon, K. W. Cochran, and J. C. Spendlove. 1977. Field studies
on coliphage and coliforms as indicators of airborne animal viral contamination from
wastewater treatment facilites. Water Research, 11:181-188.
3. Johnson, D., D. E. Camann, C. A. Sorter, B. P. Sagik, and J. Glennon. 1977. A
comprehensive methodology for the prediction of pathogenic levels in wastewater
aerosols. In: Proceedings of Conference on Risk Assessment and Health Effects of
Land Application of Municipal Wastewater and Sludges. San Antonio, Texas.
-------
134 Wastewater Aerosols and Disease/Population Studies
4. Tcltsch, B., and E. Katze nelson. 1978. Airborne enteric bacteria and viruses from
spray irrigation with wastewater. Appl. Environ. Microbiol., 35: 290-2%.
5. Ledbetter, J. O., L. M. Hauck, and R. Reynolds. 1973 Health hazards from wastewa-
ter treatment processes. Environ. Letters, 4:225-232.
6. Katzenelson, E., I. Buium, and H. I. Shuval. 1976. Risk of communicable disease
infection associated with wastewater irrigation in agricultural settlements Science,
194:944-946.
7 Monto, A. S., J. A. Napier, and H. L. Metzner. 1971. The Tecumseh study of respira-
tory illness. I. Plan of study and observations on syndromes of acute respiratory
disease. Am. Jour. Epidemiol., 94:269-279.
8. Napier, J. A. 1962. Field methods and response rates in the Tecumseh community
health study. Am. Jour. Pub. Health, 52:208-216.
9. Kullback, S. 1959. Information Theory and Statistics. John Wiley & Sons, New York.
10. Kullback, S., M. Kuppeman, and H. H. Ku. 1962 Tests for contingency tables and
Markov chains. Technometrics, 4:573-608
11. Melnick. J. L., J. Emmons, H. J. Coffey and H. Scboof. 1954 Seasonal distribution of
coxsackie viruses in urban sewage and flies. Am. Jour. Hyg 59:164-184.
12. Monto, A. S., and J.J. Cavallaro. 1971 The Tecumseh study of respiratory illness II
Patterns of occurrence of infection with respiratory pathogens, 1965-1969. Am. Jour.
Epidemiol., 94:280-289
13. Kabler, P. 1959. Removal of pathogenic microorganisms by sewage treatment proc-
esses Sew.Ind Wastes, 31:1373-1382.
14 Grabow, W. O. K. 1968. The virology of wastewater treatment. Water Research
2:675-701
15. Pasquill, F. 1962. Atmospheric diffusion. In: The Dispersion of Windborne Material
from Industrial and Other Sources. D. Van Nostrand Co , Ltd., Lond.
DISCUSSION
MR. LINDAHL: Was any consideration given to the fact that for the
period from May through October the windows were open, and for the
period from November through May the windows were closed?
DR. FANNIN: There were several reasons for selecting the two pe-
riods. There was evidence that during the warmer months there was an
increased instance of enterovirus infection within that population, and
there was a greater exposure during the summer. It was intended to
specify for the time of the year because of expected greater exposure
and expected higher instance rates during that season.
MR. LINDAHL: Was any consideration given to the effect of the
trees surrounding the basin?
DR. FANNIN: Well, I eluded to that consideration in my discussion,
where I indicated that the trees probably did act as a partial barrier for
any aerosols that might have been emitted from the plant. They might
have disrupted local air flow patterns resulting in relatively unpredicta-
ble downwind dispersion.
MR. LINDAHL: One more question. Would you suggest planting
trees around the wastewater plant as one of the alternatives to improve
the situation?
DR. FANNIN: Yes. I think that is an acceptable method for provid-
ing some barrier to a potentially exposed population.
DR. LEDBETTER: I would like to point out something about the
statistics that bothers me. On Figure 6 you have 18 different possibilities
across there. You have total, respiratory, and gastrointestinal illness. I
note that nine of them are blank, that is, don't have any circles or
triangles. I presume they turned out negative.
DR. FANNIN: Taking the test indicates excess illnesses only. So,
you are correct that the points which don't have figures indicate that
-------
K. F. Fanm'n, K. W. Cochran, D. E. Lamphiear, A. S. Monto 135
fewer than expected illness occurrences were noted at that particular
location for that particular illness.
DR. LEDBETTER: Isn't it amazing that it turns out exactly 9 out of
18. It has some above average and some below average. I think we draw
a conclusion where there is not any supporting data.
DR. FANNIN: First of all, Dr. Ledbetter, I might note that with the
statistical analyses, the thing we were trying to determine was whether
there were differences in illness occurrences.
DR. LEDBETTER: I'm really concerned when I look at Figures 6,
7, and 8. Fuller says not to trust those that divide it into parts in order to
get big numbers. I think the people that read that article are not scien-
tists, overall, but statisticians.
DR. DEAN: I would like to know how many of your four thousand
population were inside the inner circle?
DR. FANNIN: They were unequally distributed throughout the pop-
ulation. I don't have the figures with me but I can tell you that there were
fewer individuals in the inner circle.
DR. DEAN: What I want to know is, when you talk about 10 excess
cases, how many actual illnesses are you talking about-10, 100, 1,000?
DR. FANNIN: We are talking about fewer than 100, and I don't
have the raw data with me, but I can tell you that it was based upon very
few illnesses.
DR. DEAN: Well, in the inner circle differences of 20% can't be
significant. You have got to have something bigger than that because
you are working with such small numbers.
DR. FANNIN: Well, that is true. We are working with small num-
bers and this study was designed as a preliminary study to determine if
there were any detectable differences with regard to distance from the
sewage plant. But there are other factors involved, not merely distance
in this study.
DR. FUHS: What is your population with respect to the prevailing
wind direction?
DR. FANNIN: I have a wind rose of prevailing wind direction which
will illustrate this point. The major population center was upwind from
the prevailing wind.
I think this is important to consider but I think you should realize that
the population in Tecumseh has a very strong data base on comprehen-
sive community health, and that is the reason the city was selected. The
location of the plant is very good from a public health point of view, I
believe.
DR. LUE-HING: My question has to do with the reference you
mentioned from Israel. Are you referring to the reported article in
"Science"?
DR. FANNIN: Yes, I am referring to a reported article in
"Science."
DR. LUE-HING: I just want to say that I may disagree with the use
of the conclusions of the article without the necessary caveats. The data
include people not necessarily working in the sprays. Without the cave-
ats, other persons reading the citation may get the wrong impression,
and I would hope that would not be the case. My colleagues may disa-
gree but that is my feeling.
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136
Health Effects from Wastewater Aerosols at a New
Activated Sludge Plant: John Egan Plant,
Schaumburg, Illinois
Donald E. Johnson
David E. Camann
Kay T. Kimhall
R. John Prevost
and Richard E. Thomas
Department of Environmental Sciences
Southwest Research Institute
San Antonio, Texas
ABSTRACT
A study was performed to identify public health hazards of aerosols from operating
sewage treatment plants by examining a new activated sludge facility. Environmental
monitoring, a household health survey, and assays of clinical specimens from human
subjects were conducted during four baseline and operational sampling periods within a 5
km radius of the plant. The residential area began 350 m from the plant.
The wastewater aerosol from the aeration basins was a statistically significant source of
indicator bacteria and a presumed source of coliphage, pathogenic bacteria, enteroviruses,
and mercury. However, the levels of microorganisms and trace metals in the air in neigh-
boring residential areas were not distinguishable from the background levels.
The nearby residents reported a higher incidence of skin disease and several gastrointes-
tinal symptoms after the treatment plant became operational. Antibody tests for 31 human
enteric viruses and attempted isolations of many pathogenic bacteria, parasites, and vi-
ruses yielded virtually no clinical evidence of infectious disease effects associated with the
sewage treatment aerosol.
At the exposure levels investigated, the sewage treatment aerosols from well-operated
American plants do not appear to be a significant health hazard to residential populations.
The current evidence is insufficient to determine whether effects of lesser consequence,
such as gastrointestinal symptoms and skin conditions, are associated with moderate
aerosol exposure.
INTRODUCTION
Background
The United States Environmental Protection Agency, through its con-
struction grants program to the states and municipalities, is funding a
multibillion dollar effort to construct new wastewater treatment facili-
ties throughout the United States. These new facilities are required to
reduce sewage pollution of the waterways of the nation.
In the past, many wastewater treatment plants have been constructed
in relatively unpopulated areas. From an engineering standpoint, how-
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Donald E. Johnson, et al 137
ever, some facilities must be located close to the residential areas
served. Consequently, urban development has placed large populations
in close proximity to treatment facilities in recent years.
Locating a wastewater treatment plant near residential areas might
pose a health problem because of the wastewater aerosol produced by
the plant. Large amounts of wastewater aerosol are generated during
secondary treatment by the aeration basins of activated sludge plants
and by trickling filters. Pathogenic organisms excreted by infected indi-
viduals in the area served by the plant often survive the primary treat-
ment process. Thus, the wastewater aerosol may contain the pathogenic
microorganisms of diseases occurring in the service area.
Hickey and Reist (1) and Kowal and Pahren (2) provide a useful
summary and evaluation of the literature. It has been adequately demon-
strated in the literature that activated sludge and trickling filter treatment
processes are a source of aerosolized microorganisms (3-11) which are
carried at least 50 m downwind from the aeration basin (4,5,11).
The pathogenic microorganisms in the wastewater aerosol could in-
fect exposed populations, such as workers, nearby residents, and per-
sons passing through the area. There have been few studies designed to
examine the potential health effects of a wastewater treatment plant on
the surrounding population. Fannin et al. (9) reported increased risk of
respiratory and gastrointestinal illness for persons within 600 m of a
wastewater plant, but socioeconomic differences in the study popula-
tions confound the interpretation of their results. Northrop and cowork-
ers (10) found that a large wastewater treatment plant was a source of
microorganisms, but no obvious health effects on residents were evi-
dent. Clark et al. (12), in preliminary results, found some evidence of
increased subclinical viral infections but none for bacterial infections in
workers engaged in wastewater collection and treatment. Katzenelson
et al. (13) examined communicable diseases in Israeli populations living
near facilities which utilized essentially untreated wastewater and found
that the incidences of dysentery, typhoid fever, and infectious hepatitis
were higher in populations which utilized the wastewater. The use, how-
ever, was not limited to spray irrigation.
This paper reports the results of an environmental monitoring and a
prospective epidemiology study of a new activated sludge wastewater
treatment plant located near Chicago, Illinois (14).
Objectives
The objectives of this study were: 1) to determine whether sewage
treatment processes are a source of bacteria, viruses, and trace metals in
aerosols; 2) to identify health effects which might be attributable to a
sewage treatment plant.
Study Design
The design was to monitor the environment and the health of persons
near a new activated sludge treatment plant before and after its initial
operation. The environmental monitoring during the baseline period
measured microorganisms and trace metals in ambient air, soil, and
surface water. After the plant became operational, the wastewater and
-------
138 Wastewater Aerosols and Disease/Contaminants
the wastewater aerosol were also monitored. A household health survey
was conducted on the incidence of respiratory, gastrointestinal, eye,
ear, and skin diseases, and symptoms in persons living within 5 km of
the plant. This survey was performed both prior to the operation of the
plant and after its initial operation. The health of a subgroup of volun-
teers from the baseline health survey was monitored through isolates of
pathogenic bacteria, viruses and parasites in clinical specimens, through
viral antibodies in serum, through specimen trace metal levels, and
through reported incidence of relevant diseases and symptoms. These
persons lived within 3.5 km of the plant. Their health was monitored in
early fall and mid-winter both before and after the initial operation of
the plant.
Site
The design of this study (i.e., before and after initial operation) neces-
sitated that a new wastewater treatment plant be selected which was not
an addition to an existing plant and that a sufficiently large population
reside near the plant site in order to conduct a sensitive health study.
The John E. Egan Wastewater Plant of the Metropolitan Sanitary Dis-
trict of Greater Chicago, located near Schaumburg, Illinois, was se-
lected. The Egan plant is a conventional activated sludge plant with a
design dry weather flow of 30 mgd (1.4 x 108 I/day). The study site map
presented in Figure 1 shows the plant location on Salt Creek. The area
shown is located approximately 25 miles northwest of downtown Chi-
cago, Illinois. The study site was divided into two concentric regions
(within 3.5 km and from 3.5 to 5.0 km) about the Egan plant. The design
permitted the use of distance and prevailing wind direction(s) as surro-
gate measures of exposure. The presumably least exposed subjects pro-
vided a control population with similar socjoeconomic and demographic
characteristics.
Daily resultant wind directions from the U.S. Weather Bureau at
O'Hare International Airport showed that prevailing winds were from
the southwest and south and secondarily from the north-northeast dur-
ing the operational period of the study. Thus it was anticipated that
exposure to aerosols from the plant aeration basin would be less for
residences located to the west and northwest than in other directions.
The wind rose diagram, giving the distribution of daily resultant direc-
tions from which the wind blew during the operational period, is pre-
sented in Figure 2.
METHODS
Environmental Monitoring
Air and Wastewater Sampling. Air samples were taken simultaneously
upwind and at several distances downwind from the plant. Continuous
meteorological measurements for wind speed, wind direction, and rela-
tive humidity were made by an on-site weather station. Microbial air
samples were collected by use of large volume electrostatic precipitator
air samplers (LEAP and Litton types). Sampling runs were conducted
for 30 min at a sampling rate of 1.0 m3 of air/min. A typical sampler
array was one upwind sampler with four or five samplers at various
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Donald E. Johnson, et al
139
Note: Shaded areas show location of participants from which dintcal specimens were obtained.
Figure 1. Map of study area around John E. Egan Sewage Treatment
Plant.
distances from 15 to 300 m downwind. A wastewater sample was col-
lected from the aeration basin during sampling to allow comparison with
air levels of the monitored microorganisms.
Large volume composite samples of wastewater were collected from
the aeration basin to indicate the relative prevalence of routine indicator
organisms and selected pathogens. A more comprehensive screen of
two grab samples was conducted to identify and provide semiquantita-
tive data on potentially pathogenic organisms.
Bacteriology. Wastewater and air samples were analyzed for indicator
and potentially pathogenic organisms by procedures detailed in Stan-
dard Methods, the 13th edition (15) or 14th edition (16). Total and fecal
coliform were determined using the membrane filter method (16), and
standard count was determined according to Standard Methods (16)
using an automatic colony counter.
Virology. The enterovirus assay of wastewater and air samples was
performed using a bentonite concentration method with enumeration on
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140
Wastewater Aerosols and Disease/Contaminants
PERIOD
OBSERVATION
i\'0 OF OBSERVATIONS
SOURCE
O HARE INTERNATIONAL AIRPORT
CHICAGO LL'NOIS
JANUARY - OCT03EP 1976
DAILY RESULTANT WIND OiPSCT'ON
30E DA^s
LOCAL CL'MATOLOC-lCAL DATA,
NATIONAL CLIMATIC CENTER
N
0/360"
330
300
90' E
15%
240'
120"
210°
150"
180"
S
Figure 2. Distribution of daily wind direction during the operational
period (Jan.-Oct. 1976)
He La cell monolayers and reported as pfu/1 original sample (17). Two-
thirds of the plates of each assay were incubated for three days and
scored for plaques. To avoid overgrowth of slower-growing enteric vi-
-------
Donald E. Johnson, et al 141
ruses by poliovirus plaques, the remaining one-third of each sample was
mixed with pooled antipolio serum, incubated for five days and scored
for plaques.
Household Health Survey
Design. Household surveys were conducted prior to plant operation
(baseline survey) and after its initial operation (operational survey) to
collect demographic and health information on residents who lived in
the study area. The baseline survey also served as a basis for recruit-
ment of participants. During each of the two survey periods, approxi-
mately 1,100 households were contacted, about one-half in the inner
concentric circle and the balance in the outer concentric region. The two
regions were divided into 22 sectors, 12 in the inner circle and 10 in the
outer region. A stratified sampling by sector was conducted, and ap-
proximately 50 households were interviewed in each. The head of the
household or spouse was asked to complete a questionnaire on each
person in the household regarding demographic characteristics and oc-
currences of selected chronic and acute diseases and symptoms.
Households. The characteristics of the local residents are presented in
Table 1, based on the 1970 census tracts wholly or partially within the 5
km radius study area. The area population was considered sufficiently
large to conduct the health study. It consisted primarily of white, middle
to upper-middle class residents who lived in single family homes.
The baseline survey in September 1974 was conducted in 1,043 house-
holds between 1 and 5 km from the plant site. The study design had
scheduled the operational survey for September 1975, but initial opera-
tion of the plant was delayed until December 1975. In the meantime, an
apartment complex was opened very close to the plant site (from 350 to
800 m northwest of the first-stage aeration basin). Accordingly, in Sep-
tember 1975 an additional 75 baseline surveys were conducted in this
new community of nearby residents. After the treatment plant began
operation, 1,104 household surveys were obtained in September 1976.
A total of 1,118 households with 4,428 members were included in the
baseline survey, and 1,104 households with 4,269 members were in-
cluded in the operational survey. The two survey samples were com-
pared to determine any differences in personal and demographic charac-
Table 1. Characteristics of Residents (1970 Census)
Age Number
Less than 5 13,238 Median income—$6,000
5-19 35,265 Median education—12.5 years
20-44 38,514 Race—99.3% white
45 + 12,435 Occupational status—31.3% professional or managerial
99,452
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142
Wastewater Aerosols and Disease/Contaminants
teristics. Fewer children, especially those less than nine years of age,
were involved in the operational survey than in the baseline survey.
Also, there were fewer children within 2 km of the plant site in the
operational survey.
Diseases and Symptoms. The questionnaire obtained a report from the
household head or spouse on the occurrence of acute diseases within the
last 12 months and symptoms within the last three months for each
person in the household. Table 2 shows a list of diseases and symptoms
monitored. Prior to data analysis, these diseases and symptoms were
evaluated by a physician to identify the likelihood of association with
possible pathogens in sewage treatment aerosols and to identify the age
group expected to have the highest incidence rate. This evaluation was
used in interpreting the results.
Table 2. Diseases and Symptoms Monitored in Household Health
Survey
Polio
Pneumonia
Skin disease
Spinal meningitis
Croup
Anemia
Empyema
Infectious jaundice
Worms
Pleurisy
Influenza
Sleeping sickness
Dysentery
Symptoms
Severe headache not
relieved by aspirin
Severe dizziness
Severe night sweats
Canker sores around mouth
Sore throat
Cold
Diarrhea
Bloody diarrhea
Bloody urine
Burning on urination
Yellow skin
Weakness of arms or legs
Stiff neck with fever
Stiff neck with rash
Fever above 103°F
Colicky pains in abdomen
Shortness of breath
Unconsciousness (not due to
blow on head)
Severe pain in bones and
joints with high fever
Severe weight loss
Hemorrhagic rash
Yellow eyeballs
Cough
Skin rash: face
Skin rash: arms and legs
Skin rash: body
Nausea
vomiting
Pain in chest on deep breathing
Cough up blood
General weakness
Draining ear
Severe trouble with teeth
Brown urine
Convulsions
Statistical Methods. The data from the Household Health Survey are in
the form of frequency counts of reported occurrence of a particular
chronic illness, disease, or symptom. The statistical methodology deter-
mined any significant changes in the rate of occurrence between the
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Donald E. Johnson, et al 143
baseline period and the operational period. In addition, any change in
incidence rate associated with the distance of the household to the Egan
plant was determined. When both conditions were met, i.e., the inci-
dence rate of a disease or symptom was significantly higher in the opera-
tional period than in the baseline period, and incidence rate increase was
highest in households within 2 km of the Egan plant, then the sewage
treatment plant was considered for its potential as the source.
A multiple approach was used for this evaluation. First a contingency
table was constructed with factors of survey period at two levels (base-
line and operational) and distance at three levels (0 to 2.0 km, 2.0 to 3.5
km, and 3.5 to 5.0 km). Using chi-square test of independence, the
incidence of each illness, disease, and symptom was tested for signifi-
cant interaction or dependence between distance and survey period.
Diseases or symptoms exhibiting this tendency were compared to the
physician's evaluation for likelihood of a relationship to the treatment
plant and for age group expected to show highest incidence.
As a second method of evaluation, the relative incidence in the base-
line and operational periods were compared. The test statistic was a
standard normal deviate, Z, calculated to test the null hypothesis of
equivalent proportions in the two surveys in the same distance range.
The same test was also used for the incidence rates for the three dis-
tances separately to determine if any change in incidence had a distance
pattern consistent with the hypothesis of a plant effect on community
health. To identify possible plant effects, the difference measure, Zi, at
the 0 to 2.0 km range, had to be more strongly positive than at the
remaining distances, Z2 and Z3, and for the overall trend in the study
area, Z0.
For those diseases and symptoms for which a possible effect was
identified, the relative incidence was determined for the four wind direc-
tion quadrants, and the incident rates in the prevailing downwind direc-
tions (north and south) were examined.
Since many incidence rates vary with age or sex, the possibility that
this was the cause of the observed changes in incidence was investigated
by comparing the incidence rates within age and sex subgroups at the
closest distance for each disease and symptom possibly identified with
the plant.
Clinical Specimens
Human Subjects. A total of 231 participants began the study in October
1974, 51 participants from the close-in apartment complex were added in
October 1975, and 226 completed the clinical specimen health monitor-
ing in October 1976. The majority of the 20 percent of participants who
dropped out of the study did so because they relocated, and there was
no attempt to replace them. Blood, feces, urine, blood, throat swabs,
sputum, and hair were collected during each of the four periods.
The characteristics of the 226 study participants who finished the
study are given in Table 3. The plan had been to collect equal numbers
of participants in each of the eight age-sex groups, but the need to
include parents to obtain the participation of young children resulted in
overrepresentation of the 19-45 age group. The participants were pre-
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144 Wastewater Aerosols and Disease/Contaminants
Table 3. Characteristics of Participants
Age Sex
Male Female
0-6
7-18
19-^*5
46+
20
27
43
15
105
26
20
55
20
121
Race: 96% white
Education- 49% of heads of households completed college
dominantly white, in accord with the racial distribution of the area resi-
dents (Table 1). Some 49% of the heads of participant households had
completed college, indicating that selected volunteer participants were
better educated than the community as a whole. Regarding the distribu-
tion of ages, the participants were particularly representative of the
general population:
Participants Residents
42% 18 years or less 49% 19 years or less
43% 19-45 years 39% 20-44 years
15% 46 years or more 12% 45 years or more
The distribution of participants relative to distance from the center of
the plant was as follows:
Distance (km) Number of Participants
0.3—0.6 34
1.4—1.9 35
2.0—2.9 113
3.0—3.5 44
The 34 participants living close to the plant (350 to 600 m from the
primary aeration basin) all resided in the apartment complex northwest
of the plant location. Since the prevailing winds are from the north and
south and seldom from a southeasterly direction, these 34 participants
were usually upwind from the plant's aerosol emissions.
Bacteriology. Pathogenic and potentially-pathogenic bacterial isolates
were sought from the feces, sputum specimens, and from the throat
swabs. Sputum specimens were only analyzed for Mycobacterium tub-
erculosis. Fecal specimens and throat swabs were analyzed for each of
the following pathogens and potential pathogens: 1) Proteus; 2) Pseudo-
monas; 3) Salmonella; 4) Shigella; 5) Staphylococcus aureus; 6) Staphy-
lococcus epidermidis; and 7) Streptococcus-beta.
Fecal Specimens. Bacteriological examinations of feces were per-
formed in accordance with the standard procedures and techniques
which have been established for isolation and identification of microor-
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Donald E. Johnson, et al 145
ganisms by clinical diagnostic laboratories and by procedures standard
for the conducting laboratory. Feces samples were inoculated onto Sal-
monella-Shigella agar, endo agar, eosin-methylene blue agar, and Mac-
Conkey agar plates for primary isolation. Cultural morphology, bio-
chemical reactions, microscopic appearance, and serologic testing were
employed as required.
Throat Swabs. Bacteriological examinations of throat swabs were
performed in the same manner as the feces samples. Throat swabs were
inoculated primarily onto blood agar plates.
Sputum. Sputum specimens were inoculated onto Lowenstein-Jensen
Medium and Middlebrook 7H-10 Medium in screw cap tubes and incu-
bated in a CO2 incubator.
Parasitology. Seven hundred eighty-nine fecal specimens were analyzed
for a variety of helminths (parasitic worms) and protozoa. Parasites and
commensals from the following groups were sought: Helminth-Nema-
todes, Helminth-Cestodes, and Protozoa. The merthiolate-iodine-for-
malin concentration technique (MIFC) proposed by Blagg et al. (18) was
used.
Virology. The fecal specimens and throat swabs were both analyzed for
a spectrum of virus groups and associated microorganisms:
adenovirus papovavirus
arbovirus picodnavirus
arenavirus picornavirus
coronavirus poxvirus
herpesvirus reovirus
oncornavirus rhabdovirus
orthymyxovirus other viruses
paramyxovirus chlamydia and ricksettia
Fecal Specimens. Isolation and identification of viruses from feces
were performed by standard procedures (19) and by procedures of the
NIH/WHO Regional Reference Center for Simian Viruses. Monolayer
cell cultures of primary baboon kidney and cultures of a continuous cell
line (WI-38) were employed for demonstration of cytopathology.
Throat Swabs. Virologic examinations of throat swabs were per-
formed by the methods used for feces. Primary isolation was performed
on primary baboon kidney cells and WI-38 cell monolayers.
Viral Serology. Two sets of viral serology tests were conducted on the
blood samples. Eight tests were conducted on all participant blood sam-
ples to measure the antibody levels to the following viruses: Coxsackie-
virus B-l; Echoviruses 3,7,11, and 12; and poliovirus 1, 2 and 3.
A second set of 23 additional serologic tests was conducted on the
paired October sera of 100 selected participants, which were classified
into three groups of presumably different aerosol exposure. Group I (28
participants) resided in the apartments just northwest of the plant within
0.3 to 0.6 km. Group II (39 participants) resided within 1.4 to 2.3 km and
primarily to the south. Group III (33 participants) resided within 2.8 to
3.5 km of the plant mainly to the northwest. The groups were well
matched for age, sex, and socioeconomic status with a higher frequency
-------
146 Wastewater Aerosols and Disease/Contaminants
of smokers and central air-conditioning in Group I. The 23 additional
tests for these 100 paired sera were as follows: Adenoviruses 1,2, 3, 4,
and 5; Coxsackievirus A-7, A-9, A-16, B-3, B-5, and B-6; Echoviruses 4,
6,8, 13, 19, 21,25,29, and 33; and Reoviruses 1,2, and 3.
Serological analyses were performed by standard procedures (19).
The specific test systems employed were hemagglutination-inhibition
and serum neutralization. Each viral serology test determined the con-
centration range of the viral antibody in a blood sample by a titration
procedure. Most tests used six serial two-fold dilution levels: 1 in 10, 20,
40, 80, 160, and 320. Poliovirus tests were conducted at two tenfold
dilution levels (1 in 10 and 1 in 100), because poliovirus antibody levels
presumably resulted from vaccinations.
Statistical Methods. The statistical analysis of the clinical specimen mi-
crobiology had two major objectives: 1) to determine from the self- and
seasonally-paired data whether there were increases in the incidence of
pathogen isolates or antibody titer rises in the operational sampling peri-
ods, and, if so; 2) to determine whether such increases were related to
surrogate aerosol exposure measures such as distance from the sewage
treatment plant, or to other factors such as participant characteristics.
Participants residing between 350 and 600 m from the aeration basin
comprised a separate analysis group termed the "close-in" participants.
In order to determine whether the occurrence of pathogen isolates in
the clinical specimens and viral antibody titers had increased after the
plant began operating, the analytical results of the samples taken from
each participant were matched according to season (February or Octo-
ber) and compared for each of the bacteria, parasites and viruses ana-
lyzed in the four sample media (feces, throat swabs, sputum, and
blood). Comparisons of the paired isolation results from bacterial, par-
asitic, or viral analyses of feces, throat swab, or sputum samples yielded
three possible outcomes: decrease, increase, or no change from the
baseline to the operational sampling period. Through a series of two-
sided sign tests, paired samples showing an increase or decrease were
analyzed; incomplete pairs were deleted. All of the microbiological iso-
lation data were analyzed in this way.
Each serologic test result was reported as a viral antibot r titer. Con-
secutive integer codes were assigned to the geometric se..?s of titer
levels and difference scores were computed from the codes for paired
sera. Wilcoxon's one-sample signed ranks tests were applied to the dif-
ference scores to determine whether the presence of antibodies to these
viruses had increased in the operational year. The analysis of the 23
additional serology tests required comparison of antibody changes ob-
served in the three defined groups having presumably different levels of
aerosol exposure. The Kruskal-Wallis H test was used, followed by
planned comparisons to elucidate distance-exposure relationships.
All pathogens showing an overall increase in occurrence or in titer
level in the operational periods were further investigated through step-
wise multiple regression to determine if the pattern of increases was
associated with surrogate measures of aerosol exposure. The 34 poten-
tial regressor variables consisted of possible plant aerosol exposure fac-
tors (e.g., distance, prevailing downwind directions, hours per day at
home), other environmental factors, and personal factors.
-------
Donald E. Johnson, et al
RESULTS
147
Environmental Monitoring
Wastewater. Table 4 shows a summary of the data for the microbial
analyses of wastewater from the primary aeration basin. While Salmo-
nella and Shigella were not detected, Klebsiella, mycobacteria, Pseudo-
monas and fecal streptococci were found at relatively high levels. Low
concentrations of human enteroviruses (primarily polioviruses) were
seen, and they were primarily associated with solids (approximately
98%). The first stage aeration basin had substantially higher levels of
coliforms than did the second stage.
Air Sampling. Table 5 shows a summary of the data from microbiologi-
cal assay of air samples. Measurable levels of standard plate count, total
coliform, fecal coliform, coliphage, fecal streptococci, and Pseudo-
monas were found above background at near downwind sites. Proteus,
Klebsiella, Salmonella, Shigella, and enteroviruses were not detected.
Statistical examination of these data revealed that the wastewater plant
Table 4. Microbial Concentrations in Aeration Basin
Standard Analyses (Geometric Mean)
Standard Plate Count, SPC/ml
Total coliform, cf u/ml
Fecal coliform, cfu/ml
Coliphage, pfu/ml
Fecal streptococci, cfu/ml
Pseudomonas, cfu/ml
Proteus, cfu/ml
Salmonella, cfu/ml
Shigella, cfu/ml
Enteroviruses, pfu/ml
Three-day
Three- and five-day
5,800,000
400,000
21,000
120
1,300
10,000
<3
<3
<3
0.2
0.2
Bacterial Screen (Semquantitative)"
Clostridium, cfu/ml
Enterobacter, cfu/ml
Klebsiella, cfu/ml
Leptospira, cfu/ml
Mycobacteria, cfu/ml
Staphylococcus, cfu/ml
6
2,000
8,000
30
1,000
2,000
a Bacterial screening results are geometric means from 2 grab samples
Table 5. Microbial Aerosol Concentrations
(Microorganism Geometric Mean)
Upwind 15-25m 50-80m 95-200m
Standard Plate Count, SPC/m3
Total colifof m, cf u/m3
Fecal coliform cfu/m3
Coliphage, pfu/m3
Fecal streptococci, cfu/m3
Pseudomonas, cfu/m3
Proteus, cfu/m3
Salmonella, cfu/m3
Shigella, cfu/m3
Enteroviruses, pfu/m0
4,400
1.3
0.2
0.02
<2
<4
<2
<2
<2
<0.02
29,000
12.4
0.7
0.08
<2
50
<2
<2
<2
<0.02
9,000
6.9
0.5
0.04
15
<4
<2
<2
<2
<0.02
7,100
3.1
0.03
002
<2
4
<2
<2
<2
<002
-------
148 Wastewater Aerosols and Disease/Contaminants
was an aerosol source of standard plate count, total coliform, and fecal
coliform but that the elevated levels returned to background levels at
residential distances.
Large volume aerosol samplers are necessary to provide the sensitiv-
ity to obtain quantitative microorganism aerosol concentrations, espe-
cially for pathogens. However, the large volume samplers have a tend-
ency to become and remain contaminated with some of the hardy
microorganisms, such as Pseudomonas, usually resulting in an ex-
tremely high standard plate count.
Six-stage Andersen samplers were used to determine particle size
distribution of microbiological aerosols. The limited standard plate
count and total coliform size data suggest that about half of the viable
particles were in the primary respirable range (between 1 and 5 M in
diameter).
The first stage aeration basin was determined to be a borderline signif-
icant source of aerosolized mercury. However, there was no difference
in the mercury levels between the residential upwind and residential
downwind locations. The aeration basin was not a detectable source of
Cd or Pb, since there was no significant difference between their upwind
and close downwind levels in air.
Household Health Survey. From the chi-square tests of independence,
the incidences of the following diseases and symptoms were determined
to exhibit a significant interaction or dependence between distance and
survey period at the one percent level: influenza, vomiting, asthma-hay
fever, and worms. Significant at the five percent level were dysentery,
general weakness, nausea and sore throat.
Based on the physician's evaluation of possible sewage treatment
association, asthma-hay fever and worms were considered unlikely to
be related and were eliminated from further consideration. It was the
physician's judgment that the remaining symptoms might be associated
with sewage treatment aerosol exposure.
As a result of the Z tests (standard normal deviate), three additional
diseases or symptoms were implicated as possibly being associated with
sewage treatment aerosol exposure: skin disease, diarrhea, and pain in
chest on deep breathing. Each of these responses showed a significant
increase at the 0 to 2.0 km range and nonsignificant changes at the
greater distances. The reported incidence of the identified illnesses, dis-
eases, and symptoms in each of the three distance ranges in the baseline
period and operational period is presented in Table 6, and the test statis-
tics for significance for each identified response are presented in Table
7. As shown in Table 6, all responses, except asthma-hay fever, worms,
and sore throat showed an increased relative incidence (percentage inci-
dence) at the 0 to 2.0 km range which is suggestive of sewage treatment
aerosol exposure. This was further demonstrated by the significant chi-
square and positive Zi values in Table 7 for each of the responses.
Further examination of these symptoms for an association with pre-
vailing wind directions showed that there was an increase in the south-
ern inner sectors for all the diseases and symptoms possibly identified in
the prior analyses as associated with aerosol exposure, and in the north-
ern inner sectors for all but two. Since these were the two predominant
downwind directions during the operational period, the consistency of
-------
Donald E. Johnson, et ai
149
Table 6. Incidence of Illnesses, Diseases, and Symptoms Reported in
The Household Health Surveys
Baseline survey
Household members surveyed
0.0-2 Okm
2.0 - 3.5 km
35-50km
Chronic illnesses ever diagnosed
Asthma - hay fever
00-20km
20-3.5km
3.5-5 Okm
Diseases diagnosed during past year
Dysentery
0 0 - 2.0 km
20-35km
3 5 -5.0 km
Influenza
0.0 - 2.0 km
20-35km
3.5 -5.0 km
Skin disease
0.0 - 2.0 km
20-35km
35-5.0km
Worms
0.0 - 2.0 km
2 0 - 3.5 km
3.5 -5 Okm
Number of
responses
N
750
1711
1951
Positive
responses
n
102
188
176
2
22
13
70
221
366
4
28
27
7
27
11
Percentage
incidence
P
13.6%
11.0%
9.0%
0.3%
1 3%
0.7%
9.3%
129%
18.8%
0.5%
1 .6%
1.4%
09%
1.6%
0.6%
Operational survey
Number of
responses
N
644
1621
1992
Positive
responses
n
72
182
235
3
1
7
72
122
182
11
21
27
0
0
14
Percentage
incidence
P
1 1 .2%
11.2%
1 1 .8%
0.5%
0.1%
0.4%
11.2%
7.6%
9.1%
1.7%
1.3%
1.4%
0.0%
0.0%
0.7%
Symptoms experienced in Past 3 months
Diarrhea
00-20km
2.0 - 3.5 km
35-5.0km
General weakness
0.0 - 2 0 km
2 0 - 3.5 km
3.5 -5.0 km
Nausea
00-20km
20-35km
3.5 -5.0 km
Pain in chest on deep breathing
0.0 - 2 0 km
2.0 - 3 5 km
35-50km
Sore throat
0.0 -2.0 km
2.0 -3.5 km
3.5 -5.0 km
Vomiting
00-20km
20-3.5km
3.5- 5 Okm
31
73
94
5
17
29
9
41
59
4
27
28
132
269
333
10
52
53
4.1%
4.3%
4.8%
0.7%
1.0%
1.5%
1 2%
2.4%
3.0%
0.5%
1.6%
1 .4%
17.6%
15.7%
17.1%
1 3%
3.0%
27%
49
77
85
12
7
11
19
23
33
12
24
22
59
195
243
20
23
47
7.6%
4.8%
4.3%
1.9%
0.4%
0.6%
3.0%
1 .4%
1.7%
1.9%
1.5%
1 1%
9.2%
12.0%
12.2%
3.1%
1.4%
2.4%
-------
150 Wastewater Aerosols and Disease/Contaminants
Table 7. Test Statistics for Significance of Responses
Illness, disease, or symptom Chi-square ZQ Z: Z2
Asthma-hay fever
Influenza
Worms
Vomiting
Dysentery
General weakness
Nausea
Sore throat
Skin disease
Diarrhea
Pain in chest on deep breathing
1319"
15.06"
2496"
12.04*
10.03"
10.40°
10.04°
8.45°
427
4.20
489
143
-8.64
-3.90"
-1 48
-3.63
-2.17b
-2.26
-655"
022
1.07
0.12
-1.36
1 14
-2.46*
2.27*
0.62
203*
2.32°
-4.57"
2.12"
2.78°
2.32°
0.22
-5.12
-5.08*
-315
-4.27
-1.92
-2.05"
-3.08>
-0.82
0.67
-023
2.85 *
-8.73
0.55
-0.71
-1.39
-2.93*
-2.84*
-4.33 "
-0.08
-0.83
-0.93
"Significant at 0.01 level Required: X2 - 11.34, Z - 2 58
°Significant at 0.05 level. Required: X2 - 7.84, Z - 1.96.
these results lends some credence to the possibility that these reported
changes in general health status may be associated with sewage treat-
ment aerosol exposure.
In examining incidence by age and sex subgroups, the lower propor-
tion of young children in the operational survey may explain the je-
ported incidence reductions in worms, sore throat, and high fever. How-
ever, it increases the likelihood that the reported higher incidence of
gastrointestinal systems was actually associated with aerosol exposure.
A summary of the results from the health survey is presented in Table 8.
Clinical Specimens
Bacterial Isolates. Proteus, Pseudomonas, and Salmonella were the only
pathogen isolates in the feces samples; fecal streptococci were fre-
quently isolated but are not considered pathogenic. Statistical analysis
showed a significant decrease in the incidence of Proteus isolations in
the operational periods and no significant differences in the isolation
incidences of Pseudomonas or Salmonella between the baseline and
operational periods. There were significant increases in the incidence of
throat swab isolates of Streptococcus-beta and Staphylococcus aureus
in the operational periods. However, regression analysis of the inci-
dence pattern with distance and direction from the plant indicated that
the increases were not related to the participants' exposure to sewage
treatment aerosols. No Mycobacterium tuberculosis was isolated in any
sputum sample.
Parasitic Isolates. Protozoa were found in eleven samples; none con-
tained helminths. The protozoans were identified and their frequencies
were Chilomastix mesnili (1), Entamoeba coli (4), Entamoeba hart-
manni (1), Endolimax nana (1), Giardia lamblia (3), and Trichomonas
(1). Depending on the sampling period, from 0 to 2 percent of the partici-
pant samples contained parasites. The incidence of parasitic isolates
from feces increased slightly in the operational period; however, im-
provements in sample collection and processing during the operational
sampling periods may be responsible for the increased incidence.
-------
Donald E. Johnson, et al
Table 8. Summary of Health Survey Analyses
151
Illness,
disease, or
symptom
Asthma-hay fever
Influenza
Worms
Vomiting
Dysentery
General weakness
Nausea
Sore throat
Skin disease
Diarrhea
Pan in chest
on deep
breathing
Test for
independence
Significant at 0 01
Significant at 0.01
Significant at 0.01
Significant al 0.01
Significant at 0.05
Significant at 0.05
Significant at 0.05
Significant at 0.05
Not significant
Not significant
Not significant
Physician's
evaluation
Not related
Related
Possibly
related
Related
Related
Related
Related
Related
Possibly
related
Related
Not related
Distance
relationship
None
Slight increase
at 0-2, decrease
overall
None
Significant in-
crease 0-2,
slight decrease
elsewhere
Slight increase
0-2, decrease
elsewhere
Significant in-
crease 0-2,
significant de-
crease elsewhere
Significant in-
crease 0-2,
significant de-
crease elsewhere
None
Significant in-
crease 0-2, no
change elsewhere
Significant in-
crease 0-2, no
change elsewhere
Significant in-
crease 0.2,
slight decrease
Direction
relationship
—
Increase at
close distance
in south
—
Increase at
close distance
north and south
None
Increase at
close distance
north and south
Increase at
close distance
in south
—
Increase at
dose distance
north and south
Increase at
close distance
north and south
Increase at
close distance
north and south
Viral Isolates. No viruses were found in the throat swabs. All 20 of the
positive virus isolates in the feces samples were picornaviruses. The
picornavirus group includes polioviruses, coxsackieviruses, echovi-
ruses, and rhinoviruses. The picornavirus isolation comparison results
were evaluated through a sign test which indicated that there had been a
significant increase in picornavirus isolations in the operational sampling
periods (see Table 9). Comparison with the serologic liters showed that
subjects with picornavirus isolates had liter rises to a variety of echo
and coxsackie viruses, bul ihere was Hide correlation of ihe isolales
with tiler rises and seroconversions. Regression analysis was ihen used
lo determine whelher ihe pattern of isolalion increases conformed lo
plant aerosol exposure. The resulling equalion explained very little of
the variability in the pattern of increases, and Ihe two potenlial exposure
factors identified exhibited ihe wrong relalionship lo be associated wilh
aerosol exposure (isolalions decreased with exposure and were greater
-------
152 Wastewater Aerosols and Disease/Contaminants
Table 9. Comparative Analysis of Viral Isolations in Feces Samples
Results of paired comparisons8
0 Total
— (N) (P) + Pairs
Picornavirus
Original participants-February
Original participants-October
Lexington Green participants-October
Total comparisons
Result significant increase, p = 0.016
2
0
0
2
176
145
28
349
2
0
0
2
5
7
0
12
185
152
28
365
a— = the pathogen was isolated in the baseline period sample, but was not isolated in the paired
operational period sample
0 = the paired baseline and operational period samples both contained the pathogen (P), or both were
negative for the pathogen (N)
+ = the pathogen was isolated in the operational period sample, but not in the baseline period sample
northwest of the plant). Thus, there is no evidence that the sewage
treatment aerosol was related to the increase in picornavirus isolates.
Viral Serology. Table 10 summarizes the difference scores from the
paired comparisons of the tilers to Echovirus 12 and Poliovirus 1, two of
the eight specific tests conducted on all serum samples. The statistical
analysis of the paired comparisons determined whether the presence of
the antibodies to those viruses in human blood samples had increased in
the operational year. Only antibodies to these two viruses demonstrated
significant changes between baseline and operational samples. Titers to
Echovirus 12 declined significantly in the operational period (p = 0.045).
Titers to Poliovirus 1 rose significantly after the sewage treatment plant
began operation (p = 0.014). Regression analysis was used to determine
whether the pattern of Poliovirus 1 liter rises was consistenl wilh plant
aerosol exposure. The resulting equation provided no evidence of asso-
ciation with the plant's aerosol.
Analyses comparing Groups I, II, and HI were conducted for the 23
additional serologic tests. Antibody liter difference scores are presented
in Table 11 for three of the 23 viruses for which possible anlibody
changes were found. Only the changes in antibody to Echovirus 29 were
significantly different among the three groups (p = 0.02). There was a
borderline significant difference among the groups in Echovirus 13 anti-
body (p = 0.07), and a difference approaching significance for the
changes in antibody to Echovirus 33 (p = 0.18).
If the plant aerosols were contribuling to the presence of viral anti-
body in the blood, it is plausible thai Ihe effect would be proportional to
exposure. The negative exponential of distance from the Egan aeration
basin may be a good surrogale measure of long-lerm cumulalive expo-
sure to the microbiological aerosol (20). Based only on this exposure
measure, the close-in participanls (Group I) were expected to evidence
-------
Donald E. Johnson, et al 153
Table 10. Summary of Viral Antibody liter Comparisons from Original
Tests on All Human Subjects
Results of paired comparisons8 Total
-3 -2 -1 0 +1 +2 +3 pairs
Echovirus 12 by hemagglutination-inhibition
Original participants-February 0 1 14 176 8 0 0 199
Original participants-October 0 5 1616510 2 0 198
Lexington Green participants (October) 00 226200 30
Total comparisons 0 6 32 376 20 2 0 427
Result, significant decrease, p = .045
Results of paired comparisons' Total
-2 -1 0 +1 +2 pairs
Poliovirus 1 by serum neutralization
Original participants-February
Original participants-October
Lexington Green participants (October)
Total comparisons
Result significant increase, p = .014
0
0
0
0
2
0
2
4
173
155
28
356
6
10
1
17
0
0
0
0
181
165
31
377
a A code difference of 1 corresponds to a twofold liter level change for echovirus and tenfold for poliovirus
the greatest increase in viral antibody titer, followed by the nearer origi-
nal participants (Group II). Planned contrasts were conducted on the
Echovirus 29 antibody data; a borderline significant increase in titer
rises occurred in Group II relative to Group III (p = 0.05).
An increase in antibody titer of at least a factor of four in paired sera
is generally defined as seroconversion, indicating an immune response
to infection. Of the three Echovirus 29 serocon versions among the 100
paired sera, two (a seven-year old girl and her father who lived nearly 2
km south of the aeration basin) were from Group II and the other from
Group III. In an effort to determine what factors were contributing to
the pattern of titer rises, the Echovirus 29 difference scores were re-
gressed. The regression equation provided little evidence of an associa-
tion between Echovirus 29 titer rises and exposure to the plant aerosol.
In general, the serology analyses provided little evidence of the se-
wage treatment aerosol as a source of virus. For the one virus exhibiting
an overall increase in antibody titer (Poliovirus I), there was no evidence
at all of the expected relationship of plant aerosol exposure to the ob-
served titer rises. The Echovirus 29 results provide possible evidence of
an exposure-related pattern in the original participants, but no effect
occurred in the close-in participants who were seldom downwind.
Trace Metals. Clinical specimen trace metal data from blood, feces,
hair, and urine appeared unrelated to the presence of the sewage treat-
ment plant. Trace metals analyzed were Cd, Cu, Pb, Hg, and Zn.
-------
154
Wastewater Aerosols and Disease/Contaminants
Table 11. Summary of Viral Antibody liter Comparisons from Additional
Tests on 100 Human Subjects
Results of paired comparisons8 Total
-2 -1 0 +1 -t-2 pairs
25 0
36 1
29 1
90 2
Echovirus 13 by hemagglutination-inhibition
Group I (Lexington Green participants) 0 3
Group II (Original participants-near) 0 0
Group III (Original participants-far) 0 2
Total comparisons 0 5
Result, borderline significant difference, p = .07
Echovirus 29 by hemagglutination-inhibition
Group I (Lexington Green participants) 0 1 27 0
Group II (Original participants-near) 0 0 32 5
Group III (Original participants-far) 0 2 29 1
Total compansons 0 3 88 6
Results- significant group difference, p = .02
0 28
2 39
1 33
3 100
0 28
2 39
1 33
3 100
Echovirus 33 by serum neutralization
Group I (Lexington Green participants)
Group II (Original participants-near)
Group III (Original participants-far)
Total comparisons
Results: approaching significant difference, p = .18
0
0
0
0
0
1
2
3
27
35
31
93
1
3
0
4
0
1
0
1
28
39
33
100
"A code difference of 1 corresponds to a twofold liter level change
DISCUSSION
Significance of Findings
Source of Wastewater Aerosol. The wastewater aerosol from the Egan
aeration basins constituted a significant aerosol source of total and fecal
coliforms and the standard plate count of aerobic and facultative ana-
erobic heterotrophic bacteria. The sampled wastewater concentrations
and projections using the microbiological dispersion model (20) suggest
that the aeration basins were also a source in early October 1976 of such
potential pathogens as Klebsiella, Pseudomonas, and fecal streptococci.
One would expect the potential pathogens prevalent in the aerosol
source to vary with the cyclical epidemic pattern of the associated dis-
eases in the community serviced by the sewage treatment plant. Salmo-
nella and Shigella, for example, were not prevalent at that time. With the
possible exception of Hg, the Egan wastewater aerosol did not appear to
be a significant source of trace metals, especially relative to vehicular
traffic and industrial point sources.
Environmental monitoring did not detect higher than background lev-
els of indicator coliforms and the standard plate count at the distances of
the nearest residences (350 to 600 m). This is to be expected in light of
model projections of the downwind levels (20), and the sensitivity of the
air samplers. Similar results were obtained from extensive distant moni-
toring at a wastewater spray irrigation site (21, 22).
-------
Donald E. Johnson, et al 155
Reported Symptoms and Illness. There were statistically significant in-
creases in the self-reported incidence of skin disease, of a gastrointes-
tinal syndrome (diarrhea, nausea, vomiting, and general weakness), and
of pain in chest on deep breathing in the surveyed households within 2
km of the sewage treatment plant. These increases occurred primarily in
the predominantly downwind quadrants (north and south) and were not
observed in the households more distant (2 to 5 km) from the plant.
The proportion of young children was smaller in the operational pe-
riod survey, both in the total survey population and in the households
within 2 km of the plant. This age disparity might explain the statistically
significant decreases in the reported incidence of sore throat, and fever
above 103 F, both of which are more common in young children. How-
ever, it fails to explain and accentuates the anomaly of obtaining the
reported higher incidence of the gastrointestinal symptoms near and
downwind from the plant.
Thus, the elevated reported incidence of gastrointestinal symptoms
and skin disease might have been associated with the wastewater aero-
sol from the Egan plant. Suitable infectious agents were present in the
wastewater (e.g., enteroviruses and atypical mycobacteria). Alterna-
tively, the distance and directional pattern of reported incidence might
reflect an odor-induced reporting bias or a "normal" sporadic outbreak
of unknown origin. Since many diseases and symptoms were statisti-
cally analyzed, it is also quite possible that one or more of the identified
statistically significant patterns are "false positives" (i.e., Type I
errors).
Other studies of health effects from sewage treatment aerosols tend to
corroborate this weak evidence of acute gastrointestinal and skin effects
reported near the Egan plant. While most of their investigations of
health effects versus exposure were negative, Northrop and coworkers
(10) did find some significant correlations of incidence of skin conditions
with their index of aerosol exposure at a very large older treatment
plant. This association was evident among families whose youngest
child was between 5 and 14 and among families with over 20 years of
local residence. Rylander and Lundholm have found a high incidence of
gastrointestinal symptoms among workers in conventional sewage treat-
ment plants and in a plant composting household garbage and sewage
sludge (23). Rylander suggests that endotoxins rather than infectious
agents may be responsible for the gastrointestinal symptoms he studied
(23-25).
Clinical Specimens. Antibody tests for 31 types of human enteric viruses
(enteroviruses, reoviruses, and adenoviruses) resulted in statistically
significant rises in titer to Poliovirus 1 and Echovirus 29 and a significant
decline in Echovirus 12 titer. The only viral isolates from fecal speci-
ments, picornaviruses, were isolated significantly more frequently after
the Egan plant began operation. The subjects with picornavirus isolates
had titer rises to a variety of echo and coxsackie viruses, but there was
little correlation of the isolates with titer rises or seroconversions. The
distance and directional patterns of occurrence suggest that the Poliovi-
rus 1 titer rises and the picornavirus isolates were unrelated to sewage
-------
156 Wastewater Aerosols and Disease/Contaminants
treatment aerosol exposure. The occurrence pattern of the Echovirus 29
liter rises shows a slight association with aerosol exposure, but the
evidence is inconclusive. Thus, the viral serology and attempted isola-
tions of many potentially pathogenic bacteria, parasites, and viruses
produced virtually no clinical evidence of infectious disease effects as-
sociated with operation of the Egan plant.
Health Effects of Sewage Treatment Aerosols
Sewage treatment and its aerosols have not been found to have ob-
vious adverse effects on health in several extensive studies of American
facilities. No clinical or clear subclinical health effects on residential
populations were evident, either in this study covering the first nine
months of operation of a new activated sludge plant (14) or in Northrop
and coworkers' seven-month health watch near a very large older acti-
vated sludge plant (10). The health of sewer workers, sewage treatment
workers and their families was monitored by Clark et al. in several
cities, and no evident adverse health effects of occupational exposure
were observed (26). At the exposure levels investigated, the treated
sewage and aerosols at well-operated American sewage treatment plants
do not appear to be a significant health hazard to the workers or to
nearby residential populations.
Infectious or allergic disease effects of lesser consequence, such as
the self-reported gastrointestinal syndrome and skin disease in this Egan
study, may sometimes occur with greater frequency among nearby resi-
dents as a result of moderate exposure to sewage treatment aerosols.
The current evidence is insufficient, either to associate or to disassociate
such effects with aerosol exposure. The primary difficulty in designing a
definitive health watch is the lack of a sufficiently large, sensitive popu-
lation group (i.e., young children, whose immunologic defenses against
infectious diseases are still developing) that resides close enough to the
source to receive a high dose of the aerosolized agent(s). Another diffi-
culty occurs in studies of sewage treatment facilities. Interpretation of
any observed health effects (especially identifying the route of infection
or disease transmission) is confounded by the almost universal practice
of locating the sewage treatment plant within the area it services. The
ultimate sources of the pathogens in the wastewater aerosol are infected
individuals in the service area. If evidence of health effects due to these
pathogens were to be found, it is very unlikely that the route of trans-
mission (whether by direct contact, wastewater aerosol, or some other
pathway) could be ascertained.
Both of these difficulties in designing a definitive health watch can be
partially mitigated by investigating the health effects of wastewater aer-
osols at new sites where wastewater is applied to land on a large scale by
sprinkler irrigation. A demonstration project is being conducted near
Lubbock, Texas to construct, operate, and evaluate such a land treat-
ment system. An average of 7.4 mgd (2.8 x 107 1/d) of unchlorinated
secondarily treated municipal wastewater from Lubbock will be applied
by sprinkler irrigation in a farming community 18 miles away. A three-
-------
Donald E. Johnson, et al 157
year prospective infectious disease health watch of the farm families
spraying with wastewater and nearby residents and a supporting envi-
ronmental monitoring program are planned to investigate potential sub-
tle health effects associated with the wastewater aerosol.
References
1. Hickey, J.L.S., and P.C. Reist. 1975. Health significance of airborne microorganisms
from wastewater treatment processes. Journal, Water Poll. Control Fed,, 47:2741.
2. Kowal, N.E., and H.R. Pahren. 1979. Health effects associated with wastewater treat-
ment and disposal. Jour. WaterPoll. ControlFed., 51:1301.
3. Fair, G.M., and W.F. Wells. 1934. Measurement of atmospheric pollution and contam-
ination by sewage treatment works. In: Proc. 19th Annual Meeting New Jersey Sew.
Works Assoc., Trenton, New Jersey, p. 20.
4. Ledbetter, J.O., and C.W. Randall. 1965. Bacterial emissions from activated sludge
units. Ind. Med. Surg., 34:130.
5. Napolitano, P.J., and D.R. Rowe. 1966. Microbial content of air near sewage treatment
plants. Water & Sew. Works, 113:480.
6. Ladd, F.C. 1966. Airborne bacteria from liquid waste treatment units. M.S. thesis,
Oklahoma State Univ., Stillwater.
7. Randall, C.W., and J.O. Ledbetter. 1966. Bacterial air pollution from activated sludge
units. Amer. Ind. Hyg. Assn. Jour., 27:506.
8. Kenline, P.A., and P.V. Scarpino. 1972. Bacterial air pollution from sewage plants.
Amer. Indust. Hygiene Assn. Jour., 33:346.
9. Fannin, K.F., K.W. Cochran, H. Ross, and A.S. Monto. 1978. Health effects of a
wastewater treatment system. EPA-600/1-78-062. U.S. Environmental Protection
Agency, Cincinnati, Ohio.
10. Carnow, B., R. Northrop, R. Wadden, S. Rosenberg, J. Holden, A. Neal, L. Sheaff, P.
Scheff, and S. Meyer. 1979. Health effects of aerosols from an activated sludge plant.
EPA-600/1-79-019. U.S. Environmental Protection Agency, Cincinnati, Ohio.
11. Johnson, D.E., D.E. Camann, H.J. Harding, and C.A. Sorber. 1979. Environmental
monitoring of a wastewater treatment plant. EPA-600/1-79-027 U.S. Environmental
Protection Agency, Cincinnati, Ohio.
12. Clark, C.S., G.M. Schiff, C.C. Linnemann, G.L. Van Meer, A.B. Bjornson, P.S. Gart-
side, C.R. Buncher, J. P. Phair, and E.J. Cleary. 1978. A seroepidemiologic study of
workers engaged in wastewater collection and treatment. In: State of knowledge in
Land Treatment of Wastewater, Vol. 2. U.S. Army Corps of Engineers, Hanover,
New Hampshire, August 20-25.
13. Katzenelson, E., I. Buium, and H.E. Shuval. 1976. Risk of communicable disease
infection associated with wastewater irrigation in agricultural settlements. Science,
194:944.
14. Johnson, D.E., D.E. Camann, J.W. Register, R.J. Prevost, J.B. Tillery, R.E. Thomas,
J.M. Taylor, and J.M. Hosenfeld. 1978. Health implications of sewage treatment facili-
ties. EPA-600/1-78-032. U.S. Environmental Protection Agency, Cincinnati, Ohio.
15. Taras, M.J., A.E. Greenberg, R.D. Hoak, and M.C. Rand. 1971. Standard Methods for
the Examination of Water and Wastewater, 13th Edition. American Public Health
Association, Washington, D.C.
16. Rand, M.C., A.E. Greenberg, M.J. Taras, and M.A. Franson. 1975. Standard Methods
for the Examination of Water and Wastewater, 14th Edition. American Public Health
Association, Washington, D.C.
17. Moore, B.E., P.B. Sagik, and C.A. Sorber. 1979. Procedures for the recovery of
airborne human enteric viruses during spray irrigation of treated wastewater. Appl.
andEnv. Microb., 38:688.
18. Blagg, W., E.L. Schloegel, N.S. Mansour, and G.I. Khalaf. 1955. A new concentration
technique to ECHNIC for the demonstration of protozoa and helminth eggs in feces.
Amer. J. Trap. Med. Hyg, 423.
19. American Public Health Association. 1969. Diagnostic Procedures, Viral and Rickett-
sial Infections, E.H. Lennette and N. Schmidt, eds. American Public Health Associa-
tion, Washington, D.C.
-------
158 Wastewater Aerosols and Disease/Contaminants
20. Camann, D.E. 1980. A model for predicting dispersion of microorganisms in waste-
water aerosols. In: Proc. Symposium on Wastewater Aerosols and Disease. U.S.
Environmental Protection Agency, Cincinnati, Ohio, September 19-21,1979.
21. Johnson, D.E., D.E. Camann, C.A. Sorter, B.P. Sagik, and J.P. Glennon. 1978. Aero-
sol monitoring and microbial organisms near a spray irrigation site. In: Proc. Confer-
ence on Risk Assessment and Health Effects of Land Application of Municipal Waste-
water and Sludges. University of Texas at San Antonio. December 12-14, 1977.
22. Johnson, D.E., D.E. Camann, J.W. Register, R.E. Thomas, C.A. Sorter, M.N. Guen-
tzel, J.M. Taylor, and H.J. Harding. 1980. The evaluation of microbiological aerosols
associated with the application of Wastewater to land: Pleasanton, California. EPA-
600/1-80-015. U.S. Environmental Protection Agency, Cincinnati, Ohio.
23. Rylander, R., and M. Lundbolm. 1980. Responses to Wastewater exposure with refer-
ence to endotoxins. In: Proc. Symposium on Wastewater Aerosols and Disease. U.S.
Environmental Protection Agency, Cincinnati, Ohio, September 19-21, 1979.
24. Rylander, R., J. Andersson, L. Berlin, G. Berglund, R. Bergstrom, L. Hanson, M.
Lundbolm, and I. Mattsby. 1976. Sewage worker's syndrome. Lancet, 2:478.
25. Rylander, R., K. Andersson, L. Berlin, G. Berglund, R. Bergstrom, L. Hanson, M.
Lundholm, and I. Mattsby. 1977. Studies on humans exposed to airborne sewage
sludge. Schweiz. Med. Wschr., 107:182.
26. Clark, C.S., G.L. Van Meer, C.C. Linnemann, A.B. Bjornson, P.S. Gartside, G.M.
Schifl, S.E. Trimble, D. Alexander, and E.J. Cleary. 1980. Health effects of occupa-
tional exposure to wastewater. In: Proc. Symposium on Wastewater Aerosols and
Disease, U.S. Environmental Protection Agency, Cincinnati, Ohio, September 19-21,
1979.
DISCUSSION
MR. LINDAHL: In the City of Des Plaines, when this plant was
built, the houses in that area were selling for $40,000 to $50,000 and a
distillery was getting about 400 weekly complaints. Today, those same
houses are selling for $80,000 to $90,000 and the houses are within 150
feet of the plant fence. So, it would be a good opportunity for you to get
some information there. The houses and most of the people living there
were there long before the plant was built.
DR. JOHNSON: Well, you are quite right. We know when we went
in there that this was a rapidly growing area. They put the plant where
there was a convenient place to put it, which was not near people. But
that didn't last very long, and certainly by the end of our study, there
were a lot of new homes very close to the plant; unfortunately, they
were not in our study.
MR. LINDAHL: The present population is about 80,000.
DR. JOHNSON: Thank you.
DR. GERBA: Did the sewage at this plant come from the same com-
munity in which the plant was located?
DR. JOHNSON: Primarily, yes. Finding a plant to obtain data be-
fore and after operation, in the first place, was very difficult. Trying to
find one where they also bring sewage in from a community at a distance
is even more difficult.
DR. GERBA: I think your suggestion is very good and will work if
you will be taking sewage from large metropolitan areas and putting it in
-------
Donald E. Johnson, et al 159
rural areas that are smaller communities. We may really want to study
the health effects of that area.
DR. JOHNSON: I agree.
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160
Wastewater Aerosol and School Attendance
Monitoring at an Advanced Wastewater Treatment
Facility: Durham Plant, Tigard, Oregon
David E. Camann,
H. Jac Harding,
Donald E. Johnson
Southwest Research Institute
San Antonio, Texas
ABSTRACT
As the first stage of a potential health hazard investigation, wastewater aerosols and
school attendance were monitored at an advanced wastewater treatment plant using the
activated sludge process An elementary school is located next to the new treatment plant.
Wastewater aerosols are generated by the aeration basin (within 400 m of the classrooms)
and by an aerated surge basin (within 50 m of the school playground).
The aeration basin was observed to be a much stronger source of aerosolized microor-
ganisms than the surge basin. The geometric mean concentrations monitored in air at 30 to
50 m downwind of the aeration basin were 12 cfu/m3 of total coliforms, 4.2 cfu/m3 of fecal
streptococci, 19 cfu/m3 of mycobacteria, and 1.5 pfu/m3 of coliphage. Enteroviruses were
not detected in air (<0.0002 pfu/m3).
After sewage treatment commenced, attendance at the nearby school generally im-
proved, relative both to the baseline school years and to five control schools. The students
probably received a peak dose from the aerosol on the order of 2 cfu of mycobacteria and
0.8 cfu of fecal streptococci. At this level of exposure, the sewage treatment aerosol
had no adverse effect on communicable disease incidence as discerned from total school
absenteeism.
INTRODUCTION
Background
To improve the quality of surface waters, the U.S. Environmental
Protection Agency is sponsoring a large program of local construction
grants for new wastewater treatment plants. Siting requirements and
urban sprawl often dictate that the new wastewater treatment units be
located near residential areas.
The Durham Advanced Wastewater Treatment Plant (DAWTP) in
Tigard, Oregon, is a modern activated sludge plant funded by the con-
struction grants program that processes 9 to 13 mgd of sewage (3 to 5 x
107 I/day). It was built next to the six-classroom Durham Elementary
School (DES). The school buildings are located 370 to 470 m from the
aeration basin, while the school playground extends to within 50 m of
the nearest aerator in one of the surge basins. Local public health offi-
cials were concerned that operation of the DAWTP so near the school
-------
David E. Camann, et al 161
might facilitate the spread of infectious disease among the school chil-
dren, especially since "foam blobs" from the aerated surge basin occa-
sionally settled on the playground.
Aeration basins can produce large amounts of wastewater aerosol
which may contain many of the pathogenic microorganisms present in
the raw sewage. The mechanical aerators used in the surge basin also
generate wastewater aerosol. Since these basins are not enclosed, the
wastewater aerosol could be carried by the wind into the classroom area
and onto the playground. If a sufficient dose were inhaled, the pathogens
in the wastewater aerosol might initiate infection in susceptible
students.
Two environmental epidemiology studies have recently been per-
formed in the Chicago area, by Northrop and coworkers (1) and by
Johnson et al. (2,3) to investigate possible infectious disease effects to
populations living near large activated sludge treatment facilities. In
both studies, measures of the health of the people living near the plant
were compared to those of matched populations living farther away
from the plant. Various respiratory and gastrointestinal infectious di-
seases that might be associated with exposure to aerosols containing
microorganisms from the sewage treatment plant were examined via
serology, symptom incidence, and isolates from clinical specimens. In
general, both studies found little evidence of detectable health effects.
This may be because both studies lacked enough sensitive participants
who lived sufficiently close to the aeration basins to receive substantial
exposure to the wastewater aerosol.
The siting of the DAWTP next to DBS was of sufficient public health
concern to warrant some investigation. The quality of information to be
derived from field monitoring and local school attendance records per-
mitted a cost-effective initial investigation. Depending upon its out-
come, a more complete study could then have been made of infectious
disease health effects of wastewater aerosols among this population of
young children who spent a large portion of their active time (approxi-
mately 35 hr/week for 9 months of the year) within a quarter of a mile of
an activated sludge plant's aerosol source. The initial investigatory
study (4) presented here was conducted to monitor microorganisms in
the wastewater aerosols from the DAWTP aeration and surge basins and
to evaluate the existing school attendance data.
Study Objectives
The primary objective was to monitor the type and quantity of mi-
croorganisms in the wastewater and in the ambient air upwind and up to
100 m downwind of the DAWTP. From these data, an evaluation was to
be made of microorganism levels in the wastewater aerosol transported
into the school environment.
A secondary objective was to determine whether the absentee rate at
DES was significantly different from the absentee rates at control
schools located in the same area but not near a wastewater treatment
facility. The intent was to provide some preliminary indication of possi-
ble health effects which might be associated with the sewage treatment
aerosol.
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162 Wastewater Aerosols and Disease/Contaminants
Study Design
The environmental monitoring was performed in two phases. In Phase
1 (November 1977) large samples of wastewater were collected from the
two potential sources of aerosolized microorganisms at the plant: the
aeration basin and the aerated surge basin. Both wastewater samples
were screened to characterize the type and approximate concentration
of enteroviruses and a variety of enteric bacteria. The microorganisms
to be routinely monitored in the wastewater aerosol during the second
phase were then selected. In addition, the relative levels of various test
organisms present in the two aerosol sources in the plant were compared
in order to determine which source would be the focus of the aerosol
sampling.
In Phase 2 (March 1978), six aerosol runs were conducted to simulta-
neously measure levels of microorganisms in wastewater and air at the
aeration basin and the surge basin. A special enterovirus aerosol run was
also conducted to measure enterovirus aerosol levels at the aeration
basin. The concentration and frequency of microbial aerosols reaching
the school were estimated.
Five suitable control schools for DES were selected. Standardized
data on quarterly attendance at the six schools were obtained for the
seven school years prior to DAWTP operation and for the first two
school years of DAWTP operation. If the DAWTP had an adverse
health effect, one would expect to see high absenteeism at DES (relative
to the control schools) in the two operational years. Such absenteeism
might take the form of a uniformly higher absence rate throughout the
two operational years, or because of acquired immunity, it might only be
evident during the first several months of aerosol exposure episodes.
STUDY SITE
Durham Advanced Wastewater Treatment Plant (DAWTP)
The Durham Advanced Wastewater Treatment Plant (DAWTP) is op-
erated by the Unified Sewerage Agency and serves part of the south-
western suburbs of Portland, Oregon (see Figure 1). The DAWTP is an
activated sludge plant with a design capacity of 75,000 m3/day (20) (see
Figure 2).
Treatment Process
The treatment process consists of barminutors to screen out and re-
duce the size of large objects, primary clarification where settleable
solids and grit are removed, and aeration in an aeration basin with acti-
vated sludge. These processes are followed by secondary clarification
and chemical clarification using alum and coagulant aids to reduce the
phosphorus and solids content. The final steps are filtration and chlorin-
ation prior to discharge into the Tualatin River. Organic sludge from the
primary and secondary clarifiers is processed, heat treated, and inciner-
ated; the resulting ash is used for landfill.
Surge basins of 38,000 m3 (10 million gallon) and 19,000 m3 (5 million
gallon) capacity accommodate primary clarifier effluent during periods
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David E. Camann, et ai
163
SOUTHWESTERN SUBURBS OF
PORTLAND,OREGON
SCALE OF MILES
0 0.5 1
LAKEOSWEGO
DAWTP
DURHAM ELEMENTARY SCHOOL (DES)
,C) CONTROL SCHOOL
Figure 1. Study Area
of high flow. Surface aerators are used to prevent the stored wastewater
from becoming anaerobic. During periods of low influent flow, waste-
water from the surge basins is reintroduced into the treatment process to
equalize flow through the secondary and tertiary treatment sections of
the plant.
-------
164
Wastewater Aerosols and Disease/Contaminants
CH
DURHAM
ELEMENTARY
SCHOOL
100
200
300
Figure 2. Durham Advanced Wastewater Treatment Plant (DAWTP)
and Durham Elementary School (DBS)
Microbial Aerosol Sources During Sampling Periods
The aeration basin and the surge basin were determined to be the
major sources of microorganism-laden wastewater aerosols. In the
3,800 m3 (1 million gallon) capacity aeration basin, all wastewater is
mixed with activated sludge. Two mechanical turbine mixers agitate the
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David E. Camann, etal 165
aeration basin liquor and disperse an air stream that is introduced
through a 10-cm diameter nozzle oriented vertically upward underneath
each turbine at a distance of 1.5m from the bottom of the basin.
The three electro-mechanical surface aerators on the No. 1 surge
basin (19,000 m3 capacity) also produced wastewater aerosol during
Phase 2. No wastewater was diverted to or removed from it during the
aerosol monitoring.
Study Schools
Durham Elementary School (DES)
The school attendance portion of the study focused on Durham Ele-
mentary School (DES), a small six-classroom school (one room for each
grade level, one through six) in the Tigard School District which was
situated adjacent to the DAWTP. As Figure 2 illustrates, the school
buildings are about 370 to 470 m northeast of the DAWTP aeration basin
and about 200 m north of the plant's aerated surge basins. Since the
school has no air conditioning or forced air circulation, the windows are
opened to provide ventilation and cooling during warm weather. The
school playground behind the classrooms borders the DAWTP property
and extends to within 50 m of an aerator in the closest surge basin.
Year-end enrollment in June 1978 was 123 students. Historically about
60% of the students attend all six grades at Durham Elementary. Nearly
all students are white and from families in the middle to upper-middle
income bracket, with 40 to 45% residing in apartments. During the time-
frame of the attendance study (September 1969 through June 1978),
DES had very little teacher turnover. However, new principals were
installed in July 1974 and again in July 1976.
Control Elementary Schools
In order to assess the potential health hazard of the DAWTP as re-
flected in school attendance at the nearby DES, elementary schools not
located near the sewage treatment plant were sought for use as controls.
The matching criteria employed were racial distribution, socioeconomic
status, attendance recording system, and degree of urbanization. Using
these criteria, the remaining five elementary schools in the Tigard
School District were selected as control schools. The map in Figure 1
shows the general locations of DES and the control schools relative to
the DAWTP.
General Characteristics of Schools
Relevant characteristics of the schools are summarized in Table 1.
The students attending all the schools were predominantly white, with
less than 1% black and Indian and about 1% Oriental. However, DES
had a smaller enrollment and served a more rural area than any of the
control schools. The socioeconomic status and the proportion of stu-
dents dwelling in apartments was higher for DES than for some of the
control schools.
-------
166
Wastewater Aerosols and Disease/Contaminants
Table 1. Background Information on Schools in School Attendance
Study
Elementary Distance and direction from End of year School Students Socio-
school Durham plant aeration basins enrollment ventilation living in economic
(grades 1-6) Distance (km) Direction (June 1978) system apartments status"
Durham
04
NE
123
Open windows* 40%-45%
(Many)
M-UM
Lewis
Metzger
Templeton
Tigard
Tualatin
31
50
1 6
30
28
NNE
N
NNW
NNW
S
282
426
556
648
566
Combination'
Combination
Forced air'
Combination
Combination
Many
Few
Few
Few
Many
LM-M
L-M
M-UM
L-UM
M-UM
"Socioeconomic status categones, based on value of home
L - lower class
LM - lower - middle
M - middle class
UM - upper - middle
''Open window - the windows are opened to provide ventilation for cooling and air circulation
• Combination - schools having forced air system but often using open windows
'' Forced air - fans are used to force fresh air through the ventilation system
METHODS AND MATERIALS
Sample Collection
Meteorological Measurements
During the period of aerosol sampling, wind speed and direction,
temperature and relative humidity were measured at heights of 2 and 10
m in the vicinity of the aeration basin. Field measurements of solar
radiation and cloud cover were also made.
Wastewater Samples
Time-weighed 24-hour composites were collected from the aeration
basin and the No. 1 surge basin in Phase 1. Wastewater samples were
also collected from these two aerosol sources during each aerosol run.
High Volume Air Samples
The Litton Model M large-volume air sampler (LVAS) was used to
collect microbial aerosol samples. The sampler collected airborne parti-
cles by electrostatic precipitation and concentrated them into a thin,
moving film of a liquid medium (brain-heart infusion (BHI) broth with
0.1 percent Tween 80). The LVAS sampled 1.0 m3/min of air while
recirculating the BHI medium at 5 ml/min. Before each aerosol run, the
samplers were decontaminated using both absolute ethanol and buffered
1% Chlorox1*. The average microorganism collection efficiency of these
samplers was 48%.
Air Sampling Protocols
Microbiological Aerosol Runs—
The objective of the microbiological aerosol runs was to simulta-
neously measure the microorganism levels and their viability decay from
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David E. Camann, et al
167
the two sources of aerosol: the aeration basin and the No.l surge basin.
As shown in Figure 3, eight LVAS were deployed in pairs as close as
possible to four planned locations (upwind, 50 m downwind of the surge
basin, and 30 m and 100 m downwind of the aeration basin) when the
wind direction was relatively constant and there was no precipitation.
The LVAS were operated simultaneously for 30 min to constitute a
microbiological aerosol run. Samples were shipped from the field site to
the laboratory for assay within 28 hours after collection.
// ADMINISTRATION
V BLDG
WIND DIRECTION
MAIN POWER
SUBSTATION
AEROSOL SOURCE
XX AEROSOL SAMPLER PAIR
0 METEOROLOGICAL STATION
Figure 3. Typical Microbiological Aerosol Run
-------
168 Waste water Aerosols and Disease/Contaminants
Enterovirus Aerosol Run—
To provide the necessary sensitivity to detect enteroviruses in the
wastewater aerosol, eight LVAS were operated simultaneously in close
proximity to each other at 30 m downwind from the aeration basin for
nine consecutive 30-min periods. The BHI medium was changed at the
end of each 30-min period. At the conclusion of aerosol collection, all
the samples were pooled, concentrated in the field, and shipped for
assay.
Analytical Methods
Microbial Wastewater Screen
The microbial screen of the wastewater in Phase 1 involved semiquan-
titative analysis for specific enteric organisms. Both Salmonellae (in-
cluding Arizona) and Shigella were assayed by methods described in
Standard Methods (5), which involved concentration by filtration, en-
richment, and direct plating on selective media. Proteus was determined
by directly plating serial dilutions of the sample onto moderately selec-
tive and highly selective enteric media. Staphylococcus aureus was as-
sayed by spread plating directly to previously solidified plates of manni-
tol salt agar. Quantitation of Klebsiella was determined by employing its
ability to produce large mucoid colonies on differential enteric media
containing a high concentration of carbohydrate (e.g., eosin methylene
blue agar).
Members of the other genera of Enterobacteriaceae (i.e., Enterobac-
ter, Serratia, Edwardsiella, Escherichia, Citrobacter, Providencia and
Yersinia) were determined by picking colonies from samples dilution-
plated to moderately selective and highly selective enteric plating media.
Yersinia enterocolitica was determined by selective enrichment of mem-
brane filter-concentrated samples plated to Salmonella- Shigella agar.
Microbiological Assay
Both total coliforms and fecal coliforms were determined by filtration
and direct plating on selective media in accordance with Standard Meth-
ods (6). After filtration of the sample, fecal streptococci was directly
counted after plating on M—Enterococc'us agar (Difco). Total plate
count was determined by serial dilution and direct count. Mycobacteria
were assayed quantitatively by a procedure which almost totally sup-
pressed sewage saprophytes while permitting recovery of most myco-
bacteria. This procedure involved sample processing, selection of colo-
nies, preliminary screen, subculture, and further tests for identification.
By using a direct and quantitative approach, fluorescent pseudomonads
were assayed by dilution and direct plating on Pseudomonas Agar F
(Difco). Coliphage were assayed with Escherichia coli K-13 as host in
tryptose phosphate agar.
Enterovirus analysis of wastewater samples involved separation
into liquid and solid phases, concentration onto bentonite clay and
enumeration on HeLa and Buffalo Green Monkey (BGM) monolayers.
-------
David E. Camann, et al 169
Enterovirus Aerosol Sample Assay
The enterovirus study employed a two-stage procedure (field concen-
tration and assay) (7). Field concentration involved classical two-phase
polymer separation. Final assay was conducted on the lower phase and
interphase from the field concentration volumes utilizing HeLa and
BGM monolayers.
Chemical and Physical Analyses
Total organic carbon analyses were conducted on acidified homogen-
ized wastewater samples (6). Total suspended solids and total volatile
suspended solids were determined on wastewater sample aliquots (6).
Data Evaluation Methods
School Attendance Data
An accurate and uniform attendance accounting system has been
maintained since 1969 for each elementary school in the Tigard School
District. The cumulative school attendance data reported to the state for
the school years from 1969 to 1970 through 1977 to 1978 were utilized.
These data were the total child-days present and absent during each
calendar quarter at each school (grades 1 through 6 combined). The
percent absent statistic defined as the total days absent divided by total
days present and absent was used in the data analysis. To permit a class
cohort analysis, these same attendance statistics were obtained for each
grade from the local records at DBS and the two nearest and socioecon-
omically similar control schools (Templeton and Tualatin).
Aerosol Exposure
The aerosol exposure of DES students was estimated from a mathe-
matical model of the aerosol monitoring data and from the wind direc-
tion readings for each school day, since the school was too distant from
the aeration basin for direct aerosol sampling. A rough estimate of the
highest dose of aerosolized microorganisms inhaled 1 school day/year
was obtained as the product of the highest predicted air concentration
during a school day, the student breathing rate, and the duration of
exposure.
The estimation procedures for the general form of the microbiological
dispersion model when there are two downwind sampler distances (8)
were used to compute viability decay rates and predicted downwind air
concentrations during each microbiological aerosol run. An index of
exposure to aerosols was determined each school day using the 3-hr
wind direction readings from the National Weather Service. Based on
the number of school days of steady exposure, the percentile corre-
sponding to the highest predicted air concentration at the school dis-
tance was selected from the distribution of model predictions during the
aerosol runs.
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170 Wastewater Aerosols and Disease/Contaminants
RESULTS
Field Monitoring of Wastewater Aerosol
Microbial Characterization of Wastewater
Results of microbial screens and assays of potential test organisms for
large volume wastewater samples collected during Phase 1 from the
aeration basin and the surge basin are presented in Table 2. The levels
shown for the microbial screen are minimal values since only a portion
of the total number of colonies counted on a given media were con-
firmed. The actual microorganism concentration might have been any-
where from the indicated value to an order of magnitude higher. Myco-
bacteria and Klebsiella levels were fairly high relative to the
microbiological indicators, whereas Salmonella and Shigella were not
prevalent.
Table 2. Analysis of Large Samples of Wastewater (Phase 1)
Aeration basin Surge basin
Levels of test organisms (cfu/ml)"
Total plate count
Total coliforms
Fecal coliforms
Fecal Streptococci
Mycobactena
Pseudomonas
Coliphage (pfu/miy1
Enteroviruses (plu/ml)
Microbial screen (serniquantitative cfu/ml)
Citrobacter sp
Enterobacter sp
Eschenchia coli
Klebsiella sp
Proteus sp
Providencia sp
Salmonella sp
Serratia sp
Shigella sp
Staphylococcus sp
Yersmia
4,800,000
1,800
530
67
13,000
230
61
074
70
500
70
400
<30
<30<
<3O
70
<0.008
3
<0.07<
210,000
1,100
160
13
9,700
100
<02-
0009
30
200
10
40
0
<3c
<0.001C
3
<0001'
-------
Da vid E. Camann, et al 171
Table 3. Concentrations in the Wastewater During Aerosol Runs
(Geometric Mean)
Aeration basin Surge basin
Bacteria (cfu/ml)
Total colrforms
Fecal Streptococci
Mycobacteria
Pseudomonas
Viruses (pfu/ml)
Coliphage
Enteroviruses
Physical and chemical characteristics (mg/l)
Total suspended solids
Total volatile suspended solids
Dissolved oxygen
Total organic carbon
450,000
4,500
59,000
1,500
690
050
1,800
940
1 7
390
44
53
320
1,200
03
0002
100
44
—
49
Table 4 presents the mean concentrations of microorganisms in the air
upwind and at the sampled distances downwind from the aeration and
surge basins during the aerosol runs in Phase 2. The microorganism air
concentrations tended to decrease with increasing downwind distance
from the wastewater aerosol source. The microorganism air concentra-
tions also tended to vary from one aerosol run to another due partially to
variations of microorganism levels in the wastewater.
The downwind air concentrations of fecal streptococci and mycobac-
teria indicate that there were many potentially pathogenic bacteria in the
DAWTP aeration basin aerosol and considerable mycobacteria in the
surge basin aerosol. The air densities of these potentially pathogenic
bacteria were generally as high or higher than the densities of such
indicator organisms as total coliforms and coliphage at 70 to 100 m
downwind of the aeration basin. Thus, the use of indicator microorgan-
isms such as total coliforms or coliphage in wastewater aerosol monitor-
ing appears to be inadequate to characterize the pathogenicity of the
aerosol.
Enterovirus Aerosol Level
No enteroviruses were found 30 m downwind of the DAWTP aeration
basin in the total sampled air volume of 1980 m3. Thus, the enterovirus
aerosol concentration was less than 0.002 pfu/m3 (plaque forming units
per cubic meter).
Table 4. Concentrations in the Air During Aerosol Runs
(Geometric Mean)
Downwind of Aerosol Source
Aeration Basin
Total coliforms (cfu/m3)
Fecal Streptococci (cfu/m3)
Mycobactena (cfu/m3)
Coliphage (pfu/m3)
Enteroviruses (pfu/m3)
30-50 m
12.2
4.2
19.1
1.5
<0.002
70-1 00m
1.7
1.1
4.2
0.6
Surge Basin
55-95 m
0.15
<0.02
0.32
<0.04
Upwind
(Presumed
Background)
<0.02
0.06
<0.02
<0.04
-------
172 Wastewater Aerosols and Disease/Contaminants
School Attendance
Annual Comparison
The annual percent absent at DES and the combined control schools
are plotted in Figure 4 as two time series. This illustrates that DES
historically has tended to have higher levels of absenteeism than the
control schools. In the two years after the DAWTP began operation, the
absence percentages at DES and the control schools both decreased.
During DAWTP operation, attendance at DES improved to a level very
close to the attendance at the control schools.
In Table 5, the percent absent in the 2-year operational period is
compared to the percent absent in the last 2 years of the baseline period.
While a slight decrease in absenteeism occurred at the control schools
(-0.32%), DES had a stronger decrease in absenteeism (-0.69%).
If DAWTP operation had had a sustained adverse effect on the health
of DES students, an increase might have been anticipated in the absen-
tee rate at DES relative to the control schools in the DAWTP operation
years. In contrast, the annual attendance rate at DES improved, both in
a simple numerical sense and in relation to control school attendance.
Quarterly Comparison
To examine more transitory health effects, quarterly time series of
percent absent at DES and the combined five control schools are pre-
sented in Figure 5. There is a pronounced seasonal pattern. The lowest
percentage of absences always occurred in the first calendar quarter
(September) and the highest absentee percentage usually occurred in the
third calendar quarter (January through March). There were no pro-
nounced differences in quarterly absentee percentages between DES
and the control schools after the DAWTP began operation.
Class Cohort Comparison
To investigate any patterns obscured in the grouped absentee rates for
grades one through six, differences in absenteeism in class cohorts (i.e.,
children in the same grade level at DES and two similar control schools)
were compared using quarterly time series over their years in elemen-
tary school. Various DES classes had prolonged periods of higher ab-
senteeism than their control class cohorts, particularly during the base-
line. After the DAWTP was operating, there were several periods of
slightly higher absenteeism among first and second grade students at
DES.
Table 5. Absenteeism Comparison Over Two Year Periods
Absenteeism (%)
Last two DAWTP
baseline operation Operation
years years effect (%)
Durham Elementary 5 36 4 67 -0.69
Control schools 496 4.64 -0.32
-------
PERCENT ABSENT
.DURHAM ELEMENTARY SCHOOL (DES)
.FIVE TIGARD CONTROL SCHOOLS
BASELINE PERIOD
I
69-70
70-71
71-72
I
72-73
7374
I
74-75
75-76
g
H
<
i
Q
I
03
a
6!
OPERATIONAL
PERIOD
76-77 77-78
SCHOOL YEAR
Figure 4. Annual Attendance Plot for DES and the Tigard Control Schools
-------
10
g
8
7
6
5
4
3
2
1
0
PERCENT ABSENT
DURHAM ELEMENTARY SCHOOL (DES)
FIVE TIGARD CONTROL SCHOOLS
I
I
1
I
l
I l
1234123412341 234123412341234
69-70 70-71 71-72 72-73 73-74 74-75 75-76
O-
O
CO
z
O
LJJ
CD
O.
<
Q
2341234 QUARTER
76-77 77-78 SCHOOL YEAR
Figure 5. Quarterly Attendance Plot for DES and the Tigard Control Schools
-------
David E. Camann, et al 175
Aerosol Exposure of DES Students
Model Predictions at DES Distance During Aerosol Runs
The rates of viability decay of microorganisms in the aerosol from the
DAWTP aeration basin were determined during the six microbiological
aerosol runs. The distributions of the viability decay rates are presented
in Table 6. With so few runs, no significant difference in viability decay
rates could be detected for the DAWTP aeration basin aerosol in com-
parison to a thoroughly monitored sprinkler irrigation aerosol (9).
Model predictions were made of the microorganism concentrations in
air at the school distance (450 m) on the centerline downwind from the
aeration basin during each aerosol run. There are probably one or more
magnitudes of uncertainty in each model prediction of the air concentra-
tion at such a large downwind distance (8,4). The distributions of the
model predictions for fecal streptococci and mycobacteria are presented
in Table 7. They are also contrasted in Table 7 with the background
outdoor concentrations estimated from the upwind air samples. It ap-
pears that the aeration basin aerosol appreciably increases the air con-
centration of fecal streptococci and mycobacteria above the background
levels normally inhaled by the students. This occurs about half of the
time that the DES classrooms are downwind of the DAWTP aeration
basin.
Table 6. Estimates of Viability Decay RateXFrom DAWTP Aeration
Basin
Distribution of \ (seer1) values
Percentile Total coliforms Fecal Streptococci Mycobacteria Coltphage
25
50
75
-0059
-0043
-0.035
-0051
-0.027
"
-0057
-0.041
"
-0054
"
"
"Indeterminate viability decay rate; for model calculations, * may be presumed to represent X
O.Osec-i
Table 7. Model-predicted Air Concentrations At School Distance from
DAWTP Aeration Basin
Distribution of Model-predicted concentrations
P450(cf u/m3) at 450 m from aeration basin
Percentile Fecal Streptococci Mycobacteria
25 4 x 10-" 4 x 10-6
50 6x 10-" 8x 10-s
75 0.17 0.40
83 0.42 0.92
Estimated Background 0.06 <0.02
-------
176 Wastewater Aerosols and Disease/Contaminants
Frequency and Persistence of Aerosol Exposure at DES
The distribution of the exposure of DES students to DAWTP aerosols
is presented in Table 8. The classroom area was steadily downwind of
the aeration basin on only 10 school days in the 2 operational years. All
of these days were rainy, cloudy, cool, and humid (i.e., conditions con-
ducive to survival of aerosolized microorganisms between the showers).
Because of rainfall, the DES students may have used their playground
on only about 40% of the days when it was steadily exposed to aerosols.
The first school days on which the playground received steady exposure
to the surge basin aerosol were in December 1976. The classroom area
was not steadily exposed until February 1977.
Estimated Maximum Inhaled Dose of Aerosolized Microorganisms
The calculation of the highest dose of aerosolized microorganisms
likely to be inhaled during one school day per year is presented in Table
9. Considering the assumptions and data extrapolations involved, each
dose estimate could well be a factor of 10 higher or lower than the value
calculated in Table 9.
The highest inhaled doses received one school day per year, both in
the classroom and on the playground, were probably on the order of 0.8
cfu (colony forming units) of fecal streptococci and 2 cfu of mycobac-
teria. The majority of the peak school day dose was probably inhaled in
the classroom area. The peak inhaled dose of about 0.8 cfu/day of fecal
streptococci from the DAWTP aerosol is not much larger than the esti-
mated usual background dose (about 0.13 cfu/day) from other sources in
the school area. However, the peak inhaled dose of about 2 cfu/day of
mycobacteria from the aerosol appears to be larger than the usual back-
ground dose of mycobacteria.
DISCUSSION
The aeration basin was observed to be a much stronger source of
aerosolized microorganisms than the surge basin. The geometric mean
aerosol concentrations at 30 to 50 m downwind of the aeration basin
were 12 cfu/m3 of total coliforms, 4.2 cfu/m3 of fecal streptococci, 19
cfu/m3 of mycobacteria, 1.5 pfu/m3 of coliphage, and <0.002 pfu/m3 of
enteroviruses. Aerosolized mycobacteria were found to be more preva-
lent at this plant than at previously monitored sites (9,3). The inability to
detect enteroviruses in air resulted from their low concentration (rela-
tive to other test organisms) in the wastewater and from their absorption
onto and incorporation into the mixed liquor suspended solids which are
not easily aerosolized.
After the DAWTP began sewage treatment, overall attendance at
DES actually improved, relative both to baseline attendance at DES and
to attendance at the five control schools. Although school absenteeism
may reflect many factors besides illness, it can be an efficient measure of
infectious disease incidence when such other major confounding factors
as socioeconomic status and annual weather differences are properly
controlled (10). Thus, DAWTP operation had no discernible adverse
-------
David E. Camann, etal
177
Table 8. Frequency and Persistence of DBS Student Exposure by
Calendar Quarter
School day
exposure index
Number of school days
1Q
1976-77
2Q 3Q
4Q
1Q
1977-78
2Q 3Q
4Q
Percent
Both of
school school
years days
Exposure of classroom area to aeration basin aerosol
O(None) 11 30 30 25 6 27 42 25 196 55
1-2 (Occasional) 6 17 14 9 6 12 8 11 83 23
3-4 1 5 5 9 4 7 5 7 43 12
5-6 02553314236
7-8 (Steady) 00400 501 10 3
Exposure of playground area to surge basin aerosol
0 (None)
1 -2 (Occasional)
3-4
5-6
7-8 (Steady)
11
5
2
0
0
24
17
5
5
3
18
20
7
5
8
23
9
7
7
2
6
5
3
2
3
15
12
13
7
7
19
17
14
5
1
21
11
9
4
3
137
96
60
35
27
39
27
17
10
8
effect on the incidence of communicable illness as reflected by total
school absenteeism. The slight improvement in DBS attendance may
have been produced by some unrecognized factor. One possible expla-
nation is the change in principal coincident with initial DAWTP opera-
tion (i.e., the young new principal was observed to interact closely and
positively with the students of his small school).
Table 9. Estimated Maximum Daily Dose of Aerosolized Microorgan-
isms Inhaled by Students at DES
Highest expected dose per year from DAWTP
From aeration basin From surge basin
In classroom area At playground At playground
Usual
background
dose
"Normal
outdoors"
Distance from aerosol source
School days per year of steady
Exposure (from Table 8)
Percentile of highest day
Estimated mean air concentra-
tion on highest day (cfu/m3)
Fecal Streptococci
Mycobactena
Student breathing rate (m3/hr)
Duration of exposure (hr/day)
Estimated dose inhaled on
highest day (cf u/day)
Fecal Streptococci
Mycobactena
450m
5
83%
OA2b
0.92*
025'
7
0.74d
16"
300m
3"
75%
0.36fc
0.88b
043C
1
0.15"
0.38?
50
5"
83%
0.90"
043'
1
<0.06d
0.391*
177
0.06*
<0.02"
0.27<
8
0.13d
<0.04d
"Excluding days playground not usable due to ram
fc Assumes conditions sampled during one week monitoring period reflect both the levels and variability
encountered in first two years of DAWTP operation
'Assumes an average child body surface area of 1 0 m2, an at-rest breathing rate of 3 6 l/min/m2, a
classroom rate 15% above at-rest, and playground rate twice the at-rest rate
d Estimated inhaled dose = Air concentration x breathing rate x exposure duration. Each dose estimate
is subject to at least an order of magnitude of uncertainty.
-------
178 Wastewater Aerosols and Disease/Contaminants
The DBS students may have received added exposure through
DAWTP aerosols to such potential pathogens as mycobacteria and fecal
streptococci on perhaps 10% of the school days after the DAWTP began
operation. The peak doses inhaled from the aerosol about 1 school day/
year were probably on the order of 2 cfu of mycobacteria and 0.8 cfu of
fecal streptococci.
While DAWTP operation has had no discernible adverse effect on
communicable disease incidence, continued limited health monitoring of
the DBS students appears to be warranted. Several periods of increased
absenteeism of dubious significance were observed among first and sec-
ond grade students at DES after the DAWTP began operation. Contin-
ued surveillance of school attendance, especially among the younger
children, should be maintained for DES and the control schools beyond
the 1977-78 school year to determine if this is a recurring pattern.
ACKNOWLEDGEMENT
The research on which this paper is based was supported by the U.S.
Environmental Protection Agency, Health Effects Research Labora-
tory, Cincinnati, Ohio, under Grant R 805533.
References
1. Carnow, B., R. Northrop, R. Wadden, S. Rosenberg, J. Holden, A. Neal, L. Sheaff, P.
Scheff, and S. Meyer. 1979. Health effects of aerosols from an activated sludge plant.
EPA-600/1-79-019, U.S. Environmental Protection Agency, Cincinnati, Ohio.
2. Johnson, D.E., D.E. Camann, K.T. Kimball, R.J. Prevost, and R.E. Thomas. 1980.
Health effects from wastewater aerosols at a new activated sludge plant: John Egan
Plant, Schaumburg, Illinois. In: Proc. National Symposium on Wastewater Aerosols
and Disease. U.S. Environmental Protection Agency, Cincinnati, Ohio, September
19-21, 1979.
3. Johnson, D.E., D.E. Camann, J.W. Register, R.J. Prevost, J.B. Tillery, R.E. Thomas,
J.M. Taylor, and J.M. Hosenfeld. 1978. Health implications of sewage treatment facili-
ties. EPA-600/1-78-032, U.S. Environmental Protection Agency, Cincinnati, Ohio.
4. Johnson, D.E., D.E. Camann, H.J. Harding, and C.A. Sorber. 1979. Environmental
monitoring of a wastewater treatment plant. EPA-600/1-79-027, U.S. Environmental
Protection Agency, Cincinnati, Ohio.
5. Taras, M.J., A.E. Greenberg, R.D. Hoak, and M.C. Rand. 1971. Standard Methods for
the Examination of Water and Wastewater. 13th Ed. American Public Health Associa-
tion, Washington, D.C.
6. Rand, M.C., A.E. Greenberg, M.J. Taras, and M.A. Franson. 1975. Standard Methods
for the Examination of Water and Wastewater. 14th Ed. American Public Health
Association, Washington, D.C.
7. Moore, B.E., B.P. Sagik, and C.A. Sorber. 1979. Procedures for the recovery of
airborne human enteric viruses during spray irrigation of treated wastewater. Appl.
Environ. Microb. 38:688.
8. Camann, D.E. 1980. A model for predicting dispersion of microorganisms in waste-
water aerosols. In: Proc. National Symposium on Wastewater Aerosols and Disease,
U.S. Environmental Protection Agency, Cincinnati, Ohio, September 19-21, 1979.
9. Johnson, D.E., D.E. Camann, J.W. Register, R.E. Thomas, C.A. Sorber, M.N.
Guentzel, J.M. Taylor, and H.J. Harding. 1980. The evaluation of microbiological
aerosols associated with the application of wastewater to land: Pleasanton, California.
EPA-600/1-80-015, U.S. Environmental Protection Agency, Cincinnati, Ohio.
10. Miday, R.K. 1980. Epidemiologic approach to disease assessment. In: Proc. National
Symposium on Wastewater Aerosols and Disease, U.S. Environmental Protection
Agency, Cincinnati, Ohio, September 19-21, 1979.
11. Steadham, J.E. 1980. High catalase strain of Mycobacterium kansa.su isolated from
water in Texas. Jour. Clin. Microb. (in press).
-------
David E. Camann, et al 179
DISCUSSION
SPEAKER: I want to ask you, Mr. Camann, why are these treatment
plants being built? Where was the sewage going before it was going to
the sewage treatment plant?
MR. CAMANN: Well, at the Durham site there were a number of
small sewage treatment plants throughout this area. The service area is
now served by this modern plant, and sewage was consolidated into this
one plant to improve the effluent characteristics and improve the Tuala-
tin River, into which the wastes were dumped.
MR. SAWYER: I've got a couple of questions relating to the source
strength. Am I to conclude that you are saying that it is not possible to
directly determine the source strength from aeration basin strength?
MR. CAMANN: I have not ever seen such a calculation done be-
cause you cannot calculate the diffusion pattern very close to the
source. So the best thing to do is to take an aerosol sample close enough
downwind where decay has not been a major factor and yet where the
diffusion has gotten into a stable pattern, so that you can diffusion model
it. That is the approach that I have seen done in other places and that is
the approach I took.
MR. SAWYER: The second thing is that on one of the slides that you
showed, I don't remember the exact number, but I think it was some-
thing like 92.3 cfu/m3. When you do a mathematical model, and your Q
represents source strength, that term has to be defined in terms of an
emission rate per unit time, and not in terms of the concentration factor,
which is what you gave. Even using your back calculation, can you say
what is the emission rate from those factors?
MR. CAMANN: I was not interested in trying to do the calculation. I
really could not tell you offhand. I would have to look at it.
MR. SAWYER: Do you think it would be possible to get those kinds
of terms from your data?
MR. CAMANN: I am not positive that I've got all the relevant infor-
mation which might be required. I know that we did not do it to the
extent of diffusion modeling at this site because it was expensive and
this was a limited study. I think it would be possible to do the back
calculation from our aerosol values. It would be a fairly extensive time-
consuming operation and beyond the scope of this monitoring approach.
DR. SORBER: To help answer that particular question you could get
this emission rate if you had an estimate of impact factors of that aera-
tion basin, which is difficult to do in modeling. You are assuming the
combination of emission rate and impact factor at the close in location.
MR. CAMANN: Right. The Q would take into account both things
and would not be able to distinguish among various parts of it.
DR. SORBER: That's right. There is no way we could do that at this
particular site and to identify the impact factors separately. We haven't
been able to do that. We can calculate the rate per square foot.
-------
180
Health Effects of Aerosols Emitted from an Activated
Sludge Plant
R. Northrop, B. Carnow, R. Wadden, S. Rosenberg, A. Neal,
L. Sheaff, J. Holden, S. Meyer, and P. Scheff
University of Illinois School of Public Health
Chicago, Illinois
ABSTRACT
An 8-month environmental health study was carried out in a 1.6 km area surrounding a 202
mgd activated sludge plant. A cross-sectional demographic and health survey of a random
sample of persons residing within the study area revealed that they were relatively homo-
geneous, predominately white, upper middle class, and with no remarkable prevalence of
health problems. Seven hundred and twenty-four people (246 families) volunteered to
record self-reported illnesses at biweekly intervals. Throat and stool specimens were
collected from a selected subsample of 161 persons providing a total of 1,298 specimens
analyzed for pathogenic bacteria and viruses. Three hundred and eighteen persons submit-
ted paired blood samples at the beginning and end of the study period to determine
prevalence and incidence of infections to five-coxsackie- and four-echovirus types. No
remarkable correlations were found between the exposure indices and rate of self-re-
ported illnesses or of bacterial or viral infection rates determined by laboratory analysis.
However, the plant was identified as a source of viable particles and total coliforms. The
overall conclusion that this activated-sludge treatment plant had no obvious adverse health
effect on residents potentially exposed to aerosol emissions must be tempered by the very
small number of people who were exposed to the highest pollution levels. This plant was
not a source of high concentrations of viable particles, gases, or metals, and the plant
levels of the aerosolized pollutants were much lower than those reported by other investi-
gators for similar plants.
Objectives of Study
This study was designed to determine whether or not the health of
persons exposed to aerosols emitted by a sewage treatment plant is
significantly different from that of persons living in less exposed areas
around the plant site. Field and laboratory studies to evaluate the envi-
ronmental and health status include:
• assessment of microorganisms and metal and gaseous constituents in
sewage with emphasis on those components considered to be hazard-
ous to human health
• assessment of the quality, quantity, and distribution of viable parti-
cles, nonviable particles, and gases in the air originating from the
sewage treatment plant and in the community
• assessment of the health, particularly with reference to infectious
diseases, of persons living in areas exposed to different concentra-
tions of viable and nonviable pollutants originating from the plant
-------
R. Northrop, et al 181
• interrelating the above data to determine the potential and actual
health hazard of exposure to sewage aerosols.
Scope of Work
In an attempt to determine whether or not the sewage treatment plant
was hazardous to the health of the community exposed to the plant
aerosols, several measurements of health were made.
First, a retrospective questionnaire survey of the types of diseases,
particularly of infectious character, was conducted on these diseases
that had occurred in the previous 12 months.
Second, a Health Watch, which was a prospective study of self-re-
ported illnesses by the sample population as well as microbiological
studies of throat and fecal specimen cultures, was conducted. Biweekly
diaries of self-reported infectious-like diseases and biweekly throat and/
or fecal specimens of members of selected households were collected by
field staff for 8 months. Also, two blood samples were collected from
this study group, one at the onset of the study and the second 8 months
later. The serosurvey provided both prevalence data of certain types of
infectious diseases encountered in the past and incidence of those en-
countered during the study period.
The analysis and interpretation of the health information collected
was based on the biometric and epidemiological concept of a dose-
response relationship; i.e., persons living in areas more highly exposed
to aerosols originating at the plant site may have different frequencies or
types of health problems than persons living in low exposure areas.
Accordingly, a separate control population group was not needed. Con-
ceptually, if the sewage treatment plant was the source of infectious
agents, trace metals, gases, or other hazardous materials, then the level
of exposure may be directly related to the number of infections and/or
diseases occurring in the exposed population.
Sewage and air monitoring programs were conducted to characterize
the type and extent of exposure of populations living within the study
area to pollutants emitted by the plant. The air pollutants monitored
included three general categories: viable particles, nonviable particles,
and gases. In addition, these substances were monitored in the sewage
at different stages of treatment.
The environmental measurement program characterized, through 8
months of monitoring, the exposure of individuals living in the vicinity
of the plant. This was accomplished by generating models of air concen-
trations within the study area for each pollutant measured. These con-
centrations were used to develop a personal exposure index for each
participant, and these indices were the basis for comparative health
analysis. In addition, through use of these measurements, an attempt
was made to relate the dispersion of pollutants to appropriate meterolog-
ical parameters and to a plant operation data model. This model would
attempt to predict air concentrations of each pollutant at various dis-
tances from the plant based on such factors as wastewater aeration rate,
wind speed and direction, concentration of pollutant in wastewater, and
solar radiation.
All health data obtained from the questionnaire, the Health Watch,
and the corresponding laboratory results were recorded into a personal
-------
182 Wastewater Aerosols and Disease/Population Studies
health file for each person interviewed and/or participant in the study.
These personal health files were referenced according to an individual
and household identification number. Incidence rates of various illness
categories were obtained for each person and/or household. A pollution
exposure index was available for each person or household. From these
data sets, a dose-response relationship between different levels of expo-
sure to sewage plant emissions and illness and infection rates was
investigated.
Standard techniques such as regression and analysis of variance were
used to relate the health and environmental data.
Description of Plant
The sewage treatment plant, referred to as the North Side Sewage
Treatment Works (NSSTW), used in this study is located in Skokie,
Illinois.
The NSSTW is an activated sludge plant employing diffused aeration
with a little tapered aeration. Chlorination occurs after the final settling
process. No sludge processing occurs at the plant. The maximum capac-
ity of the plant is 1.51 x 109 1 of raw sewage/day. During the study
period (April to November 1977) the plant had an average daily flow rate
of 1.1 x 1091 of sewage and a median air rate of 4.6 x 106 m3/day. The
estimated surface area of sewage in the aeration tanks is about 55,000 m2
in settling tanks, concentration tanks, etc., exposed to the atmosphere.
The total retention volume of one battery of aeration tanks is 7.45 x 104
m3. The tank levels were maintained at approximately 4.6 m. Residence
time of sewage in the aeration tanks is generally 51/* hours.
Description of Study Area
The area within a 1.6 km radius of the treatment plant as shown in
Figure 1 was designated as the study area. Previous studies suggested
that the dispersion of viable particles does not exceed 0.8 km from a
source. Therefore, the 1.6 km radius study area permitted analysis of
exposed and unexposed populations. As can be seen in Figure 1, the
plant is located in a small industrial area which occupies most of the land
within the first 0.4 km (1/4-mile) radius of the plant. The major residential
section begins at the 0.4 km radius line anq1 extends uniformly through
the 1.6 km radius area. The population of the study area was estimated
to be 15,850 persons, or 5,600 households, based on the 1970 census.
HEALTH ASSESSMENT PROGRAM
Methods
Sampling
In order to obtain a sample of households that would be distributed
throughout the study area, three concentric sampling zones were desig-
nated around the sewage treatment plant as shown in Figure 2.
Since the number of residences in the first 0.8 km radius was small
(394) compared to the next two 0.4 km radius areas (1,308 and 3,630,
respectively), a random sample of the entire area would have provided
many more households in the outer 0.8 km area. Therefore, a random
sample was chosen for each zone in order to obtain a more uniform
-------
R. Northrop, et al
183
CHICAGO
« 1> • 12
Figure 1. Map of Study Area
Rgure 2. Map of Sampling Zones
-------
184 Wastewater Aerosols and Disease/Population Studies
geographic distribution of households throughout the study area. It is
emphasized that these zones were established for sampling purposes
only. Final data analyses were based on actual viable and nonviable
pollution exposure levels, and not geographic distances.
The sample design was a disproportionate stratified sample with the
three sampling zones forming the strata. Since an equal number of
households was required per zone, the sample size for each zone was
determined by the number of households in the smallest zone, sampling
zone 1. Only 394 households were present in sampling zone 1; thus,
nearly every family in sampling zone 1 was included in the sample and
an equal number of households was then selected in sampling zones 2
and 3.
Health Questionnaire
The survey instrument was a 34-page booklet containing 29 questions
and required approximately 45 minutes of interview time for an average
family to complete. Questions were asked by trained interviewers re-
garding demographic, historical health, occupational, and living condi-
tions for each member of the family. Usually each member responded
for himself. Certain families fulfilling the requirements to be a Health
Watch participant were recruited at the time of the health questionnaire
interview into the Health Watch.
Health Watch
In order to obtain ongoing, prospective information about health in
the study population, a subsample of the persons interviewed in the
health questionnaire survey was solicited into the Health Watch. Partici-
pants, as family units, were asked first to maintain a health diary to self-
report any and all illnesses they encountered for an 8-month period.
Secondly, they were requested to provide blood samples at the begin-
ning and again at the end of the 8-month period. Finally, certain families
were asked to provide clinical specimens for biweekly microbiological
surveillance as follows:
• When children 12 years or younger were present, then biweekly throat
and stool specimens were requested from the children. In addition,
the next older person over 12 years of age in those households was
requested to provide only a stool specimen biweekly. All persons over
6 years of age were asked to give two blood samples as well as to
maintain the diary.
• If all persons in the household were over 12 years of age, two blood
samples and diary maintenance were requested from each household
member.
The study design and sampling for the Health Watch were extensions
of the design and sampling methods described for the health question-
naire survey. Specifically, 290 households were needed to participate in
the Health Watch in order to have sufficient health-related data for
analysis. Each diary provided directions and space for self-reporting of
any illnesses that occurred in a 2-week period. The information re-
quested included:
-------
R. Northrop, et al 185
• date illness began
• person in family experiencing illness
• nature of illness and/or symptoms
• number of days ill with no restriction of activity
• number of days of restricted activity
• medications taken
• physician consulted
• hospitalization
• date of recovery.
Results and Discussion
Health Questionnaire Survey
Demographics of Survey Population. The 807 households (2,378 indi-
viduals) participating in the health questionnaire survey were distrib-
uted throughout the 1.6 km radius study area as shown in Table 1. It
can be seen that the households were nearly equally distributed with
regard to distance from the plant. Since the main health variable to be
considered was the incidence of infectious diseases relative to air qual-
ity, it was important to determine that the study population in each area
was composed of persons with similar demographic characteristics.
Age, sex, race, socioeconomic status, and family size are known con-
founding variables in the incidence of many infectious diseases.
Overall, the families participating in the health questionnaire survey,
regardless of their residence location in the study area, were character-
ized as white (93.6%), middle class ($22,317 median income), white
collar workers (76.8%), with an average family size of 2.9 people, and
were a stable population having lived in the study area for more than a
decade (mean = 11.7 years).
The analyses of the general characteristics of the subsets of the health
questionnaire survey population according to location of residence in
the study area have shown that there are minor significant differences in
these subsets. Age, race, family size, length of residence, and occupa-
tion were significantly different; whereas sex, income, and home air
conditioning were not. The differences, although minor, were incorpo-
rated into later interpretation of the health data.
Prevalence of Chronic Conditions in the Survey Population. The con-
cern about chronic conditions in the study population was twofold: first,
a number of chronic conditons have been associated with metals, gases,
Table 1. Distribution of Health Questionnaire Survey Population by Dis-
tance of Residence from Plant
Distance of
from plant (km)
0.0-0.8
0.8-1.2
1.2-1.6
No.
269
267
271
Households
%
33.3
33.1
33.6
No
847
791
740
Individuals
%
35.6
332
31 1
Total 807 100.0 2,378 100.0
-------
186 Wastewater Aerosols and Disease/Population Studies
or infectious agents that are present in the environment; and second,
individuals with chronic illness may be at a higher risk to acute infec-
tious diseases than those without such conditions. Table 2 lists the
chronic conditions specifically inquired about in the questionnaire and
the corresponding number of conditions per 100 persons in the residen-
tial areas. For the 2,378 respondents, 2,006 chronic conditions were
reported. The rates for respiratory conditions (26.6/100), cardiovascular
(20.4/100), gastrointestinal conditions (21.1/100), and other chronic con-
ditions (28.0/100) combined for an overall prevalence of 96.6 conditions/
100 persons interviewed. It was not possible to assess these rates be-
cause they represent self-reported conditions experienced in the lifetime
of the survey participants; comparable data have not been reported in
the literature.
No association was found (one-way analysis of variance, p> 0.05)
between the prevalence of chronic respiratory, chronic cardiovascular,
or all chronic conditions and distance of residence from the plant. How-
ever, a significant difference (one-way analysis of variance, p< 0.01,
followed by Duncan multiple range test) was observed between the
prevalence of chronic gastrointestinal conditions in the 0.0 to 0.8 km and
1.2 to 1.6 km residence groups; persons living farthest from the plant
had more gastrointestinal conditions than those living nearest the plant
site. The 1.2 to 1.6 km residence area had a higher percentage of persons
over 59 years old (26.1%) than the other two residence areas (14.3 and
19.7%) which may be a possible explanation for the above observation.
Table 2. Average Number of Reported Chronic Conditions/100 Per-
sons by Distance from Plant
Type of chronic condition Distance of residence from plant (km)
0.0-0 8 0.8-1 2 12-16 Total
Respiratory conditions''
Cardiovascular conditions"
Gastrointestinal conditions"
Other cancers
Arthritis
Infectious hepatitis
Diabetes
Anemia
Other chronic conditions
25.3
18.4
17.0
2.1
9.9
1.0
4.4
3.7
6.6
292
21.2
21 6
26
9.6
1 2
5.1
2.7
6.1
253
21 9
25.3"
36
11 5
1 4
32
41
5.9
26.6
20.4
21 1
2.7
10.3
1.2
4.2
3.4
6.2
Total 76.5 87.2 90.3 84.3
"Includes cancers
"•Significantry greater (one-way analysis of variance test, p < 0.05, in conjunction with Duncan multiple
range test) than that for 0.0-0.8 km residence group
Acute Illnesses Reported for Year Prior to Interview. Table 3 contains
a summary of the rate of acute illnesses/1,000 person-days for the year
prior to the onset of the study. The average rate of 1.64 illnesses/1,000
person-days was likely an underreporting since recall of short-term ill-
ness is probably unreliable, particularly if one family member responds
for other family members. This was borne out by several surveys over
the past few decades where the average experience was 2.5 to 4.4 ill-
nesses/1,000 person-days.
-------
R. Northrop, et al 187
Table 3. Average Number of Acute Illnesses/1,000 Person-days Dur-
ing Months Prior to Survey by Distance from Plant
Distance of
residence
from plant (km)
0.0-0.8
0.8-1.2
1.2-1 6
Type of acute illness
Respiratory
096
0.90
0.93
Gastrointestinal
0.30
022
038"
Eye/ear
0.19
0.11
014
Skin
0.25
019
0.27
Total
1.70
1 48
1 75
Total 093 0.30 0.16 025 1.64
"Significantly greater (one-way analysis of variance test, p < 0 05, in conjunction with Duncan multiple
range test) than that for 0.0-0.8 km residence group
Health Watch
Demographic Comparisons. Of the 807 households that participated in
the health questionnaire survey, 290 households (869 individuals) be-
came participants in the Health Watch to determine the incidence of
health problems prospectively over an 8-month period. The remaining
517 households (1,509 individuals) were designated as "questionnaire-
only" households. A demographic comparison (age, sex, race, family
size, and income) of these two subsamples was made to determine
whether the Health Watch participants adequately represented the en-
tire questionnaire population (n = 807 households), and the demo-
graphic distributions were found to be similar for the two subsamples.
During recruitment of households for the Health Watch, 61 house-
holds (162 individuals) refused to participate in the study. In order to
maintain the original sample size, the refusals were replaced with 54
alternate volunteer households (163 individuals). The Health Watch re-
fusals were demographically similar to their replacements.
Of the 290 households that participated in the Health Watch, 44 (15%)
dropped out during the course of the study (see Table 4). The 246 fami-
lies completing the Health Watch included 724 individuals; the 44 drop-
out families consisted of 145 individuals. Health Watch families drop-
ping out of the study were demographically similar to those completing
Table 4. Summary of Health Watch Participation and Completion": April
3-November26,1977
Distance of Number entering Number completing
residence from Health Watch Health Watch
plant (km)
Families Persons Families Persons
No % No. %
0.0-0.8
0.8-1.2
1.2-1.6
95
93
102
306
289
274
82
80
84
863
86.0
82.3
252
245
227
82.4
848
82.8
Total 290 869 246 84.8 724 833
"Based on diary participation.
-------
188
Wastewater Aerosols and Disease/Population Studies
the study. The demographic characteristics of the drop-outs and those
who completed the Health Watch are presented in Table 5.
Table 5. Demographic Profile of Health Watch Participants
Individuals
Age (years)
<6
6-18
19-59
>59
Total
Mean age = 39 7
Sex
Male
Female
No
32
162
473
202
869
No
411
458
%
37
18.6
545
233
%
473
23.3
Households
Family size
1
2
3
4
5
>6
Mean family size =
Income (x $1,000)
<10
10-14.9
15-249
^25
No answer
No
28
107
56
62
21
16
3.00
No
24
29
79
104
54
%
97
36.9
193
21 4
7.2
5.5
%
83
10.0
272
35.9
18.6
Median income = $23,200
Race
White
Other
No.
270
20
93.1
69
Health Diary Data. The distribution of the types and number of ill-
nesses reported and of the person-days observed during the 17 biweekly
periods of the study are shown in Table 6.
Table 6. Distribution of Reported Illnesses and Exposure Days by Data-
Collection Period
Beginning date
of 2-week data-
collection
period, 1977
April 3
April 17
May 1
May 15
May 29
June 12
June 26
July 10
July 24
August?
August 21
September 4
September 18
October 2
October 16
October 30
November 13
Total
(%)
No of illnesses
No of
person-days
of exposure"
3,486
5,794
10,062
10,504
10,231
9,858
9,496
9,398
9,162
9,331
9,423
9,604
9,465
9,425
9,166
9,262
9,359
153,026
Respir-
atory
20
40
73
65
49
54
25
37
56
64
61
69
82
108
65
59
91
1,018
(648)
Gastro-
intes-
tinal
9
9
15
21
14
19
10
19
18
11
16
21
14
17
25
16
21
275
(175)
Eye-ear
2
6
13
14
8
5
5
10
15
6
9
4
8
7
1
2
3
118
(75)
Skin
3
5
2
3
6
2
2
3
3
7
2
6
5
6
4
4
3
66
(4.2)
All
other''
5
7
7
5
10
4
3
9
3
9
6
4
5
6
5
2
5
95
(6.0)
Total
39
67
110
106
87
84
45
78
95
97
94
104
114
144
100
83
123
1,572
(100.0)
"Total number of days all persons participating in Health Watch were present in the study area dunng the
data-collection period
'Includes other acute infections, exacerbations of chronic conditions and new chronic conditions
-------
R. Northrop, et al 189
From these data, illness rates were expressed as follows:
"umber of illnesses x 1,000 = illness rate/1,000
number of person-days observed person-days
(Equation 1)
Thus, the total number of 1,572 illnesses reported during 153,026 per-
son-days observed equaled a rate of 10.27 illnesses per 1,000 person-
days as shown in Table 7. In general, these illness rates were consistent
with the Health Interview Survey (HIS) for 1975 to 1976 reported by the
National Center for Health Statistics (NCHS). The rates shown in Table
7 were nearly 1.7 times higher than those reported by NCHS. This study
and the HIS were not conducted in the same way and cannot be directly
compared. It is possible that the Health Watch participants were more
health conscious than the general population because there was some
degree of self-selection on the part of the Health Watch families, even
though they were demographically similar to a random sample of the
study area population. The outcome of a self-selected, health-conscious
group would tend to result in overreporting of illness. It is also empha-
sized that illness is defined here as any deviation from an expected
healthy state, whereas NCHS defined illness as a condition limiting
normal activity; consequently, the Health Watch was a more sensitive
measure of illness but not as specific as the HIS.
Table 7. Illness Rates" by Data-Collection Period
Beginning date
of 2-week
data-collection
period, 1977
April 3
April 17
May1
May 15
May 29
June 12
June 26
July 10
July 24
August?
August 21
September 4
September 18
October 2
October 16
October 30
November 13
Total
All
illnesses''
11.42
11.58
10.93
10.28
8.50
852
474
8.30
10.37
10.40
998
10.83
1204
15.28
10.91
8.96
1314
10.28
Respir-
atory
5.85
6.90
7.26
6.19
4.79
5.48
2.64
3.94
6.11
6.86
6.47
719
8.66
11 46
709
6.37
972
666
Gastro-
intes-
tinal
2.64
1 55
1 49
2.00
1.36
193
1 05
2.02
97
.18
70
2.19
.48
.80
2.73
1.73
2.24
1.80
Eye/ear
0.59
1.04
1 29
1 33
0.78
0.51
0.53
1.06
1.64
0.64
0.96
042
0.85
0.75
0.11
0.22
0.32
0.77
Skin
0.88
0.86
0.20
0.29
0.59
0.20
0.21
0.32
033
0.75
021
0.63
0.53
0.64
0.44
043
0.32
0.43
Other
acute E
infec-
tions
0.59
0.35
0.10
010
039
010
0.11
0.32
0.11
0.21
011
C
0.11
<
<
I
011
0.14
jocerbatior
of chronic
condition
0.88
0.86
060
0.19
0.39
0.30
0.11
0.43
0.22
054
042
031
0.42
0.32
0.44
0.22
043
0.39
) New
chronic
condition
,-
<
<•
0.19
020
<
0.11
0.21
C
021
0.11
0.10
C
0.32
011
i
<
0.10
««nesses/1,OOOpersorwJayS = "Q. of .llnesses reported
no of person-days present
''See Table 6 for number of illnesses
cNo cases reported
-------
190
Wastewater Aerosols and Disease/Population Studies
CD
o
CL
x
CD CD
en „_
<" O
CD
c c/)
n >-
- co
a,'?
QC en
"5 CD
£ O
— o
o
CD
a
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Respiratory
Illnesses
01 2 34 5 6 7 8 9 10 11 12 13 1415 16 17
April May June July Aug Sept Oct. Nov.
Data-Collection Period
Figure 3. Seasonally of Illness Rates
Respiratory illness rates were lower in the spring and summer than in
the fall, reaching peak incidence in early October (Figure 3). This rela-
tively high occurrence appeared shortly after the beginning of school,
coinciding with the increased exposure of children within the confine-
ment of school rooms. The overall pattern of incidence of respiratory
illnesses was in consonance with current knowledge of seasonally of
respiratory illness. Seasonal variation was not observed for gastrointes-
tinal illnesses, eye/ear illnesses, skin disease, other acute problems,
exacerbation of chronic conditions, or new chronic conditions. Al-
though seasonal variations for these illnesses was not expected, the
rates for these illnesses were low (only gastrointestinal illness rates
consistently exceeded one/1,000 person-days) and temporal variations
would have been an unlikely observation.
Illness rates were examined with respect to five demographic varia-
bles (age, sex, race, family size, and length of residence in the study
area) in order to determine which of these characteristics might be asso-
ciated with risk of illness.
Considering age, rates of all reported illnesses (Table 8) were highest
in children under 14 years old, and the rate tended to decrease as age
-------
R. Northrop, et al 191
Table 8. Illness Rates" By Age''
Age groups (years) Total
Typeofillness 0-2 3-5 6-13 14-18 19-59 >59 (allages)
Acute
Respiratory
Gastrointestinal
Eye/ear
Skin
Other acute infections
Chronic
Exacerbation of
chronic condition
New chronic condition
Total (all illnesses)
No. of people m age category
13.99'
350
233
d
j
d
d
1983
9
16.09
3.97
088
0.44
0.22
d
022
21 82'
23
1063
238
0.89
059
015
d
d
1465
76
763
250
066
046
013
d
013
11.50
86
602
1 71
0.59
036
010
0.24
007
909
473
461
1 10
1 13
055
023
1 13
017
8.91
202
666
1 80
077
043
0 14
039
010
1027
869
-Illness/1,000 person-days = "° of i"nesses rePorted * 1,000
no of person-days present
''Age at beginning of Health Watch
'See Table 6 for number of illnesses
JNo cases reported in this category
^Significantly different (p < 0 01) from total illness rates tor age groups 14-18, 19-59, and > 59 years
increased. The total illness rate for 3- to 5-year-old children was signifi-
cantly different (one-way analysis of variance, p < 0.01, in conjunction
with Duncan multiple range test) from the total illness rate for the 14-to
18-, 19- to 59-, and over 59-year-old groups. About two-thirds (68.0%) of
all illnesses in all age groups were of respiratory nature. Gastrointestinal
conditions were more common in the age groups 0 through 18 years than
in older age groups. The other illness types were less age-related and
relatively infrequent in occurrence.
Regarding the sex variable as seen in Table 9, the incidence rate of all
illnesses reported for females (11.8/1,000 person-days) was significantly
Table 9. Illness Rates" By Sex
Sex Total
Typeofillness Male Female (both sexes)
Acute
Respiratory 5.67*' 755 666
Gastrointestinal 1 48 2 09 1 80
Eye/ear 0 56 0 95 0 77
Skm 0.41 045 043
Other acute infections 004 023 014
Chronic
Exacerbation of chronic
condition 036 041 039
New chronic condition 008 011 010
Total (all illnesses) 861 118O 1028
No. of people in
sex category 411 458 869
-Hness/1,OOOpersorMteys = no of Mnesses reported x ^
no of person-days present
''See Table 6 for number of illnesses
• Significantty (p < 0 01) greater than total illness rate for males
-------
192 Wastewater Aerosols and Disease/Population Studies
greater (t-test, p < 0.01) than that reported for males (8.6/1,000 person-
days). A similar sex differential in illness was also observed by NCHS.
It has also been reported that females seek more health care, excluding
visits pertaining to childbearing, than males.
Illness rates by race were not examined since 92.7% of the families in
the study were white. Comparisons of illness rates according to ethnic-
ity were not undertaken.
It has been generally found that the incidence of infectious diseases is
proportional to family size. There was no apparent difference in illness
rates in families ranging in size from one through nine members (Table
10) in this study. These illness rates, however, included numerous non-
infectious, acute conditions as well as chronic conditions, which may
mask the effect of family size on communicable illnesses.
It was also hypothesized that persons living in the study area for a
short time might experience more illness because they are being exposed
for the first time to sewage aerosols in the environment, whereas per-
sons who have been exposed for longer periods of time were infected
and are subsequently immune to these environmental agents. Not all
reported illnesses are infectious in nature, and, as will be shown later,
only about one of six reported illnesses in children can be associated
with an infectious agent. Although no association between length of
residence and illness rate is readily apparent (Table 11), the inverse
relationship of illness rate and length of residence may be real. Future
studies should document this relationship, with laboratory data to con-
firm the incidence of infectious disease.
Table 10. Illness
Rates" By Family Size
Family size (no. of members in household)
Type of illness
Acute
Respiratory
Gastrointestinal
Eye/ear
Skin
Other acute
infections
Chronic
Exacerbation of
chronic condition
New chronic
condition
Total (all ill-
nesses)
No of families
in size category
1
604''
1.46
1.04
<
0.42
2.92
r
11.87
28
2
649
1.46
0.93
0.58
017
082
017
10.61
107
3
4.98
1.59
094
0.29
011
0.14
'
8.04
56
4
772
284
0.65
0.60
016
0.22
013
1233
62
5
772
1.09
0.52
0.16
0.10
c
0.10
9.60
21
6
5.54
1 51
0.76
042
1
0.08
0.08
839
10
7 8
6.85 4.94
0.36 0.62
< 0.31
< 0.62
' 031
c <
< '
7.21 6.80
3 2
Total
(all
9 sizes)
10.28 6.66
0.94 1 80
1.87 0.77
' 0.43
' 0.14
< 039
<• 010
13.08 1028
1 290
-..Iness/I.OOOperso.-o-ays -
feSee Table 6 for number of illnesses
'No cases reported in this category
-------
R. Northrop, et al 193
Table 11. Illness Rates" By Length of Residence
Length of residence (years)
Type of illness* <1 1-5 6-10 11-20 21-30 31-40 >40 Total
Acute
Respiratory
Gastrointestinal
Eye/ear
Skin
Other acute infections
Chronic
Exacerbation of
chronic condition
New chronic condition
Total (all illnesses)
No. of persons in
residence category
"HlnaftRpR/l noft nprsnn-da
777
1.80
057
1 04
<
0.10
<
11 27
56
ws- no-
8.11
2.61
1 07
0.70
0.09
0.64
009
1330
206
657
1.14
0.57
0.18
0.07
004
014
872
159
of illnesses reported
5.40
1 80
0.54
0.48
0.16
030
0.10
879
289
x 1
6.91
1 56
1.16
0.25
0.69
0.11
10.68
145
.000
4 47 4.98
1.66
3.32
0.56
0.56
'
5.59 9.97
11 2
665
1.80
0.77
0.43
014
039
010
1027
868"
no of person-days present
bSee Table 6 for number of illnesses
rNo cases reported in this category
"Length of residence unknown for one person
Microbiological Analyses of Specimens Collected. Eighty Health
Watch participants provided stool specimens representing 44.0% of the
expected number of providers. They submitted 541 stool specimens
(17.7% of the total number of stool specimens expected), indicating that
not even the.80 participants provided all the specimens expected. Labo-
ratory testing for bacteria included a search for any unusual isolates.
The tissue culture systems used in the laboratory for virus isolation were
most sensitive for recovering adeno-, myxo- and enteroviruses.
As shown in Table 12, two Salmonella spp. were recovered from the
80 persons tested for 8 months. One isolate was from a 5-year-old girl;
the other was from an adult female. Neither had reported clinical illness.
This was equivalent to an incidence rate of 3.75 cases/100 person-years,
which, compared to 12 cases/100,000 person-years reported in the Un-
ited States by the Center for Disease Control, was more than expected.
The rate of permanent, asymptomatic carriers of Salmonella in the Un-
ited States is believed to be 0.2 to 5.0/100 of the normal population.
Whether these two cases were carriers or not was not established.
Viruses isolated from the 541 stool specimens were members of three
enterovirus groups. No adenoviruses or other cytopathic agents were
recovered that could have been detected in the cell culture systems used
(Table 12). Seven polioviruses were recovered, and all of these were
from young children with a recent history of poliovirus immunization.
One Coxsackievirus B3 was isolated from a child. The remaining 13
virus isolates were echovirus types 3, 6, 12, 22, and 25. The incidence of
echovirus infections was highest in the 3- through 6-year-old groups but
occurred in the other age groups to 13 years old. Only one echovirus
infection occurred (Echovirus 12) in an adult. These coxsachievirus and
echovirus types recovered during this study group are commonly asso-
ciated with respiratory-enteric illness or with diarrheal disease and often
are asymptomatic infections.
-------
194 Wastewater Aerosols and Disease/Population Studies
Table 12. Organisms Isolated from Stool Specimens0 by Age of Partici-
pants'1
Age groups (years)
Isolates 0-23-45-6 7-12 13-18 19-59 Total
Stool specimens
No. of people asked
to give specimens
No. people who gave
at least one
No. specimens
obtained
Bacterial isolates'
Salmonella
Viral isolates1
Poltol
Polto 3
Coxsackie B3
Echo 3
Echo 6
Echo 12
Echo 22
Echo 25
Total viral
Total stool' isolates
8
6
43
0
3
3
0
0
0
0
1
0
7
7
14
10
73
0
0
0
0
0
1
1
0
1
3
3
20
10
72
1
0
0
1
1
1
1
1
1
6
7
69
23
154
0
0
1
0
3
0
0
0
0
4
4
24
8
46
0
0
0
0
0
0
0
0
0
0
0
45
23
153
1
0
0
0
0
0
1
0
0
1
2
180
80
541
2
3
4
1
4
2
3
2
2
21
23
"Specimens requested on a biweekly basis of chikten 12 years of age and under and of one adult in each
family thereof; specimens obtained from May, 1977 through November, 1977
"Age at beginning of Health Watch
'For cases of multiple consecutive isolations of a single type of organisms for one person, only the first
isolation was tabulated
An interpretation of the incidence of these laboratory-confirmed in-
fections based on examination of stool specimens is, at best, crude. The
incidence of Salmonella spp. in stool specimens has been considered
above, and the poliovirus isolates were vaccine-related. The recovery of
14 coxsackievirus and echoviruses from 80 persons submitting 541 spec-
imens over an 8-month period yielded a crude rate of 17.5 enterovirus
isolations/100 persons/8-months.
Studies have been conducted showing that the percentage of healthy
children shedding enteroviruses ranged from 4.6 to 14.9%. The Health
Watch study period covered those seasons of the year in which enterovi-
rus infection rates were expected to be highest, accounting for the fact
that the rate found here was in the upper limits of the expected rate.
Of the 111 children 12 years old and under in families recruited into
the Health Watch, 81 submitted 757 throat specimens for an average of
9.3 specimens/child during the study (Table 13). Theoretically, 17 speci-
mens could have been collected from each participating child; actually,
nearly 55% of the expected number of throat specimens were collected.
Compared with the 17.7% of expected stool specimens collected, it is
apparent that providing throat swabs was more acceptable than submit-
ting fecal samples. It was also noted that the age distribution of the 81
children providing throat specimens was similar to that of the original
111 children in the recruited families.
-------
R. Northrop, et al
195
A total of 177 bacterial and viral isolates was made from the 757 throat
specimens received. On the average, 4.5 bacterial isolates were recov-
ered from each child in the 0-to 2-year age group, 2.7/child in the 3- to
4-year age group, and 1.8 in the 5- to 12-year age group. A similar
decrease in isolation with increasing age was also possible for viral
infections, but the numbers were too small to be significant.
Of the 20 different bacterial types isolated, Klebsiella pneumoniae,
Staphylococcus aureus, and Enterobacter spp. were the most frequently
recovered in the 0- to 2- and 3- to 4-year age groups. S. aureus was the
Table 13. Organisms Isolated from Throat Specimens" by Age of Par-
ticipants''
Isolates
Age groups (years)
0-2
3-4
5-12
Total
No Rate' No. Rate No. Rate No. Rate
Throat specimens
No. people asked
to give specimens
No. people who gave at
least one
No. specimens received
Bacterial isolates''
Staphylococcus aureus
Beta-streptococcus, Group A
Beta-Streptococcus,
not A or D
Salmonella enteritidis
(Newport)
Klebsiella ozaenae
Klebsiella pneumoniae
Escherichia coli
Enterobacter aerogenes
Enterobacter aggtomerans
Enterobacter cloacae
Enterobacter hafniae
Serratia liquefaciens
Serratia marcescens
Serratia rubidaea
Aeromonas hydrophilia
Citrobacter diversus
Citrobacter freundii
Pseudomonas spp
CDC, Group IV C-2
CDC, Group V, E-1
Total bacterial
Viral isolates-'
Adenovirus 2
Echovirus 6
Total viral
Total throat isolates
8
6
48
6
0
0
0
2
9
2
0
1
4
0
0
0
0
0
0
2
0
0
1
27
0
0
0
27
1000
00
0.0
0.0
33.3
150.0
33.3
0.0
16.7
66.7
00
0.0
0.0
0.0
00
0.0
333
0.0
0.0
16.7
14
11
108
8
1
2
1
0
2
1
1
2
6
0
1
0
0
2
1
0
1
0
0
29
0
2
2
31
72.7
91
18.2
91
0.0
18.2
9.1
9 1
18.2
54.5
00
9.1
0.0
0.0
18.2
9.1
00
9 1
0.0
00
89
64
601
56
14
17
0
0
4
5
0
6
5
1
3
1
1
1
0
0
2
1
0
117
1
1
2
119
87.4
224
26.5
00
0.0
6.2
7.8
00
94
7.8
1.6
47
1 16
1.6
1.6
0.0
0.0
31
1 6
00
111
81
757
70
15
19
1
2
15
8
1
9
15
1
4
1
1
3
1
2
3
1
1
173
1
3
4
177
86.4
18.5
23.5
1.2
2.5
18.5
9.9
1 2
11 1
18.5
1 2
4.9
1 12
1.2
37
1.2
2.5
3.7
1 2
1.2
"Specimens requested on a biweekly basis from children 12 years of age and under; specimens
obtained from May, 1977 through December, 1977
<>Age at beginning of Hearth Watch
•Number of isolated/100 persons
dFor cases of multiple consecutive isolations of a single type of organism for one person, only the first
isolation was tabulated
-------
196 Waste water Aerosols and Disease/Population Studies
most frequent isolate in the 5- to 12-year-old group, followed by beta-
hemolytic streptococci. The number of different bacterial genera iso-
lated was the smallest in the youngest age group and more different
genera were recovered with increasing age.
Only four virus isolates were recovered: three Echovirus 6 were iso-
lated in the 3-to 12-year-olds, and one Adenovirus 2 in the 5-to 12-year-
old group. No viral isolates were made in children 2 years old or youn-
ger. Hemadsorption tests were done on all cell cultures inoculated with
these specimens and none were positive, suggesting that influenza, para-
influenza, measles, or mumps virus infections had not occurred in this
population.
In summary, 173 separate, nonnormal flora, bacterial isolates were
recovered from routine throat swab specimens of 81 children 1 through
12 years of age. In contrast, only two unusual bacteria isolates were
identified in stool specimens from persons 0 through 59 years of age.
Virus isolates were about three times more frequent from stools (ex-
cluding the polioviruses associated with immunization) than from throat
specimens. The recovery of more enterovirus from stool than from
throat specimens was expected because infections of the oropharynx
persist for only a few days whereas these infections continue in the
intestinal tract for a month or more (whether or not there is associated
clinical illness) increasing the chance of recovery from stool specimens
when biweekly specimens are obtained. The information derived from
this microbiological survey of throat and stool specimens did not allow a
statement of the significance of the findings because of the small number
of participants involved and of the small number of bacteria and viruses
recovered. The findings were of value for descriptive purposes for con-
sideration later when the air quality data were analyzed.
Serological Analyses. A total of 318 persons 6 years of age and older
gave paired blood samples of 837 persons requested to give two blood
samples, pre- and post-study. The sera of each paired blood sample
were tested for antibodies to 12 viral agents. These included Poliovi-
ruses 1 through 3; Coxsackieviruses Bl through B5, and Echoviruses 3,
6, 9 and 12 which: 1) are known to commonly populate sewage; 2) are
stable and could be emitted into sewage aerosols; and 3) are known to be
common pathogens for man which may cause either clinical or subclini-
cal illness. Enteric viruses have been associated with gastrointestinal,
respiratory, cutaneous and/or combined illness.
For the analysis of the serological data, it was necessary to calculate
the number of susceptibles for each virus under consideration, since any
one person could be immune to one virus and susceptible to another
virus. The following equations were used for Table 14:
no. susceptible + no. immune = total paired blood donors
(Equation 2)
no. susceptible = (no. of persons with initial liter < 10)
plus
(all other persons with fourfold rise)
(Equation 3)
The incidence (Table 14) of Coxsackievirus B4 infections was the high-
est observed, 17.97/100 persons, whereas the Bl rate was the lowest,
-------
R. Northrop, et al 197
Table 14. Incidence of Viral Infections Among Susceptible Blood
Donors
Virus
antigen
Coxsackie B1
Coxsackie B2
Coxsackie B3
Coxsackie B4
Coxsackie B5
Echo 3
Echo 6
Echo 9
Echo 12
No. of persons
immune"
48
137
140
190
98
119
140
94
94
No of persons
susceptible1'
270
181
178
128
220
199
178
224
224
No. of persons
seroconverting'
4
12
15
23
9
7
8
3
10
Incidence1' of
viral infections
1 48
6.63
8.43
17.97
4.09
3.52
4.49
1.34
446
«No. of persons with initial antibody titer > 10 minus no. of persons with fourfold rise whose initial titer
was > 10
''No of persons with initial antibody titer < 10 plus all other persons with fourfold rise
'All persons with fourfold rise in antibody titer
1.48/100 persons. The listing of the number of persons immune and
susceptible to the coxsackieviruses emphasises that the majority of per-
sons were susceptible to these agents, except for Coxsackievirus B4.
The infection rates for Echoviruses 3, 6, 9, and 12 were similar to each
other and were generally lower than those observed for the coxsackievi-
ruses. The number of susceptibles was similar to the number susceptible
to the coxsackieviruses.
The incidence of these viral infections was then examined by age
groups (Table 15). Infections by Coxsackievirus Bl and B2 were not
observed in the 6-through 18-year-old groups, but occurred in all other
age categories. The incidence of B3 infections was similar in all age
groups, whereas B4 infection rates increased remarkably with increas-
ing age to the maximum of over 30/100 persons over 59 years old.
Coxsackievirus B5 infections were relatively more frequent in children
and adults than in the over 59-year-old group.
Echovirus 3, 6, and 9 infection rates were similar in all age groups;
Echovirus 12 infections were not observed in the 6-through 18-year-old
group and the rate increased from about 4/100 in the 19-through 59-year-
old group to 10/100 in the over 59-year-old group. With only a few
exceptions, the number of susceptible persons in each age group ex-
ceeded the number immune. The incidence data presented here for these
few infectious diseases are of important descriptive nature, and they are
not intended for statistical interpretation since a hypothesis for these
data alone was not the purpose of this portion of the study. Biometric
analyses of these data will be applied when they are considered with the
environmental air quality data.
-------
Table 15. Incidence of Viral Infections Among Susceptible Blood Donors by Age
CO
00
Age groups (years)
6-18
Virus
antigen
Coxsackie B1
CoxsackieB2
Coxsackie 63
Coxsackie B4
Coxsackie B5
Echo 3
Echo 6
Echo 9
Echo 12
No. of
immune
persons"
5
10
12
15
16
15
14
7
1
No. Of
susceptible
persons*
35
30
28
25
24
25
25
23
39
No. of
persons
serocon-
vertingf
0
0
2
1
1
2
1
1
0
Incidence
of viral
infection''
0.00
000
7 14
4.00
4 17
8.00
4.00
3.03
0.00
No of
immune
persons
32
82
89
114
65
55
77
59
58
19-59
No. Of
susceptible
persons
160
110
103
78
127
137
115
133
134
No. Of
persons
serocon-
verting
3
9
9
14
7
4
5
1
5
Incidence
of viral
infection
1.87
818
874
1795
5.51
292
4.35
075
3.73
No Of
immune
persons
11
45
39
60
17
49
48
28
35
>59
No. Of
susceptible
persons
75
41
47
26
69
37
38
58
51
No of
persons
serocon-
verting
1
3
4
8
1
1
2
1
5
Incidence
of viral
infection
1 33
732
8.51
30.77
1.45
2.70
5.26
1 72
980
"No. of persons with initial antibody titer >. 10 minus no. of persons with fourfold rise whose initial titer was > 10
''No. of persons with initial antibody titer < 10 plus all other persons with fourfold rise
1 All persons with fourfold rise in antibody liter
"Incidence of viral infections = no. of persons seroconvertmg x 1QO
no. of persons susceptible
-------
R. Northrop, et al 199
ENVIRONMENTAL MONITORING PROGRAM
Methods
Measurements of air pollutants were taken on a regular basis at the
plant and in the surrounding area out to 1.6 km. The air pollutants
included total aerobic bacteria-containing particles, hereafter referred to
as total viable particles (TVP), total suspended particulate matter (TSP),
NO2( SO2, C12, NH3 and H2S. TSP filters were also analyzed for ni-
trates (NO3~) and sulfates (SO4=), As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Sb,
Se, Sn and V. Total coliform (TCP) were collected and analyzed over
the final 2V2 months of the project. Grab samples of sewage entering the
aeration tanks, taken concurrently with the air samples, were analyzed
for the same pollutants. Sampling methods and a description of the
sampling periods for viable and nonviable pollutants are given in Tables
16 and 17.
A meteorological station was installed on the plant site for continuous
monitoring of wind speed and direction, temperature, relative humidity,
ultraviolet and total radiation, and rainfall. This equipment provided
integrated wind direction data for use in the selection of the monitoring
sites.
The environmental monitoring data were used to develop a personal
exposure index for the residents of the study area. This was accom-
plished by using maps of concentration isopleths generated from the air
pollution data. The personal exposure index takes into account meteoro-
logical factors as well as the actual measured pollution levels.
Selection of Monitoring Sites
The sites for viable particle sampling were selected to maximize the
probability of collecting organisms of plant origin. Three sites in a line at
various distances downwind from the aeration tanks and one upwind
were chosen for this purpose. Based on dispersion distances observed in
previous studies of airborne organism distributions and the geographic
distribution of residences in the study area, 16 community sampling sites
were selected in two concentric circles of 0.8 km and 1.6 km radius from
the plant, and four on-plant sites were chosen along the north, east,
south, and west edges of the aeration tank batteries. The 16 community
viable sampling sites were chosen to closely follow the eight major wind
direction patterns (N—S, E~~W, NW—SE, and SW—NE). At each
sampling site, a location for the mobile monitoring unit was chosen away
from all tall buildings or other obstructions. For on-plant site selection,
wind direction was categorized into one of four 90° sectors: NE to SE,
SE to SW, SW to NW, and NW to NE.
The monitoring sites selected for the nonviable air measurements
were based on different criteria than for the viable protocol. Each site
was a permanent facility. The site at the plant was located near the
aeration tanks. Two community sites were selected in high-density resi-
dential areas 1.6 km from the aeration tanks. Two other sites were
located northeast of the plant approximately 0.8 and 1.6 km from the
tanks. These selections were based on 1975 prevailing wind data for the
north suburban area. The nonviable monitoring sites required access to
a 110-volt electrical supply. It was also necessary to locate the equip-
-------
Table 16. Sampling Methods: Viable Constituents
Constituent
Total aerobic
bacteria containing
particles (TVP)
Total coliform-
containing particles
(TCP)
Fecal coliform-
contaming particles
Sampler
Andersen - 2000
Cascade Impactor
Andersen - 2000
Casade Impactor
Litton large
volume air
sampler (LVAS)
Litton large
volume air
sampler (LVAS)
Air flow rate
0 028 mVmm
(Km)
0.028 nWmm
1 0 rtvVmin
fluid flow
rate -6 to
10 ml/mm
Voltage - 10-
15kitovolts
Same as above
Collection time
15min
30 mm
15 mm
Same as
above
Table 17. Sampling Methods:
Constituent
Total suspended
particulates
Trace metals
(V, Cr, Mn, Ni,
Cu.As, Se, Cd,
Sn, Sb, Hg, Pb)
Gases
(N02, S02, 0,,
NH3, HS)
Sampler
RAC hi-volume air
sampler
RAC hi-volume air
sampler
RAC five - gas
bubbler trains
Air flow rate
45-60 dm
40-50cfm
200 ml/mm-
SCv NOj, CI2,
H2S, 5 l/mm-NHa
Collection time
24 hours
24 hours
24 hours
Media
Trypticase soy-agar
(BBL) with actidione
M-endo broth with
1 5% Bacto-agar
(Difco)
Phosphate buffered
water, 0.01% phenol
red and 25% trypti-
case soy broth (BBL)-
oollection. M-endo-
broth - assay
Same as above
except M-FC broth
used for assay
Incubation
35°C
48 ±5 hours
35°C
24 ±2 hours
35°C
24 +2 hours
44±05°C
(water bath)
24±2hours
Sampling period
5 intervals in each
2-week period, April
18-Nov 30,1977
Same as aerobic bac-
teria, except started
Sept 13-Nov 30,1977
Approximately every
2 weeks, Aug 24
toNov 30
Same as above
Non- Viable Constituents
Media
Glass fiber filters
Whatman 541 filters
Specific collection
Fluid for each gas
Analysis method
Pre and post weight
X-ray fluorescence
spectrometry
Spectrophotometnc
methods, specific
for each gas.
Sampling period
Every fifth day, May
19 -Nov. 30, 1977
Every fifth day,
June 28 - Nov 30
Every fifth day,
May 19 -Nov. 30
I
89
if
sr
M
§.
"S
r
?+
§
-------
R. Northrop, et al
201
12.
T3
•i-li uJv
• - f - \
SAMPLE LOCATIONS: O VIABLE, A NON-VIABLE
Rgure 4. Map of Sampling Sites
ment on a relatively flat roof not easily accessible to vandals and far
from building exhaust systems.
The on-plant sites (1-4), community sites (5-10), and non-viable sites
(A-E) are depicted in Figure 4.
One-liter grab samples were collected at the inlet manifold of one of
the aeration tank batteries in order to determine the concentrations of
the pollutants which might be aerosolized.
RESULTS
The environmental monitoring program was designed to answer two
questions: 1) What are the exposures of people living in the study area
to air pollutants, and 2) Is the Metropolitan Sanitary District's North
Side Sewage Treatment Plant a source of air pollution for the surround-
ing community?
Summary of Environmental Data
A detailed record of the meteorological conditions during the study
period was an important component of both the environmental sampling
and data analysis efforts.
The wind rose diagram for the study period is based on on-plant
measurements and is shown in Figure 5. It shows no strong predominant
wind pattern. The most frequent wind direction was southwest for only
-------
202
Wastewater Aerosols and Disease/Population Studies
N
12.4%
10.4%
17.6%
Q 10.8%
18.6%
0-5 6-10 11-15 >15
Wind Speed, miles/hour
Figure 5. Wind Rose Diagram Based on On-Plant Measurements Dur-
ing Study Period
18.6% of the study-period hours. The most frequent wind direction
measured at Midway was south for 24.6% of the study-period hours.
Sampling runs consisted of air sampling at four sites and the collection
of an on-plant sewage sample. These sites, which were selected based
on the previous hour's vector-averaged wind direction, were 0.8 km
upwind from the plant, on the plant grounds downwind of the aeration
tanks, 0.8 km downwind of the plant, and 1.6 km downwind of the plant.
Sampling sites 1 through 4 (Figure 4) represent position "on-plant down-
wind." Sites 13 through 20 were always position "1.6 km downwind."
Sites 5 through 12 were positions 0.8 km upwind or 0.8 km downwind
depending on the wind direction.
-------
R. Northrop, et al 203
A total of 72 Andersen runs for total viable particles and 26 Andersen
runs for total coliform and 83 sewage samples for total aerobic, coli-
form, and fecal coliform bacteria were collected. Forty-eight of the
viable runs were in the summer and 24 in the fall. Twenty-two of the 26
total coliform runs were in the fall. Table 18 shows the average total
viable particle and average total coliform particle concentrations for the
four positions. Table 19 shows seasonal differences for total viable parti-
cles by position. Table 20 shows average total viable particle and coli-
form concentrations by sampling location and wind direction. Table 21
gives average concentrations for total viable and total coliform particles
summarized by median size distribution. About 70% appeared to be
greater than 4.7/101 in diameter. On the average, 95% of the total viable
particles discharged from the plant were greater than 2.1;um, while 99%
of the total coliform particles were greater than 1.1 M m. Airborne meas-
urements of total and fecal coliform taken with the LVAS are shown in
Table 22. Averaga sewage concentrations by month and for the 8-month
study period are shown in Table 23.
Sampling for nonviable pollutants was carried out every 5 days from
April 4 to Novemer 30. Air samples for all 20 parameters were collected
at the plant for every collection period. Of the remaining four sites, two
were used to collect TSP, SO4=, and NOs~ while two were used to
collect samples of the five gases and 12 metals.
Table 18. Average TVP and TCP Concentrations by Sampling Site
Position
Total viable particles Total colrform
Sampling
site
position"
0.8 km upwind
On-plant downwind
0.8 km downwind
1 .6 km downwind
Mean
concentration
(partides/mj)
143 (62)''
376^(68)
198<(68)
218^(60)
Standard
deviation
(partides/m3)
123
339
155
262
Mean
concentration
(particles/m3)
1 15 (26)"
6 87^(26)
1 15 (25)
1 01 (24)
Standard
deviation
(partides/m3)
1 8
89
20
22
"Position relative to plant
''Number of samples in parentheses
•Significantly greater than the upwind value (p < 0.05)
Table 19. TVP Concentrations by Season and Sampling Site Position
Total viable particle concentrations (partides/m3)
Sampling
site
position"
0.8 km upwind
On-plant downwind
0.8 km downwind
1 .6 km downwind
Summer
Mean Standard
concentration deviation
143 (38)" 125
379 (43) 385
186 (44) 152
230 (37) 281
Fall
Mean
concentration
144 (24)*
372 (25)
221 (24)
199 (23)
Standard
deviation
123
245
161
232
"Position relative to plant
''Number of samples in parentheses
-------
204
Wastewater Aerosols and Disease/Population Studies
Table 20. Average TVP and TCP Concentrations by Sampling Site and
Wind Direction
Downwind concentrations
(particles/m3)
Upwind concentrations
(partides/m3)
Sampling
site
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
L^IOldl H*C
from plant
(km)
—
—
08
08
08
08
08
08
08
08
1 6
1 6
1 6
1 6
1 6
1 6
1 6
1 6
Total viable
particles
447
381
347
354
268
191
155
199
294
93
228
232
169
580
200
60
174
248
171
144
(12)"
(21)
(21)
(13)
( 6)
( 8)
(14)
( 7)
( 7)
( 9)
(13)
( 4)
( 6)
( 9)
(10)
( 6)
( 6)
( 8)
(12)
( 3)
Coliform
396
342
1708
1220
1 10
260
1 20
1 10
037
000
203
073
1 10
000
000
055
( 7)«
(12)
( 5)
( 2)
( 6)
( 3)
( 9)
( 2)
( 3)
(12)
( 6)
( 3)
( 8)
( 2)
( 3)
( 2)
Total viable
particles
59
157
135
378
227
161
118
54
( 7)"
(10)
(12)
( 3)
( 5)
( 6)
(16)
( 3)
Coliform
037
000
094
037
1 97
1 65
(3)"
(2)
(7)
(3)
(9)
(2)
"Number of samples in parentheses
Table 21. Median Size Distributions for TVP and TCP Based on All
Samples
Total viable particles
Stage
1
2
3
4
5
6
Total
Diameter (/^m)
>7
47-7
33-47
21-33
11-21
0 65 - 1 1
TVP/m3
103
54
43
18
13
5
236
%
43
23
18
8
6
2
100
Total Coliform
Coliform/m3
1 28
065
040
013
008
002
256
%
50
25
16
5
3
1
100
Table 22. Average Concentrations of Total Coliform and Fecal Coliform
Collected with an LVAS by Distance from Plant
Total Coliform/m3"
Fecal Coliform/m3
Location
on-plant upwind
on-plant downwind
0 8 km downwind
1 6 km downwind
Mean
concentration
056 (&)>'
987 (7)
0 37 (6)
272 (4)'
Standard
deviation
0.47
6.82
046
235
Mean
concentration
0 1 1 (7)*
1 91 (8)
004 (7)
0 29 (3)<
Standard
deviation
027
271
008
050
"Significantly different at the 0.01 level by analysis of variance
'•Number of samples in parentheses
•One sample was collected at site 14
-------
R. Northrop, et al 205
Table 23. Summary of Sewage Microbiology
Total aerobic bacteria
Averaging -
period
1977
April
May
June
July
August
September
October
November
April-
November
(10V100ml)
No of
samples
6
10
11
11
5°
10*
10
13
78
Mean
155
525
20
59
889
30
40
39
165
Standard
deviation
96
1.323
19
54
1,789
40
21
24
659
Total colrform
(ICKVIOOml)
No. of
samples
6
10
11
11
11
11
10
13
83
Mean
37
65
19
26
104
70
64
42
54
Standard
deviation
16
109
12
24
85
44
30
25
59
Fecal coliform
(10V100ml)
No of
samples
6
10
11
11
11
11
10
13
83
Mean
35
67
40
58
128
120
73
79
78
Standard
deviation
32
67
29
34
59
52
36
59
56
"Plus one sample of > 10V100 ml, five samples were > 10V100 ml
'Plus one sample of < 10V100 ml
Tables 24 through 26 show the particulate matter and gas data aver-
aged by location for the study period. The maximum average assumes
all concentrations below the detection limit are equal to the detection
limit. The minimum average assumes that all concentrations below the
detection limit are equal to zero. The actual concentration falls between
these averages. All concentrations are in jug/m3. A summary of TSP
particle size distribution (based on plant site measurements) is given in
Table 27. About 50% (by weight) were greater than 3.3Mm. A summary
of nonviable sewage data is shown in Table 28. Number of samples,
detection limits, study period average concentrations, and standard de-
viations of all 12 pollutants measured are included.
Development of Personal Exposure Indices
Two viable and nine nonviable pollutants were selected for the model
to predict personal exposure indices for use in the health analysis. The
main criterion used in selecting these indices was the ability to reliably
measure the pollutant. In the case of fecal coliforms and many of the
metals, the study area concentrations were close to, or below, detection
limits.
The upwind and downwind average concentrations of total viable
particles and total coliform particles by sampling sites were summarized
in Table 20. Figures 6 and 7 show the data, separated by each sampling
sites' wind relation to the plant (up or downwind), projected over the
entire study area. These maps were generated using the SYMAP pro-
gram. This program uses an inverse-square weighting scheme to interpo-
late concentrations at every point within the study area from the concen-
trations at the 20 sampling locations. It was judged to be the best model
available because it integrates all meteorological and topographical con-
ditions by using all the air pollution data to interpolate concentrations in
the study area. A comparison of the downwind maps to the upwind
maps identifies the plant as a source of total viable and total coliform
particles within certain portions of the study area. The downwind total
viable particle map also identifies a second source of total viable parti-
cles near site 14. This source does not emit coliform particles.
-------
Table 24. Average Ambient Trace Element Concentrations by Site
Concentration'' (^ig/m3)
Sampling
site"
A
B
C
D
E
V
Average
max1
00045
0.0041
00043
0.0040
00073
Average
mm d
00021
0.0014
00019
0.0017
00047
Average
max
0.0318
00277
0.0327
0.0287
0.0385
Cr
Average
mm
0.0000
0.0000
00058
0.0000
00118
Mn
Average
max
00417
00361
00478
00459
0.0363
Average
mm
00292
0.0183
0.0380
00376
00262
Ni
Average
max
0.0118
00100
0.0115
00106
00104
Average
min
0.0003
00000
00006
00006
00000
Cu
Average
max
02141
03691
04247
0.3971
0.3123
Average
mm
02141
03691
0.4247
03971
03123
As
Average Average
max mm.
00109 0.0012
00086 00000
0 0099 0 0007
00100 00019
0 0093 0.0000
Concentration'1; jig/m3)
Sampling
site
A
B
C
D
E
Se
Average
max
00090
00081
0.0064
0.0074
00066
Average
mm
00025
0.0029
0.0017
0.0021
00041
Average
max
00157
00131
00149
00148
0.0170
Cd
Average
mm
0.0042
0.0000
00018
0.0033
00069
Sn
Average
max
0.0124
00111
0.0117
00115
00109
Average
mm.
00037
0.0021
00022
00022
0.0022
Sb
Average
max.
00120
00122
0.0114
00114
00117
Average
mm.
00018
00032
00000
00018
0.0024
Hg
Average
max
0.0134
00112
0.0129
00126
00116
Average
mm
00015
00021
00013
00026
0.0000
Pb
Average Average
max mm.
0 6083 0.6083
07412 07412
0 8400 0.8400
0 6455 0 6455
0 8394 0 8394
"See Figure 4 for key to sampling sites
''Determined from Whatman 541 filters analyzed by energy dispersive X-ray fluorescence spectrometry
'Average maximum assumes all concentrations below the detection limit are equal to the detection limit
''Average minimum assumes all concentrations below the detection limit are equal to zero
I
i
!?
5T
te
I
O
C/5
r+
I
8F
-------
Table 25. Average Gas Concentrations by Site
Concentration (yg/ms)
Cl.
NH3
NOj
SO,
Sampling
site"
A
B
C
D
E
Average
max k
13.55
15.25
13.39
16.73
14.81
Average
mm1
11 05
11 80
11 03
1359
11 42
Average
max
290
296
247
276
266
Average
mm
0.36
043
0.17
057
025
Average
max
46.39
5359
60.57
5485
5383
Average
mm
42.72
4732
57.01
5485
5349
Average
max
088
072
097
1 06
0.73
Average
mm
0.11
000
0.22
0.27
0.00
Average
max
10.49
13.98
13.68
1580
876
Average
mm
3.27
722
7.08
876
311
"See Figure 4 for key to sampling sites
''Average maximum assumes all concentrations below the detection limit are equal to the detection limit
' Average minimum assumes all concentrations below the detection limit are equal to zero
10
O
-------
208 \Vastewater Aerosols and Disease/Population Studies
Table 26. Average Ambient TSP, Nitrate, and Sulfate Concentrations
by Site
Average ambient concentratK>nb(^g/m3)
Sampling site" TSP NO3 SO4
A 7756 160 1408
B 74 47 1 40 11 31
C 8745 146 1343
D 8221 157 1303
E 68.13 144 1204
"See Figure 4 for key to sampling sites
''Determined from glass-fiber filters
Table 27. Mean TSP Size Distribution (Plant Site)
Stage Diameter (jjm) Average concentration" (ug/m3) Weight (%)
1
2
3
4
5
Total
>70
33-70
20-3.3
1 1-2.0
001-1 1
21 0
15.0
98
107
163
728
287
20.6
13.4
148
225
1000
"Based on 17 samples
Table 28. Summary of Nonviable Sewage Data
Constituent
S0« =
NCX,
V
Ni
Cu
As
Se
Cd
Sn
Sb
Hg
Pb
No of
samples
27
27
19
19
19
19
19
19
19
19
19
19
No Of
samples above
detection limit
27
27
0
19
19
19
0
19
19
10
0
19
Detection
limit
(M9/0
0 1
0 1
12
2
2
60
2
3
1
1
4
5
Study period
ave cone
(M9/I)
266"
76"
b
215
218
171
h
129
60
1 4'
h
280
Standard
deviation
(M9/I)
170"
46"
b
54
251
69
b
56
15
1 9-
h
141
"Concentrations in mg/l
kAII samples below detection limit
'Samples below detection limit averaged as 0 ng/\
-------
"X
*o ff
f
?/ /
O ; 6}
// /
£? .' J^
-S
^
AP
/
/
-------
to
h-»
o
I
&9
I
sr
as
g.
UPWIND
4(a)
Concentration Ranges, coliforms/m^
<1 0 1 0-2 0 >2 0
DOWNWIND
4(b)
0 5 km
Plant Boundaries
Figure 7. Study Area Concentration Profiles for Total Coliform Particles
(TCP)
I
M
-------
R. Northrop, et al 211
Exposure indices for total viable particles and total coliform were
developed by combining the modeled upwind and downwind concentra-
tions with the wind rose data for the study period as shown in Figure 5,
The process used to accomplish this is as follows: First, for each house-
hold in the study area, an upwind and a downwind exposure index were
predicted by SYMAP. Each household was then associated with the
closest wind direction of Figure 5. The percentage of the time each
household was upwind and downwind of the plant was calculated by
assuming that each house is downwind from the plant if the wind is
within a 135° arc directly across the study area from that house. For
example, if a household has been associated with the northwest direc-
tion, winds from the east, southeast, and south place that house down-
wind of the plant. Winds from the southwest, west, northwest, north,
and northeast place that house upwind of the plant. The house is, there-
fore, downwind of the plant 10.75% +7.04% + 13.39%, or 31.8% of the
study period and upwind 18.62% + 17.55% + 10.42% + 12.40% +
9.75%, or 68.75% of the study period.
The exposure index for each household is then calculated from Equa-
tion 4:
Exposure = (UPEXP) (% upwind) + (DOWNEXP) (% downwind)
(Equation 4)
Where: Exposure = household exposure index for study period
UPEXP = household upwind exposure
% upwind = percent of study period house was upwind
of the plant
DOWNEXP = household downwind exposure
% downwind = percent of study period house was downwind
of the plant.
UPEXP and DOWNEXP are predicted by SYMAP for each household
used in the analysis.
Two studies were carried out to check the accuracy of the process
described above. First, the study-period wind direction distribution was
compared to the wind direction distribution for sampling hours only.
These two distributions were almost identical. This allows the combina-
tion of study-period wind data and exposure values with no error result-
ing from possible abnormal winds during sampling.
Second, a validation of SYMAP's interpolation accuracy was carried
out. This was accomplished by dropping one of sites 5 through 12 at a
time and having SYMAP predict a concentration at the missing site. This
represents a worst-case analysis because at no point in the study area
does SYMAP have to search farther for adjacent sampling sites than
from one of sites 5 to 12 to the surrounding sampling points. The com-
parison between the actual and predicted concentration at sites 5
through 12 showed that SYMAP always interpolated an exposure index
to at least within a factor of 2 under worst-case conditions. This is
further confirmed by examining maps of downwind exposure when one
-------
212
Wastewater Aerosols and Disease/Population Studies
of the 0.8 km downwind data sites was missing. These maps all showed
the same pattern of elevated exposures into the community as is shown
in Figure 6.
In addition to the study-period average exposure indices for total
viable particles and total coliform, an exposure index for every 2-week
Health Watch period for total viable particles was calculated. Total
coliform was not used in the 2-week analysis because the data were all
collected in the fall. In addition, the accuracy of combining subgroups of
the data when the measurement is so close to the detection limit would
be questionable. The process of developing 2-week exposure indices
was the same as the study-period index. For each 2-week period, an
upwind and downwind exposure index was calculated for each house-
hold. These indices were then combined with a wind direction distribu-
tion from the same 2-week period using Equation 4. This resulted in 16
exposure indices for each household in the study.
Concentration Ranges, ug/m3
<0.0025 0.0025-00030 >0 003
0.5 km
Plant Boundary
Figure 8. Study Area Concentration Profile for Airborne Sn
-------
R. Northrop, et al
213
Analysis of Plant as an Emission Source
The calculation of household exposure indices for the nine nonviable
pollutants was much more direct than for the viable measurements.
SYMAP plots of nonviable indices represent study-period averages of
the nonviable indices integrated for all wind directions. It was, there-
fore, only necessary for SYMAP to interpolate an exposure index for
each household in the health study for each pollutant.
It is important to point out that all nonviable concentrations meas-
ured, with the exception of SO4=, were very low with respect to envi-
ronmental health standards and Chicago averages for the same seasons.
Chicago SO4= data were not available, so no comparison could be car-
ried out.
Distance-Concentration Relationships. All 20 nonviable and two via-
ble pollution indices were modeled by SYMAP to identify which pollu-
tants could be related back to the sewage treatment plant as an identifia-
t
Concentration Ranges,
<745 745-81 >81 0
0 5 km
Plant Boundary
Figure 9. Study Area Concentration Profile for Total Suspended Parti-
culates (TSP)
-------
214 Wastewater Aerosols and Disease/Population Studies
r
Concentration Ranges,
<510 510-65.0 >65.0
0.5 km
Plant Boundary
Figure 10. Study Area Concentration Profile for
ble source. For the viable indices, upwind and downwind maps were
plotted (Figures 6 and 7). For the nonviable indices, integrated wind-
direction maps as well as maps sorted by wind direction were plotted. Of
all 22 indices, only total viable particles (Figure 6), total coliform parti-
cles (Figure 7), and possibly tin (Figure 8) identify the plant as a source.
However, this pattern for tin is based on only 18 measurements above
the detection limit, and so this relationship to the plant is quite tentative.
Study-period average concentrations of TSP and NOa integrated for all
wind directions is shown in Figures 9 and 10, respectively. A set of maps
for TSP concentrations when winds were from the south, north, east,
and west are shown in Figure 11. The major source of TSP was Chicago
(south winds).
The total viable particle average concentrations show a decrease
with distance from the plant. Table 18 shows that the downwind total
viable particle concentration at the plant is greater than three times the
upwind or background concentration. At 0.8 km downwind of the plant,
-------
0.5 km
Westwinds
8(d)
Concentration Ranges,
<75 75-90 >90
Northwmds
8(a)
Southwinds
8(c)
eu i
EL
Figure 11. Total Suspended Paniculate (TSP) Concentration Profiles by Wind Direction
-------
216
Wastewater Aerosols and Disease/Population Studies
the average total viable particle concentration is still 45% greater than
the background concentration. The 1.6 km downwind average concen-
tration is also higher than the background concentration.
The total viable particle upwind and downwind maps, Figure 6, shows
that the plant contribution to the total viable particle air concentration
extends farther than 0.8 km downwind of the plant. The 1.6 km down-
wind concentration is higher than the 0.8 km downwind concentration;
however, this is partially the result of some other source or sources of
total viable particles located near site 14 (Figure 4). Such a source or
sources located near site 14 not only increase the downwind concentra-
tion at site 14 but also increase the 0.8 km upwind concentration at site
6. Removing site 14 and site 6 upwind from the analysis removes any
complications encountered because of the other possible sources at site
14. The remaining sites show a clear pattern of the effect of the treat-
ment plant on the surrounding community when they are downwind of
the facility (Figure 12).
Concentration Ranges, TVP/m^
<150 150-300 >300
0.5 km
Plant Boundary
Figure 12. Study Area Concentration Profile for Total Viable Particles
(TVP) Excluding Site 14 Downwind
-------
R. Northrop, et al 217
Table 29 shows the four average position variables without samples
collected at site 6 (when it was upwind of the plant) and site 14. The
downwind concentrations are all higher than the background concentra-
tion and decrease with distance from the plant. Figure 12 shows the
downwind study-area concentrations affected by the plant source only
and supports this conclusion.
Table 29. Average TVP Concentrations by Sampling Position Without
Sites 6 Upwind and 14 Downwind
Total viable particles
Sampling site
position"
0 8 km upwind
On-plant downwind
0.8 km downwind
1 6 km downwind
No of
samples
52
68
68
51
Mean concentration
(partictes/m3)
141
376*
198*
155
Standard deviation
(partides/m3)
121
339
155
144
"Position relative to plant
hSignrficantly greater than the upwind value (p < 0.05)
A one-way analysis of variance was run to test the significance of the
difference between the means of the four position variables. When run
both with and without sites upwind and 14 downwind, the difference
between position means is significant at the 0.05 level.
In order to determine which of the three downwind position means are
significantly higher than background, t-tests were run comparing the 0.8
km upwind concentrations to the plant, 0.8, and 1.6 km downwind con-
centrations separately. These tests were run both with and without sites
6 upwind and 14 downwind. When all 20 downwind and eight upwind
sites are included, the differences in concentration between 0.8 km up-
wind and all three downwind sites are significant at the 0.05 level. The
same comparisons when run on the data without sites 6 upwind and 14
downwind show that the plant and 0.8 km downwind concentrations are
significantly higher than background at the 0.05 significance level. The
1.6 km downwind concentration is not significantly higher than the 0.8
km upwind concentration at the 0.05 or 0.1 significance levels.
The total coliform concentration at the plant is six times greater than
any of the other position concentrations (Table 18). Assuming the 0.8
km upwind concentration represents background conditions, it appears
that the plant does add significant amounts of coliform to the air that
passes over it. By the time the air reaches 0.8 km downwind of the plant,
however, the coliform concentration returns to the background levels.
The plots of the upwind and downwind coliform concentrations (Figure
7) confirms this. A one-way analysis of variance showed the variation in
means of the coliform data to be significant at the 0.05 significance level.
The results from eight samples taken with the LVAS are shown in
Table 22. The LVAS and Andersen sampler do not measure the same
thing; therefore, the results cannot really be compared. Both the total
coliform and fecal coliform concentrations indicate that the plant is
contributing these organisms to the surrounding atmosphere but that this
-------
218 \Vastewater Aerosols and Disease/Population Studies
effect is no longer at a distance of 0.8 km from the plant. Relationships
with other parameters cannot be tested due to the small number of
samples collected.
The following conclusions appear to*be warranted: 1) the effect of the
plant on total viable particles is significant out to at least 0.8 km down-
wind and does not return to background until almost 1.6 km downwind;
and 2) the effect of the plant on total coliform concentration is signifi-
cant. However, because of the limited viability of coliform in air, the
concentration returns to background 0.8 km downwind from the plant.
In order to thoroughly compare the differences between the means
from all four positions, the Duncan multiple range test in conjunction
with a one-way analysis of variance was used. The Duncan tests show
when sites 6 upwind and 14 downwind are not included, that the plant
measurements of total viable particles and total coliform are signifi-
cantly higher than the other three position means at the 0.05 level of
significance. Log transformations are commonly used for air pollution
data because of extreme values. When the natural log of concentration
of total viable particles is used, the Duncan test shows that the plant
concentration is higher than the other three position concentrations and
that the 0.8 km downwind concentration is higher than background at
the 0.05 significance level.
Meteorology, Plant Operating Characteristics, and Concentrations. A
second approach to the characterization of the plant as an emission
source was a comparison between air quality measurements and sewage
characteristics, meteorology, plant operating parameters, and interac-
tion effects between these variables. The goal of this analysis was to
develop a model to predict viable concentration in the study area based
on meterology, sewage characteristics, and plant operating conditions.
A second goal was to determine if the plant was a significant source of
any nonviable pollution. When on-plant total viable particle concentra-
tions were compared using regression analysis with plant operating char-
acteristics (such as sewage throughput or air rate), or total aerobic bac-
teria in sewage concentrations, no obvious relationships were found.
However, sampling locations 1 through 4 (Figure 4) were not always
directly downwind. When the analysis is limited to those observations
± 22.5 from due east or west (sites 2 and 4), a rough association (r =
0.68, significantly different from zero at the 0.005 level) is evident
(Figure 13). These concentrations reflect air passage across maximum
tank surface areas. (The north-south distance is only 25% of the east-
west distance.) The spread in the data could not be further explained by
systematic differences in wind speed, temperature, or relative humidity.
Total coliform also did not show any striking relationships with sewage
concentrations or operating parameters.
Total viable particles and coliforms in air were compared using regres-
sion analysis with temperature, humidity, wind speed and direction,
solar radiation, and ultraviolet radiation for the plant and 0.8 km upwind
and downwind positions. No discernible relationships were found be-
tween total viable particle and coliform concentrations and humidity,
temperature, solar radiation, UV radiation, or wind direction. In order
to further delineate the effects of meterological conditions, a multiple
-------
R. Northrop, et al
219
1000-
2 800
S 600
O 400
0)
_ 200
S
o
o
oo
100 120 140 160 180
Aeration Tank Air Rate, 106ft.3/day
200
Figure 13. Total Viable Particle (TVP) Concentration Versus Aeration
Tank Air Rate
regression was done with wind speed, temperature, and relative humid-
ity as the independent variables and total viable particle concentration
as the dependent variable. Due to the low r2 of 0.11 (percentage of the
variance explained by these three variables), these meterological para-
meters cannot be considered to have a significant effect on total viable
particle concentration. Even less of the differences between total coli-
form concentrations can be explained by wind speed, temperature, and
relative humidity (r2 = 0.048) using this same method.
The TVP concentrations were correlated with the average NO2, SO2,
and TSP concentrations measured on the same day. A significant corre-
lation between NO2 and TVP concentrations was found for TVP meas-
ured at the plant (r = 0.64, significantly different from 0 at the 0.02
level). No correlation was found at any other sampling locations or with
either SO2 or TSP at any location.
No relationships (regression analysis) were found between plant non-
viable measurements and any plant operating or sewage characteristic.
The off-plant sites B, C, D, and E were analyzed by comparing upwind
and downwind measurements made at each site. No relationship was
found between TSP, SO4 =, NO3~, and any sewage or operating para-
meter. Sites C, D, and E are all 1.6 km away from the plant. Combining
these three sites for the wind direction analysis also did not produce any
relationship between a nonviable pollutant and a sewage characteristic
or plant operating characteristic.
Even though a variety of trace elements were found in the sewage
(Table 28) most are apparently not discharged into the air in sufficient
quantities to be notable. The same was true for NO3~ and SO4=. The
lack of correlation between operating parameters and any of the nonvia-
ble pollutants is somewhat puzzling, particularly in light of the fact that
both sewage throughput and air rate independently varied by almost a
-------
220 Wastewater Aerosols and Disease/Population Studies
factor of 2. Apparently the quantities of SO4=, NO3~, and trace ele-
ments which are aerosolized do not measurably contribute to the exist-
ing background concentrations. It may be that aeration tank surface area
and air discharge velocity are more important factors for emission of
pollutants to the atmosphere.
INTEGRATION OF HEALTH AND ENVIRONMENTAL DATA
Introduction
The major purpose of this study was to determine whether or not a
sewage treatment plant is a health hazard to a community. This was
investigated by integrating the environmental exposure data with the
health data for the study population in the community. The environmen-
tal data provided exposure indices for total viable particles, total coli-
form bacteria, and nonviable pollutants (TSP, metals, and gases) for
each household for the 8-month study period. The Health Watch data
provided household illness and infection rates for the same period. The
seroepidemiological survey provided the most valid incidence rates of
infection, but for only a few selected viruses. Finally, the retrospective
health questionnaire survey permitted the identification of persons po-
tentially at high risk to the health effects of viable and nonviable pollu-
tion exposure.
A dose-response approach was taken in the analysis of exposure and
health effects. Regression analyses were performed to determine if
health effects increased with exposure, or if the two variables varied
independently. Scatter diagrams were prepared to further examine the
relationship between exposure and health effects.
Total Viable Particle Exposure and Self-Reported Acute Illness
Acute Illness Rates and Total Viable Particle Exposure. Total viable
particle exposure indices for the 8-month study period were compared
with acute illness rates for each of the 290 Health Watch households.
Eight-month exposure indices were calculated with and without sites 6
(upwind) and 14 (downwind) since these sites reflected a source of total
viable (downwind) particles other than the plant. The range and mean in
particles/m3 for the exposure indices using all sites were 86 to 265 and
155, respectively. The range and mean for the indices excluding sites 6
and 14 were 86 to 264 particles/m3 and 158 particles/m3, respectively. In
relating illness rates to total viable particle exposure, it was necessary to
limit the illnesses to those types which potentially had a causal associa-
tion with viable particle exposure. With this in mind, the illness rates
were based on self-reported (diary) acute illnesses equal to or greater
than 1 day duration and were calculated for respiratory, gastrointestinal,
eye and ear, skin, and total illnesses. The 290 8-month household total
illness rates ranged from 0 to 71.43 and averaged 7.31 illnesses/1000
person-days of exposure.
Regression analyses of the 8-month household total viable particle
exposure indices and the corresponding 8-month household acute illness
rates were performed. No linear relationship (p > 0.05) was found for
these variables with or without sites 6 (upwind) and 14 (downwind). This
was true for the separate illness categories as well as all types of ill-
nesses combined. All of the correlation coefficients were <0.1 and not
-------
R. Northrop, et al 221
significantly different (p > 0.05) from zero. Scatter diagrams of total
illness rates and respiratory illness rates against total viable particle
exposure indices (calculated both ways) did not reveal any apparent
relationships missed by the regression analysis. The lack of correlation
between 8-month total viable particle exposure and illness rates may be
the result of an inadequate sample size (in terms of number of house-
holds), an unequal frequency distribution of household exposure indices
in terms of not having enough households exposed at "low" or "high"
levels of total viable particle concentrations, the inaccuracies in self-
reported illness rates, the existence of more complex functional rela-
tionships between the health and exposure variables, or no relationship
at all.
Temporal Acute Illness/Total Viable Particle Exposure Relationships
Regression analyses between illness and exposure were also per-
formed on a 2-week averaging period basis. These periods correspond to
the Health Watch data-collection periods. The same illnesses used for
the total viable particle analyses discussed above were calculated as
2-week period rates. Not enough total viable particle measurements
existed for the first data-collection period (April 3 to 16) so the analyses
were performed for only the last 16 2-week periods. No linear relation-
ships (p > 0.05) were found for the 2-week periods when analyzed
separately or together for all types of illnesses or for respiratory ill-
nesses only. Respiratory illnesses were considered separately since they
represented a large proportion of the total illnesses reported.
In order to examine a possible lag effect between exposure and illness,
a 2-week lag period analysis was carried out. This was accomplished by
correlating a 2-week period's illness rates with the previous 2-week
period's exposure indices. A 2-week period was the smallest lag period
possible to analyze. Again, no linear relationship (p > 0.05) between
2-week illness rates and total viable particle exposure measured 2 weeks
prior to the illness period was detected.
In addition to the explanations for lack of correlation provided in the
previous section, it was also possible that the 2-week lag period was too
long in terms of incubation period for most bacterial and viral agents
possibly associated with these illnesses. It was also important to note
that the 2-week exposure indices were much less reliable measurements
than those based on the total study period.
Acute Illness Rates for High Risk Subgroups and Total Viable Particle
Exposure
An attempt was made to examine the relationship between illness and
exposure for various subpopulations potentially at high risk to the ef-
fects of total viable particle exposure. Age, chronic respiratory disease,
chronic gastrointestinal problems, smoking, family composition (pres-
ence of young children), and length of residence in the study area were
considered potential risk factors. Regression analyses between the
8-month illness rates (as separate categories and as total illnesses) and
exposure indices were carried out controlling for each of these high-risk
groups.
-------
222 Wastewater Aerosols and Disease/Population Studies
The acute illnesses defined above were used to calculate rates for
persons within households belonging to a specific high-risk subgroup. A
person-exposure index was taken to be equal to a person-household
exposure index. The correlation coefficients for four age groups (0 to 12,
13 to 18, 19 to 59, and 59 years) did not reveal any linear relationships
between illness and exposure. A similar finding was derived for the 70
people with chronic respiratory disease (chronic bronchitis, emphy-
sema, or asthma). The correlation coefficients for persons with chronic
gastrointestinal problems were not significantly different (p > 0.05) from
zero. Regression analyses of smokers (current) and nonsmokers also
resulted in correlation coefficients not significantly different (p > 0.05)
from zero. Family composition was categorized as follows: 1) families
with only one or two members (all adults); 2) families with youngest
child age 0 to 5 years; 3) families with youngest child between 5 and 14;
and 4) families with youngest child over 13 years old. All but one corre-
lation coefficient (r = 0.27 for skin illnesses for families with youngest
child between 5 and 14) were not significantly different (p > 0.05) from
zero. Length of residence was considered in terms of less than 1 year, 1
to 5 years, 6 to 10 years, 11 to 20 years, and over 20 years of residence in
the study area. All but one coefficient (r = 0.39 for skin conditions in the
over 20 years of residence group) were not significantly different (p >
0.05) from zero. The correlation coefficients obtained for skin conditions
for families with youngest child between 5 and 14 years old and for
greater than 20-year residents are based on mean illness rates of 0.25 and
0.07 skin conditions/1,000 person-days of exposure, respectively, and
are therefore of questionable importance.
In summary, regression analyses of acute illness and total viable parti-
cle exposure with consideration given to high-risk variables did not re-
sult in any significant linear relationships. Again, the lack of any appar-
ent linear correlation between exposure and illness may be due to
inadequate sample sizes, an inadequate representation of exposure lev-
els, inaccuracy of the illness data, or the existence or nonexistence of
more complex relationships. Because of the consistent lack of any sig-
nificant relationships when each independent variable was considered
singularly, any multiple regression analysis would also be of no
significance.
Total Viable Particle Exposure and Infection Rates
Throat and Stool Specimens
As was reported earlier, 174 bacterial organisms were isolated from
throat cultures of children 0 through 12 years of age. Throat bacterial
infection rates were developed as follows:
throat bacteria infection = s unique bacterial isolations x 1,000
rate/1,000 person-days £ days present in study area for every
2-week data-collection period a
throat culture was received
(Equation 5)
These rates were then compared to the 8-month total viable particle
exposure indices. In Figure 14, the bacterial infection rates were plotted
-------
R. Northrop, et al
223
CD
C/5 ^
Q>
£ «
"ro
CD
C
O
CD
0_
O
TO
CD
— O
ro O
O O
CD
a
Figure
70
60
50
40
30
20
10
0
---- Staph. only
r i i i i I r-M i i is i\ i i i /f Ax i\i ILL!
ooooooooooooo
•^COCMCOO^COCNJIQO'^CO
Total Viable Concentration, particles/m^
14. Respiratory Infection Rates Versus Total Viable Particle
(TVP) Exposure
for Staphylococcus aureus and all other bacteria combined. S. aureus
was specifically plotted because it is most frequently transmitted from
person to person and is unlikely to be of environmental origin. Both
rates of bacterial infection were unrelated to total viable particle expo-
sure; the two distributions of infection rates were similar. Thus, there
appears to be no dose-response relationship between viable particle ex-
posure and bacterial infections. Regression analysis confirmed the lack
of a linear relationship between infection rates and total viable particle
exposure (correlation coefficient = 0.07).
Serosurvey
Analysis of virus infections was possible by comparison of the total
viable particle concentration of household exposure with infections due
to coxsackieviruses and echoviruses as determined serologically. Re-
gression analysis of the initial virus antibody tilers and total viable parti-
cle exposure indices was carried out for each of the coxsackieviruses
and echoviruses. None of the correlation coefficients were significantly
different (p > 0.05) from zero. Table 30 shows the number of sera tested
which showed a fourfold rise in antibody and the number of sera tested
in which a rise was not found for any of the five coxsackieviruses and
four echoviruses tested. Also shown are the mean total viable particle
exposure indices associated with each serological group. The total via-
ble particle exposure was less for persons with no seroconversions (160)
compared to those with at least one antibody rise to one of the types of
-------
224 Wastewater Aerosols and Disease/Population Studies
Table 30. Summary of TVP Exposure for Viral Seroconversions
Total viable particle exposure
(partides/ma)
No antibody rises/sera
Mean
Range
Coxsackie viruses B1-5
0 (272)°
>.1 (46)
EchovirusesS, 6, 9, 12
0(292)
>1 (25)
160
175
163
145
86-411
86-411
87-411
86-392
"No of sera tested indicated in parentheses
coxsackieviruses (175). A different pattern was observed for the echovi-
rus conversions which suggested an inverse relationship between expo-
sure and frequency of infection. The differences observed were not
remarkable enough to suggest that the risk of infection was greater or
less due to increased exposure to total viable particles.
Similar analyses were carried out for only those who were susceptible
to the viruses under varying criteria for "susceptibility." Five different
"susceptible" definitions were used: those with an initial liter of < 10,
< 10, < 20, < 40, and < 80. In comparing the mean exposure index for
those susceptibles who had experienced at least a fourfold rise against
the index for susceptibles who had experienced less than a fourfold rise,
no significant differences (p > 0.05) were seen for any of the "suscep-
tible" groups for any of the viruses or virus groups.
Total Coliform Bacteria Exposure and Self-Reported Acute niness
Regression analyses of total coliform bacteria exposure indices and
corresponding acute illness rates were made for each household. The
total coliform bacteria exposure indices cover a 12-week period since
total coliform measurements did not begin until September 13. The
range of the 290 household exposure indices (all sites) was 0.25 and 3.55
particles/m3 with a mean of 1.42 particles/m3. The illness rates used for
this analysis were based on the same criteria described for the total
viable particle analyses and correspond to the data-collection periods
covered by the exposure index (September 18 to November 26). No
linear relationship was found for respiratory illnesses or for all illnesses
combined.
Exposure to TSP, Metals, and Gases and Self-Reported Illness
The 8-month exposure indices developed for NO2, SO2, TSP, NO3~,
SO4~, V, Mn, Cu, and Pb represent an adequate characterization of the
study area exposure for those nonviable constituents. Although these
constituents were found not to be associated with the sewage treatment
plant, regression analyses between exposure and illness were performed
to search for an association between these constituents and health.
-------
R. Northrop, et al 225
The illness rates used in these regression analyses included chronic
conditions and conditions lasting less than 1 day. No linear relationship
(p > 0.05) was found between the household illness rates and corre-
sponding household exposure indices for any of the nine constituents.
This was the case for all illnesses combined as well as for the separate
illness categories (respiratory, gastrointestinal, skin, etc.). Scatter dia-
grams of the illness rates and corresponding exposure indices also did
not reveal any apparent linear relationships.
DISCUSSION
MR. LINDAHL: Is it not true that the design of this particular plant
is different from every other aeration plant in the world, and that this
particular rate of aeration or design of aeration facility is different from
any other in the country and the world?
DR. LUE-HING: May I answer that one?
MR. POLONCSIK: Please.
DR. LUE-HING: As far as I know, this is a basic design and the
rates are comparable. I am not aware of any difference. The rates vary
because the plates are older.
DR. DEAN: I think there is more information in your paper due to
performance. I mean in this sense, most of the work that you did as-
sumed that you had the data for the distribution. It is quite obvious from
the data that you did not have a normal distribution of bacteria or vi-
ruses. There is a tendency to be abnormal, from what I can tell from the
standard deviations.
If this is true, and it is very easy to check, you are going to get a
different interpretation if you will go the way of log normal distribution.
It will not cost any more. Your suggestion that certain differences are
significant may be erroneous because the evidence is based on a normal
distribution.
MR. SCHEFF: I am not the statistician, but we did do log transfor-
mations of all the data and we found no different patterns. I don't
believe we stated that we found any differences that were statistically
different. Maybe there was one or two statistically, but that would be
expected in a large number of analyses. I don't think we put anything
behind the differences.
DR. DEAN: The only part that would be useful would be in estimat-
ing the power. How big a difference would there have to be to figure it
out at all? Then you will get a better estimate of the power.
DR. FLIERMANS: I have a question and then a comment. Are the
trends that you saw for the respiratory illness a common phenomenon?
DR. NORTHROP: The season that we looked at was through No-
vember, that is, after school begins in September, and you begin to see
an increase in the respiratory illness. What we did not see, that I might
have expected, was an increase in gastrointestinal illness at the end of
the summer. I think the epidemiology of gastrointestinal disease asso-
ciated with infectious enteric agents isn't classical like it was a number
of years ago. Immunizations and different social patterns have changed
that.
-------
226 Wastewater Aerosols and Disease/Population Studies
DR. FLIERMANS: But let me make a comment relative to the kinds
of things that you see with visionalosis. This is the same kind of thing
that you have observed. We know that the mouth would not survive
without tap water for an extended period of time. Maybe we are looking
at the wrong end of the individual. Maybe we ought to look at the
respiratory end and some of the organisms associated there. You have
many situations where the organism can be transported.
DR. NORTHROP: Well, in terms of Legionella, we are doing an
evaluation of the material that we have. That is in progress, so I will be
able to specifically relate to that later. Transmissibility of Legionella is
unestablished for man. It comes from the environment to man and it is
not clearly understood.
DR. FLIERMANS: I think the CDC has a good body of evidence of
inhallation in the type of situations where legionelosis is contracted by
that kind of exposure, which to me becomes very important if you are
talking about aerosols.
DR. NORTHROP: Correct. That is what we are trying to establish
now. In terms of households, one member of a family acquiring it in
household transmission, I would not expect that.
DR. FLIERMANS: Yes, there is no evidence of transmission.
DR. ANDELMAN: It seems to me that there are two obvious
marked differences between the results of your study and the previous
one. One is that you did not find any obvious health effects. The second
is, by using your personal exposure index, that you did indeed obtain a
correlation with wind direction. That seemed the logical thing to do. I
am wondering if, perhaps, you tried also to do as the previous investiga-
tion did. Just look at the question of proximity as an alternative.
MR. WADDEN: Indeed we did look at this distance from the plant
to see how good our exposure index was. We didn't see any differences
as far as we now can tell. This is perhaps not unexpected because if you
look at patterns, it is reasonably centered around where the plant is and
that's true. But we did look at that.
I would like to expand a little on another point, which was that we did
not find the kinds of results that some other people found important. I
think it is well to remember that the kinds of concentrations we were
looking at were much lower, usually, than what other people have seen.
I have seen this data, and it had much higher concentration. Indeed, that
was a problem with our monitoring because we expected a much higher
initial concentration than we were able to receive.
DR. GERBA: I have two questions. I wonder if your lower concen-
tration may be related to something like open air factor where it has
been absorbed in captured aerosol disposed in the country versus in the
city. Maybe viral fallout is more rapid in the captured aerosols in the city
rather than the country. This may be one thing to consider when you are
studying an industrialized area. The organism's survival time in the
aerosol may be much less in the city. Maybe Dr. Spendlove could com-
ment on open air background.
I have one other question, that is related to how much confidence you
can really put in your antibody data, especially with the aerosols. I make
special reference to the study on the antibody response in adults. They
were studied over a period of a year and they had become, during the
-------
R. Northrop, et al 227
course of a year, exposed several times with viruses, but no antibody
response occurred in those individuals. This was a study over some 30 to
40 different adults. How much faith should we really put in the antibody
data?
DR. NORTHROP: I think our serology is probably the most solid bit
of health information we have. Those are neutralizing antibody levels
that are the basis of the tilers reported here and the basis for the sero-
conversions. I think that is something that really needs a lot of investiga-
tion. Serologically, it is my understanding that after a few years of age,
90% of the populations will have it. Therefore, you would have to look
at a very young population prospectively with exposure information.
Just to look at a population such as we had, would not be justifiable
with the current state of the art. The Norwalk agent, which is another
associated agent in the feces and diarrhea, is a different type of agent
and hopefully could be used in the kind of study that is conducted here.
This, in addition to Legionella, is something we are looking at.
DR. SPENDLOVE: The concentration is not what I suspected. I
suspect that perhaps this will be associated with the other studies.
MS. HOLDEN: I am not sure we can say that, and that is why I did
the nonviable pollutant/viable pollutant correlations. Maybe you can tell
us what pollution factors have been associated with decreased numbers.
It is definitely not associated with total suspended particulates or SO2.
Unfortunately, we had no carbon monoxide or carbon dioxide
measurements.
DR. SPENDLOVE: I suspect that SO2 will have some effect.
MS. HOLDEN: No, unfortunately, and I should have mentioned it.
We only had about 12 sampling days on which we did nonviable and
viable together on the same day. So that makes that correlation a lot less
reliable. However, we were not in the city. That's an additional factor.
-------
228
Epidemiological Study of Wastewater Irrigation in
Kibbutzim in Israel
H. I. Shuval and B. Fattal
Environmental Health Laboratory
The Hebrew University-Hadassah Medical School
Jerusalem, Israel
ABSTRACT
A retrospective epidemiological study was carried out from 1977 to 1979 in Israel on the
association between enteric disease incidence and effluent irrigation in 83 kibbutzim (co-
operative agriculture settlements) with a total population of 41,000 We collected medical
data from patient records at each kibbutz's medical facilities The medical data collection
consisted of 24 defined diseases, laboratory or clinically confirmed, about 50% of which
were of the enteric disease group. The second group consisted of nonenteric diseases
which served as a control Environmental data was collected by means of a questionnaire
filled out on site with the aid of the kibbutz coordinator The preliminary results reported
in this paper are based on data from a study of 36 kibbutzim with a population of about
14,000
The research reported was divided into two categories:
• 13 kibbutzim which practiced 2 consecutive years of using effluent sources for
irrigation at least part of the year and an additional 2 consecutive years in which
only noneffluent water sources were used for irrigation
• 23 kibbutzim, 12 of which used effluent sources for irrigation in addition to nonef-
fluent sources. The other 11 kibbutzim used only noneffluent sources for irrigation
The primary means of irrigation used by the kibbutzim was the sprinkling system.
In the first group, we compared total enteric disease incidence during the 2-year effluent
irrigation period to the enteric disease incidence during the noneffluent irrigation period. In
the second group, we compared the enteric disease incidence in the kibbutzim using
effluent irrigation with the enteric disease incidence in the kibbutzim using only noneffluent
irrigation sources.
The results were analyzed according to the age groups of the population, the irrigation
season, and other environmental factors. Inspection of overall incidence of enteric disease
incidence in the first group (for the different age groups) does not appear to show evidence
of the association between the effluent and noneffluent irrigation years at the same kibbutz.
In an analysis of various environmental factors in the second group, in no case was there
any apparent difference between effluent-irrigating and noneffluent-irrigating kibbutzim.
Additional in-depth analysis for the entire group of 83 kibbutzim is underway There-
fore , no final conclusions can be drawn at this time
The use of wastewater effluent in agriculture is becoming common in
many areas of the world, including the United States, as a means of
increasing water resources through recycling. This utilization is also
regarded as a strategy for reducing pollution of surface waters.
Israel suffers from a severe shortage of water resources; over 95% of
the available water supplies are currently being utilized. This situation
has led to the extensive use of wastewater in Israel for irrigation of
various crops and for enrichment of fishponds. Irrigation methods used
-------
H. /. Shuval and B. Fattal 229
in Israel today are sprinkler and drip. About 90% of the total irrigation is
done by sprinkling. The amount of sewage potentially available for ex-
ploitation in Israel is about 200 million m3/year. About 20% was recycled
in 1979, with the area of land irrigated with wastewater reaching 8,000
hectares.
The extensive use of effluent in agriculture creates a potential health
hazard for field workers and the population adjacent to the fields. Hu-
mans may possibly be infected by aerosols containing pathogenic bac-
teria or viruses by inhalation of particles of 0.5-5.0 ^m which penetrate
the respiratory system. The larger droplets, however, can be trapped in
the upper respiratory system, including the nose and larynx, and from
there they may reach the digestive tract. Other modes of transport of
pathogens from areas irrigated with wastewater are by direct contact
with irrigation workers, contaminated crops, and fomites.
Mickey and Reist (1) reported that pathogenic bacteria may be trans-
ported in aerosols from sewage to humans. In a later survey, Clark, et al
(2), emphasized the potential risk to sewage workers of enteric diseases
from occupational exposure. Adams and Spendlove (3) isolated mi-
croorganisms from aerosols at a distance of 1200 m downwind from a
sewage treatment plant. However, there is little proof of the degree of
health risk from aerosolized sewage.
The Environmental Health Laboratory of The Hebrew University-
Hadassah Medical School has succeeded in isolating coliforms at a dis-
tance of 350 m and salmonella at a distance of 60 m downwind from the
wastewater irrigated fields (4). Also, they succeeded in isolating entero-
viruses at a distance of up to 100 m downwind from effluent irrigation
(5).
One of the first retrospective epidemiological studies on the possible
health risks associated with sprinkler irrigation with wastewater was
carried out by our group in Israel (6). In this study, the authors were able
to show that in 77 kibbutzim (agricultural cooperative settlements) prac-
ticing mainly sprinkler irrigation with undisinfected oxidation pond ef-
fluent that the incidence of typhoid fever, salmonellosis, shigellosis, and
infectious hepatitis was two-four times higher than in 130 control kib-
butzim not practicing any form of effluent irrigation.
The researchers themselves pointed out that from this study they
could not provide definite proof that the added health risk in effluent-
irrigating kibbutzim was associated with the dispersion of pathogenic
microorganisms by aerosols, because a number of pathways of infection
other than aerosols existed, such as direct contact via clothing or bodies
of sewage irrigation workers or exposure to the crops.
This preliminary survey also had serious methodological constraints
in that the investigators based their findings solely on official communic-
able disease reports which were submitted to the Ministry of Health as
required by law. These requirements do not include listing of all relevant
diseases, and there are known serious defects in such reporting meth-
ods. Therefore, no conclusive findings may be based on this report.
Consequently, new research, based on primary medical and environ-
mental data collected at each kibbutz, as proposed by this project, is
necessary to confirm or rebut the findings of the initial retrospective
study of wastewater irrigation in kibbutzim.
-------
230 Wastewater Aerosols and Disease/Occupational Studies
Working Hypothesis
In this retrospective study it is proposed to study the difference in
enteric disease incidence by comparison of the disease rate in accord-
ance with the following categories (Table 1).
Definitions of Categories:
• "Effluent-Irrigating Kibbutzim" (A and B) are those kibbutzim
which utilize both their own sewage and/or that of nearby urban
settlements for effluent irrigation and are assumed to be either ex-
posed to aerosolized sewage and/or to other pathways of transmis-
sion such as food and body contacts or transmission by fomites.
• "Noneffluent-Irrigating Kibbutzim" (C) are those which do not
practice effluent irrigation (but do utilize other sources of water)
and are not exposed to aerosolized sewage from effluent-irrigated
neighboring fields at a distance of up to 5 km from residential areas.
• "Exposed to (Sewage) Aerosols" (A) are those kibbutzim which
are within 800 m from sewage-irrigated fields and their residential
area is within the aerosol plume at least 70% of irrigation time.
• "Not Exposed to Aerosols" (B) are those kibbutzim practicing
wastewater irrigation but where the residential area is at least 1.5
km from effluent-irrigated fields and is predominantly upwind i.e.,
70% of the time, or where the method of irrigation is not by sprin-
kler irrigation.
• "Effluent in Fishponds" (D) are those kibbutzim which utilize their
own sewage and/or that of adjacent settlements for enrichment of
their fishponds. Some of these kibbutzim use the fishpond water
after drainage for crop irrigation.
Using the above categories, we will examine the following working
hypothesis:
• The enteric disease incidence rate in the irrigation season in ef-
fluent-irrigating kibbutzim (A2, B2) is significantly higher than in
noneffluent-irrigating kibbutzim (C2) i.e. A2 and B2 > C2. On the
other hand, we do not anticipate an increased enteric disease inci-
dence rate in the nonirrigation season, At = Bt = Ci.
• The control disease incidence rate in effluent-irrigating kibbutzim
(A and B) will not be any different from the rate in the noneffluent-
irrigating kibbutzim (C) regardless of the irrigation season, i.e. A =
B = C.
Table 1. Classification of Kibbutzim by Use of Effluent
Season Type of kibbutz
Effluent-irrigating Non effluent-irn-
kibbutzim gating kibbutzim
Nonirrigation
Irrigation
Exposed
to
Aerosols
A,
AS
Not
Exposed
to
Aerosols
B, C,
B, C,
Kibbutzim utilizing
effluent in fishponds
D,
D,
-------
H. J. Shuva/ and B. Fatta/ 231
• We anticipate that in the irrigation season the enteric disease rate
will be higher for effluent-irrigating kibbutzim which use sprinklers
and are exposed to aerosols (A2) than for effluent-irrigating kibbut-
zim not exposed to aerosols (B2) i.e. A2 > B2.
• If the rates of enteric disease in kibbutzim utilizing sewage for
fishpond enrichment (D) is greater than those kibbutzim which are
noneffluent- irrigating kibbutzim (C) (D > C), then it is possible to
conclude that the reason is associated with the sewage in fishponds
and the pathogen spread is by the direct contact with fishpond
workers or by contact with or eating of polluted fish.
The kibbutz in Israel is a good model which allows us to thoroughly
investigate the above hypothesis. There are many kibbutzim which use
sprinkling irrigation and in which the main sewage treatment is non-
disinfected oxidation ponds. In contrast, there are other kibbutzim
which neither use effluent nor use sewage for fishponds. In each kibbutz
there is a clinic staffed with a nurse and serviced by a physician. In
addition, there are regional laboratories which perform routine com-
municable disease examinations for the kibbutzim. Another advantage
is the high level of consciousness of the kibbutzim in health matters as
well as their capability to record the environmental and medical data and
their willingness to cooperate with a research effort of this kind.
Materials and Methods
There are 224 established kibbutzim in Israel which have a total popu-
lation of 93,000. Due to budgetary and time limitations, we selected 83
kibbutzim for study.
The selected kibbutzim fell into four categories:
• 30 use effluent for irrigation and do not have fishponds; the total
population is about 17,000
• 30 do not use effluent for irrigation and do not have fishponds; the
total population is about 15,500
• 10 use effluent only for fishponds; the total population is about 5,000
• 13 used effluent sources for irrigation for at least part of the year for
2 consecutive years and another 2 consecutive years in which only
noneffluent water sources were used for irrigation; the total popula-
tion of the switched categories group is approximately 4,300.
Our study is based on retrospective data collected from several
sources:
• Personal medical records of kibbutzim populations. The data was
culled from these records for the period January 1, 1974 to Decem-
ber 31, 1977. Of the 24 diseases chosen, about half of them were
enteric diseases which could be wastewater borne and the other half
were control diseases. A list of the selected diseases appears in
Table 2.
• Interviews, These were conducted with the agricultural managers of
the kibbutzim to obtain environmental and demographic data such
as use of effluent, volume of effluent used and treatment of same,
methods of irrigation, the size of sewage-irrigated tract and type of
crops, and the distance of the tracts from the fields to the communal
dining halls.
• Meteorological data. Retrospective data was collected from the
-------
232 Wastewater Aerosols and Disease/Occupational Studies
Table 2. Selected Diseases from Kibbutz Clinic Patient Records
Enteric diseases Control diseases
Typhoid fever Measles
Paratyphoid Chickenpox
Other Salmonella infections Accidents
Bacillary dysentery Rubella
Gastroenteritis Mumps
Aseptic meningitis Pneumonia
Infectious hepatitis Bronchitis
Pathogenic coh; urinary tract infections Upper respiratory infections
Food poisoning (bacterial) Streptococcal throat infections
Fever of unknown origin
Coxsackievirus infection
Parasitic infections
Amebiasis
Leptospirosis
Meteorological Service which collected data from 55 stations dis-
persed throughout the country.
Results
Stage I: Kibbutzim which switched categories
Tables 3 through 5 present the results of the analysis of those kibbut-
zim which switched categories from effluent irrigation to noneffluent
irrigation or vice versa. Of the 13 kibbutzim studied, two had to be
dropped due to insufficient data, reducing the total population to 3,950.
From Table 3 no apparent difference in the enteric disease rate could be
detected between a wastewater- and nonwastewater-irrigation period. In
addition to disease rate/1,000, we calculated the ratio of enteric disease
incidence to total disease incidence. The rates and ratios for the total
group studied are presented in Table 3 and a breakdown by kibbutz is
presented in Table 4. It should be noted that influenza is included in
Tables 3 and 4, but parasitic infections, amebiasis, and leptospirosis are
not included.
Based on the calculated ratio for each year, for each kibbutz we
ranked each year's ratio from 1 to 4 (from low to high). The sum of the
ranks for kibbutz equals 10 (1 -f- 2 + 3 + 4). We then summed the ranked
Table 3. Comparison of Disease Incidence in Kibbutzim with Sequen-
tial Two Year Periods of Effluent and Non-Effluent Irrigation
(Switched Category)"
2 years of
noneffluent irrigation
No of episodes
Rate/ 1,000
Ratio of enteric to
total diseases
Enteric
disease
623
158
0270
Control
disease
1,681
426
—
2 years of
effluent irrigation
Enteric
disease
789
200
0257
Control
disease
2,286
579
—
"Total population of the 11 kibbutzim is 3,949
-------
H. I. Shuval and B. Fattal 233
numbers for all 11 kibbutzim for the effluent irrigation years and the
noneffluent irrigation years. According to the null hypothesis, the sum of
the ranked numbers should be equal to 55 (that is, u_*02 = 55) for each
category. Table 5 summarizes this form of analysis and shows that only
in the age group 0 to 4 years is there an apparent excess of enteric
disease for effluent irrigation years.
Table 4. Ratio of Enteric to Total Disease Incidence for Various Age
Groups in Effluent-Irrigation Years and Noneffluent-lrrigation
Years During The Irrigation Season Particular to Each Kibbutz
(Switched Category)
(First and Second Year Respectively)
Age group (years)
All ages 18+ 5-18 0-4
Non- Non- Non- Non-
Effluent- effluent- Effluent- effluent- Effluent- effluent- Effluent- effluent-
Kibbutz irrigation irrigation irrigation irrigation irrigation irrigation irrigation irrigation
Code number Year years years years years years years years years
1
2
3
5
6
7
8
10
11
13
14
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
.28
.15
.21
.65
.15
.15
.63
.33
.06
.09
.33
.42
.25
.52
.47
.27
.08
.40
.23
.32
.47
.22
.40
.17
.21
.38
.29
.06
.16
.60
.23
.40
.31
.24
.54
.83
.25
.18
.07
.09
.19
.24
.29
.36
.36
.27
.67
.82
.40
.33
.20
.21
.03
.02
.36
.32
.33
.67
.53
.35
.04
.28
.13
.41
0
.08
.33
0"
.33
.57
.33
.20
.33
.44
.22
.33
.09
.13
.08
.67
.42
.40
0
13
.38
.16
.40
0
.21
.20
.06
.71
.06
.07
0
0
0
.04
.37
.42
0
.10
.22
.17
.06
.33
.23
.30
.33
0
.50
.23
.13
.13
.40
.11
.02
.06
.16
32
33
.22
0
.67
.13
.10
.09
10
.07
.32
0
0
30
.06
.17
.56
0
.17
.71
.40
.13
.21
.30
.46
.60
0
.53
.29
.17
.52
.43
.30
0
0
.37
.15
.24
.37
0
0
.28
.78
.25
.48
.33
.28
.60
.93
.13
.11
.07
0
.10
0
0
.78
"Where zero is indicated, a ratio could not be calculated because one of the numbers was zero
Stage II: Effluent-irrigating versus noneffluent-irrigating kibbutzim
This primary analysis covers only 23 kibbutzim with a total population
of 9,148. Of these, 12 kibbutzim were effluent-irrigating and had a popu-
lation of 4,963 and 11 were noneffluent-irrigating with a population of
4,185.
The results of the preliminary analysis of incidence is presented in
Tables 6 through 13. In no case was there any apparent difference be-
tween effluent-irrigating and noneffluent-irrigating kibbutzim. This in-
-------
234 Wastewater Aerosols and Disease/Occupational Studies
eludes groupings by different age groups (Table 10), by proximity of
residential areas to effluent-irrigated areas (Table 11), by size of effluent-
irrigated tracts (Table 12), and by type of resident (Table 13). In most
cases the disease rates/1000 as well as ratio of enteric disease to total
disease are compared.
Table 5. Total Sum Rank Numbers Assigned to Ratios" of Enteric to
Total Disease Incidence for Various Age Groups in Effluent-
Irrigation Years and Noneffluent-lrrigation Years During the
Irrigation Season (Switched Category)
Age group (years)
All ages 18+ 5-18 0-4
Effuent-irngation years
Noneffluent-irrigation years
58
53
59
52
52
59
63
48
"Ratios are based on Table 4
Table 6. Comparison of Total Number of Individuals III One or More
Times with Enteric or Control Diseases During the Study Pe-
riod in Effluent- and Noneffluent-lrrigating Kibbutzim (Stage 2)
Type of Enteric Control Total
kibbutz diseases diseases residents"
Effluent
No 1.644 3,031 4,963
Rate* 331 610 —
Noneffluent
No. 1,691 2,699 4,185
Rate11 404 644 —
"Total residents includes ill and nonill population
"Rate/1,000 residents
Table 7. Comparison of Total Incidence of Enteric and Control Dis-
eases for Effluent- and Noneffluent-lrrigating Kibbutzim (Stage
2) (Based on Clinical Diagnosis and Lab Conformation)
Type of
kibbutz
Effluent
No.
Rate"
Ratio''
Non-effluent
No.
Rate"
Ratio'1
Enteric
diseases
3,132
631
0.23
3,730
891
0.25
Control
diseases
10,395
2,094
—
11,296
2,699
—
Total
incidence
13,527
2,725
—
15,026
3,590
—
"Rate/1,000 residents
bRatk> is quotient of incidence of enteric diseases to the total incidence
-------
H. I. Shmal and B. Fattal
235
The analysis of the age groups as shown in Table 9 indicates a similar
distribution of population in both effluent-irrigating and noneffluent-irri-
gating kibbutzim. The percentage of children in the age group 0 to 4 in
noneffluent-irrigating kibbutzim is slightly higher (4%) than the same age
group in effluent-irrigating kibbutzim.
Table 8. Comparison of Total Incidence of Enteric and Control Dis-
eases for Effluent- and Noneffluent-irrigating Kibbutzim (Stage
2) (Based on Positive Laboratory Results Only)
Type of
kibbutz
Effluent
No
Rate"
Ratio*
Non-effluent
No
Rate
Ratio1'
Enteric
diseases
890
179
041
796
190
048
Control
diseases
1,291
260
—
867
207
—
Total positive
incidence
2,181
439
—
1,663
397
—
"Rate/1,000 residents
''Ratio is quotient of incidence of enteric diseases to the total incidence
Table 9. Age Distribution in Effluent- and Noneffluent-lrrigation Kibbut-
zim (Stage 2)
Type of Kibbutz
Age group (years)
0-4
5-9
10-18
Unknown
Effluent
No
%
Noneffluent
No.
398
80
489
11 7
511
10.3
416
9.9
727
146
523
125
3,193
64.3
2,536
606
134
28
221
5.3
Table 10. Comparison of Total Incidence of Enteric and Control Dis-
eases for Various Age Groups In Effluent- and Noneffluent-
irrigating Kibbutzim (Stage 2)
Type of kibbutz
Age groups (years)
0-4 5-9 10-18 18+
Enteric Control Enteric Control Enteric Control Enteric Control
Effluent
No.
Rate-
Ratio''
Noneffluent
No
Rate-
Ratio1'
1,004
2,522
0.25
1,497
3,061
0.25
2,978
7,482
—
4,399
8,995
—
355
694
016
354
850
0.16
1,912
3,741
—
1,936
4,653
—
311
427
016
369
705
020
1,618
2,225
—
1,492
2,852
—
1,389
435
0.27
1,397
550
030
3,764
1,178
—
3,248
1,280
—
"Rate/1,000 residents
''Ratios is quotient of incidence of entire diseases to the total incidence
-------
236 Wastewater Aerosols and Disease/Occupational Studies
Table 11. Comparison of Total Incidence of Enteric and Control Dis-
eases According to Distance of Effluent Irrigation Fields from
Communal Dining Halls (Stage 2)
Up to 400 m
Distance
401-800m
Enteric
Control
Enteric
Control
No
Rate"
Ratio1-
1632
902
024
5293
2927
1149
952
023
3907
3239
"Rate/1,000 residents
hRatio is quotient of incidence of enteric diseases to the total incidence
Table 12. Comparison of Total Incidence of Enteric and Control Dis-
eases According to Size of Effluent-Irrigated Tract (Stage 2)
Size of tract (ha)
Up to 5
Enteric Control
5.1-100
Enteric Control
10.1-50.0 501-1000
Enteric Control Enteric Control
1001 +
Enteric Control
No 750 2,290 434 1,393 277 875
Rate" 1,020 3,116 1,578 5,065 734 2,321
Ratio* 0.25 — 024 — 024 —
73 178 1,453 5,130
608 1,483 834 2,976
029 — 022 —
"Rate/1,000 residents
fcRatio is quotient of incidence of enteric diseases to the total incidence
Table 13. Comparison of Total Incidence of Enteric and Control Dis-
eases According to Type of Resident for Effluent- and Nonef-
fluent-lrrigating Kibbutzim (Stage 2)
Type of kibbutz
Members and
candidates
Effluent
No
Rate"
Ratio'1
Noneffluent
No
Rate"
Ratio'1
Enteric
1,354
465
026
1,324
613
028
Control
3,821
1,337
—
3,361
1,557
—
Type of resident
Children
(below 19 years)
Enteric
1,618
1,036
0.21
2,092
1,589
022
Control
6,199
3,971
—
7,265
5,520
—
Temporary
(volunteers)
Enteric
26
187
028
120
480
037
Control
66
474
—
202
808
—
Others
Included
Enteric
97
348
0.33
178
515
030
Control
200
719
—
407
1,179
"Rate/1,000 residents
''Ratio is quotient of incidence of enteric diseases to the total incidence
Discussion
The results presented here represent a preliminary analysis of only
one-third of the population under study, and it is therefore not possible
to draw any conclusions at this stage.
Among the 11 kibbutzim which switched categories from effluent irri-
-------
H. 7. Shuval and B. Fattal 237
gation to noneffluent irrigation there were generally no apparent differ-
ences in disease rates between the two periods. However, according to a
ranking procedure of analysis there seems to be some indication of
excess enteric disease incidence in the age group 0 to 4 years in effluent-
irrigating kibbutzim.
In another analytical approach that uses the binomial test for the
above kibbutzim, Pahren (7) showed a significantly higher probability of
enteric disease during the effluent irrigation season. This was true for the
overall population but not for a specific age group.
The preliminary analysis of the 23 kibbutzim did not reveal any appar-
ent differences in enteric disease incidence between those practicing
effluent irrigation and those not practicing.
Additional in-depth analysis with further breakdown is required for
the total population before any conclusions can be drawn. Even when
our analysis is complete, we must take into account the methodological
problems associated with retrospective studies of this type. For exam-
ple, in the process of conducting this study we discovered that disease
data on volunteers and temporary residents is generally not recorded.
This means that critical data is absent from this analysis. It is our feeling
that such groups of previously unexposed people are the most suscepti-
ble to change in health status and could provide critical information as to
the degree of risk associated with wastewater irrigation during short
periods of exposure.
Many of these methodological problems can be overcome in the
planned prospective study to be supported by the U.S. EPA. In that
study, special attention will be paid to the close follow-up of volunteer
groups, with particular emphasis on determination of whether such
groups display immunological susceptibility even though they do not
show signs of clinical disease.
Acknowledgement
This study was financed by the U.S. EPA, Grant Number R-805174.
Mr. Herbert Pahren, Project Officer (HERL-EPA) has provided valua-
ble advice and guidance throughout the study period. Much useful ad-
vice was also given by Mr. Walter Jakubowski (HERL-EPA). Professor
Michael Davies of The Hebrew University-Hadassah Medical School
provided continuing guidance on questions of epidemiological meth-
odology. Thanks must also be expressed to Mr. Jerachmiel Applebaum
for his effective supervision of the field work and to Mr. Freddie Bor-
ensztajn and Mr. Mario Barras for the statistical analysis. Without the
willing and enthusiastic cooperation of several hundred kibbutz mem-
bers, including managers, nurses, and doctors, this complex field study
could not have been carried out. Their active participation is
appreciated.
References
1. Hickey, J. L. S., and P. C. Reis. 1975. Health significance of airborne microorganisms
from wastewater treatment processes. Part II: Health significance and alternatives for
action. Jour. Water Poll. ControlFed., 47:2741-2773.
2. Clark, C. S., A. B. Bjornson, G. M. Schiff, J. P. Phair, G. L. Van Meer, and P. S.
Gartside. 1977. Sewage workers' syndrome. Lancet, 1:1009.
3. Adams, A. P., and J. C. Spendlove. 1970. Coliform aerosols emitted by sewage treat-
ment plants. Science, 169:1218-1220.
-------
238 Wastewater Aerosols and Disease/Occupational Studies
4. Kalzenelson, E., and B. Teltsch. 1976. Dispersion of enteric bacteria by spray irrigation.
Jour. WaterPoll. ControlFed., 48:710-716.
5. Teltsch, B., and E. Katzenelson. 1978. Airborne enteric bacteria and viruses from spray
irrigation with wastewater. Appl. Environ. Microbioi, 35:290-296.
6. Katzenelson, E., I. Baium, and H. I. Shuval. 1976. Risk of communicable disease
infection associated with wastewater irrigation in agricultural settlements. Science,
195:944-946.
7. Pahren, H. 1979. Personal Communication. U.S. EPA, Health Effects Research Labo-
ratory, Cincinnati, Ohio.
DISCUSSION
DR. CLIVER: I wonder if you could tell us why you categorized
influenza as an enteric disease?
MR. FATTAL: We considered influenza as an enteric disease be-
cause it was included in the enteric disease group in the first retrospec-
tive study. However, in our study, we did not differentiate between
laboratory confirmed influenza and clinically diagnosed cases. We will
consider your point when we reanalyze our data. (As a result of the
discussion on whether or not influenza should be included among the
enteric disease group, the authors decided to omit it from their study and
to reanalyze the data accordingly. Please note that the enteric disease
data appearing in the symposium proceedings do not include influenza.
—Ed.)
DR. RYLANDER: We were impressed with the first study which
appeared in Science with regard to the higher rate of influenza in ef-
fluent-irrigating kibbutzim. In several of our studies, we have seen that it
is very difficult to distinguish between clinical findings in this type of
disease. We felt that some of these symptoms were supported by your
findings, but this did not correlate well with a number of other studies.
My question is, did you consider this?
MR. FATTAL: In reference to this question, I can only repeat what
I said to Dr. diver, and we will consider this point when reanalyzing the
data.
DR. GERBA: Is the effluent generated by the kibbutz itself or does it
come from outside sources? In other words, do they take sewage from
another community and use it?
MR. FATTAL: As far as effluent-irrigating kibbutzim are concerned,
some use their own effluent as well as outside effluents (from neighbor-
ing cities and communities) while others depend solely on their own
sources.
DR. GERBA: It would be very important to differentiate the sewage.
MR. FATTAL: Absolutely. We are aware of this, thank you, and we
will analyze the data accordingly.
DR. LUE-HING: I have difficulty with the interpretation others
have made of the Science paper argument. Do you agree with its conclu-
sions or don't you?
MR. FATTAL: As I have already stated, we have only presented
data on one-third of the kibbutzim in this study. Thus, our results are at
this point incomplete. Therefore, I do not want to comfirm or rebut the
results of the first retrospective study. I suggest that you wait until all
the data have been analyzed in depth with a detailed breakdown of each
disease, age group, etc.
-------
239
Health Effects of Occupational Exposure to
Wastewater
C.S. Clark, G.L. Van Meer, C.C. Linnemann, Jr.,
A.B. Bjornson, P.S. Gartside, G.M. Schiff, S.E. Trimble,
D. Alexander, E.J. Cleary
University of Cincinnati Medical Center
Cincinnati, Ohio
J.P. Phair
Northwestern University Medical School
Chicago, Illinois
ABSTRACT
The primary objective of this research was to determine the health effects, if any, asso-
ciated with occupational exposure to biological agents present in municipal wastewater
An additional objective was to determine the sensitivity of our methodology for detecting
potential health impacts of other wastewater exposures such as recreational contact with
surface-water receiving wastewater effluents.
The procedure was a prospective seroepidemiologic study applied to municipal waste-
water workers and controls in three metropolitan areas: Cincinnati, Ohio; Chicago, Illi-
nois; and Memphis, Tennessee. The study group consisted of more than 100 workers, who
were recruited at the time they began work at activated sludge plants, and who remained in
the study for a minimum of 12 months. In addition, in Cincinnati, two other wastewater-
exposed groups were included: approximately 50 sewer maintenance workers and 50
primary wastewater treatment plant workers. The latter group was recruited into the study
just before the start-up of plant improvements that included activated sludge facilities
The purpose of including this group was to differentiate between exposure to wastewater
through aerosols and exposure to wastewater through primary wastewater treatment
operations.
Exposure categories were developed for all workers in both the aerosol and wastewater
groups. These categories were based on job observations by field personnel, on the results
of aerosol sampling and analyses for bacteria, and on concurrent wastewater sampling and
analyses for bacteria and viruses.
Our study failed to demonstrate an increased risk of infection in wastewater workers.
There was no consistent evidence of increased parasitic, bacterial, or viral infections as
indicated by stool examinations, cultures, or antibody surveys. Liver function tests and
immunoglobulin determinations also failed to show clinically significant or consistent ab-
normalities in the study groups. We did observe an increased level of minor gastrointes-
tinal illness in the inexperienced sewage-exposed workers as compared to the experienced
workers and controls. These illnesses occurred most often in the second quarter of the
year and did not correspond to enteroviral infections. Continuing studies will attempt to
identify the cause of these illnesses.
-------
240 Wastewater Aerosols and Disease/Occupational Studies
OBJECTIVES AND STUDY DESIGN*
Exposure to wastewater has long been regarded as a potential health
risk because of the wide variety of biological and chemical contituents
commonly present in wastewater. Few studies are available, however,
which document actual health risks of exposure to wastewater collec-
tion and treatment systems. During the years 1975 to 1979, the Univer-
sity of Cincinnati Medical Center conducted a comprehensive study of
wastewater treatment industry workers. This U.S. EPA-supported
study was a prospective seroepidemiologic investigation of wastewater
workers in three cities. The focus of the study was on possible health
hazards due to the viral and bacterial content of the wastewater. Physi-
cal and chemical hazards were not specifically included in the design of
this study. However, wastewater industry workers are known to experi-
ence very high accident rates (1). Exposure to toxic chemicals is docu-
mented in two other papers presented at this symposium (2,3).
When the study was initiated in 1975, there were two primary
objectives:
• to assess the health risk of occupational exposure to wastewater
• to determine the sensitivity of the serologic-epidemiologic method
to detect effects of wastewater exposure.
In 1976, there was an increased interest in whether aerosols generated at
wastewater treatment plants were a source of disease to surrounding
neighborhoods. In order to gain some information regarding potential
effects of aerosol exposure, our study was expanded in July 1976 by the
addition of a third objective:
• to assess the health risk of occupational exposure to viable waste-
water treatment plant aerosols.
At about the same time, the U.S. EPA initiated several other studies
directed towards assessing the potential health impact of wastewater
treatment on neighborhoods adjacent to treatment plants (4,5,6,7). The
study method (Figure 1) involved collection of blood specimens and
throat and rectal swabs every three months (Figure 2) for laboratory
analyses, annual health examinations, environmental monitoring (Figure
3), and collection of illness information. The central feature of the labo-
ratory studies was a battery of tests used to determine the levels of viral
1 Sero-survey (Viral and bacterial)
2 Evaluation of immune status
3 Isolation and identification of pathogens
4 Clinical illness monitoring
5 Yearly health examinations
6 Environmental monitoring
Figure 1. Method of Serologic—Epidemiologic Study
'Presented by C Scott Chirk
-------
C. S. Clark, et. al 241
and bacterial antibodies and immunoglobulins in serum specimens. The
testing was designed to detect changes that may occur after a person is
exposed to waste water in an occupational setting.
The specific objectives of the study were as follows:
• to determine whether wastewater workers develop specific bacter-
ial, viral, and parasitic infections due to occupational exposure to
sewage
• to determine the immunologic response among workers presumed
to be exposed to a high level of antigenic stimulation, i.e.,
wastewaters
• to determine whether wastewater workers serve as a reservoir of
certain infections and, if so, whether members of the workers'
families are affected
• to determine the effect of exposure to aerosols generated by the
activated sludge treatment process
• to determine the concentration of bacterial aerosols at wastewater
treatment plants.
Volunteers in the study were asked to participate for a minimum of 12
months, if possible.
Blood (45 ml)
Throat swabs"
Rectal swabs"
Urine*
Stool"
"Also collected at times of illness
''During first 15 months of study in Cincinnati only
Figure 2. Biological Specimens Collected Quarterly from Study
Participants
Sample type
Wastewater
24-hour composite
Grab
Air
Locations
Primary and
secondary
effluent
Primary and
secondary
effluent
Various locations
Determinations
Enteroviruses
Standard plate count,
total and fecal coliforms,
fecal streptococcus
Standard plate count,
total and fecal coliforms,
fecal streptococcus
Figure 3. Environmental Monitoring
-------
242 Wastewater Aerosols and Disease/Occupational Studies
Related Studies
Recent literature searches have revealed little evidence of occupa-
tional health problems associated with wastewater pathogens (8,9). The
few situations in which adverse health effects have been found involved
sewage farming with untreated wastes or other contact with essentially
raw sewage (10,11,12). A comprehensive retrospective study of Berlin
sewer workers by Anders failed to reveal any health problems asso-
ciated with sewage pathogens (13).
In Sweden, Rylander and his associates describe what they call a
"sewage workers syndrome," found in workers in a sludge-drying oper-
ation producing dust mostly in the respirable size range (14). Symptoms
of this syndrome include eye discharges and fever which usually de-
velop several hours after the end of the work day. Laboratory testing
revealed elevated levels of the immunoglobulin IgA and elevated levels
of white blood cells. Their investigation has been extended to other
wastewater treatment plants; results from these studies appear else-
where in the proceedings of this symposium (15). Layton has reported
that new employees in the wastewater industry sometimes experience
dysentery during the first year of employment but appear to have no
unusual ill effects thereafter (16). A preliminary report of a study of
wastewater treatment workers in Copenhagen, Denmark, suggests that
the workers experience elevated immunoglobulin levels and elevated
levels of antibodies against Weil's disease (17). Dean (18) reports on
other aspects of the Copenhagen study elsewhere in this symposium.
Earlier studies in Germany (12) and Ceylon (11) also report elevated
levels of antibodies against Weil's disease. Weil's disease can be trans-
mitted by the urine of infected rats and may resemble influenza in its
earlier stage.
Populations Selected
The populations selected for the initial portion of the study were
Cincinnati sewer maintenance workers; Cincinnati highway mainte-
nance workers served as the comparison group. The protocol required
recruiting a minimum of 30 inexperienced sewer maintenance workers
just as they were starting work, 30 experienced sewer maintenance
workers, and comparable groups of highway maintenance workers.
Sewer maintenance workers were thought to have more intimate contact
with sewage in Cincinnati then sewage treatment plant workers. Soon
after the study began in 1975, a moratorium on municipal employee
hiring in Cincinnati made recruitment of highway maintenance workers
who just starting work impossible, and it severely impeded recruitment
of inexperienced sewer maintenance workers, although some hiring con-
tinued for this work group. When the study was expanded in mid-1976 to
determine the potential occupational health effects of exposure to acti-
vated sludge plant aerosols, the research design was expanded to in-
clude two additional exposed population groups. These groups were: 1)
50 men employed at the Cincinnati Mill Creek Sewage Treatment Plant,
which was in the process of being expanded from primary wastewater
treatment to include the activated sludge process; and 2) 100 men newly
employed at activated sludge treatment plants. The latter group was
-------
C. S. Clark, et. al 243
recruited from Cincinnati, Ohio; Chicago, Illinois; and Memphis, Ten-
nessee. As additional control groups, water treatment plant workers
were selected in Chicago; in Memphis, workers at the Memphis Light,
Gas and Water Division were selected. Chicago was chosen because the
large size and long history of the Metropolitan Sanitary District of
Greater Chicago provided a relatively large number of inexperienced
workers as a result of routine work-force attrition. Memphis was chosen
because its second treatment plant was almost completed and the em-
ployees expected to be hired would be primarily those without any prior
occupational exposure to wastewater.
Initial recruitment began in April 1975 when the first inexperienced
sewer maintenance workers in Cincinnati joined the study. Chicago
workers joined the study in July 1976 and Memphis workers in 1977,
since that was the time when initial hiring began at the newly-completed
Memphis North Wastewater Treatment Plant. A listing of the dates of
initial recruitment of all study groups appears in Figure 4. Volunteer
recruitment was completed by the first quarter of 1978, and the last
specimens were collected during the final months of that year. The total
number of volunteers recruited in the various work groups is shown in
Table 1. Over 500 workers participated in the study, but not all workers
remained in the study for the entire period. Family members of study
participants were invited to participate in a family study designed to
determine if wastewater workers served as a source of infection for
their families. Single blood specimens were collected from individuals
participating in the study. A summary of the 128 families and number of
specimens collected is presented in Table 2.
Table 1. Number of Volunteers Recruited Into Study
Group Cincinnati Chicago Memphis
Inexperienced Activated Sludge
Experienced Activated Sludge
Inexperienced Sewer Maintenance
Experienced Sewer Maintenance
Controls
44
54
13
65
80
256
56
40
0
0
50
146
50
17
0
0
55
122
Table 2. Family Study0
Number of Families
Worker group Cincinnati Chicago Memphis Total
Inexperienced Sewage Exposed
Experienced Sewage Treatment
Control
Total No Families
13
241.
12
49
13
19
11
43
16
2
18
36
42
45
41
128
"Total numbers of specimens collected from household members in Cincinnati, Chicago, and Memphis
were 170,130, and 129, respectively
includes 9 families of sewer maintenance employees with total of 31 specimens
-------
244 Wastewater Aerosols and Disease/Occupational Studies
April 1975 Inexperienced sewer maintenance —Cincinnati
July 1975 Inexperienced sewage treatment —Cincinnati
July 1975 Sewer and highway maintenance —Cincinnati
July 1976 Experienced sewage treatment —Cincinnati and Chicago
July 1976 Inexperienced sewage treatment —Chicago
October 1976 Water treatment —Chicago
July 1977 Sewage treatment —Memphis
October 1977 Light, gas and water — Memphis
Figure 4. Date of Initiation of Recruitment
ENVIRONMENTAL MONITORING, STATISTICAL
PROCEDURES, AND POPULATION CHARACTERISTICS*
Environmental Monitoring
The environmental monitoring consisted of aerosol sampling at var-
ious worksites for respirable concentrations of bacteria, and wastewater
sampling for viruses and bacteria (Figure 3). The virus assay of waste-
water in all three cities was performed by the Metropolitan Sanitary
District of Greater Chicago. Six-liter, twenty-four-hour composite sam-
ples for virus assay were concentrated using an Al(OH)3-continuous
flow centrifuge technique (19). Virus content was estimated by using a
plaque assay procedure that used three cell cultures: 1) BGM (Buffalo
green monkey kidney cells; 2) WT-38 (human diploid cell strain); and 3)
PMK (primary monkey kidney cells). The aerosol samples were col-
lected using six-stage, viable-particle Andersen samplers, and were ana-
lyzed for fecal streptococci (FS), fecal coliform (FC), total coliform
(TC), and standard plate count (SPC). The samplers were used to collect
the aerosols from about 0.4 m3 of air (20). Each sampler contained six
molded Andersen glass petri dishes containing 27 ml of plate count agar.
A replicate plate method was used for determining the total coliform
(TC), fecal coliform (FC), and fecal streptococcus (FS) counts on the
petri dishes from the Andersen samplers. Bacterial analyses of waste-
water and aerosols were performed in Chicago by the Metropolitan
Sanitary District of Greater Chicago; in Memphis by the Memphis State
University; and in Cincinnati by our staff. Bacterial analyses were per-
formed according to "Standard Methods" (21). Results of the air sam-
pling were used to determine relative levels of airborne bacteria at var-
ious worksites. Based on this information, each worker was categorized
according to his exposure level relative to other workers at the same
treatment plant. The exposure categories were "above average" and
"average or below average". Wastewater and sludge exposure levels
were determined by a combination of survey questionnaire and job ob-
servation by field personnel. Again, exposure categories were either
"above average" or "average or below average".
After each group of workers was subdivided into exposure categories,
clinical and laboratory findings were examined to see whether there was
any variation within a worker group as a result of exposure level.
Tables 3, 4, and 5 summarize airborne bacterial levels for Cincinnati,
Chicago, and Memphis, respectively. Results are based on plate counts
for stages 3 through 6 of the Andersen samplers.
*Presented by Gretchen L Van Meer
-------
C. S. Clark, et. al
245
Table 3. Environmental Monitoring - Aerosol Respirable Bacterial
Count/m3 - Cincinnati
No Standard
samples plate count
Total Fecal Fecal
coliform coliform streptococci
Mill Creek Sewage Treatment Plant
Inside - no wastewater
Inside - wastewater operations
Aeration basins
Settling tanks
Other outdoor
Seiver maintenance
Inside
Outside
Highway maintenance
Inside
Outside
Street cleaning
5
17"
17»-
5
22
5
1
11
g
2
43
761
812
280
320
374
16
93
9
1,121
0
20
8
7
6
0
0
0
0
15
0
4
1
0
2
0
0
0
0
1
0
10
2
1
3
0
0
0
0
15
"One sample too numerous to count
bTwo samples too numerous to count
Table 4. Environmental Monitoring - Aerosol Respirable Bacterial
Count/m3 - Chicago
West Southwest Sewage
Treatment Plant
Inside
Aeration basins
Aerated grit chamber
Other outdoor
No
samples
7
11
1
10
Standard
plate count
973
253
315
196
Total
coliform
18
13
33
23
Calumet Sewage Treatment Plant
Aeration basins
Aerated grit chamber
Other outdoor
Water treatment plant
11
2
10
8
292
368
212
38
4
30
0
8
Fecal
coliform
6
6
0
6
3
16
0
2
Fecal
streptococci
10
2
12
9
2
30
0
2
Table 5. Environmental Monitoring - Aerosol Respirable Bacterial
Count/m3 - Memphis
No
samples
North Sewage Treatment Plant
Inside - no wastewater
Aeration basins
Aerated grit chamber
Other outdoor
Maxson Sewage Treatment Plant
Aeration basins
Aerated grit chamber
Other outdoor
7
25
10
12
11
3
6
Standard
plate count
73
735
522
150
583
326
184
Total
coliform
7
43
42
27
68
177
13
Fecal
coliform
5
12
29
3
45
91
4
Fecal
streptococci
8
55
30
4
66
343
30
-------
246 Wastewater Aerosols and Disease/Occupational Studies
Statistical Procedures
Statistical procedures used primarily included analyses of covariance,
where the data are continuous, and the chi-square test, where the data
are discrete.
Examples of analyses of covariance are given in Tables 6 and 7 for
liver function tests and immunoglobulins, respectively, for Chicago
workers in 1978. The data were examined for distribution, and when it
was not normal, a transform was used. For all the data in this study
which were not normally distributed, a log transform was sufficient. This
was done for three of the five liver function tests and for all the immu-
noglobulins tested.
Table 6. Yearly Health Exam - Liver Function Tests - Chicago 1979
Inexperienced
SCOT" 29 1
SGPT" 139
Albumin 4 6
Alkaline phosphatase- 73 7
Total bilirubin 58
Mean Values
Experienced
271
137
44
71 5
59
Controls
240
12 1
44
647
69
P"
022
221
882
090
070
"Geometric mean
fcBy analysis of covariance, with age and race covanates
Table 7. Immunoglobulin Levels (mg/d1) Chicago
Geometric Means
1/78
10/78
IgA
igG
IgM
IgA
IgG
IgM
Experienced
189 (SO)11
1,200
83
1 72 (44)
1,119
74
Control
191 (31)
1,200
81
179 (30)
1,153
72
Significance"
252
546
904
546
.781
736
Significance
Age
030
721
149
021
727
873
Race
001
< 001
489
.024
146
232
"By analysis of covariance
^Number of persons
Covariates used were age and race, and significance levels provided in
the tables reflect this adjustment.
The virus serology procedure consisted of serial dilutions, and the
data consisted of the highest dilution level for each worker for which
antibody was found. An example of a contingency table of this kind of
data is Table 8, which shows results for Chicago sera analyzed for
antibody to Polio 3 in January, 1978. The chi-square test was used to
ascertain whether there was a significant difference in the distribution of
liter levels. If a difference existed, it was not always obvious which
group had the higher average liter level. Occasionally, the dislribulional
difference might have been a result of higher and lower liters in one
group and medium tilers in Ihe other. In order lo facililale interprelalion
of the results, the geomelric mean liter level is given for each group. To
-------
C. S. Clark, et. al 247
calculate the geometric mean for values below detection level, which
was less than 2 in this test, half the detection level was arbitrarily used,
that is, 1, in this case.
In addition to the question of differences in distribution of tilers be-
tween groups, the question arises as to whether there were differences
between groups in liter level changes from one time period to another.
An example of a conlingency lable of Ihis lype of dala is given in Ihe
second pan of Table 8. Of particular inleresl are increases of fourfold or
grealer (Iwo or more liter levels) because of Iheir potential medical
significance. However, the chi-square tesl, which was used for Ihe en-
tire contingency table, includes all changes.
Table 8. Virus Serology—Chicago—Antibodies to Polio 3
Titer Levels
Geometric
'-2248 16 32 64 _^128 N mean P"
1 /78 Experienced
1 /78 Control
2
2
2
3
3
2
5
3
9
4
6
4
8
3
9
3
44
24
234
1388
898
Titer level changes January-October 1978
Increases
Experienced
Control
3
0
1
2
1
2
1
6
6
No change
0
27
9
Decreases
1
6
4
2
3
1
3
0
0
N
43
23
P"
283
"By chi-square
Similar procedures were used to evaluate the differences between
high and low-to-medium exposed workers for both aerosols and waste-
water, and for differences thai were a resull of age or race, as indicaled
in Table 9. The data are for the same group of exposed workers shown in
Table 8. In Table 9 this group is divided on the basis of aerosol exposure
in the firsl part, wastewater in Ihe second parl, age in Ihe Ihird parl, and
race in Ihe fourth part. Again, the geometric mean liler levels are in-
cluded lo facilitale inlerprelation of the results.
In the examples given in Tables 6 through 9 there were no significant
differences (p < .01). However, Ihese same procedures were initially
used for 31 viruses in six worker groups for three time periods in two
cities. Wilh this quantily of comparisons, by Ihe laws of probabilily,
resulls will be significanl 1% of the time, and il is essenlial to guard
against Type II errors (false positives). It is possible in some situations
to adjust Ihe significance value, for example, by multiplying by the
number of tesls done. However, in a sludy of Ihis size Ihere is also the
risk of suppressing genuine differences. The best method of evalualion
in a case like Ihis is lo inspecl all differences lhal appear lo be significanl
-------
248 Wastewater Aerosols and Disease/Occupational Studies
in order to see whether there is any apparent trend or whether these
outcomes are random and within the limits of the expected number of
significant differences in a study of this size. Summaries of significant
differences for virus serology are given in the results section of this
paper.
Table 9. Virus Serology—Chicago - January 1978 Antibodies to Polio 3 -
Exposed Workers
liter Levels
Aerosol exposure
High
Low-Med
Wastewater Exposure
High
Low-Med
Age
^.40
>40
Race
Black
White
<2
2
0
1
1
1
1
0
2
2
0
2
1
1
1
1
1
1
4
1
2
1
2
1
2
0
3
8
2
3
2
3
4
1
2
3
16
3
7
5
5
7
3
1
9
32
2
4
2
4
3
3
1
5
64
3
4
5
2
5
2
2
5
^.128
7
2
9
5
3
6
2
7
N
20
24
21
23
25
19
9
35
Geometric
mean
288
18.5
246
21 0
205
257
25.4
22.0
P°
228
936
624
.525
"By chi-square
Population Characteristics
In a study consisting of volunteer subjects, the question arises as to
whether those who participated differ appreciably from those who quali-
fied and were invited, but chose not to participate. While the informa-
tion available on the nonparticipants is more limited than on the volun-
teers, data for a number of parameters were collected, namely, age,
race, salary, job class, and, in some cases, years of school (Figure 5).
For each parameter in each worker group, the participants were com-
pared with the nonparticipants. Data were put in contingency tables;
5-year groupings were established for age, and $2,000-$2,500 increments
were established for salary. Comparisons were performed using the chi-
square test. Table 10 shows the number of workers used in each group,
the mean values and range for age, the mean values for years of school,
and the median ranges for salary, along with the significance level for
each comparison. Job classification comparisons and the significance for
Type Participants Nonparticipants
Age XX
Race x x
Salary x X
Years experience X X
Household composition X
Education X
Household income X
Figure 5. Socioeconomic Data Collected
-------
C. S. Clark, et. al 249
each comparison are given in Table 11 for all 3 cities. The chi-square
procedure was used. Additional data are still being collected from non-
participants in the control groups in Chicago and Memphis. The differ-
ences that exist between participants and nonparticipants are not ex-
pected to influence study results.
More information is available for participants in the study; this infor-
mation can be used to ascertain comparability of the exposed and con-
trol groups with regard to socioeconomic status (SES). Available data
Table 10. SES Data Comparing Study Participants With Nonpartici-
pants
Age (years as of 1978)
Cincinnati
N
Inexperienced sewage exposed
Participant 52
Nonparticipant 24
P"
Control
Participant
Nonparticipant
P"
74
86
Mean
308
328
.507
431
387
.197
Range
19-64
21-64
22-67
21-64
N
55
68
39
96
Chicago
Mean
388
398
920
28.2
282
750
Range
19-61
19-62
22-76
22-69
N
50
62
56
81
Memphis
Mean
279
34.2
040
409
40 1
850
Range
19-57
19-63
19-67
20-70
Experienced sewer maintenance
Participant 65 40.9 24-66
Nonparticipant 13 41 2 27-63
p« .464
Experienced sewage treatment
Participant 58 378 20-63
Nonparticipant 11 428 24-62
P" .154
Cincinnati
Nonwhite
Inexperienced sewage exposed
Participant 19
Nonparticipant 10
p« .821
Control
Participant
Nonparticipant
P"
52
59
500
Experienced sewer maintenance
Participant 54
Nonparticipant 4
p« .001
Experienced sewage treatment
Participant 24
Nonparticipant 3
P" .273
White
27
14
21
30
11
8
34
10
Race
Chicago Memphis
Nonwhite White Nonwhite White
14 40 10 40
12 54 12 41
.310 750
22 35
33 49
.840
"By chi-square
bBy chi-square with Yates' correction
-------
250
Wastewater Aerosols and Disease/Occupational Studies
Table 10. SES Data Comparing Study Participants With Nonpartici-
pants (Continued)
Years school
Cincinnati Chicago
Mean
N
Mean
Inexperienced sewage-exposed
Participant 51 124
Nonparticipant 24 118
ph 003
Control
Participant 64 116
Nonparticipant 86 110
P" 013
Experienced sewer maintenance
Participant 64 112
Nonparticipant 12 113
ph 791
Experienced sewage treatment
Participant 60 120
Nonparticipant 12 138
ph 047
51
59
123
124
930
Salary—median range (x $1000)
Cincinnati Chicago
Median
Memphis
N
Median
Median
Inexperienced sewage exposed
Participant 45 9 6-12 1
Nonparticipant 24 96-121
P" 372
Control
Participant 72 121-14
Nonparticipant 92 96-121
P" 002
Experienced sewer maintenance
Participant 64
Nonparticipant 12
Ph
Experienced sewage treatment
Participant 57
Nonparticipant 11
96-121
12 1-14
.067
96-121
7-96
040
52 141-16
68 161-18
025
39 96-121
65 96-121
730
48 121-14
84 121-14
140
"By chi-square
fcBy chi-square with Yates' correction
also include household size and household income, more meaningful
measures of SES than salary. Comparisons for these parameters are
given in Table 12 for each worker group in each city. There are signifi-
cant differences for age (p < .01) and for race (p < .05), which is why
these covariates are used in the analyses of covariance and the virus
serology data are examined for differences based on age or race. When
virus serology data were examined for age and race effect, few differ-
ences were found. These differences are not thought to influence
the results of the study. Household sizes are similar in Cincinnati and
-------
C. S. Clark, et. aJ 251
Table 11. Comparison of Participating with Nonparticipating Job Class
I
Nonpartic
Operator
Cincinnati inexperienced
sewage-exposed
Cincinnati experienced
sewage treatment
Cincinnati experienced
sewer maintenance
Cincinnati controls
15
31
15
8
6
5
28 28
Maintenance
Laborer
A
Participati
u
1
1
Laborer
19
12
38
19
15
3
5
54
Maintenance
Laborer B
I I
I 1
Other
11 2
17 6
11 2
22 10
Security
Guard
P"
084
603
413
001
Chicago inexperienced
sewage treatment
Memphis inexperienced
sewage treatment
Memphis controls
18
40
25
20
Operator/
Supervisor
24
34
Lineman
Tradesman/
Laboratory
29
Crew Leader/
Foreman
Laborer
12
10
Other
18
23
11
12
25
30
040
033
450
"By chi-square
Chicago, but in Memphis, although the means are similar, the distribu-
tion of family sizes is different. The exposed groups are somewhat bet-
ter educated than the controls, though household income is less. This
however, may be a reflection of the younger age (which is to be expected
in a group of inexperienced workers) of the individuals in this group.
CLINICAL AND LABORATORY FINDINGS*
My personal bias at the beginning of this study was that we would
easily find evidence of increased infections in workers exposed to sew-
age, although we might not find an increase in clinical illness. The pre-
liminary findings of the study, which are reported here, do not support
that opinion. Dr. Van Meer has discussed in detail some of the problems
encountered when evaluating the results of an epidemiologic survey of
this type, in contrast to a study which focuses on a more limited ques-
tion. Therefore, in the presentation of the results, I will indicate the
number of comparisons made in various aspects of the study, and the
trends of the differences observed. In addition, I will attempt to indicate
*Presented by Calvin C. Linnemann
-------
252
Wastewater Aerosols and Disease/Occupational Studies
the clinical significance. The correlation of the environmental sampling
data with clinical and laboratory findings has not been analyzed and will
not be presented. The results will be discussed in four sections: 1) clini-
cal illness; 2) laboratory tests; 3) evidence of infection; and 4) the family
study.
Table 12. SES Data for Workers in Final Virus Serology"
Cincinnati
Age (years, as of 1978)
Chicago
Memphis
N Mean Range N Mean Range N Mean Range
Inexperienced sewage
exposed
Control
Experienced sewer
maintenance
Experienced sewage
33 336 20-64 49 389 19-60 43 274 19-57
46 470 22-66 25 509 28-76 50 377 19-67
40 37 2 24-60
treatment
Inexperienced sewage
exposed
Control
Experienced sewer
maintenance
Experienced sewage
treatment
Inexperienced sewage
exposed
Control
Experienced sewer
maintenance
Experienced sewage
treatment
41 38 0 22-63
p< 001
Cincinnati
Nonwhite White
13 16
28 18
36 4
19 22
p- 001
Cincinnati
N Mean
33 36
41 38
40 34
45 37
p =- 790
p- 009 p< 001
Race
Chicago Memphis
Nonwhite White Nonwhite White
11 38 8 35
12 12 20 31
p = 019 p = 033
Household size
Chicago Memphis
N Mean N Mean
49 36 41 36
25 32 49 38
p = 791 p 025
"All procedures done using chi-square test on contingency tables of raw data; intracity comparisons
only; N = number of workers or worker's families represented
-------
C. S. dark, et. al 253
Table 12. SES Data for Workers in Final Virus Serology0 (Continued)
Years school
Cincinnati Chicago Memphis
N Mean N Mean N Mean
Inexperienced sewage
exposed
Control
Experienced sewer
maintenance
Experienced sewage
treatment
32
42
40
41
P<
125
11 5
11 1
121
.001
48 124 39 132
23 108 47 110
p = 041 p = 006
Household income - median range (x $1000)
Cincinnati Chicago Memphis
Inexperienced sewage
exposed
Control
Experienced sewer
maintenance
Experienced sewage
treatment
29
45
40
41
P =
96-12
14
12
14
100
1-16
1-14
1-16
48 14.1-16 39 96-12
24 25 45 14 1-16
p < 001 p = 002
"All procedures done using chi-square test on contingency tables of raw data; intracity comparisons
only; N = number of workers or worker's families represented
Clinical Illness
The illnesses which occurred in the study populations were categor-
ized as respiratory, gastrointestinal, combined respiratory and gastroin-
testinal, and other. This reflects our primary concern with respiratory
and gastrointestinal illnesses. Figure 6 and Table 13 show the occur-
rence of clinical illnesses in the combined study groups. The number of
illnesses is expressed per 100 worker-months of exposure. This was
necessary because of variations in duration of the workers' participation
in the study. The illness rates are presented quarterly in order to allow
interpretation of seasonal patterns. Total illnesses, which peaked in the
first or winter quarter, reflected the increase in respiratory illnesses.
There were no major variations in the other illness categories. Upon
examination of clinical illnesses by worker groups (Table 14) we find
that respiratory illnesses are the most common illnesses in all groups;
the highest total illness rates occur among the inexperienced and experi-
enced treatment workers. The only statistically significant difference in
illness rates between worker groups and/or controls was the difference
in gastrointestinal illness among inexperienced workers and in other
groups. This is illustrated in Figure 7, and, as can be seen, the difference
is greatest in the second quarter of the year. These were minor gastroin-
testinal illnesses and did not appear to correspond with enteroviral
infections.
-------
254
Wastewater Aerosols and Disease/Occupational Studies
16
14
12
o
I 10
8
S.
M
€>
<0
CO
«
c
•5 6
E
2 4
Total
Respiratory
1 2 3
Quarter of the Year
Figure 6. Clinical Illnesses in All Study Participants, Including Waste-
water Workers and Controls
-------
C. S. Clark, et. al
255
Table 13. Clinical Illness in All Study Participants, Including Waste-
water Workers and Controls
Type of illness"
Quarter of Year Respiratory
January-March 8 7
April-June 5 9
July-September 5 4
October-December 4 9
Gastrointestinal
22
27
22
1 6
Respiratory and
Gastrointestinal
1 3
06
08
1 4
Other
37
44
39
28
Total
159
136
124
108
"Per 100 worker-months of exposure
Table 14. Clinical Illness in Wastewater Worker Groups
Type of illness"
Respiratory and
Worker
Inexperienced
Experienced
Maintenance
Treatment
Control
Respiratory
65
5.5
80
4.9
Gastrointestinal
36
1 3
24
1 5
Gastrointestinal
1 7
05
09
1 0
Other
38
40
36
33
Total
156
11 3
149
107
"Per 100 worker-months of exposure
Laboratory Tests
As indicated by Dr. Clark, a variety of laboratory tests were per-
formed on each worker, including complete blood counts, urinalysis,
blood chemistries, and tests of immunoglobulin levels. We were particu-
larly interested in liver function tests because of the possibility of hepa-
titis. Table 15 shows the geometric mean values for the SCOT and SGPT
for each worker group in each city by study year. It is apparent that the
means for all groups are within normal limits. The mean SGOT is
slightly higher for the experienced sewer maintenance workers in Cin-
cinnati, but the SGPT in the experienced sewer maintenance worker
group is lower than in the unexperienced worker group. The SGPT is an
enzyme which is more specific for liver than is the SGOT. None of these
differences between the groups was significant at p < .01 level. The
results of the liver tests provided no evidence of an increase in hepatitis
in workers exposed to waste water.
Immunoglobulin levels were determined because other studies of
wastewater workers have reported higher levels of immunoglobulins,
although the reported differences are not statistically significant. Theo-
retically, continuing antigenic stimulation from wastewater could pro-
duce elevated immunoglobulin levels. In the present study, immuno-
globulin levels were measured in inexperienced workers at the initial
time of employment and compared to the levels three months later. As
shown in Table 16, there were no significant differences. Immunoglob-
ulin levels of study groups were also compared at intervals throughout
the study period. The values for one of the three cities are shown in
Table 17. This is typical of all cities; there were no consistent differences
between study groups. Year to year variations could not be compared,
-------
256 Wastewater Aerosols and Disease/Occupational Studies
Table 15. Results of Liver Function Tests in Each Study Group, by City
Geometric mean values by worker group
Year
Test
Inexperienced Experienced Experienced
sewer- sewer sewer
exposed maintenance treatment Control
Cincinnati
Chicago
Memphis
1976
1977
1978
1977
1978
1977
1978
SCOT
SGOT
SGPT
SGOT
SGPT
SGOT
SGOT
SGPT
SGOT
SGPT
SGOT
SGPT
255
27 1
279
233
21 1
282
29 1
139
271
150
19 1
180
325
352
182
303
203
236
266
175
238
195
238
27 1
137
255
266
205
277
203
260
240
12 1
243
121
175
137
since tests were not done simultaneously. However, the first and last
sera from one group of inexperienced workers were measured simulta-
neously and there was no change in immunoglobulin levels. Therefore,
the study failed to demonstrate increased or changed immunoglobulin
levels in wastewater workers.
1=5
I
0>
-------
C. S. Clark, et. al 257
EVIDENCE OF INFECTION
Parasitic
To evaluate the frequency of parasitic infection in sewer maintenance
workers, a prevalence survey was conducted in the first year of the
study. Stool specimens were collected from 136 men, including 69 con-
trols, 19 new employees who had not been exposed to sewage, and 48
experienced maintenance workers (Table 18). Parasites were found in
11.6% of the controls and in 10.5% of the new employees but in none of
the sewage-exposed workers. An additional 196 stool examinations were
performed over the following year, but the identification of parasites
was similar in the sewage-exposed and nonexposed workers. There was
no evidence of increased parasitic infection in the wastewater workers.
Table 16. Immunoglobulin Levels in Inexperienced Wastewater
Workers"
Cincinnati Chicago Memphis
Type
IgG
IgM
IgA
First
serum
1,954
83
176
Second
serum
1,804
82
171
First
serum
2,461
94
196
Second
serum
2,065
96
192
First
serum
1,113
83
183
Second
serum
900
110
193
"Mean values, mg/d1
Table 17. Immunoglobulin Levels by Wastewater Worker Group in
Cincinnati
Year of
study
1975
1976
1978
Worker
group
Experienced sewer maintenance
Control
Experienced sewer maintenance
Experienced sewage treatment
Control
Experienced sewer maintenance
Experienced sewage treatment
Inexperienced sewage-exposed
Control
Immunoglobulin level"
igG
2,176
2,857
2,183
2,486
2,537
1,451
1,188
1,636
1,451
IgM
126
95
689
78
69
84
74
84
73
IgA
327
281
268
183
233
179
167
156
226
"Mean values, mq/d1 _ . .
Bacterial
Rectal swabs were obtained from workers and controls, and cultured
for Salmonella and Shigella. The results of these cultures are summa-
rized in Table 19. Salmonella were isolated from six of 206 workers
exposed to sewage, and Shigella were isolated from one of 171 controls.
This is not a significant difference.
Antibody liters were measured for Salmonella, Leptospira, and Legi-
onella pneumophila serotype 1. There were no differences in Salmonella
antibody in limited studies in the first 3 years of the study. In the final
year, sera from all men were tested by a microagglutination technique
for antibodies to Salmonella groups A through E. Forty-five compari-
sons were made between groups of workers and controls. This included
-------
258 Wastewater Aerosols and Disease/Occupational Studies
comparisons of antibody levels in sera collected from each man in Janu-
ary and October and of seroconversion between the two sera. These
three comparisons were repeated for the five Salmonella groups in each
of the three cities in the study. In 45 comparisons there were no differ-
ences between groups which were significant at the p < .01 level. There
were only four differences which were significant at the p < .05 level.
Table 18. Prevalence of Parasites in Stools by Worker Group in
Cincinnati
Worker
Group
Nonexposed
Controls
New employees
Exposed
Sewer maintenance
Total
No of
Workers
69
19
48
136
Positive
Stool (%)
8 (116)
2 (105)
0
10 (74)
Parasite
(No of workers)
Giardia
E nana
Isospora
Giardia
Strongyloides
—
(D
(5)
(2)
(1)
(1)
Table 19. Salmonella and Shigella Isolations from Rectal Swabs
Worker No of Positive
Group Workers Cultures %
Exposed to sewage 206 6 29
Nonexposed 171 1 06
Two prevalence surveys for antibody to Leptospira were conducted
in 1977 and 1978 (Table 20). Antibody was measured by Dr. C. Sulzer in
the Leptospirosis Reference Laboratory of the Center for Disease Con-
trol with a microscopic agglutination technique that used over 20 sero-
vars. In 1977, a survey of 124 men indicated that the prevalence of
antibody was greater in workers who were not exposed to sewage (Table
20). In 1978, an expanded survey including 357 men showed a higher
prevalence of antibody in the workers who were exposed to sewage.
The differences were not statistically significant.
In the final year of the study, a prevalence survey for antibody to
Legionella pneumophila was conducted by use of a fluorescent antibody
technique. This test was added to the study because of increasing epide-
miologic data which suggested that this was a soil organism which could
be acquired from environmental sources. The results of the survey are
shown in Table 21. Screening at a 1:64 dilution of serum, 34.4% of the
workers exposed to sewage and 35.4% of the nonexposed workers had
antibody. The level of antibody was slightly higher in sewer mainte-
nance workers compared to sewer treatment workers, but the difference
is not statistically significant.
-------
C. S. Clark, et. al 259
Table 20. Prevalence of Leptospiral Antibody
Worker Group
1977
Sewage-exposed
Nonexposed
1978
Sewage-exposed
Nonexposed
No of
Workers
57
67
225
132
No with
Antibody
7
19
11
1
%
123
284
49
08
Table 21. Prevalence of Antibody to Legionella pneumophila
Fluorescent Antibody
Worker Group
Sewage-exposed
Maintenance
Treatment
Nonexposed
Titer"
<64
179
40
139
117
S64
94
29
65
64
Positive
344
420
31 9
354
"Reciprocal of the serum dilution
Viral
The possibility of an increase in viral infections among wastewater
workers was tested by the use of throat cultures and rectal swabs for
viruses, and by use of extensive serologic surveys. Viral cultures were
performed in Rhesus monkey kidney, WI-38, Vero and HeLa cells. The
numbers and types of viruses isolated are shown in Table 22. Herpes
simplex virus was isolated most frequently and enteroviruses were the
second most common isolate. Our major concern in this study was the
occurrence of enteroviral infections because of the frequency with
which enteroviruses can be recovered from wastewater. Although more
enteroviruses were recovered from wastewater workers, the recovery
rates were not significantly different. The results for the study partici-
pants in Cincinnati are presented in Table 23. The specific enteroviruses
which were isolated from the participants are shown in Table 24 along
with those enteroviruses which were recovered from wastewater sam-
ples during the study.
Table 22. Virus Isolations from Throat and Rectal Swabs
Study
group
Wastewater
Control
Entero
15
3
Adeno
1
3
Type of Virus
Rhino
4
1
Herpes
18
12
Flu A
3
1
Total 18 4 5 30
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260 Wastewater Aerosols and Disease/Occupational Studies
Table 23. Enterovirus Isolations from Study Participants in Cincinnati
Worker
group
Exposed to sewage
Nonexposed
No of
workers
183
78
Number
excreting
enterovirus
6
2
%
33
26
Table 24. Enteroviruses Recovered During the Study
Wastewater Study
Viruses monitoring participants
Polio 1-3 1,3
Coxsackie A15,61,3-5 A13;B2,4,5
Echo 1-4,6,7,9,13,18,33 3,9,21,29
The serologic testing for viral antibodies was performed in two large
surveys. The viruses which were included in the initial survey are shown
in Table 25, and those in the final survey are shown in Table 26. Most of
these are enteroviruses, antibody was measured by a microneutraliza-
tion technique. The specific viruses were selected on the basis of recov-
ery of viruses from workers and wastewater in the study or by viral
diagnostic laboratories in the study areas. Several nonenteroviruses
were also included, and antibody was measured by complement fixation
for most of these.
Table 25. Viruses Included in Initial Virus Serology Survey
Polio 1,2,3
Coxsackie A7,9,16,21; B1-6
Echo 1-4.6,8,9, 11, 13, 14, 19,24,25,30
Adenovirus
Reovirus
Herpes simplex
Cytomegalovirus
Table 26. Viruses Included in Final Virus Serology Survey
Polio 1,2, 3
Coxsackie A9;B1-5
Echo 3, 6, 8, 9, 11, 21
Adenovirus
Herpes simplex
There were many comparisons made between the various study
groups (Tables 27 and 28). For each virus included in the survey, the
level of antibody for each quarter was tested and the increases in anti-
-------
C. S. Clark, et. al 261
body liters between quarters were compared. These comparisons must
be multiplied by the number of viruses tested and the number of cities
included in order to determine the total number of comparisons made.
Therefore, there were 310 comparisons made in the initial survey and
153 in the final survey. Randomly, one would expect one in 100 to be
significant at p < .01 and one in 20 to be significant at p < .05. The
numbers and types of observed differences are shown in Tables 27 and
28. The direction of the differences (whether or not a study or control
group had higher antibody levels of more increases in antibody) is also
listed. It is apparent from this data that the serologic surveys did not
demonstrate evidence of a marked increase in enterovirus infections in
the wastewater workers.
Table 27. Results of the Initial Viral Serosurvey
Comparisons. 310 comparisons between groups (31 viruses x 5 comparisons x 2 cities)
Differences. 12 significant at p < 05 (5 at p < 01)
A) 10 differences in level of antibody
Control group higher in 5, both a control and study group in 2, and study group in 3
B) 2 differences in changing antibody liters
Study group higher for both
Table 28. Results of the Final Viral Serosurvey
Comparisons 153 comparisons between groups (17 viruses x 3 comparisons x 3 cities)
Differences • 8 significant at p <.05 (3 at p ^ 01)
A) 7 differences in level of antibody
Control group higher in 1, both a control and study group in 2, and 2 study groups in 4
B) 1 difference in changing antibody liter
More increases in 1 study group, fewer in 2
The prevalence of antibody to Hepatitis A, as measured by radioim-
munoassay, was also determined (Table 29). The prevalence of Hepati-
tis A antibody was not increased in workers as compared to controls.
However, the number of study participants who were susceptible to
Hepatitis A at the beginning of the study was not determined. Before we
can conclude that Hepatitis A is not an occupational risk for wastewater
workers, the actual number of workers at risk in each study group, as
well as the number of infections which occurred during the study years,
must be specified.
Family Study
The final aspect of this study was a serologic survey of viral anti-
bodies in study participants and their families. The question was
whether or not workers introduced viral infections into their families. A
total of 128 families were studied, including 87 families of wastewater
workers and 41 control families. Antibody was measured for six viruses,
-------
262 Wastewater Aerosols and Disease/Occupational Studies
including Polioviruses 1, 2, and 3, Echovirus 9, Coxsackie A9, and
Hepatitis A. These were selected because of the prevalence of viruses in
wastewater and in workers, the frequency of poliovirus antibody ex-
pected in immunized children, and our interest in the possibility that
Hepatitis A may be acquired by exposure to wastewater.
If the wastewater workers were being infected at work and introduc-
ing infection into their homes, then we would expect the antibody prev-
alence or antibody level to be higher in workers as compared to other
members of their families and higher in family members of workers as
compared to family members of controls. However, the serologic sur-
vey showed no significant differences between the various groups.
Table 29. Prevalence of Hepatitis A Antibody as Measured by
Radioimmunoassay
Worker No. of
group workers
Inexperienced sewer maintenance 1 2
Experienced sewer maintenance 60
Inexperienced sewage treatment 1 40
Experienced sewage treatment 1 08
Controls 177
Number with Hepatitis
A antibody
7
40
42
50
102
%
58.3
667
300
46.3
57.6
Summary
This preliminary report of the results of our study failed to show an
increased risk of infection among wastewater workers. There was no
consistent evidence of increased parasitic, bacterial, or viral infections
as indicated by stool examinations, cultures, or antibody surveys. Liver
function tests and immunoglobulin determinations also failed to show
clinically significant or consistent abnormalities in the study groups. We
did observe an increase in minor gastrointestinal illness among inexperi-
enced sewage-exposed workers as compared to experienced workers
and controls. These illnesses occurred most often in the second quarter
of the year and did not correspond to enteroviral infections. Continuing
studies will attempt to identify the cause of these illnesses.
The complete data on which these conclusions are based will be avail-
able in the final report to the Environmental Protection Agency.
References
1. WPCF Safety Committee and Staff Report. 1971. Wastewater collection and treatment
facilities—1970. Personnel safety survey. Jour. Water Poll. Control Fed., 43:335-337.
2. Kominsky, J., and M. Singal. 1979. Nonviable contaminants from wastewater U.S.
EPA Symposium on Wastewater Aerosols and Disease, Sept. 19-21, 1979. Cincinnati,
Ohio.
3. Elia, V., V. Majeti, and C. S. Clark. 1979. Worker exposure to organic chemicals at an
activated sludge plant. U.S. EPA Symposium on Wastewater Aerosols and Disease,
Sept. 19-21, 1979. Cincinnati, Ohio.
4. Johnson, D.E., et al. 1978. Health implications of sewage treatment facilities. EPA-
600/1-78-032. U.S. EPA, Cincinnati, Ohio.
5. Carnow, B., et al. 1979. Health effects of aerosols emitted from an activated sludge
plant. EPA-600/1-79-019. U.S. EPA, Cincinnati, Ohio.
-------
C. S. Clark, et. al 263
6. Camann, D.E., et al. 1979. Wastewater aerosols and school attendance monitoring at
an advanced wastewater treatment facility: Durham Plant: Tigard, Oregon. U.S. EPA
Symposium on Wastewater Aerosols and Disease, Sept. 19-21, 1979. Cincinnati,
Ohio.
7. Johnson, D.E., et al. 1979. The Evaluation of Microbiological Aerosols Associated
with the Application of Wastewater to Land. Pleasanton, California. Southwest Re-
search Institute, San Antonio, Texas.
8. Hicky, J.L.S., and P.C. Relst. 1975. Health significance of airborne microorganisms
from wastewater treatment process. Part II: Health significance and alternatives for
action. Jour. Water Poll. Control Fed. 47:2758-2773.
9. Clark, C.S., E.J. Cleary, G.M. Schiff, C.C. Linnemann, Jr., J.P. Phair, and T.M.
Briggs. 1976. Disease risks of occupational exposure to sewage. /. Environ. Eng. Div.,
ASCE, 102:375-388.
10. Central Public Health Engineering Research Institute (CPHERI). 1971. Health status of
sewage farmworkers. Technical Digest, No. 12, May 1971. Nagpur, India.
11. Nityananda, K. 1976. Leptospirosis-Serological survey of occupational groups in Cey-
lon. /. Trap. Med. Hyg., 250-254.
12. Fuchs, G.H.P. 1971. Problems of occupational leptospirosis in so-called dirty occupa-
tions. Zbl. Bakt. I. Abt. Orig., 180:549-561 (Excerpta Medica 1961,1971).
13. Anders, W. 1954. The Berlin sewer workers, R.E. Oesper, University of Cincinnati,
trans. Zeitschrift for Hygiene, 1:341-371.
14. Rylander, R., J. Andersson, L. Berlin, L.G. Berglund, R. Bergstrom, L. Hanson, M.
Lundholm, and I. Mattsby. 1976. Sewage workers' syndrome. The Lancet, 2:478-479.
15. Rylander, R., and M. Lundholm. 1979. Responses to wastewater exposure with refer-
ence to endotoxins. U.S. EPA Symposium on Wastewater Aerosols and Disease,
Sept. 19-21, 1979. Cincinnati, Ohio.
16. Lay ton, R.F. 1976. Discussion: "Disease risks of occupational exposure to sewage. /.
Environ. Eng. Div, ASCE 102:1134-1135.
17. Lous, P. 1977. Provisional report to the Public Health Office, Kettering Laboratory
Library, University of Cincinnati, trans. Bispebjerg Hospital, Copenhagen, Denmark.
18. Dean, R.B. 1979. Disease rates among Copenhagen sewer workers. U.S. EPA Sym-
posium on Wastewater Aerosols and Disease, Sept. 19-21,1979. Cincinnati, Ohio.
19. Metropolitan Sanitary District of Greater Chicago. 1977. Viral and bacterial levels
resulting from the land application of digested sludge. Final Report to the U.S. Envi-
ronmental Protection Agency by the Metropolitan Sanitary District of Greater Chi-
cago, Contract No. 18-02-22, 1977.
20. Andersen, A.A. 1976. A sampler for respiratory health hazard assessment. Am. In-
dust. Hygiene Assoc. Jour., March-April 1976.
21. American Public Health Association. 1975. Standard Methods for the Examination of
Water and Wastewater. 13th Ed.
DISCUSSION
MR. BEARDSLEE: When you said that inexperienced sewage-ex-
posed workers displayed higher incidence of gastrointestinal illness
when compared to the various other groups, was this for both aerosol
and waste-exposed workers?
DR. LINNEMAN: Yes, that was for the combined groups.
MR. BEARDSLEE: Those coming in direct contact with sewage
were included in that category?
DR. LINNEMAN: That is right. The point of our concern, to ex-
pand on that a second, was whether or not the gastrointestinal illnesses
occurred only in the early phases of employment. A preliminary look at
the data suggests that, indeed, this is not the case. These are not ill-
nesses occurring only in the first few weeks of exposure. They are
distributed over the first half year or so of employment.
DR. FLIERMANS: I am interested in your Legionella findings. The
35% that you expressed, is that combined from all three cities, and are
-------
264 Wastewater Aerosols and Disease/Occupational Studies
there differences among those cities?
DR. LINNEMANN: They were looked at for each city, and I simply
combined them because there were no significant differences among the
cities themselves.
DR. FLIERMANS: At a 128 level which CDC uses, what was that
percentage?
DR. LINNEMANN: I think it was about half of what you saw on the
figure.
DR. FLIERMANS: What were the serogroups that were used to
measure IFA?
DR. LINNEMANN: These preliminary studies were only with sero-
group I. Antigens are now available for serogroup II but we have not
looked at them. We plan to in the future.
DR. PHAIR: There is a degree of cross reactivity that might be mani-
fest in titer differences, but you would still have positive and negative
reactions.
DR. WARD: The percentage of persons that have antibody to hepa-
titis A seems unusually high at 30 to 67%. Is that something that is
related to socioeconomic class?
DR. LINNEMANN: It is related to socioeconomic class, and I think
you see figures like this in a number of other surveys that looked at
similar populations.
DR. WARD: So, for instance, would the upper middle class be
around 10%?
DR. LINNEMANN: There have been surveys in those populations
that have been that low, yes.
DR. WARD: So, actually, by examining sewage workers, you are
examining a special class of people and persons, for example, in a higher
socioeconomic group might be more of a risk if they were exposed to the
same type of material as the sewage workers are exposed?
DR. LINNEMANN: Absolutely.
DR. RYLANDER: Concerning the gastrointestinal symptoms, they,
by your description, fit exactly into the type of symptoms that we ob-
served in our studies. However, we made an observation where we
divided the employees into those who had a low exposure level, because
they encountered sludge dust only occasionally when it was airborne, as
compared with those who had a high exposure level because they were
continuously exposed. We had symptoms in both groups which included
intestinal trouble and high IgG. Those who went in occasionally were
more affected than those who stayed in the foulest part continuously. I
wonder if you had similar observations?
DR. CLARK: We haven't compared that yet; we will soon, though.
-------
265
Worker Exposure to Organic Chemicals at an
Activated Sludge Wastewater Treatment Plant
V. J. Ella, C. S. Clark, V. A. Ma jet i, T. Macdonald, N.
Richdale
University of Cincinnati Medical Center
Department of Environmental Health
Cincinnati, Ohio 45267
ABSTRACT
During a seroepidemiological study concerned with evaluating the potential health risks of
workers involved in the treatment of municipal wastewater, it was observed that the
treatment plant had a characteristic and irritating odor which might be attributed to chemi-
cal wastes. The treatment plant is located near a manufacturer of pesticides and flame
retardants. The potential exposure of treatment plant workers to the chlorinated organics
and insecticides from this manufacturer prompted an investigation to discern whether
these substances were present in the influent wastewater and in the air. Individual expo-
sures were also estimated by personal air monitoring and by measuring urinary excretion
of selected chlorinated organics.
Influent wastewater and area air samples were collected at various locations in the
treatment plant from May through November 1978. Both influent wastewater and the
workplace air contained substantial quantities of hexachlorocyclopentadiene (HEX) and
several other chlorinated organics including hexachloronorbornadiene (HEX-BCH), hep-
tachlorobicycloheptene (HEX-VCL) and chlordene. Typical concentration ranees for in-
fluent wastewater were: HEX (0.3 to 4 ppb), HEX-BCH (10 to 430 ppb), HEX-VCL (15 to
720 ppb) and chlordene (0.3 to 2000 ppb). The highest concentration of these substances in
the ambient air at several locations in the treatment plant was 280 jug/m3 for HEX-BCH.
Further assessment of occupational exposure to these substances was indicated by their
presence in urine specimens collected from workers at the end of the shift.
During a prospective seroepidemiological study aimed at evaluating
the health risks from bacteria and viruses associated with the treatment
of municipal wastewater, an opportunity developed to investigate expo-
sure to organic chemicals emitted from the wastewater during the treat-
ment processes. In the early part of 1978, workers at one of the waste-
water treatment facilities being studied complained of acute symptoms
of respiratory distress, dizziness, headache, and irritation of the eyes,
throat, nose, lungs, and skin. It was also noted that the plant had an
unusual and characteristic odor which was similar to what might be
expected from industrial chemical wastes. The incidence of acute symp-
toms seemed to be associated with periods of more intense chemical
odor. Although it has been generally recognized that workers in sewage
treatment plants may be at an increased risk of exposure to infectious
agents (1), only recently have studies revealed incidences of exposure of
sewage treatment plant workers to potentially toxic chemicals.
-------
266 Wastewater Aerosols and Disease/Occupational Studies
The symptoms reported by the workers in this study were similar to
those experienced by workers approximately a year earlier at the Mor-
ris Foreman Wastewater Treatment Plant in Louisville, Kentucky. In
that incident, exposure was determined to be from pesticide interme-
diates, hexachlorocyclopentadiene (HEX) and octachlorocyclopentene
(OCTA), which were illegally dumped into the municipal sewer system
(2).
The wastewater treatment plant involved in the infectious disease
study, and subsequently in this study, was the North Wastewater Treat-
ment Plant in Memphis, Tennessee. This is a relatively new plant, and it
is located near a manufacturer that produces and utilizes several chlori-
nated organic intermediates for the synthesis of flame retardants and
pesticides (notably isodrin, endrin, chlordane and heptachlor). Waste
from this manufacturer is discharged into a sewer that flows to the
Memphis North Treatment Plant. Concern of potential exposure of
treatment plant employees to toxic levels of chlorinated organics
prompted an investigation to discern whether exposure to such chemi-
cals in this municipal wastewater treatment plant exists. For comparison
purposes, a second plant in Memphis, the Maxson Wastewater Treat-
ment Plant, was used. The sewer from the pesticide manufacturer is not
connected to the Maxson Plant.
The initial objective of this study was to establish a baseline chemical
exposure, if any existed, of wastewater treatment plant workers during
normal operational conditions so that if a spill incident occurred, or
when employees experienced acute symptoms, an assessment of a po-
tential chemical exposure could be made. A secondary objective was to
conduct environmental monitoring to determine: 1) if the influent waste-
water contained selected chlorinated organic contaminants; and 2) if
these substances were being released into the air during the treatment
processes.
Experimental
The initial study carried out in May 1978 was designed to be a screen-
ing of urine specimens for HEX. The study was conducted at the time of
the regular quarterly collection of specimens for the infectious disease
study. Urine samples used in this survey were collected near the end of
the work shift from workers at the North and Maxson treatment plants.
The urine specimens were frozen immediately after collection and were
kept frozen until analyzed. The analysis of urine involved extraction of
urine with petroluem ether, after saturating the urine with Nad. The
petroleum ether extract was analyzed for HEX and HEX-BCH by gas
chromatography using an electron capture detector. The analyses were
performed with glass columns packed with OV-101 or OV17/QF-1 at
175°C.
The primary route of exposure of treatment plant workers to these
substances is probably by inhalation. Therefore, it was important to
determine the concentration of these substances in the ambient air in the
treatment. Apparently, chemical wastes enter the treatment plant either
-------
V.J.EHa, et.al. 267
in a soluble form or adsorbed to suspended materials in the wastewater.
Aeration during the treatment processes causes aerial dispersion of
these substances as aerosols and vapors.
Dispersion of organic contaminants into the ambient air was estab-
lished by collecting area air samples at several locations in the treatment
plant. Air sampling consisted of drawing air through glass sampling
tubes containing 150 mg of preextracted Chromosorb 102 (3). Chlori-
nated organics were desorbed from the sorbent with petroleum ether
and subsequently analyzed by gas chromatography using an electron
capture detector (Ni63).
Urine screening was again conducted during June and September
1978. Urine samples from both the start and end of the work shift were
collected in June 1978. During the September 1978 screening, end-of-
the-shift samples were also obtained from a Cincinnati, Ohio, wastewa-
ter treatment plant. Personal air monitoring of a group of workers at the
Memphis plants was conducted in September 1978 both at their work
site and while they were away from work. Ambient air and influent
wastewater were monitored at various times from May to November
1978.
Results
Seventy-two workers participated in the first urine screening, 41 from
the North plant and 31 from the Maxson (South) plant. The results of
this survey are presented in Table 1. HEX was found in urine specimens
for 25% of the individuals at the North Plant. HEX-BCH, more promi-
nent than HEX, was found in 90% of the samples. Urinary concentra-
tions of HEX-BCH were also higher than those of HEX.
Tabte 1. Analysis of HEX and HEX-BCH in Urine Samples Collected at
the End of Shift in May 1978 (Memphis)
Plant
North
South
HEX
Range
Np/Nja jug/I
10/41 <0.8-2.5
2/31 <0.8-1.4
HEX-BCH
Range
NP/NT<, jjg/i
37/41 <0.3-15.2
11/31 <0.3-9.5
"Np = number of samples containing the compound Nj = total number of samples
Figure 1 shows typical gas chromatograms of influent wastewater
collected at the North and Maxson treatment plants during the time of
this study. The North plant sample clearly shows the presence of several
contaminants including HEX-BCH, heptachlorobicycloheptene (HEX-
VCL) and chlordene. In comparison, the influent samples at the Maxson
plant do not contain these types of contaminants. Although the presence
of several contaminants in the wastewater is indicated, they would have
to be emitted into the air as aerosols or vapors before significant expo-
sure to workers would occur.
Gas chromatograms of area air samples collected at the wet well and
grit chamber of the treatment plants are similar in appearance to the
chromatograms of the wastewater. These samples showed that HEX,
-------
268 Wastewater Aerosols and Disease/Occupational Studies
O
CO
NORTH PLANT
15 MIN
SOUTH PLANT
15 MIN.
Figure 1. Gas Chromatograms of Extracts of Influent Wastewater
Samples
HEX-BCH, HEX-VCL, and chlordene were present in the atmospheric
air at the Memphis North Treatment Plant and indicate that the source
was aerial dispersion from the wastewater. Air samples have also been
obtained at the grit chamber of the Maxson Plant and the Mill Creek
Treatment Plant in Cincinnati, Ohio. These chromatograms had several
early eluting peaks suggesting the possible presence of some volatile
chlorinated hydrocarbons. However, there was no indication of the sub-
stances found in the samples obtained at the Memphis North Plant.
The concentrations of four chlorinated organics found in the influent
wastewater of the Memphis North Plant during the time of air sampling
and urine screening studies are given in Table 2. Although these values
do not represent the values for the complete month, they are indicative
of the concentrations at various times. The concentration of HEX-BCH
was generally about 300 ppb, although much lower levels were measur-
ing during October and November. HEX-VCL and chlordene concen-
trations seem to be more variable, ranging from about 17 to 2000 ppb.
-------
V.J. Elia, et. al. 269
Table 2. Influent Wastewater at Memphis North Treatment Plant, 1978
Concentration, jug/I
Date HEX HEX-BCH HEX-VCL Chlordene
June
August
September
October-November
3
<0.8
4
<0.8
334
329
292
11
57
115
668
17
87
216
58
32
One sample collected during September had a chlordene concentration
of 1980 ppb. The September samples listed in Table 2 were collected at
the time of a reported spill which occurred subsequent to the urine
screening that month. The analysis of wastewater and air samples indi-
cated that HEX-VCL was at least one of the major constituents in the
spill.
Area air samples collected at various locations in the treatment plant
provide an indication of the magnitude of aerial dispersion of these
semivolatile compounds. The concentrations of these substances found
in air samples collected in the wet well, which is a building with a
ventilation system, and the grit chamber are presented in Table 3. The
levels at the wet well are generally higher than at the grit chamber. HEX
was found at levels as high as 39 fig/m3. The highest levels of HEX-BCH
and HEX-VCL measured were 280 (JLg/m3 and 200 (Jig/m3, respectively.
Table 3. Area Air Samples Collected at the Memphis North Plant, 1978
Concentration, jug/mj
Location Date HEX HEX-BCH HEX-VCL Chlordene
Wet well
Grit chamber
May
June
September
October
November
May
June
July
September
October
November
<003
18
8
15
39
<0.03
6.3
<0.03
0.02
0.04
12
219
278
25
2.4
68
4.1
65
0.5
05
1.2
2.6
87
15
200
1
85
1 9
1.5
07
1.1
1 0
43
45
16
44
<0.14
7.8
0.9
5.3
2.3
27
0.8
1.0
Since the initial urine screening conducted in May 1978 revealed the
presence of at least two compounds (HEX and HEX-BCH) in a number
of urine specimens, a follow-up urine screening was conducted in June
1978. In this study, urine specimens were collected early in the work
shift (beginning of shift) and a second specimen was collected near the
end of the work shift. This sampling strategy was undertaken to investi-
gate the relationship between exposure and the appearance of these
chemicals in urine. The results of this study are summarized in Tables 4
and 5. A number of the urine samples obtained early in the work shift
(Table 4) had detectable amounts of both HEX and HEX-BCH. How-
ever, in the case of North plant samples, some exposure could have
-------
270 Wastewater Aerosols and Disease/Occupational Studies
Table 4. Urine Samples of Wastewater Treatment Employees Col-
lected During the First 4 Hours of the Shift in June 1978
(Memphis)
HEX HEX-BCH
Plant
North
South
NP/NT"
11/56
5/24
Range
M9/I
<0.8-3 7
<0.8-4 8
NP/N-P.
18/56
10/24
Range
<0.3-7 5
<0.3-12
"Np = number of samples containing the sample Nj = total number of samples
Table 5. Urine Samples of Wastewater Treatment Plant Employees Col-
lected at the End of Shift in June 1978 (Memphis)
HEX HEX-BCH
Plant
North
South
NP/NTO
5/53
5/18
Range
<0.8-3.1
<0.8-3.9
NP/NJ,,
41/53
2/18
Range
/jg/l
<0.3-103
<0.3-1 6
"Np = number of samples containing the compound Nj = total number of samples
occurred prior to obtaining the specimens. The HEX-BCH concentra-
tions for the Maxson (South) plant samples had one high value of 12^ g/1
which was much higher than the other samples. The values for the other
nine samples ranged from 0.4 to 3.5 ^g/1, while the values for the North
plant sample ranged from 0.4 to 7.5 [o.g/1. End of the work shift samples
(Table 5) indicated that urinary excretion of HEX-BCH increased during
the work shift for individuals at the North plant. Thirty-two percent of
the early-in-the-shift samples had detectable concentrations of HEX-
BCH. This increased to 77% for the end-of-the-shift samples; the means
for these was 4.1 (j.g/1.
Of 43 paired urine samples at the North plant, one each at the begin-
ning and end of the shift from the same individual, 34 increased during
the shift for HEX-BCH while three decreased and six were below de-
tectable limits both times. This contrasts with the Maxson (South) plant
results where only two increased in HEX-BCH concentration, seven
decreased, and nine pairs were below detectable limits. For HEX con-
centrations, 32 paired urine samples from the North plant workers were
below detectable limits, four increased, and eight decreased. At the
Maxson plant, 12 pairs were below detection each time, three increased,
and three decreased.
The data, presented in Table 6, give the results for a urine screening
conducted in September 1978 at the time of the regular quarterly speci-
men collection. One individual at the North plant had a detectable con-
centration of urinary HEX-BCH. HEX was not found in any of the
North plant samples and neither HEX nor HEX-BCH was found in the
-------
V.J.EIia, et.al. 271
samples of individuals from the Maxson (South) plant. Urine samples
were also collected from a wastewater treatment plant in Cincinnati to
Table 6. Urine Samples of Wastewater Treatment Plant Employees
Collected at the End of Shift in September 1978
HEX HEX-BCH
Range Range
Plant NP/NT. Mg/| NP/NT,, Mg/i
North (Memphis) 0/49 — 1/49 0.8
South (Memphis) 0/23 — 0/23 —
Mill Creek (Cincinnati) 0/21 — 0/21 —
«Np = number of samples containing the compound Nj = total number of samples
serve as a control. Air samples collected at the North plant at this time
(Table 3) showed that the concentrations of airborne chlorinated organ-
ics were considerably lower than those found in May and June.
Personal air monitoring of 11 workers at the North plant was carried
out in September 1978. Eight-hour personal air samples were collected
during the work shift and during the workers' off-shift time (home sam-
ple). The work shift sample for most of the North plant workers con-
tained HEX, HEX-BCH, HEX-VCL and chlordene. There was no ob-
vious relationship between work area and the extent of exposure.
Several of the home samples also had detectable amounts of some of
these compounds, but the levels were considerably lower than the work
shift sample. The air concentrations for the four compounds found from
personal air monitoring were in good agreement with the concentrations
determined from area air samples collected at the grit chamber. The
samples of the workers at the Maxson plant were below detection limits
except one work shift sample which contained a trace of HEX-BCH.
The source of the organic chemicals found in urine specimens and
occasionally in air samples from the Maxson plant is not well under-
stood. Possibilities include: intermittent discharge into the sewer system
by either a user of these chemicals or a waste hauler; discharge from a
buried dump site containing these substances; and ambient air pollution
in the Memphis area. It is clear from the data collected during the study
that these compounds are not present at the Maxson plant at the same
levels as the Memphis North plant, nor do the positive values seem to be
associated with working at the Maxson plant, since paired urine samples
at the beginning and end of the work shift do not increase in concentra-
tion of the chemicals.
Discussion
It is generally recognized that wastewater treatment plant workers are
exposed to a wide variety of infectious agents. Only recently has it
become apparent that these workers are also exposed, at times, to toxic
chemicals. In industrial operations, control measures can usually be
instituted to minimize worker exposure and atmospheric release of toxic
-------
272 Wastewater Aerosols and Disease/Occupational Studies
contaminants. However, wastewater treatment facilities, with their
many open tanks and basins, generally are not designed so that aerial
dispersion of contaminants can be eliminated. Furthermore, the nature
and quantity of chemicals in the influent wastewater are usually highly
variable and generally unknown. In many systems, aeration of the
wastewater is a vital treatment process, but this also causes increased
aerial dispersion of certain chemical contaminants as aerosols and
vapors.
Hexachlorocyclopentadiene is a semivolatile compound which is only
slightly soluble in water. Inhalation, dermal, and oral exposures of HEX
have been reported to cause several short-term and toxicological symp-
toms. Animal studies have indicated that long-term exposures may re-
sult in a number of nonspecific adverse health effects (4). In 1977 a
threshold limit value (TLV) of 110 |ig/m3 was recommended by the
American Conference of Governmental Industrial Hygienists (5). TLV's
have not been established for the other compounds, but there are indica-
tions that HEX-BCH may be as toxic as HEX. Hypothetically, if it is
assumed that the TLV for HEX-BCH would be equal to the TLV for
HEX (110 |u.g/m3 or 10 ppb), air concentrations measured in the wet well
during May and June 1978 would be about two times this TLV level. In
practice, when evaluating air exposure levels for two or more hazardous
substances, the effects of those substances should be considered addi-
tive unless other information is available. This practice implies that for
complex exposure situations, i.e., those that might be encountered at
wastewater treatment facilities, determination of exposure levels of a
single chemical may not adequately reflect the actual exposure burden
experienced by an individual. In this case, consideration of the exposure
levels of several substances is recommended.
The Louisville, Kentucky, episode demonstrates a case of acute ex-
posure to toxic contaminants from wastewater. The situation described
in this paper is a case of essentially continuous chronic exposures with
intermittent acute exposures. Unfortunately, only limited information is
available on the toxicity and health effects of these chlorinated organics.
Thus, the significance of urinary excretion of these substances and the
possible relationship to health effects are not known.
Acknowledgement
Financial support for this study came from Research Grant No. R
805445 from the Health Effects Research Laboratory (Cincinnati) of the
U.S. Environmental Protection Agency. Acknowledgement is also given
to the many persons involved in this study including Kathy Hunninen,
M.S., Darryl Alexander, B.S., Virginia Boyle, R.N., Sandra Russell,
R.N., Peter Lurker, M.S., and Willard Wells, M.S.
References
1. Clark, C.S., E.J. Cleary, G.M. Schiff, et al. 1976. Disease risk of occupational exposure
to sewage. /. Environ. Eng. Div., 102:375-388.
2. Morse, D.L., J.R. Komlnsky, C.L. Wisseman, and P.J. Landrigan. 1979. Occupational
exposure to hexachlorocyclopentadiene: How safe is sewage?/AMA, 241:2177-2179.
-------
V.J.Elia, et.al. 273
3. Thomas, T.C., and J.N. Seiben. 1974. Chromosorb 102, an efficient medium for trapping
pesticides from air. Bull. Environ. Contamination and Toxicology, 12:17-25.
4. Treon, J.F., P.P. Cleveland, and J. Cappet. 1955. The toxicity of hexachlorocyclopenta-
diene, Indust. Health, 11:459-472.
5. American Conference of Governmental Industrial Hygienists. 1977. Threshold limit val-
ues for chemical substances and physical agents in the workroom environment with
intended changes for 1977. American Conference of Governmental Industrial Hygien-
ists, Cincinnati, Ohio.
DISCUSSION
DR. PHAIR: In the past two or three years, there have been publica-
tions about the inhalation of chlorinated hydrocarbons, ring compounds,
thallic anhydrides, and compounds of that nature in the chemical indus-
try. Certain numbers of workers have been shown to have respiratory
symptoms, and other groups have been shown to have an allergic asth-
matic type of disease.
One approach to this problem has been to use a reactive chemical as a
hapten, bind it to protein carriers, and then look for antibody in the
workers. I wonder if you have thought about this approach in getting a
handle on health effects, especially in those individuals who seem to
have a chronic exposure because of their environment?
DR. ELI A: We have not tried anything like that.
MR. COLLINS: First of all, I want to thank Dr. Clark and his asso-
ciates for the studies they did in bacterial and viral problems and in
pesticides at our Memphis sewage treatment plant. I have a question
which you can clear up for me. Since HEX and HEX-BCH have rela-
tively good absorption abilities, what is the possibility that these com-
pounds could have been absorbed by NaCl during the testing prepara-
tion and given erroneous results?
DR. ELIA: This has been looked at and considered. At the time
when we ran our urine specimens, we ran blanks which included carry-
ing urine through the complete process and using all of the reagents. At
that time, we did not have any traces of contaminants in the areas of
HEX or HEX-BCH in our chromatograms. We have received a sample
of the salt. Those salt samples were also analyzed 3 or 4 weeks after our
studies, and I am sure that if it had been left open for a period of time it
certainly could have picked up contamination, especially if there are
levels of these compounds continuously in that environment.
Our analysis of the salt samples, which you referred to, does not show
any indications of HEX or HEX-BCH. We have done this in Cincinnati.
I also have chromatograms that were run on those salt samples from the
chemist at the Memphis North Treatment Plant; and those chromato-
grams do not show any traces of HEX or HEX-BCH, but do show traces
of HEX-VCL and a little bit of chlordene. The amounts that they used in
their samples were probably larger, maybe at least two or three times the
amounts which we normally used in our extraction of the urine samples.
Also, a number of these samples run during that time did not show any
presence of these compounds; and, if there was actually contamination,
you would expect it throughout all of the samples.
MR. COLLINS: I want to thank you.
-------
274
Disease Rates Among Copenhagen Sewer Workers
Robert B. Dean
LunDean Environmental Co.
Cincinnati, Ohio, and Copenhagen, Denmark
ABSTRACT
Sewer workers in Copenhagen, Denmark, have a higher death rate than the comparable
male population. An alarmingly high proportion of the deaths occur within the year that
employment terminates. Attempts to correlate the statistics with sick leave records or
chemicals in the environment have not been successful so far. Sewer workers experience a
high rate of gastrointestinal tract disorders which they associate with chemical odors and
infectious agents. They have elevated levels of gamma globulins Analytical work has not
yet identified any agents that might be responsible for the observed death rates or the
gastrointestinal problems Biological examinations of stool specimens have not been
made.
The health of sewer workers has been discussed in the literature for at
least the past 25 years (1). There is no doubt that sewer workers are
exposed to a relatively high level of enteric pathogenic agents in the
course of their work. In industrialized countries, there is also potential
exposure to chemical vapors such as benzene and other solvents used in
paints and manufacturing. Attempts to relate exposure to disease rates
have seldom shown statistically significant effects. In fact, some anec-
dotal reports have claimed that sewer workers had lower rates of absen-
teeism than control groups (2). This was explained on the assumption
that the sewer workers got protective immunization doses of infectious
agents and thus developed resistance to more serious infections.
The health and working conditions of sewer workers in Copenhagen
have been investigated and reported in a series of documents published
and discussed over the period 1975 through 1977. In April 1974, the
union representing the sewer workers requested the University of Co-
penhagen to investigate environmental and health problems of Copen-
hagen's sewer workers. The study was assigned to J. M0rkholdt Ander-
sen and Tage Egsmose, M.D., associate professors at the University's
Institute of Hygiene. Some financial assistance was provided by the
municipality from the sewer department's budget.
The preliminary report came out in December 1975, and was pub-
lished with minor corrections in April 1976 (3). Additional death statis-
tics were presented later (4), and sick leave data were provided by the
municipality (5) as a response to the original preliminary report. In April
1977, a second report was published based on medical consultations
with sewer workers (6). A report of blood and urine chemistry was
issued in 1977 (7). The data in these reports have been summarized in
a U.S. EPA report (8) which forms the basis for this paper.
-------
Roberts. Dean 275
The municipality of Copenhagen serves 600,000 permanent residents,
approximately 200,000 transients and commuters, and has an industrial
load equivalent, on a BOD5 basis, to 1,600,000 additional persons for a
total equivalent load of 2.4 million. The sewage is strong, on the order of
750 mg/1 BOD. At the present time sewage is screened to remove rags
and large objects and discharged through two outfalls directly to the
waters between Copenhagen and Sweden. A modern treatment plant
using high rate activated sludge with the UNOX pure oxygen process is
under construction and is expected to go into operation in late 1979. One
small plant uses primary treatment and digestion. Over the entire period
covered by the reports, sewer work involved primarily cleaning and
maintenance of sewers, manholes, screens, and pump stations. It did
not include sewer construction or mechanical shopwork such as repair-
ing motors and pumps. About 80 permanently employed workers were
classified as sewer workers in 1976. Management of the sewers is a
division of the City Engineer's office. The sewer workers are members
of the Earth and Concrete Workers Union and the Highway Department
Workers Club.
"The Sewer Workers Report" (3) is based on four separate studies:
• responses to a questionnaire given to sewer workers about health and
working conditions
• a study of sick leave records from January 1957 through December
1973 for sewer workers and a control group of all city office workers
• a study of death records compared with national mortality statistics
• assessment of reports of analyses of sewer atmospheres for toxic
substances.
The report "Sewer Work and Health" (6) is based on clinical consul-
tations with 82 out of 97 sewer workers in 1976. The same group and two
control groups were subjected to a battery of tests on blood and urine
(7,9). The reports are considered together.
Questionnaires and Sick Leave Records
Responses to the questionnaires as well as the medical consultations
clearly show that sewer workers consider their job to be unhealthy and
unsafe. A detailed analysis of the responses to the questionnaires is not
included because the responses are difficult to reproduce and are liable
to be influenced by local customs and recent news items concerning the
environment. Sick leave records are also difficult to analyze because the
decision to take sick leave is made by the worker. In Denmark, sick
leave pay for permanently employed municipal workers is 100% of base
pay but does not include extra pay for "dirty work." Medical confirma-
tion of short illness is seldom required.
Table 1 compares sick leave for permanently employed sewer work-
ers over the period 1959 to 1973 with male office workers of comparable
ages in the year 1964. At all ages above 30 years, the sewer workers take
more leave than office workers. Most significant is the high percent of
sick leave taken by sewer workers over 50 years of age. Workers over 60
years of age take an average of 1 day in 5 as sick leave.
-------
276 Wastewater Aerosols and Disease/Occupational Studies
Table 1. Sick Leave for Sewer Workers and City Office Workers (3)
Sewer workers
(1959-1973)
Age
24-29
30-39
40-49
50-59
60-69
Sick days
71
2,100
3,362
2,426
623
%
07
40
56
92
201
Office workers
(1964)
Sick days
855
1,755
4,667
7,756
9,952
%
1 5
1 6
27
39
54
A rebuttal from the City Engineer's Office (5) gives the comparative
sick leave data shown in Table 2; unfortunately no age adjustment.
There are relatively few transfers between work groups. The high sick
leave of garden and park workers is attributed to hazardous working
conditions, as in trees, rather than a selection of older workers for
garden and park work. There is no evidence that sewer workers take
more sick leave than other manual workers although sewer workers
certainly take more sick leave than office workers.
Table 2. Sick Leave Rates of Unskilled Wage Earners in the City Engi-
neer's Office, Not Adjusted for Age
1973(%) 1974(%)
Parking meter collectors 61 65
Street cleaners 71 73
Sewer workers 76 88
Street repairmen 81 9.4
Garden and park workers 106 109
Workshop and warehousemen 103 122
The second study (6) was recommended by the authors of the first
report (3), and was financed by the municipality to investigate health
problems among sewer workers. Matched control groups from the city
gardeners and from office workers were chosen by the municipal person-
nel office, and their blood and urine chemistry were determined (7,9);
however, not enough money was supplied for a medical examination of
the controls. This report confirmed the questionnaires of the first report
and concluded that sewer workers have a higher than normal incidence
of acute symptoms of gastrointestinal disorders including nausea, vom-
iting, and diarrhea. It further concluded that the disorders are directly
related to the intensity of exposure to sewer odors and splash. Half of
the workers have had diarrhea in the past year, and 10% say they have
experienced it one or more times a week. The frequency of the disorders
is related to current exposure and not to years of experience. Few
workers go to their doctors for treatment for gastrointestinal disorders
but seem to consider them to be part of the job. No examinations of
stool specimens were made. The doctors concluded that sewer workers
have a high level of chronic problems including fatigue, difficulty in
concentrating, headaches, and dizziness, as well as psychic problems.
The doctors making the 81 examinations found 21 cases of occupational
disease which were reported to the health service doctor. An additional
-------
Robert B. Dean 277
25 cases were not reported because the workers did not wish it.
Many workers consider that odors rather than infectious agents cause
their gastrointestinal disorders. For example, one told the doctor,
"Suddenly you get this stench in the face, and then you know you will
have stomach trouble for the next few days." (6) In a publication from
the Occupational Health Office, a steward said, "Longer vacations are
necessary because we have a very special problem getting accustomed
[to the sewer environment]. After a vacation of a week or more, one is
almost always sick the first two or three work days with vomiting, nau-
sea, headaches, and smarting of the eyes. We don't know what we owe
it to, but it is most likely the chemicals in the sewer." (6)
Analytical Data
The chemical analyses reviewed (3) provide no evidence for toxic
chemicals that might be related to acute gastrointestinal problems. Sol-
vent vapors occasionally exceeded hygienic standards for 1 hour's expo-
sure and H2S once reached 13 ppm versus a standard of 10 ppm. There is
little doubt that industrial discharges frequently contribute high levels of
organic vapors to the sewer, contrary to regulations. Many of these
discharges are of short duration and are, therefore, difficult to identify.
The effect of these vapors on the health of sewer workers is at present
only conjecture. One station was found to have three times the allowa-
ble level of benzene when a sick worker was replaced (6). There was,
however, no diagnosis of benzene toxicity in the sick man. One case of
high lead in the blood was found in a worker who had been cleaning
heating coils in a sludge digester (6). The job was very dusty and the
dried sludge had a Pb content over 100 mg/kg. The worker was trans-
ferred to another job and his blood Pb levels returned to the normal
range. Masks are specified for workers in dust or spray, but the worker
may not have been using his mask effectively. The second study (6)
includes photographs of a worker who was using a high pressure spray
to clean screens but was not using a mask, and of another worker who
was not using his gloves to handle a wooden ball used to clean the sewer,
again contrary to regulations.
The report of clinical laboratory analyses (7) showed little essential
difference over a wide range of chemical parameters between sewer
workers and the control groups chosen by the personnel office. In many
cases the sewer workers, as a group, fell between office workers and
garden workers. In a follow-up study (9) a significantly higher level of
the immunoglobulin, IgG, was found in the sewer workers but no signifi-
cant differences from the control group for IgA pr IgM. Higher levels of
antibodies to hepatitis A were also reported for the sewer workers but
no difference in antibodies to hepatitis B, otherwise known as serum
hepatitis.
Death rates among sewer workers
The initial study (3) showed 24 deaths among 142 sewer workers who
had been employed for at least one year in the period 1957 through 1973.
This is significantly greater than the death rate for all Copenhagen males
of comparable ages. An updated report (4) added nine additional deaths
-------
278 Wastewater Aerosols and Disease/Occupational Studies
that had not been available to the authors at the time of the original
study. Table 3 groups the workers by years of employment and shows
the comparable death rates for Copenhagen males based on the 1975
statistical yearbook. Death rates in Copenhagen do not change very
much from year to year.
Table 3. Death Statistics for Sewer Workers
Years of
sewer work
1-8
9-12
13-16
Chi square
No of
deaths
(N)
8
14
11
Expected
deaths
(E)
9.8
58
5.6
(N-E)2/E
03
11 6
5.2
17 1
Probability
(%)
01
2
0.5
Workers who have spent 1 to 8 years in sewer work in the 15-year
study period have a death rate indistinguishable from the city rate. For
the next 8 years of employment, the rate is more than twice the expected
rate. A statistical analysis of the data shows the following: The chi-
squared test on the three groups, 1 to 8 years, 9 to 12 years and 13 to 16
years, is highly significant. Individual groups were tested against the
Poisson distribution. Death rates for workers with 9 to 12, and 13 to 16
years of employment were significant at the 2% level or better. There-
fore one can conclude that workers who have spent more than 8 years in
Copenhagen sewers have about twice the death rate of all Copenhagen
males. The normal death rate during the first 8 years of employment may
also reflect an adverse environment since sewer workers are selected
from healthy able-bodied males who should have a death rate signifi-
cantly below the city average (11).
When the causes of death of the 33 cases were examined, the only
outstanding difference from the national average was for cancer of the
pancreas. Of nine cases of cancer recorded on the death certificates
there were three cases of cancer of the pancreas, two cases of lung
cancer, and one each for four other cancers. The expected death rate is
only 0.4 cases of pancreatic cancer among 33 deaths of men over 25
years of age. The apparent Poisson probability is 0.8% that three deaths
from pancretic cancer will occur. However, as pointed out by Tukey
(12), the apparent probability of a chosen high-incidence level must be
multiplied by the number of possible choices that could have been made
had the incidence been high in any one of them. In this case, there were
six types of cancer and many other causes of death, so the probability
level is at least 6 times 0.8%, or 4.8%, which is barely significant. The
death certificates have been examined further for other possible corre-
lations, but none have been reported. It was found that one of the three
victims of pancreatic cancer had been employed less than 2 years in
sewer work followed by other employment.
Over 40% of dead former sewer workers died within the calendar year
in which they stopped working (3). The calculation is based on 210 sewer
workers of whom 111 left the work force in the years 1959 to 1973.
Thirty-two of these had died by the end of 1976; 13 of them in the year
-------
Robert B. Dean 279
that employment terminated. The ages at death of 12 of the 13 men who
died in the year that employment terminated were evenly distributed
between 51 and 68 years. Some of these men were ill when they stopped
working. Put another way, 12% of the former workers died in the calen-
dar year in which they terminated work. For comparison, only 1% of
Copenhagen males aged 55 and 3% of those aged 65 will die within the
twelve months following their respective birthdays. Although it is well
known that retirement increases the risk of death, it is more likely that
the causes of death of most of the 13 men were related to the condition
of their health before termination of their employment. It is also known
that manual laborers in some industrialized countries have a higher
death rate than the general male population. Unfortunately, compara-
tive death statistics for other groups of workers in Copenhagen have not
been analyzed.
Conclusion
Mortality statistics show that sewer workers die earlier than Copen-
hagen males of comparable age, many of them soon after termination of
their employment. The sewer workers complain of nauseating odors and
a high incidence of gastrointestinal tract disorders. They have elevated
levels of gamma globulin but no other significant differences from con-
trol groups. The available evidence is insufficient to assign cause for
their poor health and reduced life expectancy. It seems probable that
biological and chemical insults, caused in part by lax observance and
poor enforcement of safety regulations and discharge restrictions have
all contributed to the adverse survival expectancy of this group.
In an attempt to reduce the discharge of solvents and other chemically
hazardous wastes to the sewers, the City of Copenhagen has arrange-
ments with 40 paint and household chemical retailers to collect contain-
ers of waste materials for eventual disposal by Kommune Kemi, Den-
mark's official organization for the disposal of hazardous wastes. The
program is well advertised in the newspapers by posters and displays in
the windows of cooperating dealers. The dealers also give out plastic
carrying bags advertising the program. It is too early to evaluate the
effect of this program on sewer workers' health, but the return of haz-
ardous solvents has been very encouraging.
References
1. Anders, W. 1954. The Berlin sewer workers. Zeit. f. Hygiene, 1:341-371.
2. Melnick, J.L. 1967. Comments. In: Transmission of Viruses by the Water Route, G.
Berg. ed. Interscience. Publishers John Wiley and Sons, New York.
3. Andersen, J.M., L. Egsmos, and T. Egsmos. 1976. Kloakarbejder rapporten (The
sewer workers report). FADL's Forlag, Copenhagen.
4. Egsmos, T., and J. Nyboe. 1976. Vedr^rende d^delighedsunders^gelsen i kloakarbej-
der rapporten (Concerning studies of death in the sewer workers report). University of
Copenhagen Institute of Hygiene.
5. Gulstad, E. 1976. Oversigt over sygeligheden blandt l^narbejderne ved Stadsingeni^r-
ens Direktorat i 1973 og de 3 f^rste kvartaler i 1974 (Review of illness among hourly
workers at the City Engineers Office in 1973 and the first three quarters of 1974).
Unpublished report.
6. Jansson, P., and H. Klausen. 1977. Kloakarbejde og helbred (Sewer work and health).
Eks-skolens Trykkeri ApS, Copenhagen.
-------
280 Wastewater Aerosols and Disease/Occupational Studies
7. Lous, P. 1977. Forel^big rapport til Stadslaegen (Provisional report to the Public
Health Office). Bispebjerg Hospital, Copenhagen.
8. Dean, R.B. 1978. Assessment of disease rates among sewer workers in Copenhagen,
Denmark. EPA 600/1-78-007 U.S. Environmental Protection Agency, Cincinnati,
Ohio.
9. Lous, P. 1978. Rapport til Stadslaegen (Report to the Public Health Office). Bispebjerg
Hospital, Copenhagen.
10. Office of Occupational Health. 1976. Psykisk arbejdsmilj^: Trivsel i kloakr^r og kontor-
landskaber (Psychic working conditions: Thriving in sewer pipes and office land-
scapes). Arbejdstilsynet, Annual Publication of the Office of Occupational Health,
Copenhagen, pp. 45-51.
11. Fox, A.E., and P.F. Collier. 1976. Low mortality rates in industrial chort studies due to
selection for work and survival in the industry. /. Prev. Soc. Med., 30:225-230.
12. Tukey, J.W. 1977. Some thoughts on clinical trials, especially problems of multiplic-
ity. Science, 198:679-684.
-------
281
Sewage Treatment Plant Workers and Their
Environment: A Health Study
Sekla,L.,M.D.,Ph.D.J
Gemmill, D., M.D.2
Manfreda, J., M.D.3
Lysyk, M., B.Sc.4
Stackiw,W.,B.Sc.1
Kay, C., Ph.D.1
Hopper, C., R.N.1
VanBuckenhout, L., R.T.1
Eibisch, G., R.T.1
1Provincial Laboratory, Province of Manitoba.
2Department of Health, City of Winnipeg.
3Department of Medicine and Department of Social and Preventive
Medicine, University of Manitoba.
department of Labour and Manpower, Province of Manitoba.
ABSTRACT
A 1-year multidisciplinary study was conducted in two secondary sewage treatment
plants. Sporadic and inexplicable peaks of H2S approaching and, on occasions, exceeding
acceptable levels have been detected in the grit tank areas. Intermittent excessive levels of
CO2 have been recorded in the secondary treatment areas. Bacteria and viruses were
isolated from the samples of sludge, effluent, and air tested. The comprehensive hemato-
logical, biochemical, serological, and immunological profiles obtained on each of the 77
plant personnel at the beginning and at the end of the study showed few significant
findings. Fecal examination revealed an inexplicable lack of gram-negative bacilli in some
cases. No pathogenic bacteria or viruses were isolated from the throat swabs of personnel
with upper respiratory symptoms. Employees' respiratory health status was assessed by
means of a questionnaire and two lung function tests. Symptoms and abnormalities were
more prevalent in smokers than in nonsmokers and were comparable, in both groups, to
those found in general population. Sinusitis was the most common complaint, indicating
an upper airway problem caused by a yet undetermined irritant, allergen, or infectious
agent. This and other symptoms invariably started upon exposure to the work environ-
ment and improved upon leaving it, thus producing illnesses of short duration.
Concern about the health hazard of the work environment was ex-
pressed by employees and management of two sewage treatment plants
in Winnipeg. By mutual agreement, it was decided that all employees
would participate in a health study sponsored by the city.
The objectives of the study were:
• to assess the health hazard of the work environment
• to assess the health status of the employees
-------
282 Wastewater Aerosols and Disease/Occupational Studies
• to determine any relationship between health hazard and health
effects
• to recommend relevant corrective measures, if any.
A multidisciplinary study was therefore designed to:
• evaluate the work environment by means of a chemical and micro-
biological industrial hygiene survey
• assess the employees' health by means of a questionnaire, clinical
examination, lung function tests, recording of sickness, and an ex-
tensive set of laboratory tests performed on feces and blood
• test sick employees.
INDUSTRIAL HYGIENE CHEMICAL SURVEY
The north plant provides secondary sewage treatment for the largest
part of the metropolitan area of Winnipeg. It consists of: grit removal
and preaeration, primary treatment (clarifiers), and secondary treatment
(totally enclosed building). The raw and the activated sludge generated
are treated by anaerobic digestion and then pumped to sludge-drying
beds in the area. The average dry weather flow is approximately 60
million imperial gallons per day (migd).
The south plant has been designed to serve the southern part of the
city. Its sewage flow is approximately 10 migd with provisions for ex-
pansion to 35 migd. This particular facility is unique in that it is the first
plant in Canada, and one of the first in North America, to use pure
oxygen (95%) generated on site for the biological treatment of sewage.
Table 1 shows the results that were accumulated during the health
study period by continuous monitoring of H2S, temperature, and humid-
ity. Monitoring was carried out in all four seasons of the year, but
significant seasonal variations were not noted. H2S concentrations were
readily detectable in the preaeration building of the north plant and in
the preaeration and primary treatment buildings of the south plant. Of
particular concern is the preaeration building at the north plant where
we detected unexplainable slugs of H2S exceeding the threshold limit
value of lOppm.
Table 1. Continuous Monitoring Results—North and South Plants
H2S Temperature Humidity
Location (ppm) (°F) (%)
Preaeration and grit removal
North plant "to>10 55-74 34-96
South plant "-38 63-80 32-80
Primary treatment
North plant « 56-80 38-96
South plant "-25 54-69 52-99
Secondary treatment
North plant « 63-80 57-90
South plant b k h
"Not detectable
*Not done
-------
L. SekJa,etal
283
Table 2 shows results accumulated on a spot monitoring basis for
H2S, CO2, CO, NHa, and for the following heavy metals: Ni, Pb, Cu,
Zn, and Cd. The H2S levels detected were very similar to those found
using continuous monitoring equipment. Elevated CO2 concentrations
were detected in the enclosed secondary treatment buildings at both
plants. Other contaminants monitored, including heavy metals, were
either not detectable or well below accepted standards.
Table 2. Spot Monitoring Results—North and South Plants
Location
Preaeratron and grit removal
North plant
South plant
Primary treatment
North plant
South plant
Secondary treatment
North plant
South plant
H2S CCX, CO
(ppm) (%) (ppm)
«-6 0.03-O.06 «10
"-2 0.025-0 08
0 03-0.05
«-2 0 02-0.03
h 003-014
0.03-0.50 *
Heavy metals
NH3 Ni,Pb,Cu,Zn,Cd
(ppm) (mg/m3)
<0.02
« h
h h
b
"Not detectable
hNot done
INDUSTRIAL HYGIENE MICROBIOLOGICAL SURVEY
The work environment was also examined microbiologically by test-
ing samples of air and sewage.
Microbiology of Air
Air samples were collected at the same arbitrarily selected locations
as for the Industrial Hygiene Chemical Study. Settling plates containing
enrichment medium were placed for 1 to 15 min, (depending on location
and time of year) for the collection of bacteria. For the collection of
viruses, an impinger was used, pumping 10 S. of air/min into buffered
saline. Standard laboratory procedures were used for the isolation and
identification of microorganisms (1,2).
Table 3 shows that gram-positive bacteria were found predominantly
in winter, in both pre- and secondary aeration areas. However, in the
summer, more bacteria were isolated, and most isolates were gram-
negative bacteria. The significance of this seasonal variation is not clear.
The most common gram-negative bacteria isolated in the summer was
Aeromonas hydrophila. Salmonella and Shigella were not isolated. The
most interesting isolation was that of an atypical Yersinia enterocolitica,
isolated in the summer from the preaeration area of the south plant. Two
of the 13 air samples assayed yielded enteric viruses; both were col-
lected from the secondary aeration area of the north plant. A poliovirus
type 2 was isolated on an RD (3) cell line in winter, and an echovirus
type 7 was isolated on a BGM cell line in the summer.
-------
284 Wastewater Aerosols and Disease/Occupational Studies
Table 3. Airborne Bacteria
Preaeration
Secondary
aeration
Plant
North
South
North
South
Season
Winter
Summer
Winter
Summer
Winter
Summer
Winter
Summer
Total no
Isolates
1,452
6,691
215
5,502
713
1,699
11
800
Gram-
positive
bacteria
(%)
771
184
548
126
663
98
ii
18
Gram-
negative
bacteria
(%)
21 5
81 5
451
874
338
90.1
ii
82
"Not done
Microbiology of Sewage
Grab samples of raw and digested sludges and 24-hour composites of
final effluent were examined by use of standard laboratory procedures
(4).
The total and fecal coliform counts were reduced by the treatment to
5.0 to 8.3 and 5.0 to 7.7 (log™) colony forming units/1 of final effluent,
respectively. Counts were slightly higher in the spring. Coliforms were
not tested for enteropathogenicity, enterotoxigenicity, or transferable
drug resistance.
Fifty-four Salmonella were isolated from 38 samples of sludge and 16
samples of effluent, representing 13 different serotypes, shown in Table
4. All but two, Salmonella thomasville and Salmonella london have been
identified from human feces in Manitoba. The most common was Sal-
monella st. paul, a serotype that has, in the last 15 years, always been
listed among the 10 Salmonella spp. most commonly isolated from hu-
mans in Manitoba. It should be noted that Salmonella typhi was not
isolated.
Table 4. Salmonella Serotypes Isolated from Sewage
Serotype No. of isolates
S. st. paul 15
S muenchen 10
S infantis 8
S typhimunum 5
S newpon 3
S thompson 3
S london 3
S newbrunswick 2
S. heidelberg 1
S panama 1
S WocMey 1
S enteritidis 1
S thomasville 1
-------
L. Sekla, et al 285
Table 5 shows the enteric viruses isolated from raw sewage and ef-
fluent in amounts varying from 500 to 2200 plaque-forming units (pfu)/l
of sewage and from 200 to 1000 pfu/1 of effluent. All the enteric viruses
isolated have been reported from human feces. It is interesting to note
that no enteric viruses were isolated from the samples of digested sludge
examined. In summary, the survey of the work environment has shown
that pathogens were identified in both sewage treatment plants.
Table 5. Enteric Viruses Isolated From Sewage
Virus type
Poliovirus
Coxsackievirus B
Echovirus
Raw Sewage
1-3
2-6
7
Effluent
1-3
2,4,5
3,7
ASSESSMENT OF EMPLOYEES' HEALTH
A total of 77 employees working in both plants were classified on the
basis of their primary duties into five categories: operator, operator/
supervisor, maintenance, laboratory, and clerical. A fair amount of in-
tercategory changes happened during the year. Three employees re-
fused to participate in the study and others participated only partially.
Questionnaire
Participants were given a questionnaire inquiring whether they had
any of the following symptoms or problems during the preceeding year:
fatigue, headache, loss of weight, fever, gastrointestinal problems, and
pneumonia or flu-like diseases. The answers are summarized in Table 6.
Though it is difficult to compare groups because of their small numbers,
operators appear to be the only group reporting headaches every day or
on most days; operators and laboratory personnel indicated "fatigue on
most days" slightly more frequently than those in the other categories.
A larger proportion of operators and laboratory personnel lost weight
over the preceeding year; however, most of this was due to dieting.
There was no difference between the categories with respect to the
Table 6. Frequency (%) of Symptoms by Work Category
Operator
No. %
No of workers
Symptoms
Fatigue
Headache
Weight loss
Fever
Gastro-
intestinal
Chest
36
9
3
15
26
20
25
25
8
42
72
55
69
Supervisor
No %
5
1
—
1
3
2
3
20
—
20
60
40
60
Maintenance
No %
9
1
—
1
5
3
5
11
—
11
55
33
55
Laboratory
No %
18
4
—
8
12
7
12
22
—
44
67
39
67
Clerical
No. %
3
— —
1 33
2 67
2 67
2 67
-------
286 Wastewater Aerosols and Disease/Occupational Studies
proportion of men who reported fever, gastrointestinal problems, and
pneumonia or flu-like disease. However, the frequency of episodes of
fever was higher in operators than in other groups. The employees were
also asked in which area of the plant they worked before the develop-
ment of these symptoms; the most frequently reported location was the
secondary aeration building.
Clinical Examination
At the time of the clinical examination, the employees complained
about the health problems grouped in Table 7 according to the body
system affected and the age group of the employee.
Table 7. Current/Recent Medical Problems
Ages (years)
20-29
30-39
40-49
50-59
60-65+
Total
Upper
respiratory
11
7
9
3
1
31
Gastro-
intestinal
2
3
3
3
0
11
Skin
4
0
7
2
2
15
Nervous
system
3
2
0
1
0
6
By far the most common complaint was related to upper respiratory
problems. Thirty-one complained of plugged noses, recurrent cold-like
symptoms, or hay fever. Several required surgery to alleviate the
symptoms.
The onset of symptoms occurred upon exposure to the plant environ-
ment with resolution occurring gradually after 2 to 3 days' absence from
the plant. This was particularly reported in connection with headaches,
diarrohea, dyspepsia, and skin eruptions. New employees reported hav-
ing experienced these symptoms initially for a few weeks, but the condi-
tion appeared to stabilize with passage of time.
Lung Function Tests
Each employee was given two lung function tests, the forced vital
capacity maneuver, and the single breath nitrogen test (5,6). Results are
shown in Table 8 for the following parameters: forced vital capacity
(FVC), forced expiratory volume in 1 sec (FEVj.o), FEV,.0/FVC ratio,
maximum flow when 75% of vital capacity is expired (Vmax*,), clos-
Tabto 8. Lung Function Testing (Mean % Predicted)
Nonsmokers Ex-smokers Smokers
FVC
FEV,.«
FEV, o/FVC
Vmax25
CC/TLC
Slope phase III
91.4
90.9
98.5
95.7
94.5
73.9
90.7
888
97.J.
872
100.6
98.2
90.7
86.4
95.1
75.6
97.8
115.6
-------
L. Sekla, et al
287
ing capacity as percent of total lung capacity (CC/TLC), and the slope of
phase III. The lung function was expressed as percent predicted, and the
averages are shown for three smoking groups (7). If the lung functions
were exactly as predicted, the values would be 100. It can be seen,
however, that the values deviate slightly from the predicted averages.
The effect of smoking is reflected in a lower FEVi.0, FEVi.0/FVC ratio,
and VmaxM, and in a higher closing capacity/total lung capacity ratio and
slope of phase III in smokers than in nonsmokers. The vital capacity of
nonsmokers is lower than predicted, but due to the small numbers tested
it is not possible to ascertain if this is due to their occupations. Seven
men had an obstructed lung function pattern in agreement with their
smoking and disease history.
Absenteeism
During the 1-year study, a public health nurse was informed about any
illness of more than 2 day duration and endeavored to collect relevant
specimens for laboratory testing. In addition, a record of absenteeism
was kept.
Only 66 employees had complete records, shown in Table 9.
Table 9. Absenteeism Per Age Group
Age (years)
20-29
30-39
40-49
50-59
60-65+
Total
No of
Employees
20
16
20
8
2
66
Total
days lost
135
92
106
17
—
350
Avg
days lost
/employee
675
575
5.30
213
—
5.30
Avg duration
of absence
/age group
1 53
1 26
1.33
1 13
—
1 37
The highest number of days lost per person was in the age group 20 to
29. The duration of absence was short (average 1.37 days) and fairly
uniform for all age categories. This observation suggests a common
ailment of short duration; within 2 to 3 days of absence from the plant,
the employee returns to normal.
In general, absenteeism in the plants (5.3 days/employee) was not out
of line with that experienced in other civic departments. However, the
medical reason for absenteeism may be significant. Table 10 relates the
Table 10. Absenteeism and Symptoms
No. of
Symptoms Employees
Sinus only
Gastrointestinal only
Skin only
Central nervous system only
Multiple symptoms
No symptoms
Total
21
3
6
6
10
20
66
Days off
1978
130
22
9
40
87
62
350
% of total
absenteeism
37.03
6.34
264
11 37
2486
1772
100
-------
288 Wastewater Aerosols and Disease/Occupational Studies
percentage of days lost to the symptoms reported by the employees and
indicates that 37% of the time off was due to sinus complaints.
Laboratory Tests
Since the symptomatology reported was unspecific, a comprehensive
set of laboratory tests was performed on each employee in order to
detect any abnormalities that could have been caused by the ingestion
of, inhalation of, or simply by contact with pathogens in the work envi-
ronment. Standard laboratory procedures (8,9) were performed and re-
sults were interpreted following the criteria in current use for each par-
ticular test. The interpretation of some of the serological and
immunological findings required comparison with a control group. Two
such groups, matched for age and sex with the employees of the sewage
treatment plant, were tested. The first control group (Group A) con-
sisted of 20 municipal employees in occupations unrelated to the sewage
treatment plant, expected to be the "healthy" control group. The sec-
ond control group (Group B) consisted of 50 sera submitted to the labo-
ratory for the serodiagnosis of various diseases and, therefore, expected
to be the "sick" control group.
On the employees of the sewage treatment plants, five profiles were
obtained by repeated testing:
• microbiological (fecal) • serological
• hematological • immunological
• biochemical
In addition, relevant specimens were tested on those employees who
became sick during the study.
Microbiological Examination of Feces
Fresh feces were cultured for bacteria and viruses, while S.A.F. (so-
dium acetate, acetic acid, formaldehyde) (10) preserved feces were ex-
amined for parasites. Findings were as follows:
• No pathogenic bacteria were isolated. We specifically looked for
Salmonella spp., Shigella spp., enteropathogenic Escherichia coli
and Yersinia spp.
• No enteric viruses were isolated
• Giardia lamblia was found in three employees, all operators
• Dientamoeba fragilis was found in two employees: one operator
and one maintenance
• Nonpathogenic intestinal protozoa (reflecting feco-oral contamina-
tion) were found in eight employees: Entamoeba coli was identified
in five operators and two laboratory employees; Endolimax nana
was found in one operator
• An unexplainable lack of the normal gram-negative intestinal flora
was found persistently in 16.5% of the employees and intermittently
in 30 to 80% of them. It is interesting to note that nine of the
employees with intestinal protozoa had abnormal intestinal bacter-
ial flora.
Table 11 shows the percentage of employees with abnormal fecal
findings. Operators appear to have more intestinal protozoa than the
other groups.
-------
L. Sekla, et al 289
Table 11. Abnormal Findings in Feces
Category
Operator
Operator Supervisor
Maintenance
Laboratory
Clerical
No. tested
36
5
10
15
3
Intestinal
protozoa (%)
27.7
0
100
133
0
Lack of gram-
negative bacteria (%)
50
80
30
33.3
33.3
Hematological Profile
The hematological profile consisted of the following: red blood cell
counts, white blood cell counts, erythrocyte sedimentation rate and
hemoglobin.
Of the 55 employees tested twice, 90.0% had no hematological
abnormalities.
The erythrocyte sedimentation rate was elevated in three employees:
two operators and one maintenance.
A marginally low red blood cell count was found in two employees:
one operator and one maintenance.
Biochemical Profile
The profile quantified the following substances in blood: Na, K, Ca, P,
glucose, blood urea nitrogen (BUN), bilirubin, serum glutamic oxala-
cetic transaminase (SGOT), lactic dehydrogenase (LDH), and alkaline
phosphatase.
Eighty percent of the 55 employees tested twice had no abnormalities.
Table 12 shows the abnormalities detected:
• Glucose was elevated in one clerical employee
• BUN was elevated in two employees: one operator and one
maintenance
• SGOT was elevated in six employees: four operators, one opera-
tor/supervisor and one laboratory
• LDH was elevated in four employees: three operators and one
laboratory
• Bilirubin was elevated in three employees: one laboratory, one
maintenance, and one clerical.
Again, operators appear to have more abnormal findings than the
others.
Table 12. Abnormal" Biochemical Findings
Category No tested Glucose BUN SGOT LDH Bill
Operator 25
Operator Supervisor 5
Maintenance 9
Laboratory 13
Clerical 3
0
0
0
0
1
1
0
1
0
0
4
1
0
1
0
3
0
0
1
0
0
0
1
1
1
"Elevated
-------
290 Wastewater Aerosols and Disease/Occupational Studies
Serological Profiles
The serological profile consisted of the following batteries:
• bacterial: Salmonella typhi (TH, TO and Vi); Brucella abortus
(B.A.); Leptospira canicola, L. grippotyphosa, L. hardjo, L. ictero-
haemorrhagia and L. pomona; Yersinia enterocolitica and Y. pseu-
dotuberculosis; Mycoplasma pneumoniae
• parasitic: Toxoplasma gondii, Entamoeba histolytica, and Hydatid
cyst.
• Viral: respiratory viruses (Adenovirus, Respiratory Syncytial Vi-
rus, Parainfluenza 1, 2, 3, Influenza A and B), enteric viruses (Polio-
virus 1, 2, 3, Coxsackievirus B2, B5, B6, Echovirus 7 and reovi-
ruses) and hepatitis viruses (Hepatitis A antibodies, Hepatitis B
surface antigen and antibody).
When the results of the tests done on the employees were compared
with those of the two control groups, no apparent differences were
noticed except for those listed in Table 13. Of particular interest are the
findings of Yersinia antibodies, since the sera were tested against the
strain of Yersinia enterocolitica isolated from the air in the south plant.
Antibodies to the reoviruses were expected since the viruses are found
in the sewage; however, their role as pathogens in adults may be ques-
tioned. The absence of antibodies to parainfluenza viruses in employees
of the sewage plants is difficult to explain.
Table 13. Significant Serological Findings
YE 2308" Reovirus Parainfluenza
Category
Employees
Control Group A
Control Group B
No.
62
20
50
% positive
32.2
25
4
No.
53
20
50
% positive
23
5
161
No
55
20
50
1
0
40
8
% positive
2
9.1
55
46
3
2
35
22
°YE 2308 - Yersinia enterocolitica
The total absence of Leptospira antibodies in Manitobans, in general,
and in sewage workers, in particular, is also worth mentioning. During
the 1-year study, two seroconversions were noticed: one to Hepatitis A
virus and one to Brucella abortus, both in laboratory employees. The
study also revealed an asymptomatic carrier of Hepatitis B antigen
(operator/supervisor). Antibodies to Hepatitis A virus were detected in
50% of the employees.
Table 14 shows the percentage of employees with abnormal serologi-
cal findings grouped according to their type of work.
It is interesting to note that if we exclude the clerical group because of
the small number tested, the highest percentage of Brucella antibodies
was found in laboratory employees and the highest percentage of Yersi-
nia antibodies was found in operators. It should be noted that any one
-------
L. Sekla, et al
Table 14. Detail of Positive Serological Findings
291
No.
BA«
% positive
YE" 2308 CB2f CB& ET
Reo/ HAV*
Operator
Operator/Supervisor
Maintenance
Laboratory
Clerical
36
5
10
15
3
138
20
0
535
33
40
20
10
285
66
25
20
30
133
333
138
20
30
33.3
666
27
0
10
0
0
26.9
25
25
83
0
387
60
70
357
333
"BA—Brucella abortus
hYE—Yersiria enferoco/rt/ca
< CB2—Coxsackie B2
<
-------
292 Wastewater Aerosols and Disease/Occupational Studies
Table 16. Abnormal Immunological Findings
Alpha-2
globulins
Operator 1
Operator/
Supervisor 0
Maintenance 1
Laboratory 2
Clerical 1
Total 5
Total
gamma
globulin
5
1
0
0
0
6
igG
0
0
0
2
0
2
IgA
1
0
0
1
0
2
IgM
2
0
1
3
1
7
igM"
3
1
2
1
2
9
igE
12
2
3
3
0
20
"Depressed IgM, all others are elevated
However, as a whole, when compared with those of the two control
groups, the means of the IgG, IgA, IgM and IgE in the employees tested
were not significantly different.
LABORATORY TESTS PERFORMED ON SICK EMPLOYEES
In 1978, a total of 14 throat swabs and three stool specimens were
obtained from sick employees. No pathogenic bacteria or viruses were
isolated.
Blood was collected from 24 sick employees. Nineteen were tested
for an illness suspected to be caused by a Coxsackievirus B3. However,
no significant differences were noted when the results were compared
with those of a control group.
Five employees with flu-like symptoms had antibodies to the respira-
tory viruses prevalent in the community at the time.
Conclusion
The work environment contains potential pathogens. Laboratory tests
have shown several abnormal findings. However, as a group, the em-
ployees did not differ significantly from other Manitobans tested as a
control for this and other studies. This finding was unexpected in view
of the demonstrated presence of pathogens in the work environment. It
is interesting to speculate about the cause of such a discrepancy. It
could be dose-related, implying that the minimal infective dose for hu-
mans, under field conditions, may be higher than expected. It could
equally be due to a substance in the environment that, upon absorption
into the human body, competes with the known pathogens, eventually
preventing their ill-effects.
The relationship between pathogens in the work environment and
illnesses in the employees has not been demonstrated unequivocally. It
has been noticed that absenteeism was more frequent in the younger age
group and in operators. Sickness, however, was usually of a short dura-
tion with resolution upon absence from the work environment.
In view of all the findings just described, it seems appropriate to
recommend a preemployment health examination, in addition to yearly
clinical and laboratory investigations of all employees of sewage treat-
ment plants, and on-going emphasis on personal hygiene. A thorough
investigation of episodes of illness should also be carried out.
-------
L. Sekla, et al 293
The results of the Industrial Hygiene Study point out the need for a
review of existing exhaust provisions, as well as the implementation of
continuous monitoring programs at both plants. Such programs could
include:
• continuous microbiological monitoring
• continuous monitoring for temperature and humidity
• continuous monitoring for H2S
The monitoring units in the preaeration buildings could be equipped
with alarms and lights that would cut in when H2S levels reached, for
example, 5 ppm. They would provide permanent records of H2S concen-
trations that would enable plant personnel to know when peaks occurred
and, eventually, why they occurred.
In addition, it is recommended that monitoring for CO2 and heavy
metals be intensified and that air and sewage samples be analyzed for
pesticides.
References
1. American Public Health Association. 1970. Diagnostic Procedures for Bacterial, My-
cotic & Parasitic Infections, H.L. Bodily, ed. American Public Health Association.
2. American Public Health Association. 1969. Diagnostic Procedures for Viral and Rick-
ettsial Infections, E.H. Lennette and N.J. Schmidt, eds. American Public Health
Association.
3. Schmidt, H.J., H.H. Ho, J.L. Riggs, and E.M. Lennette. 1978. Comparative sensitivity
of various cell culture systems for isolation of viruses from wastewater fecal samples.
Appl. Environ. Microbiol., 36:480-486.
4. Standard Methods for the Examination of Water & Wastewater. 14th Ed. M.C. Rand,
A.E. Greenberg, M.J. Taras, eds. American Public Health Association, American
Water Works Association, Water Pollution Control Federation.
5. National Heart and Lung Institute. 1973. Suggested standardized procedures for clos-
ing volume determination (nitrogen method). National Heart and Lung Institute.
6. National Heart and Lung Institute. 1971. Recommended standardized procedures for
NHLI lung program epidemiological studies. National Heart and Lung Institute.
7. Manfreda, J., N. Nelson, and R. M. Cherniack. 1978. Prevalence of respiratory abnor-
malities in a rural and an urban community. Am. Rev. Respir. Dis., 117:215.
8. Todd Sanford. 1974. Clinical Diagnosis by Laboratory Methods. 15th Ed. J. David-
sohn, and J.B. Henry, WG Saunders Company.
9. American Society for Microbiology. 1976. Manual of Clinical Immunology, N.R. Rose
and H. Friedman, eds. American Society for Microbiology.
10. Yang, J., Th. Scholten. 1977. A fixative for intestinal parasites permitting the use of
concentration & permanent staining procedures. Amer. J. Clin. Path., 67:300-304.
DISCUSSION
DR. FANNIN: Does this suggest that if a treatment plant is en-
closed, we might expect higher enterovirus concentrations that result in
greater risk to workers than in an open plant?
DR. SEKLA: It appears to be so.
DR. RYLANDER: I think I can shed some light upon our theories of
the seasonal variations of the gram-negative bacteria. The major source
of these bacteria that we demonstrate is the natural environment. They
appear from early spring into summertime. Actually what we see in our
systems is that the sewage acts as a kind of a gigantic growth medium
where bacteria coming from the strains we see in vegetation are incu-
bated. They all grow in this very rich mixture which means that, in the
winter, the natural growth is suppressed.
-------
294 Wastewater Aerosols and Disease/Occupational Studies
There is an interesting parallel which is seen in fresh water lakes with
blue-green algae. There are reports in Sweden and Finland that people
suffer from algae disease. They have fever and winter-like symptoms,
and the incidents of these episodes correspond well with the growth of
bacteria in the late fall season and the early spring season; those bacteria
or algae were also seasonal.
-------
295
Interim Report on a Mortality Study of Former
Employees of the Metropolitan Sanitary District of
Greater Chicago
P.S. Gartside, B. Specker, P.E. Harlow, C.S. Clark
University of Cincinnati Medical Center
Department of Environmental Health
Cincinnati, Ohio 45267
ABSTRACT
In order to discover any adverse health effects among workers in the wastewater industry,
a mortality study of workers who were employed at the Metropolitan Sanitary District of
Greater Chicago during the 1%0's has been undertaken. This interim report is based upon
data from the complete employment records and death certificates of 402 decedents,
approximately half of the expected number. Proportionate mortality analyses of these
data have not shown any significant departures from expected death rates for several
major disease groupings, for the workers as a whole, for several employee subgroups, or
by length of employment.
Workers in the wastewater collection and treatment industry are ex-
posed to a wide variety of conditions which may have an adverse effect
on their health and well-being. These conditions result not only from the
presence of infectious biological agents and hazardous chemicals in
wastewater but also from physical hazards present in their workplace
environment. The safety record of the wastewater industry has long
been known to be one of the worst in this country (1). Most studies of
the health of wastewater workers have focused on risks due to biological
agents present in the wastewater. A review by Clark et al. (2) summa-
rizes many of the earlier studies. More recent studies of this type by
Rylander and Lundholm (3), Sekla (4), and Clark et al. (5) are reported
elsewhere in this Symposium. The Sekla study and studies by Kominsky
(6) and Elia et al. (7) also includes evaluations of some chemical expo-
sures; these studies are reported in this Symposium.
Another approach to the determination of the health effects of occu-
pational exposure to wastewater is to evaluate the causes of death of
former employees in the wastewater treatment industry. This approach,
known as a mortality study, has the advantage of potentially being able
to measure the cumulative combined effect, if any, of all the conditions
under which workers have labored during the course of their employ-
ment. Dean (8), reporting on a study by the University of Copenhagen,
concluded that Copenhagen sewer workers were dying earlier than con-
trols of comparable age; many of the sewer workers expired soon after
retirement. The study also revealed that deaths due to cancer of the
pancreas occured more often than expected, although a relatively small
-------
296 Wastewater Aerosols and Disease/Aerosol Suppression
number of death certificates were examined.
The present study is an application of the mortality study approach to
one of the largest wastewater treatment systems in the United States—
the Metropolitan Sanitary District of Greater Chicago (MSDGC). Apart
from its size and the corresponding large number of employees,
MSDGC is appropriate for such a study because it has been in existence
for more than a half century, and from its inception has operated its own
retirement system—the Sanitary District Employees' and Trustees' An-
nuity and Benefit Fund.
The protocol for this study required that the workers included in the
study had to have been employed by MSDGC at anytime during the
years 1960 to 1969. A roster of all workers who have met the protocol
has been compiled from records located in the MSDGC personnel office.
Pensions records, where available, have been obtained and reviewed,
and the vital status of each worker has been determined. Based on vital
statistics tables for the United States, it is expected that there should be
about 1075 decedents in the cohort by December 31, 1979. As of July,
1979, it has been determined that at least 704 members of this worker
group have deceased; death certificates have been located for 510 of
them. Of these, employment records have been located thus far for 402
employees. The data for this last group of workers have now been
analyzed, and preliminary results have been produced.
For each of the 402 decedents, the underlying cause of death has been
classified and coded by a qualified nosologist, according to the 8th Revi-
sion of the International Classification of Diseases (ICD) (9). For com-
parison, the distributions for age and cause of death among white males
in the State of Illinois for each year from 1960 to 1975 have been ab-
stracted from vital statistics tables of the United States. U.S. mortality
data for the years 1976 to 1979 have not yet been published; therefore, it
has been assumed that the distributions of deaths for these years are
similar to those for 1975. From these data, the observed numbers of
deaths and the expected numbers of deaths in five important cause-of-
death groupings for the 402 decedents have been tabulated and are pre-
sented in Table 1. These cause-of-death groupings are neoplasms (ICD
codes 140-209), heart disease (ICD codes 390-448), respiratory disease
(ICD codes 470-493), accidents (ICD codes E800-949), and other causes.
A chi-square statistic with four degrees of freedom, testing for signifi-
cant difference between the observed and expected frequencies, was not
significant (p = 0.20).
Table 1. Observed and Expected Numbers of Deaths (402 Workers)
Cause of death Observed Expected"
Neoplasms, all sites 90 781
Heart disease 227 238 6
Diseases of respiratory system 16 195
Accidents 9 139
All other causes 60 51 9
"For white males, State of Illinois, stratified by age and year of death (p = 0.20)
-------
P.S. Gartside, et al 297
In an attempt to determine whether length of exposure might have an
effect, the above data were subdivided according to years of employ-
ment with MSDGC, for those workers where this information was avail-
able. The chosen subdivisions for employment were 1 to 8 years, 9 to 16
years, and 17 or more years; the groups contained 64, 114, and 210
employees, respectively. The observed and expected numbers of deaths
for the above five disease groupings are given in Tables 2 to 4 for the
length-of-employment subdivisions. Chi-square statistics, each with
four degrees of freedom, for the three length-of-employment subgroups
resulted in p-values of 0.40,0.26, and 0.65, respectively, and showed no
outstanding differences between the numbers of observed and expected
deaths.
Table 2. Number of Deaths: 1-8 Years of Employment (64 Workers)
Cause of death Observed Expected"
Neoplasms, all sites 16 128
Heart disease 32 35 2
Diseases of respiratory system 1 2 8
Accidents 2 3.4
All other causes 13 98
"For white males, State of Illinois, stratified by age and year of death (p = 0 40)
Table 3. Number of Deaths: 9-16 Years of Employment (114 Workers)
Cause of death Observed Expected"
Neoplasms, all sites 24 22 2
Heart disease 71 66.3
Diseases of respiratory system 2 5.4
Accidents 1 4 5
All other causes 16 156
"For white males, State of Illinois, stratified by age and year of death (p = 0 26)
Table 4. Number of Deaths: 17 or More Years Employment (210
Workers)
Cause of death Observed Expected"
Neoplasms, all sites 47 40.8
Heart disease 120 129 0
Diseases of respiratory system 11 10.6
Accidents 4 5.4
All other causes 28 24 2
"For white males, State of Illinois, stratified by age and year of death (p = 0 65)
-------
298 \Vastewater Aerosols and Disease/Aerosol Suppression
To determine whether degree of exposure, as represented by type of
employment of MSDGC, showed any mortality effects, Tables 5 to 12
were prepared. These tables represent a subdivision of the workers into
four departments (Tables 5 to 8) and four job classification groups (Ta-
bles 9 to 12); each worker is classified into one of the four departments
and into one of the four job class groups. The departments are research
and development, engineering, maintenance and operations, and secu-
rity and safety, with 35, 44, 286, and 21 workers, respectively. The job
class groups are engineers and laboratory personnel, tradesmen, operat-
ing personnel, and laborers, with 55, 93, 122, and 85 workers, respec-
tively. Observed and expected numbers of deaths and chi-square statis-
tics with four degrees of freedom each were computed for these eight
groupings and resulted in the following respective p-values: 0.35, 0.50,
0.35, 0.85, for the department groups, and 0.70, 0.60, 0.45, 0.60 for the
jobs class groups. None of these are significant.
Table 5. Number of Deaths: Research and Development Employees
(35 Workers)
Cause of death Observed Expected"
Neoplasms, all sites 9 70
Heart disease 23 20 6
Diseases of respiratory system 0 1 7
Accidents 0 1 0
All other causes 3 4.7
"For white males, State of Illinois, stratified by age and year of death (p = 0.35)
Table 6. Number of Deaths: Engineering Employees (44 Workers)
Cause of death Observed Expected"
Neoplasms, all sites 13 86
Heart disease 25 26.6
Diseases of respiratory system 1 22
Accidents 1 1 3
All other causes 4 5.3
"For white males, State of Illinois, stratified by age and year of death (p = 0.50)
Table 7. Number of Deaths: Maintenance and Operations (286
Workers)
Cause of death Observed Expected"
Neoplams, all sites 61 56
Heart disease 161 168.7
Diseases of respiratory system 11 138
Accidents 7 10.3
All other causes 46 37 2
"For white males. State of Illinois, stratified by age and year of death (p = 0.35)
-------
P.S. Gartside, et al 299
Table 8. Number of Deaths: Security Guards, Safety, Etc. (21 Workers)
Cause of death
Observed
Expected"
Neoplasms, all sites
Heart disease
Diseases of respiratory system
Accidents
All other causes
0
0
11
26
79
07
03
11 7
"For white males, State of Illinois, stratified by age and year of death (p = 0.85)
Table 9. Number of Deaths: Engineers, Lab Staff, Etc. (55 Workers)
Cause of death
Observed
Expected"
Neoplasms, all sites
Heart disease
Diseases of respiratory system
Accidents
All other causes
13
35
2
1
4
105
335
27
1 7
66
"For white males, State of Illinois, stratified by age and year of death (p = 0 70)
Table 10. Number of Deaths Among Tradesmen (93 Workers)
Cause of death
Observed
Expected"
Neoplasms, all sites
Heart disease
Diseases of the respiratory system
Accidents
All other causes
24
51
5
2
11
18 1
555
46
32
11 7
"For white males, State of Illinois, stratified by age and year of death (p = 0 60)
Table 11. Number of Deaths: Operating Personnel (122 Workers)
Cause of death
Observed
Expected"
Neoplasms, all sites
Heart disease
Diseases of respiratory system
Accidents
All other causes
23
67
6
3
23
243
71 8
58
4 1
160
"For white males, State of Illinois, stratified by age and year of death (p = 0.45)
Table 12. Number of Deaths Among Laborers (85 Workers)
Cause of death
Observed
Expected"
Neoplasms, all sites
Heart disease
Diseases of respiratory system
Accidents
All other causes
23
45
1
3
13
243
484
40
32
11 1
"For white males, State of Illinois, stratrhed by age and year of death (p = 0 60)
-------
300 Wastewater Aerosols and Disease/Aerosol Suppression
The data was tabulated in Table 13 to compare with the finding re-
ported by Dean (8) that Copenhagen sewer workers were dying early in
retirement. Of the 402 decedents in our study, it was determined that 71
of them had retired from MSDGC. Of these 71, only 12 (17%) died
within 12 months of their retirement date; this contrasts with Dean's
report that 13 (41%) out of 32 died in the same calender year of their
retirement in Copenhagen. This difference between the two studies in
early death after retirement is significant at p = 0.019 by chi-square
statistic with one degree of freedom.
Table 13. Number of Deaths in Early Retirement
Chicago, Illinois
Within 12 months after retirement 12 (17%)
After 12 months of retirement 59
Copenhagen, Denmark
Within calendar year of retirement 13 (41%)
After calendar year of retirement 19
(p = 0019)
The final tabulation (Table 14) was made to determine if deaths due to
cancer of the pancreas occurred more often than expected and to com-
pare the results with the findings of Copenhagen study, which found that
cancer of the pancreas did occur often. Our data did not show an exces-
sive number of deaths due to cancer of the pancreas (p = 0.60).
In conclusion, in this preliminary study we did not find any outstand-
Table 14. Number of Deaths Due to Pancreatic Cancer
Observed 60
Expected" 4 4
"For white males, State of Illinois, stratified by age and year of death (p = 0.60)
ing frequency of deaths in the major subgroupings nor did we duplicate
the results reported by Dean. However, it should be noted that the
Copenhagen workers were exposed to the confined environments of
sewers while those in the present study were engaged in the relatively
more open environments of sewage treatment plants. Thus, the occupa-
tional exposures were not necessarily of the same type. The final report
of this study will include additional comparisons and should involve
more than twice as many death certificates as were available for this
interim report.
-------
P.S. Gartside, et al 301
References
1. WPCF Safety Committee and Staff Report. 1971. Wastewater collection and treatment
facilities—1970. Personnel safety survey. Jour. Water Poll. Control Fed., 43:335-337.
2. Clark, C.S., E.J. Cleary, G.M. Schiff, C.C. Linnemann, Jr., J.P. Phalr, and T. M.
Briggs. 1976. Disease risks of occupational exposure to sewage. /. Environ. Eng. Div.,
ASCE, 102:375-388.
3. Rylander, R., and M. Lundholm. 1979. Responses to wastewater exposure with refer-
ence to endotoxins. U.S. EPA Symposium on Wastewater Aerosols and Disease, Sept.
19-21, 1979. Cincinnati, Ohio.
4. Sekla, L., et al. 1979. Sewage treatment plant workers and their environment: A health
study conducted in Manitoba. U.S. EPA Symposium on Wastewater Aerosols and
Disease, Sept. 19-21, 1979. Cincinnati, Ohio.
5. Clark, C.S., G.L. Van Meer, P.S. Gartside, et al. 1979. Health effects of occupational
exposure to wastewater. U.S. EPA Symposium on Wastewater Aerosols and Disease,
Sept. 19-21,1979. Cincinnati, Ohio.
6. Kominsky, J., and M. Singal. 1979. Nonviable contaminants from wastewater. U.S.
EPA Symposium on Wastewater Aerosols and Disease, Sept. 19-21, 1979. Cincinnati,
Ohio.
7. Elia, V., V. Majeti and C.S. Clark. 1979. Worker exposure to organic chemicals at an
activated sludge plant. U.S. EPA Symposium on Wastewater Aerosols and Disease,
Sept. 19-21,1979. Cincinnati, Ohio.
8. Dean, R.B. 1978. Assessment of disease rates among sewer workers in Copenhagen,
Denmark. Environmental Health Effects Research Series. EPA-600/1-78-007. U.S.
EPA, Health Effects Research Laboratory, Office of Research and Development, Cin-
cinnati, Ohio.
9. U.S. Department of Health, Education and Welfare. 1975. 8th Revision (adopted for use
in the United States). Public Health Service Publication No. 1963. U.S. DHEW, Public
Health Service, National Center for Health Statistics, U.S. Government Printing Of-
fice, Washington, D.C.
-------
302
Suppression of Aerosols at a Wastewater
Treatment Plant
C. Lue-Hing, J. O. Ledbetter, S. J. Sedita, B. M. Sawyer,
D. R. Zenz, C. W. Boyd
ABSTRACT
The Metropolitan Sanitary District of Greater Chicago (MSDGC) is currently engaged in a
program to evaluate aerosol suppression devices at its John E. Egan Wastewater Reclama-
tion Plant. The conduct of this work by the MSDGC is in response to construction grant
conditions imposed by the U.S. EPA following protracted litigation relative to the charac-
teristics of aerosols to be emitted from the proposed O'Hare Water Reclamation Plant.
Windborne aerosol particles are formed from the evaporation of droplets which are in-
jected into the air by bubbles bursting at the air-water interface in wastewater aeration
basins.
The techniques which may be used to suppress aerosols can focus on: 1) the droplets
formed by the bursting bubbles or 2) the paniculate residues which are left after droplet
evaporation. Inertial impaction techniques may be applied to suppress the droplets
formed; classical air cleaning techniques may be applied to the particulate nuclei.
The MSDGC has proposed an evaluation of several techniques of suppression, includ-
ing: 1) bubble size reduction; 2) flat plates at the aeration tank surface; 3) partial covering
of the aeration tank surface; 4) particle collection at the tank surface and removal by
conventional scrubbers; 5) particle collection at the tank surface and removal by electro-
static precipitation; and 6) particle interception via a "green belt" or vegetative barrier. At
this time only the vegetative barrier or "green belt" has been evaluated experimentally.
Preliminary results indicate that the rate at which microorganisms are aerosolized and
emitted to the air from activated sludge aeration tanks is quite low and only a small
proportion of these organisms are of the indicator type. Further, the total microorganism
content of air immediately above the aeration tank liquid surfaces decreases exponentially
with height at least within the first 100 cm above the aeration tank liquid surfaces, and the
content appears to be influenced by factors such as the mixed liquor suspended solids
concentration of the aeration tanks, bacterial die-off, fallback of larger particles, and
dispersions by wind currents.
Although the scientific issues to be considered at this symposium may
be of national and even international significance, it is at this particular
time a question of special immediacy in the Chicago metropolitan area,
where construction of the O'Hare Wastewater Reclamation Plant
(OWRP) has just been completed and the facility is ready to be placed in
operation.
The O'Hare plant, located just inside the south boundary of the city of
Des Plaines, Illinois, is a facility with a treatment capacity of 75 mgd. It
is designed to receive and treat the combined sewage and storm flows
from a region known as the O'Hare or Upper Des Plaines Drainage
Basin of northwestern Cook County, in the Chicago metropolitan area.
Although the site is zoned industrial, the plant fence is just across Oak-
ton Street from the homes of residents of the city of Des Plaines, a fact
that has been the cause of a great deal of unhappiness and dismay on the
-------
C.Lue-Hifig,etal 303
part of some residents and officials of the city. Beginning in 1966, the
city carried on a running battle in the state and federal courts for a
period of 11 years in an effort to prevent the construction of the OWRP
on the site where it is now located.
The Metropolitan Sanitary District of Greater Chicago (MSDGC), the
regional agency that presided over the planning, design, and construc-
tion of the OWRP (with the aid of federal grant support), considered this
project an essential segment of the pattern of facilities required to com-
bat the mounting water pollution problems of the metropolitan Chicago
region. It fought with all of its vigor to prevent the O'Hare project from
being interrupted or sidetracked in the courts and to avoid or minimize
as much as possible the costly delays occasioned by protracted litigation
during a period of extreme inflation.
The battle was joined between the city and the MSDGC on a number
of legal issues in the various lawsuits, but the central issue presented
that is relevant to this symposium is whether the construction and opera-
tion of the OWRP at its present site would pose a health hazard to the
residents of the city by virtue of microbes and viruses emitted into the
atmosphere from the plant's aeration tanks.
Since the project would have an impact on the environment and fed-
eral funding was involved, an environmental assessment, full-scale pub-
lic hearings, and Environmental Impact Statements (EIS's) were all re-
quired, under the provisions of the National Environmental Policy Act
(1,2). Again, in the environmental assessment process, the question of
whether there was a health hazard to the residents of the city from
aerosols that would be emitted from the proposed plant became a central
issue; and many pages of the final EIS's are devoted to this question. In
the assessment process, with the city and the MSDGC in opposite posi-
tions, an intensive effort was made to gather such scientific evidence on
the question as was available at that time and to present it both orally
and in writing for inclusion in the EIS's.
The two-volume final EIS for the OWRP and solids pipeline was
completed in May 1975, by the United States Environmental Protection
Agency (U.S. EPA). A great many pages of the document are devoted to
the inputs of the city and the MSDGC on the health hazard question and
the analysis and conclusions reached by the EPA. As a part of the
process, the EPA itself conducted an extensive literature survey to de-
termine "the extent of the present knowledge on aerosol generation and
its health implications."
The conclusion of the EPA, as it is stated on page 5-9, Volume I of the
final EIS is as follows:
"It can be seen that there are innumerable factors which
control the viability and infection potential of microorganisms
commonly found in wastewater aerosols. To conclude that the
presence of these aerosols will positively result in a public health
hazard is not supported by scientific evidence. Since it is equally
unsupportable to reach a conclusion that a potential health
hazard does not exist for the residents in close proximity to Site
1, we find that in order to accomplish the intent and purpose of
the National Environmental Policy Act mitigative measures are
-------
304 Wastewater Aerosols and Disease/Aerosol Suppression
required to adequately suppress aerosol transmission from the
aeration tanks. Should evidence become available that these
additional facilities are not sufficient, we would require, and the
MSDGC has indicated its willingness to implement, whatever
additional mitigative remedies are necessary."
The litigation in the federal courts was concerned with resolving the
questions raised by the contentions of the city that this conclusion by
the EPA and the environmental assessment on which it was based were
not legally adequate. This question was decided against the city in the
U.S. district court and, on appeal, by the Seventh U.S. Circuit Court of
Appeals.
In its opinion, the federal appellate court said (in relevant part):
"We believe it is clear from the material of record that EPA
took the requisite hard look at this problem and reacted sensi-
tively to it. EPA summarized in its analysis the data available
(which was set out in full appendices) and stated its reasonable
conclusion that no definitive answer could be made to the ques-
tion of asserted health hazards from aeration. In response to
the mere possibility that such hazards might be present in unre-
gulated aeration, EPA took a conservative approach and re-
quired MSD to design, construct, and install devices to sup-
press aerosol emissions. The uncertainty regarding the very
existence and scope of the potential health hazard is ignored by
the City in its argument that the failure to specify standards and
specific devices renders the pertinent EIS inadequate and in its
insistence that the entire project be held in abeyance until defini-
tive answers and solutions can be obtained. We believe the EIS
unquestionably contains a fair statement of the problem and the
solutions intended, insofar as was possible, and we do not be-
lieve more was required in this case. ..."
Meanwhile, as a part of the parade of litigation, the city filed an
enforcement-type proceeding before the Illinois Pollution Control Board
(IPCB), in which it contended essentially that, in issuing the permit for
the construction of the OWRP, the Illinois Environmental Protection
Agency was violating state law "by threatening the (city's) environment
with air pollution in the form of odors, bacteria and viruses" that would
be emitted by the plant when it was built.
The IPCB dismissed the city's complaint as "frivolous", and this
ruling was affirmed, on appeal, by the Illinois appellate court.
In starting his opinion that the issue of a possible health hazard from
aerosols from sewage treatment plants in this kind of context was not a
proper subject for an enforcement proceeding before the board, Dr.
Zeitlin of the IPCB said:
"Were there a concerned need to now control aerosols from
sewage treatment plants, the proper forum would be the submit-
tal of a proposed regulation to the Board considering the fact
that the abatement of this possible emission would affect every
sewerage treatment plant in the State of Illinois, whether they be
existing, under construction, or proposed. "
-------
C. Lue-Hing, et al 305
No rulemaking proceeding has yet been initiated before the IPCB to
regulate aerosols emitted by sewage treatment plants.
The recommendations made in the final EIS as to the study of aerosols
and mitigating measures resulted in corresponding grant conditions im-
posed by EPA in connection with the construction of the OWRP. The
discussions we will be engaged in at this symposium will be concerned
with some of the research data generated in fulfillment of those grant
conditions and some of the resulting conclusions.
Specifically, this presentation will: 1) describe the aerosol suppression
study currently being conducted by the MSDGC; 2) discuss the rationale
behind the selection of the methods to be studied; 3) discuss the aerosol
suppression methods to be studied; and 4) present some of the pertinent
characterization data gathered thus far.
DESCRIPTION OF AEROSOL SUPPRESSION STUDY
The study involves physical, chemical, and biological characterization
of various treatment streams and aerosols generated from the aeration
tanks of the MSDGC's John Egan Water Reclamation Plant. In addition,
methods to suppress the aerosols generated from a pilot plant simulating
the Egan plant aeration tanks will be studied. The Egan plant was cho-
sen for study since it very closely approximates the OWRP in sewage
characteristics, method of sewage treatment, and physical configura-
tion.
The study is broken down into three phases. These phases are sepa-
rate and distinct entities, and each phase must be completed before the
next phase is begun. Perhaps more important is the condition which
requires that no phase of the project can be started unless shown to be
warranted by conclusions reached on the basis of data gathered in a
previous phase. A more comprehensive treatment of the experimental
program and work plan is available (3).
The following sections describe the general procedures to be followed
for sampling, sample analyses, and quality control during the course of
the study.
Physical and Chemical Parameters
A number of physical and chemical measurements will be made on the
raw waste water, the wastewater influent to the aeration tanks, and the
aeration tank mixed liquor of the first- and second-stage aeration tanks
of the Egan plant. The Egan plant is a two-stage activated sludge plant.
The first stage, which is designed principally for carbonaceous BOD
removal operates at mixed-liquor suspended solids (MLSS) concentra-
tions between 2,000 and 4,000 mg/1; the second stage, designed for bio-
logical nitrification, operates at MLSS concentrations between 1,000
and 2,000 mg/1. These physical and chemical measurements are listed in
Table 1.
Biological Parameters
Biological characterization of wastewater samples and mixed liquor
samples will consist of the biological parameters listed in Table 2.
Chemical Laboratory Quality Control
Prior to the start of the project, a series of distilled water standards
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306 Wastewater Aerosols and Disease/Aerosol Suppression
will be prepared and submitted to the chemical laboratory for analysis.
Five sets of duplicate samples of each parameter will be analyzed so that
the precision and accuracy of each analysis will be determined.
In order to evaluate the daily performance of the chemical laboratory,
quality control charts will be maintained for each chemical analysis. The
procedure for constructing quality control charts as outlined in the U.S.
EPA "Handbook of Analytical Quality Control in Water and Wastewa-
ter Laboratories" (1972) will be used.
In addition, monthly check samples will be prepared from certified
standards and analyzed during the course of the experimental program.
Bacteriological Quality Control
Internal bacteriological quality control will be conducted along the
lines of the following references:
• Environmental Protection Agency
Bacteriological Survey for Water Laboratories
EPA-103
• Handbook for Evaluating Water
Bacteriological Laboratories
EPA 67019-75-006
• Standard Methods for the Examination of Water and Wastewater 14th
Ed.
Table 1. Physical and Chemical Parameters for Aerosol Study
1. Total solids (TS)
2. Total suspended solids (TSS)
3 Total volatile solids (TVS)
4 Chemical oxygen demand (COD)
5 Alkalinity
6 Nontonic detergent
7. Methylene blue active substances (MBAS)
8. Total dissolved solids
9. Ammonia (NhU-N)
10 Total organic nitrogen (TON)
11. Orthophosphorus
12. Total phosphorus
13. Hardness
14 pH
15. Temperature
16 Dissolved oxygen (DO)
17. Chloride or other conservative indigenous ionic tracer
18. Viscosity
19. Surface tension
20. Bubble size
21. Bubble terminal velocity
Table 2. Biological Parameters for Aerosol Study
1. Total plate count (TPC)
2. Total colHormfTC)
3. Fecal coliform (FC)
4. Fecal streptococci (FS)
5. Klebsiella pneumonias
6. Salmonella
7. Pseudomonas aemginosa
8. Coliphage particles
9. Animal virus particle quantitatbn and, where specified, identification
-------
C. Lue-Hing,etal 307
Viral Analysis and Quality Control
Total viruses in raw sewage and mixed liquor will be analyzed by
means of an A1(OH)3, continuous-flow centrifuge technique (4). Basi-
cally, the procedure consists of adsorbing the indigenous viruses on an
A1(OH)3 precipitate, removing the precipitate from solution using a con-
tinuous-flow centrifuge, resuspending the precipitate, removing ad-
sorbed viruses with sonification and Freon 113, and again separating the
viruses by centrifugation. The virus-containing solutions will then be
analyzed by plaque assay procedures using three cell cultures: 1) BGM
(Buffalo Green Monkey) Kidney Cells; 2) WI-38 (Human Diploid Cell
Strain); and 3) PMK (Primary Monkey) Kidney Cells. All plaques
formed will be confirmed by repassage of the plaques in the same cell
system. Only those plaques showing cytopathic effect on repassage will
be registered as viruses in the virus assay. A representative selection of
confirmed viruses will be identified by serum neutralization.
Quality control in the virus laboratory will include extensive log keep-
ing, such as photographic records of the plaques formed in the first and
second passage and a census of the types of plaques which develop and
which are subsequently picked for repassage in the appropriate cell
system. In addition, seeded quality control samples will be prepared and
the seed viruses concentrated, isolated, and identified.
Quality Assurance Plan for Samplers
The air samplers employed in this project will be tested side by side
for a sufficient number of runs to statistically examine the variation in
collection efficiency among samplers. These runs will take place under a
variety of experimental conditions to ensure that data is gathered for the
wide range of operating conditions which will occur during the test
program.
Since it is not possible to autoclave the high-volume samplers, it will
be necessary to check periodically the sterilization procedures used by
running sterile distilled water through them and analyzing for biological
parameters 1 through 8 in Table 2.
For the times when the high-volume samplers are used for virus meas-
urements, sterility checks will be made prior to all runs to ensure that no
viruses are present.
Phase I
Phase I concentrates on defining the range of aerosol emissions that
are produced by the Egan plant and the associated process conditions
giving rise to these aerosol emissions. This is accomplished by measur-
ing the physical, chemical, and biological properties of aerosols emanat-
ing from the aeration tanks of the Egan plant and relating these to
measurements of the wastewater aeration process parameters and to
environmental parameters which may have an influence on the aerosol
properties. Work on Phase I is divided into six tasks ?s follows:
Task 1: A study of the diurnal and daily variation of the chemical and
biological quality of raw wastewater, mixed liquor, and first-stage and
second-stage aeration tank effluents of the Egan plant are to be con-
ducted. Three 8-hour composite samples will be collected on each of 4
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308 Wastewater Aerosols and Disease/Aerosol Suppression
consecutive days for 2 weeks. Grab samples of mixed liquor will also be
taken. All samples will be examined for physical and chemical parame-
ters 1 through 3, 8 through 10, 12 and 14 (Table 1) and biological parame-
ters 1 through 4, 6 and 7 (Table 2). Data pertaining to the physical,
chemical, and biological parameters will be analyzed statistically so that
subsequent wastewater sampling plans which depend upon the results of
previous tasks can be adjusted accordingly.
Task 2: This task is designed to complete the characterization of
wastewater and mixed liquor of the Egan plant which was begun in Task
1. However, this data, to be collected for a 30-day period, will include
additional mixed liquor samples, and physical and chemical parameters
1 through 21 (Table 1) and biological parameters 1 through 8 (Table 2). In
addition, on 6 days, samples of raw wastewater, first-stage effluent, and
mixed liquor from both aeration stages will be collected and analyzed
for animal viruses. The entire sampling program will be established
according to the results obtained in Task 1 to ensure that samples are
representative of the daily and diurnal variations.
Task 3: The purpose of this task is to estimate the range and variation
of the rate of emission, particle size distribution, and biological content
of aerosols emitted from point to point over the surface of the aeration
tanks of the Egan plant and to relate the aerosol properties observed
with the associated characteristics of mixed liquor.
On each of 15 days on which wastewater and mixed liquor are to be
collected during the period of Task 2, the aerosols present directly
above the aeration tank surface will be sampled with tyndallometers at
eight samping stations on each stage of the Egan plant. The aerosol
concentration and size distribution will be obtained.
On each of 5 days on which the tyndallometer measurements are
made, the biological properties of the aerosols will be determined with
Andersen six-stage and AGI samplers at three sampling sites on each
stage. These sites will be determined on the basis of previous tyndallo-
meter measurements. Andersen samples will be examined for biological
parameters 1 through 7 (Table 2), and AGI samples will be analyzed for
biological parameters 1 through 8 (Table 2).
Task 4: It is possible that aeration tank mixed-liquor solids concentra-
tions may have a significant influence on aerosol emission rates. There-
fore, tests will be conducted in a 15 ft deep column fitted with a diffuser
plate having a structure and porosity identical to the diffuser plates of
the OWRP and Egan plant. Mixed liquor will be withdrawn from the
Egan aeration tanks and diluted or concentrated to MLSS levels of 2,000
to 4,000 mg/1. Aeration rates will be adjusted to DO levels of 1 to 5 mg/1
for first-stage mixed liquor, and 2 to 6 mg/1 for second-stage mixed
liquor. A tyndallometer will be used to examine the concentration and
particle size distribution of aerosols emitted with various conditions of
MLSS levels and aeration rates.
Task 5: The purpose of this task is to ascertain whether animal viruses
are present in the Egan aeration tanks and whether viruses may be
detected as constituents in aerosols emitted from these tanks. A total of
10 high-volume samplers will be placed downwind of the Egan tanks,
but as close as possible to the edge of these tanks. Sampling times will
be on the order of 6 to 8 hours. The sampling fluid of all 10 samplers will
-------
C. Lue-H/ng,etal 309
be pooled for analysis and examined for animal virus content. One
upwind sample will act as a control.
In addition, a composite mixed liquor sample will be collected during
each aerosol sampling run. This sample will be a composite of samples
gathered in the inlet, outlet, and midpoint of each aeration tank and will
be analyzed for chemical parameters 1 through 21 (Table 1), and biologi-
cal parameter 9 (Table 2), animal virus.
Task 6: The purpose of this task is to establish the magnitude of the
site-specific factors for the application of a selected dispersion model to
be used in subsequent tasks of the study and to verify that the results are
consistent with experiences and applications of this model under similar
circumstances. A total of 30 aerosol sampling runs will be conducted.
During each aerosol sampling run, one aerosol station will be established
upwind of the aeration tanks of the Egan plant and six stations down-
wind at distances of 5 to 50 m. During each run, a high-volume sampler
and a six-stage Andersen sampler will be operated at elevations of 5 and
10 m above the ground. During each run, tyndallometer measurements
will be performed at each ground level sampling station. Sampling fluid
will be analyzed for biological parameters 1 through 8 (Table 2). The
Andersen plates will be analyzed for the biological parameters 1 through
7 (Table 2).
During each sampling run, a composite mixed liquor sample will be
collected at the inlet, outlet, and midpoint of each aeration tank. These
samples will be analyzed for physical and chemical parameters 1
through 21 (Table 1) and biological parameters 1 through 8 (Table 2).
Report—Phase I: The complete results of the work under Phase I will
be compiled into a report for review by MSDGC consultants and the
U.S. EPA. Phase II will not proceed until the report has been fully
reviewed and final direction for further work has been decided.
Phase II
Phase II will begin with the construction of a pilot facility representing
a 25 ft cross section of one channel of a standard aeration basin of the
OWRP. The pilot plant will be used to conduct a full-scale test of aerosol
suppression devices. The pilot plant aeration tank is designed to gener-
ate an aerosol particulate with physical and biological characteristics
similar to those actually emitted by the Egan and O'Hare plants. Mixed
liquor from the Egan plant will be fed to the pilot plant at detention times
similar to those in a 25 ft cross section of the tanks and then returned
back to the Egan plant.
The pilot plant will be equipped with five different aerosol suppression
devices which will be described in another section of this report.
Phase II will be conducted to determine whether the aerosol emissions
of the pilot plant are representative of the aerosol emissions from the
Egan plant. A total of 20 aerosol sampling runs will be performed.
During these runs, samples of the aerosol emissions of the pilot plant
and the Egan plant will be collected simultaneously. Aerosol sampling
runs will be scheduled to obtain measurements under varied environ-
mental conditions. Samples will be collected at ground level at one
upwind and six downwind locations of the Egan aeration tanks, and at
three locations immediately upwind over center and downwind of the
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310 Wastewater Aerosols and Disease/Aerosol Suppression
pilot plant. In each run, Andersen six-stage and high-volume samplers
will be employed along with tyndallometer measurements. In addition,
Andersen six-stage and AGI samples will be collected at an elevation of
5 m above ground immediately downwind of the Egan plant and the pilot
plant. During each run, composite mixed liquor samples will be col-
lected from the Egan plant and pilot plant. Sample collection fluid from
the high-volume samplers will be analyzed for biological parameters 1
through 8 (Table 1), while the Andersen samples will be analyzed for
biological parameters 1 through 7 (Table 2). Each mixed liquor sample
will be analyzed for chemical parameters selected on the basis of data
from Phase I and for biological parameters 1 through 8 (Table 2).
Report—Phase II: The findings of Phase II will be compiled into an
interim report. Again, this report will be reviewed by the U.S. EPA and
MSDGC consultants. Phase III, with the exception of the vegetative
barrier study, will not begin until a final determination is made as to the
direction to be taken based upon the conclusions and recommendations
of this report.
Phase HI
In this phase, the five aerosol suppression devices are to be tested on
the pilot facility. In addition, a study was included to determine the
efficiency of a vegetative barrier as an aerosol suppression device. This
vegetative barrier study was conducted on a laboratory scale using a
wind tunnel, and has been completed.
Pilot Plant Tests: Each of the five aerosol suppression devices will be
evaluated by operating trials utilizing the pilot plant. A total of 15 com-
plete performance trials of each system will be performed. The operat-
ing mode of the pilot plant is to be selected based upon data collected in
Phase II. Each performance trial will consist of two sampling runs: one
in which the aerosol emisisions of the pilot plant will be sampled without
the operation of the suppression technique, and the other during the
operation of the suppression device being tested. During each run, aero-
sol samples will be collected at one upwind station and six downwind
ground level stations at distances of 5 to 50 m from the pilot plant. A
high-volume and an Andersen six-stage sampler will be used at each
station. One Andersen six-stage sampler will also be located at an eleva-
tion of 5 m above ground at five downwind locations. Tyndallometer
readings will be taken at each station during a run. A composite mixed-
liquor sample of the pilot plant will be gathered for each run.
Sample collection fluid of the high-volume samplers will be analyzed
for biological parameters 1, 3, and 8 (Table 2). Andersen samples will be
examined for biological parameters 1 and 3 (Table 2).
Mixed liquor samples will be examined to determine physical and
chemical parameters 1 through 4, 6 through 8, and 17 (Table 1) and
biological parameters 1,3, and 8 (Table 2).
Report—Phase III: At the completion of Phase III, the District will
prepare a complete draft final report of the project. Recommendations
will be presented regarding the method or combination of methods con-
cluded to be the most effective and reliable, considering estimated capi-
tal and operating costs, for suppression of aerosol emissions of aeration
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C. Lue-Hing, et al
311
facilities at the OWRP, with related proposed detailed design criteria.
The report will review the facilities and methods employed, review all
experimental and test data, perform analyses of data and results, and
conduct a full comparison and discussion of the performance, reliabil-
ity, and estimated costs of each alternative aerosol suppression tech-
nique examined during the project.
Aerosolization Process
The typical process whereby aerosols are generated in a wastewater
treatment plant aeration tank can be characterized as follows (Figure 1)
(5,6,7,8):
1. A 600(j.m diameter bubble rises to the surface of the aeration tank.
2. The bubble bursts and ejects about 5 droplets of 60(j,m diameter.
3. The droplets rise to a height of about 8 cm above the surface.
4. The droplets evaporate to form windborne aerosol particles.
These windborne aerosol particles exhibit equivalent diameters of
about 12 (j.m microscopically and 6 fjim aerodynamically, as character-
ized by the Andersen six-stage sampler. Based on the above particle
characteristics, it can be inferred that the particles are very flocculent
and have a low bulk density of about 0.25 g/cm3.
6um DIA
Particles
Figure 1. Section of Aeration Tank Showing Formation of Droplets and
Airborne Particles
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312 Wastewater Aerosols and Disease/Aerosol Suppression
Rationale for Methodologies and Techniques
The methodologies or techniques which may be considered for sup-
pression of aerosols from wastewater aeration tanks are as follows:
• suppression of the droplets which are ejected from the surface of the
wastewater by the bursting bubbles
• suppression or capture of the solid particle residues left after evapora-
tion of the droplets
Suppression of the droplets would best be accomplished by inertial
impaction devices whereas collection of the solid particulate residues
would be more amenable to classical air cleaning principles other than
inertial impaction.
DEVICES FOR SUPPRESSING AEROSOLS
Devices Considered
Many devices or alternations in the treatment process have been pro-
posed for the suppression of aerosols from wastewater treatment plants.
A listing of these is presented here to indicate the difficulty involved in
the task of choosing an appropriate suppression system (Table 3).
At-the-Surface Suppression: Not all of the methods proposed would
necessarily have the same probability of success. For example, Wood-
cock and others (6,7) have shown that ejected droplets are about one-
tenth the diameter of the bubble from which they originate. Thus, it
should be possible, theoretically, to reduce the bubble sizes to such an
extent that the resulting droplets and particles would be too small to
carry any microorganisms. Reduction in bubble size, while attractive in
its simplicity, is not a practical approach to aerosol suppression. In
theory, it should be possible to produce oxygen bubbles so small that
they would dissolve completely before reaching the surface. Such bub-
bles actually pick up other dissolved gases during their travel, however,
and do not disappear.
Of the various types of floating covers which have been proposed for
droplet suppression, all have drawbacks which eliminate them as useful
candidate systems for actual testing. The expense of tall oil and its
potential for degrading effluent quality, and the foaming characteristics
of detergents eliminate them from consideration. Expanded plastic foam
such as polyurethane could be made to float on the surface and repre-
sents a better candidate than either tall oil or detergents. The plugging of
the polyurethane matrix, however, would necessitate frequent replace-
ment as the material would not be cleanable. The use of ping-pong balls
as a floating cover to suppress droplet emission is intuitively attractive
because of its simplicity. Such a cover would be self-cleaning, and long-
lasting, although less efficient than a polyurethane foam float. Unfortu-
nately, ping-pong balls tend to travel with the flow and pile up at the end
of the channel; they do not stay evenly distributed over the surface.
Above-the-Surface Suppression: Above-the-surface methods for
droplet suppression would appear to have the greatest probability of
success, although a number of methods proposed have serious limita-
tions. Multiple-layer or knitted mesh screens would probably be more
efficient than single-layer screens, but would be more difficult to clean.
Fiber bed filters, while theoretically very efficient, would plug up due to
-------
C. Lue-Hing, et al 313
accumulation of solids. Polyurethane foam used as a filter would again
be subject to plugging and require frequent replacement. The use of
overlapping flat plates (such as those found in awnings) appears to be a
good candidate for inertial impaction of the droplets as does the use of
properly spaced spray nozzles. The use of a high-speed rotating brush to
capture droplets before evaporation, while imaginative, is not very
practical.
Table 3. Suppression Devices Considered
Droplet suppression techniques
At-the-surfaoe methods
Bubble size reduction - smaller plate size,
not practical
Floating covers
Oil - surface tension reduction - tall oil
Collapsing foam - detergent
Permanent foam - polyurethane sheets
Ping-pong balls - floating on surface
Above-the-surface methods
Single layer screen -100-200 mesh
Multiple layer or knitted mesh screen
Fiber beds
Foam or granular bed
Flat plate
Water spray
Rotating brush
Evaporated particle suppression by collection
At-the-canopy
Sedimentation
Multiple cyclone
Scrubber
Electrostatic precipitator
Fabric filtration
Downwind of the tank - vegetative barrier
Suppression by Collection: Under a canopy placed over the area
where the bubbles burst, sedimentation could be an effective suppres-
sion mechanism. Due to the slow rise velocity of the air under the
canopy, many of the particles would settle back into the water. A multi-
ple-cyclone could collect particles under the canopy; however, due to
their flocculent nature, they might be crushed into smaller particles and
reentrained. A low-energy scrubber attached to the exhaust stream from
the canopy would have a good probability of success as would the use of
an electrostatic precipitator. Fabric filtration (bag filters) would have a
very high collection efficiency, and be relatively uncomplicated; how-
ever, the size requirements for such an installation at already crowded
facilities might preclude their use.
The only method proposed to intercept particles downwind of the
tank is a "green belt" or vegetative barrier. Thus far, this is the only
method which has been examined experimentally. The results of these
experiments are presented elsewhere in these proceedings under the title
"Effectiveness of Aerosol Suppression by Vegetative Barriers" (J.C.
Spendlove).
From the preceding discussion, it is obvious that although many meth-
ods were proposed, only a few methods were worth serious considera-
tion. A total of five (excluding the vegetative barrier) techniques were
-------
314 Waste water Aerosols and Disease/Aerosol Suppression
chosen for further consideration from among all of those proposed.
Included in the list were two inertial impaction techniques, two under-
the-canopy techniques, and one disinfection device which was not con-
sidered under the physical methods proposed.
Devices Chosen for Complete Testing
The following is a list of the devices which the MSDGC has chosen
for further testing along with a brief description of each (Table 4).
Inertial Impaction Devices:
• Slats over the tank (Figure 2)
The system consists of two layers of overlapping slats suspended over
the entire aeration tank surface. Each slat should be 4 to 8 in wide.
The lower layer should be no more than 4 to 6 in above the surface of
the water, the closer the better, with the upper layer 1 in above the
lower layer. The slats may be corrugated for support.
• Water spray (Figure 3)
This system should consist of a sprinkler system with spray nozzles
designed to produce water droplets of from 50 to 300 (im diameter.
The nozzles are positioned so that the resulting spray completely
covers the tank 12 in above the surface.
Particle Suppression or Collection Devices:
• Parabolic cover over diffuser plate area (Figure 4)
The system consists of a fiberglass or metal canopy extending 8 ft
over the aeration tank surface to cover the diffuser plate area. Both
edges of the cover are submerged. The top of the cover should be 2 to
4 ft above the surface of the water at its highest point. There is an
exhaust manifold along the entire length, venting into a single dis-
charge point.
• Parabolic cover with electrostatic precipitator (Figure 5)
This system is identical to the parabolic cover system described above
(Figure 4), with the addition of an appropriately sized electrostatic
precipitator mounted on the discharge side of the canopy exhaust
vent.
• Ultraviolet lights (Figure 6)
This system should consist of approximately 56 30-watt UV lamps
arranged in four rows over each aeration tank. Each lamp is 36 in long
with reflectorized fixtures and is suspended 3 ft above the surface of
the water. Each fixture should contain two lamps and be wired so that
either or both lamps can be operated.
The MSDGC proposes to test each of these devices on a pilot plant
which represents a full-scale cut through one of the aeration tanks.
Design criteria for construction can be developed from the results of
these tests, should this be necessary.
Table 4. Suppression Devices Chosen For Complete Testing
Inertial impaction devices
Slats over the tank
Water spray
Particle suppression or collection devices
Parabolic cover over diffuser plate area
Parabolic cover with electrostatic precipitator
Ultraviolet lights
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C.Lue-Hing,etal
315
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-------
316
Wastewater Aerosols and Disease/Aerosol Suppression
AERATION TANK
MANIFOLD
DISCHARGE
SECTION AS SHOWN ABOVE
Figure 4. Parabolic Cover
Preliminary Results
The primary goal of Phase I of the aerosol study is to characterize the
existing aerosol emissions from the aeration tanks at the Egan plant with
the main emphasis on microbial emissions. A number of sampling runs
have been conducted directly over the aeration tanks in order to define
the source strength emission rate of aerosols.
-------
C. Lue-Hing, et al
317
AERATION TANK
MANIFOLD
DISCHARGE
Figure 5. Parabolic Cover with Electrostatic Precipitator at Discharge
Figure 7 presents the results of one such sampling run. Samples were
collected with Andersen six-stage viable samplers positioned at ground
level 0.3 meters over the liquid surface of the first-stage aeration tanks
at a number of locations along the length of the tank. A total plate count
analysis was performed on all samples collected. As can be seen, total
plate count concentrations ranged from 866 to 1420 colonies/m3 air over
the tanks. A sample collected at the same time 15m upwind of the tanks
showed 284 colonies/m3 air.
Figure 8 presents similar data collected above the second-stage aera-
tion tanks. One difference, though, is that these samples were collected
at a height of 2.4 m above the liquid surface. This height was chosen for
this sampling run because the liquid level of the second-stage aeration
-------
318 Waste water Aerosols and Disease/Aerosol Suppression
(Not to Scale)
Di»
-------
C. Lue-Hing, et al
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
319
Tank I <
Tank 2 '
58
51 155 103
MEAN = 120/m3 245 110
19
7-0'
UPWIND BACKGROUND = 89 (SAMPLES COLLECTED 15 METERS FROM TANKS)
NOTE- ALL SAMPLES COLLECTED 2.4 METERS ABOVE WATER SURFACE
WITH ANDERSEN 6-STAGE VIABLE SAMPLERS.
Figure 8. Bacterial Concentration in Air Above Stage 2 Aeration Tanks
(All values expressed as colonies/m3 air)
tanks is actually 2.4 m below ground level in order to allow for gravity
flow of wastewater through the treatment plant. Thus, the sample was
actually taken at ground level. As can be seen, the total count concentra-
tion ranged from 51 to 245 colonies/m3 air at 2.4 m above the liquid
surface. Although the data shown in Figure 8 were not collected on the
same day as those shown in Figure 7, there appears to be a significant
decrease in the bacterial concentration at this slightly increased height
above the liquid surface.
These findings led to the decision to conduct another set of experi-
ments in which the effect of height above the liquid surface was exam-
ined more closely. Andersen six-stage viable samplers were positioned
approximately 7, 12, 32, 48, 73, and 99 cm above the liquid surface of the
aeration tanks and operated simultaneously.
Figures 9 and 10 present the results of these sampling runs above the
first stage and second-stage aeration tanks, respectively. These figures
indicate that there is an exponential decrease in the bacterial concentra-
tions in air within the first 100 cm above the liquid surface. Counts
decreased from 1766 colonies/m3 air to 462 colonies/m3 air over the first-
stage and from 769 colonies/m3 to 189 colonies/m3 over the second-
stage. This decrease in concentration is probably due to a number of
factors, including bacterial die-off, fallback of larger particles, and dis-
persion by wind currents.
The data presented thus far have dealt with total plate counts col-
lected with the Andersen six-stage viable samplers. On a limited number
of days, comprehensive bacterial analyses have been done on the An-
dersen sampler plates in order to study the occurrence of indicator
organisms in the air. The results of the most comprehensive run thus far
-------
320
Waste water Aerosols and Disease/ Aerosol Suppression
o
I-
o
o
CE
LLJ
O
<
CQ
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
2000
O
1000
900
800
700
600
500
400
300
200
100
O
Note: Upwind background distance
from source (15m )= 17lcol./mJ
10 20 30 40 50 60 70
HEIGHT ABOVE LIQUID SURFACE (cm)
80 90 100
Figure 9. Bacterial Concentration in Air Versus Height Above Liquid
Surface in Stage 1 Aeration Tanks (Samples collected with
Andersen six-stage viable samplers)
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
z
UJ
o
z
O
o
1000
900
800
700
600
500
400
300
200
100
O
Note: Upwind background distance
from source (15m) = 97col./m3
O
10
20 30 40 50 60 70 80 90 100
HEIGHT ABOVE LIQUID SURFACE (cm)
Figure 10. Bacterial Concentration in Air Versus Height Above Liquid
Surface in Stage 2 Aeration Tanks (Samples collected with
Andersen six-stage viable samplers)
-------
C. Lue-Hing, et al
321
are presented in Table 5. This table compares the bacterial counts in an
air sample collected directly above the first stage aeration tanks with
those collected 10 m upwind of the tanks with respect to both indicator
organism content, and their distribution within each stage of the Ander-
sen sampler. Six indicator organisms were examined in addition to total
plate count. The most important points to note are that: 1) although the
total plate count above the aeration tank was 551 colonies/m3 air, the
combined count of all the indicator organisms was only 30 colonies/m3
air, or roughly 5% of the total; and 2) while the background air samples
were taken only 10 m upwind from the aeration tanks, they were nega-
tive for indicator organisms.
Table 5. Comparison of Bacterial Concentrations in Air 0.3m Above
Stage 1 Aeration Tanks and Upwind Background
Colonies/m3 air for each Andersen sampler stage
Organism" Stage 1 Stage 2 Staged Stage 4 Stages Stage 6 Total
TPC
TC
FC
FS
K
S
P
157(90)"
2( 0)
2( 0)
0(0)
2(0)
0( 0)
0(0)
114(46)"
2(0)
0(0)
2(0)
0( 0)
0(0)
0(0)
118(37)"
1(0)
2(0)
0(0)
0( 0)
0(0)
0(0)
75(54)"
2(0)
1(0)
1(0)
2(0)
0(0)
1(0)
67 (54)"
1( 0)
1( 0)
4(0)
1(0)
0(0)
0(0)
20(39)"
1(0)
2( 0)
0(0)
0(0)
0( 0)
0(0)
551(320)"
9( 0)
8( 0)
7( 0)
5( 0)
0( 0)
1( 0)
"TCP = total plate count; TC = total coliform; FC = fecal coliform; FS = fecal streptococci; K
Klebsiella pneumoniae; S = Salmonella; P = Pseudomonas aeruginosa
"Background values (in parentheses) determined 10m upwind from tanks
In order to gain a further perspective on the low rate of bacterial
emissions actually emanating from the aeration tanks, the data in Table
6 is presented. This table shows the bacterial concentrations measured
in the first stage mixed liquor at the Egan plant at the same time that the
air sample data presented in Table 5 was collected. As can be seen,
bacterial concentrations in the mixed liquor as expressed by total plate
count are in the range of 108 counts/100 ml of mixed liquor. The most
prevalent indicator organisms, such as fecal coliform and fecal strepto-
Table 6. Bacterial Concentrations in Stage 1 Aeration Tank Mixed
Liquor at the John Egan Water Reclamation Plant
Counts/100 ml"
Station
Influent
TPC
5.8x10*
TC
1.3x10*
FC
1.5x10*
FS
4.7x10*
K
0/4"
S
2.2x10'
P
2.8X103
CPH
3.3x10'
Midpoint 6.2x10* 46x10' 24x10* 3.9x10* 1/4" 4.6x10' 2.2x10= <3.0x10'
Effluent 9.1x10* 3.4x107 1.3x10* 6.0x10* 2/4" 1.2x10' 4.6x10* 70x10'
"TPC = total plate count; TC = total coliform; FC = fecal coliform, FS = fecal streptococci, K =
Klebsiella pneumoniae; S = Salmonella; P = Pseudomonas aeruginosa; I CPH = cdiphage particles
"0 Confirmed out of 4 colonies picked
-------
322 Wastewater Aerosols and Disease/Aerosol Suppression
cocci in the aeration tank mixed liquor, are in the 106 counts/100 ml
range. Thus, the data in Table 5 indicate that the rate at which microor-
ganisms are aerosolized and emitted to the air from the aeration tanks is
indeed very low.
CONCLUSIONS ON PRELIMINARY RESULTS
Although the results presented here are preliminary with respect to
the total work load for all three phases, they are, however, relevant to,
and consistent with, the prinicipal mission of Phase I, which is designed
to:
"Measure the physical, chemical and biological properties of
aerosols emanating from the aeration tanks of the Egan WRP
and relate these to measurements of the wastewater aeration
process parameters of the plant, and environmental parameters
which may have an influence on the aerosol properties. . . . the
performance characteristics of the Egan WRP being presumed
to be representative of the planned operation of the O'Hare
WRP."
Based on the data herein presented, the following conclusions are made:
• The rate at which microorganisms are aerosolized and emitted to the
air from activated sludge aeration tanks is quite low, and only a small
proportion of these organisms are of the indicator type.
• The concentration of total background microorganisms is highly vari-
able and range from about 100 to 300 colonies/m3 air for distances up
to 15 m upwind from the aeration tanks.
• The total microorganism content of air immediately over the aeration
tank liquid surfaces:
1. decreases exponentially with height at least within the first 100 cm
above the aeration tank liquid surface
2. approaches background concentrations by extrapolation of current
data within 2.5 to 4 m above the aeration tank liquid surface
3. appears to be influenced by several factors, including the mixed-
liquor suspended solids concentration of the aeration tanks, bac-
terial die-off, fallback of larger particles, and dispersion by wind
currents.
References
1. The Metropolitan Sanitary District of Greater Chicago. 1975. Environmental Assess-
ment for O'Hare Wastewater Treatment Plant. December 19, 1975.
2. U.S. Environmental Protection Agency. 1975. Environmental Impact Statement for
O'Hare Wastewater Treatment Plant, May 6,1975.
3. Metropolitan Sanitary District of Greater Chicago. 1978. Detailed Work Plan—O'Hare
Water Reclamation Plant Aerosol Suppression Study. Submitted by the Metropolitan
Sanitary District of Greater Chicago, Department of Research and Development in
Partial Fulfillment of the Step 1 Grant Amendment for U.S. EPA Grant No.
C175111-02. April, 1978.
4. Metropolitan Sanitary District of Greater Chicago and IIT Research Institute. 1979. Viral
and bacterial levels resulting from the land application of digested sludge. EPA-600/
1-79-015. U.S. Environmental Protection Agency.
5. Glazer, J.R., and J.O. Ledbetter. 1967. Sizes and numbers of aerosols generated by
activated sludge aeration. Water And Sewage Works, 114:219-221.
-------
C. Lue-Hing, et al 323
6. Randall, C.W., and J.O. Ledbetter. 1966. Bacterial air pollution from activated sludge
units. Am. Indust. Hygiene Assoc. Jour., 27:506-519.
7. Woodcock, A.H. 1955. Bursting bubbles and air pollution. Sew. Ind. Waste, 27:1189-
1192.
8. Knelman, F.,etal. 1954. Mechanism of the bursting of bubbles. Nature, 173:261.
DISCUSSION
MR. SCHWARTZ: I have read that one of the common occurrences
at activated sludge treatment plants is that operators will sometimes
overaerate their wastes. I wonder if it would be possible to conduct a
study showing that you can diffuse at a minimum rate and cut down on
the amount of bursting bubbles that occur?
DR. LUE-HING: My answer to your question is we are interested in
reducing air usage because by reducing air usage, we reduce costs. The
costs of energy today is such that we can't ignore any procedure that
will cut our costs down. In fact, within the R & D Department we are
currently conducting a study aimed at maintaining effective wastewater
treatment at reduced aeration rates, but not because of aerosols; it costs
too much to pump air through sewage. We are about halfway through
this study, and we are coming up with some recommendations which tell
us that we can use less air. Our reasoning for this is not aerosol; it is just
plain money.
MR. SCHWARTZ: In the event that you go through with studying
ultraviolet light as a suppression method, do you have a maintenance
technique for keeping the light screened so as not to be covered with
participate matter?
DR. LUE-HING: I am glad you asked that because we have about 5
or 6 years of experience with ultraviolet lamps on a much less hostile
situation, using microscreens, where we don't have the splashing. We
eventually got rid of them because we couldn't maintain them, and they
were just a few 6 ft lamps. We are now talking perhaps about 3000 ft
lamps per tank. However, we plan to take a look at it if we get that far.
-------
324
Effectiveness of Aerosol Suppression by Vegetative
Barriers
J.C. Spendlove, R. Anderson, S.J. Sedita, P. O'Brien,
B.M. Sawyer and C. Lue-Hing
The Metropolitan Sanitary District of Greater Chicago, Illinois
ABSTRACT
Concern about potential public health hazards of microbial aerosols emanating from
wastewater treatment aeration tanks prompted the U.S. Environmental Protection Agency
to ask the Metropolitan Sanitary District of Greater Chicago to characterize aerosol emis-
sions and investigate ways to suppress them. One technique studied to date for suppress-
ing these aerosols involves reduction by filtration or aerosol dispersion and dilution, based
on the densities of coniferous and deciduous vegetation planted around treatment basins.
The extent of filtration as a function of vegetation density and wind speed was studied in a
low-speed wind tunnel. Filtration effectiveness was determined by reduction in aerosol
concentrations of Bacillus subtilis var. niger, disseminated as particles of similar size to
those emitted from treatment plants. Data collected experimentally were combined with
those values reported in the literature for vertical mixing and dilution created by barriers.
Results indicated that the maximum reduction possible in aerosol concentration and mass
median diameter (MMD) of particles by filtration was 50% when type and density of the
barrier together with wind speed were considered. By contrast, the literature suggested
that dispersion rather than filtration would be the principal mechanism involved for vege-
tative barriers in suppressing aerosols by orders of magnitude. Our results indicate that
strategically placed vegetation should effectively suppress aerosols emanating from waste-
water treatment facilities.
Aeration basins of wastewater treatment facilities may serve as
source of statistically significant concentrations of microbial aerosols.
These aerosols are primarily generated through the bubble-breaking
mechanism described by Blanchard and Syzdek (1). Their production is
caused by the extensive use of aerators. Aerosols thus produced contain
viable microorganisms, some of which are potential pathogens.
Microbial aerosols emitted from sewage treatment plants have been
studied by several investigators (2-6). Kenline and Scarpino (5) found
particles of these aerosols to be in a size range of 1 to 20 jam in diameter.
It has been shown by Parker et al. (7), that the viability of such airborne
microorganisms may be sufficient to allow their transport several kilo-
meters downwind of wastewater treatment facilities.
A variety of means by which such aerosols might be suppressed have
been proposed and some are under consideration as part of a U.S. EPA-
funded study by the Metropolitan Sanitary District of Greater Chicago.
Examples include: 1) thin metal strips mounted in layers over the aera-
tion surface; 2) deflector covers over the diffuser area; 3) water spray to
intercept droplets; and others. Another alternative involving relatively
-------
J. C. Spendlove, et al 325
economical implementation and maintenance, entails planting a vegeta-
tive barrier of trees and shrubs around the aeration basins. In addition to
the increased mixing and dilution of aerosol resulting from deformation
of air streamlines at the vegetative barrier, it was expected that some
filtration would occur as the aerosols passed through the vegetation. If
aerosol suppression of vegetation were effective, these barriers could be
strategically placed around wastewater treatment facilities to provide
aerosol reduction through a combination of mixing/dilution, and
filtration.
The purpose of this study, then, was to examine the aerosol filtering
capacity, as a function of wind speed, among various densities of both
coniferous and deciduous vegetation and to conduct a survey of the
literature on the effects of such a barrier on vertical mixing and dilution
of aerosol. It was felt that from the experimental data and the surveyed
dilution effects, an overall aerosol suppression effect of vegetative bar-
riers could be synthesized.
Experimental Methods
The experimental portion of this study was performed in a low-speed
wind tunnel, the Atmospheric Simulation Facility (ASF), located at Cal-
span Corp., Buffalo, New York. A photograph and schematic drawing
of the ASF are shown in Figure 1. The facility is 24 m long, 1.8 m high,
and 2.4 m wide. A large fan at one end of the ASF draws air through the
tunnel. The facility was initially designed, and is primarily used, for
scale tests of atmospheric turbulence and diffusion.
Aerosols of Bacillus subtilis var. niger(BG), a common tracer organ-
ism, were generated near the inlet end of the ASF using a commercially
available Perkin-Elmer Atomizer shown in Figure 2. This device was
chosen because it produces minimal stress without reprocessing the
bacterial slurry. Particle size distributions as well as the quantity of fluid
atomized could be varied. By adjustment, the atomizer was operated to
produce aerosol similar in size to those emitted from treatment facilities,
with a MMD of 7 jim, as determined by characterizations with the
Andersen sampler (8).
In an effort to provide a uniform bacterial aerosol distribution
throughout the cross-sectional area of the ASF, two atomizers were
used simultaneously. Additionally, thorough mixing of the aerosols with
inlet air was induced through the deployment of a grid placed upwind of
the atomizers. The grid was designed to provide small but sufficient
turbulence to produce the desired mixing. With the above procedures,
typical airborne concentrations of about 3.5 -x 10s viable aerosol parti-
cles/m3 of air were achieved. Aerosols thus produced were drawn down
the tunnel and through various densities and types of vegetative filters.
The bacterial aerosols were characterized in planes perpendicular to
the air flow both upwind and downwind of the vegetative niters by
Andersen samplers containing standard methods agar and all-glass im-
pingers, as shown in Figure 3. Sampling intervals of 1 or 2 min resulted
in near optimum collections of bacteria for characterization with the
Andersen samplers.
Andersen sampler plates were incubated at 30° for 12 to 18 hours.
Using a relationship described by Andersen (8), the actual concentration
-------
326
Wastewater Aerosols and Disease/Aerosol Suppression
A = atomizers/mixer
B = filter/characterizers
C = characterizes
TEST SECTION
NOMINAL SIZE =18m HIGH X2 4 m WIDE
FLOW
DEVELOPMENT
REGION
152 HI
Figure 1. The Calspan Atmospheric Simulation Facility (ASF)
of particles was determined for each stage from the 'positive hole
count.' These results allowed determinations of the absolute concentra-
tion (sum of concentrations in each size range) and the MMD of the
aerosol.
Density, as well as type of vegetation, was varied in order to examine
the influence of these parameters on the filtration efficiency of the vege-
tative filters as shown in Figures 4a and 4b. One type of evergreen, the
White Spruce (Picea glaucd), and two types of deciduous vegetation, the
-------
J. C. SpendJove, et al
327
©
1 Knurled Knob
2 Masher
3 Sample Tubing and
Capillary Assembly
4 S pring
5 O-r ing
6 Insert
7 Nebulizer Body
8 Venturi
9 Rear End Cap
10 O-ring
11 O-ring (2)
12 Locking Ring
Figure 2. Exploded View of Atomizer
UPWIND
B
D
A
n
o
DOWNWIND
D
CO
C
CO
CD
Figure 3. Approximate Positions Within the Cross-Section Rane of the
ASF Perpendicular to the Air Flow of Andersen Samplers (n)
and All-Glass Impingers (o) Upwind and Downwind of
Vegetative Filter
-------
328 Wastewater Aerosols and Disease/Aerosol Suppression
Figure 4a. Construction Stage of Vegetative Filter
Figure 4b. Lateral View of Completed Vegetative Filter
-------
J. C. Spendlove, et al 329
Cottonwood (Populus deltoldes), and the Black Willow (Salix nigra)
were used in the trials. The vegetative filters were constructed on a wire
grid across the entire cross section of the tunnel such that there were no
obvious 'holes'. Variation in density of vegetation was achieved by the
use of multiple vegetative filters stacked along the length of the ASF. A
maximum of six vegetative panels were used. Vegetation for these filters
was cut fresh at the beginning of each day, and each piece was supplied
with a partially water-filled balloon tied to the cut stem to keep it in fresh
condition during the trials. Particular species of each vegetation type
were chosen on the basis of range, common to both the Chicago and
Buffalo areas and on the basis of availability.
Wind speeds in the tunnel were varied to simulate those expected
within the forest canopy. Normally, four different wind speeds of 0.4,
1.8, 3.1, and 4.9 m/sec were used for each filter arrangement.
Experimental Results
A total of 41 trials were conducted in the ASF. Of these, 20 actually
represent the basic experimental data. The remaining 21 were prelimi-
nary trials performed to evaluate aerosol generation and characteriza-
tion techniques as well as to assure that background counts of bacteria
were not of sufficient levels to create interference.
The trials may be segregated into two groups based upon the type of
vegetation used in a particular trial, either deciduous or evergreen. Be-
yond this basic segregation, other important experimental parameters
that were considered were wind speed and vegetation density. The
higher the wind speed the more likely particles will be filtered by impac-
tion on vegetation elements.
While the decrease in aerosol concentration across the filter was an
indication of filter efficiency, information on filter efficiency was also
gained from measures of the change in MMD of aerosol spectra. The
impaction mechanism which was expected to be responsible for remov-
ing most of the microbial aerosols should exhibit a dependence on aero-
sol particle size. That is, greater portions of the larger particles (>5 (j.m
diameter) than of the smaller particles (<5 fxm diameter) should be
filtered by impaction. If such an occurrence were observed during the
trials, the MMD of the aerosols would decrease due to the resulting
smaller proportion of the total spectrum represented by larger particles.
Background counts of bacteria, performed before and after each se-
ries of tests with the vegetation in place, conclusively indicated that no
bacterial particles were being reentrained from the surfaces of the
vegetation.
Trials performed with Cottonwood resulted in a low filtration effi-
ciency for microbial aerosols as indicated by low concentration reduc-
tion, shown in Figure 5. A maximum reduction for this type of vegeta-
tion of about 15% was achieved at the two intermediate wind speeds. At
either extreme of the wind speed, no reduction in bacterial aerosol con-
centration was observed across the vegetative filter. Trials performed
with Black Willow, on the other hand, produced more significant results.
These results were unique in that a consistent, almost 50% reduction in
the aerosol concentration was observed across the vegetative filter. The
-------
330
Wastewater Aerosols and Disease/Aerosol Suppression
observed reduction in the concentration of bacterial aerosols by the
Black Willow filter was independent of wind speed. There was also no
observable variation in the MMD of the aerosol across the filter with
Cottonwood (Figure 6).
It is possible that the unexpected decreases in aerosol collection by
the vegetative filter with increasing wind speed were due to the forma-
tion of 'holes' in the vegetative filters. The filtration efficiency of Black
Willow was further indicated by a decrease in MMD of the aerosol
across the filter. The reduction of MMD was wind speed dependent with
a maximum of about 30% at the highest wind speed and a minimum
(actually a slight increase) at the lowest wind speed.
It was not known whether the superior collection efficiency of Black
Willow is due to leaf shape, undulating leaf characteristics, or possible
electrical charge accumulation on leaves. However, small wind speeds
are sufficient for Black Willow to produce a significant filtration effect.
The observed decrease in bacterial aerosol concentration for dense
evergreen filters was dependent upon wind speed (Figure 7) with a maxi-
mum of almost 45% collection occurring at the highest wind speed and a
minimum of 10% at the lowest wind speed. For sparse evergreen filters,
a decrease of more than 30% was observed in the bacterial aerosol
concentration across the filter at the highest wind speed. The observed
reduction in aerosol concentration with density of evergreen filters sug-
gests a minimal dependence of filtration by White Spruce on the amount
of vegetation.
60 ,-
50
40
30
c
o
o
20
10
BLACK WILLOW
2 3
Wind Speed (m/sec)
Figure 5. Percent Reduction in Aerosol Concentration as a Function of
Wind Speed for Deciduous Vegetation
-------
J. C. Spendlove, et al
331
30
20
•o
cc
o
10
-10
BLACK WILLOW,
DECIDUOUS
2 3
Wind Speed (m/sec)
Figure 6. Percent Reduction in Mass Median Diameter (MMD) of Aero-
sol as a Function of Wind Speed for Deciduous Vegetation
40
3
•o
o: 30
c
o
O
20
10
DENSE
EVERGREEN
2
Wind
Speed (m/sec)
Rgure 7. Percent Reduction in Aerosol Concentration as a Function of
Wind Speed for Two Densities of Evergreen Vegetation
The reduction in MMD of the aerosol displayed less pronounced de-
pendence on wind, but did exhibit some reduction at each of the higher
wind speeds as shown in Figure 8. This reduction also displays no con-
sistent dependence upon vegetation density. Both sets of data (concen-
tration and MMD) do indicate dependence on the wind velocity except
for sparse vegetation.
-------
332 Wastewater Aerosols and Disease/Aerosol Suppression
MEDIUM
30 r
-I 0
Figure 8. Percent Reduction in Mass Median Diameter (MMD) of Aero-
sol as a Function of Wind Speed for Various Densities of
Evergreen Vegetation
AERODYNAMICS OF VEGETATIVE BARRIERS
As a result of the present study, which showed that the attenuation of
microbial aerosols by filtration through a vegetative barrier was limited
to not more than 50%, the question of the enhanced turbulent dispersion
and dilution, that would be created by a vegetative barrier, became of
greater interest. The literature was surveyed to investigate what is
known about the aerodynamics of vegetative barriers and to what extent
they may contribute to aerosol suppression.
The available literature contains dissertations, government reports
and published papers describing a considerable volume of research into
air flow, in and around a forest canopy (9-21). There is substantial agree-
ment on the basic features of this type of flow, both from full-scale
studies and from studies carried out on models in special wind tunnels
simulating the atmospheric boundary layer. In addition there is a wide
body of literature concerned with the adsorption and release of gases,
including water vapor, within forest canopies. This literature covers
certain concepts associated with interchange of gases with foliage,
which are relevant to the current problem.
Most of the studies have been concerned with the flow through and
over the trees near the upwind edge of an extensive forest, and in some
cases, the flow leaving such a forest. However, since the most vigorous
turbulent exchange takes place over a distance of a few tree heights into
the forest, these reports cover the most important features of the forest-
canopy flow, for our purposes.
-------
J. C. Spendlove, et al 333
Characteristics of the Forest-Canopy Flow
When the turbulent atmospheric boundary layer, after it has traversed
a region of comparatively small scale roughness, encounters the upwind
edge of a forest canopy, two significant things happen. The average
wind trajectory (streamline) rises in order to carry most of the air, which
approached below tree-top height, over the forest. Also, the sudden
increase in surface roughness, characterized by the roughness length,
?o, of the logarithmic boundary layer, causes a jump in turbulent sheer-
stress, or T, near the upwind edge of the forest. Thus, a very strong
mixing process exists for a horizontal distance of a few tree heights
before the sheer-stress settles down to its new value characteristic of the
roughness parameter, fo, for the forest. The latter is a characteristic of
the diffusion of heat or momentum within a boundary layer whenever
there is a sudden change in surface temperature or surface shear-stress,
respectively.
These two features govern much of what happens near the upwind
edge of a forest. Most of the approaching air goes over the forest; some
of it jets in amongst the tree trunks for a distance of a few tree heights.
Thus most of the microbial aerosol carried in the air passes above the
trees at the upwind edge. However, the large increase in turbulent shear-
stress for the distance of a few tree heights produces a vigorous mixing
action over the first few rows of trees, and this mixing carries down into
the crowns of the trees. Hence, aerosol passing over the edge of the
forest experiences a significant vertical pumping up and down through
the foliage of the first few rows of trees, and, likewise, aerosol carried
into the region of the trunks experiences some upward mixing from the
same pumping action.
Mean Velocity Profiles
The mean velocity profiles within and above the forest canopy take
the general forms, shown in Figure 9, taken from work of Hsi and Nath
(13) for a model forest in a wind tunnel. The so-called jetting action at
tree trunk level is clearly visible. In data presented by Kawatani and
Sadek (15) the jetting action is even more noticeable and depends upon
tree spacing. Figure 10, taken from data presented by these authors,
shows the velocity profiles at a distance 5.6 tree heights (h) upwind of
the forest, at the edge of the forest, and at 1.7 h into the forest. In the
vicinity of the trunks the velocity may exceed the velocity at the same
height upwind of the forest for about 2 h into the forest. This character-
istic would be an important one to study in designing a vegetation
barrier.
Turbulent Shear-Stress Distribution
A very clear effect of the sudden change in surface roughness, as the
atmospheric boundary layer encounters a forest, has been demonstrated
in another report by Hsi and Nath (12). Their work indicates the pres-
ence of high turbulent stresses at the upwind edge of the forest for a
distance of one or two tree heights, and indicates that about 20 h into the
forest is required before the stress settles down to its new steady value.
The mixing created by this region of high shear-stress is the mechanism
-------
334 Wastewater Aerosols and Disease/Aerosol Suppression
I
I .5 I
h = HEIGHT OF TREES
X = HORIZONTAL DISTANCE DOWNWIND OF EDGE OF FOREST
X= X/*
J?= HEIGHT ABOVE FLOOR OF FOREST (m units of h)
*--&*
u = LOCAL MEAN VELOCITY
a^- REFERENCE VELOCITY AT REFERENCE HEIGHT WELL
ABOVE FOREST CANOPY
Figure 9. Normalized Velocity Profiles Through a Forest Canopy—
From 1 Tree Height Upwind of the Forest to a Distance of 12
Tree Heights into the Forest (13)
0 2 0.4 06 08 1.0
Figure 10. Normalized Velocity Profiles Near the Edge of a Forest—
Showing the Jetting Action in the Region of the Trunks, Tree
Spacing ^=h (for symbol definitions, see Figure 9) (15)
-------
J. C. Spendlove, et al
335
responsible for diffusion patterns that would be exhibited for microbial
aerosols released just upwind of a forest. Meroney and Yang (20) pre-
sent many figures showing isoconcentration profiles for a variety of
pollutant release conditions. Figure 11 is an example based on Figures
13 and 14 of their report. Here, concentration isopleths are shown for
pollutant release at the upwind edge of a forest at two heights. It illus-
trates how the flow, which enters at the base of the forest, is mixed
upwards into the flow above the canopy. It also shows how the flow
passing over the canopy becomes mixed downwards into the forest. It is
10
15
20
(a) SOURCE AT GROUND LEVEL
10
15
20
(b) SOURCE AT 0 56 h
Figure 11. Concentration Isopleths for a Source at the Upwind Edge of
a Forest (For symbol definitions, see Figure 9) (19)
-------
336 Wastewater Aerosols and Disease/Aerosol Suppression
interesting to note that the mixing mechanism is quite strong at the
upwind edge of a forest. As a result, aerosol released just upwind near
ground level will be diffused to greater heights than would occur without
a vegetative barrier. The pumping action through the canopy will also
improve adsorption on the foliage, thus augmenting the filtration effects.
Discussion
In placing the experimental portions of this study in perspective with
the literature survey, the following effects are evident: by itself, filtra-
tion of a microbial aerosol by a vegetative barrier cannot be considered
effective. However, this study has shown that filtration effects are
dwarfed by the expected reduction in aerosol concentration due to mix-
ing and dilution of aerosol at the upwind edge of the forest barrier by
orders of magnitude. The aerodynamic barrier that the forest represents
provides a method of reducing the ambient aerosol concentration, not
only by removal but principally by vertical dispersion and dilution. The
additive effects of filtration with vertical diffusion and mixing make
vegetative barriers an attractive alternative for aerosol suppression.
In the field, downwind, the influence of the barrier, in the absence of
significant filtration, would show effects in reducing aerosol concentra-
tion primarily by physical loss of the aerosol through dilution and pani-
culate fallout. In addition, viability decay of the microorganisms would
further attenuate the aerosol. The major concern, however, because of
the expected shallowness of planted barriers, has to be whether the
vegetative barrier can significantly affect the close-in regions where mi-
crobial aerosol concentration may be high enough to be objectionable.
This possible effect would require additional study.
In conclusion, it has been demonstrated that specific types and densi-
ties of vegetation may affect up to 50% reduction in microbial aerosol
concentration(s) and MMD by the mechanism of filtration. Based upon
these experimental results and a review of the literature, the dispersion
effect of a barrier, in conjunction with the filtration effects, provides a
mechanism for suppression of aerosols emanating from an aeration
basin by orders of magnitude. It is concluded that vegetative barriers
strategically placed can effectively suppress microbial aerosols from
treatment basins.
References
1. Blanchard, D.C., and L. Syzdek. 1970. Mechanism for water-to-air transfer and con-
centration of bacteria. Science, 170:626-628.
2. Randall, C.W., and J.O. Ledbetter. 1966. Bacterial air pollution from activated sludge
units. Am. Md. Hyg. Assoc. Jour., 27:506-519.
3. Adams, A.P., and J.C. Spendlove. 1970. Coliform aerosols emitted by sewage treat-
ment plants. Science, 169:1218-1220.
4. Gofl, G.D., J.C. Spendlove, A.P. Adams, and P.S. Nicholas. 1972. Emission of micro-
bial aerosols from sewage treatment plants that use trickling niters. Health Serv.
Rpts., 88:640-652.
5. Kenline, P.A., and P.V. Scarpino. 1972. Bacterial air pollution from sewage treatment
plants. Am. Ind. Hygiene Assoc. Jour., 33:346-352.
6. Fannin, K.F., J.C. Spendlove, K.W. Cochran, and J.J. Gannon. 1976. Airborne coli-
phages from wastewater treatment facilities. App/. Environ. Microbiol., 31:705-710.
7. Parker, D.T., J.C. Spendlove, J.A. Bondurant, and J.H. Smith. 1977. Microbial aero-
sols from food processing waste spray fields. Jour. Water Poll. Control Fed., 49:2359-
2363.
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J. C. Spendlove, et al 337
8. Andersen, A.A. 1958. New sampler for the collection, sizing, and enumeration of
viable airborne particles. Jour. Bacterial., 76:471-484.
9. Raynor, G.S. 1967. Effects of a forest on paniculate dispersion. Proc. USAEC Meteo-
rol. Information, Chalk River, Ontario, Rept. AECL-2787, C.A. Mawson, ed. Atomic
Energy of Canada Ltd. Chalk River, Ontario, pp. 581-588.
10. Raynor, G.S., J.V. Hayes, and E.G. Ogden. 1974. Paniculate dispersion into and
within a forest. Boundary Layer Meteorology, Vol. 7, No. 4.
11. Hsi, G.C.L. 1968. Wind drag within a simulated forest canopy field. Ph.D. Thesis. Col.
State U.
12. Hsi, G., and J.H. Nath. 1968. A laboratory study on the drag force distribution within
model forest canopies in turbulent shear flow. Tech. Rept. CER67-68GH-JHN5. Col.
State U., Fort Collins, Colorado.
13. Hsi, G., and J.H. Nath. 1970. Wind drag within simulated forest canopies. /. Appl.
Meterol., 9:592-602.
14. Sadeh, W.Z., J.E. Cermak, and T. Kawatani. 1969. Flow field within and above a
forest canopy. Task I: Study of airflow in simulated temperate and tropical forest
canopies. Tech. Rept. ECOM-0423-3. Atoms. Sci. Lab., U.S. Army Electronics Com-
mand, Fort Monmouth, New Jersey; CER69-70 WZS-JEC-TK-6. Col State U., Fort
Collins, Colorado.
15. Kawatani, T., and W.A. Sadeh. 1971. An investigation of flow over high roughness.
Tech. Rept. ECOM-C-0423-10. U.S. Army Elec. Comm., and Off. Naval Res.; CER-
71-72TK-WZS3. Col. StateU., Fort Collins, Colorado.
16. Fritschen, L.J., and C.H. Driver. 1969. Dispersion of air tracers into and within a
forested area: 1. Tech. Rept. EOM-68-1. U.S. Army Elec. Comm., Atmos. Sci. Lab.,
Fort Huachuca, Arizona.
17. Fritschen, L.J., and C.H. Driver. 1970. Dispersion of air tracers into and within a
forested area: 2. Tech. Rept. ECOM-68-G8-2. U.S. Army Elec. Comm., Atmos. Sci.
Lab., Fort Huachuca, Arizona.
18. Fritschen, L.J., and C.H. Driver. 1970. Dispersion of air tracers into and within a
forested area: 3. Tech. Rept. ECOM-68-G8-3. U.S. Army Elec. Comm., Atmos. Sci.
Lab., Fort Huachuca, Arizona.
19. Meroney, R.N., and B.T. Yang. 1969. Wind tunnel studies of the air flow and gaseous
plume diffusion in the leading edge and downstream regions of a model forest. Tech.
Rept. ECOM-C-0423-6. U.S. Army Elec. Comm., Atmos. Sci. Lab., Fort Huachuca,
Arizona; and CER69-7ORNM-BTY-17. Col. State U., Fort Collins, Colorado.
20. Shinn, J.H. 1971. Steady-state two dimensional air flow in forests and the disturbance
of surface layer flow by a forest wall. Tech. Rept. ECOM-5383. Atmos. Sci. Lab.,
White Sands Missile Range, New Mexico.
21. Oliver, H.R. 1971. Wind profiles in and above a forest canopy. Quar. J. Roy. Met.
Soc., 97:548-553.
DISCUSSION
SPEAKER: On the data that you have, is it all on Bacillus subtilis ?
DR. SPENDLOVE: Yes, it is all on B. subtilis. We did try Escheri-
chia coli along with this, but we had problems with decay in the length of
the chamber, and for that reason we gave up testing that organism.
SPEAKER: What about cells that are vegetative rather than spore
formers? Do you expect a difference between sfoore formers and non-
spore formers?
DR. SPENDLOVE: All of the Bacillus subtilis were spore formers
and were all in the spore state. We didn't expect any decay for the
distance, and our data indicated that. Where we had no vegetative filters
there was no decay for the length of the chamber.
SPEAKER: Do these effects that you describe for forests also hold
for trees that have lost their leaves during the cold half of the year?
DR. SPENDLOVE: Well of course there is some effect, but very
little. We wanted to test both of them. I would recommend that we use
vegetative barriers of coniferous trees that don't lose their leaves. Also,
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338 Wastewater Aerosols and Disease/Aerosol Suppression
I think that the small needles on those types of trees present a greater
surface area for chance of impaction than you will find on most deci-
duous trees.
DR. FLIERMANS: When you talk about the density of the canopy,
are you talking about moderate sparse or dense?
DR. SPENDLOVE: What we are talking about is the width of the
barrier. We wanted to get some impression of the effect that the width
might have. Of course, the greater the width, the greater the chance for
an aerosol particle to impact out on a piece of vegetation.
DR. FLIERMANS: Can that be related to the tree population per
square foot?
DR. SPENDLOVE: We made no attempt to relate sparse, medium,
or dense to any population. This was simply to get some idea of the
effect that the width of the barrier might have on filtration.
MR. SCHWARTZ: I wonder if the lesson this might have is that we
site wastewater treatment plants for areas of maximum turbulence?
DR. SPENDLOVE: I would say so. Also, of course, if aerosols are
shown to be a problem somewhere and you can get an instant barrier by
putting a berm around the basin as high as you could, even 10 to 15 feet,
and 50 feet thick let's say, an earthen berm will create the same effect of
pushing the aerosol up. This could be a temporary expedient and you
could plant the vegetative cover on top of that, and each year that it
grows you get better results.
MR. SCHWARTZ: Well, the one plant which I have seen is built
very similarly to a wall, with a very high barrier all around. In looking at
some preliminary data that was obtained, it seemed like there was quite
a bit of verticle mixing. The bacteria counts were really quite similar to
those upwind as far as aerosol was concerned.
MR. LINDAHL: How many rows of trees would constitute a forest?
DR. SPENDLOVE: Well, I couldn't say. The thicker you could
make it the better, up to about a hundred feet. But I would think that 30
to 50 feet of dense trees with underbrush should give you sufficient
barrier to create the desired turbulence.
MR. LINDAHL: Well, about three rows of trees wouldn't quite
qualify.
DR. SPENDLOVE: It would help. Every thing helps.
SPEAKER: What about resuspension off of those trees? It may be
more of a problem with deciduous than coniferous.
DR. SPENDLOVE: As I mentioned in my report, we tested for
reentrainment off of the vegetation and found none.
SPEAKER: Vegetation?
DR. SPENDLOVE: Yes. Now, one of the things that you should
remember is that if it is impacted it takes considerable energy to reen-
train it, like a hurricane or a tornado. Even if that happened, we have
had the particles there for sufficient time that viability decay would have
completely inactivated it.
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339
Assessment of Health Effects
Panel Discussion
Chairman—Herbert R. Pahren
US EPA, HERL, Cincinnati, Ohio
Panel Members
Leland J. McCabe, US EPA
Cecil Lue-Hing, MSD of Greater Chicago
Mitchell Singal, NIOSH
C. Scott Clark, University of Cincinnati
MR. PAHREN. We will have a panel discussion on what everything
means at this point. In selecting the panel members, I tried to obtain
persons with different viewpoints, representing different interests.
One is an individual from EPA. Another person is from the National
Institute for Occupational Safety and Health. Another interest I wanted
to have represented was one of the principal investigators of some of the
epidemiology studies that have been conducted over the past several
years and, lastly, the interest of someone involved in managing a sewage
treatment system. So, the first panel member will be Mr. Lee McCabe.
MR. McCABE. Henry Longest asked if the challenge was only sci-
entific, and I would have to answer, based on what we have heard during
the last two and a half days, that we probably do not have the complete,
scientific know-how to detect minute differences with his problem of
sewage treatment plant aerosols.
We have spent somewhat over $3 million during the last several years
and have to conclude that we cannot measure subtle differences, if they
exist, in health effects from exposure to these microbes. Considering the
impact on the agency, this has been research money constructively
spent. The effort has not been excessive or duplicative, but as research
it has shown that our methods may need further refinement.
Mr. Longest was apparently concerned that assessments would be
made that would substantially increase the cost of sewage treatment. If
we make our assessment on the sewer and wastewater treatment worker
data, we should be able to save the government considerable sums in the
construction grants program. There appears to be no hazard from sew-
age and every home can have a cesspool in the backyard to take care of
the liquid waste. As our colleague from Baylor has indicated, each fam-
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340 Wastewater Aerosols and Disease/Assessment
ily would be exposed to its own sewage and that would not be a hazard.
In order to say that sewage treatment plants are not hazardous to the
neighbors, we must have instruments that can measure the effect, if
there really is one. Bob Miday addressed the problem of the power of
the test to detect a real effect. We used the best and most sensitive
methods known but our illness inquiry system, serological epidemiol-
ogy, and check of infection rates did not find an effect. We must show
that we have a method to detect an effect in a maximally-exposed popu-
lation. In other words, we must have the equivalent of positive controls
to prove that our methodology has sufficient sensitivity to detect an
effect, if there is one. Maybe our sample sizes have been too small and
we will have to pool results from several studies, but the University of
Cincinnati group doesn't even show minor differences in the right direc-
tion. If Scott Clark studied every new worker that was hired to work at
the plants, what else could he do? Would Dr. Rylander's techniques be
more usable?
Some of us took comfort in that at least we had a worst case report
from Israel, but now Mr. Fattal tells us that this is most likely not so.
The effects of exposure to pathogens on enteric disease have been
measured. We have just completed a series of studies relating bacterial
indicators of water quality to gastrointestinal symptoms in swimmers
(1). Even as a child I was able to show the effects of privies on dysentery
rates (2). Is the adult somewhat refractory to infections even when
lacking "measurable" antibody? Will Scott Clark have to study a group
of Cub Scouts, led by a 70-year-old den mother, that clean up a polluted
riverbank?
The chemical epidemiologists seem to have solved their problem with
a few studies. Effects occur and they can be measured. All that is
needed is to keep the neighborhood exposure below the TLV or, maybe
better, to keep it below upwind background.
The concept of getting the viable microorganism count below back-
ground density should also be considered, but I am not sure we know
how to measure the viable count in the proper way. We need to be
measuring something that relates to infectious dose. Is it possible that
what has been called the aerosol shock is really the reducing of the size
of microbiological clumps? Maybe the aerosol is only a set of single
viable organisms. These could be less than a minimum infective dose.
We may need an animal exposure experiment to get at this concept. If
the exposed person must be susceptible to be able to measure an effect,
how can such a study be conducted? Children were studied at Tigard,
Oregon; and getting blasted only a few days per year was not reflected in
school absenteeism.
Dr. Fannin's paper did not talk about children except to note that the
rates were age adjusted. When he adjusted for everything, there was a
higher rate at 600 m, and a look at the tables in the published report (3)
gave a hint that children should be examined more closely. More years
of data might have to be collected and studied to get a reasonable num-
ber in just younger ages.
Don Johnson also reported an effect on neighbors; some illnesses and
infections were higher after start-up of operation. The illness effect
looks like it is greater in children to me, but I did not see data on age for
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Herbert R. Pahren, Chairman 341
the infections in their published report (4). Here we may also have too
small a population of the younger ages, but maybe another study could
be done concentrating on the young when some other plant is started up.
It would be best to have comments by Fannin and Johnson on how
they see the effects on the younger ages.
If we are requested to continue the health effects studies, we would do
well to research also the cost of aerosol supression; then more realistic
trade-offs could be made in the future.
If suppression were very costly, we would need unequivocal health
effects to justify the cost; but if some less costly techniques were avail-
able, health effects data would not need to be as firm. From what we
have heard, there would seem to be little justification for large expendi-
tures to contain aerosols based on a national policy, or even for a single
plant. The designer of sewage treatment plants must continue to be
concerned, however, and do what can be done to minimize aerosols.
Here is where the more-than-scientific considerations are involved—the
public must feel that their interests are considered.
References
1. Cabelli, V.J. et al. 1979. Relationship of Microbial Indicators to Health Effects at
Marine Bathing Beaches. Am. J. Public Health, 69:690-6%.
2. McCabe, L.J., and T.W. Haines. 1957. Diarrheal Disease Control by Improved Human
Excreta Disposal. Public Health Reports, 72:921-928.
3. Fannin, K.F. et al. 1978. Health Effects of a Wastewater Treatment System. EPA—600/
1-78-062. U.S. Environmental Protection Agency, Cincinnati, Ohio.
4. Johnson, D.E. et al. 1978. Health Implications of Sewage Treatment Facilities. EPA—
600/1-78-032. U.S. Environmental Protection Agency, Cincinnati, Ohio.
DISCUSSION
DR. LUE-HING: I think I will start by asking a question of Lee.
What was your dose-response measuring instrument for your privy
testing?
MR. McCABE: We did rectal swabs for Shigella on the kids, and we
demonstrated that before, during, and after, the rates were different. A
simple thing.
DR. LUE-HING: Well, I am happy because it seems to me that we
were using the same instrument in the epidemiological studies. So, we
do have the measuring technology, Lee, for looking at health effects.
To indicate that my comments are totally objective, I did not write
anything until this morning. In fact, I consulted with my colleagues last
night and I went to sleep, didn't think about it, and wrote most of my
notes during Lee's presentation. I was here for the last 2 days and I
heard the same presentations that Lee did, and I disagree with his as-
sessment of the information that I think we both heard.
If we start with Henry Longest again, he posed a very challenging
question; and I still believe that, in our attempt to answer that question,
we have to come down to earth a little bit. I have no objections to being
in the clouds, but there are times when we need to come down to earth. I
listened to Dr. Cliver, and I have to agree with him that the population
that is least at risk are the residents. In his descending order of risk, it
would be the workers, the visitors to plants, and, finally, the residents in
the vicinity of plants.
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342 \Vastewater Aerosols and Disease/Assessment
It was indicated by Dr. Rylander, through my interpretation of his
data, that only in specialized circumstances such as unusual confine-
ment situations was it shown that the sewage treatment plant environ-
ment may have some effects on the health of the worker. We are not
talking about aerosols in the same context of the symposium but, rather,
we are talking about a dust-related type of situation.
Dr. Fannin's work was reviewed by Lee. I have no difficulty with
Kirby's work. I think his report also showed that sewage treatment
plants can be good neighbors. Dr. Johnson's work on the John Egan
plant indicated to me that, living next to a sewage treatment plant does
not expose you to any additional risk. David Camann's work on the
school children again says to me, "We are not exposing our residents to
additional risk." And, incidentally, we, too, have a grade school next
door to one of our suburban plants in the township of Hanover Park. So,
we do share the experience with Mr. Camann.
Perhaps one of the most comprehensive, though short-lived, experi-
ments yet performed in this area, involving epidemiological characteri-
zation and assessment, was the work by Northrop of the University of
Illinois. Incidentally, it may be good for the audience to know that my
organization is involved in most of the field experimental work reported
on in the last two days, either directly or indirectly. We were involved
with Scott Clark on his study. We loaned the Northside plant to EPA for
the study by Northrop. We loaned the Egan plant to EPA for a study by
Southwest Research. We are now doing the suppression work and we
are involved in bits and pieces of other studies reported in the last 2
days.
We do have an interest, and we are not afraid to know the truth
because we feel that, if there is something out there that we need to
know, we want to be the first to know it. In these days of funding at 75%
and the enormous cost that we face in Chicago, we just want to be first
in line. So, we are interested.
I had some difficulty with the Israeli work when it first appeared in
Science, and I was asked to review that paper when it was presented in
Melbourne. I could not be there personally but a colleague of mine read
my critique. I am very encouraged that Dr. Fattal's group has decided to
reevaluate that particular study. I am encouraged because that work has
been quoted very extensively throughout the world and I run into it
almost every place I go.
However, having talked with him the last 2 days and having seen the
new information he is presenting, I am more convinced now that my
critique in 1976 was correct. I feel confident that, when his work is
completed, we will reach a conclusion that spray irrigation does not
present any significant additional risk to the community.
As a participant in Scott Clark's work, to some extent, I know of it
and I have been with it for some time. The conclusions reached also
convince me that the sewage treatment environment does not pose any
significant risk to the worker and less so to residents close to sewage
treatment plants.
I was particularly encouraged by the assessment and presentation of
Dr. Linnemann who, as a physician, could not afford the luxury of
making statistical diagnoses. He treated the data very well, and I feel
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Herbert R. Pahren, Chairman 343
that we are fortunate that the establishment of significance was not left
up to statistics alone but to the judgment of a qualified medical practi-
tioner. I have nothing against statistics. I am just afraid sometimes that
when two numbers collide, and the statistician has to make a choice he
goes in the direction of the heavier number.
Dr. Sekla's work also indicated to me that the sewage treatment envi-
ronment does not pose any additional significant risk to the worker.
Here again we have a situation where the environment was confined,
and there was far less opportunity for normal outdoor mixing. There
appears to be some information in the data she presented that this could
create some difficulty for the worker, but not the residents close by the
facility.
We are involved in the review of death certificates of former workers
of the Southwest District in Chicago. When the request was made, the
records personnel and my boss came to me and asked, "What the hell do
we do?" I said, "Give them the records. If there is anything in there you
guys need to know, you had better know it in a hurry. Give them the
records." So, we decided to participate and to cooperate. Again, we
want to know what is in those records because, if something is wrong,
we want to be the first to correct it.
Following all of this information, we examined the small data base
that we were able to generate on the basis of our aerosol suppression
study. After putting it all together, I have no difficulty at all in conclud-
ing that the proper operation of sewage treatment facilities will not pose
any additional significant risk to the community.
I noticed, in the last 2 or 3 days, that some of my colleagues, including
my friend Lee, lament the fact that we don't find any responses or we
don't find any effects. I am not surprised; they are not there. It is not
because our measurement technology isn't good enough. It is good
enough. I have always been prepared to spend money to improve our
measurement technology, but I think we have ample technology today.
We are not finding responses because the responses just aren't there. It
is not because we are not able to measure them.
I am encouraged that Lee concluded that there is no justification for
massive expenditures for suppression. I certainly agree. I will support
funds for continued work because, while I am not a public health-related
man per se, I am fully aware of the need to maintain our vigilance and to
remove any last vestige of doubt. I am happy for people like Lee Mc-
Cabe because, without them, there will always be some residual doubt,
and I would be quite prepared to support additional work in this area.
Before I close, I would like to say a few nice words for the EPA.
Those of you who know me well enough know I don't do it too often,
not because I am giving them a bad deal, but I don't think they deserve
all of the praise too frequently. In this instance, I think the EPA, and
particularly within the context of our meeting, the health effects group
should be commended.
I thought that the program had spent in the area of $12 million and I
was prepared to say, "You did a good job for $12 million," but when
you said it was about $3 million, I have to double that praise. Five years
ago, I could not comfortably arrive at the conclusions I have today.
While it was my gut feeling that my conclusions were valid then, I
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344 Wastewater Aerosols and Disease/Assessment
couldn't prove them, at least as effectively as I can today. For the $3
million that these guys have spent, I think they have gotten a very good
buy for their buck. They have answered a lot of questions, not all, but
the most critical ones. I believe that the operating parts of your agency
can now make the type of judgments that are necessary concerning
aerosols.
I believe we have arrived at the point where I personally can say,
based on what I have heard in the last 2 days, I do not see any significant
additional risk to residents around sewage treatment facilities.
MR. PAHREN: Thank you, Cecil. Also, I thank you for your kind
words regarding EPA. EPA seems to always be in the middle. On some
of our regulations, we are sued by both sides, so praise isn't coming that
frequently and it is appreciated, especially if it is coming from you,
Cecil.
MR. FATTAL: (Submitted for the proceedings in response to Dr.
Lue-Hing's comment on the 1976 article in Science—Ed.) The data of
the first study (Science paper 1976) cannot be compared to those of the
present retrospective study as they have entirely different data bases.
The most obvious and important difference is that the Science paper
included disease cases reported to the Ministry of Health, including
those cases from volunteers and temporary residents. The present ret-
rospective study is based on present kibbutz clinic records which, in
general, do not include those cases, and to our sorrow, we discovered
that kibbutz clinics do not keep files for volunteer and temporary resi-
dents after they leave. This means that the potentially most susceptible
group has been lost. This might lead to a totally skewed picture of what
really happened in years past. The only way to overcome this constraint
is through a prospective study which will include temporary workers
and volunteers as well as permanent residents.
Another difference between the two studies is that they do not cover
the identical time periods. In the Science paper, the Salmonella data was
drawn from the records of the Ministry of Health for the years 1969 to
1974, a 5-year period, while the typhoid data covered years 1965 to 1974,
a 10-year period.
We decided for reasons of uniformity and convenience to restrict our
data collection for the current retrospective study from 1974-1977, a
4-year period. Thus, the time periods of the study are not identical,
which might provide another explanation for the lack of congruence or
correlation in the overall results.
This may not explain the difference in results to the two studies, but it
is important to keep these factors in mind. Only when the prospective
3-year study is completed can we arrive at a definite conclusion.
DR. SINGAL: Without trying to be too repetitious, let me just say
that my assessment of the epidemiologic presentations yesterday was
that the studies of health effects in the community around wastewater
treatment plants, in general, showed little evidence of infection attribut-
able to treatment plant aerosols and no convincing evidence of clinical
illness. But, to briefly review the deficiencies that plagued these studies
—deficiencies in the circumstances, not in the quality of the study nec-
essarily—there seemed to be very few people living closer than a quarter
to a half a mile from the site of the aerosol generation, and even those
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Herbert R. Pabren, Chairman 345
within half a mile to a mile range, there were often insufficient numbers
of families to adequately detect illnesses that you might expect to have
with a low prevalence.
Likewise, in workers of waste water treatment plants, there seemed to
be little evidence of increased rates of infection or clinical illness due to
microbiologic agents and, thus far, no convincing evidence of increased
mortality. On the contrary, we have seen evidence of adverse short-
term health effects due to acute chemical exposures and absorption of
chemicals to which there was low level or chronic continuous exposure
and, presumably, in the near future, we will see whether there is any
evidence that this is associated with any health effects.
To the question of whether there is or is not substantial health hazard
to the community or to the workers of the treatment plants from expo-
sure to aerosols generated in the treatment plants, I would conclude
that, in the absence of any unusual circumstances resulting in unusual
exposure to the workers, there probably is no substantial health hazard
from aerosolization of microbiologic agents. I will temper that with the
realization of the conceptual and statistical difficulties of proving a
negative.
I would propose two methods of investigating this problem that
haven't been addressed. One of them is a thorough investigation of
outbreaks of infectious diseases that occur in the vicinity of treatment
plants. I am not aware that this has been recorded, or that such out-
breaks have been reported or suspected, but certainly, if one does, it
should be thoroughly investigated. As somewhat of a precedent for this,
associated with the investigation of the contamination of the Louisville
sewage treatment plant, there was a concurrent investigation of the
community surrounding the treatment plant for evidence of the same
effects that were reported by the workers. In this case, we had a defined
time period when we might expect these effects and we had specific
effects to look for. The survey involved 212 residents, and there was no
indication that the community residents suffered the same effects as the
workers.
The other approach that might be worth investigating for the effects of
microbiologic agents is to look at the surveillance data that is routinely
collected by local and state health departments. In every state, Hepatitis
A is a reportable disease. In most, if not all states, Salmonella and
Shigella laboratory surveillance is conducted. Most state health depart-
ments do most of the viral serologic work for viruses of public health
concern in the states, particularly for enteroviruses. Also, many state
health laboratories do a substantial amount of parasitic identification
and, even though they may not do the serology, they act as the conduit
for parasitic serology to the Center for Disease Control.
DR. CLARK: I would like to take advantage of being the last of the
panel to first respond to some of my fellow panel members' remarks.
After that a few specific remarks will be made on what else has been said
these past 21/z days.
Lee McCabe's questioning of whether the most sensitive health ef-
fects assessment method has been used on an adequate number of
worst-case exposures is a very important one. When we laid the plans
for our study almost 10 years ago, I thought that the worst cases of
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346 Wastewater Aerosols and Disease/Assessment
wastewater exposures in Cincinnati were among the sewer maintenance
workers. That is still my opinion today. However, because of a city
moratorium on hiring new workers, we were only able to recruit 9 who
remained in our study for a minimum of 12 months. The newly em-
ployed activated sludge treatment workers recruited into the study were
employed at recently completed activated sludge treatment plant facili-
ties in Cincinnati and Memphis. The Chicago treatment plants from
which workers were recruited, while not as new as those in Cincinnati
and Memphis, nevertheless were well maintained, up-to-date, activated
sludge treatment plants. In general, therefore, the activated sludge plant
workers in our study were not working in worst-case situations. If we
had attempted to recruit workers in the most exposed positions we
would have focussed on different groups of employees. In Chicago, for
example, employees at the sludge heat drying facility would likely have
been chosen. Exposures at this facility, however, are not representative
of those at typical modern activated sludge treatment operations. Sludge
heat drying facilities, such as the one in Chicago, are very limited in
number in this country. Certain other enclosed environments at waste-
water treatment plants, where the contaminants do not disperse or die
off as rapidly as they do in open air situations, would be likely to repre-
sent more of a potential health risk than average outdoor environments
at the plants.
Lee McCabe's somewhat jestful suggestion that we study a group of
Cub Scouts and their den mother while they are cleaning up a polluted
riverbank has some merit. For testing the adequacy of the study meth-
odology, however, I would suggest that we focus on den mothers rather
than on the cub scouts who would likely be a major pathway for infec-
tious diseases transmission to each other. The cub scouts could also
serve as a potential health risk to den mothers. The den mothers should
be recruited into the study before they undertake their responsibilities
with the cub scouts. Many alternatives to den mothers exist, such as
persons just beginning student teaching of young children.
The health effects studies performed thus far do not seem to justify
large expenditures for aerosol suppression, a viewpoint also expressed
by panel members McCabe and Lue-Hing. I agree with Cecil Lue-Hing
that some research and development effort should continue in this area.
Earlier this year I had an opportunity to visit a Los Angeles County
wastewater treatment plant that had installed removable covers over the
top of the aeration basins. The purpose of the covers was not to sup-
press airborne bacteria and viruses, but rather for odor control thought
necessary because of local complaints. As I recall air beneath the covers
was used as a source of air for the plant blowers, further reducing the
release of odors. Existing aeration basin covers, such as these, warrant
examination for study of their utility in reducing viable aerosol emis-
sion. Activated sludge treatment plants using pure oxygen, rather than
air, as a source of oxygen for the microbes, should also be considered
for their aerosol suppression characteristics which result from their hav-
ing covers on their aeration tanks to permit recovery of oxygen. Any
added cost of the oxygen systems over those using air should be com-
pared to the cost of suppression devices installed on systems using air.
In colder climates, some increase in the plant efficiency may also result
-------
Herbert R. Pahrea, Chairman 347
from covered aeration tanks maintaining higher wastewater tempera-
tures. Care must be taken in the examination of various techniques for
aerosol suppression to insure that workers are not subjected to undue
safety risks as well as other hazards.
Mitch Singal offered two alternative approaches to study wastewater
treatment plant-caused health effects—the investigation of outbreaks in
the vicinity of treatment plants and the investigation of surveillance data
routinely collected by local and state health departments. The first ap-
proach could be expanded to include possible outbreaks among treat-
ment plant personnel as well. My colleagues at EPA and I are contacted
from time to time regarding suspected outbreaks at sewage treatment
plants. In one such instance involving chemical exposure in Memphis,
Tennessee, we were fortunate enough to have a routine infectious dis-
ease study underway at the same plant and were able to conduct a
limited investigation. Vic Elia reported on some of the results of it
yesterday. This investigation, as well as the one conducted by NIOSH in
Louisville, Kentucky, and reported by Kominsky 2 days ago, have pro-
vided very useful information regarding the potential for chemical expo-
sure of workers at wastewater treatment plants. Those exposures are
likely to be intermittent in nature and therefore not amenable to study
except when special conditions prevail.
The second approach suggested by Dr. Singal, examination of routine
health department surveillance data, was attempted a number of years
ago for Hepatitis A by fellow panel member Lee McCabe and a col-
league of his (1). At the time, little data was available for other infec-
tious diseases. They concluded that in Ohio, Hepatitis A rates among
sewage treatment plant personnel appeared to be higher than among the
rest of the population. This approach might yield useful information if
attempted again.
There are several comments that I want to make on some of the
presentations made during the previous 2 days. The studies of exposures
of wastewater treatment plant personnel to organic chemical emissions
reported by Kominsky and by Elia et al. seem to indicate that the acute
effects subside rather rapidly after the exposure has ended. What isn't
known are the long term effects. In the case of the Memphis situation,
the exposure appears to be a continuous one of variable magnitude that
has thus far lasted more than 2 years.
Rylander and Lundholm's work has been of interest to us for several
years. Their initial study that came to our attention reported adverse
effects of exposure to heat dried sludge. More recently, some of these
same responses, such as elevated immunoglobulins and excess gastroin-
testinal symptoms occurred in workers at regular activated sludge
plants. We have not found consistently elevated immunoglobulins
among sewage-exposed workers in our study but have detected higher
rates of gastrointestinal illness among workers newly employed in
wastewater treatment plants. Rylander and Lundholm suggest that en-
dotoxins are responsible for many of the adverse effects observed. We
are currently including an evaluation of this exposure agent in our study
of wastewater treatment plant sludge composting workers.
Results of the Tigard, Oregon, school attendance monitoring study
should be used with caution because of the many factors unrelated to
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348 Wastewater Aerosols and Disease/Assessment
the nearby treatment plant that may affect school attendance, as the
investigators indicated. Nonetheless, I think the observation that foam
from the aeration tanks can be seen depositing on the school playground
is evidence enough that the wastewater treatment plant is located too
close to the school. The report by Fattal yesterday on their follow-up to
the retrospective study of Israeli kibbutzim using wastewater spray irri-
gation suggest results different from those in their earlier report on this
study. The new evidence would seem to indicate that, for the time being,
the kibbutzim study results should not be cited as conclusive evidence
of an adverse effect of wastewater spray irrigation.
The Copenhagen, Denmark, sewer worker study discussed by Dean is
of interest primarily because of the elevated levels of immunoglobulin,
and the high proportion of workers who die during their first year of
retirement. Elevated immunoglobulins were also reported in wastewater
treatment plant workers in Sweden by Rylander and Lundholm. Our
interim evaluation of data on a mortality study of former wastewater
treatment plant employees of the Metropolitan Sanitary District of
Greater Chicago did not reveal such a high percentage of deaths early in
retirement.
The study of Manitoba, Canada, wastewater treatment plant workers
detected sinusitis among the workers that started upon exposure to the
work environment and diminished after leaving work. They suggest that
an allergen might be involved. Other findings of the study such as an
excess of nasal disorders warrant follow-up.
In our study of wastewater workers, which was reported on exten-
sively yesterday, indications of increased risk due to wastewater expo-
sure have thus far been very few. In a prospective study of the relatively
small population groups involved, with the inherent inability to control
the hiring of new workers and their longevity of employment, certain
imbalances of age and race are difficult to avoid. However, after careful
analyses, we do not think that these differences affected the study re-
sults. Our initial objective of determining the sensitivity of the seroepi-
demiologic approach was not fully achieved because of the untimely
moratorium on hiring of new sewer maintenance employees.
In conclusion, the results of the last 2l/2 days seem to indicate that
wastewater treatment plant workers' hazard, if any, is small from infec-
tious disease agents. Such hazards to nearby residents do not appear to
have been detected at all. However, the worst case of exposure of either
worker or neighbor has almost certainly not been investigated. Where
acute exposure to organic chemicals has been expected, it has not been
difficult to detect measurable effects.
References
1. Dixon, F.R., and L.J. McCabe. 1964. Health Aspects of Wastewater Treatment. Jour.
Water Pollution Control Fed., 36:299-304.
DISCUSSION
MR. PAHREN: Next, I would like to give the four panelists an op-
portunity to cross examine each other. Who would want to ask the first
question?
-------
Herbert R. Pahren, Chairman 349
DR. LUE-HING: I would like to make a few comments, which I
probably should have made earlier. Dr. Singal brought it to my attention
when he indicated his concern for the size of the resident population
in the vicinity of its sewage treatment facility. The general pattern is
for the immediate vicinity of a sewage treatment plant to be thinly
populated.
However, in spite of that, the work done by Northrop of the Univer-
sity of Illinois on our Northside plant included in the test zone, not a
number of families selected for testing by Northrop, but the test zone
defined by the experiment contained over 16 thousand people. Without
having the statistics in front of me, I can easily say that this population is
greater than 40 percent of the cities in the State of Ohio. That is a lot of
people.
The fact that Northrop selected 300 families indicated to me that he
had a wide selection. He could have selected 1,000 if he had wanted to.
There was not enough money in the budget to study 1,000 people, and I
think Northrop and his group are intelligent enough to know that you
don't need to study 2,000 families. You can do it with less if you design
experiments properly and conduct your study to take care of that small
population. Larger populations naturally are more desirable.
There is one other point which I have to comment on again. That is the
fact that we don't find responses simply because they are not there. We
should not forget that we have conditioned ourselves in the last 20 years
to expect trouble, and we are not yet prepared to accept the fact that we
were run off. We have to face up to the fact that we made it by crawling,
and we will forever blame the lack of responses on measurement tech-
nology unless we come to grips with the fact that we are not really going
to find the type of tragedy that some individuals predict, especially if
they use a model.
So, I am happy that the measurement technology is adequate and that
we are not finding these responses because they just aren't there.
DR. SINGAL: My comment about the sample size didn't have to do
with the fact that he selected 305 out of 16,000. It had to do with the fact
that if there is an effect, it is most likely very minimal and very subtle,
and you wouldn't expect to see it out at a half mile or even beyond a
quarter of a mile where most of these 16,000 people live. You would
expect to see it up close to the source, and my comment on sample size
had to do with the fact that even though there were 16 thousand people
living in the test area, most of those people didn't live close enough to
the plant to be exposed.
DR. LUE-HING: I think I would agree with you if there were any
exposure at all. I think you are quite safe if you are 50 feet away.
MR. PAHREN: At the Northside plant where Dr. Northrop studied,
I think the distances were measured from the center of the aeration
basins. As I recall that site, there are houses right across the street on
the west side. Do you know the distance between the edge of the aera-
tion basin and the nouses, Cecil?
DR. LUE-HING: I don't recall.
DR. NORTHROP: Thirty houses are within a quarter of a mile.
MR. McCABE: Well, I think Scott and Mitch both agreed that we
ought to conduct the studies like a dose response, and you ought to have
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350 Wastewater Aerosols and Disease/Assessment
some place where you are getting a response. I don't think the conclu-
sion is that we didn't see a response because there wasn't any. Some-
how I think we should have been seeing something in the workers or we
were not measuring the right thing.
We are not going about it the right way if we don't see something in
the workers. Other than that, we shouldn't bother to build sewage treat-
ment plants. Dump it in a stream.
DR. SINGAL: I think Scott said, the workers may not be the people
who you might expect to show effects. There are no children, there are
no old people, there are no debilitated people. Some of the organisms
that were mentioned as problems, like Klebsiella and Pseudomonas, are
mainly opportunistic pathogens that need a compromised host in order
to cause a clinical illness. So again, you wouldn't expect these organ-
isms to cause problems in generally healthy workers.
MR. PAHREN: How serious are some of the infectious diseases that
the workers might get?
DR. SINGAL: Well, most Salmonella and Shigella infections are a
matter of a few days illness, but they can be more serious. Parasitic
infections aren't necessarily disabling, but they are unpleasant and
unesthetic. Viral infections are not a big problem. As was mentioned,
most of those poliovirus isolates and serologic responses were likely due
to vaccine strains rather than wild strains. Enterovirus infections and
other gastroenteritis are disabling for a day or two for the most part.
DR. LUE-HING: I do believe we might take some time to develop a
practical methodology in the area of virus identification and enumera-
tion. One of the problems we have is the inability to compare notes
between laboratories. I think it is important that we develop some lan-
guage where we can talk and understand each other in terms of what is a
virus; how many do we have; and how do we go about counting them,
identifying them, and standardizing the methodology for doing this.
DR. LUND: Did you study surface aerators or deep aerators?
DR. CLARK: Our plants have the porous plate diffusers at the bot-
tom so your point is well taken. The surface aerators could have much
more effect. Part of our reason for looking at the plants with subsurface
aerators was that these were planned for the plant near the Chicago
airport.
DR. JOHNSON: I think in all of our health studies and population
studies that we lacked sufficient population within about 400 meters,
particularly children. In our Egan plant studies we did expect to empha-
size preschool children and school children with approximately half of
the population. We did that and it still was not sufficient because there
simply weren't that many people living there. Even the school we stud-
ied was 400 meters from the aeration basin.
I would like to make a comment now about the help we got from the
Metropolitan Sanitary District personnel. They were extremely helpful
and I would also like to make a comment that our conclusions were
based on that plant relative to operations at that plant.
SPEAKER: If there were any effects as a result of the operation of
treatment processes, there should have been some kind of evidence by
this time. I don't know why in the recent years, some people are jump-
ing on the bandwagon of research regarding aerosol effects.
-------
Herbert R. Pahren, Chairman 351
DR. LUE-HING: Well, I have to agree with the gentleman on his
feeling toward the recent popularity of aerosol work. In this country the
incentive is money, and it is a very good incentive. I have no objection
to that incentive. The sewage treatment plants constructed since the
1900's have been generating aerosols across this country. In Chicago,
we don't measure aeration tanks in square feet. We measure them in
acres.
If you remember the picture I showed yesterday, it was approxi-
mately a quarter of a mile across the aeration tanks. At this plant where
we pump almost a billion gallons of sewage every day, we do have
residents within, I would say, 250 ft of these aeration tanks.
They have lived there for decades. We are not aware of any problems.
We can't get our operators to retire. We have to keep extending their
retirement. At retirement age they keep asking for extensions. They
don't get sick.
DR. DEAN: Why is there this emphasis on aerosols? I think it was
pointed out in one of the early papers that many of the objections to
odors and aerosols and virus infections are really secondary objections.
The real objection is the people don't want the big city pushing down on
them and telling them what to do.
We have had a great many objections of this sort where people are
building their own power base by raising objections to what is not really
related to the problem at hand, but is a handle they can use. We see the
reverse done. We see recommendations for restrictions on sewer con-
nections but what is really wanted is a rezoning ordinance. It is easier to
restrict the load on the sewage plant and thus keep people from building
more houses than it is to put in the zoning laws. There are a great many
examples like this, and a lot of the objections to aerosols are probably
not really based on aerosols.
DR. AKIN: Just a comment about the direction of future virus work.
Traditionally, environmental virology has dealt with the enteroviruses
because we had the tools for their in vitro study. The environmental
transmission of disease produced by these viruses is difficult to study
because most infections occur in children and are asymptomatic; also, a
wide variety of symptoms are produced in those that do manifest dis-
ease. It appears that we are now obtaining the tools for in vitro study of
the viruses that have been shown epidemiologically to produce water-
borne disease—namely, Hepatitis A virus and the gastroenteritis
viruses.
Explosive outbreaks caused by the contamination of drinking water
by these viruses have been documented. Recently, CDC reported a
gastroenteritis outbreak (presumed to be viral) affecting about 200 swim-
mers. Tests on the water before and after the outbreak did not show
elevated indicator bacteria counts at the swimming site. Obviously, this
agent is very virulent and produces disease in all age groups. I think it is
appropriate for environmental virologists to now focus on these agents
and possibly put less of our energy and resources into studies of the
enteroviruses.
MR. PAHREN: A question just occurred to me and perhaps I will
direct it to Dr. Clark. In thinking about John Phair's paper, do you think
that the heroic efforts of phagocytes and polymorphonuclear leukocytes
-------
352 Wastewater Aerosols and Disease/Assessment
might be one of the reasons that we are not seeing effects in exposed
personnel? I am referring to the fact that in many of these exposure
cases you do not see increases in antibody. Is this the case because of
the cell-mediated immunity whereby foreign matter is phagocytized be-
fore it initiates the antibody response?
DR. CLARK: White blood cell (leukocyte) counts were routinely
performed during the annual health examinations given study partici-
pants. Elevations among sewage exposed workers were not detected,
however. It is possible that testing performed more frequently would
have detected elevations. In our health study of sewage treatment plant
sludge composting workers complete blood counts are being performed
several times per year.
DR. SINGAL: I think many of the bacteria we are talking about in
normal intestinal flora are common environmental bacteria that don't
cause infection per se. Salmonella and Shigella are relatively uncommon
in infectious amounts. Whatever Salmonella and Shigella find their way
into the sewers are greatly diluted by the time they reach the sewage
treatment plant. I don't recall any of the papers that tried to measure
them and actually found them. Is that everybody else's recollection too?
DR. CLARK: We found a few Salmonella.
DR. SINGAL: In the sewage?
DR. CLARK: No, in rectal swabs.
DR. SINGAL: Okay, so in the case of bacteria, I think the primary
reason you didn't see infections was there was probably seldom expo-
sure to an infectious dose of the pathogen. In the case of the viruses,
probably the first exposure causes, in most adults, a non-illness infec-
tion, a sub-clinical infection if you will. Then subsequent to that there is
humoral antibody protection.
DR. JOHNSON: I think that we probably are underestimating public
interest in environmental issues on health effects at sewage plants.
MR. WITHERELL: Coming from a rural area I am concerned about
the aerosols that are generated with more conventional types of treat-
ment for rural areas, mechanical aeration, and we are going into oxida-
tion ponds to a great extent. We are also getting some spray irrigation.
To date we are recommending spray irrigation only after secondary
treatment, but I think the push is on from an economic standpoint to do
as little pre-treatment as possible, i.e., taking raw sewage, grinding it up
and spraying it on the fields to keep costs down. But what are the health
effects of those aerosols? It seems to me that we should encourage
responsible investigation into this.
DR. SINGAL: Community outbreaks may be an appropriate time to
look at the community around the treatment plant and at the workers at
the plant. We should see what the attack rate was among them compared
to the rest of the community and where they fit on the disease curve. I
think if it turns out that they were rather late in the curve, that might
suggest that their source of exposure was everybody else's excretion.
DR. CLIVER: I have a lot running through my head in the last few
minutes. On the one hand we heard early on that there was a great
difficulty in getting representative samples of aerosols and, on the other
hand, the model that I tried to construct of what hazards there might be
in regard to aerosol had a great deal to do with the problem of sampling
-------
Herbert R. Pahrea, Chairman 353
the sewage plants and determining what is being contaminated by the
aerosols directly. I couldn't help but think that, for some of these infec-
tions, we already have other ways to extract the data. Maybe what we
need to do is place ham sandwiches in key places around one of these
aerosol generating plants to see if we can detect which areas this infec-
tion is spreading from.
MR. McCABE: I think certainly what Dean says has been an issue
with the FDA and the chickens, by introducing every house to a big
batch of Salmonella every time you buy a chicken. That is a problem.
Granted the chicken is cooked, but if you innoculate everything else on
the kitchen sink, I think there is some merit to that idea. There might be
something that you could do among the neighbors.
DR. SINGAL: Are you suggesting that a 50-cent ham sandwich is a
better measuring device than those $3,000 instruments?
MR. McCABE: Probably.
MR. SCHWARTZ: In talking with a number of plant operators
around this area, I find that some plants are issuing up to 7 to even 10
changes of protective clothing per week. This is a work uniform. Is there
any new push in either NIOSH or EPA to develop a set of health
standards?
DR. SINGAL: I am not aware of any NIOSH work specifically on
work standards for sewage treatment workers.
MR. McCABE: I don't know how EPA is going to have that happen.
We are certainly not going to do it. NIOSH is not doing it. It looks like it
is in the crack.
MR. PAHREN: Well, Dr. Clark mentioned that 8 years ago he ap-
proached NIOSH about their interest in looking at the occupational
health of workers, and they said that if he found a hazard to let them
know and they will proceed. Now, is there sufficient evidence for
NIOSH to proceed or not? Or will they have to consider the material in
the proceedings?
MR. SCHWARTZ: One of the reasons I bring this up is because I
have seen some of the contents from operator short courses, under the
direction of the State of Ohio, which suggest to employees that they not
only shower before they go home but that they not take their work
clothes home. If they do, they should be sure not to wash it with those of
their family because of the potential of infectious organisms that might
have adhered to their clothing.
DR. SINGAL: In my personal opinion, it seems like a good idea,
even though we haven't documented any transmission. Based on the
precedent for working with other hazardous materials, it would be cer-
tainly consistent with NIOSH recommendations and OSHA regulations
concerning other hazardous materials, either chemicals or biologic
agents.
MR. PAHREN: In the meantime I think common sense should
prevail.
DR. LUE-HING: For the general worker in the plant I don't think
we have any special program for the clothes. For workers who have to
enter sewers, at least in the R&D department, we manage the industrial
waste control program, and in some instances we have disposable
clothes. If we are investigating an explosion in a pesticide plant, we
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354 Wastewater Aerosols and Disease/Assessment
would go in with disposable clothes. You walk out, take it off, shower
and get out. But we don't have any program of that type for the in-plant,
8:00 to 5:00 worker.
MR. SCHWARTZ: If I might make one more comment on this, one
of the things that is increasing in practice is the storing of wastewater
samples in the same refrigerator with employee lunches. I think that that
should not be tolerated.
MR. PAHREN: This applies not only to sewage treatment plants but
to research laboratories.
DR. LUE-HING: We don't permit that in Chicago. I do have a cou-
ple of comments on disinfection if I might make them. The gentleman
was concerned about spray irrigation. I cannot speak to that question
specificially, but in the State of Illinois, we have petitioned the state to
abandon its requirements for chlorination of secondary effluents for
several reasons: 1) we cannot document where it presents a hazard to
the citizens of the state; 2) it costs too much; and 3) if one looks at the
data with and without chlorination, they are indistinguishable. For ex-
ample, the requirements of the state say you should chlorinate to 400
fecal coliform organisms/100 ml. In a 60-day continuous, 24-hour a day,
sampling study at a plant, we found that the unchlorinated effluent for
those 60 days had a mean of less than 1,000/100 ml. When you are
talking about sewage, those two numbers, to me, are back to back. For
these and other reasons, we are petitioning that the requirement be
abandoned.
MR. PAHREN: Let us now close the symposium. Thank you all for
attending. I hope it has been worthwhile and that the information pre-
sented will serve the scientific community and regulatory agencies.
-------
355
REGISTRATION LIST
ABID, Syed H.
Virologist
Metro. Sanitary District of Greater
Chicago
J. Egan WRP, R.R #2, Box 226
Roselle, IL 60172
ACKERMAN.RoyA.
Technical Director
ASTRE
P.O. Box 5072
Charlottes ville.V A 22905
ADAMSKI, Robert E.
NYC Dept. of Environmental Prot.
40 Worth Street
New York, NY 10013
AKERS, Thomas G., Dr.
Associate Dean
Tulane University
School of Public Health & Trop. Med.
150S. Liberty Street
New Orleans, LA 70112
AKIN, Elmer W., Dr.
Chief, Acute Disease Program
U.S. EPA, HERL
26 W. St. Clair St.
Cincinnati, OH 45268
ALEXANDER, Darryl L.
Research Assistant
Kettering Laboratory
University of Cincinnati Medical Center
3223 Eden Avenue, Rm. 112
Cincinnati, OH 45267
ALLISON, Betty K.
Biological Lab Technician
U.S. EPA, EMSL Virology
26 W. St. Clair St.
Cincinnati, OH 45268
ANDELMAN, Julian B., Prof.
University of Pittsburgh
Graduate School of Public Health
Pittsburgh, PA 15261
ANDERSON, E. V.
Johnson & Higgles
95 Wall St.
New York, NY 10005
ANDERSON, Rodney, Dr.
Calspan Corporation
P.O. Box 400
Buffalo, NY 14225
ANDRAE, George
Environmental Health Engr.
DuPage County Health Dept.
111 N. County Farm Road
Wheaton,IL 60187
ARIAIL, David
Land Treatment Specialist
U.S. EPA, Region IV
345CourtlandSt.,NE
Atlanta, GA 30308
AVENDT, Raymond J.
Assistant Vice President
Consoer, Townsend & Associates
360 E. Grand
Chicago, IL 60611
BAIRD, George
Assistant Env. Lab Director
Fairfax County Wastewater Treatment
Div.
4100 Chain Bridge Road
Fairfax, VA 22030
BARTH, Edwin F.
Chief, Biological Treatment Section
Municipal Env. Research Lab
26 W. St. Clair St.
Cincinnati, OH 45268
BAXTER, Peter J., Dr.
Center for Disease Control
1600 Clifton Road, NE
Atlanta, GA 30333
BEARDSLEE, Richard
U.S. EPA, Region V
230 S. Dearborn
Chicago, IL 60604
BERG, Gerald, Dr.
U.S. EPA, EMSL
26 W. St. Clair St.
Cincinnati, OH 45268
BENOER, Jon H.
Sanitary Engineer
U.S. EPA, Wastewater Research
26 W. St. Clair St.
Cincinnati, OH 45268
BENETT, Don, Lt.
Water Quality Engrg. Div.
U.S. Army Environmental Hygiene
Aberdeen Proving Grounds, MD 21010
-------
356
Wastewater Aerosols and Disease
HERMAN, Donald
Microbiologist
EPA, EMSL
26 W. St. Clair St.
Cincinnati, OH 45268
BERTUCCI, James
Metro. Sanitary District of Greater
Chicago
Egan Lab., R.R. #2, Box 226
Roselle, IL60172
BETTINGER, George E., Dr.
E.I. DuPont de Nemours & Co.
Haskell Laboratory of Toxicology &
Industrial Medicine
Wilmington, DW 19898
BLAKE, John W., Dr.
Director, Environmental Programs
Power Authority of New York State
10 Columbus Circle
New York, NY 10019
BLANCO, Alfonso
U.S. EPA
John F. Kennedy Bldg., Rm. 2313
Boston, MA 02203
BO YD, Charles W.
Metro. Sanitary District of Greater
Chicago
100 E. Erie
Chicago, IL 60611
BOYLE, Virginia
University of Cincinnati
3338 Ridge Cap Drive
Memphis, TN 38138
BJORNSON, H. S.,Dr.
University of Cincinnati Medical Center
Dept. of Surgery
231 Bethesda Avenue
Cincinnati, OH 45267
BRENNER, Kristen
Graduate Research Assistant
University of Cincinnati
5786 Shadyhollow
Cincinnati, OH 45230
BRIGANO, Frank A. Orlando, Dr.
Postdoctoral Fellow
Dept. of Civil & Env. Engrg.
University of Cincinnati
Box 1209, 2920 Scioto Street
Cincinnati, OH 45219
BROWN, David S.
City of Springfield
P.O.Box 1208-WWTP
Springfield, OH 45501
BRUMBERG, A.J.
Chief Engineer
Montgomery County, Ohio
Sanitary Engineering Dept.
4221 LammeRoad
Dayton, OH 45439
BRYANT, Mary C.
Assistant Regional Counsel
U.S. EPA, Region V
230 S. Dearborn St.
Chicago, IL 60604
CAMANN, David E.
Southwest Research Institute
Post Office Drawer 28510
San Antonio, TX 78284
CAPITO.Johnl.
1649 White Shop Road
Culpeper, VA 22701
CAREY, Robert P.
Ohio EPA
Box 1049
Columbus, OH 43215
CARR, F. Robert
Tatman & Lee Assoc., Inc.
2005 Concord Pike
Wilmington, DE 19803
CARROLL, Ernest R.
Safety Officer
Dept. of Environmental Protection
Administration Building
Wards Island, NY 10035
CHAPIN, Richard W.
Environmental Assessment Council
789 Jersey Avenue
New Brunswick, NY 08902
CHEN, Chiu-Yang, Dr.
For Am Trading Co.
5585 Noah Way
San Diego, CA 92117
CHUNG, Moon S.
Project Manager
Engineering-Science
600 Bancroft Way
Berkeley, CA 94710
CLARK, C. Scott, Dr.
Kettering Laboratory
University of Cincinnati Medical School
3223 Eden Avenue
Cincinnati, OH 45267
CLARKE, Norman, Dr.
U.S. EPA
26 W. St. Clair St.
Cincinnati, OH 45268
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357
CLEVENGER, Tom, Dr.
Associate Director
Environmental Trace Substances
Research Center
University of Missouri
Route #3
Columbia, MO 65201
CLIVER, Dean O., Dr.
Food Research Institute
University of Wisconsin
1925 Willow Drive
Madison, WI53706
COLBAUGH, Jim, Manager
Las Virgenes Municipal Water District
4232 Las Virgenes Road
Calabasas.CA 91302
COLLIER, James R.
Public Health Engineer
Div. of Environmental Health
Bureau of Water Pollution Control
150 West North Temple
Salt Lake City, UT 84110
COLLINS, Jerry R., Jr.
Manager of Wastetreatment Facilities
City of Memphis
2303 North Second Street
Memphis, TN 38127
CONW A Y.Kathleen
U.S. EPA (RD-683)
Office of Health Research
401 M Street, S.W.
Washington, D.C. 20460
COONY, Michael
Idaho State Dept. of Health & Welfare
Div. of Environment
2110 Ironwood Parkway
Coeur D-alene, ID 83814
CRAWFORD, George V.
Gore & Storrie Ltd.
1607 Bay view Avenue
Toronto, Ontario, Canada, M4G 3C2
CRONIER, Sandra
R.R. #1
Guilford, IN 47022
DAHLING, Daniel R.
Microbiologist
U.S. EPA
26 W. St. ClairSt.
Cincinnati, OH 45268
DA VIS, M. L.,Dr.
Dept. of Civil & Sanitary Engrg.
Michigan State University
East Lansing, MI 48824
DAVIS, Ra'Nell Alcya
Assistant Water Systems Chemist
Detroit Wastewater Treatment Plant
9300 West Jefferson
Detroit, MI 48209
DEAN, Robert B., Dr.
Lundean Environmental Company
Dronningensgrad 9
DK-1420 Copenhagen K
Denmark
DEMIRJIAN.Y. A., Dr.
Manager-Director
Muskegon County Wastewater
Management System
8301 White Road
Muskegon, MI 49442
DiPUCCIO, Anthony J.
Senior Project Engineer
SCS Engineers
211 Grandview Drive
Covington, KY 41017
DOHERTY, Paul E.
Sanitary Engineer
U.S. EPA, Region VII
324 E. 11th St., WATR/ENGR
Kansas City, MO 64106
DONNELLON.JohnJ.
Deputy Chief
NYC Dept. of Environ. Protection
Division of Plant Operations
Wards Island, NY 10035
DONNELLY, Jean
Graduate Assistant
Dept. of Civil & Environ. Engrg.
721 Rhodes Hall
University of Cincinnati
Cincinnati, OH 45221
DOTSON.G. K.
U.S. EPA, MERL
26W. St. ClairSt.
Cincinnati, OH 45268
DOWNING, Jonathan
Laboratory Director
Dept. of Public Utilities
P.O.Box 1103
Colorodo Springs, CO 80947
DOZIER, Jack C., Program Manager
Municipal Grants Program
Georgia Environ. Protection Div.
270 Washington St., S.W.
Atlanta, GA 30034
EBORALL, Alan
President, Idaho Utility Services, Inc.
Rt. 4, Box 157
Coeur D-alene, ID 83814
EDWARDS, Barbara, Dr.
Ebon Research Systems
1542 Ninth St. NW
Washington, D.C. 20001
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358
Wastewater Aerosols and Disease
EFTELAND, Jon
Assistant Professor
Department of Geography
University of Northern Iowa
Cedar Falls, IA 50613
ELI A, Victor J., Dr.
Kettering Laboratory
University of Cincinnati Medical
Center
3223 Eden Avenue
Cincinnati, OH 45267
ELLIS, Elliot M.
Highway Maintenance Div.
3300 Colerain Avenue
Cincinnati, OH 45225
ERICKSEN, T. H.
Research Microbiologist
US EPA, HERL
26 W. St.ClairSt.
Cincinnati, OH 45268
EVER, Frederick T.
Sanitary Engineer
Dept. of Natural Resources
Water Quality Division
350OhawaSt.,NW
Grand Rapids, MI 49503
FANNIN, KerbyF.,Dr.
IIT Research Institute
10 West 35th Street
Chicago, IL 60616
FATTAL, Badri
Environmental Health Laboratory
Hadassah Medical School
Hebrew University
P.O. Box 1172
Jerusalem, Israel
FEDER, Robert L.
U.S. Army Engineering Div., Ohio River
P.O. Box 1159
Cincinnati, OH 45201
FELICIANO, Donald V.
Water Pollution Control Fed.
2626 Pennsylvania Ave., NW
Washington, D.C. 20037
FERRARA, Raymond A.
Assistant Professor
Princeton University
Dept. of Civil Engineering
Princeton, NJ 08544
FISH, Birney R.
Director, Environmental Div.
McDowell Cancer Network
915 South Limestone St.
Lexington, KY 40503
PLASTER, David S.
Michael Baker, Jr. of New York, Inc.
219 East 44th St.
New York, NY 10017
FLIERMANS,Carl,Dr.
Savannah River Laboratory
E.I. du Pont de Nemours & Co.
Atomic Energy Division
Aiken, SC 29801
FREIHOFER, Vic
Environmental Engineer
Div. of Water Quality
2514 Dixie Highway
Ft. Mitchell, KY 41017
FREUND, Alice
Environmental Scientist
Hazen & Sawyer Engineers
360 Lexington Avenue
New York, NY 10017
FUHS.G. W.,Dr.
NYS Dept. of Health
Div. Labs & Research
Empire State Plaza
Albany, NY 12201
GELDREICH, Edwin E.
Research Microbiologist
Chief, Microbiological Trmt. Branch
Drinking Water Research Div.
US EPA, MERL
26 W. St. ClairSt.
Cincinnati, OH 45268
GERBA, Charles P., Dr.
Asst. Professor of Env. Virology
Dept. of Virology
Baylor College of Medicine
Houston, TX 77030
GERGER, Douglas
ENCOTEX
3950 Varsity Drive
Ann Arbour, MI 48104
GERHARD, M. Kathy
Industrial Hygienist
Private Consultant
5723 Prince William St.
Louisville, KY 40207
GILLESPIE, Vickie L.
University of Cincinnati
3223 Eden Ave.
Cincinnati, OH 45267
GILLMAN, Rita, Chemist
Richmond Sanitary District
451 Test Road
Richmond, IN 47374
GLEASON, Thomas L., Ill
U.S. EPA(RD-681)
401 M Street, SW
Washington, D.C. 20460
GODFREY, Carole
Assistant Engineer
Allegheny Cty. Sanitary Authority
3300 Preble Avenue
Pittsburgh, PA 15233
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359
GOLDSMITH, Harold A.
Senior Environmental Engineer
Kraft, Inc.
Kraft Court
Glenvieww, IL 60025
GOODMAN, Albert
Jeffersonville Wastewater Trmt. Plant
9th and Illinois Ave.
Jeffersonville, IN 47130
GOYKE, Tammy
US EPA
26 W. St. ClairSt.
Cincinnati, OH 45268
GREATHOUSE, Daniel G.
US EPA, HERL
26 W. St. Clair St.
Cincinnati, OH 45268
GUPTA, D.K..P.E.
D. Kumar International, Inc.
P.O. Box 160
South Holland, IL 60473
HALLIBURTON, Mary M.
Dept. of Env. Quality
Water Quality Division
P.O. Box 1760
Portland, OR 97207
HANSON, Douglas M., Dr.
Vice President
Bioassay Systems Corp.
100 Inman Street
Cambridge, MA 02139
HARLIN, Curtis C., Jr., Dr.
Chief, Wastewater Mgmt. Branch
R. S. Kerr Research Lab, EPA
P.O.Box 1198
Ada, OK 74820
HARVERLAND, Rick A.
Systems Technology Corp.
245 N. Valley Road
Xenia, OH 45385
HAYMES, Neil, M.S.P.H.
Columbia University
333 E. 43rd St.
New York, NY 10017
HERWIG, Lee C., Jr.
U.S. Army
4212 Ann Fitshugh Drive
Annandale,VA22003
HESSE, Carolyn
Technical Assistant
Illinois Pollution Control Board
309 W Washington St., Suite 300
Chicago, IL 60606
HILL, David
Research & Control Specialist
City of Dayton
2800 Guthrie Road
Day ton, OH 45420
HOFF,JohnC.,Dr.
Res. Microbiologist
U.S. EPA, Drinking Water Research
Division, MERL
26 W. St. Clair St.
Cincinnati, OH 45268
HOLCK, John N.
Soil Scientist
Minnesota Pollution Control Agency
Facilities Section
1935 W. Co. Road, B2
Roseville, MN55113
HOLDEN, Janet
School of Public Health
University of Illinois at the Medical
Center
P.O. Box 6998
Chicago, IL 60680
HOLLAND, Joseph W.
Research Associate
University of Cincinnati
9207 Maverick Drive
Cincinnati, OH 45231
DAVIS-HOOVER, Wendy
Graduate Research Asst. #254
University of Cincinnati
3554 Amberway
Cincinnati, OH 45231
HORAN,JohnM.,M.D.
NIOSH
4676 Columbia Parkway
Cincinnati, OH 45226
HOWELL, E. Stallings
Project Manager
Florida Sect., Water Div., EPA
345CourtlandSt.,NE
Atlanta, GA 30308
HSIAO, Joyse S.
Engineering-Science
600 Bancroft Way
Berkeley, CA 94710
HSU, Deh Yuan
Process Engineer
Greeley & Hansen, Engineers
222 S. Riverside Plaza
Chicago, IL 60606
HUNDT, Thomas
Environmental Assessment Council
789 Jersey Avenue
New Brunswick, NJ 08902
HUNT, Vilma R.
Deputy Assistant Administrator for
Research Development
US EPA
401 M Street, SW
Washington, D.C. 20460
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360
Wastewater Aerosols and Disease
HUTZLER, Neil
Michigan Technological University
Haughton, MI 49931
JABLONSKI, Edward B., P.E.
Senior Project Engineer
Cullinan Engineering, Co., Inc.
200 Auburn Street
Auburn, MA 01501
JACKSON, Arthur
Cincinnati Health Dept.
3101 Burnett Avenue
Cincinnati, OH 45229
JAFFA, RandyeS.
Research Assistant
University of Cincinnati
Clinical Virology
231 Bethesda Avenue
Cincinnati, OH 45267
JAKUBOWSKI, Shirley A.
6907 Maidmarian Court
Cincinnati, OH 45237
JAKUBOWSKI, Walter
Epidemiology Branch
US EPA, HERL
26 W. St. ClairSt.
Cincinnati, OH 45268
JOHNSON, Donald E., Dr.
Southwest Research Institute
P.O. Drawer 28510
San Antonio, TX 78784
JONES, Ancil A.
Regional Staff Engineer
US EPA, Region VI
1201 Elm Street
First International Building
Dallas, TX 75270
JONES, Baxter L.
Environmental Biologist
JTC Environmental Consultants
7979 Old Georgetown Road
Bethesda, MD 20014
JORDAN, John H., Dr.
Environmental Engineer
US EPA, Region V, Water Div.
230 South Dearborn
Chicago, IL 60604
JORDAN, W. R.
Proctor & Gamble Co.
6100 Center Hill Road
Cincinnati, OH 45224
KAPER, James, Dr.
Senior Fellow
University of Washington
Dept. of Microbiology
Seattle, WA 98195
KEYER, John
Louisville-Jefferson County Dept. of
Public Health
400 East Gray Street
Louisville, KY 40202
KIMBALL, KayT.
Southwest Research Institute
3600 Yoakum Blvd.
Houston, TX 77006
KRABBENHOFT, Kennedy L., Dr.
Professor-Microbiology
Mankato State University
Dept. of Biological Sciences
Mankato, MN 56001
KOMINSKY, John
National Institute for Occupational
Safety and Health
4676 Columbia Parkway
Cincinnati, OH 45226
KOWAL, Norman Edward
Research Medical Officer
US EPA,HERL
25 W. St. Clair St.
Cincinnati, OH 45268
KRAEMER, Dale
US EPA, HERL
26W. St. ClairSt.
Cincinnati, OH 45268
KREMER, Fran
Environmental Scientist
University of Cincinnati
424 Riddle Road, Apt. IB
Cincinnati, OH 45220
LANCELLOTTI, Kenneth D.
US EPA, Marine Field Station, HERL
438 Liberty Lane
West Kingston, RI 02892
LANG, Stephen A.
District Engineer
Ohio EPA, NWDO
1035 Devlac Grove Drive
Bowling Green, OH 43402
LANTIS, Richard B., Engr.
Systems Technology Corp.
245 N. Valley Road
Xenia, OH 45385
LEDBETTER, Joseph O., Dr.
The University of Texas at Austin
8.6 Cockrell Hall
Austin, TX 78712
LEMBKE, Linda
Ames Lab
Iowa State University
Ames, IA 50011
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361
LENHART, C. F.
Project Manager
Sanitary Engrg. Dept., Mongt. Cty.
4221 Lamme Road
Dayton, OH 45439
LEONG, Lawrence Y.C.
Laboratory Director
James M. Montgomery, Consult. Engrg.
555 E. Walnut Street
Pasadena, CA 91101
LESEMAN, William G.
Lab Director
City of Tallahassee
1815 Lk. Bradford Road
Tallahassee, FL 32304
LINDAHL, Philip, P.E.
Environmental Officer
City of Des Plaines
1420 Miner St.
Des Plaines, IL 60016
LINNEMANN, Calvin C., Jr., Dr.
Kettering Laboratory
University of Cincinnati Medical Center
3223 Eden Avenue
Cincinnati, OH 45267
LONG, Maxine
US EPA, Quality Assurance Office
Region V
536 S.Clark
Chicago, IL 60605
LONGEST, Henry L.
Deputy Asst. Administrator for Water
Program Operations
US EPA
Washington, D.C. 20460
LUCAS, James B., Dr.
Deputy Director, HERL, US EPA
26 W. St. ClairSt.
Cincinnati, OH 45268
LUE-HING, Cecil, Dr.
Metropolitan Sanitary District of
Greater Chicago
100 East Erie St.
Chicago, IL 60611
LUND, Ebba, Dr.
Professor of Virology & Immunology
Royal Agricultural & Veterinary Univ.
Bulowsvej 13
1870 Copenhagen V
Denmark
LUNDHOLM, Monica
Department of Environmental Hygiene
University of Gothenburg
Pack
400 33 Gothenburg
Sweden
LYND, Edgar
Senior Sanitary Engineer
Dept. of Environmental Quality
522 S.W. 5th Avenue
Portland, OR 97204
MacKINNON, D.
Chemist
Wastewater
120 E. First St.
Monroe, MI 48161
MAJETI, VimalaA.,Dr.
Kettering Laboratory
Dept. of Environmental Health
University of Cincinnati
3223 Eden Avenue
Cincinnati, OH 45267
MARKE, Gayle E.
Vice President
Trace Element, Inc.
460 S. Northwest Highway
Park Ridge, IL 60068
MARTIN, Russell J.
Environmental Engineer
US EPA, Water Div., ILFPS
230 S. Dearborn
Chicago, IL 60604
MARX, Gary F.
Staff Biologist
Lake Michigan Federation
53 Jackson Blvd.
Chicago, IL 60604
MASQUELIER, Ursula B.
University of Cincinnati Medical Center
231 Bethesda Ave., Room 7060-MSB
Cincinnati, OH 45267
MATHUR, Narendra
Sanitary Engineer
D.C. Govt., Dept. of Env. Serv.
Bureau of Air & Water Quality
5010 Overlook Ave., SW
Washington, D.C. 20032
MATSCHKE, Donald E., President
D.E. Matschke Company
Two Salt Creek Lane
Hinsdale,IL 60521
MATTERS, Mildred F.
Arizona Dept. of Health Services
1740 West Adams
Phoenix, AZ 85007
MAYO, Francis T.
Director of Municipal Environmental
Research Laboratory
US EPA
26W. St. ClairSt.
Cincinnati, OH 45268
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362
Wastewater Aerosols and Disease
McBRIDE, John
Arco Environmental, Inc.
2115DeLaCruzBIvd.
Santa Clara, CA 95050
McCABE, LelandJ.
Director, Field Studies Division
HERL, US EPA
26 W. St. ClairSt.
Cincinnati, OH 45268
McINTIRE, Michael G.
Lafayette Wastewater Treatment Plant
20 N. 6th St., City Hall
Lafayette, IN 47901
MIDAY, Robert, Dr.
HERL, US EPA
26W. St. ClairSt.
Cincinnati, OH 45268
MILLER, Grayson B., Jr., Dr.
Director, Division of Epidemiology
Virginia State Dept. of Health
109 Governor St., Room 701
Richmond, VA 23219
MISKOWSKI, Diane
Princeton Testing Lab
U.S. Route 1
Princeton, NJ 08540
MORI, Tadahiro, Dr.
Japan Sewage Works Agency
No. 5141, Nishihara, Shimosasame,
Toda-City, Saitama-Pref., 335
Japan
MURPKEY, Bill
Illinois Dept. of Natural Resources
309 W. Washington
Chicago, IL
MURRAY, T. J.
Westchester County
Asst. Director Wastewater Trmt.
400 County Office Bldg.
White Plains, NY 10601
NARKIS, Nava, Dr.
Senior Lecturer
Environmental & Water Resources
Engrg.
Technion, Technion City,
Haifa, Israel
NEAL, Anneke
School of Public Health
University of Illinois at the Medical
Center
P.O. Box 6998
Chicago, IL 60680
NELLOR, Margaret
Project Engineer
L.A. Cty. Sanitation Districts
1955 Worman Mill Road, P.O. Box 4998
Whittier.CA 90607
NORTHROP, Robert L., Dr.
School of Public Health
University of Illinois at the Medical
Center
P.O. Box 6998
Chicago, IL 60680
NOVAK, Boris M.
Civil & Sanitary Engineer
Swiss Federal Inst. of Technology
Hinterbergstrasse 75
8044 Zurich,
Switzerland
NUTTER, Wade L., Dr.
Associate Professor
University of Georgia
School of Forest Resources
Athens, GA 30602
O'BRIEN, Parnell
Metropolitan Sanitary District of
Greater Chicago
2420 E. Oakton, Unit E
Arlington Heights, IL 60001
ODEWALD, Robert G.
Div. of Env. Control
Union Carbide Corporation
6733 W. 65th St.
Chicago, IL 60604
O'NEILL, Carlos, Eng.
Director of Water Quality Bureau
Environmental Quality Board
P.O. Box 11488
Santurce, Puerto Rico 00910
ONI, Ade, Dr.
Deputy Health Director
Monroe Cty. Health Dept.
111 Westfall Road
Rochester, NY 14692
PADMANABHA, Anantha
Superv. Sanitary Engineer
D.C. Govt., Dept. of Env. Serv.
Bureau of Air & Water Quality
5010 Overlook Ave., SW
Washington, D.C. 20032
PAHREN, Herbert R.
Physical Science Administrator
HERL, US EPA
26 W. St. Clair St.
Cincinnati, OH 45268
PAHREN, Mary K.
9413 Shadyoak Court
Cincinnati, OH 45231
PARKER, Larry A.
Laboratory Chief
US EPA, Region III
Wheeling Field Office
303 Methodist Bldg., 11th & Chapline
Wheeling, WV 26003
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363
PARROTT, James H.
General Manager
Clark County Sanitation District
5857 E. Flamingo Road
Las Vegas, NV 89122
PASK, Wayne M.
Graduate Instructor in Research
School of Civil Engineering
Purdue University
Civil Engineering Building
West Lafayette, IN 47907
PAULLIN, John
Ebon Research Systems
15429th St., NW
Washington, D.C. 20001
PEABODY, Frank R.
Michigan State University
Dept. of Microbiology
East Lansing, MI 48842
PEDERSON, Marshall
Design Engineer
John R. Sansalone & Co.
1008 Marshall Ave.
Cincinnati, OH 45225
PEREIRA, Martin R., Dr.
Environmental Scientist
Gibbs& Hall, Inc.
393 7th Avenue
New York, NY 10001
PHAIR, John, Dr.
Northwestern University Medical
School
Department of Medicine
303 East Chicago
Chicago, IL 60611
PIEH, Samuel H.
Coordinator
Environmental Health Program
Mississippi Valley State Univ.
Itta Bena, MS 38941
POLONCSIK, Stephen
Water Division
US EPA
230 South Dearborn Street
Chicago, IL 60604
POTEAT, Charles S.
Planning Programs Coordinator
Montgomery County Government
100 Maryland Ave., Cty. Office
Rock ville.MD 20850
PURKER, Peter
University of Cincinnati
8989 Mockingbird Lane
Cincinnati, OH 45231
RAMAIREZ, Joe
Safety Officer
Metro. Sewer District
1600 Gest Street
Cincinnati, OH 45204
REED, Robert E.,P.E.
Missouri D.E.Q.
P.O. Box 1368
Jefferson City, MO 65101
REICHARD, V. S.
Dir. Environmental Health
Kern County Health Dept.
1700 Flower St.
BakersfieId,CA93302
RICHDALE, Natalie
Research Assistant
University of Cincinnati
Environmental Health
3223 Eden Avenue
Cincinnati, OH 45267
RICHARDSON, Allyn
US EPA, Region I
John F. Kennedy Federal Building
Boston, MA 02203
RICHARDSON, D. G.
Engineer III
Dept. of Environmental Regulation
2180 W. First St., Suite 401
Ft. Myers, FL 33901
RILEY, Michell Y.
University of Cincinnati
1549 Meredith Drive
Cincinnati, OH 45231
RINGENBACH, Laura A.
Environmental Scientist
US EPA
26 W. St. Clair St.
Cincinnati, OH 45268
RISLEY, Clifford, Jr.
Director, R&D
US EPA, Region V
230 S. Dearborn Street
Chicago, IL 60604
ROESLER, Joseph F.
Regional Liasion Officer
US EPA
26 W. St. Clair St.
Cincinnati, OH 45268
ROHR, Mary-Ellen
US EPA
26 W. St. Clair St.
Cincinnati, OH 45268
ROMAN, Donald F.
Acting Superintendent
Wastewater Treatment
8430 Crestway Drive
Clayton, OH 45315
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364
Wastevvater Aerosols and Disease
ROSE, Milton R.
Texas Dept. of Water Resources
P.O. Box 13087, Capital Station
Austin, TX 78711
ROTH, Thomas P.
President
Anderson Samplers, Inc.
4215-C Wendell Drive
Atlanta, GA 30336
RUSSELL, Sandra
University of Cincinnati
8085 Neshoba Road
Germantown, IN 38138
RYAN, James, Dr.
US EPA
26 W. St. ClairSt.
Cincinnati, OH 45268
RYLANDER, Ragnar, Dr.
Dept. of Environmental Hygiene
University of Gothenburg
Pack 400 33 Gothenburg
Sweden
SAFFERMAN, Robert S., Dr.
US EPA
26W St. ClairSt.
Cincinnati, OH 45268
SAGIK, B.,Dr.
College of Sciences and Mathematics
University of Texas at San Antonio
San Antonio, TX 78285
SANGHAVI, Ashok M.
West Virginia State Health Dept.
1800 Washington St., East
Room 550
Charleston, WV 25305
SAWYER, Bernard
Research Chemist
Metropolitan Sanitary District of
Greater Chicago
5915 W. 39th St.
Cicero, IL 60650
SCARPING, P. V., Dr.
Professor in Env. Engineering
University of Cincinnati
Mail Loc. #71, 721 Rhodes Hall
Cincinnati, OH 45221
SCHAUB, Stephen A., Dr.
U.S. Army Medical Bioengineering
R&D Laboratory
Fort Detrick
Frederick, MD 21701
SCHAUFFLER, Fred
Executive Engineer
New England Interstate Water Pollution
Control Commission
607 Boylston St.
Boston, MA 02116
SCHEFF, Peter, Dr.
School of Public Health
University of Illinois at the Medical
Center
P.O. Box 6998
Chicago, IL 60680
SCHERFIG, Jan
Professor of Civil & Env. Engrg.
University of California
School of Engineering
Irvine, CA 92716
SCHIFF, Gilbert M., Dr.
Christ Hospital Institute of Medical
Research
2141 Auburn Avenue
Cincinnati, OH 45219
SCHWARTZ, David, G.
Industrial Hygienist
509 Norway Avenue
Cincinnati, OH 45229
SEDITA, Salvador J.
Head,Biology Research
Metropolitan Sanitary District of
Greater Chicago
5915 W. Pershing Road
Cicero, IL 60650
SEKLA, L. H. Dr.
Cadham Provincial Laboratory
770 Bannatyne Avenue
Winnipeg, Manitoba R3E OW3
Canada
SEMINARA, Edward L.
Westchester Cty. Deputy Director
Wastewater Treatment
400 County Office Blvd.
White Plains, NY 10601
SEMINARA, Jean M.
400 County Office Blvd.
White Plains, NY 10601
SHEIKH, Bahman
Engineering-Science
600 Bancroft Way
Berkeley, CA 94710
SINGAL, Mitchell, Dr.
NIOSH
4676 Columbia Parkway
Cincinnati, OH 45226
SITMAN, William D.
Director of Engineering
WalterB. Sattertawaite, Assoc., Inc.
11 N. Five Points Road
West Chester, PA 19380
SLOTE, Lawrence, Dr.
Professor/Chairman
Dept. of Occupational Health and Safety
NY University, 715 Broadway
New York, NY 10003
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365
SLOVIN, Donald L., Dr.
NIOSH
4676 Columbia Parkway
Cincinnati, OH 45226
SMITH, Carl, Dr.
Professor of Env. Health
University of Cincinnati College of
Medicine
3223 Eden Avenue
Cincinnati, OH 45267
SMITH, Richard W., P.E.
Chief, Wastewater Mgmt. & Grants
Fla. Dept. of Env. Regulation
2600 Blair Stone Road
Tallahassee, RL 32301
SNELL, Terry D.
Soil Systems, Inc.
525 Webb Industrial Blvd.
Marietta, GA 30062
SORBER, Charles A., Dr.
College of Sciences and Mathematics
University of Texas at San Antonio
San Antonio, TX 78285
SOUTHWORTH, Robert M.
Sanitary Engineer
US EPA, OWPO (WH-547)
401 M Street, SW
Washington, D.C. 20460
SPECKER, Bonny L.
Kettering Laboratory
University of Cincinnati Medical Center
3223 Eden Avenue
Cincinnati, OH 45267
SPENDLOVE, J. Clifton, Dr.
523A Bonafin Drive
Dugway, UT 80422
SPROUL, Otis J., Dr.
Civil Engineering Department
Ohio State University
470 Hitchcock Hall
2070 Neil Avenue
Columbus, OH 43210
SPROUL, Warren W.
City of Springfield
P.O. Box 1208-WWTP
Springfield, OH 45501
STANCZAK, Edmund A., Jr.
General Superintendent
City Utilities
One Main Street
Fort Wayne, IN 46802
STEINER, Joe
Sanitary Engineer
Montana Dept. of Health &
Environmental Science
Helena, MT 59601
STERLING, David A.
3020 Euclid Ave., #2
Cincinnati, OH 45219
STONE, James S., P.E.
President
Stone Environmental Engrg. Services,
Inc.
7131 W. 84th Way, #1604
Arvada, CO 80003
STROUBE, Robert B., Dr.
Dir., Div. of Health Hazards Control
Virginia State Dept. of Health
109 Governor St., Room 701
Richmond, VA 23219
SUGAR, J. William
Linde, Div. of Union Carbide
P.O. Box 44
Tonawanda, NY 14150
SUNDERMAN, Otis L., R.S.
Occupational Health Specialist
Lincoln-Lancaster Cty. Health
Department
2200 St. Marys Avenue
Lincoln, NB 68502
SUSKIND, Raymond R., Dr.
Director, Dept. of Env. Health
University of Cincinnati College of
Medicine
3223 Eden Avenue
Cincinnati, OH 45267
TATMAN, D. Russell, P.E.
President
Tatman & Lee Assoc., Inc.
2005 Concord Pike
Wilmington, DE 19803
THOMAS, Richard
Physical Scientist
US EPA, OWPO (WH-547)
401MSt.,SW
Washington, D.C. 20460
THOMPSON, Larry R.
Mobay Chemical Corp.
Agri. Chemicals Div.
8400 Hawthorn Road, P.O. Box 4913
Kansas City, MO 64120
TOLMAN, A.
Asst. Manager, Env. Science
SML - Martin
900 W. Valley Forge Road
King of Prussia, PA 19406
TOMASHESKI, Jerome
Northeast Ohio Regional Sewer Dist.
3090 Broadway
Cleveland, OH 44115
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366
Wastewater Aerosols and Disease
TORRUSIO, Michael
General Council
Room 2325
NYC Dept. of Environ. Protection
1 Center Street
New York, NY 10007
TURNER, Andrew
Asst. Office Chief
Ohio EPA
361 E. Broad St.
Columbus, OH 43215
VAJDIC, Ann H.
Project Mgr. Microbiology
Environment Ontario
13SSt. ClairAve. West
Toronto, Ontario
Canada
VANDOREN.GuyD.
Project Engineer
Hazen & Sawyer
360 Lexington Avenue
New York, NY 10017
VAN MEER, Gretchen L., Dr.
Kettering Laboratory
University of Cincinnati Medical Center
3223 Eden Avenue
Cincinnati, OH 45267
VAN VALKENBURG, Charles
Env. Protection Specialist I
EPA
2200 Churchill Road
Springfield, IL 62706
VENOSA, Albert D., Dr.
Research Microbiologist
US EPA, MERL
26 W. St. ClairSt.
Cincinnati, OH 45268
VOCES, Thomas F.
Assistant Director
Air & Water Control 2-110
Inland Steel Co.
3210 Watling Street
East Chicago, IN 46312
VORNBERG, Daniel L.
Vice President
Envirodyne Engineers, Inc.
12161 Lackland Road
St. Louis, MO 63141
WADDEN, R. A.
University of Illinois School of Public
Health
P.O. Box 6998
Chicago, IL 60680
WAGNER, Edward O.
Chief, Div. of Plant Operations
Dept. of Env. Protection, NYC
Wards Island
New York, NY 10035
WAGNER, Ralph
Union Carbide
120 S. Riverside
Chicago, IL 60606
WALDMAN, Mariam, Dr.
Life Sciences Div. - NCRD
Kiryat Ben Gurion, Bldg. 3
Jerusalem, Israel 91000
WALKER, John M., Dr.
US EPA, OWPO (WH 547)
Washington, D.C. 20460
WARD, Richard, Dr.
Sandia Laboratories
Albuquerque, NM 87185
WATANABE, Arthur S.
NIOSH, DSHEFS, HETAB, MS
4676 Columbia Parkway
Cincinnati, OH 45226
WATSON, A. E. P., Dr.
Scientist
International Joint Commission
100 Ouellette Ave., 8th Floor
Windsor, Ontario N9A 6T3
Canada
WELLS, W. H. Jr.
Kittering Laboratory
University of Cincinnati
3223 Eden Avenue
Cincinnati, OH 45267
WEIR, Hannah K.
Data Technician
University of Cincinnati
Environmental Health Dept.
3223 Eden Avenue
Cincinnati, OH 45267
WENCK, Norman
Vice President
Hickok & Associates
545 Indian Mound
Wayzata, MN 55391
WESTERFIELD, Rick
Environmental Engineer
Woolpert Consultants
2324 Stanley Avenue
Dayton, OH 45404
WESTFALL, Brian A.
Environmental Engineer
Industrial Env. Research Lab
5824 Ridge Ave., Apt. 8
Cincinnati, OH 45213
WESTMAN, T. R.
Laboratory
Muskegon Cty. Wastewater Mgmt.
System
8301 White Road
Muskegon, MI 49442
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Registration List
367
WHEELER, Brian L.
W. Virginia State Health Dept.
1800 Washington St., East
Charleston, WV 25305
WILLIAMS, Gary H.
Chief, Env. Engineering Branch
US EPA, Region V, Water Div.
230 S. Dearborn St.
Chicago, IL 60604
WILLIAMS, H. Douglas
Center for Environmental Research
Information
US EPA
26 W. St. Clair St.
Cincinnati, OH 45268
WILLIFORD, Charles H.
Environmental Engineer
Bureau of Pollution Control
P.O. Box 827
Jackson, MS 39205
WILSON, Carl D.
Nonpoint Source Coordinator
US EPA, Water Div.
Water Quality Policy Section
230 S. Dearborn St.
Chicago, IL 60604
WINSLOW, Brian A.
Project Engineer
URS Company
North 4407 Div., Suite 815
Spokane, W A 99207
WITHAM, Clyde L.
Chemical Engineer
SRI International
333 Ravenswood Avenue
Menlo Park, CA 94025
WITHERELL, Linden E.
EPA, Vermont Field Office
Prouty Federal Bldg., Box 35
Essex Junction, VT 05452
WITHEROW, Jack L
EPA - Land Treatment Task Force
P.O. Box 1198
Ada, OK 74820
WOJCIK, Gene
Chief, EIS Section
US EPA, Env. Engrg. Branch
230 S. Dearborn St.
Chicago, IL 60604
WOLOCHOW, H.
Naval Biosciences Laboratory
University of California
Naval Supply Center, Bldg. 844
Oakland, CA 94625
WONG, Philip M.
EPA
Washington Operations Office
c/o DOE Southwest Region (LU 11)
Olympia.WA 98504
WRIGHT, Michael David
Tulsa City-County Health Dept.
4616 E. 15th St.
Tulsa, OK 74112
YARK, Donald J., P. E.
Erie County Sanitary Engineer
Erie County, Ohio
1200 Sycamore Line, P.O. Box 549
Sandusky, OH 44870
YIN, Bryan
US EPA
Water Operations N/S 429
1200 Sixth A venue
Seattle, WA 98101
YU, Ta-Shon, Chief
Maryland State Env. Health Admin.
201 W. Preston Street
Baltimore, MD 21201
ZENZ, David R.
Metropolitan Sanitary District of
Greater Chicago
5915 W. 39th Street
Cicero, IL 60650
ZIMMERMAN, Neil J.
Graduate Research Assistant
University of North Carolina at Chapel
Hill
Room 129, School of Public Health
Chapel Hill, NC 27510
ZULTOWSKI, Tom
President, Local 1320
c/o District Council 37
140 Park Place
New York, NY 10007
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