f/EPA
United States
Environmental Protection
Agency
Health Effects Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S1-81-002 Mar. 1981
Project Summary
Health Risks of Human
Exposure to Wastewater
C. S. Clark, C. C. Linnemann, Jr., G. L Van Meer, G. M. Schiff, P. S. Gartside,
A. B. Bjornson, E. J. Cleary, J. P. Phair, C. R. Buncher, D. L. Alexander, S. E.
Trimble, and B. C. Barnett
I
The primary objective of this
research was to determine the health
effects associated with occupational
exposure to biological agents present
in municipal wastewater. An addi-
tional objective was to determine the
sensitivity of the 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 sero-
epidemiologic study applied to
municipal wastewater workers and
controls in three metropolitan areas:
Cincinnati, Ohio; Chicago, Illinois;
and Memphis, Tennessee. The
primary study group consisted of
more than 100 workers 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, a Chicago group of 30 expe-
rienced sewage treatment plant
workers were included and, in
Cincinnati, two other wastewater-
exposed groups were recruited con-
si sting of about 50 sewer
maintenance workers and 50 primary
wastewater treatment plant workers.
The latter group was recruited into the
study just before start-up of plant
improvements that included activated
sludge facilities. The purpose of
including this group was to differen-
tiate between aerosol exposure and
exposure to wastewater and sludge
through those operations associated
with primary wastewater treatment.
The protocol involved quarterly col-
lection of blood, throat, and rectal
swabs; yearly medical examinations;
collection of illness information; work
observations; and environmental
monitoring. Initial recruitment of
workers began April 1975 in
Cincinnati; July 1976 in Chicago; and
July 1977 in Memphis. Final speci-
mens in all cities were collected in the
fall of 1978. The serological survey
included testing for antibodies to a
large group of viruses and bacteria and
determination of immunoglobulin
levels. Work observations were used
to evaluate the level of the workers'
contact with wastewater and, in con-
junction with the biological air moni-
toring, to assess the extent of contact
with aerosols. The environmental
monitoring included viral and bacterial
analyses of wastewater and the use of
six-stage Andersen samplers to deter-
mine the respirable concentrations of
bacteria in the work areas of the plant.
A total of over 500 volunteers
participated in the.study including
both subjects and controls.
This Project Summary was devel-
oped by EPA's Health Effects Re-
search Laboratory, Cincinnati, OH, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
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Introduction
Objectives
The purpose of this study was to
determine the health effects, if any, of
the occupational exposure to the
viruses, bacteria, and parasites present
in municipal wastewater. The central
feature was an extensive surveillance
of the health of 100 newly-hired
activated sludge treatment plant
workers during a minimum of 12
months of occupational exposure to
wastewater. Specific objectives of the
project were:
1. To determine whether wastewater
workers develop clinical illness or
specific bacterial, viral, and para-
sitic infections due to occupational
exposure to sewage
2. To determine the immunologic re-
sponse among workers presumed
to be exposed to a high level of anti-
genic simulation, i e., through
wastewaters.
3. To determine whether wastewater
workers serve as a reservoir of
certain infections and, if so,
whether members of the workers'
families are affected.
4 To determine the effect of exposure
10 aerosols generated by the acti-
vated sludge treatment process.
5 To determine the concentration of
bacterial aerosols at wastewater
treatment plants, and to compare
them to levels at other public works
facilities.
An underlying objective of the study
was the determination of the sensitivity
of various elements of the epidemio-
logical-serological approach for the
detection of wastewater-related health
effects Such a determination would
permit an assessment of the potential
application of this methodology to the
study of health risks associated with
other population exposures to waste-
waters. The latter would include
persons working with or living near
wastewater land-disposal facilities,
persons living in the vicinity of waste-
water treatment plants, and persons
engager ~i recreational use of bodies of
water receiving waste effluents.
Background
Information regarding the human
health risks associated with contact
with wastewater and related materials
brought about by occupational and
other exposures is limited. However,
assumptions concerning these risks are
providing motivation for the
promulgation of state and federal
standards designed to protect
populations from various wastewater
Table 1. List of Viruses, Bacteria,
and Immunoglobulins for
Which Workers' Sera
Were Tested for Anti-
bodies.
Viruses
1. Polio 1, 2, and 3
2. Coxsackie A-7, A-9, A-16, A-21,
and B-1 to B-6
3. Echo 1, 3, 4, 5, 6. 8, 9, 11, 13, 14,
19, 24, 30
4. Reov/rus
5. Adenovirus
6. Cytomega/ovirus
7. Herpes simplex
8. Hepatitis A antibody and Hepatitis B
antibody and antigen
Test Methods: M/croneutra/iza-
tion for Polio, Coxsackie and all
Echo viruses; Radioimmuno-
assay for Hepatitis A and B; and
Complement Fixation for the
others.
Bacteria
1. Salmonella: Group A, B, C, D, andE
Test Methods' Rapid slide agglu-
tination (1975-1976)
Microagglutination (1978)
2. Leptospira
Test Method: Microagglutination
3. Legionella pneumophila
Test Method: Indirect immuno-
fluorescence
Immunologic Factors
1. IgA
2. IgG
3. IgM
4. Rheumatoid Factor
Test Methods: Radial immunodif-
fusion for immunoglobulins,
latex reaction for rheumatoid
factor
exposures. The growing emphasis on
the land application of wastewater and
sludges as a viable method of wastes
utilization increases the need for
reliable and up-to-date information on
the health risks, if any, involved.
Wastewater also contains a wide
variety of harmful chemicals which may
under some conditions compromise the
health of wastewater workers.
However, chemical hazards were not
considered in this study.
Methods
The study consisted of an intensive
serologic survey correlated with epide-
miological, clinical, and environmental
data on the study populations. The
central feature of the design was an
evaluation of the effects of occupational
exposure to wastewater over at least a
12-month period based on the
measurement of specific viral and
bacterial antibodies and immunoglobu-
lin in sera collected over that time
period In order to help separate the
effect of the occupational exposure from
that associated with other possible
disease pathways, appropriate control
groups were utilized. In addition, many I
of the wastewater workers were
recruited into the study at the time of
their initial employment m the waste-
water treatment industry
Each quarter blood samples, throat
swabs, and fecal samples were
collected from participants in the study.
Blood specimens were used for the
serologic surveys and the throat swabs
and fecal specimens were used for
analysis for bacteria, viruses and
parasites. (Parasitic examinations were
performed only during the early period
of the study in Cincinnati.)The serologic
survey involved the determination of
antibodies to a group of viruses and
bacteria and measurement of
immunoglobulm levels (Table 1). Of
concern in the serologic survey was
whether the prevalence and level of
antibodies were different in the
wastewater exposed and control
groups,and whether the number of
infections as indicated by increases in
antibody concentration was different
among the various study groups.
Illness information was obtained by
monthly health diaries maintained by
the workers supplemented by telephone
and on-the-job contact. Illness symptom
information from all sources wasj
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combined in a mannerdesignedtoavoid
double counting and was categorized as
"respiratory," "gastrointestinal," and
"other." The data processing proce-
dures provided for coding various
possible combinations of these The
definition of these illness categories
was based on the symptoms indicated
on the health diary, as follows.
Respiratory - Cold symptoms,
sore throat, cough
or other lower res-
piratory symptoms.
Gastrointestinal - Nausea, vomiting,
diarrhea, or intesti-
nal upset
Other - Fever, persistent
headache, eye in-
flammation or other
eye trouble, ear-
ache or other ear
trouble, skin infec-
tion, rash, boils, or
open sores.
From time to time job locations of
participants were visited to determine
types and levels of exposure and other
work conditions. Work site air was
monitored periodically for bacterial
concentrations, and concurrent
wastewater samples at the wastewater
treatment plants were analyzed for
bacterial and viral concentrations. Six-
stage Andersen samplers were use'J to
collect the airborne bacteria. In order to
process the air samples as soon as
possible, preparation and analyses of
the plates for bacterial sampling were
performed in Chicago by the
Metropolitan Sanitary District of
Greater Chicago (MSDGC), in Memphis
by the Memphis State University, and
by the bacteriologist on the study staff
in Cincinnati. All wastewater samples
for virus assay were processed by the
aluminum hydroxide continuous flow
centrifuge technique and assayed by a
plaque assay procedure.
On a yearly basis, study volunteers
were offered a medical evaluation that
included hematology, urmalysis, pul-
monary function testing, blood chem-
istry (including tests of liver and kidney
function), and examination by a physi-
cian.
A number of comparisons and
correlations were made from the
epidemiological, environmental,
t clinical, and serological aspects of the
study.
As initially conceived, the study goals
were limited to the first three specific
objectives listed above The population
groups planned for the study were
sewer and highway maintenance
workers in Cincinnati. The research
design initially called for recruitment of
an equal number of menbegmning their
respective jobs as those recruited who
had two or more years experience, for
both exposed and control groups. Soon
after the study was initiated economic
conditions in the municipal government
forced a moratorium on hiring new
employees in the Cincinnati Public
Works Department which eliminated
prospects for establishing a newly
employed highway maintenance study
group.
About one year after this research
began, its goals were expanded to
include a determination of the health
effects associated with the dispersion of
aerosols generated by the activated
sludge wastewater treatment process
(Specific Objectives 4 and 5). At this
time the study design was expanded to
include two additional exposed popula-
tion groups: 50 men 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 a total of 100 men
newly employed at activated sludge
treatment plants. Since only one-third
of the 100 inexperienced activated
sludge plant workers were expected to
be available in Cincinnati, thestudy was
expanded to include workers at the
plants in Chicago and Memphis. These
cities were chosen because at least 50
new employees would be hired within
the next year, the plants contained the
activated process in open basins with
porous plate-type diffusers, they were
reasonably accesible to Cincinnati, and
the plant administrators were
agreeable to the study. MSDGC hired a
significant number of new workers
because of normal work force turnover
by virtue of its size. In addition, its long
experience in wastewater treatment
and the technical support for
monitoring available from its Research
and Development Department made it
very suitable for study. Memphis was in
the final stages of construction of its
second activated sludge treatment
plant, the North Treatment Plant, an
entirely new facility. In addition, its first
plant, the Maxson Wastewater
Treatment Plant had plans to hire more
workers.
Comparison groups in Cincinnati,
Chicago and Memphis were highway
maintenance water treatment plant
workers and gas and electric utility
workers, respectively.
Conclusions
1. Gastrointestinal illness rates were
higher in the inexperienced waste-
water exposed workers than in the
experienced workers and controls,
Wastewater workers were not
found to be subject to any
detectable risks due to parasites
present in wastewater. There was
only slight evidence, if any, to sug-
gest that there were risks due to
viruses and bacteria in wastewater.
2. Immunoglobulm levels were not
found to be consistently higher in
wastewater-exposed workers than
in controls in any of the cities
studied.
3. Wastewater workers were not
found to serve as a source of viral
infections for their family members.
4. In a few instances levels of antibody
to certain viruses appeared to be
related to level of exposure to
wastewater aerosols.
' 5. Bacterial aerosol levels in buildings
where wastewater sludge was
being processed were generally
higher than levels adjacent to out-
door aeration tanks at the same
treatment plants.
6. Since the seroepidemiologic ap-
proach did not detect any
significant health effects of occu-
pational exposure to wastewater, it
is unlikely that this approach would
detect potential health impacts in
populations with lower levels of
exposure to wastewater.
Recommendations
Since the basic design of this study
was to compare antibody levels
between two quarters in each year of
the study, all sera collected over the
entire study period have not been
tested. It is possible that changes in
antibody levels were not detected by
semiannual testing. Selected viruses of
high prevalence should be studied by
testing all sera for each individual.
> US GOVERNMENT PRINTING OFFICE 1M1-757-02I/70J2
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Because the predominance of
seroconversions to Hepatitis B were in
the sewage-exposed groups (seven of
123 sewage-exposed workers com-
pared to one of 52 control workers),
additional testing should be done on
workers not yet evaluated to determine
whether this trend persists.
Additional testing of sera of workers
occupationally exposed to soil, such as
some sewer and highway maintenance
workers, would be useful m attempting
to verify previous suggestions that soil
exposure increases the risk of infection
to Legionella pneumophila
Because of the limited testing of sera
for antibody to Hepatitis A, the initial
sera of a number of workers has not
been tested. It would be useful to test
these sera to determine whether any of
these people acquired the antibody
during the course of the study
Serologic testing for rotavirus or
parvovirus agent was not performed
during the study. Since these viruses
are now recognized as a major cause of
gastrointestinal illness, the sera col-
lected during the study should be
analyzed for antibody to them.
C. S. Clark, C. C. Lmnemann, Jr., G. L. Van Meer, G. M. Schiff, P. S. Gartside.
A. B. Bjornson, E. J. deary, J. P. Phair, C. R. Buncher, D. L. Alexander,
S. E. Trimble, and B C. Barnett are with the University of Cincinnati Medical
Center, Cincinnati, OH 45267.
Walter Jakubowski is the EPA Project Officer (see below).
The complete report, entitled "Health Risks of Human Exposure to Waste-
water," /Order No. PB 81-143 406; Cost: $15.50, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Spring field, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at.
Health Effects Research Laboratory
U S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
230 S bEAH»0»^
CHIC AGO Jtj
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