EPA-600/4-76-018
April 1976
Environmental Monitoring Series
DESIGN OF POLLUTANT-ORIENTED
INTEGRATED MONITORING SYSTEMS
A Test Case:
Environmental Lead
Environmental Monitoring and Support Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Las Vegas, Nevada 89114
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL MONITORING series.
This series describes research conducted to develop new or improved methods
and instrumentation for the identification and quantification of environmental
pollutants at the lowest conceivably significant concentrations. It also includes
studies to determine the ambient concentrations of pollutants in the environment
and/or the variance of pollutants as a function of time or meteorological factors.
This document is available to the public through the National Technical Informa-
tion Service. Springfield, Virginia 22161.
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EPA-600/4-76-018
April 1976
DESIGN OF POLLUTANT-ORIENTED INTEGRATED
MONITORING SYSTEMS
A Test Case: Environmental Lead
edited by
Dale W. Jenkins
National Institute of Scientific Research
Rancho Santa Fe, California 92067
Contract Number 68-03-0443
Project Officer
Edward A. Schuck
Monitoring Systems Research and Development Division
Environmental Monitoring and Support Laboratory
Las Vegas, Nevada 89114
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
ENVIRONMENTAL MONITORING AND SUPPORT LABORATORY
LAS VEGAS, NEVADA 89114
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DISCLAIMER
This report has been reviewed by the Environmental Monitoring and
Support Laboratory-Las Vegas, U.S. Environmental Protection Agency, and
approved for publication. Approval does not signify that the contents
necessarily reflect the views and policies of the U.S. Environmental
Protection Agency, nor does mention of trade names or commercial products
constitute endorsement or recommendation for use.
ii
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CONTENTS
List of Figures iv
List of Tables v
I Introduction 1
II Concept of an Integrated Monitoring System 2
III Evaluation of Concept Using Lead as a Test Case 6
Critical Receptor Population 6
Critical Transport Pathways and Portals of Entry 15
Critical Sources 34
Quantitative Mathematical Models 36
Basic Research Requirements 42
Research Monitoring Requirements 45
Design of an Integrated Monitoring System 46
IV Conclusions 47
V Participants in the Workshop 48
References 50
iii
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LIST OF FIGURES
Figure Page
1 Calculated Lead Body Burden Comparison
Between Adult and Child 9
2 Major Pathways Affecting Lead Burden
in Critical Receptor 16
3 Lead Exposure Pathways to Critical Receptor 17
4 Pathways of Lead in Critical Receptor 18
5 Average Lead Size Distribution Comparison, with
Junge's Model for Continental Aerosols on Log-
Probability Paper 21
6 Pathways of Lead to a Receptor Via the Water Cycle 29
7 Pathways of Lead to a Receptor Via Liquids Other
Than Water 30
8 Spatial Distribution of Lead Concentration in Air 41
9 Hypothetical Exposure Cross Section to Total
Atmospheric Lead in a Typical Urban Area 43
iv
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LIST OF TABLES
Number Page
1 Atmospheric Lead Concentrations 19
2 Lead Dust on and Near Heavily
Traveled Roadways 22
3 Lead Dust in Residential Areas 23
4 Lead at Soil Surfaces 24
5 Lead in Diet of Adult Males 25
6 Diet of 15-20 Year Old Males 26
7 Lead in Diet of Children 26
8 Lead in Fresh and Processed Foods 27
9 Lead Content of Various Beverages in
Milligrams per Liter 32
10 Lead in New York Area Milk 32
11 Lead Consumption in the United States 35
12 Emission Sources of Lead in Air 35
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I. INTRODUCTION
Environmental monitoring assesses the types and amounts of pollutants in
the environment and determines if sensitive human populations or other suscep-
tible receptors are exposed to levels and durations of exposure to pollutants
that may cause adverse effects.
It is convenient to define the concepts of "critical receptors" and "crit-
ical sources" when discussing the biological effects of pollutants. A critical
receptor will be defined to be that subgroup of animals or plants which shows
a measurable or observable effect at a dose or exposure of the specified pollu-
tant lower than any other group. A critical source is that single source that
contributes more than any other source to the fate of the critical receptor.
Typically, but not necessarily, if a critical source is eliminated the debili-
tating effect on the critical receptor will be eliminated.
It is absolutely necessary to assure that monitoring measurements are
directly related to the critical receptors at risk and to critical sources
amenable to some control or modification. As we gain more experience and
knowledge about pollutants, critical receptors, and critical sources, we also
need to carefully review existing, ongoing, and planned monitoring networks to
see that they provide the most pertinent data possible.
The concept of an integrated monitoring system was developed to coordinate
complex information about the relationships of pollutants, critical sources,
and critical receptors. The concept considers many aspects of the problem at
once and it defines, quantifies, and compares specific factors about each pollutant.
An integrated monitoring system is a systems approach for providing the
information required to permit efficient control of critical sources of pol-
lutants causing major problems or threats in critical receptors. Traditionally
most monitoring programs assess only single pathway systems but, in contrast,
integrated monitoring attempts to assess total exposure to a pollutant or
combination of pollutants.
Design of an integrated monitoring system that will provide the desired
exposure assessment requires much specific information. The major areas of
concern and the sequence of steps in designing a system include identifying
the sources, critical receptors and major transport pathways, determining
dosages via major portals of entry into receptors, and identifying and locat-
ing major critical sources, especially those amenable to control. In order to
organize this information to evaluate the relative importance of different
components, a mathematical model appears to be of value. Models will help
determine basic research needs and research monitoring requirements, and will
help in the design of an integrated monitoring system or network.
It was desired to test the validity of the concept of integrated monitor-
ing systems and to examine the criteria and steps involved. A test case was
undertaken by a "Workshop for the Design of a Pollutant-Oriented Integrated
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Monitoring System" conducted at the National Environmental Research Center* at
Las Vegas, Nevada, in March 1974. Medical and environmental specialists were
convened to evaluate the concepts using a selected test-case pollutant.
The pollutant was selected using the following criteria: a) a large amount
of data is available on the pollutant and its effects, b) it would probably il-
luminate most of the problems in designing an integrated monitoring system,
c) it should reach man through several environmental pathways, d) the pollutant
should cause significant effects in humans, and e) design of a system might be
of value for monitoring the selected pollutant. Lead, which seemed to best fit
these criteria, was the pollutant selected.
The following report critically examines the concept using this system ap-
proach and points out the values and problems. The review pointed out important
knowledge gaps, basic research needs, and research monitoring requirements. The
use of mathematical models appears to be valuable, but more detailed testing and
evaluation of models is required to establish their validity and usefulness.
II. CONCEPT OF AN INTEGRATED MONITORING SYSTEM
The concept of an integrated monitoring systems approach which takes into
account simultaneously the critical receptor, critical transport pathways, and
critical sources is relatively new. The term "critical" is used to designate
a specific and important population at risk and the special transport pathways
from the important sources which impact this receptor population. While all
sources and pathways are included, instead of general ambient environment mon-
itoring, special monitoring of the major pollutant chain involved is done spe-
cifically to permit control of critical sources. This concept includes the
following considerations: a) critical receptors, b) critical transport path-
ways and portals of entry, c) critical sources, d) mathematical models, e) basic
research requirements, f) research monitoring requirements, g) design of an
integrated monitoring system.
The concept is presented below with a detailed outline of the factors in-
volved and a discussion of models. This outline provided the workshop with
the structure for analysis of the concept using the test-case pollutant, lead.
A. Critical Receptor Population
1. Determine Critical Receptor
a. Population with greatest exposure risk (number of persons
exposed to greatest concentration of pollutant).
b. Population most sensitive with lowest threshold of effects.
c. Population actually showing most effects.
* This Center became the Environmental Monitoring and Support Laboratory-Las
Vegas effective June 29, 1975.
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2. Medical Effects
a. Determine daily dosage, absorbed dosage, retention, and
excretion rates.
b. Determine minimum threshold of effects of pollutants for
both acute high dosage and chronic low dosage in adults
and children.
c. Determine changes and trends in body burden levels and
effects with time.
B. Critical Transport Pathways and Important Portals of
Entry into Receptor
1. Determine dispersion and dissemination of pollutant into
the environment.
2. Determine major transport pathways and special areas of
accumulation or concentration of pollutant in the environ-
ment.
3. Determine critical pathways from critical sources to critical
receptor.
4. Quantitate total amounts and rates of flow of pollutant in
critical transport pathways in different media.
5. Quantitate special pathways and portals of entry, e.g.
placental transfer from mother.
6. Quantitate amount of pollutant entering (the portals of
entry) of the receptor.
C. Critical Sources
1. Identify sources, both natural and man made, and develop
an emissions inventory.
2. Identify critical sources which are of importance to the
critical receptor via identified major transport pathways.
3. Determine mass emission rate for each major type of source,
both mobile and stationary.
4. Determine chemical composition and particle or aerosol size
distribution for each major type of source.
5. Determine changes of sources and trends with time.
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D. Quantitative Mathematical Models
1. General Model
A mathematical model can be of great value in helping to select from
various alternatives the relative importance of various sources, pathways,
and routes of entry of a pollutant into a receptor. It may be of value in
showing the use and limitations of presently available quantitative data and
showing the relative importance of obtaining required missing data. The model
can help in assigning priority in determining research data requirements,
research monitoring requirements, and in design of an integrated monitoring
system.
A deterministic mathematical model appears to be suitable for simulating
pollutant dispersal to a receptor. This type model usually requires much fewer
data than statistical models. However, follow-up experiments for validating
the model are required in order to assure the adequacy of the deterministic
model. A hierarchical systems approach is used in which the top echelon general
model covers the entire system. Lower levels of the hierarchy of models include
submodels for specific components which interact with and become an input to
the general model.
2. Submodels
Submodels can be developed for each process or compartment of the general-
ized model. Of particular interest in the integrated monitoring system is the
transport or distribution model from the source through the environment to the
receptor.
A submodel for transport and diffusion can be developed which includes
only diffusion from one or more sources. Submodels can also include entry and
absorption in the receptor. A number of atmospheric transport models have been
developed. Mathematical diffusion models for specific metropolitan areas have
been developed with varying degrees of sophistication. Examples are the
Travelers Research Corporation model (Hilst, 1969) and the Argonne National
Laboratory model (Roberts, et al., 1969) which are short-term period models
with daily predictions of concentrations. An air quality diffusion model by
Martin and Tikvart (1968) permits calculation of seasonal or monthly concentra-
tions of any pollutant.
A submodel on atmospheric pollutant transport was developed by Battelle
(Lutz, et al., 1970). This represents steady state airborne transport from
several sources. Equations for meteorological transport of a pollutant were
developed for a) continuous point source, b) finite crosswind line source,
c) finite downwind line source, and d) finite aerial source. The validity of
the use of models for lead distribution and transport is discussed in the lead
case study. In addition, a model was developed at the workshop specifically
for lead, and it is also presented.
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3. Use of Models
More effort on developing and testing of models and submodel components
is required to fully utilize the value of this approach.
During this workshop, the submodel for atmospheric lead concentration
was developed but not tested. It provides a theoretical basis for development
of an atmospheric monitoring system for a pollutant. In the lead test case,
many quantitative data were compiled relating to the sources, critical
receptors, and pathways and portals of entry. However, it was not possible
to apply the data to any of the models to test them. A complete set of hier-
archical models for the special receptor and the special pathways is needed,
which would contribute greatly to development of an integrated monitoring
system for lead.
E. Basic Research Requirements
Basic research, as used here, is the scientific study of a specific
problem to obtain knowledge to understand the function, action, or part played
by a component of a system. Basic research may be closely related to research
monitoring because it may involve repetitive measurement over a short period
of time.
Basic research, for example, might be carried out on the pica behavior
(the craving for and eating of unnatural substances) of a child to determine
the amount of house or street lead-containing dust the child consumes or
breathes. This may be conducted jointly with research monitoring on the
daily levels of lead in dust in the houses and on the streets involved in the
research program. Both programs are limited in space and time until specific
questions have been answered.
F. Research Monitoring Requirements
Research monitoring is the repetitive sampling of a pollutant, or of
the effects it produces, to answer specific questions in a research or monitor-
ing program. Research monitoring is usually limited in both time and space,
in contrast with routine monitoring of the ambient environment which uses
large numbers of sampling stations in a monitoring network.
Research monitoring may be established to answer specific questions on
determining the importance of a specific transport pathway or concentration
area or, for example, determining the proper height of a sampler to quantify
the impact of air particles on the child.
G. Design of Integrated Monitoring System or Network
After identification of the critical receptors, pathways, sources, and
critical sources, and after compiling and evaluating all available information
(preferably with the use of models), the principles of monitoring systems
design may be applied in order to design an integrated monitoring system or
network. Various basic research and research monitoring needs would have to
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be identified and satisfied before a fully effective and efficient system
could be implemented. By following this procedure, one could feel reason-
ably certain that the monitoring system would yield the data for which it was
designed, and that such data would be sufficient for effectively controlling
critical sources.
III. EVALUATION OF CONCEPT USING LEAD AS A TEST CASE
To evaluate the concept of an integrated monitoring system, the available
data on lead were compiled following the outline presented in Section II.
Mathematical models for lead were examined. The applicability of the concept
to the specific test case was reviewed.
Lead is a heavy metal which is highly toxic to human beings when absorbed.
It is the only heavy metal that does not have some modern therapeutic appli-
cation and is not essential to the nutrition of human beings, other animals,
or plants. The modern interest in the physiological properties of lead
centers around its toxicological properties.
Lead is extremely useful and is used in very large quantities. In 1968
the United States used 1.39 million tons of newly produced lead plus 0.55
million tons from secondary sources. (Lutz, et al., 1970)
CBT.TICAL RECEPTOR POPULATION
Large numbers of people are exposed to lead, but it must enter the body
and be absorbed to be dangerous. People who work with lead in mines, smelters,
factories, and processing plants are occupationally exposed and may exhibit
toxic symptoms. In addition, workers with tetraethyl lead gasoline additive,
storage battery workers, ship scrapers, painters, consumers of lead-contami-
nated "moonshine" whiskey, and other exposed persons such as tunnel workers
and garage men, sometimes suffer from lead poisoning. Since there are now
quite strict environmental health controls on lead exposure in industry, the
number of cases of lead poisoning is not as great as previously. However,
children are also known to be subject to lead poisoning, apparently without
any more exposure than urban adults.
During the past few years, environmental lead has been the subject of
many publications and reviews. Based on these studies, the population at
risk, i.e., the critical receptor, in the United States has been identified
as the urban child of one to six years of age (Buckley, et al., 1973).
However, neurological damage may have actually occurred at an earlier period
with the effects first appearing at a later stage of development. In addition,
these effects may be too subtle to be easily recognized since they may
gradually progress with growth and maturation.
Clinical evidence indicates that young children are much more likely to
suffer from the effects of lead poisoning than adults. Also, children tend
to become exposed to and absorb greater quantities of lead than do adults,
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especially in the inner cities and older urban areas. This is probably due
to lead-contaminated dust predominantly originating from automobile exhaust
(Sayre, et al., in press) and from lead-contaminated household items such as
paint chips. Further, there is evidence indicating toxic symptoms appear at
lower dosage levels and that absorption rates are higher in children than in
adults (Alexander, et al., 1973.)
There are about 17 million children, aged six or less in the United States.
The National Bureau of Standards (Gilsinn, 1972) has estimated that 2.5 million
of these children have high risk of lead poisoning and that over 600,000 of
these children now have elevated lead levels in the blood (over 40 ug/100 ml).
This study confirms that "pediatric lead poisoning is a major urban health
problem in this country. The effects of this, in terms of the number of
children suffering permanent brain damage or damage to other organs, is not
known. How many of the children who have only slightly elevated blood-lead
levels will later exhibit learning or social difficulties is not known."
Another estimate of children with high blood-lead levels is the "Lead
Model Case Study" by Lutz, et al., (1970) which states that one-eighth of
the United States population lives in substandard housing in metropolitan,
ghetto areas. There are 10 million children in age groups 0.5 to 3.5 years,
with 1.25 million children living in high risk areas. It was estimated that
250,000 young children (up to 3.5 years) have high blood-lead levels, and
1,900 children suffer permanent brain damage, each with an approximate $250,000
cost to society during their lifetimes.
At any rate, young children constitute, by far, the largest group of
clinical lead poisoning cases—especially in high density urban areas and
near heavily traveled streets and highways. This may be largely due to their
much greater propensity to touch, mouth, and(lnjest just about everything
available in their environment.
While the acute effects of lead uptake are a matter of routine clinical
observation and treatment, the precise effects of chronic exposures to lead
at various exposure levels, rates, and modes are unknown. This is true for
all age groups. A comprehensive research monitoring program should also take
this into account.
Studies available on infants and children concerning the respiratory dose
and pulmonary retention of lead are not comparable to those performed with
adults. Knelson (1974) and King (1971) have reviewed information which
pertains to this problem. The current state of knowledge permits only an
indirect estimate of the inhalation of airborne lead. This can be done by
using the data based on metabolic requirements for oxygen, and hence for air.
Using basal metabolic requirements, the daily volume of air can be estimated.
To this should be added an allowance for increased metabolic requirements due
to infection, fever, and physical activity. For normal activity and growth,
the basal values should be multiplied by a factor of 1.35, and, in the extreme
case, by a factor of 2.0. Metabolic activity and requirements for infants and
children can be compared with adults on a surface area basis.
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No statement can be made at present about such factors as particle
size and its relation to the assimilation of lead by the respiratory route.
It is important, however, to know the particle size distribution of lead,
particularly the distribution below the two-micrometer level at from 1 to
3 feet above the surface. Measurements at this level are important in
estimating respiratory exposures and doses in infants and young children.
Although it is generally considered that there are no significant concen-
trations of organic lead compounds in the vapor form, some attention should
be given to this if pilot studies show that there is a significant concentra-
tion. In this case, the different absorption factors for vaporized lead
would have to be calculated.
Studies of the alimentary intake of lead in adults generally estimate
the retention by this route to be up to about 10%.
For estimating alimentary intake in healthy children, the balance studies
of Alexander, et al., (1973) are available; however, this study is limited to
a short-term study in 11 subjects from 3 months to 8-1/2 years of age. These
authors calculate an average daily intake of 10.6±4.0 yg Pb/kg body weight per
day. Calculations were made for adults and children based on all of the data
compiled during the workshop (Alexander, et al., 1973; Karhausen, 1973;
National Academy of Sciences, 1972; Knelson, 1974). This more recent calcula-
tion indicates a daily absorbed intake of 7.5 yg/kg per day for children of
10 kg weight. (See Figure 1 for comparison with adult.)
Retention of lead in the body is partly dependent on the levels already
existing. In small children the calculated retention was 2.03±1.4 yg Pb/kg/day
or an average of 18% of the daily intake (Alexander, et al., 1973). These
data, while preliminary, indicate that children take in less lead from air,
water, and food than adults, and they absorb more in the intestine. Taking
into account body weight, the resulting body burden of lead calculated for
the child (Figure 1) is about ten times more per kilogram of body weight than
for adults. This calculation does not include the additional exposure to
lead children are subjected to from such sources as street and house dust
which may be critical sources in some populations of children. It should be
noted that the numerous studies showing that the concentration of lead in the
blood of children is essentially the same as the concentration in adults does
not constitute a rebuttal or counter-example to the above calculations. If ~
a child rapidly stores lead in his soft tissues and bone, the blood-lead
level will remain low even though he is absorbing large amounts and the
tissue levels of lead are reaching toxic concentrations.
The whole blood-lead concentration is the most useful and accessible
index of the level of lead in the exchangeable and potentially toxic pool
within the body. Although individual measurements of whole blood-lead con-
centrations are not specifically related to adverse health effects, several
ranges in blood-lead concentration can be related to varying degrees of risk
of adverse health effects. The following broad ranges are recognized in
adults, based on all available literature cited in the bibliography. The
ranges for children are less well established, but seem to be similar except
that they are somewhat displaced downward, i.e., the thresholds for the
8
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XWWnMXf&WKWymfy
<-',? />- " t
\ -•" •••=' ,*
0.7Hg Pb/kg
dose per day
ONE YEAR OLD
MAY HAVE
TEN TIMES GREATER
BODY BURDEN
THAN ADULT!
ADULT (70kg)
7.5Mg Pb/kg
dose per day
CALCULATED ABSORPTION
CHILD (10kg)
Daily Intake
Lead Absorbed
Food - 300 yg 30 yg (10%)
Water - 20 ug . 2 yg (10%)
Air - 2.5 yg (23 m^) 21 yg (37%)
TOTAL
53 ygPb
70 kg man
±53 ygPb
0.7 ygPb/kg dose
per day to man
Daily Intake
Food - 130 yg
Water- 10 yg
Air - 2.5 yg (6 m3)
TOTAL
75 ygPb
Lead Absorbed
65 yg (50%)
5 yg (50%)
5.5 yg (37%)
±75.5 ygPb
10 kg child
7.5 ygPb/kg dose
per day to child
Figure L Calculated Lead Body Burden Comparison Between Adult and Child
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effects discussed below are somewhat lower in children. There are insufficient
data available at this time to establish ranges for infants (less than 12
months of age).
The major evidence concerning ranges was derived from the interpretation
of metabolic studies and Ca-EDTA mobilization data (National Academy of
Sciences, 1972; Lutz, et al., 1970).
Range 1 (10-40 yg Pb/100 ml)
Studies in groups of normal healthy persons, primarily adults, show mean
blood-lead concentrations between 15-20±6 (1 s.d.) yg Pb/100 ml of whole blood.
While in vitro assays of delta-aminolevulinic acid dehydratase (ALAD) activity
show partial inhibition in such groups, there is no measureable effect on the
level of the substrate, namely urine delta-aminolevulinic acid (ALA), in body
fluids.
Range 2 (30-55 ye Pb/100 ml)
This is the apparent threshold zone for the first detectable increase
in ALA excretion and free erythrocyte protoporphyrin (FEP) levels. Above this
threshold zone, there is a linear relationship between increases in blood-lead
concentrations and the logarithm of increases in the levels of heme precursors
in the body fluid. Early metabolic warning signals, of metabolic disturbance,
such as heme synthesis and proximal renal tubular function, are available.
However, there are at present no known biochemical indices of disturbance
in brain function.
Range 3 (50-80 yg Pb/100 ml)
If blood-lead levels in this range are sustained for periods of weeks or
months, most individuals will show adverse metabolic effects on heme synthesis,
and a few may show early mild symptoms or plumbism.
Range 4 (70-100 yg Pb/100 ml)
Sustained levels in this range are associated with increasing risks of
serious clinical effects, both acute and chronic. In comparison with groups
having blood-lead concentrations in the 10-30 yg Pb/100 ml range, the sustained
body burden must be increased by a factor of approximately 10 in order to reach
the 70-100 yg Pb/100 ml range.
An important finding is that while there is a relatively narrow but more
or less comfortable range between present levels of lead in the average adult
(25 yg/100 ml of blood) and the toxic level (70-80 yg/100 ml of blood), no such
range exists for children (Gilsinn, 1972).
The urban population of children has an average level of lead in the
blood of about 25 yg/100 ml of blood, but 28.9% are 40 or above, 12.7% are 50
or above , 6% are 60 or above, and 2.7% are 70 or above. This includes over
600,000 children with levels over 40 yg/100 ml (700,000 based on New York data)
(Gilsinn, 1972).
10
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Symptoms such as anemia, behavorial problems and physiological changes
have been observed at 40 yg/100 ml and over of lead in the blood of children.
It is known that the threshold of lead toxicity in young children is lower
than that of adults; however, how much below 40 or above 40 yg is not known.
The disconcerting facts are that many blood levels of children are high and
we know that the toxicity levels are in this range, but we do not know exact
threshold levels or the variation in sensitivity which could result in many
children having toxic problems at low levels. Therefore, the range between
present levels and toxic levels in children is uncomfortably close with no
latitude for safety (Lin-Fu, 1973).
Some evidence indicates that young children have a lower tolerance to
blood-lead concentrations than do older population groups (LinrFu, 1973).
In considering receptor levels of the monitored pollutant (lead), the
vulnerability of developing brain tissue requires particular attention. Un-
like other tissues which have an inherent ability to regenerate themselves,
brain tissue is unique in its "once only opportunity to grow properly."
Information heightening this critical concern is that the concentration of lead
in the brain sharply increases only during the first two decades of life
(Zaworski and Oyasu, 1973). Maximum rates of growth occur in the human prior
to one year of age, are largely complete by 30 months of age, and appear to be
greatest between the last eight weeks in utero and the first 10 months follow-
ing birth. There may be another possible period of brain vulnerability - the
10th to the 18th gestational week of neuronal multiplication. This emphasizes
the need to consider the pregnant woman in a pollutant monitoring model. This
period of increased susceptibility may be associated with a lower tolerance
for lead than is apparent in older age groups.
Autopsy data and metabolic studies (Rabinowitz and Wetherill, 1973) show
that lead in the body is partitioned into two major compartments: (1) a
small but rapidly exchangeable compartment consisting of blood, soft tissues,
and the rapidly exchangeable fraction of bone mineral; and (2) a much larger
but slowly exchangeable fraction tightly bound in bone and teeth. Autopsy
data show that the bony fraction increases with age in members of industriali-
zed and urbanized societies, but that soft-tissue lead concentrations show
little apparent increase with age. A three-city study (U.S. Public Health
Service, 1965) indicated that blood-lead concentrations do not show any
measurable increase with age. The rapidly exchangeable pool is similar to, if
not identical with, the chelatable fraction (or the metabolically active
fraction of lead in the body. There are no documented clinical instances in
recent years of toxicity related to the sudden mobilization of the bony stores.
Experimental observations are not helpful in this regard as they do not closely
simulate the normal human experience. Increasing concentrations of lead in
the exchangeable pool are associated with the known adverse health effects of
lead (Chisolm, 1971).
Experimental observations and clinical observations suggest that free
erythrocyte protoporphyrin (FEP) measurements reflect sustained changes in
soft-tissue lead levels.
11
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Biological variables such as nutritional, genetic, metabolic, and hormonal
factors (about which there is little information, but which could modify the
absorption and distribution of lead) do not allow a more precise statement
regarding blood-lead concentrations in various groups of people.
Blood-lead concentrations can be affected in the short-term by isolated
spikes in assimilation due to factors like the ingestion of lead-containing
paint chips or dusts. This can cause a transitory increase in the blood-lead
concentration. Conversely, chelation therapy can temporarily depress the
blood-lead concentration. However, the single, massive ingestion of lead is
not associated with known severe toxicity (U.S. Public Health Service, 1971).
It is essential to measure lead directly in the receptor to determine the
uptake resulting from environmental exposure sources. The available data
(National Academy of Sciences, 1972) strongly suggest that measurements of the
concentrations of lead in whole blood and the metabolite, erythrocyte proto-
porphyrin, are among the most sensitive indicators of changes of lead con-
centrations in the exchangeable pool which is responsible for lead's adverse
effects. Among the various practical options for sampling, this is also the
most available one. Random blood samples collected from children in selected
environmental areas might give a fairly reliable indication of average
exposure/effect relationships in these areas if the random samples are numer-
ous enough to be representative, whereby unusual variances would cancel each
other.
The methodology used for sampling and analyzing blood for lead is critical.
Reliable results depend on stringent quality control procedures. Under good
conditions, sampling and analysis errors on the order of ±5 yg Pb/100 ml
(1.0 s.d.) should be anticipated in field studies.
While the blood-lead level is one measure of assimilation by the receptor,
other types of data should not be disregarded in a monitoring system.
Teeth represent a host tissue in which the dentine is reflective of prior
exposure over a non-specified length of time. It may be possible to utilize
the lead-210 content of this tissue in order to determine the residence time
of lead in the tissue. Levels in teeth do correlate with exposure but not to
blood lead, and they normally decrease markedly at about age 10 in the human.
While dentine-lead levels have been shown to correlate to exposure levels
(Needlemann, et al., 1973), the information concerning any possible relation-
ship to adverse health effects is insufficient at this time. In one study
(Needlemann, et al., 1974), which included both analysis of teeth and blood-
lead concentrations, a relationship between late health effects was found to
be"correlated with prior blood-lead concentrations, but not with tooth dentine
levels.
Hair may afford a method of evaluating community exposures and changes
therein, particularly exposures to airborne pollutants. The ready availability
of this tissue would initially suggest that it is an ideal tissue for receptor
monitoring. However, variations in hair growth rate, area of the body from
12
-------
which obtained, hair color, racial background, and texture must be considered
(Schroeder and Nason, 1969). Present methodologic difficulties are a strong
deterrent to effective usage of hair as a primary receptor monitoring tool.
A pilot study to assess possible relationships between hair-lead levels,
blood-lead levels, and adverse health effects may yield meaningful data and
facilitate the interpretation of hair-lead levels.
Fingernails or toenails are also readily accessible and should be con-
sidered in the design of a monitoring system. However, those measurements
are subject to the same concerns that apply to hair.
As an available metabolic product, sweat should be considered for measure-
ment in a biologic monitoring system. However, data for lead evaluated in
several normal, white, male adults shows that the concentration of lead in
activity-induced sweating is approximately 15 parts per billion, or
15 yg Pb/liter (Rabinowitz, 1974), and may vary depending upon the degree of
active sweating; i.e., hypermetabolic versus passive or basal sweating level.
Sweat may not be useful for monitoring purposes because of the low lead con-
centrations, the difficulty of obtaining sufficient uncontaminated samples,
and the lack of quality control in accepted analytical methodology.
Saliva, like sweat, is a substance which one might include in a monitor-
ing system. This material contains approximately 20 parts per billion of
lead, or 20 yg Pb/liter, in healthy, white, male adults and apparently is in
rapid exchange with blood lead (Rabinowitz, 1974). Significant deterrents to
its usage in a large-scale monitoring approach are the difficulties inherent
in obtaining adequate samples which are free of contamination by inhaled or
ingested lead. These difficulties would be especially marked in young
children.
A well-rounded biological lead monitoring research approach would probably
include at least three basic analyses of blood samples collected with random
or selective sampling techniques. These three analyses are:
(a) Whole Blood-Lead Concentration. This analysis gives a reliable
indication of the amount of lead available in the exchangeable body pool,
and allows some evaluation of its relation to general, and possibly specific,
environmental lead exposure conditions.
(b) Free Erythrocyte Protoporphyrin (FEP). This is a sensitive method
for measuring metabolic tissue effects from increased lead absorption levels,
and may indicate the degree of possible permanent damage to the body.
(c) Hematocrit. This is a simple way to determine the possible relation-
ship between iron deficiency and increased lead absorption.
Information of this type is already being obtained through childhood lead
poisoning screening programs, and data are being tabulated by the Communicable
Disease Center, Bureau of State Services, Division of Environmental Health
Services, Atlanta, Georgia. Semi-micro techniques for both blood lead and
erythrocyte protoporphyrin have recently been developed. Such sampling might
13
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be rather easily extended to infants and pre-natal programs. For the
sampling of children within this age range not covered under Medicare, it
may be advisable to approach the American Academy of Pediatrics (Evanston,
Illinois). With suitable administrative arrangements, such data could be
made available to an integrated monitoring system.
Epidemiologic data and experimental observations suggest that women in
the childbearing age range (especially during pregnancy), neonates, infants,
and young children should be monitored. Sampling could possibly be made
available to other groups through health maintenance organizations, similar
pre-paid medical group plans, the armed forces, etc. If accessible, these
groups should also be included.
Exploration of the utility of hair and shed deciduous teeth on a pilot
basis should be considered. However, one should take into account the fact
that such samples are not easy to collect and present considerable problems
in both analysis and interpretation. The aim of such a pilot study should be
to determine correlations between teeth and hair and nails, on the one hand,
and blood-lead levels and indices of toxicity on the other hand.
If autopsy tissues can be obtained, they would be invaluable to increase
what is currently a very limited data base with regard to tissue-lead levels
in fetuses, infants, and children.
There is a great need for more information on lead metabolism in fetuses,
infants, and young children. Not only with regard to dietary intake, but
also concerning respiratory intake, and basic respiratory physiology in young
children themselves. For this purpose, the feasibility of using the naturally
occurring isotopes such as lead-210 or lead-204 as a marker deserves serious
consideration. When such research is completed, the results will be useful
in updating monitoring systems that are currently being proposed.
Adequate provisions for the protection of an individual's confidentiality
must be considered in the design of programs involving human monitoring.
The most critical adverse effect of lead toxicity is irreparable damage
to the brain and nerves. Although it has not been established that the brain
is most vulnerable to lead during its growth and neuronal multiplication
phases, this may be the case. If, indeed, the brain is most susceptible to
lead during these phases, the situation may be associated with a lower toler-
ance for lead in children than is apparent in older age groups. Much more
information is needed in this area.
Whole blood-lead concentration is the most useful and accessible index
of the exchangeable and potentially toxic pool within the body. Although
individual measurements of whole blood-lead concentrations are not specifically
related to adverse health effects, several concentration ranges can be related
to varying degrees of risk of adverse health effects. The threshold zone,
derived from the interpretation of metabolic studies in adults and calcium-
ethylenediaminetetraacetic acid (Ca-EDTA) mobilization data, appears to range
between 30 and 55 vg Pb/100 ml of whole blood. The duration of exposure and
14
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lead concentration levels in whole blood are related to the appearance of
effects and to accurate dose calculation. Biological variables such as
nutritional, genetic, metabolic, and hormonal factors probably modify the
absorption and distribution of lead; however, little information is available
in these areas.
While whole blood-lead concentration is the most accessible and valuable
biological monitoring index, other media should not be disregarded in a com-
prehensive monitoring program. Teeth, for instance, may represent a host
tissue which is reflective of prior doses over a non-specified length of
time. Also, hair may afford a method of evaluating community exposure trends.
The information obtainable from random samples of excreta and bodily secre-
tions is deemed of negligible value for monitoring purposes.
CRITICAL TRANSPORT PATHWAYS AND PORTALS OF ENTRY
Once sound integrated monitoring system concepts are developed and
applied to surveillance of environmental lead, as well as other pollutants, it
will be possible to further delineate areas of concern, to provide reliable
trend and research data, and to establish efficacious and economical control
measures.
Dispersion of lead into the environment is relatively broad and diffuse.
However, dispersal from the critical source to the critical receptor involves
specific pathways which must be quantified and accurately monitored. To this
must be added the general background level of lead.
The detailed exposure pathways contributing to lead burdens in a receptor
are shown in Figures 2 and 3. An objective of this study was to quantitate
these pathways and, thus, to determine total exposure and its variability
among individuals and populations. Additionally, the relations between
exposure, dose, uptake, and effects were assessed. The diagram in Figure 4
illustrates the pathways of lead within a critical receptor. These pathways
were assessed to determine the best indices of body lead burdens.
In spite of the availability of an impressive information base
(Lutz, et al., 1970), the pathways leading to and within a critical receptor,
the urban child, cannot be accurately quantitated without additional sub-
stantial investments in research and monitoring. One result of this lack of
quantification is that most current review documents tend to overestimate the
contributions of leaded paint chips and to underestimate the importance of
airborne lead which continually settles out on all surfaces and is available
for resuspension and subsequent inhalation and ingestion.
The major sources of airborne respirable dust particles containing lead
are transportation, industry, energy production, and incineration. The
particle size distribution, after gravitational and atmospheric interaction,
is believed to be approximately a logarithmic normal distribution for all
sources. Of these sources, motor vehicles using leaded gasolines contribute
by far the greatest quantities of all airborne lead particles (Buckley,
et al., 1973).
15
-------
A
l'
FOOD
WATER
MOTHER
DUST
SUSPENDED
PARTICLES
L
k
f
\
T
INGESTION
INTERMITTENT &
VARIABLE ABSORPTION
^
f
FOOD
PAINT
•^
WATER
DUST
r
PLACENTAL TRANSFER URBAN
CHILD
INITIAL BURDEN
INHALATION
CONTINUOUS &
VARIABLE ABSORPTION
r
(CRIT
DU
SUSPE
PAR]
k.
f
ICAL
PTOR)
ST
NDED
•ICLES
Figure 2. Major Pathways Affecting Lead Burden in Critical Receptor
-------
OTHER SOURCES
PAINT, INK, ETC.
Pb &
Pb COMPOUNDS
MAJOR
ROUTES
MINOR
ROUTES
HIGHLY
VARIABLE
ROUTES
AUTO
EXHAUST
AIR
-»>
"*""
DUST
T
WATER
WATER
PIPES
FORAGE
CROPS
CONSUMER
CROPS
FOOD
PROCESSING
ANIMALS
A
I
I
INGESTION
AND
INHALATION
BY
CRITICAL
RECEPTOR
Figure 3. Lead Exposure Pathways to Critical Receptor
-------
03
• RATES
VARIABLE,
DEPENDING
ON MANY
FACTORS
INHALATION
UPPER
RESPIRATORY
SYSTEM
LOWER
RESPIRATORY
SYSTEM
Gl TRACT
1
INGESTION
B
L
O
O
D
SOFT
TISSUE
BONE
HAIR
NAILS
NERVES
BRAIN
URINE
SWEAT
FECES
Figure 4. Pathways of Lead in Critical Receptor
-------
The airborne concentration of lead at any specified location can be
determined by summing the relative contributions from mobile and stationary
sources, the geophysical background and the atmospheric lead originating from
other cities. Meteorological conditions, proximity to significant stationary
sources, and the relation between traffic volume and distance from the
critical receptor population groups are important monitoring considerations.
The largest source of routine ambient air-lead data in the United States
is the National Air Surveillance Network (NASN). These stations, which are
located both in urban and non-urban places, provide a general indication of
overall "average" urban lead concentrations. In addition, many specialized
measurement studies have been undertaken very near important lead sources,
such as highways and intersections, and these are reported in the literature.
The arithmetic mean air-lead concentration in the United States (U.S.
Public Health Service, 1965) (from 1960 to 1965) was 0.79 yg/m3, using data.
from NASN high-volume samplers. During this period of time, the highest single
air-lead concentration in any city was 8.6 yg/m3.
Many investigators, such as Larsen (1969), hold that the concentration
in air of pollutants in general follows a lognormal distribution. (It should
be noted that the arithmetic mean is not an appropriate statistical measure
of central tendency for the lognormal distribution; the geometric mean should
be used).
Table 1 gives typical annual mean air-lead concentrations from several
cities. Typical outlying concentrations are on the order of 1 yg/m3; con-
centrations in the more central areas are generally in the range of 2 to 4
yg/m3- The table also shows examples of the higher air-lead concentrations
that are encountered very close to sources. Concentrations measured near
traffic and on sidewalks range between 8 and 30 yg/m3, with some values as
high as 54 yg/m3 for the morning rush hours. (National Acadamey of Sciences
1972).
Table 1. ATMOSPHERIC LEAD CONCENTRATIONS
Of Cities Annual Mean
Philadelphia, suburbs 1 yg/m3
Philadelphia, downtown 3 yg/m3
Cincinnati, suburbs 1 yg/m3
Cincinnati, downtown 2 yg/m3
Los Angeles, suburbs 2 yg/m3
Los Angeles, downtown 3 yg/m3
Near Roadways Range of Annual Means
Los Angeles, freeway (a.m. rush hour) 26.9-54.3 yg/m3
Los Angeles, freeway (mid-day) 16.6-31.1 yg/m3
Los Angeles, downtown traffic (a.m. rush hour) 19.1-29.9 yg/m3
Los Angeles, downtown traffic (mid-day) 8*4-12*2 ue/m3
Pasadena, downtown, sidewalk (mid-day) 8!6-14!6 yg/m3
19
-------
It should be noted that all the data are not strictly comparable
because the sample durations (i.e., averaging times) are often different, or
worse, are not stated at all. Furthermore, the exact distance and height
at which the measurements are made are often unspecified. However, some
data do exist in the literature on concentration "profiles" as a function
of distance from sources. Elaboration on this subject is beyond the scope
of this review; however, consideration of these factors is essential in the
design of monitoring networks.
It can be concluded from the NASN data previously cited that ambient
air urban-background lead concentrations are in the range of 1 to 3 yg/m3
in the majority of urban areas (annual average), with concentrations within
100 meters of streets with heavy traffic loads usually ranging from 8 yg/m3
to about 30 yg/m3.
Fairly extensive data are available on the size distribution of atmos-
pheric lead-containing particulates (Robinson and Ludwig, 1964). The dis-
tribution is generally approximated as log-normal; i.e., the logarithm of
aerodynamic particle size is normally distributed. A typical cumulative
plot of particle size on log-probability paper is shown in Figure 5. Note
that over 90% of the mass of airborne lead particles are under one micro-
meter in size. Lead particles of this size distribution can readily be
respired and thereby entered into the bloodstream.
Similar data on the size distribution of the larger diameter particles
which settle out of the atmosphere are unavailable. These particles con-
tribute to the lead burden of the dust encountered by children and vary
widely in size due to the effects of control systems on sources such as
smelters, refining and metallurgical processes, and on the internal com-
bustion engine and its exhaust system. However, since particulates of very
large diameter (greater than 25 microns) and intermediate diameter (10-25
micrometers) can be inspired and/or ingested by the critical receptor, they
are of high concern.
Settled dust originates from the same sources as airborne respirable
dust particles - namely, transportation, industry, energy production, and
incineration. Here again the leaded gasoline used in motor vehicles con-
tributes most of the lead in dust in most residential areas. However, there
are important exceptions. For example, the El Paso, Texas, lead smelter
emissions dwarf the contributions of lead dusts by automobiles and lead-based
paints in some El Paso residential areas (Landrigan, et al., 1974).
Lead in settled dust and dirt also contributes to increased blood-lead
levels through the inhalation of resuspended dust and through ingestion
primarily by children. Although exposure to dirt and dust contaminated with
lead from automobile exhaust, alone, has not been shown to be responsible for
cases of overt lead poisoning, it has been related to high blood-lead
levels in children (Buckley, et al., 1973). There is also a good correla-
tion between high blood-lead levels in children and household dust. The
lead in dirt and dust on children's hands, and the consequent higher blood-
lead levels also increase with nearness to heavily traveled streets and mid-
20
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CONTINENTAL
AEROSOL (JUNGE)
0.2 —
0.1
5 10 15 20 30 40 50 60 70 80 85 90 95
MASS SMALLER THAN GIVEN DIAMETER (PERCENT)
Figure 5. Average lead size distribution comparison, with Junge's
model for continental aerosols on log-probability paper.
(Tabular information adapted from Robinson and Ludwig, 1964. )
21
-------
city areas, while adults in the same environment show substantially lower
blood-lead concentrations than do children.
Recent surveys of several urban environments show that there are sub-
stantial concentrations of lead in the dust and dirt on and near heavily
traveled roadways (see Table 2) and in residential areas (see Table 3).
The fallout of airborne lead from automobile exhaust and that from other
mobile and stationary sources creates a significant exposure hazard, espe-
cially for children. Dust and chips from the deterioration of leaded paints
are also major contributors to interior and exterior residential lead pollu-
tion.
Table 2.
Location
Washington, D.C.
Chicago
Philadelphia
Brooklyn
Boston
Vermont
New York City
Detroit
Philadelphia
Various U.S.
cities
LEAD DUST ON AND NEAR HEAVILY TRAVELED ROADWAYS
Sampling Site
Busy Intersection
Many Sites
Near Expressway
Near Expressway
Near Expressway
Near Expressway
Near Expressway
Near Expressway
Street Dust
Gutter (Low
Exposure)
Gutter (High
Exposure)
Highways and
Tunnels
yg Pb/g
12,820
(4,000-8,000)
6,000
3,000-8,000
1,000-2,500
500-700
2,000
966-1,213
1,507
(270-2,626)
3,262
(280-8,201)
10,000-20,000
Authority
Lin-Fu (1973)
Calandra (1973)
Needleman, et al.,
(1973)
900-4*900 Lombardo (1973)
Fritch and
Prival, (1972)
Pinkerton, et al.,
(1973)
Ter Haar, et al.,
(1973)
Needleman, et al.,
(1973)
Buckley, et al.,
(1973)
Netherlands
Heavily Traveled 5,000
Roads
Rameau (1973)
Sayre, et al., (in press) considered house and hand dust as a potential
source of lead exposure to young children. Their findings showed a strong
relationship between lead concentrations found on household surfaces and
those found on children's hands in the same households. No significant
correlation could be made between the household dust-lead level and whether
or not leaded paint was available in the household. In addition, they found
that inner-city children have higher mean blood-lead values than suburban
children, and the lead content of dusts collected from the houses and hands
of inner city children is significantly higher.
22
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Location
Philadelphia
Table 3. LEAD DUST IN RESIDENTIAL AREAS
Sampling Site yg Pb/g
Boston and
New York
Brattleboro, Vt.
Birmingham, Eng.
New York City
El Paso Smelter
Philadelphia
Classroom
Playground
Window Frames
House Dust
In Home
In Home
Middle Class
Residential
Smeltertown
Dust at:
0-1 Miles
1-2 Miles
2-3 Miles
>4 Miles
Urban Industrial
Residential
Suburban
2,000
3,000
1,750
1,000-2,000
500-900
5,000
608-742
36,853
(2,800-103,750)
2,726
(100-84,000)
2,234
(100-29,386)
2,151
(200-22,700)
3,855
(929-15,680)
614
(293-030)
830
(277-1,517)
Authority
Needleman, et al.,
(1973)
Needleman &
Scanlon (1973)
Darrow &
Schroeder (1973)
Lombardo (1973)
Pinkerton, et al.,
(1973)
Landrigan, et al.,
(1974)
Needleman, et al.,
(1974)
Lead pollution at the soil surface level varies markedly, but it
generally decreases with distance from central urban areas, roadways, smelters,
power plants, painted buildings, and other sources of lead. The results of
some recent studies documenting lead surface soil pollution are presented
in Table 4.
Household paints containing more than 1% lead are very important con-
tributors to clinical lead poisoning and elevated blood-lead levels in
children. This is especially true for older deteriorating houses where the
paint is chalking, flaking, and/or peeling, and young children between the
ages of 6 months to" 3 years are present. The pica habit of these young
children, i.e., eating non-food items, accounts for the high ingestion rate
of leaded-paint particles and the consequent doses.
23
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Location
El Paso smelter
area
Table 4. LEAD AT SOIL SURFACES
Locality yg Pb/g Authority
600 feet from 3,457
smelter
Landrigan, et al.,
(1974)
Midwest city
survey
San Diego
San Francisco
Los Angeles
Residential
Commercial
Industrial
City Park
City Park
City Park
1,636
2,413
1,512
194
560
3,357
Hardy (1971)
National Academy
of Sciences
(1972)
Adjacent to U.S. Soil
highways
160-540
Seeley, et al.,
(1972)
England
Soil
10,000
Barltrop & Strahlow
(1973)
High Sierra
mountains
Soil
9.2
Hirao & Patterson
(1974)
Although the ingestion of lead based paint chips by young children is
often the ostensible and/or actual cause of overt clinical lead poisoning,
these paint chips may have served only as a trigger for the acute symptoms
requiring immediate treatment. These clinical cases may not have occurred
in the absence of pre-existing chronic high blood-lead concentrations
originating from airborne and/or settled dusts. Paint chips are available
to young children especially in older, deteriorating houses that are
improperly maintained.
Despite the existence of a Health Code limiting the level of lead in
household paint for over a decade, Finberg and Rosen (1973) showed that
significant lead can be found in vinyl acrylic paints. Many of these paints
contained from 4 to 6 micrograms of lead per gram of paint despite the fact
that they were labelled for interior use.
Lead has been found in the majority of food items tested throughout the
world. Several investigations were made to determine the lead content of
typical diets for groups of adults and children. These diets were considered
to be representative of the intake of the groups studied. An excellent,
though unexpected, agreement was observed among the various groups' average
reported values in spite of their culinary differences. Some of the typical
24
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average daily intakes of lead which appeared in the literature are shown in
Tables 5, 6, and 7.
Table 5. LEAD IN DIET OF ADULT MALES
Adults
United Kingdom
England
England (1,500
Japan
United States
United States
United States
United States
United States
United States
United States
United States
United States
United States
World Average
Average pg Pb/day*
274
220
g) 200
150
300
300
330
330
270
100-500
300
285
300
258
440
Authority
Thompson (1971)
Mbnler-Williams (1950)
Tolan & Elton (1973)
Imamura (1967)
Kehoe (1961)
Kehoe (1963)
Patterson (1965)
Schroeder & Balassa
(1961)
Parry-Howells (1971)
Schroeder & Tipton
(1968)
Cholak & Bambach (1943)
Barley (1970)
Lewis (1966)
Schroeder & Balassa
(1961)
Karhausen (1973)
^Assumes 2,000 g of food per day (some British diets assume 1,500 g).
From a sampling of New York City diets in 1966 (Barley, 1970), an
interesting comparison can be made of the concentrations of lead in fresh
versus processed foods (Table 8). Note the large increases in lead con-
centrations when fruits and vegetables are processed and when flour is con-
verted into bakery products. These increases in lead content during pro-
cessing are the result of such factors as contributions of lead from the
food handling machinery and from containers.
25
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Table 6. DIET OF 15-20 YEAR OLD MALES
(Food and Drug Administration 1973 Unpublished Data)
Food Product
Dairy (milk-cheese-eggs)
Meat (fish-beef-poultry)
Grain and Cereal
Potatoes (fried-boiled-chips)
Leafy Vegetables
Legume Vegetables
Root Vegetables
Garden Fruits
(tomatoes and cucumbers)
Fruits
Oil-Fats-Shortening
Sugar-Adjuvants
Beverages (tea-coffee-soda)
TOTALS
gms/day
ingested
756
290
369
204
59
74
34
88
217
52
82
697
2,922
gms/day
ppm lead
in food
Trace
0.015
0.012
0.004
0.054
0.265
0.131
0.108
0.031
0.15
0.008
0.004
0.782
ppm Pb
Ug Pb per
day ingested
Trace
4.4
4.4
0.8
3.3
19.6
4.5
9.5
6.7
0.8
0.7
2.8
57.4
yg Pb/day
Table 7. LEAD IN DIET OF CHILDREN
Age
Young Adult
2 Year Old
Youth (10 kg)
Youth (20 kg)
Youth (25 kg)
Youth (30 kg)
Italian Infant:
4 Month Old
6 Month Old
9-12 Month Old
Infant
Infant
Infant
Ug Pb/day
165
133
120
155
180
210
172
224
289
100
150
165
Authority
Chisolm & Harrison (1956)
Barltrop (1973)
Alexander, et al. (1973)
Lanzola, et al. (1973)
ii ti ii
Kehoe, et al. (1933)
Barltrop & Killala (1967)
Chisolm & Harrison (1956)
26
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Table 8. LEAD IN FRESH AND PROCESSED FOODS
Adapted from table by Harley (1970)
and from table by Tolan and Elton (1973)
Diet Category
Vegetables
Fruit
Whole Grain Products
Flour
Macaroni
Rice
Bakery Products
Meat
Poultry
Eggs
Dairy Products
Shellfish
Fresh Fish
Carrots
Peas
Corn
Spinach
Beef
Cherries
Baby Foods
Fresh
mg/kg wet weight
0.12
0.07
0.42
0.30
0.22
0.31
0.16
0.02
0.02
0.01
0.02
0.23
0.05 (jars)
0.04 (jars)
Processed
mg/kg wet weight
0.44
0.25
0.13
0.04
0.08
0.04
0.39
0.04
0.22
0.21
1.22
0.95
1.20
0.17 (cans)
0.24 (cans)
An on-going program in the Food and Drug Administration (FDA) currently
measures lead levels in 41 major food commodities including fluid milk and
nine baby foods. In Fiscal Year 1975 the FDA will conduct two additional
total diet studies. One will focus on the lead content of foods consumed
by the 6-month-old infant and the other will be concerned with the same
problem in the two-year-old toddler. (The current FDA guideline for lead
in evaporated milk is 0.5 ppm).
The analytical procedure which has been used to date by FDA (FDA, 1973)
in obtaining lead data is based on atomic absorption. The FDA is readying
an anodic stripping voltametry (ASV) procedure which will probably be used
in future surveys involving heavy metals.
27
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The Children's Hospital in Washington, B.C. is currently surveying the
blood-lead levels of children in the inner city. In support of this survey,
the United States Food and Drug Administration Baltimore Laboratory is
analyzing the food sources of these children for lead.
The total diet survey conducted by the FDA indicates that the average
daily intake of lead by a 15 to 20 year old male is 57.4 yg/day. Certain
assumptions have been applied to the data used to calculate this value in
an effort to compensate for inadequacies in the reported values. If one
converts all values reported as "trace" to 0.09 yg Pb, on the assumption
that 0.1 yg Pb would be the lowest reported value, then the average daily
intake increases to 159 yg Pb/day. Furthermore, if all values reported as
"zero" are assumed to have the finite value 0.05 yg Pb, then the average
daily intake increases to 233 yg Pb/day. The conclusion based on the Fiscal
Year 1973 data is that the average daily intake of lead in the food by a 15
to 20 year old male is between 57 and 233 yg/day.*
In a similar study, the Food and Drug Protectorate of Canada concludes
that the lead intake from food is about 180 yg Pb per day for a young adult.
Although children ingest a lower total amount of lead, on a body weight
basis (assuming 70 kg for the average man and 10 kg for the average one-year-
old child), the amount absorbed for the child is greater, as discussed pre-
viously.
Drinking water, on the average, contributes very small amounts of lead
to the body burden. Very few people drink water containing more than 50 yg
Pb/liter. Problem areas would primarily involve lead plumbing and lead-
glazed drinking vessels, particularly with acidic drinks. For monitoring
purposes, water quality baselines should be established for potable water
supplies just prior to distribution, and trends in suspended and dissolved
lead should be evaluated. Pathways of lead to the critical receptor via
water and other liquids are shown in Figures 6 and 7.
The analysis of more than 1,500 samples of raw surface waters at more
than 100 locations across the United States from 1962 to 1967 indicated a
range of dissolved or colloidal lead concentrations (i.e., those passing
through a 0.45-ym millipore membrane filter) of between none detectable and
90 yg/liter. Only 23% of the samples yielded positive results. The arith-
metic average was on the order of 10 yg Pb/liter. The average of the
positive results was 23 yg Pb/liter (Kopp and Kroner, 1970). In the 1970
*This information was provided in a personal communication from Mr. Paul
Corneliusses of the FDA. The assumptions discussed above were impressed on
the data in an attempt to counteract the effect of dilution resulting from
the combination of several samples.
28
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| SEEPAGE
to
vo
GROUND
WATER
I RAINFALL |
CISTERN
WATER
TREATMENT
MISC. POINT &
NON-POINT
SOURCES
DISTRIBUTION
SYSTEM
PLUMBING
DRINKING
VESSEL
-4
IORAL
INTAKE
WASTE WATER
DISCHARGE
Figure 6. Pathways of Lead to a Receptor Via the Water Cycle
-------
LIQUIDS (MILK)
FEED
COW
MILK
PROCESSING
AMBIENT
AIR
ENCLOSURE
LIQUIDS (OTHER THAN WATER & MILK)
PACKAGING
CONTAINERS
STORAGE
VESSELS
DRINKING
VESSELS
ORAL
INTAKE
FOOD,
JUICES
CARBONATION
RAW
MATERIALS
PROCESSING
T
OTHER
ADDITIVES
Figure 7. Pathways of Lead to a Receptor Via Liquids Other Than Water
-------
United States Geological Survey analysis of 720 samples of raw surface
waters across the United States, lead in the dissolved or colloidal form
was found in 63% of them. The range in the positive samples was from 1 to
greater than 50 yg/liter. Lead occurred widely in the 6 to 50 yg/liter
range (USGS, 1970). In areas of limestone and galena, waters are known to
contain lead in solution as high as 400 to 8,000 yg/liter (Kopp and Kroner,
1970). This is highly unusual, however.
Of 23 rainfall samples collected, concentrations of particulate
material plus dissolved lead as high as 490 yg/liter were obtained. The
lead concentrations increased with nearness to highways and other sources
(Ettinger, 1965).
A range of none detected to 62 yg/liter of dissolved or colloidal Pb
(the average was less than 10 yg/liter) was found in a 1962 survey of the
100 largest water supplies in the United States (Durfor and Becker, 1964).
A range of none detected to 60 yg/liter of dissolved or colloidal lead was
found-in samples from 544 water supplies in the United States in 1973. The
majority of values were less than 10 yg/liter (Buckley, et al., 1973).
Water standing in lead pipes exhibited as much as 920 yg/liter lead
(Kehoe, 1961). No data are available on the lead contributed by water dis-
tribution systems other than that the interior of steel storage tanks is
often painted with lead chrornate paints.
Hardy (1965) reported that beer contains 100 yg/liter of lead and wine
from 80 to 860 yg/liter. These values are supported by data presented by
de Treville (1964) which show Cincinnati beer to range between 10 and 290
yg Pb/liter and wine between 50 and 1,510 yg Pb/liter. Some of the data
cited in de Treville's report are given in Table 9.
Processed milks in 1972 and 1973 were found to deliver up to 100 yg
Pb/day to toddlers. Fresh human milk and homogenized cow milk were found
to contain no detectable lead (less than 0.5 yg/100 ml). Table 10 contains
data on the concentration of lead in liquid milks (Lamm and Rosen, 1974).
Cases of lead poisoning in humans have resulted from use of acidic
drinks with lead-glazed utensils. One case resulted after a patient had two
years of habitual exposure to lead from drinking liquids with a pH of 2.7
from a glazed mug (Harris and Elsea, 1967). Tests were made of the lead
contribution from a glazed mug when filled with chilled cola, with pH 2.7,
for varying time periods. The cola before being poured in the mug had a
lead concentration of 200 yg/liter. After two minutes, about 3,000 yg/liter
of lead was leached from the mug; after two hours, the lead level was as
high as 6,800 yg/liter. It was found that the lead contribution by lead-
glazed drinking vessels varies greatly with: (1) the temperature at which
the glaze was fired; (2) the time period during which the drink remained in
the vessel; (3) the pH of the drink; and (4) the number of times the vessel
had been used previously. As an instance of the influence of pH, it was
found that no lead was detected in water that was retained in the same mugs
which had contributed large concentrations to cola with a pH of 2.7 (Harris
and Elsea, 1967).
31
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Table 9. LEAD CONTENT OF VARIOUS BEVERAGES, IN MILLIGRAMS PER LITER
(Information from de Treveille, 1964)
Tea
Tea (Ceylon), hand-picked (dry) 0.02
Tea leaves, import package lined
with corroded lead foil (dry) 43.2
Tea (India), packed in tins 1.8
Tea (India), packed in lead foil 2.4
Beer
Beer (Cincinnati) 0.01-0.29
Grape Juice and Wine
Grape Juice 0.04-0.06
Wine 0.05-1.51
Liquors and Spirits
Brandy (India) 0.05-0.06
Rum (India) 0.024-0.057
Dry Gin (India) 0
County spirit (India) 0.026
Whisky (India) 0.027
Aerated Waters
Lemonade 0.004
Soda 0.004
Table 10. LEAD IN NEW YORK AREA MILK
(Information from Lamm and Rosen, 1974)
Samples Mean ± 1 s.d. Range
Type of Milk Sources Analyzed (yg Pb/100 ml) (ug Pb/100 ml)
Evaporated
(Skimmed) 2 Brands 11 6.0 ± 0.2 4-7
Evaporated
(Whole) 2 Brands 15 11.0 ± 1.1 4-22
Infant formula:
Concentrate 2 Brands 6 8.3 ± 0.9 4-12
Ready to serve 2 Brands 30 3.3 ± 0.4 0-8
Homogenized cow
milk 3 Brands 19 <0.50*
ftnnan Breast Milk 10 Women <0.50*
*Limit of detection of non-flame atomic absorption spectrometry method used
in this study.
32
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A report demonstrated that pottery is capable of imparting as much as
7600 yg/liter of lead after an 8-hour acetic acid exposure (Stek, 1974).
In another study, twenty-five percent of the earthenware gave 100 yg/liter
lead in a standard test (Harris and Elsea, 1967). In addition, a plastic
tank used to store soft water for 18 months imparted 500 yg/liter of Pb to
the water. No lead was imparted to hard water by the same tank (Chancellor,
1960).
The pesticide, lead arsenate, contributes in some places to the con-
tamination of our air, water, and food supplies via spray drift, fugitive
dust, agricultural run-off, and by systemic incorporation in and by residues
on 23 common fruits and vegetables. This source is not as significant as it
once was due to a decline in its use. However, residential districts near
agricultural areas using lead arsenate, or on land previously used for orchard
crops, should be monitored. Also, market-basket samplings should be made to
identify potentially harmful lead concentrations.
The domestic production of lead arsenate in 1971 was 3,100 tons,* up
48% from 1970. The 1971 production was down 14% from the average production
of the previous five years, i.e., 3,550 tons. In 1971, the domestic dis-
appearance (contributions to environmental pollution) was 2,550 tons. This
represents a decrease of 29% over the average of the previous five years
(Fowler, 1973).
In 1972 domestic production of lead arsenate was 2,791 tons, down 9.5%
from 1971; however, domestic disappearance was 2,512 tons, up 21% from 1971
(Fowler, 1974).
A tolerance level of 7 parts per million combined lead has been
established for lead arsenate on the following 28 crops: apples, apricots,
asparagus, avocados, blackberries, blueberries, boysenberries, celery,
cherries, cranberries, currants, dewberries, eggplant, gooseberries, grapes,
loganberries, mangoes, nectarines, peaches, pears, pepper, plums, prunes,
quinces, raspberries, strawberries, tomatoes, and youngberries; and 1 part
per million on citrus crops (Code of Federal Regulations).
The Office of Pesticide Programs (OPP), EPA, operates a soils monitor-
ing program. The samples include both inner-city and suburban soils. These
samples will be analyzed for lead and will continue to be available for re-
analysis in a soil bank maintained by OPP.
All golf courses in the northeast and midwest were identified by the
OPP. A random sampling of the soil from the greens and fairways was made
and the following lead levels were found in the soil (Yang, in preparation
1975).
Depth Below Surface (cm) Greens (ppm) Fairways (ppm)
0-4 647.9 83.4
4-8 - 238.9 50.1
8-12 102.2 30.3
33
*1 ton = 2000 Ibs = 0.91 metric tons
-------
The average application rate for golf courses is 294 pounds of lead
arsenate per acre. It should be noted that the range of values for golf
course soils was 6 to 3,330 ppm of lead.
Lead arsenate was used as an insecticide in the growing of tobaccos
until about 1950. As a result of the changing patterns in pesticide usage,
tobacco has decreased from an average lead level of 130 ppm in the 1950's
to 20 ppm in the 1960Ts and appears to have leveled off at 20 ppm in the
1970's (Buckley, et al., 1973).
An example of the acute effects of high blood-lead concentrations in a
pregnant mother and her newborn infant are well illustrated in a case
reported by Palmisano, et al., (1969) in which these authors also state that
lead has a "devastating effect on reproduction and pregnancy since it most
commonly causes sterility or early spontaneous abortion." It has been
clearly shown that lead crosses the human plancenta and may cause untoward
effects in the fetus (Karlog and Mailer, 1968). Around the beginning of
this century it was recognized that women employed in the lead trades often
produced liveborn infants who were small, weak, and neurologically damaged
(Cantarow and Trumper, 1944; Angle and Mclntire, 1964).
CRITICAL SOURCES
Lead, which is found in the earth's crust, also occurs naturally in the
atmosphere and hydrosphere as a result of both physical and chemical
processes. Man's activities, of course, introduced the greatest quantities
of lead and lead compounds into the atmosphere and hydrosphere. For example,
lead or its compounds can enter the environment at any stage during the
mining, smelting, processing, and use of this metal and its derivatives.
Additionally, lead is stable and incrementally accumulates as a waste or
contaminant.
Increases in lead use have been on the order of 3% per year over the
last decade, and the total annual consumption of lead in the United States,
summarized in Table 11, is approximately 1.3 million short tons. However,
most of this lead is not in a form or use likely to pose an environmental
or health threat. In fact, over 40% of the annual consumption of lead comes
from recycling.
Major sources of lead causing or likely to cause adverse environmental
or health effects include exhaust from the use of leaded gasoline and other
fuels as oil and coal; the use of paint, ink coloring, and other pigments
containing lead; the use of lead in treating, processing, and packaging food;
the use of lead in water pipes, ceramic pottery, batteries, and pesticides;
the use of lead as a stabilizer in the manufacture of certain plastics; and
the mining, smelting, processing, and terminal disposal of lead-containing
materials. These and other sources bring large quantities of lead into man
and his environment via air, water, and food.
The principal sources of atmospheric lead are listed in Table 12.
Lead dusts entering the upper and lower respiratory tract are in the particle
34
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size range of from less than 1 to greater than 10 micrometers. Although
different particle size distributions and proportions emanate from these
various sources, the resulting size profile, after gravitational and atmos-
pheric interaction, is believed to be approximately a logarithmic normal
distribution. Consequently, various sources of respirable airborne lead
ultimately yield a somewhat similar size distribution profile (Lee, et al.,
1968; Task Group on Lung Dynamics, 1966).
Table 11. LEAD CONSUMPTION IN THE UNITED STATES (Short Tons)*
(Information from National Academy of Sciences 1972)
Uses 1968 Totals
Metal Products 915,500
Pigments 109,734
Chemicals* 262,526
Coatings and Miscellaneous 41,030
GRAND TOTAL 1,328,790
*261,897 Tons are gasoline additives.
Table 12. EMISSION SOURCES OF LEAD IN AIR
(Information from U.S. Environmental Protection Agency Position
on Health Implications of Airborne Lead, November 18, 1973.
Environmental Lead and Public Health, Air Pollution Control
Office, Publication No. AP-90, March 1971.)
Estimated Emissions
Source (Tons)*in 1968
Gasoline Combustion 181,000
Coal Combustion 920
Lead Alkyl Manufacturing 810
Primary and Secondary Smelting 811
Incineration of Solid Wastes 11,000
Other (pesticides, paint degrada-
tion, construction materials, inks,
chemicals, etc.) 755
TOTAL - 195,296
*1 ton = 2000 Ibs = 0.91 metric tons
35
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Patterns of lead emission to the atmosphere have changed in modern
times. Emissions from coal burning and smelting have been checked by
improved industrial controls, but these decreases have been more than offset
by emissions from automobile exhaust fumes. Today, about 98% of the air-
borne lead that can be traced to its source comes from combustion of gaso-
line (National Academy of Sciences, 1972). It is estimated that 66% to 75%
of the lead fuel additive is emitted into the atmosphere from motor vehicles,
and over one-half of this emission becomes widely dispersed.
Automobiles are moving sources concentrated primarily in or near resi-
dential areas. If the most critical receptors presently known are assumed
to be pregnant women and young children, and these receptors are also assumed
to be distributed throughout residential areas, it appears logical that
monitoring networks would be most efficacious in residential neighborhoods
immediately leeward of the more heavily traveled streets and adjacent to
major arterials. A correlation which might have general applicability can
probably be established between traffic volume, distance from the traffic,
and exposure levels in any urban area.
In addition, specialized monitoring stations are also desirable to cover
major fixed sources of respirable lead pollution such as smelters, public
incinerators, power plants, and agricultural areas using lead arsenate pesti-
cides. Here, meteorological considerations would be important in properly
locating monitoring stations in order to determine nearby residential expo-
sure levels.
In considering all routes of lead to the critical receptor, concern lies
in two areas: (1) total suspended particulates, and (2) dustfall containing
lead, either of which can be ingested and respired due to human and climatic
activity. The first category is in the size range under 10 micrometers, and
the second category is in the range above 10 micrometers. Concern also must
be given to particulate emissions from metallurgical processes, paint degra-
dation, building demolition, and other processes and operations which con-
tribute both to the general suspended particulate concentration and to more
localized dust concentrations.
QUANTITATIVE MATHEMATICAL MODELS
A generalized model for a pollutant distribution which can be used for
lead is presented below. In addition, submodels for various processes and
compartments are needed for the special problems of lead, and several of
these submodels have been developed for lead.
A qualitative representation of process in the pollutant-environment-
receptor can be represented schematically in a pollution chain diagram.
Some notations are included in the diagram which are explained below. This
diagram and the mathematical model were developed for the United States
Department of Health, Education, and Welfare by Lutz, et al., (1970).
36
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Transport Exposure Population
Sources _^ Pathways + Rate + Exposure
V° Di(t) dt
where E ., = the population exposure from pollutant i over time
tj to t£ through pathway j to man at location k
S., = the time varying source strength of the pollutant i
at location k (It represents the amount of pollutant
released into the environment that could ultimately
become a stressor to the population.)
p
jk = the transport pathway term for pathway j at location
k (It is a fraction, less than 1, representing the
environmental dilution processes from release at the
source until exposure of the population.)
D. = the exposure rate for the pollutant i (It includes
the exposure rate that man would be subjected to
from all modes of exposure and portals of entry.
In the preliminary stage of the model, ordinary differential equations
are utilized. Development of the model is an iterative process of exercising
the model in its preliminary stages, determining what changes are necessary,
and investigating mechanisms that better represent the system. Most of this
involves more detailed submodels. This iteration process includes sensi-
tivity analysis of the parameters of the model to determine how sensitive
the output of the model is to variations in the parameters of the model.
In this study, the approach used to develop the model was to represent
the total transport of the pollutant from the source to an individual as a
first phase, with the subsequent distribution in several body organs of the
individual due to the principal modes of entry into the body - inhalation
and ingestion.
A submodel for lead in the body describes the distribution of lead in
several body organs (lung, blood, bone, liver, and kidneys) due to intake
of lead from inhalation and ingestion (Lutz, et al., 1970). While the model
is not a very detailed representation of the biological processes, the pre-
dictions of lead in the body organs were within the accuracy desired. The
calculated blood-lead levels using the model were within a factor of two of
reported blood-lead levels. The quantitative predictions of blood-lead
37
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levels due to intake of lead by ingestion or inhalation were shown to be
valid within the accuracy of this preliminary modeling effort.
A submodel was also developed by Battelle (Lutz, et al. , 1970) for
young children having pica behavior and ingesting abnormally high amounts of
lead as in paint chips. Since ingestion of lead via foodstuffs was stated
to not vary significantly, no submodel for foodstuff ingestion was developed.
A model for lead distribution and movement through a watershed was
developed in the University of Illinois, Research Applied to Natural Needs
study on lead (Rolf, et al. , 1972). This model divides the watershed into
terrestrial and aquatic subsystems or zones and into additional subsystems
based on degree of lead exposure. The model distributes the lead to nodes
that are connected to the atmosphere, and the lead contained in each node is
distributed as follows:
= xi(t) d±i Si
where y.. = the quantity of lead moving from node i to node j
"^ during time period t
x. = the quantity of lead in node i
d.. = the flow, relative to other branches leaving i,
1J from i to j
n = the number of branches leaving a node *'
s . . = a seasonal factor for branch ij at time t (The
seasonal factor is a step function to simulate a
nonlinear function such as plant or animal growth.)
Once the relative flows between nodes (dij's) have been estimated, this
type of model is highly versatile. Each zone can be considered a separate
unit and different systems can be modelled by proper arrangement of units
and changing the internal configuration of nodes and branches. This model
was used to estimate future lead levels in the watershed areas of study.
An atmospheric lead transport submodel was developed and tested by
Battelle (Lutz, et al., 1970). This model was tested using data on airborne
lead concentrations in Cincinnati, Ohio, with lead in gasoline as the major
source. The atmospheric transport model did not provide a very detailed
representation of the atmospheric diffusion of lead; however, the predictions
of airborne lead concentrations using this model were within the accuracy
required. For an adult city dweller inhaling lead at an average concentra-
tion of 1.0 yg/m3 and ingesting 300 yg of lead daily via foodstuffs, the
predicted blood- lead level, from calculations using the mathematical model,
was 17.6 yg/100 g blood.
38
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While the models and submodels were developed by the United States
Department of Health, Education, and Welfare on a theoretical basis, they
were developed to simulate real-world interactions closely to the extent of
available data and knowledge. The predictions of the mathematical model are
quantitative and are based upon a systematic utilization of basic data
available as compared to guesses or intuition.
For the special problem of monitoring atmospheric lead from automotive
exhaust, the described models do not provide sufficient detail to account
for the variability from sources such as urban streets. This is required to
develop a practical monitoring system, and this type of submodel was develop-
ed during the workshop. The submodel is based upon the work of Ott (1974)
and is similar to the approach of Gilsinn (1972).
The problem of properly monitoring an atmospheric pollutant concentra-
tion can be better defined if a conceptual framework is constructed. The
purpose of such a framework is to facilitate the design of an overall net-
work which ultimately treats routes of exposure through all environmental
media.
For purposes of this submodel the overall lead particulate concentra-
tion that remains suspended in air (non-setteable) in a particular urban
area is assumed to be comprised of four different components:
(1) Contribution from mobile sources,
(2) Contribution from stationary sources,
(3) Contribution from other cities, and
(4) Geophysical background contribution.
The concentration measured at any location in the city and at any
moment of time represents the sum of these four components. The first two
contributions, the lead concentrations from mobile sources and from
stationary sources, vary greatly with locations within the urban area while
the last two, because they are very thoroughly mixed in the atmosphere, do
not vary spatially across the city.
This approach, which is referred to as "component analysis," treats
air quality at any location, C (x,y), as being the sum of these four
individual components: n
CT(x,y) = C + C +.L C (x,y) +4 C (x,y)
T G I 1-1 -M± 3-1 Sj
where C_ = total atmospheric lead concentration (yg Pb/m3)
Cp. = geophysical background concentration component
G (yg Pb/m3)
39
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C_ - long-distance extra-urban background concentration
component (yg Pb/m3)
CM (x,y) = component of lead concentration contributed by street
i i as a function of x and y distances from the street
(yg Pb/m3)
Cg (x,y) = component of lead concentration contributed by station-
j ary source .3 as a function of x and y distances across
the city (yg Pb/m3)
Figure 8 is a graphical representation of the equation. The vertical
axis shows the atmospheric lead concentration (yg Pb/m3), and the horizontal
axis shows distance across the city (km). If effect, this figure provides
a typical "cross section" of lead concentration as a function of horizontal
distance X. The components of concentration given in the above equation are
depicted on this figure. The total air-lead concentration C is the sum
of these components.
Components C and C are treated as constants, since they do not
vary with distance. Component C (x,y) is assumed to have many maxima,
one at each street. In Figure 8, each street may be viewed as perpendicular
to the plane of the figure, with traffic flowing toward and away from the
observer. Each of the narrow, tall maxima is the concentration "envelope"
contributed by the street. The airborne lead concentration arising from
vehicular exhaust is highest in the immediate vicinity of the traffic,
dropping off rapidly with distance from the highway. This concentration
component never quite reaches zero, however, because the contribution from
the next street or highway soon begins to have influence. The height of
each maximum is a function of traffic volume (vehicles/hour), road configura-
tion, traffic acceleration, and micrometeorology. The heights of the maxima
have been chosen to depict typical values. This picture represents, of
course, only an "idealization." In actual situations, the symmetrical
curves would be skewed somewhat due to the influence of wind. (For simplic-
ity, this skewness has been omitted from the drawing.)
The last term in the equation represents the concentration component
contributed by stationary sources of atmospheric lead. In general, sta-
tionary sources (smelters, power plants, incinerators) are more varied than
mobile sources. Furthermore, some cities may have more than one lead smelter
while other cities may have none. Due to this variability, "specialized"
networks should be set up to monitor air-lead concentrations immediately
around each stationary source. The distribution of these stations would
depend on the size and the nature of the source as well as local meteoro-
logical characteristics. The purpose of a specialized network is to gather
data on the highest concentration to which members of the general public
surrounding this source might be exposed. Because more than one stationary
source of atmospheric lead may be present in a given city, the last term in
the equation is shown as a summation term. The concentration from any given
stationary source is, of course, a function of the horizontal distance from
this source and other factors.
40
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ligPb/m3 -CROSS SECTION OF A CITY-
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
FREEWAY
MOBILE SOURCE
COMPONENT
STATIONARY
DISTANCE km
GEOPHYSICAL & EXTRAURBAN COMPONENT
.l - 0.4 ug/rrv* )
Figure 8. Spatial Distribution (Suspended Fraction) of Lead Concentration
(Geometric Mean) in Air
-------
If the purpose of the network is to monitor exposure of the general
population to the highest concentrations, it would be desirable to locate
monitoring sites where: (1) concentrations are highest, and (2) large
numbers of people congregate for relatively long periods. Thus, we are
interested in the joint occurrence of both high concentrations and large
numbers of people for long periods. A conceptual way to treat this problem
is to introduce the "population occupancy" function. This function is the
product of the number of people at a given location in the city and the time
they spend at this location. A hypothetical example of such a function is
shown in Figure 9 (solid curve) along with the total concentration distribu-
tion, i.e., the sum of the components in Figure 8 (broken curve). Typical
units are "people-hours," and these data can be obtained from an in-depth
urban survey of population activity in the urban area. (Such a survey
probably would include aerial photography.) ~
The joint occurrence of both high atmospheric concentrations and high
population occupancy for long periods of time at a given location would be
the basis for establishing a sampling station at that location. Locations
where these two variables were jointly large would be ranked. High-volume
samplers would then be installed, along with cascade impactors in some
instances, at locations receiving the highest ranking.
It should be noted that this suggested modeling approach does not take
into account the influence of resuspension of settled lead particles. At
this time insufficient information prevents inclusion of this important con-
tribution.
BASIC RESEARCH REQUIREMENTS
As a result of the review of the available literature and a considera-
tion of information requirements for the design of an integrated monitoring
system, many research requirements have been identified. Some of the more
urgent research requirements for critical receptors and transport pathways
are outlined in this section.
1. Research on Critical Receptors
a. Conduct research on lead exposure to children playing,
eating, and in other behavior with regard to lead intake
from air, dust on hands, food, and other contaminating
methods.
b. Determine the contribution of lead from the mother to
the newborn child. This should include pathological studies
and blood-lead level determinations in stillborn and aborted
fetuses, particularly for brain and nerve damage in those with
high blood-lead levels. Umbilical cord blood-lead level
determinations are needed.
c. Information on the respiratory physiology and ventilatory
absorption, retention, and excretion of lead in the infant and
42
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M9 Pb/m3
T
36
34
32
30
29
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
DISTRIBUTION OF 'TOTAL' LEAD CONCENTRATION
POPULATION x TIME (HYPOTHETICAL EXPOSURE)
DISTANCE, km
Figure 9. Hypothetical Exposure Cross Section to Total Atmospheric Lead
in a Typical Urban Area
-------
child is unavailable. Research to define minimum and
maximum daily rates of inspired lead under resting and
various activity-level states is required. No data exist
on the relations between the particle size of airborne
lead, ventilatory rates, and alveolar exchange, or the
degree of respiratory absorption in children. Existing
information is largely a poor estimate based upon model
information regarding suburban and rural children and
adults compared to urban children and adults.
d. Solubility factors (availability for absorption) should
be elucidated for various pollutant compounds, such as lead,
within the human body, particularly in children. For example,
the solubility of dusts and paint chips in digestive juices may
be significantly different with consequently different gastro-
intestinal absorption rates.
e. The effects of recent changes in recreational activities
need to be assessed; for instance, jogging and bicycling in
areas of heavy traffic and swimming in polluted rivers and
lakes. Additionally, research is needed to determine the
most representative vertical sampling zone or profile for
monitoring exposure levels.
2. Research on Transport Pathways
a. Definitive models need to be developed to relate lead
concentration, traffic volume, and distance from streets
and highways as well as to determine the vertical lead
distribution profile and the effects of local meteorology.
b. Research is needed on the resuspension of particulates
in the household. The extent to which settled particulates
reenter the air in a household is poorly defined. It may
depend on house cleaning, human traffic, and other activities.
This may vary from household to household. Tracer studies
could be undertaken to better define this phenomenon.
c. Multi-variate analyses are needed for heavy metals in air
particulates and gaseous air pollutants. Multi-variate analyses
would determine the correlations and relationships of these
variables with each other for different cities and different
site locations. Carbon monoxide and lead concentrations are
correlated with traffic volume, and effects observed may be due
to lead alone or lead combined with carbon monoxide (and perhaps
with other heavy metals).
d. Determine how lead is added to processed foods and recommend
measures to reduce this source of dietary lead intake.
44
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RESEARCH MONITORING REQUIREMENTS
In addition to basic research, which develops concepts and finds under-
lying natural mechanisms, there is also a need to apply the basic research
results to specific and highly individualistic situations. In order to do
this, very specific information is required about «ach situation. Much of
the information needed to implement monitoring system designs, both current
and hypothetical, is unavailable. The following section outlines the
various monitoring research requirements foreseeable for an integrated mon-
itoring system applied to lead.
1. Research on Critical Receptor
a. Research monitoring of blood-lead levels and other
parameters in children is required in areas of high
levels of lead in the air and in dustfall to determine
more accurately their part in childhood plumbism.
b. Research monitoring is required on blood-lead levels
in expectant mothers and new mothers in areas with high
exposure risk to lead. Correlations should be made
between mothers'blood-lead levels and that of newborn
infants.
2. Research on Transport Pathways
a. Research monitoring should be conducted in critical target
cities to monitor lead in air at 1 meter above the surface
in inner city areas, near freeways, in heavy traffic, near
gasoline stations and bus stops, and inside of highly
exposed houses.
b. Lead in dustfall should be measured in the same areas as
above.
c. Research monitoring is required to test and verify models
which would relate lead concentration, traffic volume, and
distance from streets and highways. There is evidence that
the highest atmospheric lead concentrations occur very close
to streets and highways, decreasing rapidly as distance from
the highway increases. Therefore, mathematical relationships
(with narrow confidence intervals) must be developed which
would ultimately enable the concentration very near streets
to be estimated for highways in any given city when just the
traffic volumes are known.
d. Vertical profiles should be determined for airborne lead con-
centrations. Monitoring instruments often are located at very
different heights. Therefore, it is necessary to fully document
the change in lead concentrations with elevation. A detailed
microscale monitoring research investigation is recommended for
the purpose.
45
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e. A relationship should be established between outdoor air-
borne lead and indoor airborne lead. Most members of the
general public, including critical receptors, spend most
of their time indoors. Thus, more accurate models are
needed which relate outside lead concentrations to inside
lead concentrations. These can be established by an in-
tensive indoor/outdoor monitoring research study using
houses in different locations, both near and far from
streets.
f. Research monitoring should be conducted around stationary
sources of lead pollution such as power plants (especially
those burning coal which has a high heavy-metal content),
incinerators, factories, or smelters when these are near
high population or residential areas.
g. Air-lead concentrations and blood-lead concentrations of
drivers in traffic should be measured. Drivers and passen-
gers in automobiles may receive high air-lead exposures;
thus, comprehensive data are needed on lead concentrations
inside vehicles moving in traffic. (These vehicles should
include school busses). Estimates should be made of the
integrated average concentrations for persons spending 2
to 8 hours in traffic.
h. Information documenting values of absorbable lead within
foods consumed in the diets of Americans, including all
subgroups and subcultural dietary considerations, is needed.
Population groups (especially children) likely to consume
large quantities of potentially high-lead content foods and
beverages should be determined.
Diets disproportionately composed of foods that are particu-
larly prone to contain or carry lead (e.g., legumes, fruits,
shellfish) should be monitored to establish base lines and/or
trends.
i. Many older sections of cities have lead water pipes. These
should be identified and the water monitored to obtain exposure
data for this source.
DESIGN OF AN INTEGRATED MONITORING SYSTEM
All people are exposed to environmental lead, and practical considera-
tions must prevail in establishing a monitoring system. It is, therefore,
necessary to rank the probable receptors according to environmental, physio-
logical, and behavioral criteria. In the case of lead, clinical evidence
overwhelmingly indicates the young urban child as the most critical receptor.
This may be due primarily to the combination of behavioral patterns and
the increased availability of environmental lead. Additionally, some recent
evidence also indicates that the child may absorb 5 to 10 times more lead and
46
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suffer adverse effects from lead at lower blood concentrations than adults
do.
Considerable scientific data exist about lead in numerous disciplinary
fields. However, a marked deficiency of respective intercommunication
between disciplines and the subsequent interpretation and analysis of these
data remains at the present time.
It is strongly recommended that an interdisciplinary team approach be
utilized as a part of any new monitoring system design. Computer systems
should be used. Computer systems should be envisioned and programmed prior
to the onset of monitoring for correlative and objective analysis of all
information to be gathered. Such an information system should permit future
modification, growth, and reorientation for continued use and cost benefit.
When the design model is complete, feasibility testing is recommended
for this monitoring system in several representative United States commu-
nities as soon as practicable. Such an opportunity to correlate inter-
disciplinary efforts can be utilized to obtain the needed dependent extra-
polation from studies performed on adults.
It is technically feasible to design an integrated monitoring system
for various pollutants after study of the variables and assignment of
tentative priorities. An integrated monitoring system designed on the basis
of modifications to a lead model system would probably have general appli-
cability because lead is universally prevalent in air, water, and food cycles.
IV. CONCLUSIONS
As a result of an analysis and review of the concept of an integrated
monitoring system for pollutants, using the test case of lead, the following
conclusions are presented:
1. The concept of identifying critical receptors, transport path-
ways, and sources appears to be a valuable method for developing
more efficient monitoring.
2. Design of a monitoring system which will provide usable informa-
tion directly for control of critical sources is very valuable.
3. The concept provides a framework for logically organizing exist-
ing information and provides a means of analysis to determine missing
information.
4. Appropriate models appear to be very useful for quantifying the
relative importance of various factors, especially major transport
pathways. More work is needed in evaluating and actually using and
testing models..
5. The concept and models provide the basis for designing basic
research and research monitoring programs to provide needed quanti-
tative data.
47
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6. Lead was a suitable pollutant to use as a test case, and the
criteria used for selecting it for this purpose appear valid. Many
gaps were discovered in the data on lead.
7. It is recommended that the evaluation of the integrated monitoring
concept be continued as follows:
a. Review mathematical models and use the data for lead
assembled in this workshop in the model and submodels
selected. Test the models, and determine the quantita-
tive data still needed for lead.
b. Use another test-case pollutant for further evaluating
the concept of the integrated monitoring system. Another
test case could be the cholinesterase monitoring system
for organophosphates used by the Department of Defense.
V. PARTICIPANTS IN THE WORKSHOP
VISITING PANEL PARTICIPANTS
Dr. J. Julian Chisolm, Jr., Baltimore City Hospitals, Baltimore,
Maryland
Dr. Henry Enos, U.S. Environmental Protection Agency, Washington, D.C.
Mr. Willis B. Foster, U.S. Environmental Protection Agency, Washington,
D.C.
Mr. William Henry, Battelle Memorial Institute, Columbus, Ohio
Dr. Dale W. Jenkins, National Institute of Scientific Research, San
Diego, California
Dr. Morris M. Joselow, New Jersey Medical School, Newark, New Jersey
Dr. Harold Lubin, Ohio State University, Columbus, Ohio
Dr. Wayne R. Ott, U.S. Environmental Protection Agency, Washington, D.C.
Dr. Michael B. Rabinowitz, Institute of Geophysics, University of
California, Los Angeles, California
Mr. William T. Sayers, U.S. Environmental Protection Agency, Washington,
D.C.
Dr. Paul Tompkins, U.S. Environmental Protection Agency, Research Triangle
Park, North Carolina
48
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LOCAL PANEL PARTICIPANTS
(All from the U.S. Environmental Protection Agency, Environmental Monitoring
and Support Laboratory, Las Vegas, Nevada)
Mr. Vernon E. Andrews
Dr. Delbert S. Earth
Dr. Joseph V. Behar
Dr. Stuart C. Black
Mr. Wayne A. Bliss
Dr. Maxwell E. Kaye
Dr. Robert R. Kinnison
Mr. Victor W. Lambou
Mr. Jerry J. Lorenz
Mr. Leslie G. McMillion
Mr. George B. Morgan
Mr. Alan Peckham
Mr. Edward A. Schuck
Dr. Richard E. Stanley
Dr. William W. Sutton
49
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/4-76-018
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
DESIGN OF POLLUTANT-ORIENTED INTEGRATED MONITORING
SYSTEMS A Test Case: Environmental Lead
5. REPORT DATE
April 1976
6. PERFORMING ORGANIZATION CODE
7. AUTHORIS)
Workshop participants
Dr. Dale W. Jenkins, Editor
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Monitoring and Support Laboratory
U.S. Environmental Protection Agency
P. 0. Box 15027
Las Vegas, Nevada 89114
10. PROGRAM ELEMENT NO.
1HD620
11. CONTRACT/GRANT NO.
68-03-0443
12. SPONSORING AGENCY NAME AND ADDRESS
Same as above
13. TYPE OF REPORT AND PERIOD COVERED
Interim
14. SPONSORING AGENCY CODE
EPA-ORD Office of Monitoring
and Technical Support
15. SUPPLEMENTARY NOTES
This report was edited by Dr. Dale W. Jenkins, National Institute of Scientific
Research, Rancho Santa Fe, CA 92067, a consultant under contract to EPA.
16. ABSTRACT
It is necessary to assure that monitoring measurements are directly
related to the population of highest risk and that the major sources of pollutants
are clearly identified and quantified. An integrated monitoring system is a
systems approach for providing the information necessary to permit efficient
control of those sources of pollutants causing major threats to the population
of highest risk. A "Workshop for the Design of a Pollutant-Oriented Integrated
Monitoring System" convened by EPA in March 1974 summarized the elements of
such a systems approach and discussed those information needs yet to be
satisfied by basic monitoring research.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Environmental biology
Mathematical models
*Monitoring
Operations research
Pollutant-oriented
monitoring systems
Environment simulations
06F
12A,B.
14F
21. NO. OF PAGES
62
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
UNCLASSIFIED
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
691- 216-1976
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