CALIFORNIA STATE UNIVERSITY, NORTHRIDGE
A STUDY OF TI1E DEPOSITION OF AUTOMOBILE
EMITTED LEAD ON PROPERTIES ADJOINING
A .MAJOR TRANSPORTATION CORRIDOR
A thesis submitted in partial satisfaction of the
requirements for the degree of Master of Science in
Health Science,
Environmental and Occupational Health
by
Angelo James Bellomo
,.
~
June, 1981
Tne Thesis of Angelo James Bellomo is approved:
Dr.
Mr. Owen Seiver, Chairman
California State University, Northridge
ii
ACKNOWLEDGl'viENTS
I wish to express my appreciation to Dr. Edward Gocka
and Dr. David Toppen, for their direction and assistance in the
preparation of this paper.
A special word of thanks is extended to Nancy Turnage
of Elite Secretarial Service, for her invaluable efforts in the
preparation of the final manuscript.
Finally, I would like to acknowledge my brother Sam, for his
many suggestions during the field work associated with this project.
iii
DEDICATION
This thesis is dedicated to my parents,
who have always been my source of strength and
inspiration.
And to Madeline, for her patience and
encouragement.
iv
TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS
iii
DEDICATION
iv
LIST OF TABLES
vi.i
LIST OF FIGURES
viii
ABSTRACT
ix
CHAPTER
I.
INTRODUCTION
1
The Problem
Focus and Purpose of the Study
Theoretical Framework and
Research Hypotheses . .
Organization of the Study
II.
2
3
4
5
REVIEW OF LITERATURE
Association of Environmental Exposures
and Blood-Lead Levels
Air Exposures . . . .
Lead-Paint Exposures
Dietary Exposures . .
Soil and Dust Exposures
Relative Source Contributions and
Research Needs
. . . .
The Highway as a Source of Lead
in Soils and Dusts . . . . .
Aerial Deposition of Automobile
Emitted Lead
.....
Existing Deposition Measurement
Systems . . . . . . . . . . .
The Bell Deposition Collector .
Deposition Rate as a Function of
Distance from Source
Stationary Sources
Mobile Sources
v
6
7
11
13
15
18
23
24
27
31
33
33
34
Page
III.
37
METHODOLOGY
Study Design . .
Study Hypotheses
Site Selection and Control Procedures
Srunpling and Analytical Methods
IV.
42
PRESENTATION OF THE DATA
Descriptive Analysis
Statistical Analysis .
'1.
37
39
39
FINDINGS, CONCLUSIONS AND RECOMMENDATIONS
45
45
56
58
REFERENCES
vi
LIST'OF TABLES
TABLE
Page
Estimated Relative Contributions of Lead
From Different Sources
19
Modified Es~imates of Relative Source
Contributions . . .
19
Atmospheric Deposition Rates in Selected
Areas
. . . . • . • • . . • • . • • •
25
SUI!Lmary Statistics for the Performance of
Alternative Collector Prototypes
32
5.
Site Conditions . .
41
6.
Measured Deposition Rates in Study Area .
47
7.
Table of Summary Statistics . • .
49
8.
Summary Table for the Analysis of Variance
49
9.
Summary Table for the Analysis of Variance-Log Transformed Data . . . . .
50
l.
2.
3.
4.
10.
i\nalysis of Variance for the Regression of
Deposit~on Rate on Distance Fr-om Freeway
....
51
11.
Analysis of Linearity . . . .
51
12.
Ar.alysis of Variance for the Regression of
Deposition Rate on Distance From Freeway-Log Transformed Data . . . . . . • . . • •
54
vii
LIST OF FIGURES
Figure
Page
1.
Study Design Matrix
38
2.
The Bell Deposition Collector
43
Map of Study Area
46
Equation for the Regression of
Deposition Rate on Distance
From Freeway . . . . . . . .
53
4.
viii
ABSTRACT
A STUDY OF THE DEPOSITION OF
AUTOMOBILE EMITTED LEAD ON PROPERTIES
ADJOINING A r-'1AJOR TRANSPORTATION CORRIDOR
by
Angelo James Bellomo
Master of Science in Health Science
Occupational and Environmental Health
The occurrence of lead in human populations is d,.w to
number of occupational and environmental exposures.
<:!
Associations
between the levels of lead in blood and exposures to lead in air,
soils, foods, water, paints and other materials are well documented,
and have been reviewed within this study.
In
examinin~
automobile emissions as a source of exposure,
a number of prior investigations have studied the relationship
between blood-lead and exposures to lead in air and soil environments.
In reviewing the literature, it is suggested that major limi-
tations are associated with the use of either soil- or air-lead in
reflecting total exposure to lead emissions.
ix
In the present study, the deposition of airborne lead is
examined in an area of residential housing adjoining a major
Los Angeles freeway.
Site-specific determinations of lead deposition
rate, or the mass of lead aerially deposited per unit area per month,
were made with a sampling device developed pursuant to this research.
The regression of deposition rate on the variable, distance from
freeway, was examined.
A strong and essentially linear relationship between the
variables under study, is demonstrated throughout the range of distances within the study area, and the use dt'posi tion rate is suggested
to provide an accurate reflection of exposure to particulate lead
emissions.
The findings of this study are useful in describing the
·mechanism by which automobile-emitted lead is distributed to critical
receptor properties along the freeway corridor.
X
CHAPTER I
INTRODUCTION
Toxic substances research has given considerable attention
to the effects of lead on man.
Most of this work has been directed
to the assessment of overt exposures among employees within the
lead smelting,
refin~ng
and manufacturing industries.
More recently,
lead as a widely distributed micropollutant affecting large segments
of the urban population has become an important area of investigation.
Today, it is widely recognized that the occurrence of lead in
htlffian populations has resulted from exposure to a variety of occupational and environmental sources.
In considering non-occupational
exposures to lead, the element is present in food, water, air, soil
and pain·t, and contributions to blood-lead from each of these have
been documented within the literature.
Although previously, exposure
to lead-based paints had been most extensively studied, recent efforts
have focused upon the relative contribution of multiple lead sources.
As a result, a good deal of light has been shed on the importance of
other sources of lead exposure, particularly those related to the
consumption of leaded gasolines.
The findings of an investigation by Caprio et al (1974) confirmed that the occurrence of excessive lead absorption is increased
by household proximity to major highways.
lished the
inhala~ion
Their work clearly estab-
cf automobile exhaust as an important factor
in the etiology of childhood lead poisoning.
1
Various other investi-
2
gators have successfully correlated undue lead absorption in children
and adults with various indicators of freeway lead exposure (Sayre
et al, 1974; Caprio et al, 1974; Cohen, 1973).
Further, two European invest:lgations have suggested that a
substantial health risk is taken by those who live or recreate beside
the freeway corridor.
Neukomm et al (1972) demonstrated that higher
rates of malignant neoplasms could be observed in populations residing
along three major highways in Grance.
A more recent inquiry by
Blummer (1976) found that of 2.32 adults residing on properties adjacent to a highway, 11 percent died of cancer during an observation
period of 12 years, while the corresponding figure for a traffic-free
neighborhood was 1 percent.
Additional work by Blurnrner (1977) has
led that author to the assumption that lead in gasoline may play a
significant role in the development of cancer.
The Problem
In 1978, approximately ten metric tons of lead gasoline
additives were consumed within the Los Angeles basin each day
(Nevitt et al, 1978).
Prior work by Friedlander (1975) provides for
the estimation that; nearly 75 percent of this amount was exhausted
to the atmosphere.
Of the amount exhausted, 56 percent or over four
tons per day, \vas deposited on or near traffic corridors.
It is suggested that an important area of research remains
to be undertaken within the environment of residential properties
adjoining the freeway corridor, where levels of exposure are greatest.
Soil- and air-lead concentrations have been studied in relation to
3
distance from both stationary and mobile sources, and have led to a
better understanding of aerial distribution processes.
But there are
major limitations to the use of these variables in reflecting exposure
to automobile-emitted lead.
It is suggested that the use of lead
deposition rates, or milligrams of lead deposited over an area of one
square meter per month (mg/m 2 -mo.), may significantly contribute to
an
~~derstanding
of how automobile-emitted lead is distributed to
critical receptor properties along the freeway corridor.
Focus and Purpose of the Study
This study has focused upon the local environment of residential properties adjoining a major transportation corridor.
Of
specific concern was the manner in which automobile-emitted lead is
distributed throughout an adjoining tract of housing.
The purpose of this study was to examine the rate at which
freeway-generated lead is deposited on adjoining properties, and
experimentally verify an assumed relationship
be~ween
deposition and distance from the freeway centerline.
the rate of
Inasmuch as
existing measurement systems did not provide for the determination
of site-specific deposition rates, the study purpose was extended to
include the development of a measurement system which could be practically applied within the study area.
Theoretical Framework and Research Hypotheses
A number of prior investigations have studied the health
4
implications of lead exposure at varying distances from both mobile
and stationary emission sources (Landrigan et al, 1975; Johnson et al,
1975; Caprio et al, 1974; Yankel et al, 1977; Roberts et al, 1974).
In nearly all such studies reported·, the exposure variable measured
over distance was the concentration of lead in either air oi soil.
Limitation.s in the use of these two variables are apparent
when considering exposure measurements over distance, as proposed in
this study.
Soil-lead concentrations are highly variable even within
the perimeter of a single residential property.
Air-lead concentra-
tions reflect only that portion of the emission consisting of relatively small diameter particles which remain suspended in air.
They
do not reflect that portion of larger particles which continually
settle-out of suspension where they may present major exposures
through the ingestion of contaminated soils and dusts.
It is suggested that deposition rates may more accurately
reflect total exposure to automobile-emitted lead within the study
area than either air- or solid-lead concentrations.
Conceptually,
deposition rates measured at roof level would be subject to less
extraneous variation, and could be more easily determined for each
·property within the. study area.
Central to this study is the hypothesis that a relationship
exists between lead deposition rate and distance from the freeway.
In order to shed light on the nature of this relationship, it is
further hypothesized that the relationship is linear.
ses are defined operationally in Chapter III.
These hypothe-
5
Organization of the Study
A review of the literature is undertaken in Chapter II.
The
concentrations of lead in various environmental media, typically
occurring throughout remote, suburban and heavily industrialized areas
are presented.
The reported associations of blood-lead levels with
each exposure medium is reviewed, and the relative contributions of
multiple sources are discussed in order to demonstrate the need for
greater focus on soil and dust exposures.
The highway as a source of lead in soils and dusts is examined, and the use of deposition rates is introduced as a means to
better understand how freeway lead emissions are distributed to
adjoining receptor properties.
In Chapter III, the methods employed in examining the relationship between deposition rate and distance from the freeway are
discussed, and the study design, research hypotheses and analytical
methods are defined operationally.
The data are reported and statistically evaluated in Chapter
IV.
Inferen<Zes are drawn on the relationship between the variables
under study, and tenability of the research hypotheses is examined.
Interpretations, conclusions and recommendations are offered
in the final chapter.
CHAPTER II
REVIEW OF LITERATURE
Association of Environmental Exposures
and Blood-Lead Levels
It has been estimated that over
161~000
metric tons of lead
were emitted into the United States atmosphere in 1976 (EPA, 1976).
Once
emitted~
this lead is subjected to various environmental proc-
esses including transport by wind, dry and wet deposition; and
resuspension.
Within the urban environment, or those areas subjected
to heavy industrialization, airborne lead may represent a major
source of human exposure.
Furthermore, through the deposition of
airborne lead, additional environmental sinks are created, as foods,
surface waters, soils and dusts are contaminatedL
Thus, the routes by which human populations are exposed to
lead are generally characterized as direct or indirect.
Direct
exposures occur as a result of inhaling airborne lead particulates
. or organic vapors.
Indirect exposures are those in which lead-
contaminated materials are ingested.
It is important to recognize
that human exposure to lead is the summation of exposures from many
individual sources.
Efforts to establish associations between environmental lead
exposures and human absorption have generally focused upon four
exposure routes:
(1) The inhalation of airborne lead; (2) The
6
7
ingestion of lead-contaminated foods and water; (3) The ingestion of
lead-containing paints; and (4) The ingestion of lead-contaminated
soils and dusts.
These exposure routes have been extensively studied,
and their associations with elevated levels of blood-lead are well
docw-nen ted.
Air Exposures
Lead-bearing minerals are naturally occurring throughout the
earth's crust, and natural airborne lead concentrations from this
source are estimated at 0.0004- 0.0012 ug/m 3 •
Chow and Earl (1972)
have found levels as low as 0.0012 - 0.029 ug/m 3 in a remote
mountainous area of California.
Extensive data are available for ambient air-lead concentrations throughout many urban and rural communities.
The National Air
Surveillance Network (NASN) has maintained such data for 300 urban
and 30 rural sites since 1957.
Examination of these data reveal lead
concentrations in rural air typically ranging from 0.01 to 1.4 ug/m 3 ,
with an overall average of 0.2 ug/m 3 (Akland, 1976).
In contrast,
ambient urban air-lead levels range from 0.1 to 5 ug/m 3 , with overall
averages of 1 - 2 ugjm 3 •
A level of 18 ug/m 3 has been measured in an
area within one mile of a lead smelter (Yankel et al, 1977), and
levels ranging from 26.9 to 54.3 ug/m 3 have been reported for a site
immediately adjoining a major Los Angeles freeway during rush-hour
traffic (N.A.S., 1972).
A number of investigations have attempted to study the
relationship between air-lead concentrations and levels of blood-lead
8
in human populations.
An extensive review of this subject has been
reported by EPA (U.S. EPA, 1977).
Differences in blood-lead values were examined in relation to
airborne lead for two distinct populations in Los Angeles County
(Johnson et al, 1976).
The first group consisted of residents living
in proximity to a heavily traveled freeway, with air-lead concentrations averaging 6.3 ug/m 3 •
The second group was comprised of suburban
residents of the Lancaster area, with an average air-lead concentration of 0.6 ug/m 3 •
Significant blood-lead differences were reported
for these two groups, with mean blood levels of 16.4 and 10.5 ug/dl
for the Los Angeles and Lancaster groups, respectively.
A prior investigation by Johnson and coworkers (1974) in
Houston, examined blood-lead levels of traffic policemen, parking
attendants and adult females living near freeways, in relation to
three matched control groups.
Statistically significant differences
in blood-lead for the policemen (mean, 23.1 ug/dl) and their controls
(18.4 ug/dl), and between the parking garage attendants (28.3 ug/dl)
and their controls (21.3 ug/dl) were reported.
ences in blood-lead were not
ways
(12~9
ug/dl)
~nd
not~d
Significant differ-
between the women living near free-
their control group (11.9 ug/dl).
An association between blood-lead values and ambient air-lead
concentration has been demonstrated by Yankel et al (1977) in an area
surrounding a primary lead smelter in Idaho.
Reductions in airborne
lead of from 18.0 to 10.3, 14.0 to 8.5, 6.7 to 4.9, and 3.1 to 2.5
ug/m 3 at four reported distances were noted for the period 1974 1975.
The authors reported a corresponding decrease in observed
9
blood-lead values for this period of time.
Although a strong correla-
tion was noted between the variables under study, the authors have
suggested that the ingestion of contaminated soils and dusts may
account for a major portion of the observed variation in blood-lead.
Angle and Mcintire (1974, 1977) have reported on their study
of three school populations during the period 1970- 1977.
The first
school was located adjacent to a battery plant and downwind from two
other lead emission sources.
The second school population was sampled
from a mixed commercial-residential area, and the third from a suburban area with no apparent source of lead exposure.
During the study
period, an impressive relation was observed between annual variations
in air-lead and blood-lead levels.
Annual air concentrations of from
1.48 to 0.10 ug/m 3 were remarkably paralleled by blood-lead values of
from 31.4 to 14.4 ug/dl foT all three study populations.
Johanson and Luby (1972) studied a population of children
living in proximity to secondary lead smelters, and found blood-lead
values of 30 and 22 ug/dl for the study and control groups, respec-tively.
These values were paralleled by air-lead concentrations of
3.5 and 1.5 ug/m 3 , respectively.
A study by !suchiya et al (1975) examined blood-lead values
of policemen who worked in five zones, defined by degree of urbanization, and ranging from central city to suburban.
A consistent
relationship was observed between the air-lead concentrations of the
five zones (ranging from 0.024 to 1.157 ug/m 3 ) and the corresponding
average blood-lead values (range, 17.0- 19.7 ug/dl).
10
A number of experimental studies have been reported in \-.rhich
volunteers were exposed to elevated air-lead concentrations (Kehoe,
1961; Gross, 1977; Rabinowitz, 1974, 1976; Griffin, 1975).
Griffin
(1975) used a gas chamber to expose eleven adult males to an air-lead
concentration of 10.9 ug/m 3 for 60 days.
At 12 weeks, the mean blood
level for the experimental group stabilized at 25.6 ug/dl, compared
to the pre-exposure mean of 20.5 ug/dl.
Griffin exposed a second
experimental group to an air-lead concentration of only 3.2 ug/m 3 ,
and concluded that even at this level, mean blood-lead values would
increase by 5 ug/dl following a 7-week exposure.
In reviewing the experimental work of Kehoe (1961), Gross
(1977) determined that under controlled exposures, blood-lead could
be elevated 0.38 ug/dl for each increase of 1 ug/m 3 in air-lead concentration.
Finally, Rabinowitz (1974, 1976) demonstrated a reduction in
blood-lead for a volunteer that was confined 109 days to a room in
which the air was filtered to remove airborne lead.
Upon leaving the
lead-free room, an elevation to the volunteer's pre-experiment bloodlead
v~lue
was also demonstrated.
From the no!1-experimental investigations reviewed earlier, it
is clear that increased air-lead concentrations are associated with
elevated levels of blood-lead.
It is unfortunate however, that few
studies have examined this association while controlling for relevant cofactors such as lead in soils and dusts.
The experimental investigations reported, do shed light on
the functional relationship between air-lead exposures and levels of
11
blood lead.
Collectively, these investigations demonstrate a strong
association between increases of 2 to 3 ug/m 2 in air-lead, and
observed levels of blood-lead.
Although the relationship of these
two variables is not yet clearly defined, it has been estimated that
within the range of air-lead concentration typically found in the
urban environment,, blood-lead is elevated 1 to 2 ug/dl for each
1 ug/m 3 of lead in air (EPA, 1977).
Lead-Paint Exposures
It has been generally accepted that lead-based paints on
deteriorated dwelling surfaces, represent the single-most important
factor in the development of overt pediatric lead poisoning
(Lin-Fu, 1973).
A review of the reported studies in this area how-
ever, leads to a conclusion that observed increases in the blood-lead
of urban populations cannot be explained in terms of lead-paint
exposure alone.
Lead poisoning in children was first reported in the literature nearly a century ago (Gibson et al, 1892), and by the middle
1920's, lead paint as a contributing factor was fairly well established (Ruddock,
1~24).
Nevertheless, the marketing of leaded paints
for interior dwelling surfaces continued until less than a decade ago.
Obviously there remains a significant number of dwellings with
interior lead-paint exposures.
Current exposures to interior paints containing a significant
lead content (i.e., defined as 1 percent lead), are reflected in part
by a study of nearly 2400 dwellings in Pittsburg.
Shier and Hall
12
(1977) found that 22 percent of the dwellings built after 1960 contained leaded paints, while over 70 percent built prior to 1940 had
lead paint exposures.
Only about 14 percent of the total sample was
found to contain lead-paint surfaces that were flaking or deteriorated, and thus judged to be clearly hazardous.
·while this data does
not necessarily reflect conditions of the nation-wide housing stock,
a separate study of 115 dwellings in Washington, D.C., had similar
findings (Hallet al, 1974).
The Pittsburg investigators also gathered blood-lead data for
over 450 children from the housing stock studied, and found a weak
correlation between blood-lead and lead-paint exposure.
This corre-
lation was strengthened by looking only at those dwellings with a
peeling, flaking or otherwise deteriorating paint surface.
In a study of 81 children in Cincinnati, Reece et al (1972)
found considerable lead exposure in dwellings, but this exposure was
not reflected in the measurements of blood-lead.
Galke et al (1975) studied blood-lead levels in relation to
lead in soils, traffic density, and lead-paint on exterior and
interior surfaces.
A multiple regression analysis was conducted, and
exterior paint-lead.was reported to be significantly related to
measured levels of blood-lead.
Most blood-lead data in the United States has been gathered
as a result of federally-funded screening projects.
Having identified
significant blood-lead cases during this screening, a number of
investigators have re-examined the horne environment for likely
13
sources.
It is noteworthy that several such investigations have
reported a significant proportion of blood-lead cases in which no
source of lead-paint could be found.
Specifically, Tyler (1970)
examined 5466 paint samples from homes in which lead-poisoning cases
•vere identified during a four year screening program from 1974 - 1978.
The author r8ported that only 67 percent of the paint samples exam.,.
ined, contained lead.
During a three year blood screening program in which over
1.3 million children were examined, The Department of Health,
Education and Welfare discovered nearly 114,000 with elevated levels
of blood-lead (U.S. D.H.E.W., 1977).
Of the 103,599 homes in which
children with elevated blood-lead resided, only 57 percent were found
to contain leaded paint.
Food and water are thought to provide an important contribution to baseline levels of lead in human populations.
A number of
experimental studies have shown that for each 100 ug of lead ingested
daily, blood-lead is elevated about 6- 18 ug/dl (U.S. EPA, 1977).
A variety qf foods have been examined for lead by FDA, and
that agency has estimated that dietary lead of about 100 ug/day is
ingested by young children (Ewing et al, 1979).
Mahaffey (1977) has
reported that a young adult is likely to ingest 150 - 200 ug/day from
dietary sources.
Lead in foods generally originates from either the deposition
of airborne lead on food crops and animal feeds, the absorption of
14
lead in soils, or as a result of food canning or processing.
The
concentration of lead in fresh and canned vegetables is reported to
average 0.128 and 0.458 respectively (U.S. FDA, 1974).
Settle and
Patterson (1979) have recently determined that levels of lead in tuna
were increased 4,000 fold by canning.
The lead content of most urban water supplies is thought to
be low (N.A.S., 1980) and Durfor and Becker (1964) examined drinking
water from 100 major U.S. cities, and reported a median level of
3. 7 ug/1.
Local conditions however, such as the use of leaded pipes,
have resulted in serious lead exposures.
Beattie et al (1972)
studied a local population in Glasglow, Scotland, which derived their
drinking water from a reservoir with a water-lead concentration of
17.9 ug/ 1.
Due to conditions in the distribution system however,
water direct from the tap was found to contain lead in concentrations
as high as 934 ug/1.
The author demonstrated a significant and
related elevation of blood-lead among the exposed residents.
Rabinowitz (1974) experimentally studied the effect of sustained daily oral intake of lead on blood-lead levels.
established an impressive
relati~nship
The author
between the variables under
study, and further,. determined the half-life of lead in the blood
once the intake was discontinued.
An extensive review of similar
experimental studies in both human and animal systems is provided by
the U.S. EPA (1977).
These studies consistently demonstrate that
oral intake of lead does result in elevated blood-lead, although a
quantitative relationship between real-life food exposures and levels
of blood-lead has not yet been clearly established.
15
Soil and Dust Exposures
The natural occurrence of lead in soils has been studied by
the U.S. Geological Survey and concentrations of 15 - 30 ug/g are
reported (Shacklette et al, 1971).
Nriagu (1978) has cited an
average global soil-lead concentration of about 20 ug/g.
Hirao and
Patterson (1974) have reported a soil-lead level of 9.2 ug/g within
a remote mountainous area in the High Sierras.
In examining levels of soil-lead in 17 cities, the U.S. EPA
(1977) has reported an average urban value of less than 500 ug/g.
Solomon and Natusch (1977) studied urban soils in Illinois and found
levels ranging from 132 to 11,760 ug/g near exterior dwelling sur. faces, and 240 to 6,640 ug/g at distances away from those surfaces.
A median level of 585 ug/g was Teported by Galke et al (1975) in
their study of 194 urban sites in Charleston, South Carolina.
The present author examined soils from six residential properties adjoining a chemical waste processing facility in Los Angeles,
and found lead concentrations ranging from 400 to 11,000 ug/g
(Bellomo, 1980).
Residential soils have been studied near other
stationary sources; and levels as high as 12,000 ug/g have been
reported (Barltrop, 1974; Creason et al, 1975; Lepow et al, 1975;
Landrigan et al, 1974).
The occurrence of lead in housedusts and street residues has
been the subject of several investigations.
Needleman et al (1973)
examined the lead content of classroom and playground dusts, and
16
p '
reported levels of 2000 and 3000, respectively.
Housedust have been
reported to contain between 279 and 11,000 ug/g of lead (U.S. EPA,
1977).
Needleman and Scanlon (1973) found levels of 1,000- 2,000
ug/g in a number of homes in Boston and New York.
Finally, Landrigan
et al (1974) studied lead dusts in a number of homes within 4.8 km of
a lead smelter in El Paso.
Levels as high as 29,386 and 103,750 ug/g
were reported for homes within 4.8 and 1.6 km of this source, respectively.
Street dusts have been reported to contain 206 to 20,000 ug/g
of lead (Nriagu, 1978) and a survey of street residues in 77 midwestern cities were found to contain average lead concentrations of
1636 and 2413 ug/g for residential and commercial/industrial areas,
respecticely (NRC, 1972).
Although human exposure to lead-contaminated soils and dusts
has not yet been associated with overt cases of lead poisoning,
these exposures have been related to chronic blood-lead elevation in
children (Buckley, 1973).
A number of investigations have reported
on correlations between lead in soils and levels of blood-lead, and
the ingestion of lead contaminated soils and dusts resulting from
normal childhood behavior, has been clearly established.
·the reported
litera~ure
Review of
in this area leads to a consensus that
observable elevations in blood-lead occur as soil-lead concentration
exceed 500 - 1,000 ug/g.
In a regression analysis of data from a
number of reported studies, the U.S. EPA (1977) determined a 3 to 6
percent elevation in blood-lead for every two-fold increase in soillead concentration.
17
Yankel et al (1977) have extensively studied environmental
sources of lead surrounding a primary smelter in Silver Valley, Idaho.
The authors demonstrated that lead in both soil and housedust was
independently related to observed levels of blood-lead.
A retrospec-
tive study of two lead poisoning cases in Charleston, North Carolina,
was reported by Fairey and Gray (1970), in which a significant association was established between soil-lead concentrations and the
reported cases of poisoning.
Galke et al (1975) segregated 194 preschool children into two
groups based upon their soil-lead environments.
The median soil-lead
level was 585 ug/g, with all values within the range 9 to 7890 ug/g.
The first group consisted of those children with soil-leads between
9 and 585 and the second group with levels between 586 and 7890 ug/g.
A 5 ug/dl difference in blood lead was observed between the two groups,
and a multiple regression analysis found soil-lead to be independently
associated with levels of blood-lead.
In a study of soil-lead exposure resulting from a primary
smelter in El Paso, a significant association between blood-lead
levels and concentrations of soil-lead was demonstrated (Landrigan
et al, 1975).
On the other hand, an investigation was reported by
Barltrop et al (1974) in which a correlation analysis failed to show
a relationship between blood-lead and exposure to lead in soils.
Lepow et al (1975) examined the lead content of soils, housedusts and soil residues on the hands of ten children with elevated
levels of blood-lead.
The investigators reported that lead paint was
clearly not a factor in these cases and concluded that normal hand-
18
to-mouth behavior provided the route for absorption of contaminated
soils and dusts.
This mechanism of absorption was further studied by
Sayre et al (1974) who clearly demonstrated that significant amounts
of contaminated housedusts could be found on the hands of children,
and suggested that this source of lead could then be ingested through
the normal mouthing activity characteristic of children.
Finally, Duggan and Williams (1977) have reviewed the literature on lead dusts as a source of exposure, and have reported
their conclusion that SO ug of lead is added to the daily diet of
children through the ingestion of streetdusts alone.
Relative Source Contributions
and Research Needs
It has been firmly established that all of the sources noted,
individually contribute to elevated levels of blood-lead.
A number
of investigations have described in detail, the pathways by which
lead from each of these sources is transferred to receptor populations.
However, the relative contributions of lead from each of
these sources represents an area in which further investigation is
needed.
In modifying a method developed by Drill et al (1979) a
recent committee of The National Academy of Sciences (N.A.S.) has
estimated the relative contributions of multiple lead sources for
two hypothetical situations (N.A.S., 1980).
Table 1, presents the
estimated source-specific contributions for both children with and
without pica and an accessible source of lead-based paint.
From
19
TABLE 1
ESTIMATED RELATIVE CONTRIBUTIONS OF
LEAD FROM DIFFERENT SOURCES
Cona:ntration
Routcol
Exposure
oil=! in
Environment
.-\moun: Inhaled
or ln~ested
Per Day
At.wrption
Factor
Amount ol
1=1 Absorbed
(J.l!Vday)
Percent of
Total Load
l
0.5
7
1.3
9.1
27.3
Absorted
Case 1: Children With Pica and an Aa:essible Source of l.ud- Based Paint
Food
0. 751'!Vm 3
10 1<!VI
0.11-'!Vg
Soilfdust
Paint
500 l'lV~
10,000 1-'lVII
Air
WaJ.er
10 ml
1.4 I
0.4
0.5
0.5
0.3
0.11
I,OOOg
Ig
0.2 g
TarAL
Case i!: Children Withc>'JI f'icl and Without A=s.sible Paint
Air
0.751-'!Vml
10 ml
Water
10 l'g/1
1.4 I
food
0.11-'g/11
1,00011
Soil/dust
500 l'g/11
0.1 g
Paint
0.4
0.5
0.5
0.3
T<JJAL
Source:
50
!50
340
550
61.8
100
J
7
4
IS
9
67
20
75
100
50
National Academy of Sciences. 1980.
Lead in the Human Environment, p. 57.
TABLE 2
MODIFIED ESTIMATES OF RELATIVE
SOURCE CONTRIBUTIONS
Route of
Exposure
Concentration
of Lead
Amount of Lead
Absorbed (ug/day)
Percent of
Total
Case IU: Children With Pica and Without Accessible Paints
Air
0.75 ug/m 3
3
0.8
Water
10 ug/1
1.9
7
Food
0.1 ug/g
50
13.9
Soil/Dust
1000 ug/g
300
83.4
Total
100
360
20
this particular modeling approach, it is clear that in situation 1,
exposure to lead-based paint accounts for over 60 percent of the
total lead absorbed, whereas in situation 2, dietary sources of lead
provide by far the greatest contribution to the amount absorbed.
The NAS committee is quick to point out that the source
specific estimates. in this model are only hypothetical, and that
reasonable alterations in the source concentrations cited, could
result in marked differences in relative source contributions.
However, even the framework in which these estimates are presented,
tends to over-estimate the importance of lead-paint as a source of
lead absorption.
This bias for lead-paint is characteristic of many
prior approaches toward multiple-source modeling.
Table 2, represents this author's expansion of the NAS
estimates, in which a third situation is considered.
This situation
involves a population with pica, but without an accessible source of
lead-paint.
The soil-lead concentration has also been modified to
reflect conditions more typical of the urban residential envirorunent.
In this situation, automobile-emitted lead in soils and dusts would
contribute over 80 percent of the total lead absorbed.
It would appear that although leaded paint on deteriorated
dwelling Sllrfaces invariably represents a major source of overt lead
poisoning in children, a number of reported blood-lead differences
between urban and rural populations cannot be associated with this
source of exposure.
Many recent efforts have begun to challenge the relative
21
importance of leaded paints, and have suggested that the combustion
of leaded gasoline represents a major source of exposure among most
urban populations (Caprio et al, 1974; Cohen, 1973; and Sayre et al,
1974).
In assessing the contribution of automobile-emitted lead in
the etiology of blood-lead elevation, prior investigations have
generally considered either air-lead or soil-lead concentrations as
reflecting this source of exposure.
However, the use of either of
these factors is not without limitation, and their measurements often
do not reflect the true exposure to automobile-emitted lead at
individual locations.
For example, in order to study the association of air-lead
concentrations and levels of blood-lead in a group of 100 subjects,
it would be desirable to measure both variables for each subject.
Blood-lead is a relatively simple determination, and a measurement
for each subject would be practical.
Determinations of air-lea.d
however, are relatively complex, and an individual measurement for
each subject would not be feasible.
Rather, the subjects would
likely be grouped into several exposure levels, and an air-lead
determination for each level would be made.
Moreover, air-lead concentration is a factor which only
reflects that portion of the automobile emission which is suspended
in air, and provides for exposure only through inhalation.
It does
not reflect that major portion of the emission which settles out, and
provides for exposure via ingestion of contaminated soils and dusts.
The measurement of soil-lead is a relatively simple procedure,
and a sample from the environment of each subject would be practical.
22
However~
concentrations of lead in soil are extremely variable, and
even within the perimeter of a single residential property, extreme
soil-lead gradients are observed.
Localized drainage patterns, soil
alkalinity and organic content, local topography, and the effect of
nearby structures on the aerial deposition of
lead~
all contribute
to this variation.
Correlational studies which have examined automobile
emissions as a factor contributing to blood-lead, have thus been
limited inasmuch as both air- and soil-lead concentrations often
provide imperfect reflections of this factor.
In acknowledging this
lin1itation, it is suggested that an alternative variable be employed
to reflect exposure to automobile-emitted lead.
The concentration of lead in air, soil and housedust is
necessarily related to the amount of lead particulate emitted from
vehicular sources, and falling-out upon the landscape.
It seems
reasonable that the rate at which this particulate is deposited
(i.e., its aerial deposition rate), would more accurately reflect the
lead emitted, than either of the commonly used variables, air- and
soil-lead concentrations.
Further,deposition rates are likely con-
stant over the entire area of a specific property, and would thus be
subject to less extraneous variation than measurements of soil-lead.
Finally, deposition rates are more easily measured than suspended
air-lead, and thus, a separate determination for each property could
be feasible.
23
The Highway as a Source of
Lead in Soils and Dusts
It has been reported that the flow of lead throughout U.S.
industry resulted in the release of about 600,000 metric tons of
that element in 1976 (N.A.S., 1980).
This figure represents the
total amount of lead released into air, water and land environments.
Atmospheric lead emissions for 1975 have been estimated to exceed
161,000 metric tons, 88 percent of which were reportedly derived from
the consumption of automotive gasolines (EPA, 1976).
Huntzicker et al (1975) in reporting on the fate of automobile emissions, have estimated that nearly 90 percent of exhausted
lead is in a particulate form.
Further, these investigators report
that 30 percent of this particulate emission consists of relatively
small-diameter aerosols which become suspended in air, and thus
subject to long-distance transport by wind.
The remaining 57 per-
cent of this tail-pipe emission however, consists of larger particles
which undergo rapid settling within a few hundred meters of the roadway.
Friedlander and co-workers (1975) constructed a materials
balance for automobile-emitted lead in the Los Angeles basin.
From
their work, it has been estimated that 24 metric tons of lead in
gasoline are consumed each day in the basin.
About 18 tons/day are
reportedly exhausted to the atmosphere, while 6 tons/day are deposited within the engine and crankcase of the consuming vehicles.
Of
the amount exhausted, these investigators report that one-third is
I
'
24
transported by wind out of the basin, while two-thirds are aerially
deposited over the surrounding land_area.
The amount deposited is
designated as from either near or far deposition, and basin-wide
values of 9.5 and 2.0 tons/day are reported for these two categories,
respectively.
The work o.f Friedlander and Huntzicker provides for an estimate that within the Los Angeles basin, 55 percent of all vehicle lead
emissions are rapidly deposited on or near roadway corridors.
Inas-
much as automobile emissions are estimated to represent nearly 90
percent of total lead emissions, they likely provide an important
contribution to the amount of lead in urban soils, particularly withiP
areas inunediately adjoining major transportation facilities.
Aerial Deposition of Automobile
Emitted Lead
The transfer of airborne lead to aquatic and terrestrial
surfaces is generally expressed as a deposition rate, or mass of lead
deposited per unit area for a specified period of time.
The two most
commonly employed units for expressing deposition rates are milligrams lead per square meter per month (i.e., mg/m 2 -mo.) or nanograms
per square meter per day (i.e., ng/m 2 -day).
A number of reported deposition rates for urban, rural and
remote areas have been compiled by Nriagu (1978) and are included in
Table 3.
While a level of 0.01 mg/m 2 -yr (0.0008 mg/m 2 -mo.) was
reported for Antartica, levels exceeding 6000 mg/m 2 -yr (500 mg/m 2 -mo.)
have been documented near a secondary lead smelter in Toronto.
TABLE 3
ATMOSPHERIC DEPOSITION RATES
IN SELECTED AREAS
Site
Ocpo~ition flux
(mg Pb/n/ iyr)
·---------Near SourceB
Toronto, near secondary smeiter
M;ssouri, 800 ro frml" smeller
Cincinnati, < 10 m fror.1 hi;;hway
Toronto, near expressway
>6,0lJO
1,265
304
(100
Urban
New York City
New York City
Central Los Angeles
Los Angeles Basin (Pasadena, California)
Los Ange:es Suburbs
San Diego, California
London, England
Madison, Wisconsin
350
547
365-8,000
102-296
17-120
350
54
>25
Rural
France (11 location~)
Northwest England
Walker Branch Waterc;hed, Tennr~e.e
Dela,.·.tre River wdcr~lwds
Mt. tvioosilauke, 7\ew Hamv:>~ire
Uppt;r Great Lakes Bdsin
Lake Michigan
• OifS0uthern California Coast
14.6
<19.6
15.0
6.2
19.6
12.0
15.0
34.1
Remote
Scandimwian glaciers
Siar;. NcvaJa MountEi•1~, Q:!\f:.• mia
French Omgo
North'Central Paci!1c (\:can
Eastern Pa~:if:c Ocean
Nor:h ~.thntic Oce:m
Northern Greenknd
4.2
4,0
0.2
0.6
0.09
1.4
0.04
G~~~d
Ml
Antaroica
0.0!
Sour-ce: Nat1onal AcademYQrSoence~lm:
Lead in the Human Environment.
p. 154.
26
Deposition rates in Pasadena were determined for ten weekly
periods between November, 1972 and February, 1974 and reportedly
averaged 45 ng/crn 2 -day (13.5 mg/m 2 -mo.) (Huntzicker, 1975).
Angle and Mcintire (1977) examined
blood~lead
in relation to
lead in air and dustfall for three groups of children, and reported
deposition rates o.f 32.96 and 3.02 mg/m 2 -mo. for urban and suburban
areas, respectively.
The present author, in an earlier study of deposition rates
for two sites in Glendale, California, reported values of 32.2 and
11.5 mg/m 2 -mo. for areas of high and moderate vehicular traffic,
respectively (Bellomo, 1978).
A comprehensive study by Hinners and co-workers (1972)
examined lead dustfall in 77 U.S. cities.
Residential sites were
found to have deposition rates ranging from 1.57 to 57.0 mg/m 2 -mo.,
while values of from 5.50 to 57.0 mg/m 2 -mo. and 1.01 to 95.4 mg/m 2 -mo.
were reported for commercial and industrial sites, respectively.
Several studies have examined deposition rates in remote areas
where no localized emission sources exist.
Rabinowitz (1972) has
reported dep?sition rates for the Channel Islands off the coast of
· Southern Californi3;.
Values of approximately 0. 6 mg/m 2 -mo. were
determined on Santa Barbara, San Clemente and San Nicolas Islands,
while a value of about 0.9 mg/m 2 -mo. was reported for the Island of
San Clemente.
Similar deposition studies on these islands have been
conducted by Patterson and Settle (1974), Huntzicker et al (1975),
and Hidy.et al (1974).
The results of which are in general agreement
with the earlier works of Rabinowitz.
27
Finally, Hirao and Patterson (1975) examined deposition rates
for a remote mountainous area within the Sierra Nevada.
The particu-
lar canyon studied is 46 kilometers (km) from Yosemite Village and
17 km from the nearest road ending.
The investigators reported a
deposition rate of 0.03 ng/cm 2 -day, or 0.009 mg/m 2 -mo.
Existing Deposition
Measurement Systems
Conventional methods for the gross determination of total
settleable particulates, were often developed for assessing regional
diffe:cences in the amounts of wind-blown fugitive dusts.
Most prior
methods involved the use of large glass, stainless steel or polyethylene buckets, which were held in place by metal support stands.
Such dustfall buckets were generally positioned for a period of one
calendar month, during which time they collected the total fraction
of aerosols which fell-out of suspension under the normal force of
gravity.
In recent years, significant departures from the conven-
tional design of the dustfall bucket have resulted in the development
of several highly efficient measurement systems specifically for the
determination of lead and other trace metals.
In an effort to
standardize methods for the collection and analysis of total dustfall,
The American Society for Testing and Materials (ASTM) adopted such a
method in 1960 (ASTM, 1970).
This method was last revised in 1970,
and has been extensively used as a pattern for current monitoring
efforts in which the conventional dustfall bucket is employed.
The
ASTM method specifies procedures for the determination of pH, total
28
weight of settleable particulates, total water and benzene soluables,
and total combustible and noncombustible matter.
It does not specif-
ically address the analysis of trace metals.
In 1974, EPA reported the determination of lead deposition
rates which were derived by simply extending the
ASTI~
metal analysis as described by Hinners et al (1972).
method for trace
The bucket was
constructed of polyethylene, with a 20 em diameter opening (collection
area, 0.031 m2 ), height of 30 em with a slight taper toward the
bottom.
The bucket was positioned from an aluminum stand at a dis-
tance of at least 1.8 meters above the ground.
After the determin-
ation of total dustfall using the ASTM method, the sample was prepared
for trace metal analysis by boiling in dilute nitric acid and centrifuged to remove solids.
The solution was then quantitatively deter-
mined by atomic absorption.
The Califon1ia Department of Transportation reported a
variation of the ASTM method, in their study of particle deposition
along a 300 mile stretch of the San Diego Freeway (Caltrans, 1978).
Their collection device consisted of a plastic bag which was inserted
withir. a 15.2 em diameter and 30.5 em high metal container.
The
container was then ylaced into a 16.5 em diameter paint can which in
turn was fastened atop a wooden post at a height of 2.4 m above the
roadway surface.
The investigators report filling about half the
collector's volume with distilled water to which 5.0 mg of the
algicide, copper sulfate was added.
was reported.
not reported.
A sampling period of 30 days
The methods of sample preparation and analysis were
29
A large glass specimen jar with a diameter of 16.5 em
(collection area, 0. 021 m2 ) was extensively used in a routine sampling
program by The Southern California Air Quality Management District
(AQMD).
The purpose of that program, which continued for nearly 20
years, was to assess regional differences in the occurrence of
fugitive dusts throughout Orange County.
Further details of this
device are not reported within the literature.
In 1978, the present author evaluated the collection properties of the AQMD device, and three other collector prototypes
(Bellomo, 1978).
A comparison of lead deposition rates, as deter-
mined by each of the prototypes, for areas of high and moderate
traffic densities, was reported.
The prototypes studied were of
glass construction, with collection areas of 0.0210, 0.0088, 0.0064
· and 0. 0044 m2 •
The collectors were filled to approximately one-
third of their volumes with deionized water and positioned for a
period of one calendar month.
Upon return to the laboratory, the interior collector surfaces'
were washed in concentrated nitric acid.
The sample rinses were
placed on a hot plate and evaporated to near dryness.
Sample
residues were redissolved in concentrated nitric and perchloric
acids and again evaporated.
Finally, the residues were redissolved
in water and filtered for analysis by atomic absorption.
The prototypes with tapered or shouldered walls were found
to consistently collect and retain more lead per area than did the
AQMD prototype with straight-sided walls.
The measurement error
30
associated with the use of each collector was reported, and ranged
from 12 to 45 percent.
Huntzicker and Friedlander (1975) have developed a non-conventional measurement device to support their extensive study of lead
deposition rates in urban, rural and remote areas.
teflon disk (0.5
~n
A roughened
thick) with an exposed area of 0.0071 m2 provides
the collecting surface.
The teflon substrate is mounted directly to
a stainless steel disc, and thus the assembled collector presents a
relatively low profile to the wind.
The performance of this collector was studied, as were the
performances of simple variations using a teflon plate coated with
paraffin oil, and a 125 mm diameter crystallization dish filled with
\'later.
A one week sampling period was reported.
At the end of this
period, the plates were submerged in concentrated nitric acid and
the residues digested at boiling for one hour.
removed and the solutions evaporated to dryness.
The discs were
The residues were
redissolved in dilute nitric acid and analyzed by flame atomic
absorption spectroscopy.
The deposition rates for the three collector
variations were comparable, and the authors report experimental errors
(expressed as one standard deviation about the mean) of about 25
percent.
Hirao and Patterson (1975) determined lead deposition rates
in a wilderness area of the Sierra Nevada, by exposing 1300 pieces
of glycerin-coated roughened nylon, cut and assembled to simulate
wild sedge leaves.
Further details of sample collection and prepa-
ration were not reported, although deposition rates as low as
31
0.009 mg/m 2 -mo. were determined using isotope dilution mass spectrometry (IDMS).
The Bell Deposition Collector
Following an earlier. study of four alternative collector
proto:):.ypes (Belloms>, 1978) a 9 ern diameter glass jar with a slight
upward taper, was selected on the basis of its relative performance.
The Bellomo, or Bell collector was found to collect more lead per
unit area than the other prototypes studied, and the experimental
er~or
associated with its use compared favorably to those of other
deposition measurement systems.
Table 4, summarizes the performance of the Bell collector in
relation to the three others studied.
A group of six Bell collectors
were positioned on a roof-top in an area of high traffic density.
A second group of six were similarly positioned in an area of moderate
traffic density.
From the data, the reliability of the Bell collector
was established, and is reflected by size of the interval in which 95
percent of the measurement values were observed.
All six collectors
at each location were exposed to identical deposition fluxes (i.e.,
they were all in
th~
same location), and thus any variation in
deposition rate is attributable to measurement error.
The magnitude
of this error, however, was described as quite tolerable by the
author.
A thirty day sampling period is reported for the Bell
collector, and the methods for sample preparation and analysis are
discussed in Chapter III.
32
TABLE 4
STATISTICS FOR THE PERFORMA.l'l'CE
ALTERNATIVE COLLECTOR PROTOTYPES
Sill~tARY
---.
Site(l)
1
2
_
Prototype( 2)
?vteasured Deposition Rate
v
(3)
Experimental Error '
Limits(±)
%Error(.!:)
""
s
A
23.8
2.40
21.6
90.6
B
28.3
1. 76
2.8
9.9
c
32.2
3.19
3.4
10.4
D
28.9
2.11
2.2
7.6
A
9.5
1. 22
3.0
31.9
B
10.2
0.88
0.9
9 ... _
c
11.5
1. 76
1.8
16.2
D
12.6
2.82
3.0
23.5
....,,. _______
(1) Site 1, High Traffic Density; Site ? Moderate Traffic Density
(2) Bell Deposition Collector Identified as Prototype C
(3) At 95% Confidence Interval
~,
Source:
Bellomo, A. J., 1978. An Evaluation of Alternative
Collector Prototypes for the Determination of LeadDustfall Deposition Rates. Unpublished Report.
33
Deposition Rate as a Function of
Distance from Source
Few studies report on the relationship of deposition rates and
distance from stationary and mobile sources.
Despite the scarcity of
data in this area, existing reviews clearly indicate that atmospheric
lead is effectively removed by aerial deposition, and that this
removal mechanism is most efficient in the immediate vicinity of
emission sources (Huntzicker and Friedlander, 1975; EPA, 1978).
Moreover, the importance of distance on deposition rate may be
inferred from extensive soil-lead data near major stationary and
mobile sources.
Even at constant distances, deposition rates have been found
to be highly varia.ble and dependent upon such factors as particle
size distribution, airborne concentration and atmospheric conditions
such as windspeed and precipitation (EPA, 1978).
A number-of studies have examined deposition rates in areas
of high traffic densities or heavy industrialization, although
specific references to the distance relationship are generally not
reported.
This is perhaps due to the previous unavailability of a
deposition measurement system which could be easily applied at
varying distances from a source of lead emissions.
Stationary Sources
Roberts et al (1974) collected 130 deposition samples at
22 sites surrounding two lead smelters, and found an exponential
34
decrease in deposition rates with distance from both emission
sources.
The authors reported a reduction of 90 percent in deposition
rate at a distance of 300 m.
In this investigation, 81 percent of
the measured variation in these rates were accounted for by distance.
The distance relationship for stationary sources was not
further reported, although Nriagu (1978) has summarized monitoring
data, and reports deposition rates of 105 mg/m 2 -mo. at a distance of
800 m from a Missouri smelter, and 500 mg/m 2 -mo. near a secondary
lead smelter in Toronto.
Mobile Sou.rces
Huntzicker and Friedlander (1975) studied the deposition of
automobile-emitted lead in the Los Angeles basin, and reported that
nearly 57 percent of all exhausted aerosols are deposited on or near
the highway corridor, while 12 perc.ent.of this emission consists of
relatively small diameter particles which are transported out of the
basin by wind.
In a separate study, these authors (1975), further
defined the distance relationship by examining deposition rates
alongside a freeway and at distances of 30 and 115 m.
Rates of 675,
36 and 30 mg/m 2 -mo .. were determined for the three distances, respectively.
From this data, it is clear that deposition rate underwent
a 95 percent·reduction in moving from the freeway edge, to a distance
of 30 m.
These rates were based upon a one week sampling period,
during which time traffic volume averaged 62,000 vehicles per day.
Edwards (1975) likewise examined deposition rates at three
distances from a freeway, although the range of distances was much
35
greater.
Deposition rates of 42.6, 11.1, and 7.1 mg/m 2 -mo. were
determined at distances of 15, 4600 and 9500 m, respectively.
Traffic volume ranged from about 72,000 to 215,000 vehicles per day.
These findings differ considerably from those of Huntzicker and
Friedlander (1975).
The reported linear trend for the Edward's study
is unlikely, and sources other than the specified freeway is suspected.
Lynam (1972) studied removal mechanisms for airborne lead near
an expressway in Cincinnati, and reported that 50 percent of the lead
particulate emission was removed by dry deposition within 195 m of
the roadway edge.
Deposition values were not specifically reported,
nor were details of traffic volume.
Daines et al (1972) studied levels of airborne lead between
3 and 46 m from a freeway, and also reported a 50 percent reduction
in lead over this distance.
Finally, Caltrans (1978) examined the deposition of lead on,
and adjoining,a Southern California freeway.
Measurements were
obtained along the freeway centerline, along the east and west freeway shoulders, and at points 150 m either side of the centerline.
Deposition rates were not specifically reported, and a slight
increase in total lead collected, was observed in moving from the
furthest sampling point west to the furthest sampling point east.
The investigators attribute this trend to the predominate easterly
wind vector.
The present author has converted the raw data reported
in the Caltrans study to a deposition flux.
Values along the freeway
centerline averaged 11 and 106 mg/m 2 --mo. for the summer and winter
36
sampling periods, respectively.
Values along the east and west
shoulders for both sampling periods ranged from 22 to 100 mg/m 2 -mo.
Finally, values at points 150 m east and west of the centerline for
both sampling periods ranged from 5 to 22 mg/m 2 -mo.
Traffic volumes
for the summer and winter periods averaged 199,000 and 189,000
vehicles per day, respectively.
CHAPTER III
METIIODOLOGY
A tract of residential properties adjoining a major freeway
was established as an appropriate area J.n which the assumed relationship between the variables of interest could be tested.
A method for
site-specific measurements of lead deposition 1vas developed pursuant
to this research, inasmuch as an existing system of measurement had
not been reported in the literature.
The use of the Bell deposition
collector within the study area, thus provided a basis for the
methods employed in this study.
Study Design
The design of this study is correlative in nature and the
analysis based upon the general regression model.
Specifically, the
study is designed to examine the regression of deposition rates on
a single factor.
The factor under analysis, distance from source,
is both ordered and continuous, and its relationship with the dependent variable (i.e., lead deposition rate) is examined with a linear
regression analysis.
If a significant departure from linearity is
observed, the trend is to be evaluated using a curvilinear regression
analysis.
Conceptually, the design is fashioned as in Figure 1, with
o1 through D5 representing increasing distances from the freeway
centerline.
As shown, this factor is in five levels, each consisting
37
38
Distance From Freeway Centerline
(D)
yl
y6
Y'u
v
- 16
Yzl
Ys
Y1o
Y1s
Yzo
Yzs
Deposition
Rate
(Y)
FIGURE 1
STUDY DESIGN
~t~TRIX
39
of four deposition measurements.
Study
~theses
In Chapter I, the subject hypotheses were discussed within
the conceptual framework of this study.
Here, they are defined
operationally:
1.
Lead deposition rate (mg/m 2 -mo.) is negatively
correlated with distance from the freeway centerline.
2.
The regression of deposition rate on the variable,
distance from freeway centerline, is linear.
Site Selection and Control Procedures
In order to provide optimum conditions for examining the
relationship between the variables of
interest~
the following crite-
ria were used in the selection of the study site:
1.
An
accessible stretch of freeway with an adjoining tract
of housing in which all dwellings are situated on streets running
parallel and perpendicular to the flow of freeway traffic.
2.
An
depressed with
3.
entire tract of housing which is either level or
res~ect
to the freeway.
A freeway with an average daily traffic flow of at
least 100,000 vehicles per day.
4.
No nearby industrial lead emission sources.
5.
Favorable meteorologic conditions, i.e., minimal
precipitation and a prevailing wind component which is parallel
to the flow of freeway traffic.
40
6.
A sufficient number of property owners within the study
area, consenting to the placement of deposition collectors on rooftops.
Several prospective sites were exmnined, and a site meeting
these criteria was selected in an area of the San Fernando Valley,
20 miles northwest. of the Los Angeles Civic Center.
Sources of variation in deposition rates, other than distance
from freeway, include:
local meteorologic conditions; freeway traffic
volu.'Tie; local emission sources, and relative elevation of the freeway
and housing tract.
The effects of these variables upon the relation-
ship of interest were considered, and some controls were incorporated
within the criteria for site selection.
Specifically, local sources
of industrial lead emissions have been excluded from the study area,
and all receptor properties are equally depressed with respect to the
freeway.
Further, all receptor properties in each level are equi-
distant froin the freeway line of traffic, and the predominant wind
vector is perpendicular to each level of receptor properties.
In view of these design-oriented controls, it is suggested
that reasonable efforts have been made to ensure that any and all
·variation in measured deposition rates will be accounted for by the
variable ur..der study, distance from freeway.
It is of course possi-
ble that other intervening variables, not known to this author, may
provide some source of variation.
Finally, in crder that the results of this study may be
compared with future works, all known factors have been measured
and are presented in Table 5.
41
TABLE 5
SITE CONDITIONS
Freeway Traffic Flow
Annual ADT(l) (Vehicles/Day)
Peak-Hour Traffic Volume (Vehicles/Day)
128,000
12,800
Meteorologic Conditions(Z)
Precipitation
Prevailing Wind Vector
Site Elevation (m)
(Relative to Freeway)
None
NE, 5 mph
-3
(1) Average Daily Traffic
(2) October, 1980
Source:
Freeway Traffic Flow, Elenore Wood, Caltrans,
Personal Communication ~lay 15, 1981; ~leteorologic
Conditions, Ralph Keith, Southern California
AQMD, Personal Communication October, 1980.
42
Sampling and Analytical Methods
Deposition measurements were made using a system that was
developed pursuant to this research and in part, evaluated by this
author in an earlier study (Bellomo, 1978).
collector is presented in Figure 2.
A schematic of the Bell
This device is especially
designed for measurements of site-specific deposition rates, and is
easily positioned upon the roof-tops of receptor properties.
In a
pilot study, the statistics for which are sunuuarized in Table 4, an
experimental measurement error of 10 percent was associated with the
use of the Bell collector.
Following the consent of property owners, an array of 27 acidrinsed Bell collectors were positioned on the roofs of receptor
properties within the study area.
Two of these were field blanks.
The lids of the 25 experimental collectors were removed at the time
of positioning, and all collectors were in position within a period
of two hours.
The sampling period commenced on October 12, 1980, and
was terminated after 14 days.
in
t ~>':.
th~;;
The collectors were removed and sealed
same order in which they were positioned, and transferred to
, ':1oratory for analysis.
Upon receipt in the laboratory, two 10 ml aliquots of con-
centrated nitric acid were pipetted to each collector and the interior surfaces washed by mechanical agitation.
Complete washing was
enhanced by allowing the collectors to stand for a period of 0.5
hour.
The contents of each collector was transferred to 120 ml
43
Jar Lid
Collection Jar
Support Tube
I
I
I
I
I
I
I
I
I
\
'
-...
____
~---.,..,~~
/'1'
" \
I I~-...,__..,..~..J..-iI
I I
I
_..... )
/
I
I
I
I
I
Support Can
Roof-Top Plumbing Vent
FIGURE 2
1HE BELL DEPOSITION COLLECTOR
I
I
I
I
I
I
44
beakers with the aid of two 5 - 10 ml deionized water rinses.
Samples were placed on a hot plate and evaporated to near dryness.
The residues were then redissolved with 10 ml concentrated nitric and
1 ml perchloric acids.
The solutions were returned to the hot plate
and again evaporated to near dryness.
An
aliquot of 5 - 10 ml
deionized water was added to each beaker, and the contents filtered
into a 100 ml volumetric flask with the aid of two 5 - 10 ml water
rinses.
The filtrates were adjusted to a volume of 100 ml, a.nd
analyzed by flame atomic absorption spectrophotometry.
CHAPTER IV
PRESENTATION OF THE DATA
Descriptive Analysis
Deposition measurements were determined at four distances
from the freeway centerline, and at a remote area, far removed from
the freeway and thought to reflect ambient conditions.
Measurement
locations are shown in Figure 3.
Meteorologic conditions were recorded at a routine monitoring
station within the Hollywood-Burbank Airport, and the raw data for
October 1980 was obtained from The Southern California AQMD.
Freeway
traffic voltooes were annual averages for 1980, and were obtained from
Caltrans.
Refer Table 5.
The meteorologic conditions reflect a negligible precipitation, and a prevailing wind vector of 5 mph, SE, which is nearly
parallel to the flow of freeway traffic.
Statistic~!
Analysis
A group of four deposition rates were determined at each
distance from the freeway centerline as shown in Table 6.
An
additional group of four measurements were made on the two ambient
residential properties.
One of the observations in Group 4 was identified as an
outlier and excluded.
However a 95 percent confidence interval
45
46
Golden State Freeway
Holly~ood
Freeway
Scale: 1 em = 100 ft
FIGURE 3
MAP OF STUDY AREA
47
TABLE 6
MEASURED DEPOSITION RATES IN STUDY AREA
Group
Number
Distance From
Freeway (ft)
Deposition
Rate (mg/m 2 -mo.)
Group
Mean
1
100
20.0
13.5
10.8
8.6
13.2
2
350
7.6
8.8
5.6
7.9
7.5
3
700
4.7
6.7
5.6
3.9
5.2
4
1000
3.0
4.0
2.5
3.4
3.2
48
based on the t-distribution for the remaining three values in that
group, was found to encompass the sole detected value in Group 5, and
this observation was used to substitute for the outlier.
Summary
statistics for each group, following this modification, are presented
in Table 7.
The
sourc~s
of observed variation in deposition rates were
partitioned and identified with an analysis of variance.
data for this analysis is shown in Table 8.
The summary
The F ratio associated
with the sum of squares for between groups (distances), is significant at the one percent level.
Following the significant, p
< 0.01,
Bartlett's test for the
homogeneity of group variances, the data were log-transformed, and
the resulting analysis is reported in Table 9.
The regression of deposition rate on the factor, distance,
was examined with a linear regression analysis, the results of which
are reported in Table 10.
The F ratio for the variation due to
linear regression is highly significant.
The analysis thus far has assumed a linear relationship
between the variables under study.
deviation from
lin~arity
In order to examine whether any
is significant, the between groups swn of
squares has been partitioned in Table 11.
The resulting F ratio for
deviation from linearity is not significant, and it is concluded
that the data in fact describe a linear trend.
The correlation coefficient (r) for this linear relationship
is-0.808 and r 2 , or the coefficient of determination is 0.653.
Thus,
it is further concluded that 65 percent of the observed variation in
49
TABLE 7
TABLE OF SUMMARY STATISTICS
Group
Number
Number of
Observations
Sum
Mean
1
2
4
4
4
4
52.9
29.9
20.9
12.9
13.225
7.475
5.225
3.225
3
4
Variance
Standard
Deviation
24.416
1.822
1.449
0.402
4.941
1. 35
1. 20
0.634
TABLE 8
SUMMARY TABLE FOR THE ANALYSIS OF VARIANCE
Source of
Variation
ss
df
MS
F
10.641
3
224.19
74.729
Error
12
84.27
7.022
Total
15
308.46
Between Groups
Bartlett's test for the homogeneity of variances,
Chi-Square = 11.959, df = ~ p
0.01~ significant.
<
so
I
TABLE 9
SU~~y
Source of
Variation
Between Groups
TABLE FOR THE ANALYSIS OF VARIANCE
LOG TRANSFORMED DATA
df
ss
MS
3
4.057
1.352
Error
12
0.781
6.506
Total
15
4.838
Bartlett's test for the homogeneity of variances
Chi-Square = 1.449, df = 3, (not significant)
F
20.788
'
51
TABLE 10
ANALYSIS OF VARIANCE FOR THE REGRESSION OF DEPOSITION
RATE ON DISTfu~CE FROM FREEWAY
Source of
Variation
df
ss
MS
1
201.272
201.272
Deviation from
Regression
14
107.186
7.656
Total
15
308.457
Attributable to
Regression (Linear)
F
26.289
Correlation (r) ·········~·· -0.808
r-squared .... ~ . . • • . • • . . • . • . 0. 652
Standard Error of Estimate . 2.767
Regression Coefficient ... -1.038
Intercept . . • . • . . • . • . . . • • • 1. 287
TABLE 11
ANALYSIS OF LINEARITY
Source of
Variation
ss
MS
F
1
2
224.187
201.272
22.915
74.729
201.272
11.458
10.641
28.661
1.632
Error
12
84.270
7.022
Total
15
308.457
Between Groups
Linear Trend
Non-linear Trend
df
3
52
deposition rate is due to the factor, distance from freeway
line.
center~
Within the framework of this present analysis, it may also be
said that 35 percent of the observed variation in deposition rate is
attributable to other factors presently unknown.
From the regression coefficient and intercept reported in
Table 10, the regression of deposition rate on the variable, distance
from freeway, is graphically constructed as shown in Figure 4.
Finally, the regression analysis using log-transformed data
is reported in Table 12.
The coefficient of determination has
increased to 0.825_, showing some slight advantage for an exponential
model.
ln Chapter III, it was hypothesized that lead deposition rate
is negatively correlated with distance from the freeway centerline.
The highly significant F ratio demonstrated for this relationship,
reflects the tenability of this hypothesis.
Accordingly, the
hypothesis is accepted.
It was further hypothesized in Chapter III, that the relationship between the variables under study, is linear.
In Table 11,
the between groups sum of squares was divided into linear and nonlinear components .. From the corresponding F ratios, it is evident
that the data as so treated, do not significantly depart over the
range of distances from linearity, and thus, this hypothesis is also
accepted, even though an exponential model stabilizes variances and
gives a somewhat higher coefficient of determination.
From the graph of the regression equation, it would appear
that the observed non-linearity in the data is due to a single
53
Y (mg/m 2 -mo.)
20
0
15
0
E(Y)=l2.867- O.OlO(D)
10
0
0
0
0
0
5
0
0
200
600
400
800
D (ft)
FIGURE 4
EQUATION FOR THE REGRESSION OF DEPOSITION
RATE ON DISTANCE FROM FREEWAY
1000
54
TABLE 12
ANALYSIS OF VARIANCE FOR THE REGRESSION
OF DEPOSITION RATES ON DISTANCE FROM
FREEWAY -- LOG TRANSFORMED DATA
Source of
Variation
df
ss
MS
F
1
3.990
3.990
65.860
Deviation f:rom
Regression
14
0.848
0.061
Total
15
4.838
Attributable to
Regression (Linear)
Regression Coefficient .................... .
Intercept ................................. .
Correlation (r) ...............•...........•
r-squared (Coefficient of Determination) .. .
· Standard Error of Estimate ................ .
-1.462
2.616
-0.908
0.825
0.246
55
obse1~ation.
This is perhaps attributable to environmental conditions
existing at the corresponding point of sampling for that observation.
Specifically.~
the roof-top for this site was oriented in such a way as
to be effectively closer to the freeway than the other three sites in
that group.
CHAPTER V
FINDINGS, CONCLUSIONS AND RECOMMENDATIONS
In reviewing the literature, the present author has suggested
that exposure to contaminated soils and dusts significantly contributes to the absorption of lead in human populations.
Notwithstanding,
it is further suggested that the use of either soil- or air-lead concentrations in correlational studies with blood-lead values, may lead
to a weakening of the observed relationship between the variables of
interest.
It is suggested that relative to deposition rates, measured
soil- and air-lead concentrations poorly reflect total exposure to
automobile-emitted lead.
Air-lead concentrations reflect only that
portion of the total lead emission consisting of the aerodynamically
smaller particles which remain in suspension.
They do not reflect
that portion of lead particulates which quickly settle-out through
deposition processes and result in the direct contamination of soils
and dusts.
Site-specif~c
measurements of soil-lead are highly variable,
and even within the perimeter of a single property, extreme concentration gradients are encountered.
Essentially., the use of soil-
lead is limited because in a statistical sense, the variation within
groups often exceeds the variation between groups.
56
Thus, attempts
5]
to demonstrate associations between total exposure to lead emissions
and blood-lead values, using either soil- or air-lead as indicators,
are inherently limited.
The regression of lead deposition rate on distance from the
freeway centerline has been demonstrated within the study area.
A strong and linear relationship between these variables lends support to the suggestion that deposition rates may be useful in reflecting exposure to automobile-emitted lead and other particulates.
The usefulness of the Bell deposition collector for the
practicle determination of site-specific deposition rates has been
demonstrated.
It is suggested however, that the sampling period of
this collector be extended to one calendar month.
This modification
should eliminate the occurrence of an insufficient sample throughout
most urban areas.
In the wake of this investigation, it is recommended that an
additional study be conducted within the local environment adjoining
a major freeway, with particular attention to the multiple regression
of air-lead, soil-lead and lead deposition rates on the variable,
distance.
Throughout .the next decade, it is likely that lead in gasoline will continue to be replaced with other anti-knock additives,
particularly organic manganese compounds.
It is anticipated that the
findings of this study will serve well in initiating a better understanding of the mechanisms by which exhaust particulates in general
are distributed to critical receptor properties along the freeway
corridor.
REFERENCES
American Society for Testing and Materials.
for Collection and Analysis of Dustfall.
1970.
Standard Method
G. G. 1976. Air Quality for Metals, 1970 through 1974.
National Air Surveillance Networks, United States Environmental
Protection Agency, Office of Research and Development.
}~land,
Angle, C. R., and M. S. Mcintire. 1974. Lead in Air, Dustfall Soil
Housedust, Milk and Water: Correlation with Blood Lead of Urban
and Suburban School Children. Proceedings of the Eighth Annual
Conference on Trace Substances in Environmental Health.
Environmental Controls and the Decline of Blood Lead.
Archives of Environmental Health (in press).
Barletrop, D., C. D. Strehlow, J. Thornton, and J. S. Webb. 1974.
Significance of High Soil Lead Concentrations for Childhood Lead
Burdens. Environmental Health Perspectives. 7:75-84.
Beattie, A. D., M. R. Moore, W. T. Devenay, A. R. Miller, and
A. Goldberg. 1972. Environmental Lead Pollution in an Urban Soft
Water Area. British Medical Journal. 2:491-493.
Bellomo, A. J. 1978. An Evaluation of Alternative Collector
Prototypes for the Determination of Lead Dustfall Deposition Rates.
County of Los Angeles, Department of Environmental Health Services.
1980.
Trace Metal Contamination on Residential Properties
Adjoining a Chemical Processing Facility. County of Los Angeles,
Department of Health Services. Unpublished findings.
Blummer, W. 1976. Bleibenzin and Krebsmortalitat, Schweiz Med.
Wschr. 106, Nov. 15.
1977. Bleivergiftung durch Autoverkehr.
Behanlung in de Praxis. Schweiz. Rundschau. Med.
Und ihve
66.
Buckley, J., K. Bridboard, D. S. Hammer, R. Horton, M. Kanarek,
W. Moore, M. Piscator, L. Blumlee, S. Resnek, R. Rhoden, and J.
Stara. 1973. Position on the Health Implications of Airborne Lead.
United States Environmental Protection Agency.
California Department of Transportation. 1978. Dustfall Analysis
for the Pavement Storm Runoff Study. Report Number FHWA-CA-TL-78-12.
58
59
Caprio, R. J., H. L. Margulis, M. M. Joselow. 1974. Lead Absorption
in Children and its Relationship to Urban Traffic Densities.
Archives of Environmental Health. 28, April.
Chow, T. J., J. L. Earl, and C. B. Snyder. 1972. Lead Aerosol Baseline: Concentration at White Mountain and Laguna Mountain,
California. Science. 178-401-402.
Cohen, C. J., G. N. Bowers, M. L. Lepon. 1973. Epidemiology of Lead
Poisoning: A Comparison Between Urban and Rural Children. Journal
of American Medical Association. December 17.
Creason, J. P., L. A. Hinners, J. E. Bumgarner, and C. Pinkerton.
1975. Trace Metals in Hair as Related to Exposure in Metropolitan
New York Clinical Chemistry. 21:603-612.
Daines, R. H., D. W. Smith, A. Feliciano, and J. R. Trout. 1972.
Air Levels of Lead Inside and Outside of Homes. Industrial Medicine
and Surgery. 41:26-28.
Duggan, M. J., and S. Williams. 1977. Lead in Dust in City Streets.
The Science of the Total Environment.
Drill, S., J. Konz, H. Mahar, and .M. Morse. 1979. The Environmental
Lead Problem: An Assessment of Lead in Drinking Water from a MultiMedia Prospective. Office of Drinking Water. United States
Environmental Protection Agency.
Durfor, C. N., and E. Becker. 1964. Public Water Supplies of the 100
Largest Cities in the United States 1962. Geological Survey Water
Supply Paper 1812.
Edwards, H. W. 1975. Environmental Contamination by Automotive Lead.
International Symposium on Recent Advances in the Assessment of the
Health Effects of Environmental Pollution. Vol. III. Commission
of the European Communities.
Kwing, R. A., M.A. Bell, and G. A. Lutz. 1979. The Health and
~!lvironmental Impacts of Lead:
An Assessment of the Need for
Limitations. Office of Toxic Substances. United States Environmental Protection Agency.
Firey, F. S., and J. W. Gray. 1970. Soil Lead and Pediatric Lead
Poisoning in Charleston, South Carolina. Journal of South Carolina
Medical Association. 66:79-82.
Friedlander, S. K. 1975. A Material Balance for Automobile Emitted
Lead in the Los Angeles Basin. Environmental Science and Techno1£gy. 9: 448
60
Galke, W. A.~ D. I. Hammer, J. E. Keil, and J. W. Lawrence. 1975.
Environmental Determinants of Lead Burdens in Children. Proceedings
of the International Conference on Heavy Metals in the Environment.
National Technical Information Service.
J. L., W. Love, D. Hardie, P. Bancroft, and A. J. Turner.
1892. Notes on Lead Poisoning as Observed among Children in
Brisbane. Proceedings of the Intercolonial Medical Congress of
klstralia. Third Session.
Gibson~
Griffin, T. B., F. Coulston, H. Wills, J. C. Russell, and J. H.
Knelson. 1975. Clinical Studies on Men Continuously Exposed to
Airborne Particulate Lead. Environmental Quality and Safety Supplement II.
Gross, S. B. 1977. Statement Relating to the National Ambient Air
Quality Standard for Lead. Criteria and Special Studies Office.
Washington, D. C.
Johnson, W. C., and J.P. Luby. 1972. A Report on a Study to Determine the Blood Lead Levels in Dallas Children. Dallas Health
Department.
Hall, W. T., T. Ayers, and D. Doxey. 1974. Survey Plans and Data
Colle~tion and Analysis Metholdolgies:
As a Result of a Pre-Survey
for the Magnitude and Extent of the Lead Based Paint Hazard in
Housing. National Bureau of Standards NBSIR. 74-426.
Hidy, G. M. 1974. Characterization of Aerosole in California.
Interim Report for Phase I. State of California Air Resources
Board.
Hinners, T., J. Kent, W. Terrill, T. Heiderscheidt, R. Burton, and
A. V. Colucci. 1972. Metals in Atmospheric Particulate Collected
by Hi Vol Sampler and by Dustfall Bucket. United States Environmental Protection Agency.
Hirao, Y., and C. C. Patterson. 1974. Lead Aerosol Pollution in the
High Sierra Overrides Natural Mechanisms which Exclude Lead from a
Food Chain. Science 148:989-992.
1975.
Trace Metal Flows in Non-Urban Areas.
Air-Water-
J... and Relationships for Selected Pollutants in Southern California.
California Institute of Technology.
Huntzicker, J. J., S. K. Friedlander, and C. I. Davidson. 1975.
Material Balance for Automobile-Emitted Lead in Los Angeles Basin.
Environmental Science and Technology. 9:448-457.
61
Johanson, W. C., and J. P. Luby. 1972. A Report on a Study to
Determine the Blood Lead Levels in Dallas Children. Dallas Health
Department.
Johnson, D. E., J. B. Tillery, J. M. Rosenfeld, and J. W. Register.
1974. Development of Analytic Techniques to Measure Human Exposure
to Fuel Additives. United States Environmental Protection Agency.
Johnson, D. E., J. B. Tillery, and R. J. Prevost. 1975. Levels of
Platinum, Palladium and Lead in Populations of Southern California.
Environmental Health Perspectives. 12:27-33.
Kehoe, R. A., 1961. The Metabolism of Lead in Man in Health and
Disease •. The Harben Lectures. The Journal of the Royal Institute
of Public Health Hygiene. 24:81-97, 129-143, 177-203.
1963.
Toxicology.
Industrial Lead Poisoning.
Industrial Hygiene and
Landrigan, P . .J., S. H. Gehlbach, B. F. Rosenblum, J. M. Shoults,
R. M. Candelaria, W. J. Barthel, J. A. Liddle, A. L. Smrek, N. W.
Staehling, J. D. Sanders, and E. R. Fisher. 1974. Epidemic Lead
Absorption Near an Ore Smelter: The Role of Lead in Dust. New
England Journal of Medicine. 292(3):123-129.
Landrigan, P. J., S. H. Gehlbach, B. F. Rosenblum, J. M. Shoults,
R. M. Candeleria, W. M. Barthel, J. A. Liddle, A. L. Smrek, N. W.
Staehling, and J. D. Sanders. 1975. Epidemic Lead Absorption Near
an Ore Smelter. The Role of Particulate Lead. New England Medical
Journal. 292:123-129.
Lepow, M. L., L. Brickman, M. Tillelle, S. Markowitz, R. Robine, and
J. Kapesh. 1975. Investigation into the Sourc!=S of Lead in the
Environment of Urban Children. Environmental Research.
Lin-Fu, J. S. 1973. Vulnerability of Children to Lead Exposure and
Toxicity. New England Medical Journal.
Lynam, D. R. 1972. · The Atmospheric Diffusion of Carbon Monoxide and
Lead from an Expressway. PhD thesis. Department of Environmental
Science. University of Cincinnati.
Mahaffy, K. R. 1977. Quantities of Lead Producing Health Effects in
Humans: Sources of Bioavailibility. Environmental Health Perspectives. 19:285-296.
National Academy of Sciences. 1972.
National Academy of Sciences.
1980.
Sciences.
Airborne Lead in Perspective.
Lead in the Human Environment.
National Academy of
62
Needleman, H. L., and J. Scanlon. 1973. Getting the Lead Out.
England Journal of Medicine. 289:466-467.
New
Needleman, H. L., S.M. Shapiro, B. Dobkin, and 0. C. Tuncay. 1973.
Lead Levels in Denture and Circrenpulpal Dentine of Deciduous
Teeth of Normal and Lead Poisoned Children. Clinical Chemistry
Acta. 46.
Neukomm, S., S. Fritschi, C. Barbian. 1972. Te Test Rapide de
Cancerisation due Triton Applique a l'Etude des Poussieres Causes
par les par les Rneus a Claus sur L Autoroute du Ternan. Zeitsschrift fur Praventivmeddizin. 17.
Nevitt, J. S., J. A. Stuart, and M. Hoggan. 1978. Airborne Lead:
Sources, Concentrations, Health Effects. South Coast Air Quality
Management District.
Nraigu, J. 0. 1978. Lead in Soils, Sediments and Major Rock Types.
The Biog§ochemistry of Lead in the Environment.
National Research Council. 1972. Lead: Airborne Lead in Per~ective.
Committee on Biological Effects of Atmospheric
Pollutants. Division of Medical Sciences, National Academy of
Sciences.
·Patterson, C. C., and D. M. Settle. 1974. Contribution of Lead Via
Aerosol Deposition to the Southern California Bight. Journal de
Reec!}erche Atmospheriques.
Rabinowitz, M.
1972.
Chemosphere.
4:175.
Rabinowitz, M. D. 1974. Lead Contamination of the Biosphere by
Human Activity: A Stable Isotype Study. PhD thesis, University of
·California, Los Angeles.
Rabinowitz, M. B., G. W. Weatherwill, and J.D. Kapple. 1976.
Kinetic Analysis of Lead Metabolism in Healthy Humans. Journal of
Clinical Investigation. 58:260-270.
Reece, R. M., J. A. Reed, C. S. Clark, R. Angoff, K. R. Casey,
R. S. Challop, and E. A. McCabe. 1972. Elevated Blood Lead Levels
and the in situ Analysis of Wall Paint by X-Ray Flourescence.
American Journal of Disease in Children. 124:500-502.
Roberts, T. M., T. C. Hutchinson, J. Paciga, A. Chattopadhyay,
R. E. Jervis, and J. Van Loon. 1974. Lead Contamination Around
Secondary Smelters: Estimation of Dispersal and Accumulation by
Humans. Science. 186:1120-1123.
Ruddock, J. C. 1924. Lead Poisoning in Children with Special Reference to Pica. Journal of the American Medical Association. 82:1682.
63
Sayre, J. W., E. Charney, V. Jaroslav, and D. B. Pless. 1974. House
and Hand Dust as a Potential Source of Childhood Lead Exposure.
American Journal of Disease in Children. 127:167-170.
Settle, D. M.~ and C. C. Patterson. 1979. Lead in Albacore:
to Lead Pollution in Americans. Science (in press).
Guide
Shocklette, H. T., J. C. Hamilton, J. G. Boerngen, and J. M. Bowles.
1971. E!emental Composition of Surficial Materials in the Conterminous United States. United States Geological Survey: Professional Paper. 574-D.
Shier, D. R., and W. G. Hall. 1977. Analysis of Housing Data
Collec~~~n a Lead-Based Paint Survey in Pittsburgh, Pennsylvania.
National Bureau of Standards, Washington, D.C. (in preparation).
Solomon, R. L., and D. F. S. Nautsch. 1977. Environmental Contaminatio~_py Lead and Other Heavy Metals.
Vol. III. Distribution and
Characterization of Urban Dusts. Urbana-Champaign, Illinois.
Institute for Environmental Studies, University of Illinois.
Tsuchiya, K., M. Sugita, Y. Seki, Y. Yoboryashi, M. Hori, and
C. B. Park. 1975. Study of Lead Concentration in Atmosphere and
Population in Japan. Environmental Quality and Safety Supplement,
II. Lead. 95-147.
Tyler) R. L. 1970. Philadelphia Combats "Silent Epidemic" in the
"Ghetto" Lead Poisoning Control. Journal of Environmental Health.
33:64-71.
United States Environmental Protection Agency. 1976. Design of
Pollutant-Oriented Integrated Monitoring Systems: A Test Case:
Environmental Lead. United States Environmental Protection Agency.
1977. Control Techniques for Lead Air Emissions. Office
of Air Quality Planning and Standards. United States Environmental
Protection Agency.
United States Environmental Protection Agency. 1978. National
Ambi~pt Air Quali.ty: Standard for Lead.
Office of Air, Noise and
Radiation and Office of Air Quality Planning and Standards.
United States Environmental Protection Agency.
United States Department of Health, Education and Welfare.
Morbidity and Mortality Weekly Report. February 11.
United States Food and Drug Administration.
1974.
1977.
Unpublished data.
Yankel, A. J., I. Von Lindern, and S.D. Walter. 1977. The Silver
Valley Lead Study. The Relationship Between Childhood Blood Levels
and Environmental Exposures. Journal of the Air Pollution Control
Assoc~atJQn·
27:763-767.