United States
Environmental Protection
Agency
Health Effects Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S1-84-021 Jan. 1985
oEPA Project Summary
Measurement of Cadmium, Lead,
Zinc, and Calcium in Selected
Populations in the United States
R. J. Prevost, R. E. Thomas, and J. B. Tillery
As part of a continuing national and
international survey of cadmium (Cd)
ingestion, a study was performed to
estimate the daily intake of Cd and
other metals in two low-income popula-
tions in the United States: rural blacks
and urban Hispanics of Mexican-
American heritage. More than 260
persons were recruited and surveyed.
Feces, urine, and blood were collected
from each participant and analyzed for
Cd, Pb, Zn, Ca, and Fe; blood was also
analyzed for Fe-binding capacity and
hemoglobin; and urine was also ana-
lyzed for beta2-microglobulin and
creatinine.
Results indicate that ingestion rates
of Cd in both populations are slightly
lower than levels reported previously
for the general population of the United
States, and ingestion rates of Pb are
considerably lower (less than one-half)
than levels reported previously for the
general population. It was concluded
that nonoccupational exposures of
these two population groups to Cd and
Pb through ingestion is no greater than
and is probably less than that experi-
enced by the general population of the
United States.
This Project Summary was developed
by EPA's Health Effects Research
Laboratory, Research Triangle Park. NC.
to announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
Neither cadmium (Cd) nor lead (Pb) has
any biochemical function essential to
good health. Both metals are toxic at low
concentration, Cd more so than Pb.
The half-life of Cd and Pb in the body is
estimated to range from 5 to 30 years.
Increased accumulation of Cd in the body
will eventually lead to protemuna, renal
tubular damage, kidney failure, osteoma-
lacia, and nerve dysfunctions. Elevated
accumulations of Pb in the body may lead
to anemia, gastrointestinal dysfunctions,
encephalopathy, neuropathy, and neph-
ropathy. The "target" organ for Cd is the
kidney while bone appears to be the
"target" organ for Pb.
Industrialized countries have continu-
ally increased their use of Cd and Pb
which has resulted in an increased risk-
of-exposure for both occupationally and
nonoccupationally exposed populations.
This increased risk-of-exposure comes
from both industrial products and pollu-
tion. Industrial pollution has increased
the concentration of these metals m
water, air, soil, and food. Atmospheric
pollution of Cd and Pb is expected to
increase in the United States, as coal and
lignite replace petroleum feedstocks as
our major energy sources. Another im
portant source of Cd and Pb exposure is
cigarette smoking, which statistics indi-
cate is increasing in teenagers and
women. One pack of cigarettes contains
the equivalent of 25 /jg of Cd from dietary
sources when relative absorption rates
are accounted for. It is estimated that
smoking 30 cigarettes per day will provide
an average of 1 5 /jg of absorbed Cd to the
body.
Investigations of acute exposure epi-
sodes to Cd pollution have stimulated an
interest in the biochemistry of Cd and
have focused attention on the health
-------
effects caused by long-term exposure to
low concentrations of Cd in the diets of
different populations Recent studies on
Pb pollution have been concerned with
the health effects caused by exposure to
exhaust fumes from the combustion of
leaded gasolines and from point sources,
such as lead smelters, coal-fired power
plants, and battery reclamation plants
The application of sewage sludge to
crop lands has been practiced for many
years in this country. Presently, about 25
percent of all municipal sludges are
applied to land This presents another
source of toxic metals to the environment
and a direct link with the food chain when
applied to crop lands
Because Cd and Pb are accumulated by
certain vegetables and gram crops, and
dietary mfake is a major source of expo-
sure to the general population, the risk of
increased exposure to these metals is a
reflection of the increased contamination
of the environment The average daily
mgestion via food in noncontammated
areas has been estimated to range from
10 to 50 /jg for Cd and between 100 and
500 fjg for Pb Using a "market basket"
approach, the U S Food and Drug Admin-
istration has estimated the median
American diet to contain 39 fjg of Cd per
day Recent studies in nonindustnally
polluted urban areas of the United States
have estimated daily dietary intake of Cd
to range from 1 2 to 24 /yg/day by meas-
uring Cd in human feces. It has been
estimated that adult Americans absorb
29 fjg of Pb every day from atmospheric
and dietary sources
Absorption percentages for Cd and Pb
are estimated to be only 4 percent and 9
percent (approximate), respectively, and
these absorption percentages are influ-
enced by various dietary factors Studies
have indicated that vitamins, minerals,
and other trace metals can influence the
absorption of Cd and Pb For example,
levels of calcium (Ca), copper (Cu), iron
(Fe), zinc(Zn) and vitamin C in the diet will
affect the absorption rate of Cd and Pb.
Elevated absorption rates due to Fe defi-
ciency, protein deficiency, or decreased
levels of Ca in the diet could provide
tissue exposure to Cd and Pb at toxic
levels from diets that are otherwise within
normally acceptable limits
Because estimates of daily ingested
rates approach recognized toxic levels,
the quantities of Pb and Cd ingested by
the population of the United States are of
concern Some studies have provided
estimates for Cd and Pb by a "market
basket" approach and by measurement of
the metals in human feces More data are
needed to assess possible effects of
geographic, socioeconomic, ethnic, sex,
and urban-versus-rural differences. Three
high risk groups have been identified
among the various population groups
within the United States These are
vegetarians, high-rate consumers of
shellfish, and poor black and Hispanic
populations This study was designed to
survey mgestion rates and associated
health effects in the latter group The
survey addresses two very specific popu-
lation groups low socioeconomic rural
blacks and low socioeconomic urban
Hispanics These populations were
thought to be potentially at higher risk
than the general population because low
socioeconomic status limits the ability to
select certain foods and provides a bias
for grains, grain products, and vegetables
known to contain higher levels of Cd.
Food preferences in the two ethnic groups
may also provide a further tendency for
consumption of the higher Cd foods This
tendency may be accentuated for blacks
in rural areas where traditional food
preferences may be less affected by
recent social changes.
A number of very distinctive Hispanic
populations are residents in various areas
of the United States These include per-
sons of Mexican heritage, Puerto Rican
heritage, Cuban heritage, and others It is
recognized that no one of these heritages
is completely representative of all persons
of Hispanic heritage residing in the United
States However, to provide the study
with some degree of homogeneity in the
selected Hispanic population, only one of
these heritages was utilized—persons of
Mexican-American heritage. Persons of
Mexican-American heritage are the most
numerous among the various national-
ities of the Hispanic populations in the
United States, they are more widely
dispersed among the various states and
regions of the United States, and there
continues to be a greater influx of
Hispanic immigrants from Mexico than
from any other source of Hispanic popula-
tions.
Objectives
The general objective of this study was
to estimate the mgestion rates of Cd and
Pb in two subgroups of the population of
the United States, low socioeconomic
rural blacks and low socioeconomic urban
Hispanics, and to evaluate the evidence
of Cd toxicity. The specific objectives to
accomplish this general objective were:
1 select specific study populations
from the two subgroups of the
population of the United States;
2. obtain fecal, blood, and urine
samples and diet, health, and smok-
ing history information from the
selected study population;
3 measure levels of Cd and Pb in the
fecal samples and estimate daily
mgestion rates;
4 measure levels of Cd and Pb in the
urine and blood samples to provide
data relative to recent exposures
and to estimate body burdens,
5 measure levels of Ca and Zn in the
fecal samples to evaluate the pos-
sible effect on Cd status;
6. measure Fe in feces and serum,
total Fe binding capacity, and hemo-
globin to evaluate Fe deficiency;
7 measure beta2-microglobulin in
urine to evaluate for evidence of Cd
toxicity. It has been shown that
during Cd-induced proteinuria there
are large excretions of beta2-micro-
globulin. Elevations of protein have
been seen in populations with high
fecal and urinary levels of Cd;
8. measure creatinine and specific
gravity levels in urine for use in
adjusting urinary parameters for
urine concentration; and
9. determine significant patterns re-
garding mgestion rates, body bur-
dens, Fe deficiency, and Cd toxicity
inthestudy populationswith regard
to ethnicity, age, sex, smoking
history, and dietary habits and
compare these findings to results
for the general population of the
United States.
Design
The design of this study was to recruit
240 participants, 120 in each of two
population subgroups in the United States
as shown in the following table:
Number of Participants
Sex
Male
Female
Age
Young
12-18
Old
50+
Young
12-18
Old
50+
Urban
Hispanics
30
30
30
30
120
Rural
Blacks
30
30
30
30
120
-------
The study populations were focused
into two age groups to provide some
homogeneity regarding age and age-
related potentially confounding factors.
Age is an important characteristic which
influences exposure levels due to life-
styles and eating habits and which is
related to susceptibility The increase of
Cd levels in tissue with increasing age is
well documented. In order to provide the
opportunity for observing differences
related to age, two age groups were
selected, a young age group ranging 12 to
1 8 years and an older age group of 50 or
more years. The ages of 12 to 18 years are
important growth years with high con-
sumption of foods and building of much
tissue, potentially Cd-laden Because
tissue Cd is known to increase with age,
the older group is considered to have a
high susceptibility to continued Cd ex-
posure. Selection of these two age groups
provided a study population with high
susceptibility and with a sufficient spread
in ages for observation of age effects.
Census statistics were used to select
one urban and one rural community as
study sites to provide sufficient numbers
of low socioeconomic populations of the
required ethnic types. Within each selec-
ted study site, specific recruitment areas
were designated which exhibited particu-
larly uniform socioeconomic and ethnic
characteristics of the desired types. In
general, all residents of the designated
recruitment areas who met age and ethnic
requirements were considered eligible
Study participants were recruited
through personal contacts by trained
recruiters. Use was made of civic organi-
zations, church groups, and schools in
the selected study sites Potential volun-
teers were met at schools or community
centers and briefed on the objectives of
the study Informed consent was obtained
through the use of a specially designed
form. Volunteers were provided a package
that contained sample collection contain-
ers for urine and feces samples and
instructions for storage. Blood samples
were collected by medically trained and
licensed personnel at the school or com-
munity center. Study participants col-
lected and stored urine and feces samples
over a weekend and delivered the samples
to the study team on the following
Monday. Health, dietary, smoking, and
personal background information were
collected from each participant via inter-
view with use of a specially designed
health history record'form.
Each participant provided the following
samples: two 10-ml vacutamers of blood;
two 24-hour stool samples, and one 24-
hour urine sample The following meas-
urements were performed on the samples
collected:
Sample
Type Analysis
Feces Cd, Pb, Zn, Ca, Fe, and weight
Blood Cd, Pb, Fe, total Fe-bmdmg capacity,
and hemoglobin
Urine Cd, Pb, beta2-microglobulin, specific
gravity, creatmine, and volume
The study was conducted during an 18-
month period, beginning February 1980.
Samples were collected during the period
June to October 1980.
Conclusions
An important objective of this study
was to determine the ingestion rates of
Cd and Pb in two specific population
groups in the United States, urban
Hispanics and rural blacks, to compare
these levels to levels previously reported
for the general population of the United
States, and to determine whether these
two population groups are at high risk to
these toxic metals. Study results are
similar for the two study populations.
Ingestion rates of Cd in both populations
are comparable to but slightly lower than
levels reported previously for the general
population. Ingestion rates of Pb are
considerably lower (less than one-half)
than levels reported previously for the
general population. It is concluded from
the results that nonoccupational expo-
sures of these two population groups to
Cdand Pb through ingestion is no greater
than, and is probably less than, that
experienced by the general population of
the United States Thus, it appears that
the original hypothesis that thetwo popu-
lation groups are at higher risk of in-
gesting large quantities of these toxic
metals is false In the context of Cd and
Pb, their diet patterns are probably no
different from those of the general popu-
lation of the United States.
A second important objective of the
study was to evaluate the evidence of Cd
toxicity. It is concluded from the study
results that little or no evidence of Cd
toxicity has been found for either of the
two study populations
In addition to these major conclusions,
a number of secondary conclusions have
been drawn from the study:
1. There is no apparent Fe deficiency
in either of the study populations
2. Smokers tended to exhibit higher
levels of urine Cd than nonsmokers
in both study populations
3 Food consumption habits in both
study populations do not appear to
be oriented to the higher Cd foods.
4. A relatively high rate of heart
disease and high blood pressure
was self- reported by the older black
female study population
5 A relatively high rate of kidney
disease was reported by the older
black populations.
6. No correlation with Cd levels in
blood, urme, or feces was detected
for the populations with higher
reported heart disease, blood pres-
sure, or kidney disease.
7. Because no unusually high Cd
levels were found in the study popu-
lations, the potential for Zn or Ca
compounds to influence Cd status
was not addressed
-------
R. J. Prevost, R. E. Thomas, and J. B. Tillery are with Southwest Research
Institute, San Antonio, TX 78284.
Norman E. Kowal is the EPA Project Officer (see below).
The complete report, entitled "Measurement of Cadmium, Lead, Zinc, and
Calcium in Selected Populations in the United States," (Order No. PB 85-127
165; Cost: $13.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
•it U S GOVERNMENT PRINTING OFFICE, 1985 - 559-01 6/7877
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES PA
EPA
PERMIT No G-35
Official Business
Penalty for Private Use $300
IK
00004
------- |