Toxic Chemicals: Long-Term Coordinated Strategy Needed to Measure
Exposures in Humans (Letter Report, 05/02/2000, GAO/HEHS-00-80).
Pursuant to a congressional request, GAO reviewed efforts to collect
environmental health data, focusing on the: (1) extent to which states,
the Department of Health and Human Services (HHS), and the Environmental
Protection Agency (EPA) collect human exposure data on potentially
harmful chemicals, including data to identify at-risk populations; and
(2) main barriers hindering further progress in such efforts.
GAO noted that: (1) federal and state efforts to collect human exposure
data are limited, despite some recent expansions; (2) HHS and EPA have
been able to take advantage of improved technology to measure exposures
for more people and for a broader range of chemicals; (3) still, with
existing resources, HHS and EPA surveys together measure in the general
population only about 6 percent of the more than 1,400 toxic chemicals
in GAO's review; (4) for those toxic chemicals that GAO reviewed, the
portion measured ranged from 2 percent of chemicals prioritized for
safety testing to about 23 percent of those chemicals most often found
at Superfund sites and considered to pose a significant threat to human
health; (5) even for those chemicals that are measured, information is
often insufficient to identify smaller population groups at high risk,
such as children in inner cities and people living in polluted locations
who may have particularly high exposures; (6) at the state level,
efforts are similarly limited; (7) almost all state officials said they
highly valued human exposure data for populations within their borders,
and many provided specific examples of how such data have provided
useful information for interpreting citizens' health risks and guiding
public health actions; (8) three main barriers limit federal and state
agencies' abilities to make more progress; (9) first, federal and state
laboratories often lack the capacity to conduct measurements needed to
collect human exposure data--additionally, for most of the chemicals on
GAO's list, no laboratory method has been developed for measuring the
chemical levels in human tissues; (10) the second barrier, particularly
voiced by state officials, relates to the lack of information to help
set test results in context; (11) public health officials said they need
more information on typical exposures in the general population so that
they can compare this information with people's levels at specific sites
or with specific populations in their states; (12) they also said they
needed more research to relate exposure levels to health effects for the
chemicals of concern in their states; (13) the third barrier, of
particular concern at the federal level, is that coordinated, long-term
planning among federal agencies has been lacking, partly because of
sporadic agency commitments to human exposure measurement and
monitoring; and (14) HHS and EPA officials indicated that they have been
discussing the merits of establishing a coordinated interagency human
exposure program, but they have not yet formalized or agreed upon a
long-term strategy.
--------------------------- Indexing Terms -----------------------------
REPORTNUM: HEHS-00-80
TITLE: Toxic Chemicals: Long-Term Coordinated Strategy Needed to
Measure Exposures in Humans
DATE: 05/02/2000
SUBJECT: Toxic substances
Strategic planning
Data collection
Pesticides
Air pollution control
Environmental monitoring
Surveys
Interagency relations
Performance measures
IDENTIFIER: Superfund Program
National Health and Nutrition Examination Survey
EPA National Human Adipose Tissue Survey
EPA National Human Exposure Assessment Survey
NIH National Toxicology Program
NIH National Toxicology Program Human Exposure Initiative
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GAO/HEHS-00-80
Appendix I: Objectives, Scope, and Methodology
46
Appendix II: Reported Gaps in Human Exposure Data and
History of Federal Efforts
52
Appendix III: Survey of State Environmental Health Officials and
Results
62
Appendix IV: Comments From the Department of Health and
Human Services
68
Appendix V: Comments From the Environmental Protection
Agency
73
Appendix VI: Major Contributors to This Report
78
Table 1: Extent to Which Human Exposure Data Are Collected for Potentially
Harmful Chemicals Through NHANES or
the NHEXAS Pilot Surveys 14
Table 2: Prevalence of Elevated Blood Lead Levels in Children
Ages 1 Through 5, by Selected Demographic
Characteristics
(NHANES, 1991 Through 1994) 18
Table 3: Examples of How State Officials Use Human Exposure
Data 23
Table 4: Examples of Reports Calling for Coordination in
Environmental Health 32
Table 5: Number of Chemicals and Time Frames for Select
Federal Efforts 55
ATSDR Agency for Toxic Substances and Disease Registry
CDC Centers for Disease Control and Prevention
DP-HANES Defined Population Health and Nutrition Examination Survey
EPA Environmental Protection Agency
HHS Department of Health and Human Services
MTBE methyl t-butyl ether
NCEH National Center for Environmental Health
NCHS National Center for Health Statistics
NHANES National Health and Nutrition Examination Survey
NHATS National Human Adipose Tissue Survey
NHEXAS National Human Exposure Assessment Survey
NIEHS National Institute of Environmental Health Sciences
NIH National Institutes of Health
NRC National Research Council
NTP National Toxicology Program
PBT persistent, bioaccumulative, and toxic
PCB polychlorinated biphenyls
Health, Education, and
Human Services Division
B-282172
May 2, 2000
Congressional Requesters
State and local officials report continuing public concern over the health
risks posed by exposures to toxic chemicals, ranging from heavy metals such
as arsenic found at national hazardous waste sites to common pesticides used
in and around the home. For example, increasing rates of cancer in various
communities have prompted questions about the potential link to residues
from pesticides, indoor air pollutants, and other toxic chemicals.
Historically, estimates of human exposure to toxic chemicals have been based
on the concentration of these chemicals in environmental media--such as air,
water, and food--along with assumptions about how people are exposed.
Federal monitoring efforts have primarily focused on this type of
measurement. However, according to public health experts, measurements of
internal doses of exposure--actual levels of chemicals or their metabolites1
in human tissues such as blood or urine--can be a more useful measure of
exposure for some purposes.
Over the past decade, advances in laboratory technology have provided new
tools for measuring a broad range of chemicals in human tissues--tools that
can help researchers and health officials assess how much of a chemical has
been absorbed in the body and provide more accurate measurements of exposure
to relate to potential health risks. When gathered for the U.S. population,
such data can help identify new or previously unrecognized hazards related
to chemical substances found in the environment, monitor changes in
exposures over time, and establish the distribution of exposure levels among
the general population. These data can also help identify
subpopulations--such as children, low-income groups, or ethnic
minorities--that might be at increased risk because they face particularly
high levels of exposure. State and local health officials can use
information on typical exposures in the general population to help assess
environmental health risks for specific sites or populations within their
borders and to keep local residents informed. For example, local officials
in one community collected exposure measurements before, during, and after
the burning of arsenic-contaminated soil and found that no excess
exposure--as compared to typical levels found in the population--had
occurred.
In light of the potential benefits offered by these new technologies, you
asked us to review efforts to collect and use such information at both the
state and federal levels. Specifically, you asked us to (1) determine the
extent to which state and federal agencies--in particular, the Department of
Health and Human Services (HHS) and the Environmental Protection Agency
(EPA)--collect human exposure data2 on potentially harmful chemicals,
including data to identify at-risk populations, and (2) identify the main
barriers hindering further progress in such efforts.
We compiled a list of more than 1,400 naturally occurring and manmade
chemicals considered by HHS, EPA, and other entities to pose a potential
threat to human health. These included chemicals prioritized for safety
testing (based on EPA's findings that the chemicals may present unreasonable
health risks), chemicals linked to cancer, toxic chemicals frequently found
at Superfund sites, and certain pesticides monitored in foods or thought to
be potentially harmful to humans. For these chemicals, we assessed the
extent to which major HHS and EPA survey efforts--specifically HHS' National
Health and Nutrition Examination Survey (NHANES) and EPA's National Human
Exposure Assessment Survey (NHEXAS) phase I (pilot surveys)--were collecting
human exposure data. We also surveyed 93 environmental health officials in
50 states and the District of Columbia, receiving responses from 81
officials in 48 states for a response rate of 87 percent. At the federal
level, we focused on survey data collected for the general
(non-occupationally-exposed) population. We excluded federally sponsored
academic and private sector research. Appendix I explains our scope and
methodology in more detail. We conducted our work from March 1999 through
March 2000 in accordance with generally accepted government auditing
standards.
Federal and state efforts to collect human exposure data are limited,
despite some recent expansions. HHS and EPA have been able to take advantage
of improved technology to measure exposures for more people and for a
broader range of chemicals. Still, with existing resources, HHS and EPA
surveys together measure in the general population only about 6 percent of
the more than 1,400 toxic chemicals in our review. For those toxic chemicals
that we reviewed, the portion measured ranged from 2 percent of chemicals
prioritized for safety testing to about 23 percent of those chemicals most
often found at Superfund sites and considered to pose a significant threat
to human health. Even for those chemicals that are measured, information is
often insufficient to identify smaller population groups at high risk, such
as children in inner cities and people living in polluted locations who may
have particularly high exposures. At the state level, efforts are similarly
limited. Almost all state officials who we surveyed said they highly valued
human exposure data for populations within their borders, and many provided
specific examples of how such data have provided useful information for
interpreting citizens' health risks and guiding public health actions. For
example, state officials in nine states used human samples not only to
identify who was exposed to a toxic pesticide illegally sprayed in citizens'
homes, but to identify houses most in need of clean-up. Despite this
perceived value, most officials reported that they were unable to collect or
use human exposure data in most of the cases where they thought it was
important to do so.
Three main barriers limit federal and state agencies' abilities to make more
progress. First, federal and state laboratories often lack the capacity to
conduct measurements needed to collect human exposure data; additionally,
for most of the chemicals on our list, no laboratory method has been
developed for measuring the chemical levels in human tissues. The second
barrier, particularly voiced by state officials, relates to the lack of
information to help set test results in context. Public health officials
said they need more information on typical exposures in the general
population so that they can compare this information with people's levels at
specific sites or with specific populations in their states. They also said
they needed more research to relate exposure levels to health effects for
the chemicals of concern in their states. The third barrier, of particular
concern at the federal level, is that coordinated, long-term planning among
federal agencies has been lacking, partly because of sporadic agency
commitments to human exposure measurement and monitoring. HHS and EPA
officials indicated that they have been discussing the merits of
establishing a coordinated interagency human exposure program, but they have
not yet formalized or agreed upon a long-term strategy. A long-term
coordinated strategy should also ensure adequate linkages between collection
efforts and agency goals, provide a framework for coordinating data
collection efforts that considers individual agencies' needs and expertise,
provide a framework for identifying at-risk populations, and consider
states' needs for information. To address these needs, we are recommending
that the Secretary of HHS and the Administrator of EPA develop a coordinated
federal strategy for the short- and long-term monitoring and reporting of
human exposures to potentially toxic chemicals.
EPA projects a continuing upward trend in environmental compliance costs for
pollution control measures, amounting to an estimated $148 billion this
year. Hundreds of millions of dollars are spent monitoring levels of toxic
chemicals in the environment--for example, approximately $139 million of
federal funding supported national air-quality monitoring networks in the
United States in fiscal year 1999.3 Despite these expenditures, what often
is not known is the extent to which people are exposed to potentially
harmful chemicals in their daily lives, the chemicals to which they are most
often exposed, the levels of such exposure, how exposures change over time
in relation to regulatory policies, and the sources of exposure.
Policymakers, regulators, researchers, and public health officials must
often rely on estimates of human exposure levels for the general population
or for smaller groups thought to be at risk. Such estimates are often
derived from data showing the extent the chemicals are found in the air,
water, food, or other environmental media and assumptions about how and at
what rate the body absorbs the chemicals it contacts. A variety of methods
for measuring exposures are considered to be more direct than those that
measure chemicals in the ambient environment. These methods measure
exposures in people's more immediate environments and include tools such as
personal air monitors, which measure chemicals that may be inhaled. For
several chemicals and purposes, measuring internal exposure levels in human
tissues is considered the most useful and accurate measure and an important
piece of the information needed to link contaminants in the environment with
adverse health effects.
While officials may be able to collect internal exposure levels at a local
level, the results are difficult to interpret without information such as
comparative data to show what exposure levels might be considered high or
research findings linking exposure levels to specific health effects.
Because of the need for improved data on actual human exposures found in the
general population, the National Research Council (NRC), an arm of the
National Academy of Sciences, recommended in 1991 that the nation adopt a
new program to monitor chemical residues in human tissues, such as blood.
NRC noted that determining the concentrations of specific chemicals in human
tissues could serve to integrate many kinds of human exposures across media
such as air, water, or food and over time. As one component of an effort to
manage environmental quality and protect public health, NRC reported that a
well-designed national program for monitoring toxic chemicals in human
tissues was needed.4 NRC pointed out that human exposure data could be used
to help monitor changes in the population's exposure to chemicals and
identify population groups--by factors such as age or geographic
location--that might be at increased risk because they face higher levels of
exposure.
Direct biological monitoring of human exposure to chemicals has been made
increasingly possible by recent advancements in analytical chemistry and
molecular biology. Methods have been developed to measure smaller levels of
toxicants in body tissues and to do so with smaller sample amounts.5 For
example, a few years ago a laboratory would need 100 milliliters of blood to
detect dioxins in the part-per-billion range. New test methods use less than
10 milliliters and are capable of detecting concentrations in the
parts-per-trillion range. Single samples can also now be used to detect low
concentrations of multiple chemicals. Since 1995, for example, laboratory
methods have been developed to detect polycyclic aromatic hydrocarbons, a
group of more than 100 chemicals formed during the incomplete burning of
coal, oil, gas, garbage, tobacco, and other substances.
Lead is an example of a chemical that has been monitored extensively by
measuring absorption into human tissues--specifically, lead levels in the
blood. Elevated levels of lead in the blood can cause learning problems and,
at extreme levels, result in serious brain or kidney damage. Data on blood
lead levels have been collected for the national population since 1976.
Public health officials, researchers, and others have used lead exposure
data from large- and small-scale studies in many ways to identify at-risk
populations, evaluate regulatory actions, improve the models used to
estimate exposure, and identify significant sources of preventable exposure,
as shown in the following examples.
� Identifying at-risk populations: National blood lead data revealed that
low-income children living in houses built before 1946 had a prevalence of
elevated blood lead levels of 16.4 percent as compared to 4.4 percent for
all children ages 1 through 5; non-Hispanic black children in similar
housing had a prevalence of 21.9 percent--the highest risk of elevated blood
lead levels of any demographic group. Using this information, state and
local health officials can more effectively target screening and treatment
efforts.
� Establishing and evaluating public health-related policies: In the 1980s,
EPA was considering whether or not to make permanent a temporary ban on lead
in gasoline. National data on lead exposure showed a decline in average
blood lead levels that corresponded to the declining amounts of lead in
gasoline. Based on this and other information, EPA strengthened its
restrictions on lead in gasoline and required a more rapid removal of lead
from gasoline.
� Improving models used to estimate exposure: Experts indicate that an
increasingly important use of human exposure data has been as a "reality
check" on other indexes of exposure, such as questionnaires about activities
or work histories, to ascertain whether exposures may have occurred. For
example, prior to the decision to phase out lead in gasoline, exposure
models suggested that eliminating lead in gasoline would have only a slight
effect on blood lead levels, while actual testing showed a more dramatic
effect.
� Identifying key sources of exposure: When combined with other exposure
data, exposure measurements can help reveal the source of the exposure--an
essential step in developing and monitoring intervention strategies designed
to reduce or eliminate harmful exposures. For example, when no evidence of
lead paint--the most common source of lead contamination--was found in the
home of a child whose blood showed abnormal levels of lead, public health
officials were baffled. Observational data on how and where the child spent
time and environmental data from the surfaces most often encountered
revealed that lead-contaminated stuffing in a toy the child chewed likely
accounted for the high exposure. The child's blood lead level declined when
the contaminated toy was removed.
While lead is unique among chemicals in that it has been extensively
studied--decades of research has shown its harmful effects at increasingly
lower levels--such research has been possible in part because of laboratory
advances in measurement technology. Over the years, as technology improved
the ability to measure smaller and smaller amounts of lead in the
bloodstream, researchers have been able to identify increasingly subtle
adverse effects by linking blood lead levels and changes in neurobehavioral
functioning.
Although HHS and EPA each are expanding their survey efforts to use new
technologies and measure a broader range of exposures in the national
population, their measurement efforts cover a limited portion of the more
than 1,400 potentially harmful chemicals we reviewed. These surveys also
remain of limited value for identifying at-risk populations, because in the
case of their survey efforts, sample sizes to date have been
insufficient--and, for most chemicals, not representative of the general
population. In addition, federal efforts to help assess potential
disproportionate exposures by collecting data on communities living near
Superfund sites have been limited to few locations. State agencies reported
that their efforts are also limited, despite the importance they place on
using such data in their studies of population- or site-specific situations
within their borders. According to state environmental health officials,
they are often unable to collect these data.
In our examination of the HHS and EPA surveys, we found that the types of
chemicals measured have recently increased. For the past 40 years, HHS'
Centers for Disease Control and Prevention (CDC) has collected through a
survey nationally representative data on the health and nutrition of the
U.S. population. Exposure measurements are one component of this survey. In
the mid-1990s, EPA's Office of Research and Development initiated a human
exposure survey, which is currently in its pilot phase in three locations
across the country. A third more recent effort to monitor human exposures to
select chemicals was initiated in 1996 by HHS' National Institute of
Environmental Health Sciences (NIEHS) of the National Institutes of Health
(NIH). For each of these federal efforts, laboratory measurements are
largely conducted by the laboratory at CDC's National Center for
Environmental Health, which also developed many of the methods for
performing these measurements.
CDC's National Health and Nutrition Examination Survey
CDC collects human exposure data as part of NHANES, which has been conducted
periodically since 1960 and, beginning in 1999, has been conducted annually.
NHANES monitors trends in health status by conducting interviews and
physical assessments on a nationally representative sample of about 5,000
people per year. NHANES collects blood and urine samples for many purposes,
such as assessing cholesterol levels and the prevalence of diabetes. Since
1976, these samples have also been used to measure exposure to selected
chemicals, and excess samples are banked for future research. In the past,
CDC's human exposure monitoring efforts have focused largely on lead,
cadmium, and a few pesticides and volatile organic compounds--chemical
compounds which include a number of animal and known or suspected human
carcinogens found in tobacco smoke, building supplies, and consumer
products.6 Starting with the 1999 NHANES, CDC proposed to measure up to 210
chemicals in human tissues as staff and other resources permitted. These
chemicals include metals such as mercury, which at high levels may damage
the brain, kidneys, and developing fetus; polyaromatic hydrocarbons (a group
of compounds found in sources such as foods that have been grilled); and
volatile organic compounds, such as benzene. At the time of our review, a
CDC official indicated that resources allowed them to include about 74
chemicals for 1999 and 2000. The estimated marginal costs for the
environmental exposure-related components of the NHANES 1999 survey were
about $5 million.
EPA's National Human Exposure Assessment Survey
To expand upon and replace its National Human Adipose Tissue Survey
(NHATS)--a tissue monitoring program, which ended in 1992--EPA
initiated in 1993 pilot surveys for NHEXAS in three regions of the country.7
A goal of the NHEXAS pilots is to obtain knowledge on the population's
distribution of total exposure to several classes of chemicals and to test
the feasibility of collecting representative survey data on people's total
exposures. NHATS focused on monitoring human fat tissues for persistent
organochlorine pesticides and polychlorinated biphenyls (PCB); NHEXAS has
broadened this focus in two ways. First, in addition to measuring chemical
levels in samples such as blood or urine, the NHEXAS pilot surveys included
measurements of chemicals in air, foods and beverages, water, and dust in
individuals' personal external and internal environments. To conduct these
measurements, the pilot surveys used tools such as questionnaires, activity
diaries, air-monitoring badges worn by the individual or other
air-monitoring devices, and tap and drinking water and food samples. Such
data are important for purposes such as identifying the most important
sources or routes of exposure and for taking actions to reduce or prevent
exposures. Second, the NHEXAS pilot surveys included more types of chemicals
than pesticides, such as lead and other heavy metals. The NHEXAS pilots,
however, included fewer chemicals than its predecessor--which measured about
130 pesticides and PCBs in human fat tissue--in part because monitoring
levels of any given chemical in personal environments and in human tissues
requires significantly more laboratory measurements for the same chemical.
EPA's NHEXAS pilot surveys, which have tested biological samples from about
460 participants, have collectively measured up to 46 chemicals, including
pesticides, heavy metals, and volatile organic compounds in blood, urine, or
hair. Once data from these pilot surveys have been further analyzed, EPA
intends to assess the feasibility and cost of conducting a national effort
to collect total exposure data. To date, EPA has invested about $20 million
to support the pilot surveys. Very preliminary estimates by EPA for a
national survey range from $20 million to $30 million per year over 10 years
or more.
National Institute of Environmental Health Sciences' Human Exposure
Initiative
In 1996, NIEHS began an initiative to collect human exposure data. This
initiative was started as a collaboration between NIEHS and CDC to improve
understanding of human exposures to hormonally active agents--also called
"environmental endocrine disrupters"--for the national
population.8 The effort was intended to build upon the chemical monitoring
in NHANES by supporting the development of laboratory methods and
measurement of previously unmeasured chemicals in human tissues collected
from NHANES and other studies. NIEHS and CDC signed an interagency
agreement, under which CDC will develop methods for measuring and will
measure in blood, urine, or both up to 80 chemicals thought to be hormonally
active agents. For this effort, CDC obtained samples of about 200
people--most of whom are from the ongoing sampling of the general population
under NHANES.
In 1999, officials of NIEHS and the National Toxicology Program (NTP)--an
interagency effort to coordinate toxicological research and testing
activities of HHS, which is administratively housed at NIEHS--proposed to
expand upon the initial collaboration and formalized the undertaking as the
Human Exposure Initiative. Specifically, they proposed a broader interagency
effort to quantify human internal exposures to chemicals released into the
environment and workplace. One significant purpose of this effort was to
help prioritize those chemicals and chemical mixtures to be studied by NTP,
recognizing the limited resources available for toxicological testing and
the need for better information to prioritize which chemicals should be
tested. According to NTP officials, although NTP is the nation's largest
federal toxicology testing program, it can initiate only 10 long-term cancer
studies and 10 reproductive studies per year.9 NIEHS provided a list of 131
chemicals it hoped would be measured through this expanded effort. At the
time of our review, however, program officials told us that NIEHS had not
published data from the chemicals CDC had measured under this agreement, and
CDC was developing the laboratory methods needed to measure many of the
chemicals identified by NIEHS as
needed.10 (For more information on NHANES, NHATS, NHEXAS, and NIEHS' Human
Exposure Initiative, see app. II.)
Remains Limited
Despite these expanded efforts, NHANES and the NHEXAS pilot surveys cover
only about 6 percent (or 81) of the 1,456 potentially harmful chemicals in
our review. We compared the chemicals measured by these surveys to eight
selected lists of chemicals of concern.11 Our selection was based, in part,
on our assessment and input from experts that these lists contained
chemicals of higher concern to human health.12 However, the listed chemicals
represent a small portion of those that are regulated or are of potential
public health importance. For example, there are over 7,000 lists of
chemical substances and classes that are regulated under the Toxic
Substances Control Act and the Emergency Planning and Community
Right-to-Know Act.
For those individual lists that we reviewed, the portion of toxic chemicals
measured ranged from 2 percent of chemicals prioritized for safety testing
(based on EPA's findings that the chemicals may present unreasonable risks)
to about 23 percent of chemicals most often found at the nation's Superfund
sites and identified as posing the most significant threat to human health.
See table 1 for each of the lists reviewed and the extent to which NHANES or
the NHEXAS pilots are measuring these chemicals, and appendix I for a
discussion of each list included in our review.
Table 1: Extent to Which Human Exposure Data Are Collected for Potentially
Harmful Chemicals Through NHANES or the NHEXAS Pilot Surveys
Priority chemicals Chemicals measured or
being measured
Description of list Number in Number Percent
list
Chemicals found most often at the
national Superfund sites and of
most potential threat to human 275 62 23%
health
EPA's list of toxics of concern in
air 168 27 16
Chemicals harmful because of their
persistence in the environment,
tendency to bioaccumulate in plant 368 52 14
or animal tissues, and toxicity
Pesticides of potential concern as
listed by EPA's Office of Pesticide
Programs and the U.S. Department of 243 32 13
Agriculture's Pesticide Data
Program
Chemicals that are reported in the
Toxic Release Inventory; are
considered toxic; and are used, 579 50 9
manufactured, treated, transported,
or released into the environment
Chemicals that are known or
probable carcinogens as listed in 234 17 7
HHS' Report on Carcinogensa
Chemicals most in need of testing
under the Toxic Substances Control 476 10 2
Act (Master Testing list)
Note: Our analysis was based on human exposure data collected through NHANES
or the NHEXAS pilot surveys through 2000.
aThe Report on Carcinogens list may also include pharmaceutical agents,
substances of primarily occupational concern, and banned substances.
According to NIEHS officials, this may account for their lower inclusion in
NHANES or the NHEXAS pilots. NIEHS and NTP officials indicated that, in
addition to these chemicals, NTP reports results of its chronic bioassays
for cancer in its technical report series. There are now approximately 500
reports, which collectively include nearly 250 chemicals found to cause
cancer in rodents. Officials indicated that another useful evaluation would
assess the proportion of rodent carcinogens for which human exposure data
are collected and that NTP is planning to conduct such an evaluation.
While many potentially harmful chemicals in these lists are not measured in
the population, NHANES or the NHEXAS pilot surveys contain a greater portion
of chemicals considered of higher priority. Two toxic chemical lists we
reviewed--one ranking chemicals frequently found at Superfund sites and one
ranking selected chemicals compiled by EPA--prioritized chemicals based on
their potential to harm human health. We examined the highest-ranked
chemicals on these lists and found that higher proportions of these
chemicals were or will be measured compared to the overall list. A CDC
laboratory official also indicated CDC was in the process of developing
methods to measure a number of the chemicals on these lists and planned to
measure other chemicals in future efforts if they have adequate resources to
do so.
� Ranking of chemicals frequently found at Superfund sites: Developed by EPA
and HHS' Agency for Toxic Substances and Disease Registry (ATSDR), which
conducts public health assessments or other health investigations for
populations living around national Superfund sites, this list ranks
substances that are most commonly found at Superfund sites and pose the most
significant potential threat to human health due to their known or suspected
toxicity and potential for human exposure. Of the top 40 chemicals on this
list, CDC indicated that 9 were currently being measured in NHANES. CDC
hopes to include an additional 30 of the top 40 in future efforts; 11 of
these 30 chemicals, however, were included in the NHEXAS pilot surveys.
� Ranking of selected toxic chemicals compiled by EPA: These rankings are
based on a chemical's persistence, tendency to accumulate in plants and
animals, and toxicity. CDC indicated 4 of the top 22 chemicals on this list
based on their health hazard13 were currently being measured in NHANES. CDC
hopes to include the remaining 18 in future efforts; 6 of the 18 chemicals
were included in the NHEXAS pilot surveys.
In recent years, federal agencies have been charged with identifying whether
certain populations--including minorities, people with low incomes, and
children--disproportionately face greater health risks because they have
greater exposure to environmental hazards.14 Researchers increasingly
recognize that the scarcity of adequate and appropriate data, especially for
exposures and related health effects,
hinders efforts to more systematically identify groups that may be at
risk.15 Lacking such data, past efforts to identify the exposures of certain
demographic groups have often relied on measures of chemical levels in the
surrounding environment. For example, some studies around hazardous waste
sites and industrial plants have shown that minorities and low-income
subpopulations are disproportionately represented within the geographic area
around the sites. Such studies are limited in identifying the actual health
risk because they must make assumptions about how these substitute measures,
such as how close one lives to a hazardous waste site, relate to actual
exposures experienced by people.
To identify groups whose exposure is disproportionately greater than that
experienced by the remainder of the population--and thereby provide more
definitive assessments of whether certain groups potentially face greater
health risks--health officials and researchers might measure exposure levels
for (1) a representative sample and analyze the characteristics of
subpopulations with the highest exposures or (2) a population thought to be
at high risk and compare it to measurements from a reference population.16
We examined the extent to which federal survey data on human exposures
collected to date could be used to assess characteristics of those groups
most exposed. We also examined the extent to which human exposure data was
collected on a population considered to be at higher risk--specifically,
those living around national priority hazardous waste sites. In each effort,
the information collected has been limited, as discussed below.
Sampling Not Sufficient to Identify Many Highly Exposed Groups
Representative sampling is required to identify at-risk subpopulations in a
non-biased way--that is, without presupposing that a certain group is at
higher risk. The sample must also be large enough to ensure highly exposed
subpopulations can be objectively identified.17 For nearly all chemicals
except lead, however, past federal collection of human exposure data in
NHANES and the NHEXAS pilot surveys has been insufficient to identify
whether disproportionate exposures are occurring in many demographic groups.
In the case of NHANES, the sample is generally drawn to reflect the national
population as a whole.18 Consequently, the sample of the group of interest
may be too small to draw meaningful conclusions about characteristics, such
as exposures, of the group. In the past, most NHANES exposure measurements
were conducted among non-randomly-selected samples and from only a portion
of the surveyed participants, thus limiting the ability to identify highly
exposed groups. Lead was an exception. Data for blood lead levels in
children have been the most comprehensively collected, and certain
characteristics have been clearly associated with a higher prevalence of
blood lead levels. EPA has concluded that the evidence is unambiguous:
children of color have a higher prevalence of elevated blood lead levels
than white children do, and children in lower- income families have a higher
prevalence than children in higher income families. See table 2 for the most
recent NHANES analysis.
Table 2: Prevalence of Elevated Blood Lead Levels in Children Ages 1 Through
5, by Selected Demographic Characteristics (NHANES, 1991 Through 1994)
Percentage with elevated
Characteristic of children in sample
blood lead levels
Race/ethnicity
Black, non-Hispanic 11.2%
Mexican-American 4.0
White, non-Hispanic 2.3
Income level
Low 8.0
Middle 1.9
High 1.0
Age group
1 through 2 5.9
3 through 5 3.5
Total ages 1 through 5 4.4%
Source: CDC, "Update: Blood Lead Levels--United States, 1991-1994,"
Morbidity and Mortality Weekly Report, Vol. 46, No. 7 (1997), pp. 141-5.
CDC officials told us that representative data, such as that collected for
lead, would be collected for a larger number of chemicals starting in 1999.
However, CDC plans indicated that for most chemicals monitored, only a
portion of NHANES survey participants--generally one-third or fewer,
depending on the type of chemical--would be tested. For some chemicals, only
certain groups thought to be at higher risk may be tested. For example,
NHANES will include measurement of certain persistent pesticides known as
organochlorines in one-third of the survey participants ages 12 through 19.
Children under 12 will not be assessed.19 CDC officials indicated that
people over 19 may be assessed if adequate resources are available to do so.
Although most organochlorines are banned in the United States, some are
still used in home and garden products, such as products for treating lice
and controlling agricultural and structural pests and flame
retardants used in synthetic fabrics.20 NHANES data from a one-third
subsample will be useful for establishing reference ranges within the
population and illuminating exposure levels nationally; they will also be
useful for identifying exposures of broad demographic groups, such as males
and females. But these data are not enough to enable researchers to assess
exposure levels of or characterize many potentially at-risk groups, such as
the exposures of inner-city children in low-income families.21 According to
a CDC laboratory official, targeted studies should be considered for groups
that represent a small portion of the population.
Similarly, the NHEXAS pilot surveys included representative samples of
participants in the three geographic locations covered. However, because of
the smaller sample sizes, the work to date has also been too limited for
much analysis of at-risk populations.22 The pilot surveys included
biological measurements for about 200 people in six Midwestern states, about
180 people in Arizona,23 and about 80 people in Baltimore.
Federal Efforts to Identify Communities of Concern Valuable, but Human
Exposure Data Are Limited
A second method to identify a subpopulation disproportionately at risk of
adverse health effects is to compare exposure levels for a group thought to
be at high risk with baseline measurements from a reference population.24
This method can be used to determine, for example, the extent to which
people in a neighborhood, community, or geographic location are exposed
relative to others. In cases where exposure levels have been identified as
high compared to reference populations but potential health effects
associated with those levels have not been researched, public health actions
can help prevent further or increasing exposures, and these groups can be
assessed for any subsequent health outcomes.
One federal effort, conducted by ATSDR, analyzes risks faced by communities
near hazardous waste sites. ATSDR estimates that 12.5 million people live
within 1 mile of the nation's 1,300 Superfund sites. The agency can collect
biological samples through exposure investigations as part of the public
health assessment process or in response to requests from the public.25
ATSDR officials said that human exposure data collected at Superfund sites
have been useful in deciding on actions such as stopping or reducing
exposures, relocating residents, referring residents for medical follow-up,
reducing community anxiety, influencing priorities on site-specific
clean-up, making referrals to researchers for assessing health links, and
educating community and other health providers. As evidence, they pointed to
the conclusions of an expert review panel, which stated in March 1997 that
human exposure data were as important to exposure investigations and public
health assessments as environmental monitoring results at the sites of
concern.26 However, the number of investigations that included human
exposure data has been limited. Between 1995 and July 1999, ATSDR had
gathered biological samples at only about 47 of the more than 1,300
Superfund sites. At least 34 of these investigations detected contaminants
in people and 16 found elevated levels.
Other federally conducted efforts designed to monitor or collect data on the
exposures of populations within selected communities or geographic regions
have also been infrequent.27 One such regional-scale effort under way is
collecting data on exposures within selected communities along the border
between Texas and Mexico. Officials from Mexico and federal and state
agencies in the United States are comparing exposures of people in the
border area with those in areas away from the border. Another study examined
the exposures of people along the Arizona border compared to the exposures
of people elsewhere in the state. This study collected environmental samples
for pesticides, metals, and volatile organic chemicals. Blood and urine
samples were also tested to relate the environmental measurements to the
measurements in human tissues for these chemicals.
Investigations but Do Not Often Include Them
Most state officials who we surveyed highly valued human exposure data.
However, most could not include it in their exposure-related health studies,
investigations of concerns such as disease clusters, or surveillance
efforts. Almost half of the officials responding to our survey estimated
that they had participated in 10 or more exposure-related studies or
investigations since 1996, with about 16 percent estimating they
participated in 50 or more. However, about half of officials indicated they
could seldom if ever collect exposure data through human samples in their
efforts. When data were developed, officials listed five main uses: (1)
environmental health epidemiologic studies, (2) surveillance of diseases or
conditions with suspected environmental causes, (3) investigations of
citizen concerns, (4) planned or accidental chemical releases, and (5)
disease clusters (see table 3).28 State officials we spoke with noted that
human exposure data are often the most valid and persuasive evidence
available to demonstrate whether, and to what extent, exposure has occurred
or changed over time. In highly charged situations, where community trust
has eroded, such data may be the only evidence acceptable to area residents.
Table 3: Examples of How State Officials Use Human Exposure Data
Purpose Example
Using blood and urine samples from
people who ate sport fish and were
concerned about undue exposure to
dioxins, pesticides, and other
chemicals, health officials
Environmental health epidemiologic determined these people had exposure
studies to some chemicals from 2 to 10 times
higher than levels in a reference
population. Based on these results,
officials will focus a larger health
effects study on exposure to those
chemicals.
Virtually all states collect
Surveillance of diseases or information on blood lead levels in
conditions with suspected children to monitor and prevent lead
environmental causes poisoning. Some also monitor exposure
to pesticides and other chemicals
such as mercury and arsenic.
Health officials used human tissue
measurements and citizens' reports of
illnesses to demonstrate that the
combined effect of chemicals released
into the environment posed a health
Investigation of citizen concerns hazard severe enough to warrant
evacuating nearby residents. State
and federal officials subsequently
closed a manufacturing plant because
of the harmful health effects of its
chemical releases.
Officials in nine states asked CDC to
test tissue samples from almost
17,000 individuals thought to have
been exposed to methyl parathion, a
deadly pesticide. CDC's ability to
measure the pesticide in human tissue
and compare exposures across states
was critical to identifying
individuals with high exposures and
Investigation of planned or houses most in need of clean-up.
accidental chemical releases Because relocating residents and
removing the pesticide from homes
cost up to $250,000 per household,
the exposure data helped officials
avoid spending limited funds on
houses that did not pose a health
risk to the people living in them.
One state official said the exposure
results reduced the number of houses
needing pesticide removal from
hundreds to fewer than 10.
State health officials reviewed data
on individual cases of cancer in one
community and for the entire state.
When available data on known risk
factors did not account for the
increased incidence of breast cancer,
officials began a more detailed study
that included human tissue analysis.
Investigation of disease clusters Blood samples were obtained from
women before and after treatment
began and from women in a control
group. Results will be compared to
reference range data developed by
CDC. One goal of such studies is to
help identify environmental factors
that contribute to breast cancer
risk.
While mercury, arsenic, and pesticides were most often reported as being
studied in human samples, some state officials reported using human exposure
data for chemicals that CDC has since 1991 developed methods to measure. For
example, about 15 percent of officials conducted studies of human exposure
to volatile organic compounds, and almost 30 percent reported studies of
exposure to PCBs using data from tissue analysis.
Regardless of whether state officials had collected or used human exposure
data in the past 4 years, about 90 percent of those officials responding to
our survey said human exposure data from tissue samples was extremely or
very important for addressing environmental health concerns. Despite the
perceived value of such data, almost two-thirds of officials said they could
include human exposure data in fewer than half of the exposure-related
studies, investigations, and surveillance efforts where they considered it
important. More than one-third said they seldom could include such data.
Several state health and laboratory officials whom we interviewed expressed
frustration at the missed opportunities for collecting biological samples as
part of their studies and investigations for reasons such as limited
laboratory capacity. For example, health officials in one state could not
examine the role played by methyl t-butyl ether (MTBE)--an additive designed
to promote more efficient burning of gasoline--in a major respiratory
disease outbreak because state staff lacked the expertise and CDC staff
lacked the time to conduct the needed tests. In 1995, after MTBE was added
to gasoline and thousands of citizens reported becoming ill, state officials
wanted to measure MTBE or its by-products in blood from samples of
individuals with and without symptoms to determine whether MTBE exposure
might be the cause or a contributing factor. Objective measures of
individual exposure might have allowed public health officials to
conclusively demonstrate or rule out a link between the outbreak and
exposure, something that was not possible with environmental data and
epidemiologic surveys. The chemicals officials most often cited as wanting
to study using human exposure data but could not were pesticides and
volatile organic compounds.
Strategic Planning and Coordination
As part of our survey and interviews, we asked public health experts and
state and federal officials to identify barriers they considered significant
to their efforts to collect and use human exposure data. Officials cited two
primary barriers: the lack of laboratory capacity or methods to analyze
tissue samples and the lack of information to help set exposure test results
in context. Addressing these barriers takes time and resources. In that
regard, we identified a third barrier to more effective use of existing
resources: HHS and EPA lack a long-term strategic plan to address
infrastructure and science barriers, coordinate efforts to meet federal and
state needs, and address the many questions about how to set priorities
given their limited resources.
State officials frequently said insufficient laboratory capacity in their
states and at the federal level hindered their ability to obtain human
exposure data in cases where they thought such data were important. Over
half of the officials said their states lacked sufficient numbers of trained
laboratory staff, sufficient laboratory capacity to analyze samples, or
sufficient laboratory equipment. Many officials attribute such capacity
limitations to funding constraints because tissue analyses can be
time-consuming and expensive to perform. For example, according to a CDC
official, each test to measure dioxins in a sample requires (1) a laboratory
free from chemicals that could compromise test results, (2) specialized
equipment that costs about $500,000, and (3) highly trained and experienced
staff to complete. Officials of a professional organization representing
public health laboratories told us that, although many state laboratories
perceive they have a role in conducting tests to detect toxic substances in
humans, very few currently have such capacity.29
State and federal officials we interviewed told us that because few state
laboratories have the necessary equipment and expertise, they often rely on
CDC's environmental health laboratory staff to analyze tissue samples. Given
the specialized laboratory requirements, CDC's environmental health
laboratory is generally considered the best-suited to analyze tissue samples
for a range of chemicals and has, in fact, developed many of the methods to
do so, according to federal and state officials. CDC's laboratory performs
measurements for most federal and many state efforts to gather human
exposure data. Many officials said CDC's laboratory capacity is essential to
their efforts and needs to expand to meet growing needs. A few state
officials said CDC's laboratory consistently returned test results when
people's lives were at risk but was less able to help states assess health
risks more generally. An official in one state said that, while CDC's
assistance is invaluable, the state's laboratory capacity allowed public
health officials to obtain human exposure data and investigate citizen's
concerns more frequently than they could if they had to rely soley on CDC's
laboratory capacity.
Another significant issue is the lack of analytical laboratory methods to
measure chemicals of concern. Despite advances over the past 2 decades in
analytic chemistry and molecular biology, laboratory methods have not been
developed to measure about 88 percent of the 1,456 chemicals in our review,
according to information provided by CDC and EPA officials. Although
laboratory staff at CDC have quickly applied scientific and technological
advances to develop new and more efficient laboratory methods, they are
concerned about the lack of methods to test a single human sample for
several related toxics. For example, a method exists to measure arsenic in
blood but not to measure arsenic and other heavy metals at the same time.
Such methods make more efficient use of the samples that are gathered and
greatly reduce the time and money needed to test large numbers of samples.
While CDC's laboratory continuously develops new chemical testing methods,
current resources limit the number to about 10 annually.
Even when analytical methods exist, efforts to gather human exposure data
are sometimes limited by problems with the methods used to gather the
samples. This is especially true for young children, a group thought to be
particularly susceptible to harmful effects from exposure. In some cases,
existing laboratory methods require sample volumes that can only be obtained
through invasive techniques. That is, blood samples must be obtained by
puncturing a vein rather than by pricking a finger. Many people will not
allow their children to participate in studies that require such techniques.
Similarly, urine samples can be difficult to obtain from children who wear
diapers. For example, substances in the diapers can compromise test results.
To help interpret the results of laboratory analysis and determine what
actions, if any, are needed to protect the public's health, state and
federal officials cited the need for two types of context-setting data:
comparative (or reference range) information that shows exposure levels
among the general population and research that links exposure to adverse
health effects. At the state level, where many of the specific actions
regarding at-risk situations are taken, almost three-fourths of responding
officials cited the lack of such information as a problem.
State officials said that reference range data, when available, allowed them
to determine whether exposures are sufficiently high to merit action to
reduce or prevent further exposure. For example, in one state, public health
officials, with help from CDC, responded to citizens' reports of foul odors
from leaking tanks at a waste cleanup site by gathering and analyzing blood
samples from those living nearby. CDC's analysis of the blood samples showed
that residents near the site had exposure levels at the high end of a
CDC-developed reference range. State and federal officials ordered the
contractor to move the cleanup operations to another location. Over 60
percent of state officials responding to our survey said the lack of
reference range data prevented them from using human exposure data in their
work. State officials said the problem for research about adverse health
effects was similar. Much of the data linking exposure to health effects
concerns high-level occupational exposures or higher doses administered to
laboratory animals. Consequently, translating the results of such research
to lower-level exposures of people and determining how best to advise people
about potential effects is problematic.
Federal health officials and researchers also cited a need for both types of
information in their investigations, particularly for federally supported
work in specific geographic areas. ATSDR officials said the lack of
reference ranges was a particular reason they could not generate human
exposure data more often in public health assessments and exposure
investigations. When data allow officials to put exposure into context,
concerns can be investigated and addressed. For example, in one community,
where citizens were concerned about exposure to dioxins from nearby chemical
manufacturing plants, ATSDR officials had CDC's laboratory analyze blood
samples and found that some residents had levels of several dioxins above
the highest levels in a CDC-ATSDR-developed reference range. In response,
ATSDR helped residents obtain assistance from medical professionals expert
in dioxins and, working with state and federal environmental agencies, began
environmental testing to locate the exposure source.
Coordination
The barriers outlined above present daunting challenges to state and federal
agencies. The number of chemicals that remain to be investigated and the
kinds of information needed are substantial, the research is often
expensive, and progress is often slow. At the same time, the level of
resources available for dealing with the issue is limited, and
responsibilities are fragmented among many state and federal agencies. Many
studies have pointed to the need for better coordination. While HHS and EPA
efforts have been coordinated through, for example, participation on
advisory committees and the use of CDC's laboratory for performing the
actual measurements, such coordination falls short of what is needed for
long-term planning. This need is illustrated by the growing convergence of
interest in the planned expansions of NHANES and NHEXAS. To ensure as much
progress as possible with available resources, HHS and EPA need a strategic
planning effort that reflects a clear set of priorities, a framework for
coordinating data collection and reporting efforts, and a tie to performance
goals.
Agreement About Need for Better Planning and Coordination of Efforts Is
Widespread
In 1991, NRC reported that "although a successful monitoring program must be
highly relevant to regulatory needs, it could and should serve a wide range
of client programs and must not be dominated by any one of them." NRC
reported that the approaches of EPA, CDC, and ATSDR are each important in
the identification and control of environmental hazards to human health and
that coordination among the programs would enhance federal monitoring
efforts and benefit researchers, health professionals, and the public.30
Officials and experts agree that interagency interaction is needed to take
advantage of all approaches and information available to develop the most
cost-effective, least burdensome approach for collecting needed exposure
data. Towards this end, HHS agencies and EPA have at various times attempted
to collaborate in their respective exposure monitoring efforts. For example,
EPA solicited broad interagency input into the design of NHEXAS and
established interagency agreements with CDC and others to assist in
performing laboratory measurements, quality control, and other support
functions. Also through interagency agreements, CDC has broadened the
exposure monitoring component of NHANES to incorporate the needs of EPA
researchers.
Outside reviews and involved researchers and officials indicate that even
with recent efforts, coordination has fallen short in ensuring adequate
interaction and linkages between agencies. For example, EPA's scientific
advisers reviewed the NHEXAS pilot surveys and concluded that, while NHEXAS
was an excellent project and highly relevant for providing needed
information, a strategic plan was needed for follow-up studies. They also
urged that EPA link NHEXAS exposure data with biological data from NHANES,
where possible, and develop a more collaborative process for gathering input
for chemical selection. Attendees at a September 1999 NIEHS conference on
the Role of Human Exposure Assessment in the Prevention of Environmental
Disease also called for a coordinated interagency effort in assessing human
exposure.31 One theme and recommendation from the discussions was the need
to bridge scientific disciplines and agency missions to address knowledge
gaps in assessing human exposure.
State officials and others have also indicated that better linkages and
partnering are needed between federal, state, and local agencies. For
example, an official of the Association of Public Health Laboratories told
us that one way to improve states' involvement in a national exposure
monitoring program would be to further their capability to assess levels of
toxic chemicals in their own populations relative to national levels. This
would require, in this official's view, the transfer of new monitoring
technology to state public health laboratories, along with the resources
necessary to support that technology. Improved capacity at the state level
would allow federal laboratories to concentrate on developing more and
faster analytical methods for measuring chemicals in tissues and on
responding to crisis situations. Other experts have also called for better
linkages between federal efforts and communities and community concerns. For
example, the NHEXAS reviewers recommended that EPA improve communication
between NHEXAS investigators and state and local health officials. Another
theme of the conference on human exposure assessment was that efforts to
assess human exposure be in line with public health goals and community
concerns.
Efforts
The challenges federal and state agencies face in setting priorities for
which chemicals to assess in their individual programs likely contribute to
the difficulties they have in collaborating with one another. The expense of
conducting exposure measurements in ongoing surveys--especially for the
number of samples required to establish national or regional trends and
levels--necessitates that priorities be set. However, agreeing on
priorities--or even agreeing on the process for setting priorities--is
challenging and resource-intensive. For example, to identify chemicals to
measure in NHEXAS, EPA undertook an extensive selection process, soliciting
input from regional and program offices.32 EPA's scientific advisers, while
supportive of the program, cited the criteria for selecting target chemicals
as a weakness. NHANES is even less formal in this regard, with no documented
priority-setting process for chemicals to be measured. Chemicals measured
are largely determined by CDC's laboratory scientists based on such factors
as the availability of analytical methods for measuring the chemical and the
laboratory's capacity to perform the measurements.33 According to a CDC
official, CDC's limited staff and laboratory resources cannot develop the
administrative infrastructure to establish a scientific review process for
selecting priority chemicals.
Another challenge in setting priorities, according to some officials, is the
appropriate balance between gathering exposure information on chemicals
about which little is known and gathering information on those already
considered to be toxic. NHANES and NHEXAS, for example, focus largely on
chemicals that are considered to be toxic at some level. By contrast, the
National Toxicology Program's Human Exposure Initiative is intended to help
set priorities for chemical toxicological testing and might gather baseline
information on chemicals and chemical mixtures occurring in the population
that are not necessarily already known as harmful.
Officials we interviewed raised many other concerns that would need to be
addressed when trying to coordinate efforts among multiple federal and state
agencies and programs:
� For what specific purpose(s) will these data be collected?
� What chemicals should be measured, in what order, how frequently, and in
what specific tissues?34
� What chemicals should be measured concurrently with or only through
personal environmental measurements?
� What is the best way to identify populations that might be at higher risk
of exposure?
� What chemicals should be monitored in humans nationally, versus regionally
or locally?35
� How can exposure data be coupled with our increasing knowledge about the
effect genetic factors have on risk from exposure to improve the
understanding about an individual's risk from chemical contaminants?
� What role should state agencies have in conducting human exposure
measurements and in planning federal efforts?
The fragmentation of responsibilities and efforts for assessing human
exposure reflect larger issues in the fragmentation of responsibility for
environmental health. For over a decade, a number of studies have pointed to
the need for improved coordination between regulatory and health agencies
(see table 4).
Table 4: Examples of Reports Calling for Coordination in Environmental
Health
Report Description
Called for the federal government to
facilitate stronger ties between
environmental protection and public
health agencies, perhaps by
Environmental Health Data Needs: An strengthening organizational links
Action Plan for Federal Public and coordinating funding for federal
Health Agencies (Public Health (EPA and HHS) programs. Also
Foundation, 1997) indicated that priority environmental
health information needs included
more complete exposure data,
including laboratory data such as
biological measurements.
Found that progress in understanding
Burke, Shalauta, and Tran, The the relationship between human health
Environmental Web: Impact of Federal and the environment will require,
Statutes on State Environmental among other actions, improved
Health and Protection (Public Health cooperation between the many health
Service, Jan. 1995) and environmental agencies at the
federal, state, and local levels.
Reported that although agencies are
expanding their research efforts, few
incentives exist for them to
collaborate, and the lack of
Researching Health Risks (Office of collaboration can only hinder
Technology Assessment, 1993) progress in applying newly developed
techniques and knowledge to
understanding the potential links
between exposure and adverse health
effects.
Reported that linkage of
environmental and health data to
The Potential for Linking investigate possible connections
Environmental and Health Data between exposure and adverse health
(National Governors' Association, effects cannot occur without
1990) interagency communication and
cooperation, which rarely evolves
naturally.
Found that separating environmental
health from public health programs
The Future of Public Health impeded desirable coordination and
(Institute of Medicine, 1988) could limit the depth of analyses
given to the health implications of
environmental hazards.
Potential for Convergence of Effort Is Increasing
The importance of planning and coordination is magnified by the possible
overlap in current plans to expand human exposure monitoring efforts. This
potential can be seen in HHS' and EPA's plans for NHANES and proposed
expansions of the NHEXAS pilots. Although nearly two-thirds of the chemicals
measured in the NHEXAS pilot surveys are currently measured or planned for
NHANES, the two efforts have taken differing approaches in the past to
monitoring the population's exposure to these chemicals.36 The NHEXAS pilots
have focused on "total" exposure, which entailed measurements in human
tissues, water, air, food, dust, and other potential sources in
participants' living environments, and data-gathering has focused on three
selected regions of the country. Total exposure measurements can help
identify those sources that most contribute to exposure--a critical part of
determining how to take action to reduce or
prevent exposures. However, measuring total exposure requires several types
of laboratory measurements and is thus more expensive. By contrast, NHANES
has focused its exposure monitoring on human biological measurements and on
a sample that is generally representative of the nation as a whole.
Biological monitoring data demonstrate exposure from all sources, but
determining exposure sources usually requires additional environmental
measurements. Other than the few chemicals it covered, NHANES has
historically been considered an awkward vehicle for including exposure
monitoring--in large part because of its wide range of competing goals and
lack of a primary commitment to monitoring tissues for exposures.
Changes to the 1999 NHANES, such as the following, show a greater emphasis
in environmental health. These changes along with EPA's plans to expand
NHEXAS suggest a convergence of the two approaches and a growing and
overlapping interest among agencies in exposure measurement and monitoring.
� NHANES now has a goal of monitoring exposures. Starting with NHANES 1999,
CDC formalized its commitment to monitoring trends in the nation's
environmental exposures by establishing this as a stated goal of NHANES.37
In line with this goal, CDC's laboratory plans to issue
this year a "National Exposure Report Card" using NHANES samples.38 This
goal is similar to EPA's goal as proposed for NHEXAS' follow-up survey--to
document the status and trends of the national distributions of human
exposure to potentially high-risk chemicals.
� NHANES will include selected environmental measurements. Starting with
NHANES 1999, environmental measurements, such as contaminant levels in water
and house dust, and levels measured through personal air monitors worn by
participants will be included in the survey to help identify potential
sources of exposure.39
� NHANES will be conducted continuously rather than periodically, allowing
for more flexibility in the measurements it includes. According to CDC
officials, the new annual sampling design will enable them to include
emerging and changing priorities in the data collected through the survey
and thus allow for a broader collection of data than in previous surveys,
including exposure and measurements in people's personal environments.
Other planned changes to NHANES and NHEXAS also indicate a growing overlap
in approaches and interests. For example, pending analysis and evaluation of
its pilot surveys, EPA is proposing to expand NHEXAS beyond the regional
focus of its pilot to include a nationally representative sample similar to
the framework of NHANES. Also, both CDC and EPA would like to eventually
include a component in NHANES and NHEXAS to monitor special populations.
EPA's proposed expansion of NHEXAS would eventually include "special
studies" to examine high-end exposures in more detail and with greater
precision. Small populations for further study would be identified through
the national survey. CDC also plans to add a component to NHANES that will
gather selected NHANES health and nutrition data, possibly including
exposure measurements, on specific subpopulations in geographic areas of
interest or among specific racial or ethnic minority populations. This
effort to add a subpopulation component to NHANES was initiated in response
to the needs of state health officials and others for local level data.
Part of the difficulty in collaborating and in planning human exposure
monitoring efforts to meet longer-term needs may also arise from issues of
sporadic funding and resources to support these efforts. As compared to the
hundreds of millions spent on monitoring contaminants in environmental
media, we estimate that less than $7 million was spent collectively by CDC
(including ATSDR) and EPA on their respective human exposure efforts in
1999.40
Neither CDC nor EPA has provided a dedicated funding stream for their
exposure measurement efforts. Funding for efforts has, to a large extent,
depended on priorities established year to year. For example, funding for
the exposure and other environmental components of NHANES depends to some
extent on the interests of other federal agencies and their willingness to
pay for related data gathering and analysis.41 CDC estimated it would spend
about $4.7 million for laboratory measurements and laboratory staff costs in
1999 for NHANES-related exposure measurements such as lead, mercury,
cotinine, heavy metals, pesticides, volatile organic compounds, and other
chemical classes. Interagency agreements document the receipt of about $1.2
million from collaborators for some of those laboratory measurements. If
other agencies do not pay CDC to conduct laboratory tests--with the
exception of some "core" measurements, such as lead--CDC performs tests as
time and laboratory resources allow. For example, although CDC initially
proposed for the survey starting in 1999 to measure up to 210 chemicals in
tissues of a subset of NHANES survey participants, CDC officials indicated
that those chemicals could be measured only as resources allowed.42 At the
time of our review, a CDC laboratory official indicated that resources might
allow them to include about 74 chemicals in 1999 and 2000.
EPA's commitment to funding NHEXAS also remains uncertain. EPA officials
estimated that approximately $20 million was spent on NHEXAS from 1993
through 1999--with a decreasing amount designated to the project in 1999 and
2000. While EPA's independent scientific advisers commended the design for
NHEXAS and said it could be the basis for an effective national program,
they expressed concerns about the limited resources allocated to analyze the
data gathered in the pilot projects.43 At a national level, EPA has
dedicated approximately three full-time positions to evaluate the data from
the NHEXAS pilots and design future expansions.
Better Linkages to Program Goals and Performance Monitoring Needed
The Government Performance and Results Act of 1993 (Results Act) provides
federal agencies a structured framework to coordinate efforts in
crosscutting programs when agency missions overlap. The Results Act requires
federal agencies, as part of their mandated responsibilities, to prepare
annual performance plans that discuss agency goals and performance measures.
Past reviews have shown that EPA, HHS, and other federal agencies have not
fully used the Results Act planning process to explain how each would
coordinate crosscutting efforts with other agencies. Few agency plans
attempt the challenging task of discussing planned strategies for
coordination and establishing complementary performance goals and common or
complementary performance measures.
A major weakness of EPA's fiscal year 2000 Annual Performance Plan was the
lack of sufficient detail describing crosscutting goals and activities or
how EPA planned to coordinate with other federal agencies on related
strategic or performance goals.44 For example, under its plan's "safe food"
objective, EPA discusses coordinating with HHS and other agencies to reduce
health risks from pesticides. However, it did not outline specific projects
and strategies, responsibilities, and products that must be coordinated for
EPA to accomplish its goals. Similarly, HHS' performance plan lacked details
regarding how crosscutting activities and goals would be coordinated with
other agencies.
In their fiscal year 2001 performance plans, EPA and CDC make limited use of
human exposure data to measure or validate performance, and neither agency
describes how data collection efforts relate to complementary goals of other
federal agencies. For example, EPA and CDC have the common goal of reducing
childhood lead poisoning, but only CDC uses data on blood lead levels to
validate progress toward this goal. Although EPA has goals that are clearly
related to reducing human exposure to other toxic chemicals, the human
exposure data collected by EPA and CDC have largely not been linked with or
used to measure progress. Such data show potential for helping elucidate
federal progress in environmental efforts, but EPA has not yet acted to
fully realize such potential. For example, NHEXAS data are used to help
assess children's exposure to pesticides. However, a related goal to reduce
public exposure to pesticides does not use human exposure data; instead, it
relies on the number of activities to educate agricultural workers and the
public. The effectiveness of these efforts could be assessed, in part,
through measured reductions in actual human exposure to specific pesticides.
During 1999, CDC maintained a goal to develop methods to measure toxic
substances in humans and added a goal to measure and report on human
exposure to toxic substances. However, neither goal discusses how CDC will
coordinate with EPA and other federal programs in meeting these goals and
ensuring that newly developed methods and measured substances meet priority
data needs.
Successful Models for Planning and Coordination Point to the Need for
High-Level Mandate, Process for Inclusion, and Mechanism for Reporting
Program officials at HHS and EPA told us in early 2000 that they were
discussing the merits of establishing a new interagency program in human
exposure monitoring.45 At the time of our review, the proposal was in early
stages of discussion and officials had not clarified how a new program would
consider states' information needs, differ from or relate to NHANES and the
NHEXAS pilot surveys, or resolve past issues about differing agency goals
and priorities.
Several experts and agency officials have pointed to successful models of
interagency collaboration in environmental health issues that could help
shape an HHS-EPA interagency effort. One such model is the collaboration on
children's environmental health issues. In this case, Executive Order 13045,
signed by the President on April 21, 1997, established a Task Force on
Environmental Health Risks and Safety Risks to Children to develop and
recommend federal strategies for children's environmental health and safety.
Among the elements that have been cited as contributing to success were a
clear mandate to collaborate and a process to respond to the input and data
needs of different stakeholders. According to involved officials, a
high-level interagency work group has worked closely to address its charges.
These charges include developing general policy and annual priorities; a
coordinated federal research agenda; recommendations for partnerships among
federal, state, local, and tribal governments and the private, academic, and
nonprofit sectors; and identifying high-priority initiatives to advance
protection of children's environmental health.46
A second model with a top-down mandate and a process to respond to
stakeholders is NTP, established in 1978 as an HHS-wide effort to provide
regulatory and research agencies needed information about potentially toxic
and hazardous chemicals nationwide and to strengthen the science base in
toxicology. According to officials, part of NTP's success in fostering
collaboration are an inclusive executive committee and an established
process for decisionmaking. The NTP Executive Committee, which provides
policy oversight of NTP, includes agencies outside of HHS, such as EPA and
the Consumer Product Safety Commission. The NTP Executive Committee also
serves as a decisionmaking body, in that members cast votes on key issues,
such as prioritization of chemicals for study and for
listing in NTP's Report on Carcinogens.47 Involved officials believe the
voting requirement helps move key issues forward and provides an effective
means of resolving disagreements. NTP also has an inclusive process for
identifying chemicals to be considered by the Executive
Committee. NTP's chemical testing nominations are solicited from sources in
academia, federal and state regulatory and health agencies, industry, and
unions, as well as environmental groups and the general public.
Several officials indicated that reports on exposures in the national
population to toxic chemicals are needed to help inform policymakers,
researchers, and the public. Specifically, such reports can help identify
serious human health risks, help officials link exposures to sources,
determine appropriate interventions to help reduce these risks, and document
the effectiveness of interventions in reducing exposures. Moreover, agencies
could use such reports to validate or measure progress in meeting goals
established under the Results Act. A key element of NTP is its biennial
reports. As informational scientific and public health documents, these
reports are not only used by federal and state agencies but are considered
an important medium for informing the public and policymakers on the status
of substances considered likely to be carcinogenic for humans.
The nation has a long way to go in measuring human exposures to potentially
harmful chemicals. While federal efforts are increasingly covering chemicals
of potential concern, there are substantial gaps in current information on
exposure levels, the health risks that result, and those who may be most at
risk. Recent advances in laboratory technology show promise for improving
the collection and analysis of some of the information needed to understand
and measure human exposures. However, a more long-term and concerted effort
to address infrastructure and scientific limitations in measuring exposure
will be required if substantive progress is to be made. Applying and
continually improving upon these advances to cover an increasing number of
chemicals and issues will require both time and resources. CDC's laboratory
to date has been able to meet many demands for human exposure data for
federal and state measurement and monitoring efforts. However, its capacity,
given current resources, will continue to limit progress to develop new
methods and include more people and chemicals in federal and state efforts.
Federal agencies are currently planning whether and how they can expand
existing programs to meet the significant needs for human exposure data.
Collaboration in such planning is essential, because agencies have different
capacities and skills, and separate attempts have fallen short of supporting
the large efforts that are needed. So far, no clear strategy has emerged for
how to carry out this major task, particularly given the growing and
overlapping interests among many agencies for understanding and measuring
human exposures to potentially harmful chemicals. In our view, developing
such a strategy is a challenging but necessary first step.
In the meantime, state and local health officials must try to understand and
communicate the risks from environmental contaminants to concerned
citizens--a difficult, if not impossible, task when information is
unavailable to help them interpret the risks from the exposures citizens
face in their daily environments. State officials indicate they need more of
the information that is collected through federal efforts to help interpret
those levels faced by citizens in their states. And to collect measurements
for their studies and investigations, state officials are faced with finding
laboratories that have the equipment and capacity to perform the complex
measurements. Federal capacity, largely centered at CDC, cannot meet states'
needs in many situations, and laboratory capacity is lacking in most states.
To help meet the gaps in environmental exposure data at all levels of
government, EPA and the various HHS agencies with environmental health
responsibilities need to work closely together to forge a strategic plan
laying out the necessary next steps for addressing human exposure
information and concerns. In addition to considering states' needs and
capacities for collecting human exposure data, such a plan could
� provide long-term structure to human exposure monitoring as an interagency
effort,
� establish a mechanism for setting program priorities in line with agency
goals and performance measures,
� clarify agency roles and minimize duplication, and
� help agencies share expertise.
Policymakers, agencies, and the public seek many types of information on
exposure trends and levels in the national population as well as for groups
considered potentially at risk of disproportionate exposures. Resolution is
also needed on what information should be reported on national trends and
levels of exposure. A strategic plan could help agencies resolve the many
different informational needs to determine what exposure information should
be reported and how agencies can work together to report such information.
We recommend that the Secretary of HHS and the Administrator of EPA develop
a coordinated federal strategy for the short- and long-term monitoring of
human exposures to potentially toxic chemicals. In developing such a
strategy, the Secretary and the Administrator should assess the need for an
interagency program to collect and report data on human exposures, the
extent current surveys and agency efforts can be used as part of such an
effort, and the funding needs and sources to sustain a viable program for
monitoring human exposures to toxic substances. Such a strategy should
� address individual agency needs and expertise,
� provide a framework for coordinating efforts to gather data needed to
improve understanding of human exposures,
� assess needed federal and state laboratory capacity,
� establish research priorities for laboratory methods development and a
mechanism or process for setting chemical monitoring priorities,
� develop a framework for identifying at-risk populations, and
� consider states' informational needs.
We further recommend that the agencies identify common or complementary
performance goals or measures to reduce, monitor, or develop methods for
measuring human exposures to toxic chemicals. Such goals or measures can be
a basis for structuring and supporting interagency collaborations to collect
and use human exposure data.
As part of this coordinated strategy, we recommend that the Secretary of HHS
and Administrator of EPA periodically publish a report on levels and trends
in the national population of exposures to selected toxic substances.
We provided HHS and EPA an opportunity to comment on a draft of this report.
Both agencies generally concurred with our conclusions and
recommendations--that a long-term coordinated federal strategy was needed
for monitoring human exposures to potentially toxic chemicals and that such
efforts could be linked through common or complementary performance
goals--and indicated that they would work together to implement our
recommendations. (See apps. IV and V, respectively.) HHS and EPA also both
stressed the importance, as discussed in our report, of expanding the scope
of their efforts to monitor and measure human exposures to toxic chemicals
beyond the limited number of chemicals covered today. To support such
expansions, HHS noted the importance of additional resources for improving
laboratory capacity and methods.
HHS and EPA provided several other comments raising points that one or both
agencies consider important to monitoring human exposures to toxic
chemicals. These included the need to (1) coordinate any exposure monitoring
in the general population with monitoring of occupational exposures; (2)
consider adding the monitoring of breast milk in a national program; (3)
depending on the chemical and the purpose for the data collection, consider
measures of human exposure other than the concentration in human tissues for
collection; and (4) consider the option of expanding the scope of NHANES as
a means of improving data needed to identify potentially at-risk subgroups.
We agree that the points raised in these comments are important and that
they should be considered during development of any coordinated federal
strategy.
EPA also said that additional federal partners, including the Departments of
Defense, Transportation, and Energy should participate in developing and
supporting a coordinated federal strategy. We agree that it would be
appropriate to obtain input from all involved and interested agencies. HHS
and EPA also provided a number of clarifying and technical comments, which
we incorporated where appropriate.
We are sending copies of this report to the Honorable Donna E. Shalala,
Secretary of HHS, and the Honorable Carol M. Browner, Administrator, EPA. We
are also sending copies to Jeffrey P. Koplan, Director, CDC, and
Administrator, ATSDR; Ruth Kirschstein, Acting Director, NIH; Kenneth Olden,
Director, NIEHS; Richard J. Jackson, Director, National Center for
Environmental Health; Edward J. Sondik, National Center for Health
Statistics; Norine Noonan, Assistant Administrator for Research and
Development, EPA; and other interested parties. We will make copies
available to others upon request.
If you or your staff have any questions, please contact me at (202)
512-7119. Other major contributors are included in appendix VI.
Janet Heinrich
Associate Director, Health Financing
and Public Health Issues
List of Requesters
The Honorable Nancy Pelosi
House of Representatives
The Honorable Maxine Waters
House of Representatives
The Honorable Eleanor Holmes Norton
House of Representatives
The Honorable Patsy Mink
House of Representatives
The Honorable Anne G. Eshoo
House of Representatives
The Honorable Nydia Velazquez
House of Representatives
The Honorable John Conyers
House of Representatives
The Honorable Louise Slaughter
House of Representatives
The Honorable Henry A. Waxman
House of Representatives
Objectives, Scope, and Methodology
Nine members of the Congress asked us to study the nation's data collected
to assess human exposure to potentially toxic chemicals in the environment.
As agreed with our requesters, we focused our work primarily on efforts to
measure chemical exposures in human tissue samples, such as blood, hair, and
urine. This report discusses (1) the extent to which state and federal
agencies--specifically, HHS and EPA--collect human exposure data on
potentially harmful chemicals, including data to identify at-risk
populations, and (2) the main barriers hindering further progress in such
efforts.
Although laboratory measurements of chemical exposure are only one part of
the data collected to address environmental health concerns, they merit
attention because new technology makes it increasingly easy to measure the
degree to which a chemical has been absorbed into human tissues. Such
measurements are often a more accurate and useful approach to assessing
exposure than environmental measurements, according to public health
experts.
Because federal agencies that collect human exposure data collect these data
for different purposes, we were not able to assess the overall adequacy of
the nation's efforts to address environmental health concerns. Therefore, we
focused our work at the federal level on the efforts of two agencies--HHS
and EPA--and the subcomponents of these agencies involved in exposure
measurement and monitoring in the U.S. population:
� EPA's Office of Research and Development,
� HHS' National Center for Environmental Health (NCEH),
� HHS' National Center for Health Statistics (NCHS),
� HHS' Agency for Toxic Substances and Disease Registry (ATSDR), and
� HHS' National Institute of Environmental Health Sciences (NIEHS).
We focused our work mainly on nonoccupational environmental exposure to
chemical agents known or thought to pose a health hazard by one or more of
these agencies.
To gather information about activities of state officials, we surveyed
environmental health officials in state public health agencies and conducted
site visits to six states.
To assess the extent to which the federal agencies we reviewed have
collected human exposure data, we met with key officials responsible for
efforts intended to collect human exposure data at each agency. We focused
on what we identified as being the most significant federal efforts in human
exposure assessment at EPA and HHS related to nonoccupational human exposure
to environmental contaminants. We reviewed four major activities: EPA's
National Human Exposure Assessment Survey (NHEXAS), CDC's National Health
and Nutrition Examination Survey (NHANES), NIEHS' Human Exposure Initiative,
and ATSDR's exposure investigation activities around hazardous waste and
other sites. We also obtained information on EPA's National Human Adipose
Tissue Survey (NHATS), which ended in 1992.
We also interviewed officials and obtained documentation on how these
various programs were planned and organized and to assess the extent data
were collected in a manner that allows the identification of at-risk
subpopulations by such factors as income, race and ethnicity, age, and
geographic location. We obtained relevant budget information for 1999 and
reviewed related agency performance plans.
To assess barriers to progress in collecting or using human exposure data,
we interviewed federal officials involved in such efforts about past and
current views on such barriers. In addition, we reviewed the general
literature on human exposure to environmental chemicals and interviewed
officials from organizations representing state epidemiologists, state
public health laboratory directors, local public health officials, the
chemical industry, environmental advocates, and public health experts.
To gather nationwide data on the views of state public health officials, we
surveyed officials with environmental health responsibilities related to
chemical exposure in state public health agencies. We identified 93
officials in each of the 50 states and the District of Columbia--referred to
collectively as states--with assistance from the Council of State and
Territorial Epidemiologists and officials in each of the 51 states.
We also conducted on-site work at EPA, CDC agencies, and NIEHS and in six
states--California, Louisiana, Massachusetts, North Carolina, Oregon, and
Washington. These six states were selected to represent diverse geographic
areas and environmental health programs. In the six states, we interviewed
state public health officials. We also interviewed officials in state
environmental protection and agriculture agencies, academic and independent
researchers, and representatives of community advocacy organizations.
We excluded efforts to collect human exposure data within occupational
settings from the scope of our review. Similarly, we excluded federally
supported academic and private sector research efforts.
Our work was conducted from March 1999 through March 2000 in accordance with
generally accepted government auditing standards.
To assess the extent to which human exposure data are available for
chemicals of high concern to human health, we analyzed a number of chemical
lists maintained by HHS and EPA agencies. We also identified chemicals
measured through HHS and EPA representative surveys.
Chemical data were gathered from various sources, including EPA's Offices of
Pesticide Programs, Air and Radiation, Pollution Prevention and Toxics, and
Research and Development; the National Toxicology Program (NTP)
headquartered at NIEHS; CDC's ATSDR; and NCEH and NCHS within ATSDR. Several
toxic chemical lists were identified through a review of related reports and
literature on environmental exposure issues. To narrow the scope, we also
contacted staff in relevant offices within these agencies and asked them to
identify key lists of chemicals of concern. We consulted experts and public
health laboratory officials at the Pew Commission for Environmental Health
and the Association for Public Health Laboratories.
From the many available chemical lists, we judgmentally selected eight based
on our assessment that each list contained chemicals thought to have a high
potential for causing harm to human health and input and recommendations
from experts. These eight lists, which contained more than 1,400 unique
chemicals, provide a conservative number of the chemicals agency officials
consider a concern for human health. To ensure that chemicals with more than
one name were not included more than once, we used Chemical Abstract Service
numbers, a unique identifier. These lists, whether singly or combined, do
not necessarily reflect the highest priorities of the federal government or
the agencies or programs we contacted. The lists we reviewed are described
below.
� Chemicals found most often at the nation's Superfund sites: HHS' ATSDR,
which conducts public health assessments or other health investigations for
populations living around national priority hazardous waste sites, and EPA
prepare a list, in order of priority, of hazardous substances. This list
contains substances that are most commonly found at facilities on the
National Priorities List (Superfund) and pose the most significant potential
threat to human health due to their known or suspected toxicity and
potential for human exposure.
� EPA's list of toxics of concern in air: The Congress established the
original list of 188 hazardous air pollutants that EPA would regulate
through the Clean Air Act. EPA periodically must revise the list to add or,
when warranted, remove substances. EPA adds substances that it determines to
be air pollutants that are known to cause or may reasonably be anticipated
to cause adverse effects to human health or adverse environmental effects.
� Chemicals harmful because of their persistence in the environment,
tendency to bioaccumulate in plant or animal tissues, and toxicity: EPA's
Office of Solid Waste and Office of Pollution Prevention and Toxics created
this list of persistent, bioaccumulative, and toxic (PBT) chemicals. PBT
chemicals do not readily break down or decrease in potency after they are
released into the environment, even if released in quantities that are very
small and legally permitted. Over time, these chemicals are likely to
accumulate in soils or other environmental media, be absorbed or ingested by
animals and plants, accumulate in animal and plant tissue, pass through the
food chain, and potentially cause long-term human health or ecological
problems.
� Priority pesticides of potential concern: We combined two lists of
potentially harmful chemicals to develop this list. EPA's Office of
Pesticides Programs provided a list of pesticides of concern that were
classified as organophosphates; carbamates; or group B1, B2, or C
carcinogens. According to a program official, these classes of pesticides
are generally considered among the most potentially harmful to human health.
We combined this list with the U.S. Department of Agriculture's Pesticide
Data Program list of pesticides that are measured in selected commodities or
foods. Pesticides monitored by the program in 1997 included insecticides,
herbicides, fungicides, and growth regulators in fresh and processed fruit
and vegetables, whole milk, and grains.
� Chemicals that are known or probable carcinogens: HHS' Report on
Carcinogens includes substances known or reasonably thought to be
cancer-causing based on evaluations of substances performed by scientists
from NTP, other federal health research and regulatory agencies, and
nongovernment institutions. The list of substances in the report represents
an initial step in hazard identification. Substances listed as "known to be
human carcinogens" are those for which there is sufficient evidence of
carcinogenicity (cancer-causing potential) in humans to indicate a causal
relationship between exposure to the agent, substance, or mixture and human
cancer. Substances listed as "reasonably anticipated to be human
carcinogens'' are those for which there is limited evidence of
carcinogenicity in humans, insufficient evidence of carcinogenicity in
experimental animals, or both.
� Chemicals that are considered toxic and used, manufactured, treated,
transported, or released into the environment: EPA publishes the Toxics
Release Inventory containing information on the release and other waste
management activities of toxic chemicals by facilities that manufacture,
process, or otherwise use them. This database is made available to the
public and is considered useful to citizens, businesses, and governments for
purposes of working together to protect the quality of their land, air, and
water and for evaluating the probability that chemical releases could impact
human health in communities.
� Chemicals most in need of testing required by the Toxic Substances Control
Act: The Master Testing list contains those chemicals that are prioritized
for safety testing based on EPA's finding that (1) a chemical may present an
unreasonable risk of injury to human health or the environment and/or the
chemical is produced in substantial quantities that could result in
significant or substantial human or environmental exposure, (2) the
available data to evaluate the chemical are inadequate, and (3) testing is
needed to develop the required data.
We compared the combined list of these chemicals, totaling 1,456, and each
individual list with those chemicals identified by EPA and CDC officials as
measured in the NHEXAS and NHANES human exposure efforts through 2000. We
excluded NHATS' and the Human Exposure Initiative's chemical lists from our
analysis. NRC's 1991 review of the NHATS program raised questions about, for
example, the representativeness of the results and the methods used to
handle the tissue specimens. NIEHS' Human Exposure Initiative measurements
were not complete at the time of our review and thus it was not known which
chemicals had been or are currently being measured.
To develop survey questions, we reviewed documentation on environmental
health programs prepared by HHS and EPA agencies, professional organizations
representing state epidemiology and public health laboratory officials, and
public health experts. We also spoke with officials and representatives from
each of these groups.
We pretested our survey in person with state environmental health officials
in two states and in teleconferences with officials in two additional
states. We asked knowledgeable people in EPA and CDC and in the
environmental and public health fields to review the survey instrument. We
refined the questionnaire in response to their comments to help ensure that
potential respondents could provide the information requested and that our
questions were fair, relevant, answerable with readily available
information, and relatively free of design flaws that could introduce bias
or error into our study results. We mailed questionnaires to the 93
officials in August 1999. We sent at least one follow-up mailing and
conducted telephone follow-ups to nonrespondents. We ended data collection
in December 1999; had received responses from 81 officials in 48 states for
a response rate of 87 percent.
In preparing for our analysis, we reviewed and edited the completed
questionnaires and checked the data for consistency. We tested the validity
of the respondents' answers and comments by comparing them with data we
gathered through interviews with public health experts and other public
health officials and with documentation obtained at federal agencies and in
case study states.
The survey and survey results are presented in appendix III.
Reported Gaps in Human Exposure Data and History of Federal Efforts
Since the 1980s, reports reviewing environmental health data needs have
recommended the broader collection of human data showing actual human
exposures to chemical contaminants in the environment. Various federal
agencies have collected such human exposure data for a number of purposes;
historically, these collection efforts have been limited to selected
chemicals, subpopulations, and time periods.
Exposure to Chemical Contaminants
Data on actual levels of chemicals in humans has been a longstanding gap in
the information needed to establish human health risks from exposures to
environmental contaminants. While data on the concentration of chemicals in
environmental media--such as air, water, and food--have historically been
used to estimate human exposure to harmful chemicals, this approach to
detect or define human health risks has limitations. According to the NRC,
there are too many chemicals, too many sources, and too many routes of
exposure to rely solely on environmental monitoring. Measurements of
internal doses of exposure--actual levels of chemicals or their metabolites
found in human tissues, such as blood or urine--are generally considered an
accurate measure of human exposure. Such measurements can reflect exposures
from all routes and that may be accumulated over time, modified by
individual differences in physiology, and difficult or impossible to assess
by environmental measurements (such as hand-to-mouth ingestion in young
children). In 1991, NRC reported that a program of human tissue monitoring
is critical to the continued improvement of understanding of exposure to
toxic chemicals and recommended that such a program be given high priority
for funds and other resources.48
Several other federal reviews have pointed to information needs in this
area. An interagency assessment of federally supported databases conducted
in the early 1990s concluded that federal data systems generally lacked data
on actual human exposures, including information about contact between the
chemical and the human body (personal exposures) and the amount of the
chemical absorbed (internal doses). The review also found substantial value
in collecting and analyzing these data in a comprehensive and systematic
manner and that the costs associated with
establishing and maintaining appropriate databases were justified.49 A
discussion of some of these reviews follow.
� HHS, NCHS, Environmental Health: A Plan for Collecting and Coordinating
Statistical and Epidemiologic Data (Washington, D.C.: Government Printing
Office, 1980): This report found that "acceptable ranges of physiologic
measurements and normal levels of trace elements must be determined before
any attempt can be made to associate health outcomes with environmental
exposures. Many of these baseline data do not exist for particular
populations of interest or for specific pollutants. In addition, early
indicators and symptoms of disease that might be environmentally related are
not clearly understood." The report identified a number of research
directions to help define the association between health effects and
specific environmental exposures, including the establishment of baseline
data on physiological measurements of trace elements in tissue and blood for
the population.
� HHS, NIEHS, Issues and Challenges in Environmental Health (Washington,
D.C.: National Institutes of Environmental Sciences, 1987): This report
found that due to "gaps in data systems established for monitoring and
surveillance of environmental exposure, effort should be made to foster
better linkage among existing systems. . . . Existing data systems should be
expanded to include biochemical and cellular indicators of early stages of
disease. . . . The group found there is a need for more research and more
systematic collection of data on the exposure of human populations to
harmful substances. Reliable exposure data are necessary for assessing the
probability that exposed populations will develop adverse health effects and
the likelihood of success in intervening to reduce those risks."
� K. Sexton and others, "Estimating Human Exposures to Environmental
Pollutants: Availability and Utility of Existing Databases": This report
found that while "the evidence suggests that existing data systems contain a
substantial amount of information that is relevant to exposure estimation .
. . the quality of the data is inconsistent and difficult to assess and that
understanding and accessing the information is often difficult. Furthermore,
these systems demonstrate a striking absence of data on actual human
exposures, including a lack of information about contact between the agent
and the human body (exposure) and about the amount of the agent or its
metabolites that enters the body (dose)."
� NRC, Hormonally Active Agents in the Environment: This report found that
"determining the risk of environmental hormonally active agents to humans
and wildlife is difficult because exposure to these agents has not been
routinely monitored . . . . Background concentrations of hormonally active
agents in humans, particularly in adipose (fat) tissue and blood, and other
biota need to be established. In particular, routes of exposure and the
effects of diet need to be assessed to provide a framework for examining the
effects of these compounds in the general population and in highly-exposed
subpopulations."
Since 1967, HHS and EPA have conducted federal surveys to assess the U.S.
population's exposures to toxic chemicals from the analysis of human tissue
samples. While their efforts measured some of the same exposures and covered
some of the same time periods, their goals differed and most did not include
a nationally representative sample of citizens. EPA's efforts first
monitored exposure to pesticides and, more recently, have attempted to link
human exposure data to specific routes of exposure. CDC's periodic surveys
are intended to monitor trends in the health and nutrition status of the
population but, over time, have included exposures to environmental toxics
as one component of the general survey. NIEHS' Human Exposure Initiative,
established in the late 1990s, is intended to help the agency prioritize
chemicals for further toxicology and carcinogenicity testing. Within these
studies, various subgroups have been used to develop human exposure
estimates, but in most cases, sampling has not been for all participant
groups or random. Consequently, the results cannot be projected to the U.S.
population as a whole for most chemicals. See table 5 for the time frames
and numbers of chemicals covered for major federal efforts.
Table 5: Number of Chemicals and Time Frames for Select Federal Efforts
Number of
chemicals
Number of measured
Number of chemicals
Duration participants measured for any
providing for all
biological samples participants participants
(ages 1 and
older)
Second National Health and Nutrition Examination Survey (NHANES II)
1976-1980 20,000 examineda 36 1
Third National Health and Nutrition Examination Survey (NHANES III)
1988-1994 30,000 examineda 47 1
National Health and Nutrition Examination Survey, 1999 (NHANES)
1999-ongoing 5,000 per yearb 74c 2d
National Human Adipose Tissue Survey (NHATS)
1967-1992 14,000 128 20e
National Human Exposure Assessment Survey (NHEXAS) Pilot Study
1995-1999 460f 46c 6
aThe number of participants in NHANES II and NHANES III who received
physical examinations is used as a proxy for the number providing biological
samples, as the latter number was not readily available.
bThe number of persons examined in a calendar year is planned to be about
5,000.
cFor NHANES, the list of potentially toxic chemicals covered was provided by
CDC laboratory officials. For NHEXAS, the list of potentially toxic
chemicals covered was provided by EPA NHEXAS officials.
dAccording to a CDC laboratory official, lead and cadmium are measured in
all participants. Cotinine will also be measured in many
participants--specifically, those ages 4 and older.
eChemicals analyzed by NHATS varied over time. NHATS collected data on 20
pesticides between 1970 and 1981. NIEHS chemicals are not included because
data were not available at the time of our review.
fExcludes a related but separate study done in Minnesota reviewing pesticide
exposures that was not one of the three formal pilot surveys.
A description of these federal efforts to collect human exposure data
follows.
� CDC's National Health and Nutrition Examination Surveys: NHANES, conducted
multiple times since 1960 by NCHS, is designed to provide national estimates
of the health and nutrition status of the noninstitutionalized civilian
population of the United States. Estimates are obtained by examining
randomly selected participants in a manner that accurately reflects the
demographic characteristics of the U.S. population. Participants are given
comprehensive physical examinations (including tissue samples) and are
interviewed on issues such as their nutritional habits, health conditions,
and housing characteristics. NHANES data are used for a number of purposes.
For example, in addition to monitoring changes in blood lead levels, uses of
NHANES include development of national standards for blood pressure and
cholesterol levels and for determining infection rates for diseases. CDC's
laboratory housed at NCEH performs the measurements of chemicals in human
tissues for NHANES.
� Second National Health and Nutrition Examination Survey: NHANES II was
designed to provide national estimates of the health and nutritional status
of the civilian noninstitutionalized population of the United States for
persons aged 6 months to 74 years. Children, the elderly and people
classified as living at or below the poverty level were oversampled in order
to increase the reliability of the estimates for these groups. Measurements
of pesticide residues were taken from participants who were between the ages
of 12 and 74 years of age.50 Blood lead measurements were taken from
participants in all age groups in the survey.
� Third National Health and Nutrition Examination Survey: NHANES III was
designed to provide national estimates of health and nutritional status of
the civilian noninstitutionalized population of the United States ages 2
months and older. Children ages 2 months through 5 years, blacks,
Mexican-Americans, and persons ages 60 or older were oversampled to increase
the reliability of the estimates for these groups. Blood lead measurements
were taken from all participants ages 1 year or older. Cadmium measurements
were taken from all participants ages 6 years or older. In addition, some
participants ages 20 through 59 years had measurements taken for volatile
organic compounds and pesticides. Participants volunteered for these
additional measurements, so the results cannot be projected to the
population as a whole. However, the results still serve as the reference
ranges for these chemicals.
� National Health and Nutrition Examination Survey, 1999: In 1999, NCHS
changed the design of NHANES so that it will now be conducted as a
continuous survey of about 5,000 participants annually. Like the previous
surveys, NHANES will yield nationally representative results for the
civilian noninstitutionalized population. The NHANES design will allow for
oversampling to vary between years; persons aged 12 to 19, persons aged 60
and over, blacks, and Mexican-Americans are being oversampled. It will be
tied to related federal government data collections conducted on the general
U.S. population, in particular, the National Health Interview Survey.51 NCHS
also plans to release results from the survey every year after the first 3
years of data collection. More than 1 year of data will be required for many
estimates, particularly among detailed subgroups of the population. While
lead and cadmium will be the only potentially toxic chemicals measured for
all participants ages 1 and older (although cotinine, a metabolite which
illustrates exposure to environmental tobacco smoke, will be measured for
most age groups--those ages 4 and over), NCHS and NCEH plan to get
nationally representative data for specific chemicals for persons in
specific demographic groups, such as mercury measurements in women ages 16
through 49. NCHS will also measure household lead dust, drinking water
contaminants, and exposure to volatile organic compounds for selected
participants. In addition to conducting an annual national survey, NCHS is
developing a smaller, more targeted health survey--the Defined Population
Health and Nutrition Examination Survey (DP-HANES). NCHS recognizes that
NHANES cannot collect information that would be directly useful at the local
or state level or for small populations. DP-HANES is intended to address
this issue through the use of small mobile examination centers that would
visit areas of interest and examine 2,000 to 3,000 participants for each
special study. DP-HANES participants would not receive the full range of
tests given under NHANES; rather, the DP-HANES examination would be tailored
to the specific needs of the population under study.
� EPA's National Human Adipose Tissue Survey : NHATS was intended to be a
continuously operating survey that would collect, store, and analyze samples
of autopsy and surgical specimens of human adipose tissue from major
metropolitan areas of the country. It was established by HHS in 1967 and was
transferred to EPA in 1970. During its existence, NHATS data documented the
widespread and significant prevalence of pesticide exposures in the general
population. NHATS data also showed that reduced use of polychlorinated
biphenyls (PCB) and DDT and dieldrin (common insecticides) resulted in lower
tissue concentrations of these compounds. A trend analysis for 1970 through
1981 of NHATS data showed a dramatic decline in PCB concentrations after the
regulation of PCBs in 1976. During the 1980s, problems with NHATS' survey
design, management, and goals were compounded by insufficient financial
support and caused the usefulness and quality of NHATS to deteriorate. In
1991, NRC conducted a study to review and evaluate the effectiveness and
potential applications of NHATS.52 The study concluded that a more
comprehensive national program of human tissue monitoring was a critical
need for understanding human exposures to environmental toxics. In addition,
EPA needed a human tissue monitoring program in order to evaluate the need
and effectiveness of EPA's regulatory programs. The study recommended that
NHATS be completely redesigned to provide more useful data based on
probability samples of the whole U.S. population and that funding be
increased to permit the program to fulfill its mission. EPA ended the NHATS
in 1992 and replaced it with the NHEXAS pilot surveys.
� EPA's National Human Exposure Assessment Survey Pilot Surveys: The NHEXAS
pilot surveys were designed to obtain knowledge on the multiple pathways and
media population distribution of exposures to several classes of chemicals
and to test the feasibility of conducting a national survey to provide
estimates on the status of human exposure to potentially high-risk
chemicals. NHEXAS was also designed to measure "total exposure"--the levels
of chemicals participants take in through the air they breathe; the food,
drinking water, and other beverages they consume; and in the soil and dust
around their homes. Measurements have also been made of chemicals in
biological samples (such as blood and urine) provided by some participants.
Participants completed questionnaires to help identify possible sources of
exposure to chemicals. As designed, NHEXAS has three phases. Phase I is
intended to develop and validate NHEXAS methods, phase II is designed to
obtain nationally representative exposure data in a manner similar to that
used by NHANES to get health data, and phase III is designed to follow up on
information developed from phase II and will study selected subpopulations.
EPA conducted NHEXAS phase I (pilot) surveys in Arizona, Maryland, and EPA's
region 5 (Illinois, Indiana, Michigan, Minnesota, Ohio, and Wisconsin).
About 460 participants in the pilot surveys provided biological samples;
examinations measured a variety of chemicals, such as volatile organic
compounds, heavy metals, and pesticides. Human tissue measurements were
performed under interagency agreement by CDC's environmental health
laboratory. EPA has completed most of the fieldwork for the NHEXAS phase I
surveys and is now analyzing the results. Based on these results, EPA will
finalize the scope and methods for NHEXAS phases II and III.
� ATSDR's Exposure Investigations: As part of its health assessment process
or in response to requests, ATSDR may conduct limited biological monitoring
at hazardous waste sites or other locations through a process called
exposure investigations. In response to the recognition that the conclusions
drawn from indirect methods of measuring exposures were often not accurate
and not reliable for assessing potential health impacts and the need for
more direct measures of exposures, ATSDR formally established an exposure
investigation unit within its Division of Health Assessments and
Consultation. The Exposure Investigation Section was established in 1995 and
is comprised of nine staff members who respond to requests to conduct
exposure investigations around hazardous waste sites. These investigations
involve gathering biological samples, conducting personal monitoring for
site-related contaminants and their byproducts, and analyzing environmental
data using computational tools.
In 1996, ATSDR convened an expert review panel to comment on ATSDR's
exposure investigation program, including whether ATSDR was on the right
track in providing exposure information to improve public health
decisionmaking intended to address environmental releases from hazardous
waste sites. The panelists endorsed many aspects of ATSDR's investigative
process, including the following:
� Conducting exposure investigations prior to preparing public health
assessments, which makes agency responsibilities easier because information
is provided that enables federal agencies to take action and respond to
community concerns in a timely manner.
� Considering exposure determinations to be as important as obtaining
environmental monitoring results.
� Emphasizing the human element of exposure investigations, which
illustrates that the federal government responds to community concerns.
The panel also made several suggested improvements to the process, including
establishing a national clearinghouse of exposure investigation data and
results and developing site criteria and a protocol for identifying who will
decide on sites to target for exposure investigation.
ATSDR's exposure investigations have been valuable but limited in scope.
ATSDR used biological monitoring in conducting 47 exposure investigations
between 1995 and July 1999. Of these investigations, 17 were done in support
of the 460 health assessments done at that time. Unlike NHANES and the
NHEXAS pilot surveys, exposure investigations usually have a small number of
participants (less than 100) who volunteer to participate in the study.
While the exposure investigations are not intended to be used for
generalizations about larger populations, the studies have proven very
useful in ATSDR's community outreach and intervention activities.
� NIEHS' Human Exposure Initiative: In 1996, this initiative, a
collaboration between NIEHS and CDC, was started to improve understanding of
human exposures to hormonally active agents--also called "environmental
endocrine disrupters"--for the national population. CDC's environmental
health laboratory under an interagency agreement is developing methods for
and measuring up to 80 chemicals thought to be hormonally active agents in
blood, urine, or both. Human tissue samples used for these measurements are
largely obtained from the ongoing sampling of the general population under
NHANES and total about 200 in number.
In 1999, NIEHS and NTP officials proposed to expand the initial
collaboration between NIEHS and CDC by quantifying human internal exposures
to selected chemicals that are released into the environment and workplace.
NTP officials indicated this information would benefit public health and
priority-setting in a number of ways. First, it would strengthen the
scientific foundation for risk assessments by allowing (1) the development
of more credible relationships between exposure and response in people
thereby improving cross-species extrapolation, (2) the development of
biologically based dose-response models, and (3) the identification of
sensitive subpopulations and for estimates of risk based on "margin of
exposure." Second, it would provide the kind of information necessary for
deciding which chemicals should be studied with the limited resources
available for toxicological testing. For example, there are 85,000 chemicals
in commerce today, and NTP can provide toxicological evaluations on 10 to 20
per year. Third, the information could be used to identify and help focus
research on those mixtures of chemicals that are actually present in
people's bodies. Fourth, the types and amount of chemicals in children and
other potentially sensitive subpopulations would be identified.
Determinations of whether additional safety factors need to be applied to
children must rest in part upon comparative exposure analyses between
children and adults. Fifth, this initiative, taken together with the
environmental genome initiative, will provide the science base essential for
meaningful studies on gene and environment interactions, particularly for
strengthening the evaluation of epidemiology studies. Finally, efficacy of
public health policies aimed at reducing human exposure to chemical agents
could be evaluated in a more meaningful way if human exposure data were
available over time, including remediation around Superfund sites and
efforts to achieve environmental equity.
Survey of State Environmental Health Officials and Results
Comments From the Department of Health and Human Services
Comments From the Environmental Protection Agency
Major Contributors to This Report
Katherine Iritani, Evaluator-in-Charge, (206) 287-4820
The following individuals made important contributions to this report: Frank
Pasquier served as Assistant Director; Cheryl Williams, Senior Evaluator,
performed the literature review, assessed barriers, performed state site
visits, and--along with Anita Kay, Intern--administered the survey of state
environmental health officials; Tim Clouse, Evaluator assessed federal
efforts and evaluated information collected for identifying at-risk
populations; Sharon Silas, Intern, and Evan Stoll, Technical Analyst,
compiled and analyzed the lists of toxic chemicals; Sylvia Shanks served as
attorney-adviser, and Stan Stenersen guided the message development and
report writing.
(108398)
Table 1: Extent to Which Human Exposure Data Are Collected for Potentially
Harmful Chemicals Through NHANES or
the NHEXAS Pilot Surveys 14
Table 2: Prevalence of Elevated Blood Lead Levels in Children
Ages 1 Through 5, by Selected Demographic
Characteristics
(NHANES, 1991 Through 1994) 18
Table 3: Examples of How State Officials Use Human Exposure
Data 23
Table 4: Examples of Reports Calling for Coordination in
Environmental Health 32
Table 5: Number of Chemicals and Time Frames for Select
Federal Efforts 55
1. Metabolites result from the interaction of the chemicals with enzymes or
other chemicals inside the body.
2. The scientific community uses varying terminology when referring to human
exposures. Often, external contacts with chemicals are defined as
"exposures," and internal measurements of exposure are referred to as
"doses." Doses are also considered a measure of exposure. Our review focused
primarily on efforts to gather internal exposure measurements through human
tissue in the non-occupationally-exposed population. To simplify reporting,
we are referring to such internal exposure measurements as "human exposure"
data.
3. The Role of Monitoring Networks in the Management of the Nation's Air
Quality, National Science and Technology Council, Committee on Environment
and Natural Resources, Air Quality Research Subcommittee (Mar. 1999).
4. According to NRC, human monitoring data alone can signal the need to
conduct studies on specific environmental chemicals, but these data are best
viewed as one component of a comprehensive environmental monitoring program.
Human measurements are best supplemented with knowledge of contaminant
sources, environmental pathways, environmental concentrations, time patterns
and locations of exposure, routes of entry into the body, material toxicity,
and latency. See NRC, Commission on Life Sciences, Monitoring Human Tissues
for Toxic Substances (Washington, D.C.: National Academy Press, 1991).
5. Other human biological tissues that might be used for measurements of
chemical concentrations include fat tissue, breast milk, semen, urine, liver
specimens, hair, fingernails, or saliva. Human breath has also been used to
measure exposure to certain chemicals.
6. Special reference studies supported by the Agency for Toxic Substances
and Disease Registry were also conducted on nonrepresentative samples of a
portion of the people participating in the most recently completed segment
of NHANES (conducted from 1991 through 1994). These special studies assessed
exposure to 45 pesticides and volatile organic compounds.
7. Specifically, pilot surveys were conducted in Arizona, Maryland, and
EPA's region 5 (Illinois, Indiana, Michigan, Minnesota, Ohio, and
Wisconsin).
8. The concern about endocrine disrupters originated from the finding that
some synthetic chemicals in the environment are associated with adverse
reproductive and developmental effects in wildlife and mimic the actions of
female hormones. According to NRC, although it is clear that exposures to
hormonally active agents at high concentrations can affect wildlife and
human health, the extent of harm caused by exposure to these compounds in
concentrations that are common in the environment is debated. See NRC,
Commission on Life Sciences, Hormonally Active Agents in the Environment
(Washington, D.C.: National Academy Press, July 1999).
9. According to NTP officials, chemicals are tested for cancer and noncancer
endpoints--including effects on reproduction, development, nervous system,
and immune systems--using traditional bioassays as well as newly validated
tests. Validation of new tests is achieved through an NTP interagency center
involving 15 federal agencies or institutes.
10. CDC officials indicated that, by the end of 1999, it had developed
laboratory methods to measure more than half of the chemicals under the
agreement with NIEHS.
11. We excluded NHATS and Human Exposure Initiative chemical lists from our
analysis. NRC's 1991 review of the NHATS program raised questions about the
representativeness of the results and the methods used to handle the tissue
specimens, among other questions. The Human Exposure Initiative measurements
were not available at the time of our review and, thus, which chemicals had
been or are currently being measured was not known.
12. We selected these lists based on input from program officials and
experts at EPA, HHS, the Association of Public Health Laboratories, and the
Pew Commission on Environmental Health and our assessment that the criteria
for listing a chemical demonstrated that exposure could potentially be
harmful to humans. There are many toxic chemical lists maintained by
different programs and agencies for different purposes that we did not
include in our review and, as such, the ones we reviewed do not necessarily
individually or collectively represent the chemicals of highest concern to
human health.
13. EPA's prioritized chemical list ranks chemicals based on the length of
time to break down, the degree to which they accumulate in plants and
animals, and their toxicity. Both ecological and health risk scores are
calculated. We used only the health risk scores in our analysis.
14. Executive Order 12898 requires that each agency identify and address as
appropriate disproportionately high and adverse human health or
environmental effects of its programs, policies, and activities on minority
populations and low-income populations in the United States and its
territories and possessions. Executive Order 13045 established similar
requirements with respect to children.
15. S. Perlin, K. Sexton, and D. Wong, "An Examination of Race and Poverty
for Populations Living Near Industrial Sources of Air Pollution," Journal of
Exposure Analysis and Environmental Epidemiology, Vol. 9, No. 1 (1999), pp.
29-48.
16. D. Wagener, D. Williams, and P. Wilson, "Equity in Environmental Health:
Data Collection and Interpretation Issues," Toxicology and Industrial
Health, Vol. 9, No. 5 (1993), pp. 775-95.
17. The feasibility of using a representative survey to identify at-risk
subpopulations based on individual characteristics (such as age, race, or
income level) or location (such as a city, county, or state) depends on
sample design and size--that is, on how the participants are selected and
how many participants are included. Generally, the lower the percentage of
the population in question in the sample, the less the data can be used to
develop precise estimates of exposure or to distinguish exposure levels
between subgroups.
18. Certain groups may be included at a higher rate or oversampled to ensure
a greater level of accuracy. For example, between 1988 and 1994, children
ages 2 months through 5 years surveyed in NHANES were oversampled.
19. According to CDC officials, children under 12 will not be assessed
because the volume of tissue samples needed to perform the measurement will
not be available. Other measurements--such as those for lead, mercury, and
cotinine (a metabolite of nicotine illustrating exposure to cigarette
smoke)--will be performed for many in this age group.
20. According to CDC laboratory officials, other NHANES exposure
measurements planned for 1999 and 2000 for a subsample of participants
includes volatile organic compounds, mercury, nonpersistent pesticides,
phthalates, and trace metals. Air toxic exposures to selected volatile
organic compounds will be measured in personal measurements--such as
chemical levels in the air, measured through badges, and chemicals in water
samples--and in blood samples from a subsample of people ages 20 through 59.
Mercury will be measured in the hair and blood of participants ages 1
through 5 and women ages 16 through 49. Nonpersistent pesticides or their
metabolites are planned for measurement in one-half of participants ages 6
through 11 and one-third of participants ages 12 and over. Surveys and
focused research indicate that household use of certain pesticides may be
extensive, but little information is available concerning residential or
household exposures among the general population. Phthalates are planned for
measurement in one-third of the participant ages 6 and older. Seventeen
trace metals will be measured in one-third of participants ages 6 and older.
Trace metals such as barium and beryllium have been associated with adverse
health effects in occupational or laboratory studies but have not been
monitored in the general population.
21. The current design of NHANES samples allows several years of data to be
combined. If exposure for chemicals is measured consistently over several
years, then assessing risk factors may be increasingly possible over time.
CDC officials indicated that for any annual NHANES full sample, a limited
number of estimates for broad population subgroups can be developed. More
detailed measures for smaller subgroups (for example, analyses by age,
gender, and race and ethnicity) will require more years of data, generally 3
through 6 years--and even longer if a subsample is used--of data collected
for all participants. Based on an annual sample of one-third of the
participants, CDC indicated that estimates may be possible for very broad
subgroups, such as males or females; participants ages 6 through 19 or over
20; or a few major race and ethnicity groups, depending on the prevalence of
the condition examined.
22. One assessment of the data from Midwestern states provided some
indication of potential differences in personal exposures between age
groups, races, income segments, and house construction dates. Researchers
cautioned that the data for some categories examined were small. This
assessment did not report on exposure measurements from biological sampling
in this survey. (See E. D. Pellizzari, R. L. Perritt, and C. A. Clayton,
"National Human Exposure Assessment Survey: Exploratory Survey of Exposure
Among Population Subgroups in EPA Region V," Journal of Exposure Analysis
and Environmental Epidemiology, Vol. 9 (1999), pp. 49-55.
23. These participants provided biological samples, such as blood and urine.
Larger participant groups in the study areas provided environmental and food
monitoring samples and responded to questionnaires. This excludes a related
but separate study done in Minnesota reviewing pesticide exposures that was
not one of the three formal pilot surveys.
24. Determining the distribution of chemical exposure among a
non-occupationally-exposed population establishes a "reference range" that
shows what can be considered background exposure and what can be considered
high. With reference range information, officials concerned about exposures
of groups can compare the groups' exposures to those of the general
population and determine whether public health action is warranted to
prevent or reduce high levels of exposure.
25. ATSDR conducts exposure investigations when (1) people have likely been
exposed to a contaminant, (2) more information is needed on the exposure,
(3) an exposure investigation will provide that information, and (4) that
investigation will affect public health decisions.
26. In its report, panel members suggested many improvements to ATSDR's
exposure investigations, including creating a technical planning group to
review emerging and innovative technologies and establishing a national
clearinghouse of collected data. ATSDR officials indicated that they had not
been able to act on some of the panel's suggestions because of limited staff
and resources and other barriers to collecting data, such as the lack of
laboratory methods for testing chemicals of interest. ATSDR has nine staff
to conduct exposure assessments for sites across the nation and can only
respond to requests from communities or state or local officials for
assistance rather than conducting such assessments as part of every new
investigation.
27. Federal agencies also might fund academic research that is designed to
identify communities of concern. Assessing the extent that federally
supported academic research included or focused on human exposure data to
identify at-risk population was beyond the scope of our review.
28. Since most states conduct surveillance for lead exposure, we asked
officials to not include these efforts in their responses. See app. III for
a copy of our survey.
29. This organization actively supports expanding state and local laboratory
capacity to participate in a human biomonitoring program to provide human
exposure data that would enhance the effectiveness of environmental policy
and regulatory decisions. In addition, this group helped states apply for
the four grants CDC offered to increase state and local laboratory capacity
to detect in human fluids and tissues chemicals that could be used in a
terrorist attack. Illustrating their interest in developing such laboratory
capacity, 31 state and 2 local health departments applied for the four
grants.
30. While NRC found EPA in the best position to house a human exposure
monitoring program, it also found that the ambivalence within EPA about the
National Human Monitoring program's future indicated that the match of
program goals, potential benefits, and EPA mandates was not perfect.
31. The NIEHS-supported conference addressed many opportunities and
challenges in exposure assessment research, including exposure-analysis
methodology, exposure-disease relationships, regulatory and legislative
issues, gene-environment interactions, disease prevention and intervention,
and some current federal initiatives related to exposure assessment. One
area of discussion was the need for and limitations of biological measures
of exposure.
32. Because of its emphasis on evaluating total human exposure, NHEXAS
emphasized those chemicals that can be measured in multiple environmental
media (for example in air, water, and food) as well as human tissues.
33. CDC's laboratory officials indicated that their choice of chemicals is
determined by the availability of high-quality analytical methods with
adequate throughput, whether the chemical is a known or suspected cause of
health problems, whether the chemical is on EPA and ATSDR priority lists,
the number of persons likely exposed, and the availability of funding from
collaborators.
34. Several officials pointed to the importance of developing a breast milk
monitoring program. Many environmental agents are fat soluble and are
released into breast milk at significant concentrations. Examples include
dioxins and PCBs. According to NIEHS researchers, 6 months of nursing could
result in dioxin or PCB concentrations in infants which are 10 times higher
than in the mother. Breast milk monitoring programs operate in several
European countries including Sweden, Germany, and the Netherlands.
35. EPA's scientific advisers' review of the NHEXAS pilot surveys
illustrates some of the trade-offs in determining the appropriate balance
between large population surveys and more targeted follow-up surveys. The
advisers reported that population studies are the only means for collecting
baseline information for such uses as trend analysis. NHANES is an example
of such a probability study. On the other hand, more targeted special
studies tend to assess high-end exposure groups more precisely.
Additionally, the review illustrated how total exposure data may be
unnecessary to collect for chemicals at a national level, depending on the
chemical. The advisers pointed out that targeted special studies can be used
to identify sources and factors associated with high-end exposures. While
identification of major sources, media, and pathways for populations
experiencing high exposures are essential to reduce unacceptably high risks,
if the majority of the national population is exposed to pollutants at
levels under health-related benchmarks, source identification for such
exposures is not a priority from a health standpoint.
36. The follow-up to the NHEXAS pilots has not been planned, so the identity
of the chemicals to be measured is not known.
37. At this writing, NHANES' goals are to (1) estimate the number and
percentage of persons in the United States and designated subgroups with
selected diseases and risk factors; (2) monitor trends in the prevalence,
awareness, treatment, and control of selected diseases; (3) monitor trends
in risk behaviors and environmental exposures; (4) analyze risk factors for
selected diseases; (5) study the relationship between diet, nutrition, and
health; (6) explore emerging public health issues and new technologies; and
(7) establish a national probability sample of genetic material for future
genetic research. CDC officials told us that the emerging focus in NHANES on
environmental health issues reflects advances in technology as well as the
public's increasing priority for understanding the impacts of environment on
health. Part of CDC's responsibility is to report on environmental hazards
and determinants of health. Section 306 of the Public Health Service Act (42
U.S. C. 242k) directs the National Center for Health Statistics, the CDC
agency that conducts NHANES, to collect statistics on subjects such as the
extent and nature of illness and disability of the population;
environmental, social, and other health hazards; determinants of health;
health resources; and utilization of health care.
38. According to CDC laboratory officials, the first report card will
provide data on exposure levels of the population to 25 chemicals that have
not yet been determined. These might include selected heavy metals, indoor
air pollutants, nonpersistant pesticides, and phthalates.
39. Because of the wide range of other health and nutrition questions
addressed in NHANES, environmental measurements currently included are less
extensive than those included in NHEXAS because, for example, food and
beverage samples are not conducted.
40. NIEHS-CDC interagency agreements document that NIEHS had provided about
$3.3 million to CDC between fiscal years 1996 and 2000 for performing
environmental exposure measurements for its Human Exposure Initiative. No
funding was provided in fiscal year 1999.
41. NHANES 1999, for example, received $15.9 million in appropriated funding
and, according to CDC officials, an additional $6.8 million from
collaborating institutions. Interagency agreements related to environmental
measurements performed in conjunction with NHANES document the receipt of
about $1.4 million from collaborators at EPA and other agencies for
environmental exposure measurements. In addition to EPA's support for
measurement of certain chemicals in human tissues, an estimated $125,000 was
received from the Department of Housing and Urban Development for performing
dust sampling and an estimated $30,000 from the Mickey Leland National Urban
Air Toxics for personal measurements of volatile organic compounds. CDC
laboratory officials indicated that the increase to their fiscal year 2000
funding for the environmental health laboratory has improved their ability
to support needed laboratory measurements for NHANES and other efforts. This
funding increased by about $5 million between fiscal years 1999 and 2000.
42. According to CDC officials, uncertain funding may limit their ability to
perform NHANES measurements for dioxins, furans, coplanercoplanar PCBs,
phytoestrogens, certain heavy metals, phthalates, and polyaromatic
hydrocarbons.
43. EPA officials indicated that at the individual study level,
approximately $250,000 was allocated for analyses of the NHEXAS pilot data
in fiscal year 1999; EPA plans to spend approximately $170,000 in fiscal
year 2000.
44. See Observations on the Environmental Protection Agency's Fiscal Year
2000 Performance Plan (GAO/RCED-99-237R ) July 20, 1999.
45. This effort was coordinated through the White House Office of Science
and Technology Policy.
46. Executive Order 13045 also indicates such strategies are to include
proposals to enhance public outreach and communication and a statement
regarding the desirability of new legislation to fulfill or promote the
purposes of the order.
47. The Director of NTP issues the Report on Carcinogens pursuant to a 1978
amendment, section 301(B)(4) of the Public Health Services Act, which
requires the Secretary of HHS to publish a list of all substances that are
either known to be human carcinogens or may reasonably be anticipated to be
human carcinogens and to which a significant number of persons residing in
the United States are exposed. NTP issues a revised Report on Carcinogens
every 2 years.
48. NRC, Commission on Life Sciences, Monitoring Human Tissues for Toxic
Substances.
49. See K. Sexton and others, "Estimating Human Exposures to Environmental
Pollutants: Availability and Utility of Existing Databases," Archives of
Environmental Health, Vol. 47, No. 6 (1992), pp. 398-407.
50. Data were not publicly available, as CDC is resolving some
methodological issues associated with data collection.
51. The sampling will be conducted on different people, but some questions
asked in each survey will be the same.
52. NRC, Commission on Life Sciences, Monitoring Human Tissues for Toxic
Substances.
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