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Review of the National Human Adipose Tissue Survey and Selected Program Alternatives

DEVELOPMENT OF THE PROGRAM

The National Human Monitoring Program (NHMP) was established in 1967 to determine and assess changes in detectability and concentrations of pesticide residues in the national general population. The program was initially an activity of the U.S. Public Health Service, but was transferred to the new Environmental Protection Agency (EPA) in 1970. The NHMP now consists of the National Human Adipose Tissue Survey (NHATS); EPA planned to introduce a National Blood Network (NBN), but it has not been implemented.

It is difficult or impossible to remove persistent xenobiotics effectively from the tissues of living animals or people, so precautions must be taken against unnecessary and excessive exposures. Precautions against exposure are, however, greatly complicated by the dependence of modern society on synthetic chemicals; even the cleanest-looking environments now contain toxic contaminants. Therefore, it is prudent to assess and try to reduce their effects. An essential part of the management of toxic chemicals is regular sampling of the population to determine magnitudes of exposure and contamination.

Neither detection nor determination of concentration of a chemical in tissues of individuals or the general population provides a quantitative estimate of risks to human health. For example, people living downstream from a defunct DDT plant in Triana, Alabama, were chronically exposed to DDT in their diets for many years and have several times the national geometric mean for DDT and related chemicals (e.g., DDD and DDE) in their serum. However, a survey of the health status of 499 of them, out of approximately 600, indicated that total DDT body burdens were not associated with specific illness or ill health (Kreiss et al, 1981). But some chemicals can be degraded so rapidly that they cannot be detected in tissues even a few hours after expo-



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Monitoring Human Tissues for Toxic Substances 2 Review of the National Human Adipose Tissue Survey and Selected Program Alternatives DEVELOPMENT OF THE PROGRAM The National Human Monitoring Program (NHMP) was established in 1967 to determine and assess changes in detectability and concentrations of pesticide residues in the national general population. The program was initially an activity of the U.S. Public Health Service, but was transferred to the new Environmental Protection Agency (EPA) in 1970. The NHMP now consists of the National Human Adipose Tissue Survey (NHATS); EPA planned to introduce a National Blood Network (NBN), but it has not been implemented. It is difficult or impossible to remove persistent xenobiotics effectively from the tissues of living animals or people, so precautions must be taken against unnecessary and excessive exposures. Precautions against exposure are, however, greatly complicated by the dependence of modern society on synthetic chemicals; even the cleanest-looking environments now contain toxic contaminants. Therefore, it is prudent to assess and try to reduce their effects. An essential part of the management of toxic chemicals is regular sampling of the population to determine magnitudes of exposure and contamination. Neither detection nor determination of concentration of a chemical in tissues of individuals or the general population provides a quantitative estimate of risks to human health. For example, people living downstream from a defunct DDT plant in Triana, Alabama, were chronically exposed to DDT in their diets for many years and have several times the national geometric mean for DDT and related chemicals (e.g., DDD and DDE) in their serum. However, a survey of the health status of 499 of them, out of approximately 600, indicated that total DDT body burdens were not associated with specific illness or ill health (Kreiss et al, 1981). But some chemicals can be degraded so rapidly that they cannot be detected in tissues even a few hours after expo-

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Monitoring Human Tissues for Toxic Substances sure (Lynn et al., 1984). Such chemicals include benzidine (a known human carcinogen), aflatoxin, vinyl chloride, formaldehyde, and many other toxic or carcinogenic chemicals. Therefore, failure to detect a chemical in human tissues does not mean that potentially toxic exposure to it has not occurred. The NHATS was intended to provide data on the existence and concentrations of chemical substances in human adipose tissue of a representative sample of the U.S. population. Its specific objectives were to identify chemicals to which the population was being exposed, to establish baseline and trend data on detected chemicals, to identify populations at risk and set priorities for risk reduction, and to determine the impact of regulation. The NHATS has always measured residues of chemicals in human adipose tissue. Adipose samples are submitted for chemical analysis through the cooperation of selected pathologists. Those samples are collected from postmortem examinations and from remnant specimens removed during surgery. Age, sex, race, and clinical pathologic diagnosis are requested for each patient sampled. Geographic area of residence is inferred from the location of the contributing hospital. The NHATS originally targeted polychlorinated biphenyls (PCBs) and several organochlorine pesticides for study. Those compounds are highly lipophilic and stable in biologic systems and therefore accumulate in adipose tissue; in fact, human adipose tissue contains the highest concentrations of some of the most persistent chemicals to which humans have been exposed. The NHATS therefore selected adipose tissue as best for its purpose of estimating past human exposure. Although the emphases of the program and the chemical classes targeted by the NHATS have changed substantially, adipose tissue continues to be the basis for study. Since 1967, the NHATS has collected approximately 12,000 samples of adipose tissue—some 85–90% from autopsied cadavers and the remainder from surgical patients. Tissues are collected through a national network of pathologists and medical examiners from 47 urban or metropolitan statistical areas (MSAs); no rural areas or small towns outside MSAs are included. In recent years, collection of specimens has dropped from an annual quota of 1,370 to 500–800 samples. The NHATS specimens collected during fiscal year 1982 were designated for “broad scan analysis” to determine volatile and semivolatile organic compounds (EPA, 1986a). Since 1982, the program has been modified to implement newer methods of detecting chemicals on the original target list and to expand the list of chemicals that can be detected. New methods have come into use to measure PCB homologs, chlorinated benzenes, aromatic hydrocarbons, phthalates, and phosphate esters. Those changes signaled a shift in emphasis from monitoring to exploration and the replacement of some routine

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Monitoring Human Tissues for Toxic Substances assay techniques with newer methods. Initially, individual samples were assayed; however, because of the high cost of assays, EPA later switched to the use of composite samples. Forty-six composite samples were prepared from more than 750 NHATS specimens collected during fiscal year 1982 according to a study design prepared by the EPA Office of Toxic Substances (OTS) design and development contractor, Battelle Columbus Laboratories. The NHATS data, reported in a series of publications, have documented a widespread and significant prevalence of pesticide residues in the general population (Kutz et al., 1979; Strassman and Kutz, 1981). The program has also identified a high-risk population exposed to the pesticide Mirex (Kutz et al., 1985). NHATS data have shown that reductions in use of PCBs, DDT, and dieldrin have been followed by a decline in measured concentrations of these compounds. A specific high point for the NHATS came in 1982 with the release of a 1970–1981 trend analysis showing a dramatic decline in PCB concentrations after the 1976 PCB regulation. With this as an impetus, EPA moved to develop state-of-the-art analytic protocols. In fiscal year 1987, EPA proposed a National Blood Network that would use three U.S. blood-collection agencies as a surveillance system to monitor residues of industrial chemicals in the blood of volunteer donors. The purpose was to establish baselines and time trends for the nation as a whole and for various population groups. It was intended to complement the NHATS data by permitting less invasive collection of specimens from some subjects (blood rather than fat) and to reflect more recent, rather than only long-past, exposures. It would also complement the NHATS by focusing on volatile organic chemicals (e.g., benzene and trichloroethylene) and elements (e.g., lead, cadmium, and arsenic), as well as semivolatile organics. The NHMP has also carried out several special studies, alone or in collaboration with other agencies. They included an archive stability study, participation in a World Health Organization study of lead and cadmium in blood, a clinical study of PCBs in transformer workers, development of a national body-burden database, and (with the Veterans’ Administration) a dioxin-furan study of Vietnam veterans exposed to Agent Orange. The NHMP has suffered in recent years because of budget cuts. The NBN has never been initiated, and analysis of NHATS specimens has lagged. The NHMP is now funded only through fiscal year 1990. Program Deficiencies The NHATS program is the only comprehensive human tissue monitoring program in this country. In the face of the data needs generated by the vast

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Monitoring Human Tissues for Toxic Substances use of chemicals in the United States, it is expected to provide a national assessment of chemical exposures on an annual budget of less than a million dollars. In spite of its small present budget, it has collected approximately 12,000 samples of human adipose tissue over some 20 years through a national network of pathologist and medical examiners. EPA and its dedicated staff deserve recognition for that effort. However, the program has a number of serious problems. A basic statistical problem is that the original design was very weak; it used probability sampling for only one stage of sample selection, and even that use has been diluted over the years. Thus, the ability to generalize results is seriously limited. Another weakness is that the original design of the program did not include rural areas in the samples. The annual quota for sample collection has been 1,370; however, the average has been much lower since 1970, and only 500–800 samples have been collected in part because of a decrease in funding. Another concession to decreased funding has been a move to assay composite, rather than individual, samples. Budget reductions have also caused proposed modification and expansion of the program to be delayed, with indefinite postponement of such key steps in the program as chemical analysis of tissues, data analysis, methods development, and reporting of survey results. And the blood network has yet to be implemented. The NHATS program is now more than 20 years old. It has not aged or developed gracefully. Collection and analysis of samples have not been nearly as effective or as representative of the population as planned. Storage of samples has been inappropriate, and there is a question of whether samples collected more than a year or two ago can be used for adequate quantitative estimation of donor exposure; such specimens might be only minimally adequate even for qualitative analysis of some exposures. Data obtained from the samples have been the basis for several publications and reports, but they have not been used as effectively as they could have been. Relative to the time and money invested in the program, the publications and reports are few and cursory; and publication of reports describing survey results is usually several years behind data collection. All those factors have combined to damage the prestige and credibility of the program. The NHATS has rarely enjoyed the support that such a program deserves, and, because of its waning reputation, it currently appears to be a program that higher EPA management wishes to avoid rather than support. In summary, the NHATS program was well intended and has many important and worthwhile goals. At its inception, approximately 20 years ago, the program was at the state of the art of pesticide analysis in human tissues. However, NHATS management has expanded the objectives of the program to encompass more than was originally intended while failing to improve and

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Monitoring Human Tissues for Toxic Substances expand its design and support appropriately. The lack of innovation and leadership over the years has resulted in a program that is out of date and only partially fulfills its objectives. Design and management problems have been compounded by the failure of the program to receive financial and managerial support in proportion to its expanding objectives. As a result, the program has promised more than it can deliver, and both the quality and the quantity of data obtained from the NHATS have failed to meet reasonable expectations. Without the necessary managerial and financial support, the overall quality of the NHATS has deteriorated to the point where questions have been raised as to whether it is still worth while or even salvageable. A short summary of the major weaknesses of the current NHATS program follows. More detailed discussion of these weaknesses is presented in later chapters. Toxicologic Issues (see Chapter 3) A blood collection system has been proposed, but all prior tissue collection has been limited to adipose tissue. Variation of adipose storage of chemicals with body site (e.g., subcutaneous vs. perirenal) has not been reviewed carefully. And analysis of chemicals with lower lipid partition coefficients (e.g., heavy metals) has not been emphasized. Storage of specimens under suboptimal conditions might prevent the analysis of specific biologic markers; for example, some may be unstable at the storage temperatures now used. The current program has failed to correlate and evaluate tissue concentrations of chemicals with other variables important to interpretation of the concentrations (e.g., data on exposure and toxicity). Sampling Strategy (See Chapter 4) There are serious problems with the NHATS sample design. Some of them are inevitable when adipose tissue is used as the unit of analysis, and others follow from decisions made in planning the study. The most severe problems areas follow: The population of interest is presumably the entire live U.S. population, but the measurements are made on a combination of adipose tissue from recently deceased persons and surgical patients (as collection of adipose tissue is necessarily a invasive procedure); tissues from these sources may be sub-

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Monitoring Human Tissues for Toxic Substances stantially affected by serious illness, treatment, and/or cachexia with concentration of fat-soluble substances. There has been no evaluation of whether contaminant concentrations in tissue from these sources are similar to concentrations in the population as a whole. Most of the rural population is excluded from the sampling frame; there is no information on urban-rural differences that would permit inferences about the U.S. population. Probability sampling was used for only one of four stages of sampling— the selections of metropolitan sample areas. There is no information on potential biases of the sample selection. In the one stage that was selected with probability methods, there has been a deterioration in the quality of the sample. There has not been adequate consideration of the precision needed for data analysis or of the sample sizes appropriate for the NHATS. Insufficient attention has been paid to the implementation of the sample selection procedures. As a result, the sample sizes specified for the NHATS have not been attained in recent years. Furthermore, the contractor’s latitude in choosing counties and medical examiners or pathologists and the medical examiners’ and pathologists’ latitude in choosing tissue specimens are so wide that it is not clear how well the specimens represent the population that was intended by the sampling protocol. Starting with samples collected in 1982, the NHATS stopped separate analyses of each tissue specimen and introduced analyses of composites; that led to a substantial loss of ability to analyze and interpret NHATS results. There is no direct way to derive prevalence estimates. Statistical modeling is used to estimate mean concentrations by age, sex, and race, but the adequacy of the models has not been tested sufficiently. Little or no effort has been made to establish confidence levels around the NHATS estimates. As a result, analysts have difficulty in knowing whether changes over time or differences among population groups reflect real differences or are only random fluctuations. Collection, Storage, and Archiving of Tissues (see Chapter 5) Tissue samples now stored have been transferred among several repositories, and some have been thawed (both accidentally and deliberately to permit partial analysis). There is a lack of storage history, including freeze-thaw history, of many earlier specimens.

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Monitoring Human Tissues for Toxic Substances Inadequate numbers of specimens are being collected, and storage conditions at collection sites are not uniformly controlled. Specimen storage containers are not suitable for some analytes. Collection sites have no organized quality control system. Training programs for collectors are lacking, site visits are not made to collectors, and exclusion criteria on samples are not enforced. Many tissue specimens appear to be seriously compromised, and there is evidence of sample contamination. Sample holding times of several years have been accepted, without studies validating the storage stability of target compounds over those times. Specimens in the archive are stored in an unorganized manner. There is evidence that sample containers have been inappropriate. Chemical Assay Issues (see Chapter 6) The list of compounds selected for monitoring has not been regularly reviewed and modified, and it has been expanded without sufficient systematic planning. Analytical methods introduced in 1981–1985 were implemented without sufficient validation, and analytic goals are not clearly defined or defended. Routine monitoring functions have been allowed to lapse, because of sporadic analyses, compositing of samples, and lack of continuity of results. Programmatic Issues (see Chapter 7) A critical aspect of a successful monitoring program is the reporting of findings in a format and with a timeliness that match the needs of data users. For example, tracking of a rapidly changing environmental contaminant may require regular reporting to a regulatory or enforcement office, with a delay of no more than 6 months after the close of each reporting year. Reporting of monitoring data from the NHATS was first delayed, was then at a reduced frequency, and finally broke down altogether in the late 1980s. Part of the problem was excessive EPA delay in that part of EPA that was reviewing contractor-prepared reports. Large programs can be contracted out successfully, but the export of functions must be closely matched to both the export of responsibilities and continuing technical oversight. It is the committee’s impression that contract work in support of the NHATS has been performed in a technically acceptable manner, but that critical decisions about the general thrust of the contract work have not had adequate attention from either EPA or the contractors.

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Monitoring Human Tissues for Toxic Substances Examples (cited above) include conditions of collection and storage of samples, choice of substances to be examined, and laboratory methods. In short, the contractors appear to have done an acceptable job, but sometimes the wrong things were measured. Little evidence can be found of long-range strategic planning by the staff. Program staff were concerned with such matters as maintaining the projected magnitude of specimen collection, but failed to attend to long-range planning that would enhance the value of the collected specimens. For example, there were apparent failures to build strong links with the community of potential users, to examine and deal with the implications of the program’s organizational location, to plan for adequate continuing input from a range of technical specialties, to monitor programs in other countries and to develop close communication and even working relationships with other programs in EPA, other federal agencies, and the private and nonprofit sectors. The present program has suffered, at first indirectly and later directly, from a failure to give substantial and explicit attention to promoting the use of its products (i.e., the adipose tissue archive and data from the analysis of the samples). As a result, the products have been underused or even unused. A symptom is the recurring reference to a few striking figures of the decline in DDT, PCBs, and dieldrin after regulation of use (GAO, 1988). The committee acknowledges both the importance of and the public interest in those examples, but there should be by now a large number of additional examples of the importance of NHATS data. The NHATS as a program has suffered severely from a lack of full-time, concerted attention from persons who are technically competent in the specific relevant disciplines and who have substantial leadership roles in EPA. The committee is pleased to acknowledge the individual abilities of NHATS staff, but their commitment is far short of full-time because of other, competing responsibilities. Furthermore, the program has not been supported by sufficient leadership or full-time managerial personnel. EXISTING PROGRAMS AS POSSIBLE ALTERNATIVES TO THE NATIONAL HUMAN ADIPOSE TISSUE SURVEY The committee made a deliberate effort to consider alternatives to the present or a related successor program. This section briefly describes several programs that have some points of similarity to the National Human Monitoring Program and considers whether the NHMP objectives might be met with data from these programs. The major criteria for evaluating the suitability of each of these programs to assume NHMP tasks are shown in Table 2–1. The

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Monitoring Human Tissues for Toxic Substances TABLE 2–1 Extent to Which Existing Programs Meet Criteria for a National Human Tissue Monitoring Program Criteria NHATS NHANES ATSDR NIST TEAM FDA NOAA Population-based sample (can describe the U.S. population and major groups) No Yes No No No No No Long-term commitment to monitoring (regularly repeated observations with sufficient frequency to detect changes) Yes No No No No Yes Yes Focus on toxic xenobiotics (can respond to chemicals in commerce) No No Yes No No Yes Yes Relevance to emerging research in toxicokinetics, exposure assessment, and risk assessment No Yes Yes Yes Yes No Yes

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Monitoring Human Tissues for Toxic Substances committee, therefore, considered substituting existing programs as alternatives to NHMP if the present program is terminated. National Center for Health Statistics: National Health and Nutrition Examination Surveys (NHANES) The committee has given special thought to whether the National Health and Nutrition Examination Surveys (NHANES) of the National Center for Health Statistics (NCHS) could be adapted (e.g., by collecting additional blood samples) to serve national needs for human tissue monitoring of contaminants. Because the NHANES already takes blood samples, NHANES analysis of blood might seem to be a plausible alternative to a separate program. Our review of the NHANES indicates that it is not an adequate substitute. The NHANES has some attractive features: a national probability sample, the continuing collection of blood, the availability of other health and personal information on each subject, and a strong, broad staff that is already skilled in many relevant disciplines and techniques. Other strengths include the probability estimates of various features of the U.S. population that might have health significance or be useful in looking at health risk factors, and a priority toxicant reference-range study being conducted as part of NHANES III in collaboration with the Agency for Toxic Substances and Disease Registry. The study is to determine background concentrations of 50 priority toxicants, primarily volatile chemicals and phenols, in 1,000 people with no known excessive exposures. Subjects are being selected by age, sex, and geographic region. Urban-rural status will be considered. (See Appendix D for a more complete discussion of the NHANES.) A combination of four other features, however, seems fatal to the use of the NHANES for the present purpose: The national need is for regular, continuing sampling of human tissues, whereas the NHANES is periodic (recently at intervals of 5–10 years). That is not often enough to identify new trends rapidly. The NHANES has in the past been slow in providing results to sponsoring agencies (personal communications and workshop presentations), whereas a properly functioning monitoring program should provide results quite promptly—indeed, substantially more promptly than the present NHMP. Blood taken for the purpose of human monitoring must be in substantial volume (probably 200 cm3 or more), and such a volume could not be added to the 150 cm3 NHANES already collects.

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Monitoring Human Tissues for Toxic Substances The NHANES has, properly, a range of competing goals, and those goals might change from time to time in response to changing perceptions of national needs in ways that would not support tissue monitoring. Thus, the NHANES cannot have a primary commitment to NHMP goals and is not suitable vehicle for human tissue monitoring. Agency for Toxic Substances and Disease Registry: National Exposure and Disease Registries The Agency for Toxic Substances and Disease Registry (ATSDR) was created and directed by Congress to implement the health-related provisions of three laws that are designed to protect the public from adverse health effects of hazardous substances: the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, amendments to the Resource Conservation and Recovery Act of 1984, and the Superfund Amendments and Reauthorization Act of 1986. The agency has developed 10 programs to aid in the implementation of its congressional mandates. Three of the programs (in health assessments and health studies, toxicologic profiles, and exposure and disease registries) are to evaluate the adverse human health effects and diminished quality of life resulting from exposure to hazardous substances in the environment. Although ATSDR has been considered as a possible parent agency for a new human tissue monitoring program (Chapter 7), it does not have in-house capability to collect and assay human tissues. Therefore, trans-ferring the NHMP to ATSDR would be equivalent to, rather than an alternative to, planning a new program. National Institute of Standards and Technology: Environmental Specimen Banking Program The National Institute of Standards and Technology (NIST) carries out environmental-specimen banking and archiving. The specimen-banking activities include continuing cooperative efforts with the National Oceanic and Atmospheric Administration (NOAA). Approximately 10 years ago, NIST (then known as the National Bureau of Standards) began collaboration with EPA to determine the feasibility of long-term storage of environmental specimens. The EPA Office of Research and Development and Office of Health Effects Research funded a pilot environmental-specimen banking program.

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Monitoring Human Tissues for Toxic Substances NIST’s approach was to gain experience in the various aspects of specimen banking, including collection, storage, and analysis. Although the program was initially intended to focus on four kinds of samples—human, marine, food, and air samples—funds have been available only for the study of human tissues and, to a smaller extent, marine samples (e.g., in cooperation with NOAA). Collection and banking of human liver specimens began in late 1979. More than 550 specimens have been collected for trace elements and organic pesticides, and PCB measurements are available for about 100 of these samples. NIST clearly is capable of directing the development of human tissue monitoring programs and could contribute substantially to improving the technology of sample collection, storage, and assay. However, routine monitoring programs do not appear compatible with NIST institutional goals. The cost constraints and requirements for maximal numbers of samples to be assayed would, in the opinion of this committee, present an insoluble conflict with other NIST priorities and functions. Environmental Protection Agency: Total Exposure Assessment Methodology Study EPA has carried out the Total Exposure Assessment Methodology (TEAM) study to measure the personal exposures of 600 people to particular chemicals that were selected on the basis of their toxicity, carcinogenicity, mutagenicity, production volume, presence in preliminary sampling and pilot studies, and amenability to collection on Tenax. The subjects were selected to represent a total population of 700,000 residents of cities in New Jersey, North Carolina, North Dakota, and California. Each participant carried a personal air sampler throughout a normal 24-hour day and collected 12-hour daytime and 12-hour overnight urine samples. Identical samplers were set up near some participants’ homes to measure ambient air. Each participant also collected two drinking-water samples. At the end of the 24 hours, each participant contributed a sample of exhaled breath. The air, water, and breath samples were analyzed for 20 target chemicals. The products of a rejuvenated national tissue monitoring program would be highly complementary to such studies of exposure dynamics. The EPA personnel and organizational units that have been associated with TEAM studies might well be candidates for involvement in a successor NHMP. However, TEAM studies themselves are not an alternative to national human tissue monitoring. The series of detailed portraits of exposure (principally to organic vapors) represented by TEAM studies are distinct from the long-term tissue monitoring snapshots that would be provided by an updated National

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Monitoring Human Tissues for Toxic Substances Human Monitoring Program. Some of the key differences are the populations represented, the chemical agents addressed, and the exposure time scale represented by biologic samples. Food and Drug Administration: Total-Diet Study The Food and Drug Administration (FDA) monitors the U.S. food supply for pesticide residues, toxic elements (including heavy metals), and industrial contaminants. The objectives of the program have varied over time, but enforcement of the pesticide tolerances established by EPA and determination of the incidence and concentrations of chemical residues in food are of primary concern. Continuing studies are directed toward those objectives. For example, FDA has carried out a large-scale monitoring program for pesticide residues since the early 1960s. The program has two principal approaches: a commodity monitoring program to measure residues in specific domestic and imported foods and to enforce tolerances and other regulatory limits and a total-diet study to measure the intake of pesticides in foods prepared for consumption. The Total-Diet Study (also called the Market Basket Study) would not serve as a substitute for tissue monitoring, given other important sources of exposures and the incompleteness of present information regarding the biologic fate and diversity of chemicals that might be found in the diet. The totaldiet study, like the TEAM study, would complement a national program for tissue monitoring, but it is not a substitute. National Oceanographic and Atmospheric Administration: National Status and Trends Mussel Watch Program The National Status and Trends program has specific, well-defined goals to quantify the spatial distribution and long-term temporal trends of contaminants in the marine environment. The goals are accomplished by an annual collection of bivalves, livers of bottom-feeding fish, and surface sediments in coastal and estuarine areas of the United States. NOAA’s NS&T Mussel Watch collects specimens from 150 sites around the United States, and the NS&T Benthic Surveillance Program collects specimens from 50 other sites. NIST is responsible for the quality assurance of organic analyses; quality assurance for measurements of trace elements is handled by the National

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Monitoring Human Tissues for Toxic Substances Research Council of Canada. There is also a specimen banking component of the National Status and Trends program, which is carried out with the cooperation of NIST. Environmental monitoring programs in general and marine tissue monitoring data specifically do not address the full scope of objectives of a National Human Tissue Monitoring Program. Foreign Programs The committee reviewed several foreign monitoring programs. A comprehensive program of environmental monitoring that uses human tissues has been developed in Germany. That program and other foreign programs are described in Appendix E. Conclusions The committee concluded that the approach of each of the programs just described plays an important role in the identification and control of hazards to human health. Coordination and cooperation among those programs would benefit researchers, health professionals, and the public; such an effort also would enhance the federal approach to monitoring public and environmental health. However, none of the programs meets all the criteria in Table 2–1. Not all can incorporate new research findings in toxicokinetics, exposure assessment, and risk assessment. Not all can take the place of human tissue monitoring, which should offer over the long-term, unique insights into substances that actually enter human tissues and in what amounts. For example, only some of the other approaches could measure average concentrations of lipid-soluble toxins (such as PCBs and dioxin) or heavy metals (such as lead and mercury) to determine whether any demographic group might have exposures of concern. SUMMARY AND RECOMMENDATIONS After a thorough review of the present NHMP program, the commit tee finds that NHMP is fundamentally flawed in concept and execu tion, and should be replaced in toto.

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Monitoring Human Tissues for Toxic Substances In discussions within this committee, in comments from experts during the workshop and in separate discussions, and in the technical materials we reviewed, the need for a U.S. population tissue monitoring program is supported without reservation. The original goals of NHMP are still valid, especially as the widespread use of chemicals in modern society continues to increase. Every reasonable effort should be made to protect the population from the untoward effects of chemical exposures. A vital part of the protection is an assessment of past and present exposures to pesticides and other potentially toxic chemicals with a new program that takes advantage of the latest developments in analytic chemistry, statistical design, and human health risk assessment and is adequately supported, both financially and managerially. Although the committee is aware that the rapid metabolism of some pesticides and compounds (e.g., dichlorvos, which is difficult to detect in tissues even after high therapeutic doses are given) will prevent exposure determination for all compounds, the program still will provide valuable data on chemical exposures. In summary, the committee recommends that a new program of human tissue monitoring be developed. The committee further recommends that such development be com pleted with dispatch, that NHMP be continued only until there is a successor program, and that the change be completed as soon as is consistent with an orderly transition. Aspects of NHMP that should be preserved and evaluated for continued support include the network for collection of adipose specimens, the tissue archive, and the record of past analyses. Later chapters offer suggestions as to how a new program could be designed to meet the objectives of providing data suitable for the accurate assessment of exposure of both the general population and selected groups to a variety of chemicals likely to be encountered in the workplace, through environmental exposure, or in the food supply.

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