Effects of a Polluted Environment Research and Development Needs (1977) / Chapter Skim
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EFFECTS ON HUMAN HEALTH
EFFECTS ON HUMAN HEALTH
Pages 40-63
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From page 40... ...
The kinds cf evidence needed to establish a basis for action include: • identification of causative agents in the environment; • demonstration of adverse effects, such as morbidity cr mortality, in exposed populations; • production of toxic effects ir laboratory animals; and, • reduction or eliminatior of harm when exposure is reduced or ceases, or when the population is protected. Such sequential chains of evidence have been established in scme cases of occupational exposures (for example, to beta naphthylamine and nickel [International Agency for Fesearch on Cancer 1971-1975]
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From page 41... ...
Additional important information can be gained from investigations of the biochemical and physiological mechanisms of action of environmental agents and cf the functional and structural changes a chemical or metabolite may produce in tissues and organs. No one research approach can, by itself, provide adequate information on the potential health effects cf a chemical in the environment; congruent results are needed from both human experience and laboratory studies.
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From page 42... ...
When information on ambient environmental exposures to an agent is unavailable, it is often possible tc study a small population with a history of high exposure, for instance in an occupational environment. The study of such populations can generate valuable qualitative data to guide further investigations.
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From page 43... ...
Institutional Arrangements Epidemiological studies on ervircnmentally-caused diseases will be most effectively conducted through a coordinated effort involving several federal agencies, plus university and other research teams supported by grants and contracts. It is important that the complementary strengths of assorted agencies be used in mutually reinforcing rather than competitive ways.
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From page 44... ...
The possibility that a no-effect level may exist for each potential carcinogen in the environment has not been resolved, and the combined impact on health of simultaneous exposures to many such agents at very low levels is unknown. The uncertainties inherent ir translating experimental data on carcinogens into environmental standards create a critical need for epidemiological research on cancer.
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From page 45... ...
Specific birth defects due to particular environmental agents are unlikely to cccur so often that they will easily be noticed, unless special efforts to discover them are made. Pesponsibility for establishing a national program for the surveillance of birth defects should most reasonably reside with the National Center for Health Statistics and the Center for Disease Control, since these agencies have experience in organizing such efforts.
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From page 46... ...
A few effective tests for mutations in human populations have been developed, but no organized surveillance programs for large populations have been established. A need exists, therefore, to develop further effective techniques for detecting and monitoring mutations in man, and for maintaining surveillance and informati-cn systems.
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From page 47... ...
1c make the most of this opportunity, research is needed or the relationships between behavioral effects and other (often later) toxic consequences, Current clinical neurological tests can detect overt disease, but are inadequate for measuring many more subtle behavioral changes.
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From page 48... ...
If the likely nature of behavioral changes is unknown, a battery of tests may be required. Evidence of behavioral effects drawn from epidemiological studies ought tc be followed by controlled clinical studies of human subjects exposed to the suspected agents, where this is possible.
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From page 49... ...
Epidemiological studies are reeded tc identify populations at high risk of such diseases, either because of intrinsic special sensitivities or because of excessive exposures to1 potential causative agerts. Once identified, such populations should be examined clinically, and toxicological tests should be undertaken to provide additional insights into pathogenesis and tc help identify causative agents.
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From page 50... ...
The determination of the disease status of populations and the unraveling of causative processes should draw on the expertise cf seme of the more specialized units of the Department cf Health, Education and Welfare. TOXICOLOGY Texicological studies involving mammalian, avian, and aquatic species are the cornerstcne of research to determine adverse effects of environmental agents.
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From page 51... ...
Chronic tests for carcinogenicity are not explicitly included among the recommendations here, because we believe that importance of chronic tests for carcinogens with arimal models is clear and does not need to be stressed further. Emphasis should be placed, however, on continued development of short-term bioassays to serve as screens for potential carcinogens, and cn epidemiological studies of environmental factors in carcinogenesis (see above)
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From page 52... ...
EPA as a regulatory agency should conduct screening programs for environmental contaminants, using the best developments that emerge from such research programs. Effects of Exposures tc Mixtures of Agents a risk to_human,,health Very little specific toxicological evidence is available on hazards to human health that result from exposure to low levels of heterogeneous mixtures of contaminants.
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From page 53... ...
Further refinements of the techniques of inhalation tcxicology will be required for investigations of complex mixtures of contaminants. Replication of occupational cr ambient environments for controlled studies is difficult because of the complexities of generating and monitoring multiple contaminants.
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From page 54... ...
Behavioral Effects _behayj.orgl £h§aaes_aad_2ther_me§sures_2f .functional Eehavior depends on the functional integrity of a great many organ systems and metabolic processes. Toxic effects on any of the body's systems, such as the nervous, endocrine, or immune systems, may be expressed in behavioral
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From page 55... ...
Behavioral changes in animals may have significant ecological consequences, through impacts on processes like feeding, reproduction, and predator-prey interactions. Current knowledge suggests that subtle behavioral changes may occur at extremely low dose levels, and thus may be sensitive indicators of toxicity that might be used to detect harmful effects before irreversible damage has been done (NPC 1975b)
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From page 56... ...
Until the meaning of particular behavioral changes is determined, however, uniform testing procedures cannot be developed (Spyker and Avery 1976) , Coordinated multidisciplinary tcxicclogical research is required to determine the correspondence between various functional effects and their behavioral consequences.
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From page 57... ...
It is unlikely that mcst exposures to environmental contaminants will produce such clinically obvious defects; and many subclinical effects may be overtly expressed only later in life, as defects in subsequent maturaticnal processes such as puberty. It is important, therefore, that the evaluation of teratogenic effects of environmental agents include tests for subtle functional impairments and that evaluations be cortinued for an extended postnatal period.
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From page 58... ...
Knowledge of mechanisms of action is extremely important for the inference cf causal relationships. It can also provide early indications of biological effects that could make it possible to detect the initiation of a pathogenic process before overt disease appears, when preventive action or early treatment are possible.
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From page 59... ...
It has been suggested that a small number of metabolic pathways, perhaps fewer than a dczen, are involved in the metabolism of environmental contaminants by livirg systems (Gehring 1975)
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From page 60... ...
. Nevertheless, the answers such studies can provide are very important, and this field should continue to receive substantial emphasis in research planning.
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From page 61... ...
Presented to National Meeting of Comprehensive Cancer Centers cf the United States, Euke University Medical Center, April 9-10, 1975. Curham, North Carolina.
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From page 62... ...
Environmental Studies Ecard, Commission or Natural Resources and Committee cn Toxiciology, Assembly of life Sciences. Washington, E.G.: National Academy of Sciences.
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From page 63... ...
Pages 29-48, Methods for Detection cf Environmental Agents that Produce Congenital Defects, edited by T Shepard, J
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