Animals as Sentinels of Environmental Health Hazards (1991) / Chapter Skim
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Executive Summary
Executive Summary
Pages 1-18
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Sentinel systems can be designed, for example, to reveal environmental contamination, to monitor contamination of the food web, or to investigate the bioavailability of contaminants from environmental media; these types of systems can be designed to facilitate assessment of human exposure to environmental contaminants. Other sentinel systems can be designed to facilitate assessment of health hazards resulting from such exposure; e.g., systems can be designed to provide early warning of human health risks or can involve 1
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The committee considered the gaps in existing data that need to be addressed if animal sentinel data are to be used in human risk assessment and discussed issues of coordination between programs and standardization of data collection, analysis, and reporting. The committee explored the potential use of animal sentinels in determining risks to human populations posed by environmental contaminants, with special care to determine whether in situ and natural-exposure studies could supplement traditional laboratory studies or help to remove difficulties in risk assessment, such as problems in exposure assessment, and could be helpful in evaluating exposures to and effects of complex mixtures that are difficult to assess in the laboratory.
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Under appropriate conditions, the use of domestic and wild animals can help to reveal the presence of unknown chemical contaminants in the environment before they cause harm to humans or to help identify the amount of exposure to known chemical contaminants. Domestic and wild animals share the human environment and are in the human food web, so sentinel systems can help to identify acute and chronic health hazards caused by contaminants in air, soil, water, and food.
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Three primary strengths are noteworthy: · Many animals share environments with humans, often consuming the same foods and water from the sources, breathing the same air, and experiencing similar stresses imposed by technologic advances and human conflicts. · Animals and humans respond to many toxic agents in analogous ways, often developing similar environmentally induced diseases by the same pathogenetic mechanisms.
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Exposure Sources Sources of toxic substances that can be monitored with sentinel animals include soil, air, plants, water, and human habitats. A sentinel species should have a close association with the source of interest.
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If an animal is to function as a sentinel, biologic responses must be observed soon after exposure. Therefore, changes in ordinarily measured biologic characteristics, such as the hematologic profile and serum chemical values, probably are more generally useful end points than are reproductive characteristics, mutagenesis, teratogenesis, or neoplasia.
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and allow for prospective prediction of human risk. Objectives of Monitoru~gAnirr~ Sentinels Among the many objectives of monitoring animals sentinels are data collection to estimate human health risks, identify contamination of the food chain, determine environmental contamination, and identify adverse effects on animals themselves.
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In addition, sentinel animals might be more susceptible to agents to which they and humans are exposed. Multifactorial Causality Disease usually results from a series of highly complex events involving multiple, heterogeneous environmental insults occurring over a broad range of individual susceptibilities.
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Because food animals are part of the food chain, they are monitored for biologic or chemical contaminants in numerous programs. All the programs can generate descriptive epidemiologic studies—data usually are collected on animals that are not intentionally exposed to biologic or chemical contaminants.
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, it can be difficult to estimate their exposure with conventional procedures of measuring ambient concentrations of the contaminants and calculating their intakes from the contaminated media. One approach to solving the problem is to use animals exposed in the same environments as surrogate monitors; tissues of the animals are taken for analysis and used to provide an integrated measure of the animals' exposure.
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ANIMAL SENT7MEI5 IN RISK ASSESSMENT The assessment of risk due to environmental contaminants depends, to a large extent, on scientific data. When such data are incomplete, as is often the case, assumptions based on scientific judgments are made to calculate potential exposures and effects.
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Thus, the use of animal sentinels constitutes an approach to identifying hazards and estimating risks in circumstances similar to those in which actual human exposures occur, and can complement or provide an alternative to traditional chemical toxicity testing through standardized laboratory studies. Data obtained in studies of animal sentinels also can lead to insights into human health by stimulating epidemiologic studies of humans exposed to agents that might not have been previously identified as potentially hazardous.
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Program integration could yield efficient use of resources if specimens for multiple purposes or archiving specimen material from monitoring programs for analysis when new contaminants are discovered or improved analytic methods are developed. Another form of program coordination is to integrate data from animal sentinel programs with data from traditional environmental sampling.
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Input from relevant government agencies, industry, and academic institutions will be required, if animals sentinel programs are to be more usefully developed and operated. The committee offers the following recommendations for the use of animal sentinels in risk assessment: · Animal diseases that can serve as sentinel events to identify environmental health hazards for humans or to indicate insults to an ecosystem should be legally reportable to appropriate state or federal health agencies.
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· Increased emphasis should be given to research into development of comlative relationships that reduce the uncertainty in animal to human extrapolations and how animals sentinels should be used in the risk-assessment process. · Support for academic courses and graduate programs in epidemiology at colleges of veterinary medicine and colleges of biologic sciences should increase, and emphasis should be placed on the development of methods for the use of animal exposure and disease data in human and environmental health risk assessment.
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Observational studies including outbreak investigations, analytic epidemiologic investigations, and in situ studies are reviewed and illustrated for the populations of food animals, companion animals, and fish and wildlife. The use of animal sentinel systems specifically in risk assessment is considered in Chapters 6 and 7, which focus on selection and application of animal sentinels for components of qualitative and quantitative risk assessment.
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From page 17... ...
Animals as Sentinels of Environmental Health Hazards
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Key Terms
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