Animals as Sentinels of Environmental Health Hazards (1991) / Chapter Skim
Currently Skimming:
2. Concepts and Definitions
2. Concepts and Definitions
Pages 33-52
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 33... ...
Animals also can be placed deliberately in an area of special interest to permit collection of data for health assessments, determine the extent of contamination, or determine temporal changes in contamination; for example, animals might be placed at a site that had been contaminated to determine the efficacy of remedial efforts. Animal sentinel systems can include data collection through epidemiologic studies, in situ studies, or food monitoring programs.
|
From page 34... ...
The size of an animal can be important in itself If an animal is large enough, various types of monitoring devices can be attached to transmit radio signals to indicate location, allow determination of whether the animal is alive, or permit collection of data on physiologic characteristics and exposure. A sentinel species must have sufficient population size and density to permit enumeration.
|
From page 35... ...
For example, animals that could be considered as soil monitors include small digging animals, such as earthworms, soil insects, gophers, moles, mice, and voles. The National Contaminants Biomonitoring Program uses starlings to monitor soil contaminants; starlings feed on soil invertebrates and range over wide areas, so they are exposed to contaminants over areas as wide as 10 km.
|
From page 36... ...
Water contamination is best monitored with wholly aquatic organisms. Populations of fish and other aquatic species sometimes are absent from an otherwise suitable habitat when toxic chemicals are present.
|
From page 37... ...
Contamination in human homes can be monitored with domestic animals, such as cats and dogs. Other domestic species such as rabbits, gerbils, hamsters, and caged birds—could also be used, although the committee is unaware of actual examples where studies have been done following intentional exposure.
|
From page 38... ...
The advantage of an animal sentinel system is that it can be used to detect acute structural changes and compare them with functional sequelae. Such an approach certainly is more sensitive than, for instance, using age at menopause as an indicator of reproductive toxicity of smoking or of materials thought to be toxic to ovarian tissue (Mattison, 1985~.
|
From page 39... ...
Moreover, populations of wild animals are influenced by many natural factors that are difficult to control, as well as by the contaminants that are under investigation, and regulation of animal populations involves complex interactions among the various controlling factors. Although changes in animal populations might be an end point of primary interest, it is usually easier to measure physiologic or behavioral effects in individual animals than to determine their population consequences.
|
From page 40... ...
OBJECTIVES OF MONITORING ANIMAL SENTINELS The objectives of monitoring animal sentinels include data collection to aid in the estimation of human health risks, identify contamination of the food chain, determine environmental contamination, and identify adverse effects on animals.
|
From page 41... ...
Observational studies and followup research on numerous environmental and feed-contamination problems in domestic animals enabled investigators to predict probable hazards to human health. For example, aflatoxin Be, a potent carcinogenic mycoto~nn produced by the genus Asper~llus, was first discovered to cause hepatitis X, a severe hepatic degenerative disease, in dogs, cattle, swine, and turkeys fed moldy peanut meal and grains.
|
From page 42... ...
, which inspects poultry and livestock before and after slaughter at establishments whose marketing area are in more than one state; departments of health in various states, which inspect milk that is sold commercially; animal-disease diagnostic laboratories, which have been established in almost every state and assist practicing veterinarians and livestock and poultry producers in diagnosing diseases; the Food Animal Residue Avoidance Database (FARAD) , which is maintained by the USDA Cooperative Extension Service in cooperation with several colleges of veterinary medicine throughout the United States; and the U.S.
|
From page 43... ...
Adverse Elects on Animal Most uses of domestic animals to monitor environmental pollutants have been unplanned byproducts of veterinary services directed at alleviating health problems in the animals involved, rather than organized monitoring programs. Many domestic animals and wildlife are routinely presented to veterinary clinics and diagnostic facilities for clinical examination or necropsy.
|
From page 44... ...
In the flurry of public attention and additional research in the aftermath of Silent Spring, scientists were able to demonstrate further that persistent organochlorine compounds, even when used judiciously, had the potential to cause bird populations to decline and even vanish through the chemical induction of reproductive dysfunctions. In North America, DDT and its metabolite DDE contributed to the endangerment and regional extinction of some species (e.g., bald ~ · r ~ ~ ~ 1~ ~ _ ~ ~ _1 ~__1~ eagle, peregrine falcon, ana grown pelican)
|
From page 45... ...
. In situ studies with animal sentinels often are experimental epidemiologic studies, provided that they incorporate appropriate controls.
|
From page 46... ...
Despite their limitations, human epidemiologic studies are the most reliable basis for estimating the risk of toxicity associated with exposure of humans to environmental agents (Woods, 1979~. Descriptive and analytic epidemiologic methods that can be used to monitor animal populations for environmental health hazards are discussed below.
|
From page 47... ...
or have the power to identify chemicals that cause disease in people but that, owing to methodologic difficulties, are less likely to be identified through human epidemiologic studies. For example, older dogs living in a heavily industrialized urban environment were found, in a descriptive study, to have a higher prevalence of nonspecific chronic pulmonary disease based on chest radiographs than were dogs living in a less-industrialized environment (Reif and Cohen, 1970~.
|
From page 48... ...
Use of animal sentinels in situ can provide information on body burdens or effects that result from small exposures to chemicals in water, air, or soil. They can improve our ability to assess accurately the health risks posed by toxic chemicals, including those at hazardous-waste sites.
|
From page 49... ...
In animal epidemiologic studies (as in human studies) , the ability to approximate the truth depends mainly on rigorous scientific application of accepted epidemiologic methods and analytic techniques that control for confounding and reduce bias.
|
From page 50... ...
That was the idea behind the NIH-sponsored Multiple Risk Factor Intervention Trial, whose ultimate goal was to reduce the incidence of and death rates from coronary arterial disease in the United States. The primary goal of an animal sentinel system is to identify harmful chemicals or chemical mixtures in the environment before they might otherwise be detected through human epidemiologic studies or toxicologic studies in laboratory animals.
|
From page 51... ...
However, these differences can be adjusted with modeling techniques (Andersen, 1987~. Using animal sentinel data as quantitative measures of human exposure is challengin~all the examples cited in this chapter were examples of the use of animal data as qualitative or relative measures of human exposure.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.