Toxicology and Epidemiology - Strengths and Limitations.
NIOSH 1985 May:25 pages
The strengths and limitations of toxicology and epidemiology were discussed. Epidemiology can be regarded as a study of human experience under conditions that are controlled as well as circumstances permit. It represents an attempt to examine in an orderly and careful manner the effects of potential risk factors on humans through selected observations. Toxicology represents controlled laboratory experimentation where presumably the variables can be controlled in advance. Although humans are not necessarily excluded from toxicological studies, there are major ethical considerations that limit their use. The relevance of tests on animals or isolated species to human exposures can be uncertain because of species differences or other factors. Epidemiological studies are directly related to human experience; however, exposures cannot be as carefully defined and confounding factors as readily controlled as in laboratory animal studies. The sensitivity of toxicology studies is routinely poor because the size of the animal population is severely restricted. The sensitivity of epidemiological studies is frequently poor also, but under certain conditions, using large study populations can improve the sensitivity. Biological mechanisms of action can be easily investigated in laboratory animals whereas ethical considerations limit such studies in humans. Using surrogate systems such as in- vitro biochemical studies of tissues and enzyme and tissue extracts can provide useful information on biological mechanisms and to a certain extent replace whole animals. Examples of laboratory animal studies used to clarify the results of epidemiological studies were discussed. These include induction of thyroid adenomas by therapeutic irradiation, identifying the probable causal agents in chromate induced lung cancer, and elucidating the role of bis(chloromethyl) ethers in bronchogenic cancer. The author concludes that toxicology can be used as an adjunct to epidemiological investigations.
In-vivo-studies; Laboratory-animals; Risk-analysis; Health-hazards; Laboratory-testing; Malignant-neoplasms; Lung-cancer; Occupational-health; Biostatistics;
Infectious Diseases; Disease and Injury;
Proceedings of a Symposium on Epidemiology and Health Risk Assessment, Columbia, Maryland, May 14-16, 1985, Centers for Disease Control/NIOSH, 25 pages, 19 references