Roles for epidemiology: the impact of environmental chemicals.

Aside from the well-recognized role of documenting the extent of any health impact from exposure to environmental chemicals, epidemiology has other potential roles. Arguing by analogy from the function of epidemiology in the infectious disease field, two practical public health functions are mentioned. The first is rumor abatement: simply characterizing the population exposed and documenting the frequency of salient complaints and providing this to the affected population, so as to separate fact from fiction. Another practical public health function is to review available data bases to document the number of individuals exposed to such chemicals and a review of gross trends by place and time to set public fears in proper perspective. There are important descriptive scientific functions as well, namely, to document any syndromes or symptom patterns which may be associated with chemical exposures and to document the natural history and progression of clinical and preclinical conditions associated with chemical exposures. The sensitivity, specificity and predictive value of tests for preclinical disease are discussed.