Abstract
Epidemiological studies of community populations are highly relevant to the process of setting national ambient air quality primary standards, as criteria for those standards are the protection of human populations against adverse effects on health. Nevertheless, because of the difficulties of performing adequate community population studies of a quality commensurate with the needs of standard setting, the use of data derived from studies is problematic. This paper addresses the important issues of appropriate exposure assessment and health assessment, and discusses the problems of multiplex variables and colinearity as they are critical in assessments of exposure-effect relationships. It is concluded that a major problem in the use of data from such studies for standard setting is not necessarily one of scientific reliability or validity, but arises from the attempt of translating adequate science into policy decisions.