Biologic markers of exposure: current status and future research needs.

Biologic markers of exposure have been used successfully in many instances and are potentially useful in future epidemiologic investigations. For exposure markers to realize their full potential, much work still must be done on a marker-by-marker basis to identify properties of markers and to validate their use in human populations. Although properties of some markers, such as cotinine and lead, are well characterized, more research is needed on properties of many molecular and cytologic markers of exposure before they can be employed effectively in epidemiologic research investigations.