OPPORTUNITIES FOR THE DEVELOPMENT AND USE OF BIOMARKERS

Limitations in understanding the relationship between occupational and environmental exposures and disease present opportunities for using b iological markers to fill gaps in knowledge. Three situations can be i dentified that could foster the development and use of biomarkers, whe re epidemiological evidence is (1) definitive, (2) equivocal, and (3) lacking. When there is clear epidemiological evidence of disease risk given an exposure, biomarkers could be used to identify high- and low- risk subsets of a cohort that might benefit from differential practice s such as counseling about job risks, varying frequency and intensity of medical surveillance, and using protective equipment. Biomarkers co uld also be used to test the effectiveness of environmental controls. Assessment of blood lead in bridge workers and purified protein deriva tive (PPD) testing in health care workers illustrates biomarkers that have been used to evaluate control efforts. When epidemiological evide nce is equivocal, a broad and consistent database on intermediate biom arkers in the path between exposure and disease could provide a compel ling case as to whether a substance should be treated as hazardous. Th e case of ethylene oxide illustrates this situation: the epidemiologic al evidence of risk of lymphohematopoietic cancer is equivocal but the re is an informative database on genetic and cytogenetic changes in va rious species consistent with carcinogenicity. Biomarker data also can be used to assist in the interpretation of inconclusive epidemiologic al information as is illustrated in the case of styrene where markers provide a mechanistic rationale for the epidemiologic findings. When t here is little or no epidemiological evidence of risk in an exposure s ituation, such as around hazardous waste operations or with new techno logies, biological markers can serve as early warning indicators of ex posure or risk. In such cases it is important to have an underlying bi ological theory and an appropriate epidemiological study design if the principal results are to be of value in indicating risk and preventin g disease.