Molecular biomarkers and epidemiologic risk assessment

The use of molecular biomarkers in epidemiologic studies has been advanced as a way to improve risk assessments for occupational and environmental exposures to toxic agents. We have used the detection of two cancer-related, molecular biomarkers of vinyl chloride exposure (mutant ras-p21 and mutant p53) to examine workers with equivalent cumulative exposures that would be above or below the current permissible workplace exposure limit for vinyl chloride for differences in the presence of these biomarkers. Workers with cumulative exposures above the current permissible exposure limit (equivalent of > 40 ppm-years) have a statistically significantly increased occurrence of both biomarkers in comparison to unexposed controls (p < 10^-3). Although workers with cumulative exposures of < 10 ppm-years, i.e., well below the current limit, do not have a statistically significantly increased occurrence of these biomarkers (p > 0.05), workers with cumulative exposures of 10 to 40 ppm-years, i.e., still below the current limit, are found to have a statistically significant increase (p < 0.05). This suggests that the current exposure limit may not be adequately protective and illustrates the potential utility of molecular biomarkers in the refinement of risk assessments for toxic exposures.