Risk Assessment's New Era: part 2: Evolving Methods and Future Directions.

For more than three decades, health practitioners and regulatory agencies have used risk assessment methods to characterize health risks. Risk assessment is the process of determining the likelihood and severity of health risk to an individual or population from exposure to a chemical or other stressor.1,2 Evolving methods and advances in science and technology offer several opportunities for improving risk assessment and its application to occupational settings. Cumulative Risk Assessment (CRA) Broader in scope than traditional chemical risk assessments, CRAs determine which chemicals, stressors or other risk factors are affecting certain populations. They address multiple chemical and non-chemical stressors, aggregate exposures and risks (that is, exposure to a single stressor by multiple routes), and combined risks for common health end points by chemical or stressor groupings.3,4 The EPA framework for conducting CRAs involves planning, scoping and problem formulation; analysis; and interpretation and risk characterization.5,6 This framework has been applied to CRAs of chemicals, such as organophosphate pesticides and phthalates. In addition, EPA has developed various models and web-based tools to assess aggregate and cumulative exposures and risks.7,8 The greatest strength of CRAs is their emphasis on multiple exposures (stressors) and health effects in varied populations. But it's challenging to identify common groups and develop common metrics to evaluate dissimilar risks, and because of gaps in data and methodological limitations, CRAs have yet to include non-chemical stressors or focus on occupational exposures. Biomonitoring Biomonitoring assesses human exposure by measuring chemicals or their metabolites in human tissues or fluids (blood and urine, for example). This method quantifies the amount of a chemical that has been absorbed into the body from all potential sources. Biomonitoring data are discussed in terms of biomarkers, which are commonly divided into three categories: biomarkers of exposure, biomarkers of effect and biomarkers of susceptibility.9 But the collection of bio monitoring data-which involves selecting a target population, identifying chemicals and biomarkers, collecting and analyzing samples, and interpreting the results-can be challenging. Many population-based biomonitoring efforts are under way. For example, a national survey conducted by the CDC measures numerous chemicals and their metabolites in a representative sample of the U.S. population. The findings are published periodically and represent one of the largest publicly available biomonitoring datasets.10 Biomonitoring data integrates exposures from multiple sources and pathways to provide a direct measure of total exposure and is, therefore, a powerful tool for assessing aggregate exposure and risk. This data can be used to assess trends in exposures over time, evaluate the effectiveness of exposure-reduction policies, provide direction for future research and help medical professionals diagnose people who have potentially been exposed to excessive amounts of chemicals. Collecting and analyzing biomonitoring data requires significant resources, so only a limited number of people, compounds and body fluids have been studied to date. Also, these data provide no information on exposure conditions, such as frequency, duration, magnitude of exposures or the exposure routes that contributed to the total measured body burden.