Applying Research to Public Health Questions: Biologically Relevant Exposures

doi:10.1289/ehp.1002015 Complex diseases have both genetic and environmental components. Understanding the contribution of environmental factors to disease susceptibility will require a more comprehensive view of exposure and biological response than has traditionally been applied. “Exposure ” is defined as the “contact between an agent and a target” (World Health Organization 2004). For risk assessment, this definition of “exposure ” has been applied primarily to the individual or human population as a target of exposure, and to a chemical as an agent of exposure; however, the target of exposure can be an organ, tissue, or cell, and the agent of exposure can be a biological, physical, or psychosocial stressor or the by‑product of a given exposure agent. Exposure science is required to incorporate consideration of lifestage, genetic susceptibility, and interaction of nonchemical stressors for holistic assessment of risk factors associated with complex environmental disease. Achieving this goal will require the establishment of new capabilities to identify bio‑ logically relevant exposure metrics that can be directly associated with key events in a disease process and with an individual’s exposure profile. Wild (2005) proposed the need for a “step change ” in exposure assessment and articulated a vision for exposure measurement calling for an “exposome, ” or measurement of the life-course of environmental exposures to provide the evidence base for public health decisions to address environmental health. Wild and others (e.g., Weis et al. 2005) discussed the potential of emerging technologies to provide this new generation of exposure information. In their guest editorial in EHP, Smith and Rappaport (2009) argued that if we expect to have any success at identifying the contribution of environmental factors on chronic diseases, “we must develop 21st-century tools to measure exposure levels in human populations ” and quantify the exposome. The National Academy of Sciences committee on Emerging Science fo