William H. Farland, Colorado State University

William Farland addressed the need to examine complex chemical exposures in terms of a combination of exposures, rather than one chemical at a time. Exposure stressors can alter biology, leading to adverse effects. As exposures impinge on normal biology, there is a continuum from exposure to disease that occurs against a backdrop of variability in terms of both the exposure and a particular population’s susceptibility to disease. Depending on those two variables, exposure may ultimately overcome the body’s natural coping mechanisms, leading to adverse effects. According to Farland, although a primary goal of the public health response to the Gulf oil spill should be to prevent exposure, it may nonetheless be possible to manage and mitigate adverse effects when exposures do occur by gaining a better understanding of “source-to-receptor” pathways (i.e., the multiple pathways and environmental fates of potential toxins).

Farland indicated that the pathways to human exposure are complex, and multiple sources of exposure are possible in the context of the oil spill. But the potential for toxins to enter the food supply is a particularly important issue to consider in the Gulf. Understanding the source-to-receptor pathways in the Gulf, including toxicity in the food supply, will require gathering several types of data through various types of monitoring activities, including food, air, and water sampling.

Farland addressed some of the complexities of monitoring. For instance, effective air sampling must account for the differences between crude oil, weathered oil, and products of incomplete combustion. In this regard, air sampling conducted by both the EPA and local agencies (see Chapter 4) should be a rich source of air-sampling data on which to draw. Because there are local populations of subsistence hunters and fishermen and -women, food sampling should involve not just seafood testing but also creel surveys and game monitoring. With respect to water sampling, while it is unlikely that contamination will move far enough inland to affect underground water systems, it is important to ensure that disposal plans for various items (e.g., used personal protective equipment) do not contaminate local wells.

Farland summarized what he thought were the key challenges to assessing the Deepwater Horizon exposure situation, such as the need to consider aggregate and cumulative exposures, including previous expo-

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