Southeast Louisiana is home to a large population of Vietnamese Americans who rely heavily on the shrimp caught in the Gulf for their livelihood and as a food source. When the Deepwater Horizon oil spill happened in in April 2010, Vietnamese shrimpers were particularly concerned. While the U.S. Food and Drug Administration (FDA) conducted risk assessments on seafood contaminant levels and health risks, the Vietnamese community worried that the risk assessment conducted by the FDA did not accurately take into account their much higher levels of shrimp consumption and lower-than-national-average body weight. They were also concerned that the FDA did not source specimens from the key areas where they commonly fished for shrimp.
At the request of a prominent Vietnamese community organization, Dr. Jeffrey Wickliffe, Associate Professor of Global Environmental Health Sciences at the Tulane University School of Public Health and Tropical Medicine, conducted a targeted health risk analysis on the Vietnamese shrimping community and their potential for heightened risk from the Deepwater Horizon spill. He and his colleagues collected key data, including concentrations of PAHs in shrimp; daily shrimp intake rates of surveyed Vietnamese community members; assumed durations of exposure that people had to PAHs; individual’s self-reported body weights; and averaging times (the time used to average out the dose of PAHs). Using @RISK, the model for these inputs was simulated 10,000 times, and a sensitivity analysis was conducted to determine the most influential parameters. The analysis revealed that the concentration of chemicals and the daily shrimp intake rate were the most influential in determining risk levels, however, “The study showed that the shrimp were really low in PAHs overall,” says Dr. Wickliffe. “In fact, the testing did not actually detect any of the known carcinogens.”
Nonetheless, to be extremely conservative in their analysis, Dr. Wickliffe and his team modeled health risks using even more cautious assumptions about the presence and carcinogenicity of the PAHs. It was only under the very most conservative approach that excessive health risks (> 1 in 10,000 at the 99th percentile) were seen, and even then, they appeared only in the extreme upper tail of the modeled risk distribution. While these results are reassuring in terms of the overall health risk posed to the Vietnamese American shrimping community, Wickliffe’s team cautions that this approach is not currently tenable for policy-based chemical risk assessment because of the dearth of knowledge regarding the toxicology of these modeled compounds.
Dr. Wickliffe uses @RISK in all the courses he teaches. “Probabilistic analysis is where the regulatory agencies are going with risk assessments,” says Dr. Wickliffe. “So for students who are getting a degree in public health and environmental health sciences, this is the kind of training they need—they need to know how to conduct this kind of risk assessment.”
Read the full case study here.
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