Mercury Contamination in the Northeastern United States: Science-Based Decision Making About Fish Consumption

Mercury contamination poses a known threat to human health, yet the degree of contamination and resulting human exposure remains unknown in many regions. Assessments of the relative risks of fish consumption are fundamentally limited by the availability of data characterizing fish consumption behaviors in a given region and the mercury concentrations in fish consumed by humans, as well as by a lack of scientific consensus about how a given level of mercury exposure is likely to affect a particular fish consumer. Existing mercury data and research findings are often not accessible to fish consumers or communicated clearly and consistently. This thesis integrates two related, yet distinct, perspectives regarding how the availability of scientific information affects decision making about the consumption of mercury-contaminated fish through a focused study of the fish consumption and mercury exposure of one community of Adirondack anglers, as well as through a broader consideration of how data collection efforts can best provide information to protect human health. This effort had two overall goals: (1) to characterize how the collection, interpretation, and communication of mercury data influence the availability and clarity of information for decision making about fish consumption; and (2) to recommend how data collection, risk assessment, and risk communication efforts can foster informed, science-based decision making about fish consumption. The first part of this research effort builds upon ongoing assessments of mercury contamination by integrating available local, regional, and national fish mercury datasets with participant consumption records to estimate the mercury exposure of fish consumers (N=17), particularly anglers and families consuming fish species sport-caught from privately owned fishing preserves in the Adirondack region. We compared exposure estimates to measured mercury concentrations in participant hair samples and to recommended health guidelines. The estimated mercury exposure of 35% of participants exceeded the USEPA reference dose for methylmercury; 35% of measured hair mercury concentrations exceeded recommended levels, and the estimated mercury exposure and measured hair mercury concentrations of 29% of participants exceeded both guidelines. Fifty years of angling catch records showed a noticeable decrease in the percentage of the total catch kept for consumption rather than caught and released; this change in angling behavior is estimated to have reduced the mean mercury exposure of our study community from preserve sport-caught fish (e.g., from the waters of private Adirondack fishing preserves alone) by 84%. In the second part of this thesis, we review recent efforts to collect and integrate fish mercury data in the northeastern United States, a region that is particularly influenced by atmospheric deposition of mercury, and provide suggestions to improve and focus future research and monitoring efforts to better address threats to human health. Resource and sampling limitations have hindered comprehensive understanding of mercury in the environment and relative levels of methylmercury exposure through fish consumption. Because of these limitations, data collection should maximize the benefits of information gained by monitoring programs. By selecting appropriate target species - those species and sizes of fish harvested for consumption and those with the highest and most variable mercury concentrations at a given location - health and fisheries professionals can more comprehensively advise fish consumers and inform the protection of human health. Overall, the findings from this study will inform our understanding of: (1) how the availability and clarity of mercury information influence decision making about fish consumption, and (2) how a more comprehensive approach to data collection can more clearly characterize the relative risks to anglers and their families and thereby foster informed, science-based decision making about fish consumption