Person: Li, Miling
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Li
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Miling
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Li, Miling
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Publication Decadal Changes in the Edible Supply of Seafood and Methylmercury Exposure in the United States(Environmental Health Perspectives, 2018) Sunderland, Elynor; Li, Miling; Bullard, KurtBackground: Methylmercury (MeHg) exposure is associated with adverse effects on neurodevelopment and cardiovascular health. Previous work indicates most MeHg is from marine fish sold in the commercial market, but does not fully resolve supply regions globally. This information is critical for linking changes in environmental MeHg levels to human exposure in the U.S. population. Objectives: We used available data to estimate the geographic origins of seafood consumed in the United States (major ocean basins, coastal fisheries, aquaculture, freshwater) and how shifts in edible supply affected MeHg exposures between 2000–2002 and 2010–2012. Methods: Source regions for edible seafood and MeHg exposure in the United States were characterized from national and international landing, export and import data from the Food and Agricultural Organization of the United Nations and the U.S. National Marine Fisheries Service. Results: Our analysis suggests 37% of U.S. population-wide MeHg exposure is from mainly domestic coastal systems and 45% from open ocean ecosystems. We estimate that the Pacific Ocean alone supplies more than half of total MeHg exposure. Aquaculture and freshwater fisheries together account for an estimated 18% of total MeHg intake. Shifts in seafood types and supply regions between 2000–2002 and 2010–2012 reflect changes in consumer preferences (e.g., away from canned light meat tuna), global ecosystem shifts (e.g., northern migration of cod stocks), and increasing supply from aquaculture (e.g., shrimp and salmon). Conclusion: Our findings indicate global actions that reduce anthropogenic Hg emissions will be beneficial for U.S. seafood consumers because open ocean ecosystems supply a large fraction of their MeHg exposure. However, our estimates suggest that domestic actions can provide the greatest benefit for coastal seafood consumers. https://doi.org/10.1289/EHP2644Publication Assessing Sources of Human Methylmercury Exposure Using Stable Mercury Isotopes(American Chemical Society (ACS), 2014) Li, Miling; Sherman, Laura S.; Blum, Joel D.; Grandjean, Philippe; Mikkelsen, Bjarni; Weihe, Pál; Sunderland, Elynor; Shine, James P.Seafood consumption is the primary route of methylmercury (MeHg) exposure for most populations. Inherent uncertainties in dietary survey data point to the need for an empirical tool to confirm exposure sources. We therefore explore the utility of Hg stable isotope ratios in human hair as a new method for discerning MeHg exposure sources. We characterized Hg isotope fractionation between humans and their diets using hair samples from Faroese whalers exposed to MeHg predominantly from pilot whales. We observed an increase of 1.75‰ in δ202Hg values between pilot whale muscle tissue and Faroese whalers’ hair but no mass-independent fractionation. We found a similar offset in δ202Hg between consumed seafood and hair samples from Gulf of Mexico recreational anglers who are exposed to lower levels of MeHg from a variety of seafood sources. An isotope mixing model was used to estimate individual MeHg exposure sources and confirmed that both Δ199Hg and δ202Hg values in human hair can help identify dietary MeHg sources. Variability in isotopic signatures among coastal fish consumers in the Gulf of Mexico likely reflects both differences in environmental sources of MeHg to coastal fish and uncertainty in dietary recall data. Additional data are needed to fully refine this approach for individuals with complex seafood consumption patterns.Publication Environmental Origins of Methylmercury in Aquatic Biota and Humans(2016-05-03) Li, Miling; Sunderland, Elsie M.; Shine, James P.; Hammitt, James K.; Coull, Brent A.Methylmercury (MeHg) is a neurotoxin found in fish and shellfish, that poses risks to human and ecological health. Exposure to MeHg adversely affects neurodevelopment of children and cardiovascular health in adults. Seafood consumption is the primary exposure route to MeHg in North America. An understanding of the link between environmental MeHg sources and human exposures is needed to determine the impacts of ongoing environmental change. However, few data exist for relating environmental exposures to human health outcomes. Imprecision in dietary recall data on fish consumption and variability in MeHg concentrations within and across seafood species consumed have made it challenging to accurately identify sources of human MeHg exposure. In addition, the diverse environmental sources of MeHg production in ecosystems make it more difficult to quantitatively attribute human exposures to specific environments where methylation is taking place. My doctoral dissertation uses naturally occurring mercury (Hg) stable isotopes to characterize sources of MeHg exposure in aquatic biota and human populations. The objectives of my work are to (1) explore the utility of Hg stable isotopes in human hair as a novel method for tracing sources of MeHg exposure to humans; (2) examine drivers of the internal body burden of MeHg in frequent seafood consumers; (3) refine understanding of environmental MeHg sources for estuarine fish. My first dissertation chapter characterizes the magnitude of mass-dependent fractionation between seafood and consumers and shows Hg stable isotopes in human hair is a promising tool for estimating different Hg exposure sources (e.g., coastal vs. oceanic fish). My second chapter uses dietary survey data and Hg isotopes in hair from high-frequency seafood consumers to show that differences in in vivo demethylation do not explain variability in biomarker concentrations. I infer that absorption efficiencies for MeHg in seafood are very low for some high-frequency fish consumers and hypothesize that this is caused by interactions with co-ingested foods. The last chapter investigates diverse Hg stable isotope signatures in benthic, riverine and pelagic estuarine fish and uses these signatures to better characterize the relative importance of different environmental MeHg sources.