Mercury is a toxic compound to which humans are exposed by consumption of fish. Current fish consumption advisories focus on minimizing the risk posed by the species that are most likely to have high levels of mercury. Less accounted for is the variation within species, and the potential role of the geographic origin of a fish in determining its mercury level. Here we surveyed the mercury levels in 117 yellowfin tuna caught from 12 different locations worldwide. Our results indicated significant variation in yellowfin tuna methylmercury load, with levels that ranged from 0.03 to 0.82 μg/g wet weight across individual fish. Mean mercury levels were only weakly associated with fish size (R2 < 0.1461) or lipid content (R2 < 0.00007) but varied significantly, by a factor of 8, between sites. The results indicate that the geographic origin of fish can govern mercury load, and argue for better traceability of fish to improve the accuracy of exposure risk predictions.

We assessed mercury (Hg) pollution in China's coastal waters, including the Bohai Sea, the Yellow Sea, the East China Sea and the South China Sea, based on a nationwide dataset from 301 sampling sites. A methylmercury (MeHg) intake model for humans based on the marine food chain and human fish consumption was established to determine the linkage between water pollutants and the pollutant intake by humans. The predicted MeHg concentration in fish from the Bohai Sea was the highest among the four seas included in the study. The MeHg intake through dietary ingestion was dominant for the fish and was considerably higher than the MeHg intake through water respiration. The predicted MeHg concentrations in human blood in the coastal regions of China ranged from 1.37 to 2.77 μg/L for pregnant woman and from 0.43 to 1.00 μg/L for infants, respectively, based on different diet sources. The carnivorous fish consumption advisory for pregnant women was estimated to be 288–654 g per week to maintain MeHg concentrations in human blood at levels below the threshold level (4.4 μg/L established by the US Environmental Protection Agency). With a 50% increase in Hg concentrations in water in the Bohai Sea, the bioaccumulated MeHg concentration (4.5 μg/L) in the fish consumers will be higher than the threshold level. This study demonstrates the importance in controlling Hg pollution in China's coastal waters. An official recommendation guideline for the fish consumption rate and its sources will be necessary for vulnerable populations in China.

More attention was previously paid to adverse effects of steroids on aquatic organisms and their ecological risks to the aquatic environment. So far, little information has been reported on the bioaccumulative characteristics of different classes of steroids in cultured fish tissues. The present study for the first time provided a comprehensive analysis of the occurrence, bioaccumulation, and global consumers’ health risks via fish consumption of androgens, glucocorticoids and progestanges in typical freshwater cultured farms in South China. The numbers and total concentrations of steroids detected in the tissues of five common species of the cultured fish were in the order of plasma > bile > liver > muscle and plasma > bile, muscle > liver, respectively. The field bioaccumulation factors for the detected synthetic steroids ranged from 450 to 97,000 in bile, 450 to 65,000 in plasma, 2900 to 16,000 in liver, and 42 to 2600 in muscle of fish, respectively. This data suggests that steroids are bioaccumulative in fish tissues. Mostly important, 4-androstene-3,17-dione (AED) and cortisone (CRN) were found to be reliable chemical indicators to predict the levels of steroids in plasma and muscle of the inter-species cultured fish, respectively. Furthermore, the maximum hazard quotients (HQs) of testosterone and progesterone were 5.8 × 10−4 and 9.9 × 10−5, suggesting that human health risks were negligible via ingestion of the steroids-contaminated fish.

Mercury (Hg) is a globally-distributed pollutant, toxic to humans and animals. Emissions are particularly high in Asia, and the source of exposure for humans there may also be different from other regions, including rice as well as fish consumption, particularly in contaminated areas. Yet the threats Asian wildlife face in rice-based ecosystems are as yet unclear. We sought to understand how Hg flows through rice-based food webs in historic mining and non-mining regions of Guizhou, China. We measured total Hg (THg) and methylmercury (MeHg) in soil, rice, 38 animal species (27 for MeHg) spanning multiple trophic levels, and examined the relationship between stable isotopes and Hg concentrations. Our results confirm biomagnification of THg/MeHg, with a high trophic magnification slope. Invertivorous songbirds had concentrations of THg in their feathers that were 15x and 3x the concentration reported to significantly impair reproduction, at mining and non-mining sites, respectively. High concentrations in specialist rice consumers and in granivorous birds, the later as high as in piscivorous birds, suggest rice is a primary source of exposure. Spiders had the highest THg concentrations among invertebrates and may represent a vector through which Hg is passed to vertebrates, especially songbirds. Our findings suggest there could be significant population level health effects and consequent biodiversity loss in sensitive ecosystems, like agricultural wetlands, across Asia, and invertivorous songbirds would be good subjects for further studies investigating this possibility.

The Mesel gold mine in the Ratatotok Sub-district operated between 1996 and 2004 with tailings disposal via an engineered submarine tailings placement (STP) into Buyat Bay. This operation raised concerns of increased levels of arsenic (As) and mercury (Hg) associated disease in the local communities from consumption of seafood contaminated with anthropogenic As and Hg. This report uses the dietary exposure to As and Hg, from local fishermen and market-purchased Codex “as consumed” and environmental fish results from the pre-mining baseline (1990–1995), the mine operational (1996–2004) and post-closure monitoring (2007–2016) to examine the potential health effects. The Ratatotok Sub-district consumers total As average daily intake from fish was between 152 and 317 μg/day (adults) and 58 and 105 μg/day (infants). The average daily intake of inorganic arsenic (Asi) from the dietary staples fish and rice and drinking water consumption was 77 μg/day (adults) and 35 μg/day (infants) at Buyat Pantai and 39 μg/day (adults) and 19 μg/day (infants) at Ratatotok township. Fish consumption contributed 8.2% (adults) and 6.5% (infants) to total daily Asi intake. Average Hg intake from fish consumption, exceeded the FAO WHO PTWI for methylmercury (MeHg) for all age and gender groups at Buyat Pantai 4.6 μg/kg bw/wk (adults) and 7.3 μg/kg bw/wk (infants) and for the infants at Buyat village and Ratatotok township (2.5 and 2.8 μg/kg bw/wk respectively). The Manado City consumers had average intakes below the MeHg PTWI. The Hg exceedances resulted from the high fish consumption in coastal communities and not elevated levels of Hg in fish. Hg exposure levels from the pre-mining baseline, Mesel STP operation and post-closure monitoring, confirmed that exceedances were unrelated to the tailings deposited into Buyat Bay.

Sydney Harbour, Australia is contaminated with polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) due to a historical Union Carbide chemical manufacturing facility. We measured levels of PCDD/Fs and dl-PCBs in over 400 seafood samples (covering 20 species) collected throughout Sydney Harbour. Concentrations ranged from 0.1 to 193 pg total TEQ (WHO05)/g wet weight. These concentrations were above those considered safe for human consumption in many cases. Dioxin accumulation varied among species and was associated with life history traits. Mobile species had elevated concentrations throughout Sydney Harbour whereas accumulation in species likely to move less widely was dependent on the distance they were caught from the point source. This large scale study on multiple species of recreationally caught seafood resulted in the implementation of human consumption advisories for recreational fishing based on individual species and distance from point source. In addition, all forms of commercial fishing in Sydney Harbour were banned.

Total mercury (Hg) was measured in coastal fishes from Southern New England (RI, USA), and Hg exposure was estimated for anglers and family members that consumed these resources. Fish Hg was positively related to total length (n = 2028 across 7 fish species), and interspecies differences were evident among legally harvestable fish. Many recreational anglers and their families experienced excessively high Hg exposure rates, which was attributed to the enriched Hg content of frequently consumed fishes. Specifically, 51.5% of participants in this study had Hg exposures exceeding the US EPA reference dose, including 50.0% of women of childbearing years. These results are noteworthy given that Hg neurotoxicity occurs in adults and children from direct and prenatal low-dose exposure. Moreover, this study underscores the need for geographic-specific research that accounts for small-scale spatial variations in fish Hg and dietary habits of at-risk human populations.

Organochlorinated pesticides and Aroclors were measured in the muscle of two edible fish species (gray mullet, sea bream) and blue crab, collected from eastern Mediterranean coast in 2013. The concentration of organochlorinated pesticides (OCPs) and Aroclors in biota samples which were collected at six sites ranged from 1.0–8.6 and 9–47.5 ng g⁻¹ wet weight, respectively. Total DDT concentrations in seafood samples were compared to tolerance level established by the US Food and Drug Administration (FDA); the concentrations were detected below the tolerence level. Health risk assessment was conducted related to the consumption of chemically contaminated seafood. The estimated daily intake of OCPs calculated by using the estimated daily fish consumption in Turkey was far below the acceptable daily intake as established by FAO/WHO. Our data indicated that consumption of blue crab, gray mullet, and sea bream collected from the Mediterranean coast of Turkey could pose “no risk” for human health in terms of OCPs.

Chaohu Lake is the fifth largest freshwater lake in China, which tolerates substantial amount of anthropogenic discharge from surrounding cities that resulting in the degradation of water and damage of aquatic ecosystem. Metal analysis of sediment and aquatic organisms can provide important information on the environmental contamination and potential impact of aquatic food consumption. Thus, the concentrations of Cu, Pb, Zn, Cr, Cd, As, and Hg in sediment and fish from Chaohu Lake were analyzed with inductively coupled plasma mass spectrometry and atomic fluorescence spectrometry. The mean content of Cu, Pb, Zn, Cr, Cd, As, and Hg in the sediment samples were 27.4 ± 6.3, 40.5 ± 12.3, 136.8 ± 65.5, 68.5 ± 9.1, 0.357 ± 0.141, 10.8 ± 1.7, and 0.117 ± 0.049 mg/kg, respectively. The results were compared with background values and evaluation methods, to characterize the potential ecological risk. The concentrations of Cu, Pb, Zn, Cr, Cd, As, and Hg in the fish muscle samples were 1.68–5.31, 0.078–0.31, 15.55–372.98, 0.31–0.93, 0.001–0.033, 0.29–1.03, and 0.04–0.197 mg kg⁻¹ of dry mass, respectively. Most of the concentrations of the studied metals in muscles were found to be below the safe limits; however, the concentration of inorganic As (10% of total As) in two specimens exceeded the maximum allowance in fish. The ecological risk evaluation showed that the metals in sediment posed low to medium risk. The health risk assessment suggested that the consumption of fish from Chaohu Lake is currently safe with respect to the metals.

Mixture of metals and herbicides in rivers may pose relevant risks for the health of surrounding communities. Humans may be exposed to river pollution through intake of contaminated water and fish, as well as irrigated agricultural products. The aim of this study was to assess the human health risks of environmental exposure to metals and herbicides through water and fish intake in the Pardo River. Metals (Al, As, Be, Cd, Cr, Cu, Pb, Mn, Hg, Ni, Tl, Sn, V, and Zn) were analyzed in river water and in edible fish. Herbicides (ametryn, atrazine, diuron, hexazinone, simazine, and tebuthiuron) were analyzed in river water. Seasonal variances were also studied. Aluminum, Cd, Cu, Mn, Pb, and Zn levels in river water were higher than the USEPA benchmarks. Non-carcinogenic risks due to pollutants mixture exposure were above the limit, and carcinogenic risks of As exposure were >10⁻⁶ in the sampling points during the rainy season. Metal levels in fish were lower than the Brazilian legislation and do not pose a threat to public health. Herbicides were detected in four sampling points, with atrazine concentrations (range 0.16–0.32 μg/L) below the Brazilian standard (2.0 μg/L), but above the European Union standard (0.1 μg/L). Considering the water supply needs of cities located in the Pardo River Basin and the persistence of metals and herbicides, the present study indicated that there was a seasonal influence on non-carcinogenic and carcinogenic risks to human health, especially in the rainy season. Studies for water treatment plants implantation should consider the risks of exposure to persistent substances, in order to protect the population.