Relationship between total mercury concentration and fish size in two pelagic fish species: implications for consumer health

Total mercury, methylmercury, and selenium concentrations in blue marlin Makaira nigricans from a long-term dataset in the western north Atlantic

Mercury in seafood is a neurotoxicant that threatens human health. Dynamic rates of mercury emission, re-emission, and atmospheric deposition warrant studies into mercury concentrations in fish because many are consumed by humans and can serve as sentinels of mercury levels in the environment. We modeled trends in total mercury content in an apex marine fish predator, Atlantic blue marlin Makaira nigricans, whose muscle tissues were opportunistically sampled from North Carolina (USA) sportfishing tournaments over a discontinuous time period: between 1975 and 77 and 1998-2021 (n = 148). The model-estimated influence of marlin weight on total mercury concentration was constant across years (shared slope) allowing for comparisons of weight-corrected mercury concentrations among years. Weight-corrected total mercury concentrations revealed an inter-decadal decline of approximately 45 % between the 1970s and late 1990s and then variable but relatively stable concentrations through 2021. The mean (SD) wet weight concentration of total mercury was 9.47 (4.11) from 1975 to 77 and 4.17 (2.61) from 2020 to 2021. Methylmercury and selenium were measured on a subset of fish to address questions related to human health and consumption. Methylmercury levels (mean = 0.72 μg/g) were much lower than total mercury (mean = 4.69 μg/g) indicating that total mercury is not a good proxy for methylmercury in Atlantic blue marlin. Selenium, examined as a Se:Hg molar ratio and as a selenium health benefit value (HBV_Se), showed high protective value against mercury toxicity. Long-term trends in the concentration of mercury in blue marlin should continue to be monitored to determine whether policies to mitigate anthropogenic contributions to global mercury are achieving their intended goals and to provide information to inform safe human consumption.

Lifelong mercury bioaccumulation in Atlantic horse mackerel (Trachurus trachurus) and the potential risks to human consumption

Atlantic horse mackerel is one of the most commercially important species in Europe. It can reach a longevity of 30 years, with potential implications in lifespan mercury contamination. This study conducted along the Portuguese coast aimed at evaluating the total Hg content and tissue distribution, to determine the annual mercury bioaccumulation patterns and the associated risk for consumption. The T-Hg accumulation patterns observed followed the order: muscle (0.34) > liver (0.28) > heart (0.19) > gills (0.11) > brain (0.041 mg kg^-1). Significant differences between tissues reflect the role of the different tissues in storage and redistribution. Significant relationships observed between age and T-Hg for all tissues highlight the continuous nature of the bioaccumulation process. European food safety guidelines signalled significant risk of consumption in about 30% of the samples. Still, there was an overall low risk from the consumption of this species, which can be further minimized through consumer options to avoid health issues.

Mercury and selenium levels in archive samples of wild Atlantic bluefin tuna from the Mediterranean Sea

This study examined total mercury (THg) and selenium (Se) levels in archive samples (white and red muscles, liver, gills) of the wild Atlantic bluefin tuna (ABFT) (Thunnus thynnus) (n = 18) captured in the central Adriatic Sea. The influence of fish size, age, and tissue type on element distribution was examined. There were significant differences in THg and Se levels, and Se:THg molar ratios among tissues. THg levels were highest in liver and lowest in gills (liver > red muscle > white muscle > gills), while Se levels were also highest in liver but lowest in white muscle (liver > red muscle > gills > white muscle). Se:THg molar ratios were highest in gills (22-82), intermediate in liver (11-29) and red muscle (7-36), and lowest in white muscle (1.7-7.6). Concentrations of THg in all tissues and Se in liver and caudal muscle were positively correlated with tuna age and size, while the Se:THg molar ratio in gills and all white muscles was negatively correlated with tuna age and size, indicating that the protective role of Se against THg is reduced in older specimens. The selenium health benefit values (HBV_Se) were above zero in all tissues, indicating a small excess of Se after Hg sequestration. However, since the obtained HBV_Se for edible tissues were near zero (0.01-0.04), and more than 70% of white muscle samples and all red muscle samples exceeded the EU regulatory limit for THg in fish muscle, it would be advisable to limit their intake in adults to one meal per month.

Accumulation of Trace Metals in Indigenous Fish Species from the Old Brahmaputra River in Bangladesh and Human Health Risk Implications

In this study, accumulation of the top six most toxic trace metals (Arsenic (As), Cadmium (Cd), Chromium (Cr), Mercury (Hg), Nickel (Ni) and Lead (Pb)) were assessed in six indigenous fish species (Barilius barila, Salmostoma acinaces, Gudusia chapra, Labeo bata, Corica soborna, and Sperata aor) collected from the Old Brahmaputra River in Bangladesh. Human health risk associated with these fish consumption was also evaluated. Metals were analyzed in whole body of fish by an atomic absorption spectrometer (AAS). Mean concentrations of metals (μg/g, wet weight) were in the range of As (< 0.02-0.278), Cd (< 0.002-0.005), Cr (0.239-0.761), Hg (0.008-0.057), Ni (< 0.02-0.044), and Pb (< 0.01-0.038). The metal contents varied significantly among the fishes regarding their feeding habits and living habitats. Concentrations of As, Cr, Hg, and Pb were significantly higher in omnivorous species, whereas the benthopelagic species showed significantly higher accumulation of As (p < 0.05). The target hazard quotient (THQ) for noncarcinogenic risk and target cancer risk (TR) for carcinogenic risk were calculated to estimate the probabilities of experiencing these adverse health effects for the fish consumers. Metal-specific THQ values were all below 1 indicating no potential human health risk. Nonetheless, the hazard index (HI) values to estimate the effects from exposure to all metals collectively elucidated chronic noncarcinogenic health risk particularly from G. chapra consumption. The TR values revealed that there was carcinogenic risk from exposure to As through consumption of the fish. This study finally suggests a systematic and continuous monitoring of trace metal contamination in fishes from the river to ensure the fitness of this food item regarding the safety for human health.

Mercury and selenium in fish from the eastern part of the Adriatic Sea: A risk-benefit assessment in vulnerable population groups

The study examines the levels of total mercury (Hg) and selenium (Se) in the muscle tissue of 12 commercially important fish species (n = 717) from 48 locations in the eastern Adriatic Sea, as a function of fish species, size and habitat. Risks and benefits of fish consumption regarding Hg and Se in children (7 years) and women of reproductive age (30 years) were also evaluated. All samples but one were compliant with the European regulatory limit for Hg in fish muscle. Concentrations (μg g^-1 ww) of Hg (range: 0.014-1.37) and Se (range: 0.184-1.12) and Se:Hg molar ratios in fish were associated with habitat type. Demersal species had the highest Hg and the lowest Se concentrations, while pelagic species had the lowest Hg concentrations, highest Se concentrations and Se:Hg molar ratios. All species had Se:Hg molar ratios above 1 (range: 1.4-66.9) and a selenium health benefit value (HBV_Se) above zero (range: 3.3-9.3), indicating Se excess after Hg sequestration. The intake of two meals per week of small pelagic-neritic and bento-pelagic fish is estimated to be a valuable source of essential Se, and does not pose a risk from toxic Hg exposure in children and women during the vulnerable reproductive period. Due to the low Hg and favorable Se:Hg molar ratio and HBV_Se index, small pelagic species offer a good risk to benefit ratio of fish consumption and could be considered an optimal choice in these sensitive subpopulations.

Prenatal Mercury Exposure in Pregnant Women from Suriname's Interior and Its Effects on Birth Outcomes

Prenatal mercury (Hg) exposure was determined in a sub-cohort of the Caribbean Consortium for Environmental and Occupational Health’s environmental epidemiologic prospective cohort study of pregnant women living in Suriname’s interior. The associations between Hg exposure, low birth weight (LBW, <2500 g) and preterm birth (PTB, <37 weeks) were explored. Correlation analysis, Fisher’s exact test and logistic regression analyses were conducted to evaluate the associations between maternal hair Hg levels and birth weight, LBW and PTB, and between potential confounders, LBW and PTB, respectively. Among 204 singleton births were 198 live births, five stillbirths and one miscarriage. The mean participant age was 26 years; 15.7% of participants had PTBs and 8.1% delivered a child with a LBW. The median hair Hg level was 3.48 μg/g hair. Low hair Hg exposure, based on lowest tertile < 2.34 μg/g, was associated with LBW (OR = 7.2; 95% CI 1.5–35.6; p = 0.015); this association was independent of maternal age, ethnic background, household income and village location, and no correlation was found between hair Hg and PTB. Young maternal age was associated with PTB (RR = 5.09, 95% CI: 1.92–13.85; p = 0.0004) while maternal age was not associated with hair Hg or LBW. The impact of prenatal Hg exposure on pediatric neurodevelopment is currently being evaluated in the infant sub-cohort.

Mercury in aquatic fauna contamination: A systematic review on its dynamics and potential health risks

Mercury is an important pollutant, released into aquatic ecosystems both naturally and by anthropogenic action. This element is transferred to aquatic organisms in different ways, causing potential health risks. In addition, mercury can be accumulated by humans, especially through the consumption of contaminated food. This systematic review aims to present mercury pathways, the major routes through which this element reaches the aquatic environment and its transformations until becoming available to living animals, leading to bioaccumulation and biomagnification phenomena. The key biotic and abiotic factors affecting such processes, the impact of mercury on animal and human health and the issue of seafood consumption as a source of chronic mercury contamination are also addressed. A total of 101 articles were retrieved from a standardized search on three databases (PubMed, Emabse, and Web of Science), in addition to 28 other studies not found on these databases but considered fundamental to this review (totaling 129 articles). Both biotic and abiotic factors display fundamental importance in mediating mercurial dynamics, i.e., muscle tropism, and salinity, respectively. Consequently, mercurial contamination in aquatic environments affects animal health, especially the risk of extinction species and also on human health, with methylmercury the main mercury species responsible for acute and chronic symptomatology.

Mercury Bioaccumulation in Tropical Mangrove Wetland Fishes: Evaluating Potential Risk to Coastal Wildlife

The present study, aimed at observing the total concentration of mercury (Hg) in edible finfish species with an implication to human health risk, was carried out from the Setiu mangrove wetlands on the east coast of Peninsular Malaysia. Out of 20 species observed, the highest Hg concentrations were found among carnivores-fish/invertebrate-feeders, followed by omnivores and carnivores-invertebrate-feeders, while the lowest concentrations in herbivores. The Hg concentrations varied widely with fish species and body size, from 0.12 to 2.10 mg/kg dry weight. A positive relationship between body weight and Hg concentration was observed in particular for Toxotes jaculatrix and Tetraodon nigroviridis. Besides the permissible range of Hg concentration up to 0.3 mg/kg (cf. United States Environmental Protection Agency (USEPA)) in majority of species, the carnivore feeders such as Acanthopagrus pacificus, Gerres filamentosus, and Caranx ignobilis have shown excess amounts (> 0.40 mg/kg flesh weight) that raising concerns over the consumption by local people. However, the weekly intake of mercury-estimated through the fish consumption in all three trophic levels-suggests that the present Hg concentrations are still within the range of Provisional Tolerable Weekly Intake (PTWI) reported by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). Perhaps, a multi-species design for Hg monitoring at Setiu wetlands would be able to provide further insights into the level of toxicity transfer among other aquatic organisms and thereby a strong health risk assessment for the local communities.

Heavy metal content and molecular species identification in canned tuna: Insights into human food safety

Canned tuna in olive oil and in brine of the most popular brands sold in Italian markets were analyzed to verify the authentication of transformed products, with the aim to unveil commercial frauds due to the substitutions of high value species with species of low commercial value, and to assess the health risk of consumers related to cadmium (Cd), lead (Pb) and mercury (Hg) contents. Species authentication was evaluated with amplification of COI DNA barcode and confirmed the declared species. Among tested metals, Hg had the highest concentrations, followed by Cd and Pb. None of the tested samples surpassed the European regulatory limits no. 1881/2006 fixed for Hg and Pb, whereas one batch of canned tuna in olive oil exceeded standard for Cd. Risk for human health was evaluated by the metals daily intake and target hazard quotient (THQ). As a result, Cd and Pb did not exceed the toxicological reference values established by World Health Organization (WHO) and the Environmental Protection Agency (EPA). Conversely, Hg content suggests a consumption no more than once a week and a continuous surveillance of this fishery products for consumer protection.

Assessment of total and organic mercury levels in blue sharks (Prionace glauca) from the south and southeastern Brazilian coast

Mercury occurrence was evaluated in samples of edible muscle tissue of 27 blue sharks (Prionace glauca) caught in the Atlantic Ocean, adjacent to the south and southeastern Brazilian coast, indicating a slight increase in comparison with previous data obtained for the same studied area and being higher than those fish caught at different sites of the Atlantic Ocean. Total Hg concentrations ranged from 0.46 to 2.40 mg kg(-1) with the organic Hg fraction ranging between 0.44 and 2.37 mg kg(-1). A negative correlation between total Hg concentration in muscle tissue and blue shark size was obtained, and 40% of samples analyzed had Hg concentrations higher than 1.0 mg kg(-1) Hg, the maximum concentration permitted in Brazilian predator fish. Data obtained showed that total Hg can be used as a reliable predictor of organic Hg in blue shark muscle because 95 to 98% of the total Hg measured was found to be organic mercury. The wide range of Hg concentrations obtained for our set of samples can be explained by the heterogeneity of sampled population and the large size of the studied area. Given the adverse toxicological effects of Hg on animals and humans, a regular monitoring program of Hg contamination in Brazilian marine ecosystem can be recommended.

Examination of spotted sand bass (Paralabrax maculatofasciatus) pollutant bioaccumulation in San Diego Bay, San Diego, California

The spotted sand bass (Paralabrax maculatofasciatus) is an important recreational sport and subsistence food fish within San Diego Bay, a large industrialized harbor in San Diego, California. Despite this importance, few studies examining the species life history relative to pollutant tissue concentrations and the consumptive fishery exist. This study utilized data from three independent spotted sand bass studies from 1989 to 2002 to investigate PCB, DDT, and mercury tissue concentrations relative to spotted sand bass age and growth in San Diego Bay, with subsequent comparisons to published pollutant advisory levels and fishery regulations for recreational and subsistence consumption of the species. Subsequent analysis focused on examining temporal and spatial differences for different regions of San Diego Bay. Study results for growth confirmed previous work, finding the species to exhibit highly asymptotic growth, making tissue pollutant concentrations at initial take size difficult if not impossible to predict. This was corroborated by independent tissue concentration results for mercury, which found no relationship between fish size and pollutant bioaccumulation observed. However, a positive though highly variable relationship was observed between fish size and PCB tissue concentration. Despite these findings, a significant proportion of fish exhibited pollutant levels above recommended state recreational angler consumption advisory levels for PCBs and mercury, especially for fish above the minimum take size, making the necessity of at-size predictions less critical. Lastly, no difference in tissue concentration was found temporally or spatially within San Diego Bay.

The influence of fish length on tissue mercury dynamics: implications for natural resource management and human health risk

Consumption of fish has well-known human health benefits, though some fish may contain elevated levels of mercury (Hg) that are especially harmful to developing children. Fish length is most often the basis for establishing fishery harvest regulations that determine which fish will ultimately be consumed by humans. It is, therefore, essential to quantify the relationship between fish length and Hg accumulation in regard to harvest regulations for effective fishery and public health policy. We examined this relationship for three sportfish from six lakes across North Carolina, USA. Bluegill (Lepomis macrochirus) had the lowest Hg levels and only the very largest fish in the most contaminated site exceeded the US Environmental Protection Agency (USEPA) Hg screening level. Black crappie (Pomoxis nigromaculatus) had an intermediate level of Hg and larger individuals exceeded the USEPA screening level; however, they tended not to exceed this level before reaching the harvest length limit. Largemouth bass (Micropterus salmoides) exceeded the USEPA screening level at sizes below the fishery length limit in two lakes, leaving only higher risk fish for anglers to harvest and consume. Removing the effects of fish age and trophic position, we found strong positive correlations between Hg and fish length for largemouth bass and black crappie. We suggest public health officials and wildlife managers collaborate to structure fishery regulations and length-based fish consumption advisories that protect consumers from Hg exposure and communicate the relative risk of fish consumption.

Intake of essential minerals and metals via consumption of seafood from the Mediterranean Sea

Edible marine species (fish and cephalopod molluscs) from the Mediterranean Sea were analyzed for their metal content (Hg, Cd, Pb, Cr, Cu, Zn, and Ni). Human health risks posed by these elements via dietary intake of seafood were assessed based on the provisional tolerable weekly intake, reference dose, and recommended dietary allowances. Metal concentrations varied widely among the different organisms, indicating species-specific accumulation. On a wet weight basis, the maximum concentrations of Hg were found in fish (1.56 microg g(-1)), and the maximum concentrations of cadmium were found in cephalopod molluscs (0.82 microg g(-1)), whereas for Pb the concentrations were generally low (fish, 0.01 to 1.18 microg g(-1); cephalopod molluscs, 0.03 to 0.09 microg g(-1)). For the essential metals, cephalopods had higher concentrations (Cr, 0.40 microg g(-1); Zn, 33.03 microg g(-1); Cu, 23.77 microg g(-1); Ni, 2.12 microg g(-1)) than did fish (Cr, 0.17 microg g(-1); Zn, 8.43 microg g(-1); Cu, 1.35 microg g(-1); Ni, 1.13 microg g(-1)). The estimated weekly intake of Cd and Pb indicated increased health risks through the consumption of various seafoods. Conversely, a health risk was ascribed to the intake of Hg from consumption of certain fish, such as albacore (10.92 microg kg(-1) body weight) and thornback ray (5.25 microg kg(-1) body weight). Concerning the essential metals, cephalopod mollusc consumption made an important contribution to daily dietary intake of Cu, Zn, and Ni.

Potential human health risks from metals (Hg, Cd, and Pb) and polychlorinated biphenyls (PCBs) via seafood consumption: estimation of target hazard quotients (THQs) and toxic equivalents (TEQs)

Edible marine species (fish, cephalopod molluscs, crustaceans) from the Adriatic Sea were analyzed for content in heavy metals (Hg, Cd and Pb) and polychlorinated biphenyls (PCBs). Health risks to human via dietary intake of seafood were assessed by the target hazard quotients (THQs) and the toxic equivalent factors (TEFs). Mercury maximum concentrations corresponded to fish (0.07-1.56 microg g(-1)w.w.), followed by cephalopod molluscs (0.10-0.55 microg g(-1)w.w.), and crustaceans (0.27-0.33 microg g(-1)w.w.). Cadmium levels in cephalopods (0.18-0.59 microg g(-1)w.w.) were higher than those in fish (0.01-0.05 microg g(-1)w.w.) and crustaceans (0.02-0.04 microg g(-1)w.w.), while for Pb the concentrations were generally low (fish: ND-1.18 microg g(-1)w.w., cephalopods: ND-0.17 microg g(-1)w.w., crustaceans: ND-0.03 microg g(-1)w.w.). For PCBs, concentrations in fish, cephalopods and crustaceans ranged between 141 and 3,406 ng g(-1)l.w., 190 and 542 ng g(-1)l.w., and 202 and 429 ng g(-1)l.w., respectively. Cd and Pb THQ values as well as estimates of PCB TEQ exposure indicated the absence of health risks through consumption of the various seafood. In contrast, mercury TEQs values due to consumption of certain fish species (albacore, rosefish and thornback ray) indicated that human health risk might be of concern.

Trial for quality control in mercury contents by using tail muscle of full-cycle cultured bluefin tuna (Thunnus orientalis)

Substantial amounts of mercury are usually present in tuna muscle, with levels in excess of 10 times the standard safety value present in some individuals. Inspection of individual fish for mercury content would be desirable but may not be cost-effective. In this study, we tried to establish a low-cost system for checking the mercury content of tuna by using a tail muscle that is usually discarded. The samples used in this experiment were bluefin tuna, cultured in the Fisheries Laboratory of Kinki University (Oshima Experimental Station, Wakayama, Japan). They were raised from eggs spawned in 2002. Ninety-eight individuals, weighing 22.3 to 61.6 kg, were selected between December 2004 and November 2005. In nine individuals, the mercury content of the tail was compared with that of the whole body. The total mercury level was measured using the reduction vaporizing atomic absorption method after acid digestion. Except for the front of the abdomen, where the mercury content was lower (0.490 ppm), the mercury content of other parts of the fish did not differ from that of the tail muscle (0.631 ppm). Therefore, the overall mercury concentration in bluefin tuna could be estimated to be almost the same and/or lower than that of the tail muscle. On the basis of these results, for 1 year we investigated the quantity of mercury in full-cycle cultured bluefin tuna that were shipped. The mercury concentration showed no increase irrespective of increases of body weight.