Benefit-risk assessment of commonly consumed fish species from South China Sea based on methyl mercury and DHA

Species-specific mercury speciation in billfishes and its implications for food safety monitoring and dietary advice

Humans are exposed to toxic methylmercury mainly by consuming marine fish, in particular top predator species like billfishes or tunas. In seafood risk assessments, mercury is assumed to be mostly present as organic methylmercury in predatory fishes; yet high percentages of inorganic mercury were recently reported in marlins, suggesting markedly different methylmercury metabolism across species. We quantified total mercury and methylmercury concentrations in muscle of four billfish species from the Indian and the Pacific oceans to address this knowledge gap. We found low percentages of methylmercury in blue and black marlins (15 ± 7 %) compared to swordfish and striped marlin (89 ± 13 %), with no significant differences among ocean regions. This illustrates that billfishes exhibit species-specific methylmercury bioaccumulation patterns, likely related to unique selenium-dependent in vivo methylmercury demethylation capacities in muscle. Blue and black marlins therefore appeared generally safer for human consumption than swordfish and striped marlin regarding MeHg toxicological effects. Yet, no matter the species, the frequency of recommended weekly billfish meals decreased with increasing fish size, given that mercury naturally accumulates over time. When assessing potential risks of billfish consumption, we therefore recommend measuring methylmercury, rather than total mercury, and relying on a large number of samples to cover a broad range of fish sizes. This study calls for additional characterization of mercury speciation and bioavailability in billfishes to better understand the mechanisms driving species-specific differences of methylmercury detoxification, and to refine dietary advices associated to marine top predators consumption.

Hg bioaccumulation in the aquatic food web from tributaries of the Three Gorges Reservoir, China and potential consumption advisories

The Three Gorges Reservoir (TGR) holds the distinction of being China's largest reservoir, and the presence of pollutants in the fish from the reservoir have a direct impact on the health of local residents. Thus, 349 fish specimens of 21 species and 1 benthos (Bellamya aeruginosas) were collected from four typical tributaries of the TGR from 2019 to 2020. These specimens were analyzed for the concentrations of total mercury (THg) and methylmercury (MeHg), and some representative samples were tested for δ¹³C and δ¹⁵N values to reveal the characteristics of bioaccumulation and biomagnification. The maximum safe daily consumption was estimated based on the oral reference dose (0.1 μg kg^-1 bw/day according to US-EPA, 2017). The results showed that the mean THg and MeHg concentrations in fish from the TGR tributaries were 73.18 ± 49.21 ng g^-1 and 48.42 ± 40.66 ng g^-1, respectively, with the trophic magnification factors (TMFs) of THg and MeHg being 0.066 and 0.060, respectively. Among all the fish species in the tributaries, the highest daily maximum safe consumption amount was 1253.89 g for S. asotus consumed by adults, while the lowest was 62.88 g for C. nasus consumed by children.

Probabilistic benefit-risk analysis of fish: Nutritional benefit versus methylmercury-contaminated risk

This paper carries out probabilistic approach to quantify the benefit-risk analysis for foods (BRAFO) of omega-3 polyunsaturated fatty acid and methylmercury (MeHg) for the people who eat the mercury-contaminated fish in Taiwan. We applied the hazard quotient (HQ) model to assess the risk of developmental neuropsychological impairment effect and the desirable dose index (DI) model to quantify the health benefits. Besides, we also applied the disability adjusted life years (DALY) model to assess the number of years lost by incidence of affected infants' intelligence quotient (IQ) and coronary heart disease (CHD) or Stroke for adult. The results of this study show that although the risk of cod and scad are higher, Taiwan residents do not need to reduce intake rate based on benefit considerations. Furthermore, according to the benefits of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), this study suggests that more intake of saury and salmon.

The burden of mild intellectual disability attributed to prenatal exposure to methylmercury in China, 2017

Methylmercury (MeHg) is a neurodevelopmental toxicant that is widespread in the environment and food. Considering the presence of multiple sources of MeHg exposure in the environment, the burden attributable to different exposure sources needs to be determined. This study aimed to estimate the burden of mild intellectual disability (MID) caused by in-utero exposure to MeHg and identify the attributable burden related to MeHg exposure from different sources in China. We applied the hair mercury concentrations from studies to evaluate the burden of MID associated with maternal MeHg exposure and quantify it by disability-adjusted life years (DALYs). The DALYs attributable to MeHg exposure sources were calculated by combining the total DALYs and the contribution rates of various sources of MeHg exposure. The maternal MeHg exposure resulted in 6504 MID cases and a loss of 63,354 DALYs in China in 2017. The contribution rates of aquatic products and rice were 52.2% and 27.1%, respectively, leading to health losses of 28,115 and 18,011 DALYs. The burden of MeHg-induced MID associated with aquatic products was high in coastal areas. Several sites such as Zhejiang, Hunan, and Guangxi had high DALYs caused by rice MeHg exposure. Regions with high DALYs of MID related to MeHg exposure require more attention. Local governments should establish targeted measures to reduce MeHg exposure, thus preventing health loss.

Risk and benefit assessment of potential neurodevelopment effect resulting from consumption of cultured largemouth bass (Micropterus salmoides) in China

The aim of this study was to evaluate the net effects of dietary consumption on the potential neurodevelopmental effects of largemouth bass (Micropterus Salmoides, simplify as bass) cultured in China, especially when the bait of largemouth bass is changed from iced trash fish to formulated feed. A total of three bait group bass samples were collected from main producing areas during harvest period, including formulated feed group, iced trash fish group, and both group (converting from iced trash fish to formulated feed). Net neurodevelopment value (expressed as intelligence quotient or IQ) was calculated using FAO/WHO deterministic methods and probabilistic assessment model. The results showed net IQ of largemouth bass fed by the three baits groups all showed positive or beneficial neurodevelopmental effects, with the values of 1.55 ± 0.97 (formulated feed group), 3.17 ± 1.76 (iced trash fish group), and 2.65 ± 1.29 (both group) respectively. Bass samples fed with ice trash fish showed the highest neurodevelopmental effect. The present study suggested that more valuable formulated feed should be developed to improve the quality of cultured largemouth bass.

Dietary Exposure of the Taiwan Population to Mercury Content in Various Seafood Assessed by a Total Diet Study

This paper examines the health risks of exposure to methylmercury (MeHg) through the consumption of mercury-contaminated seafood in Taiwan, based on the total diet study (TDS) method. Samples of seafood (n = 140) were purchased at fishing harbors or supermarkets and classified into seven categories (pelagic fish, inshore fish, farmed fish, shellfish, cephalopods, crustaceans, and algae). For each sample, we analyzed raw and cooked versions and compared the concentration difference. Total mercury (THg) was detected at the highest rate and in the highest concentrations in pelagic fish, followed by inshore fish and other farmed fish. The average concentration of THg was higher after cooking. In a 75th percentile scenario, the hazard indices for children aged 1 to 3 years and children aged 4 to 6 years were higher than 100% of the provisional tolerable weekly intake. Taking into consideration the risk assessment results, MeHg concentrations, and the nutritional composition of fish, we have provided weekly consumption advisories for children aged 1 to 3 years, children aged 4 to 6 years, and childbearing women aged 19 to 49 years. The weekly consumption advisories for childbearing women are 35 g/week of pelagic fish and 245 g/week of inshore fish based on the risk results from MeHg and the potential benefits from eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) intake.

Human health risk-benefit assessment of fish and other seafood: a scoping review

Fish and other seafood are important sources of nutrients, but they are also sources of chemical contaminants that may cause adverse health effects. This article aimed to identify existing risk-benefit assessments (RBA) of fish, shellfish, and other seafood, compare methodologies, discuss differences and commonalities in findings, and identify limitations and ways forward for future studies. We conducted a scoping review of the scientific literature of studies in all languages published from 2000 through April 2019. We identified 106 RBA of fish and other seafood across Europe, Asia, North America, Africa, and at the global level. Studies were heterogeneous in terms of types of fish and other seafood considered, beneficial and adverse compounds assessed, and overall methodology. Collected data showed that a diet consisting of a variety of lean and fatty fish and other seafood is recommended for the overall population and that women of childbearing age and children should limit the consumption of fish and other seafood types that have a high likelihood of contamination. Our review emphasizes the need for evidence-based, up-to-date, and harmonized approaches in RBA in general.

Assessing the Potential Health Risk from Mercury Through Consumption of the Most Popular and Preferable Fish Species, Rutilus frisii kutum, on the Northern Coast of Iran

Due to the importance of Caspian kutum (Rutilus frisii kutum) in the nutrition and health of consumers, a study was conducted to evaluate the concentration of mercury and its associated health risk for this species, its predators, and the people. Samples were collected from the fish at the four best-selling stations, Bandar Torkaman, Bander Anzali, Fereydunkenar, and Chalos, with mean mercury concentrations in the samples from the stations being 49.4, 132.6, 103.6, and 107.6 μg/g respectively. Mercury in the muscle tissue of the collected samples increased from east to west in the southern Caspian Basin. The mercury concentrations at all stations were below the permissible international levels for this heavy metal, suggesting no or low potential health risk. However, due to the toxicity and other harmful properties of mercury, it is necessary to monitor the values of this element as well as other pollutants in fish species to assess the health risk.

Quantitative benefit and risk assessment of cadmium and nutrient levels in Chinese mitten crab (Eriocheir sinensis)

The use of Chinese mitten crabs for human consumption is controversial due to their uptake of heavy metals, such as cadmium (Cd). We developed a formula for quantification of benefit and risk assessment (hazard quotient) for the intake of a product containing essential polyunsaturated fatty acids versus heavy metals. A total of 70 samples (2100 individuals) of crabs were collected from 6 representative basins in Jiangsu province to determine Cd levels. Cd levels ranged from 0.028 to 5.015 mg kg^-1, and the levels among the basin regions were similar (p > 0.05). To determine the nutritional differences between crabs fed with iced trash fish and formulated feed, we conducted a comparative aquaculture experiment. We simulated the cultivation conditions of crabs in China and found that the nutritional content in the trash fish group (28.724 ± 2.301 mg kg^-1) was significantly higher than in the formulated food group (19.278 ± 3.556 mg kg^-1; p < 0.05). The differences in the hazard quotient of benefit and risk balance between these two diets were not significant (p > 0.05). The average hazard quotient of iced trash fish feed culture was 0.023 ± 0.019, compared with the formulated feed culture (0.034 ± 0.028). Formulated feed and iced trash fish produce similar results as culture food for the Chinese mitten crab. In terms of cadmium exposure risk, the appropriate daily consumption of crabs is less than eight. These data can help justify culture using formulated food and the sustainable development of the Chinese mitten crab industry.

Mercury, microcystins and Omega-3 polyunsaturated fatty acids in farmed fish in eutrophic reservoir: Risk and benefit assessment

Fish is an important source of nutritional omega-3 (n-3) polyunsaturated fatty acids, but it also readily accumulates toxic mercury (Hg) and microcystins (MC) in eutrophic aquatic systems. In China, farmed fish was widely consumed, and aquaculture has caused pervasive eutrophication of freshwater lakes, resulting in the increasing accumulation of MC in fish tissue. To assess the risk-benefit of consuming farmed fish, 205 fish samples of 10 primary species were collected from the eutrophic Wujiangdu (WJD) Reservoir, SW China. The contents of Hg, microcystin-RR (MC-RR), microcystin-LR (MC-LR), and polyunsaturated fatty acids (PUFA) in fish were analyzed. The results showed that THg and MeHg concentrations in all fish sampls were well below the safety limit (500 ng/g w.w) established by the Standardization Administration of China, with average values of 22.9 ± 22.8 and 6.0 ± 6.6 ng/g wet weight (w.w.), respectively. Average concentrations of MC-RR and MC-LR were 40 ± 80 and 50 ± 80 ng/g w.w., respectively. MC-RR and MC-LR concentrations in fish were significantly higher in silver carp and black carp than in perch and catfish (p < 0.05). In nutritional terms, average concentrations of n-3 PUFA and the eicosapentaenoic (EPA) + docosahexaenoic acids (DHA) of fish were 2.0 ± 2.5 and 1.4 ± 0.5 mg/g w.w., respectively. The risk-benefit assessment suggests that the n-3 PUFA benefits from consuming all farmed fish species in the WJD Reservoir outweigh the adverse effects of MeHg. However, except for perch, most fish species still pose a high MC-LR exposure risk that created a requirement for fish consumption advisories and monitoring. Consequently, more attention should be paid on the health risk of combined exposure to pollutants by aquatic product consumption.

Mercury concentration and fatty acid composition in muscle tissue of marine fish species harvested from Liaodong Gulf: An intelligence quotient and coronary heart disease risk assessment

Marine fish species are an important source of biologically valuable proteins, fats, fat-soluble vitamins, and n-3 polyunsaturated fatty acids, but they are also susceptible to pollutants. Mercury is liable to bioamplify in the aquatic food chain, and the health risks posed by methylmercury (MeHg) could undermine the benefits of eating fish, so risk-benefit assessments are needed for those fish species regularly consumed. The purpose of this study was to analyze the concentrations of mercury and characteristics of fatty acids in marine fish harvested from Liaodong Gulf, China, so as to better understand the risk-benefit effects of marine fish consumption. We found that the ratio of MeHg to total Hg (THg) was normally distributed. The concentrations of THg and MeHg in marine fish muscles (14 species, a total of 239) ranged from 0.920 to 0.288 μg/g and 0.050 to 0.192 μg/g, respectively. There were no significant interannual differences in the muscles' concentrations of MeHg and THg, or of their fatty acids (p > 0.05). The proportion of total saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs) varied significantly among different marine fish-feeding habits (predacious, omnivorous, benthivorous and planktivorous), but the differences between polyunsaturated fatty acids (PUFAs) were not significant, which may be due to the undistinguished fatty acids (p < 0.05). The risk-benefit assessment using the intelligence quotient (IQ) scoring model revealed that all the studied marine fish had positive effects on child IQ under different consumption scenarios. Additionally, the integrated risk-benefit analysis for adult cardiovascular health showed that all the studied marine fish, but especially Ditrema temmincki Bleeker, are capable of reducing the relative cardiovascular risk posed by the MeHg in the fish. We conclude the positive effects of eating common marine fish from the Liaodong Gulf far outweigh their negative ones.