Toxicity of dietary methylmercury to fish: Derivation of ecologically meaningful threshold concentrations

Abstract

Threshold concentrations associated with adverse effects of dietary exposure to methylmercury (MeHg) were derived from published results of laboratory studies on a variety of fish species. Adverse effects related to mortality were uncommon, whereas adverse effects related to growth occurred only at dietary MeHg concentrations exceeding 2.5 µg g(-1) wet weight. Adverse effects on behavior of fish had a wide range of effective dietary concentrations, but generally occurred above 0.5 µg g(-1) wet weight. In contrast, effects on reproduction and other subclinical endpoints occurred at dietary concentrations that were much lower (<0.2 µg g(-1) wet wt). Field studies generally lack information on dietary MeHg exposure, yet available data indicate that comparable adverse effects have been observed in wild fish in environments corresponding to high and low MeHg contamination of food webs and are in agreement with the threshold concentrations derived here from laboratory studies. These thresholds indicate that while differences in species sensitivity to MeHg exposure appear considerable, chronic dietary exposure to low concentrations of MeHg may have significant adverse effects on wild fish populations but remain little studied compared to concentrations in mammals or birds.

Biomagnification of mercury through the food web of the Santos continental shelf, subtropical Brazil

“…Only 2 individual samples of the guitarfish had THg levels (1.74 and ) higher than this limit. However, a recent review on the effect of dietary MeHg on fish indicated adverse effects on reproduction as well as histological, biochemical, and genetic effects at concentrations below 0.2 µg g −1 wet weight (Depew et al 2012). Some samples composed of large individuals of guitarfish, fat snoot, largehead hairtail, Patagonian flounder, and barbel drum from the Santos region had Hg concentrations of that magnitude; however, the health impact on these species at the population level is difficult to assess.…”

Effects of Inorganic Mercury and Methylmercury on Osteoclasts and Osteoblasts in the Scales of the Marine Teleost as a Model System of Bone

“…As mentioned above, muscle in fish is the main edible part, and it accumulates MeHg (Depew et al, 2012). In largemouth bass, the total mercury concentration in muscle was highly correlated with that of scales (r = 0.89) (Lake et al, 2006), indicating the importance of examining the interaction between mercury exposure and bone metabolism in fish.…”

“…Hg 0 has been shown to be oxidized to inorganic mercury (InHg) in aquatic environments, and particularly easily in seawater (Yamamoto, 1996). InHg is convertible to methylmercury (MeHg) in natural environments, and most of the mercury in fish tissue has been reported to be MeHg (WHO, 2008;WHO, 2010;Depew et al, 2012). The toxicokinetics (absorption, distribu-tion, metabolism, and excretion) of mercury are highly dependent on the form of mercury (WHO, 2008;WHO, 2010).…”

Mercury environmental quality standard for biota in Europe: Opportunities and challenges

“…An EQS for biota also automatically accounts for Hg bioavailability issues, thus greatly increasing the possibility to identify situations requiring risk management during routine monitoring programs. Depew et al (2012) derived a threshold concentration of 40 ng g À1 wet weight for reproductive effects in fish following dietary exposure to meHg. Besides protecting piscivorous organisms, the proposed EQS is therefore amenable to application for the protection of prey fish.…”

“…As to the other possibilities, application of the EQS to invertebrates will protect forage fish against dietary Hg exposure (Depew et al 2012), but EQS for piscivorous wildlife and forage fish may not be interchangeable. Finally, the choice of including Hg in the list of UPBT would shift focus from the national to the global scale, thus reducing efforts to target important local issues.…”