Bioaccessibility and bioavailability of methylmercury from seafood commonly consumed in North America: In vitro and epidemiological studies

Abstract

Methylmercury (MeHg) is a global contaminant of concern and human exposures are largely realized via seafood consumption. While it is assumed that 95 to 100% of the ingested MeHg from seafood reaches systemic circulation, recent in vitro studies have yielded results to suggest otherwise. Of the published studies to have characterized the bioaccessibility or bioavailability of MeHg from seafood, only a handful of seafood species have been characterized, there exists tremendous variability in data within and across species, few species of relevance to North America have been studied, and none of the in vitro studies have adapted results to an epidemiology study. The objective of the current study was two-fold: a) to characterize in vitro MeHg bioaccessibility and bioavailability from ten commonly consumed types of seafood in North America; and b) to apply the bioaccessibility and bioavailability data from the in vitro study to an existing human MeHg exposure assessment study. Raw seafood samples (cod, crab, halibut, salmon, scallop, shrimp, tilapia, and three tuna types: canned light, canned white, fresh) were purchased in Montreal and their MeHg concentrations generally overlapped with values reported elsewhere. The bioaccessibility of MeHg from these samples ranged from 50.1±19.2 (canned white tuna) to 100% (shrimp and scallop) of the amount measured in the raw undigested sample. The bioavailability of MeHg from these samples ranged from 29.3±10.4 (crab) to 67.4±9.7% (salmon) of the value measured in the raw undigested sample. There were significant correlations between the initial MeHg concentration in seafood with the percent of that Hg that was bioaccessible (r= -0.476) and bioavailable (r=-0.294). When the in vitro data were applied to an existing MeHg exposure assessment study, the estimated amount of MeHg absorbed into systemic circulation decreased by 25% and 42% when considering bioaccessibility and bioavailability, respectively. When the in vitro data were integrated into a regression model relating dietary MeHg intake from seafood with hair and blood Hg biomarkers, there were no differences in key model parameters when comparing the default model (that assumes 100% bioavailability) with models adjusted for the in vitro bioaccessibility and bioavailability data. In conclusion this work adds to a growing number of studies that together suggest that MeHg bioavailability from seafood may be less than 100%, but also documents the challenges when integrating such in vitro data into human exposure and risk assessments.

Methylmercury Concentration in Fish and Risk-Benefit Assessment of Fish Intake among Pregnant versus Infertile Women in Taiwan

“…), salmon (0.014 ± 0.013 mg/kg wet wt), and tilapia (0.016 ± 0.012 mg/kg wet wt.) [ 27 ]. Levels of MeHg in Tuna were 0.78 ± 0.91 mg/kg wet wt.…”

A Review of Mercury Bioavailability in Humans and Fish

“…Some of the studies investigated only a single type of seafood (e.g., Costa et al [49] only investigated salmon), while others investigated many types of seafood [50,51,52]. Some studies investigated only a few types of seafood, but also investigated how different ways of cooking these seafoods affected Hg bioaccessibility relative to raw samples of the same seafood [53,54].…”

The aging kidney and the nephrotoxic effects of mercury

“…The most common route of human exposure, however, is via the ingestion of food, primarily fish, contaminated with MeHg (Nunes et al 2014; 2014; Wolff et al, 2016; Lopez-Barrera and Barragan-Gonzalez, 2016). The flesh of large predatory fish, such as northern pike, swordfish, shark, and some species of tuna may contain high levels of CH 3 Hg + and represents a major source of Hg exposure (Siedlikowski et al 2016; Burger and Gochfeld 2011). Upon ingestion, MeHg is absorbed readily by the gastrointestinal tract (Vazquez et al 2013; 2014) following which, mercuric ions enter systemic circulation and are delivered to target organs.…”