Comparison of a toxicokinetic and a questionnaire-based approach to assess methylmercury intake in exposed individuals

Abstract

Methylmercury (MeHg) is a neurotoxic contaminant and one of the main sources of exposure in humans is seafood consumption. It is thus of interest to assess precisely MeHg exposure. The objective of this study was to estimate MeHg daily intake in exposed individuals using two different approaches, a food questionnaire and toxicokinetic modeling, and compare the complementary and use of each method. For this purpose, a group of 23 fishermen from northern Quebec provided blood and hair samples and answered a standard food questionnaire focusing on seafood consumption. A published and validated toxicokinetic model was then used to reconstruct MeHg daily intakes from mercury (Hg) measurements in biological samples. These intakes were compared to those estimated using a standard food questionnaire on seafood consumption. Daily intakes of MeHg from seafood (mean/median (range)) estimated from hair concentrations with the toxicokinetic-based approach were 6.1/5.2 (0.0-19) mg/day. These intake values were on average six times lower than those estimated using a food questionnaire, that is, 49/32 (7.2-163) mg/day. No correlation was found between the toxicokinetic-based and the questionnaire estimates of MeHg daily intakes. Most of the MeHg intakes estimated with the food questionnaire (21/23) exceeded the US EPA RfD of 0.1 mg/kg bw/day, whereas only a small proportion (6/23) of modeled estimates exceeded the RfD. This study shows that human health risk estimates strongly depend on the chosen approach.

Human Health Risks Derived from Dietary Exposure to Toxic Metals in Catalonia, Spain: Temporal Trend

“…With respect to Cd, the current dietary intake in male adults was similar to or lower than those recently found for other countries: 11.0 μg/day in France [26], 49 μg/day in Sweden [28], 14.6 μg/day in China [24], and 9.8 μg/day in Belgium [30]. In turn, Hg and MeHg dietary intakes in male adult were similar to those reported by Noisel et al [25] (6.1 μg/day of MeHg), Arnich et al [26] (7.7 μg/day of Hg), or Cheng et al [29] (13.1 and 3.23-23.3 μg/day, respectively) in Canada, France, and Cambodia, respectively. Finally, the Pb dietary intake in Catalan male adults is lower than intakes recently found in other countries, such as France (14.07 μg/day) [26] or China (13.00 μg/day) [31].…”

“…A comparison of the results of the present study with those reported by other authors shows that our data are very similar or even lower than those previously reported [23][24][25][26][27][28][29][30][31]. Thus, As and InAs dietary intakes in male adults in Catalonia are of the same order than those found in various countries, i.e., InAs 3.8 μg/day in Japan [27], As 55 μg/day and InAs 17 μg/day in France [26], or As 285 μg/day in Belgium [23].…”

Insights from mercury stable isotopes into factors affecting the internal body burden of methylmercury in frequent fish consumers

“…By contrast, the mean measured Hg concentration in hair was 0.76 µg g -1 and only 19% of individuals exceeded the level approximately equivalent to the U.S. EPA RfD (Figure 2). Similar overestimates have been observed in earlier studies on Japan, France, Quebec and indigenous populations in Northern Canada (Gosselin et al, 2006;Loranger et al, 2002;Noisel et al, 2011;Sirot et al, 2008). Linear regression of mean measured hair Hg levels against a variety of predictors reveals significant and positive associations with MeHg intake from seafood consumption and age, and a negative association with body weight (Table 3).…”

“…However, many studies find self-reported fish and shellfish consumption can only weakly explain measured variablity in Hg concentrations in hair and blood (Golding et al, 2013;Lincoln et al, 2011;Mahaffey et al, 2004;McDowell et al, 2004). Prior studies of frequent seafood consumers in Japan (Canuel et al, 2006), France (Sirot et al, 2008), Quebec (Loranger et al, 2002;Noisel et al, 2011), and indigenous populations in northern Canada (Gosselin et al, 2006) have all reported extremely low measured concentrations of Hg in hair and blood relative to ingested MeHg and correspondingly modeled internal concentrations (mean 4-14 fold difference). Despite the consistency in these results, such discrepancies are normally attributed to dietary recall bias and imprecision in exposure biomarkers (i.e., integrated signal of MeHg exposure measured in hair) rather than differences in the pharmacokinetics of MeHg metabolism across individuals (Gosselin et al, 2006;Grandjean and Budtz-Jørgensen, 2010;Sirot et al, 2008;Tsuchiya et al, 2008;Zhang et al, 2009).…”

Collate the literature on toxicity data on mercury in experimental animals and humans (Part I – Data on organic mercury)

“…A similar study was performed by Noisel et al (2011): 23 Canadian fishermen provided hair and blood samples which were analysed for total Hg. The toxicokinetic model of Carrier was used to estimate the underlying MeHg exposures and these results were compared to exposures estimated by questionnaire.…”