The Mediterranean Sea is worldwide acknowledged as a mercury (Hg) hotspot, due to the presence of relevant cinnabar settlements on the coastal shores and of the historical related mining and industrial activities discontinued in the last decades, only (UNEP, 2002). Methylmercury (MeHg) originates from inorganic Hg biomethylation in the marine sediments and bioaccumulates in the seafood. Mediterranean wild seafood species from FAO 37 fishing area show total Hg (HgTOT) and MeHg levels higher than those reported from other FAO zones (Brambilla et al., 2013, FAO and WHO,, 2011). As environmental pollutant, MeHg exerts neurotoxic effects on the human central nervous system, particularly for exposures within the first months of the foetal development (Grandjean and Landrigan, 2006). Fish and seafood give the most relevant contribution in the dietary exposure to MeHg in high and frequent consumers and in general population, as well (EFSA, 2012).
A Tolerable Weekly Intake (TWI) of 1.3 ng/kg body weight (bw) has been recently proposed for MeHg by the European Food Safety Authority (EFSA, 2012) on the basis of multiple epidemiological studies that observed adverse effects in children as consequence of maternal exposures. Other Agencies, in Japan, USA, New Zealand, Australia, UK, and Canada indicate MeHg Reference Doses (RfD) ranging from 0.10 to 0.47 ng/kg bw per day, based on multiple endpoints (Mahaffey et al., 2011). As complementary risk management measures, Maximum Residue Limits (MRLs) for HgTOT in seafood have been issued: for instance, the European Commission (EC) fixed in the 0.5–1.0 mg/kg range the MRL for low/top predatory fish (EC, 2006); moreover, the release of dietary recommendations to most vulnerable groups, on geo-referenced basis, has been suggested to European Union National Authorities by EFSA, as already done by other Agencies (Ser and Watanabe, 2012, Ström et al., 2011, Us EPA, 2004).
In biomonitoring studies, a strong correlation was found between HgTOT concentration in human hair and fish consumption (Diez et al., 2008). Furthermore, according to Bellanger et al. (2013) human hair mercury concentrations are higher in Southern Europe and lower in Eastern Europe: a relevant part of susceptible individuals such as women in the reproductive age may be overexposed via seafood intake with potential consequences on pre-natal/perinatal brain development and a potential IQ reduction in the progeny. The association between prenatal mercury exposure and infant neurodevelopment in coastal areas of four Mediterranean Countries has been recently demonstrated by Valent et al. (2013). However, inconsistencies have been reported among MeHg daily intakes when computed starting from Food Frequency Questionnaires (FFQs) accounting for inventoried HgTOT/MeHg occurrence in seafood (external dose), or when derived from the one-compartment toxicokinetic model from human biomonitoring data of MeHg in blood and hair (internal dose) (Gosselin et al., 2006, JECFA, 2004). Noisel et al. (2011) found that on a group of 23 fishermen, the MeHg intake estimated with FFQs exceeded the US EPA RfD of 0.1 μg/kg bw per day in 21 subjects, against a smaller proportion (6/23) when computed on internal dose. Similarly, an overestimation of the intakes derived from FFQs compared to those recovered from the biomonitoring data has been reported by Sirot et al., 2008, Ström et al., 2011, Valent et al., 2013.
Apart from the intrinsic uncertainties of the toxicokinetic modelling, as those generated from differences in MeHg concentrations between cord and maternal blood and/or from deviations from the steady-state, a possible source of bias in FFQ estimates may rely on the attribution of the proper MeHg occurrence to each seafood species, and on the seafood consumption habits when not broken down into species-specific details (EFSA, 2012, Miklavĉiĉ et al., 2013, Pouzaud et al., 2010). An overestimation of the intake of a contaminant through seafood consumption by means of FFQs might also stem from the fact that people generally tend to over report their life habits or activities that are known to be ‘‘healthy” or to have a positive effect (e.g., consumption of fish) (Männistö et al., 1996). Anyway, FFQ based estimates do not involve human blood or hair collection and analysis, with related ethical and financial issues, thus are a less expensive and less time-consuming methodology and should be ranked among the most cost-effective screening tools able to highlight a potential MeHg overexposure in individuals. In the present work we illustrate the outcomes of the MeHg intake assessment from a Seafood Frequency Questionnaire (SFQ) based on 45 seafood items administered to 278 adults living on the Italian Mediterranean shore. The aim is both to identify those habits able to reduce the risks associated to local seafood consumption thus maximizing the correlated benefits, and to identify, with a presumed reduced rate of false positivity, potentially overexposed individuals.
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