Public health implications of methylmercury in fishery products: contamination levels and dietary exposure in the Italian population

Methylmercury (MeHg) represents one of the most relevant contaminants in fishery products due to its high toxicity and strong bioaccumulation and biomagnification potential. MeHg is frequently detected in seafood and typically accounts for about 80% of total mercury (THg) [1]. However, this proportion varies considerably across species and geographical origins, meaning that reliance on THg alone may lead to either overestimation or underestimation of the risk, highlighting the importance of mercury speciation analysis. Compliance with EU Regulation 2023/915 is also required for public health protection; nevertheless, maximum levels apply to THg, not specifically to MeHg. The study aimed to provide a comprehensive assessment of MeHg and THg contamination levels in commercially relevant fishery products purchased from the Italian market, originating from both the Mediterranean region and other key geographical areas representative of the main national fishery supply chains. A total of 591 fishery products, largely consumed in Italy, including fresh cephalopod mollusks (Octopus vulgaris, L.; Eledone spp; Sepia officinalis, L.; Loligo vulgaris, L.; Todarodes sagittatus, L.), fresh tuna loins (Thunnus albacores. B.), salt-ripened anchovies (Engraulis encrasicolus, L.), and smoked salmon (Salmo salar, L.), were analyzed for THg and MeHg quantification by thermal decomposition–atomic absorption spectrometry [2]. Based on the available consumption data, risk characterization was performed for Italian adolescents, adults, elderly, toddlers, other children, and infants, following deterministic and probabilistic (Monte Carlo) methods. Among the analyzed products, octopus exhibited similar patterns to tuna for MeHg and THg levels, whereas salmon, squids, cuttlefish, and anchovies showed markedly lower concentrations. Statistically significant (p<0.05) differences related to geographical origin were observed in octopus and squid, with Mediterranean specimens showing up to fivefold higher levels than Atlantic samples. Deterministic exposure assessment indicated that average consumption of octopuses and tuna could result in MeHg intakes at or above the Tolerable Weekly Intake (TWI). Considering high consumers and highly contaminated products, Estimated Weekly Intakes (EWIs) exceeded up to six times the TWI. In contrast, squids, cuttlefish, anchovies, and smoked salmon contributed at most 42% to TWI in toddlers consuming flying squid. Probabilistic assessment performed on octopuses and tuna confirmed a cumulative probability of exceeding the TWI up to 81% for toddlers and 74% for other children, confirming the concerns for younger populations. Similarly, for adolescents, adults, and elderly, the probability to exceed the TWI for MeHg resulted up to 45%, 37%, and 45% respectively. The findings of the study reinforce the need for MeHg monitoring in fishery products, extending the focus beyond traditionally contaminated species to include underestimated fishery products like octopus, improving exposure assessment accuracy and strengthening public health protection, especially for vulnerable populations.