Estimation of the bio-accessibility of methylmercury from aquatic foods using a PBTK model with an approximate Bayesian computation method in Chinese pregnant women

Fish are the primary source of protein and docosahexaenoic acid (DHA) for pregnant women and children, but methylmercury (MeHg) pollution is the potential hazard of fish consumption. In risk assessments, the bio-accessibility of MeHg is usually assumed to be 100%, which could lead to overestimation of dietary exposure.An existing PBTK model was adapted to estimate parameters of the bio-accessibility based on MeHg exposure data from a cohort of 397 Chinese pregnant women. The posterior distributions of parameters were determined by using the ABC - MCMC. RMSEP and Spearman's rank correlation coefficients (Rho) were calculated to determine the goodness of model fitting. The Monte Carlo analysis was performed for the parameter distributions to estimate the model variability.The median of daily MeHg intake and maternal MeHg levels were 0.018 μg/kg bw and 3.01 μg/kg in the early and middle terms of pregnancy. The estimated bio-accessibility of freshwater fish, marine fish and others were 46.1, 17.3 and 58.2%, separately. The RMSEP improved from 11.18 to 2.54 and the Rho improved from 0.19 to 0.22 after bio-accessibility optimization. The model variability was estimated to be 2.6.The bio-accessibility estimated in this study was comparable to that determined in previous in vitro studies. The optimized model could improve the prediction performance on the MeHg body burden by dietary exposure.