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

BACKGROUND: 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. METHOD: 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. RESULT: 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. CONCLUSION: 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.

Modes of Transport to School and Their Associations with Weight Status: A Cross-Sectional Survey of Students in Shanghai, China.

Background: Over the past two decades, both transport modes as well as overweight/obesity have changed dramatically among students in China, but their relationships are not clear. This study aimed to investigate modes of transport to school and their associations with the weight status of Chinese students. Methods: A cross-sectional study was conducted with non-resident students aged 6 to 17 years from all 16 districts across Shanghai, China in October and November 2019. Information about sociodemographic characteristics and the models of travel to school among students was investigated using an online, self-administered, structured questionnaire (or those assisted by their parents). Weight and height were measured by school health workers, and the Chinese standard age adjusted BMI (weight/height2) was used to classify students' weight status. Cumulative logistic regression modelling was used to examine the relationships. Results: The main mode of transport to school was an active mode (46.5%, defined as walking, bicycling, or public transport), followed by an inactive mode of transport (30.5%, defined as a car or bicycle as a passenger), and a combination of both modes (23%). About one-third of the students were overweight or obese and 5% were underweight. No statistically significant association between transport modes and weight status was found in this study. Conclusions: In Shanghai, close to one-third of children travel to school by an inactive mode of transport. The findings of this study did not support the notion that an active mode to school could be beneficial for preventing overweight/obesity in students in China.