Verification of methodologies for estimating human exposure to high levels of mercury pollution in the environment

Abstract

A considerable amount of work has been conducted developing exposure estimate models for quantitative evaluation of Hg intake and human health risks, but few have assessed the applicability and the validity for evaluating the risks posed by Hg in the environment and have achieved very mixed results. The present study focused on verifying the daily Hg intake estimates using exposure estimate models. Deterministic methods and the probabilistic methods (the Monte Carlo) were applied to simulate the daily Hg intake doses which were verified by comparing the estimates to those established from measured Hg concentrations in the hair of 289 participants. The results showed that the single-value deterministic method for simulating Hg exposure levels overestimated the level of risk by a factor of 1.5 when compared with the highest concentration of the Hg observed in the hair of the study population. The average daily Hg intake doses simulated using the probabilistic simulation were similar in distribution to the biomarker data, with the variability of 23%. The difference between the probabilistic simulation and the data derived from hair Hg levels was considered to be most likely due to the uncertainties in unconfirmed questionnaire-based survey data, small sampling sizes and the surrogates used in the exposure models. When the reference dose (RfD) of 0.1 ?g/kg body weight/day was adopted as the acceptable dose for daily intake rate, there were approximately 19% estimated to have potential Hg exposure risks based on the Monte Carlo simulation. This percentage was favourably similar to the 17% determined from Hg concentrations in the hair samples. The findings implied that the existing exposure models together with the probabilistic approach were appropriate for the research of human exposure to Hg. On the other hand, low Hg levels in the participants’ hair indicated that Hg accumulated in the study population was not very serious, probably due to the good Hg absorptivity of the on-site fly ash. However, it should be advised that consumption of river fish elevates the health risks to the local population