Study On The Health Risk Assessment Of Mixtures From Reclaimed Water Based On PBPK Model

With the wide application of reclaimed water and more concerns on its health risk, the health risk of the mixed pollutants in reclaimed water drawn more attention. Therefore, this paper aims at studying on the human health risks via exposure to mixtures from the use of reclaimed water in toilets. This study was implemented by the screening of hazardous substance, the indoor volatilization model of pollutants, toxicology, physiologically based pharmacokinetic?PBPK? models, risk assessment and so on.Firstly, according to the long list of risk factors, water samples from the J water reclamation plant in Tianjin were monitored periodically. Then seven indexes including volatile, acute toxicity, chronic toxicity and so on were selected as the scoring categories, and comprehensive score method was applied to ranking the pollutants from the long list. And chloroform, bromodichloromethane, dibromochloromethane and bromoform were identified as the final risk factors according to the above results.Secondly, according to the existing researches, the indoor volatilization model of pollutants was established to estimate the risk factors concentrations transferred from reclaimed water to toilet indoor air during toilet flushing. And the exposure dose of each risk factor in vitro was calculated according to the inhalation pathway exposure dose assessment.Thirdly, on the basis of the existing achievements, the PBPK of mixtures of the above risk factors was built to estimate the internal dose of each risk factor to reflect the pharmacokinetic interaction between the mixtures.Finally, associating with the internal dose, the health risk assessment method of mixtures according to PBPK was applied to estimate the health risk of mixtures in the reclaimed water while toilet flushing. And the uncertainty and sensitivity were analyzed using the Crystal Ball based on Monte Carlo Method. Additionally, risk control measures were put forward according to the results of the health risk assessment.The results showed that the health risk of mixtures from the use of reclaimed water in toilets ranged from 2.24×10^-6 to 2.00×10^-5, and the risks were greater the acceptable risk level(10^-6). What's more, bromodichloromethane and chloroform were the main impact factors according to the sensitivity analysis.