Mutagenicity, health risk, and disease burden of exposure to organic micropollutants in water from a drinking water treatment plant in the Yangtze River Delta, China.

A wide variety of organic micropollutants in drinking water pose a serious threat to human health. This study was aimed to reveal the characteristics of organic micropollution profiles in water from a drinking water treatment plant (DWTP) in the Yangtze River Delta, China and investigate the mutagenicity, health risk and disease burden through mixed exposure to micropollutants in water. The presence of organic micropollutants in seven categories in organic extracts (OEs) of water from the DWTP was determined, and Ames test was conducted to test the mutagenic effect of OEs. Meanwhile, health risk of exposure to organic micropollutants in finished water through three exposure routes (ingestion, dermal absorption and inhalation) was assessed with the method proposed by U.S. EPA, and disability-adjusted life years (DALYs) were combined to estimate the disease burden of cancer based on the carcinogenic risk (CR) assessment. The results showed that 28 organic micropollutants were detected in the raw and finished water at total concentrations of 967.28 ng/L and 1073.45 ng/L, respectively, of which phthalate esters (PAEs) were the dominant category (95.79% in the raw water and 96.61% in the finished water). Although the results of the Ames test for OEs were negative and the non-carcinogenic hazard index of the organic micropollutants in the finished water was less than 1 in all age groups, the total CR was 2.17 × 10-5, higher than the negligible risk level (1.00 × 10-6). The total DALYs caused by the organic micropollutants in the finished water was 2945.59 person-years, and the average individual DALYs was 2.21 × 10-6 per person-year (ppy), which was 2.21 times the reference risk level (1.00 × 10-6 ppy) defined by the WHO. Exposure to nitrosamines (NAms) was the major contributor to the total CR (92.06%) and average individual DALYs (94.58%). This study demonstrated that despite the negative result of the mutagenicity test with TA98 and TA100 strains, the health risk of exposure to organic micropollutants in drinking water should not be neglected.

Characterization of glutathione conjugates derived from reactive metabolites of bakuchiol.

Bakuchiol belongs to a family of monoterpene phenols occurring in plant Psoralea corylifolia L., a traditional herbal medicine. Bakuchiol has also demonstrated multiple pharmacologic activities. However, metabolism of bakuchiol had never been investigated. The major objective of the present study was to study the metabolic pathways of bakuchiol in order to identify potential reactive metabolites. A total of five glutathione (GSH) conjugates (M1-M5) were detected in rat/human liver microsomes containing NADPH, GSH, and bakuchiol. M1 and M2 resulted from GSH conjugated on the phenol ring. M3, M4, and M5 were derived from GSH adducted on the side chain. The results displayed that bakuchiol can be bioactivated by oxidation of the phenol moiety to the corresponding ortho-quinone and by epoxidation of the aliphatic side chain to epoxide metabolites. No bakuchiol-derived GSH conjugates were detected in urine of rats given bakuchiol, but six corresponding cysteinylglycine (Cys-Gly) conjugates and mercapturic acids were observed instead. A 2'-iodoxybenzoic acid-mediated oxidation reaction of bakuchiol in the presence of GSH produced M1 and M2, and m-chloroperoxybenzoicacid-mediated oxidation of bakuchiol trapped with GSH generated M3 and M4. The four synthetic metabolites were detected in microsomal incubations. In addition, recombinant P450 enzyme incubations showed that CYP 1A2 was the predominant P450 responsible for the metabolism of bakuchiol. In summary, our results demonstrated that bakuchiol can be bioactivated to quinone and epoxide metabolites. These findings facilitate the understanding of the mechanisms of bakuchiol-induced cytotoxicity.

Spatio-temporal patterns of schistosomiasis japonica in lake and marshland areas in China: the effect of snail habitats.

The progress of the integrated control policy for schistosomiasis implemented since 2005 in China, which is aiming at reducing the roles of bovines and humans as infection sources, may be challenged by persistent presence of infected snails in lake and marshland areas. Based on annual parasitologic data for schistosomiasis during 2004-2011 in Xingzi County, a spatio-temporal kriging model was used to investigate the spatio-temporal pattern of schistosomiasis risk. Results showed that environmental factors related to snail habitats can explain the spatio-temporal variation of schistosomiasis. Predictive maps of schistosomiasis risk illustrated that clusters of the disease fluctuated during 2004-2008; there was an extensive outbreak in 2008 and attenuated disease occurrences afterwards. An area with an annually constant cluster of schistosomiasis was identified. Our study suggests that targeting snail habitats located within high-risk areas for schistosomiasis would be an economic and sustainable way of schistosomiasis control in the future.