Leakage of soluble microbial products from biological activated carbon filtration in drinking water treatment plants and its influence on health risks.

The application of ozone-biological activated carbon (O3-BAC) as an advanced treatment method in drinking water treatment plants (DWTPs) can help to remove organic micropollutants and further decrease the dissolved organic carbon (DOC) level in finished water. With the increase attention to microbial safety of drinking water, a pre-positioned O3-BAC followed by a sand filter has been implanted into DWTP located in Shanghai, China to increase the biostability of effluents. The results showed that BAC had high removal efficiencies of UV254, DOC and disinfection by-product formation potential (DBPFP). The removal efficiencies between pre- and post-positioned BAC filtrations were similar. Based on the analyses of fluorescence excitation-emission matrix spectrophotometry (FEEM), the generation and leakage of soluble microbial products (SMPs) were found in both two BAC filtrations on account of the increased fluorescence intensities and fluorescence regional integration (FRI) distribution of protein-like organics, as well as the enhanced biological index (BIX). The leakage of SMPs produced by metabolism of microbes during BAC process resulted in increased DBPFP yield and carcinogenic factor per unit of DOC (CF/DOC). Although BAC filtration reduced the DBPFP and CF, there still was high health risk of effluents for the production of SMPs. Therefore, the health risks for SMPs generated by BAC filtration in drinking water advanced treatment process should be addressed, especially with that at high temperature.

A study on the lymphocytes genetic damage of occupational population exposed to methyl tert-butyl ether / 预防医学

Objective To investigate the genetic toxicity of methyl tert-butyl ether (MTBE) to lymphocytes and to provide reference for establishing the occupational population exposure limit of MTBE. Methods The human B lymphocytes in the logarithmic growth phase were respectively exposed to MTBE at concentrations of 0, 1.25, 2.5, 5, 10 and 12.5 μmol/L. The percentage of tail DNA and Olive tail moment of human B lymphocytes were evaluated after 24 h exposure by using comet assay. Apoptosis was tested by Annexin V-FITC/PI double-staining flow cytometry. The contents of MDA and 8-OHdG, as well as GSH-Px activity were measured by ELISA kit. Sixty workers from a petrochemical factory in Zhejiang were selected as the occupational exposure population, and 55 non-occupational exposure workers were selected as the control population. And 5 mL heparin anticoagulant peripheral blood was collected, and the number of micronucleus of peripheral blood lymphocytes was measured by micronucleus test, and the percentages of tail DNA as well as Olive tail moment of peripheral blood lymphocytes were measured by comet assay. The contents of MDA and 8-OhdG and GSH-Px activity in peripheral blood plasma were measured by ELISA kit. Results After 24 h exposure, the percentage of tail DNA and Olive tail moment in human B lymphocytes at concentrations of 10-12.5 μmol/L were significantly higher than those in the control group (P<0.05), and the percentage of early apoptosis cells was significantly increased at concentrations of 10-12.5 μmol/L (P <0.01) . The results of population-based study indicated no statistically significant difference in micronucleus positive rate, and the contents of MDA and 8-OhdG, and GSH-Px activity between the exposure group and the control group, but the Olive tail moment was significantly higher in the exposure group compared with the control group (P=0.000) . Conclusion The results of vitro study showed that exposure to 10-12.5 μmol/L MTBE could cause genetic toxicity to human B lymphocytes. Olive tail moment of peripheral blood lymphocytes of occupational exposure workers was significantly higher than that of non-occupational exposure group.

The effects of CdSe/ZnS quantum dots on embryonic development of zebrafish / 预防医学

Objective To understand the developmental effects induced by CdSe /ZnS quantum dots(QDs)on zebrafish embryos.Methods Zebrafish embryos were exposed to 0,0.5,1,2,4,8 and 16 nmol/L of CdSe /ZnS QDs,and the typical toxicological indexes were recorded at five time points respectively (24 hours post fertilization (hpf),48 hpf, 72 hpf,96 hpf,120 hpf).Results The results showed that the median lethal concentration (LC50 )for zebrafish embryos after 120 hpf was 21.38 nmol/L(95% CI =17.21 -26.57).The frequency of spontaneous movement in 60 seconds after 24 hpf,the frequency of heart beat in 60 seconds after 48 hpf,the hatching rate and the mortality rate were obviously affected by CdSe /ZnS QDs.Several abnormalities and toxic symptoms caused by CdSe /ZnS QDs at 8 nmol/L and 16 nmol/L were observed including pericardial edema,liver atrophy,non -depleted yolk,intestinal abnormal development and muscle degeneration after 120 hpf.Conclusion High level of CdSe /ZnS QDs (more than 8 nmol/L)could induce toxic effects on zebrafish embryonic development.

Male reproductive toxicity of polychlorinated biphenyls / 中华男科学杂志

Polychlorinated biphenyls (PCBs) are a class of persistent organic pollutants with estrogen-like effects that exist widely in the environment, and its male reproductive toxicity is arousing more and more attention. Studies indicate that different types of cells in the testis respond differently to PCBs exposure. This article presents an overview on the toxicity of PCBs to testicular germ cells, Leydig cells, Sertoli cells and male offspring. We suggest that deeper studies focus on the mechanism of PCBs according to the results of investigations on male reproductive epidemiology. An insight into the intercellular junctions of Sertoli cells might produce a breakthrough in the studies of the testicular toxicity of PCBs.