Objective To comprehensively investigate the levels of exposure and distribution characteristics of trihalomethanes (THMs) in drinking water in Guangzhou City, and evaluate the health risks of different groups of children, adolescents and adults, and to provide data and evidence for protecting human health and promoting risk control of drinking water. Methods According to the technical requirements of the ^"Standards for Drinking Water Quality Testing Methods^" (GB/T 5750-2023), the concentration of THMs, including trichloromethane (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and tribromomethane (TBM) in drinking water in Guangzhou City from 2023-2024 were detected. The health risk model recommended by USEPA was used for risk assessment．Results TCM, BDCM and DBCM were detected in the factory water and terminal water, with TCM contributing the most. There was a statistically significant difference (P<0.05) between the wet and dry seasons, and the concentration of TCM in the wet season was higher than that in the dry season. Among the multiple exposure factors, the amount of exposure through drinking water intake was much greater than that through skin absorption. The carcinogenic risk index of THMs for children, adolescents, and adults was 22.0×10^-6, 12.2×10^-6, and 11.4×10^-6, respectively, while the non-carcinogenic risk was less than 1. Conclusion The exposure risks of THMs in children, adolescents, and adults is within an acceptable range, but monitoring needs to be strengthened, with a particular focus on children.

Objective To evaluate the efficacy of a sustained releasing mosquito larvicide package against larval breeding and its impact on water and plant,in order to provide a scientific evidence for its application in control and prevention of Dengue.Methods Guangzhou Center for Disease Control and Prevention was chosen as the test place.Twenty test sites were set up,2 bags of sustained releasing larvicides package,1 bag of sustained releasing larvicides package,3 g 1％ temephos granules and nothing were put into 4 glass bottles for each test site from July to December in 2014,respectively.The 4 glass bottles were called high dose (H) group,low dose (L)group,positive control (P) group and blank control (B) group,respectively.The 4 groups were observed at intervals of 10 days for 19 times.Environmental air temperature,turbidity of water,number of larvae and damage of plant were recorded.And 5 test sites were selected to collect water specimen.The chemical oxygen demand,ammonia nitrogen concentration and temephos concentration of water specimen were detected.Results The larval breeding rates were 0 (0/380),1.1％ (4/380),0.8％ (3/380) and 63.4％ (241/380),damage rates of plant were 5.0％ (19/380),5.5％ (21/380),4.7％ (18/380),4.7％ (18/380) and turbidty rates of water were 24.5％ (93/380),19.7％ (75/380),33.4％ (127/380) and 20.3％ (77/380) in H,L,P and B groups,respectively.Statistically significant differences were seen in larval breeding rate and turbidity rate of water between different groups (x2 =823.565,24.715,all P ＜ 0.05),but they were not seen in damage rate of plant (x2 =0.332,P ＞ 0.05).The temephos concentrations were 1.24,0.78 and 2.33 mg/L in H,L and P groups,respectively.Statistically significant differences were seen in temephos concentration between different groups (H =35.426,P ＜ 0.01),but they were not seen in chemical oxygen demand and ammonia nitrogen concentration (H =0.239,0.013,all P ＞ 0.05).Conclusions The sustained releasing package of mosquito larvicide makes less pollution to water and has no impact on water turbidity.Moreover,it doesn't damage the aquatic plant.The efficacy of the sustained releasing package of mosquito larvicide could effectively prevent mosquito larval breeding in Dengue epidemic period.