Health Risk Assessment Associated With Water Quality Of Rural Drinking Water Sources

Drinking water safety is facing great challenge as the development of economy in our county and frequent water environment pollution events.How to ensure drinking water safety,especially the safety of drinking water quality is an urgent problem to solve in vast rural area of China.Water quality is relative to residents' health,but traditional water quality assessment methods can reflect water pollution situation,they cannot reflect the extent to which such pollution harms human health.Health risk assessment is a method for assess the harm of the contaminants in the environment bring to human health.Therefore,it is very necessary to carry out health risk assessment work.The study firstly determined the index of major hazards in the research area on the basis of the survey of pollution sources,disease and residents' drinking habit,as well as the test of water quality of rural drinking water sources in Mingshan District,Ya'an City,Sichuan Province,and in accordance with the drinking water sanitary standard and chemical toxicity classification.Then analyzed and derived exposure parameters regarding the rural drinking water by using SPSS 17.0 Statistical Software;evaluated health risks through exposure pathway of drinking water and skin contact by adopting US Environment Protect Agency(USEPA)Health Risk Assessment(HRA)Model in the following;and finally discussed temporal and spatial variation characteristics of health risks with support of Geographic Information System(GIS)technology,to provide scientific basis for concerned departments of the research area to carry out risk management.The main achievements were as follows:(1)Using random sampling method,this study investigated the drinking water exposure characteristics of rural residents,and got 1240 investigators' information.The results showed that:all the investigators' average body weight,average daily drinking water intake rate and average skin surface area were 57.6kg,1.88L/d and 1.6m2 respectively.These three exposure parameters increased with age at first,and reached up to the maximum at the age of 46-60,then gradually decreased.(2)USEPA Health Risk Assessment Model was improved in response to the drinking habit of the residents in this research area,and thus a health risk assessment of water quality is carried out against concerned contaminants.The results showed that:the carcinogenic risk of both Cr6+ and As was over the acceptable level 10-6 and they should be considered as the major contaminants in the drinking water of this area.As for non-carcinogenic risk,the individual contaminants were sequenced in terms of the value size of the waterborne health risk as about fluoride>nitrate>Cu>Cr6+>As>Fe>ammonia>nitrogen>nitrite>Mn.Excepted that the total non-carcinogenic risk of the drinking water in Matou Village,Yongxing Town in 2010 was greater than 1,that of others was all within the acceptable level 1.Skin exposure route:the non-carcinogenic risk of skin exposure to Cr6+ was basically greater than 0.01(in some water sources,such risk exceeds 0.1),while that of skin exposure to all the remaining 8 major contaminants are less than 0.01,which,in another word,would not harm the residents' health via skin exposure.In terms of the total risk index,the said individual contaminants were sequenced in terms of the value size as about fluoride>Cr6+>nitrate>As>Cu>Fe>Mn>ammonia>nitrogen>nitrite.Water drinking was the main non-carcinogenic route of combined factors of contaminants,with contribution to the total risks accounting for 86.83%.(3)Monte Carlo(MC)Simulation was adopted to quantify the uncertainties of water quality health risk.The simulation results showed that all the span of total carcinogenic risk was higher than the acceptable level 10-6 while that that of total non-carcinogenic risk was within the risk control standard 1;BW was negatively sensitive to the risk assessment results,while IR,EF,SA and contaminant concentration appeared to be positively sensitive to such results.And,IR and Cr6+ were most sensitive to the risk assessment results.Exposure factors had a great influence on risk assessment results.(4)The water quality health risk of the rural water sources in this study varied greatly in time and space.Specifically,in term of time,the health risk value of contaminants(except Fe and Cu)differed a lot in different years.In term of space,all health risk values appeared to be significantly different.For example,the carcinogenic risk and total carcinogenic risk of Cr6+,as well as the non-carcinogenic risk of Fe,Cu,and Cr6+ appeared to gradually low down from the northeast area to the south area,and went up near Mingshan Downtown;while that of fluoride was on the contrary;the non-carcinogenic risk of nitrate,nitrite and ammonia varied relatively greatly and tended to go up;however,the total risk appeared to be relatively high in the southwest area and near Mingshan district.