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Taking Rain City District of Ya’an for example, this paper based on ComGIS (Component Object Model Geographic Information System) platform takes comprehensive and systematic detection on the exposure dose of chemical carcinogens and non-carcinogens from drinking water sources in this region and discusses health risk assessment of single factor and the whole health risk assessment. As, Hg, Cr, Pb, Cd and fluorides in some drinking water sources of Rain City District are analyzed according to Standards For Drinking Wa-ter Quality (GB5749-2006). A health risk assessment model called USEPA is also applied to drinking water health risk assessment and management countermeasure is proposed. The results show that the greatest health risk for individual person per year is caused by Cr(VI). The health risk of carcinogens is much higher than that of non-carcinogens: the greatest risk value due to non-carcinogen pollutants is caused by fluoride (F), achieving 1.05×10-8/a. The ranking of risk values due to non-carcinogen pollutants by drinking water is Pb>fluoride (F)>Hg, within Pb accounting for 44.77%, fluo-ride (F) accounting for 34.30% and Hg accounting for 20.92%. The average individual carcinogenesis annual risk of Cr(VI) is the greatest, achieving 8.91×10-4/a. The ranking of risk value due to chemical carcinogen by rural drinking water of Ya’an is Cr6+>As>Cd, within Cr6+ accounting for 91.12%, As accounting for 5.89% and Cd accounting for 3.00%. Based on this, the strategy and measures of the health risk management are put forward. This study has worked efficiently in practice. Compared with the same kind of methods which have been found, the paper has the outstanding results for the health risk assessment of the rural drinking water safety.

Aiming at the unsafe of water quality which is the core problem in rural drinking water safety, the study col-lected 221 water samples of rural drinking water sources in Ya'an and detected the concentrations of the car-cinogen and the non-carcinogen. Based on the analysis of water environment characteristics and the identifi-cation of water environment health risk source of Sichuan Ya’an City, which includes seven counties and a district and is the typical region of the western margin of Sichuan Basin, this study calculated and analyzed the carcinogenic risk (R) and non-carcinogenic risk (hazard index, HI) by applying the health risk model recommended by the US National Research Council of National Academy of Science. Then, taking advan-tage of the geo-statistic spatial analysis function of ArcGIS, this study analyzed the assessment result data (R and HI), selected the proper interpolation approach and educed R and HI spatial distribution maps of the study area. R and HI of the single factor and integrate factors were evaluated and thus obtained the following conclusions: For one thing, the cancerous risk indexes of the vast majority of water sources (about 94%) is the level of 10-7 and it belong to the safety extension. The main carcinogen in the water sources are As, Cr6+ and Pb, their concentrations are in the ranges of 0.004-0.01, 0.005, 0.01mg/l respectively and such water source mainly distributed in Yucheng district and Mingshan county. For another, the non-cancerous hazard indexes of the vast majority of water sources (about 98%) is also less than the limit value 1 and will not harm the local residents. The health risk of non-carcinogen comes mainly from As and fluoride, their concentra-tions are in the ranges of 0.004-0.01 and 0.1-4.2mg/l respectively. The results of the integrate factors health risk assessment showed that the total cancerous risk were still at the level of 10-6, only 12 drinking water source investigation sites (5%) exceeded the drinking water management standard value of EPA (the limit value is 10-6); the total non-cancerous hazard indexes are still in the range of 10-2-10-1, and will not harm the local residents either, only 18 drinking water source investigation sites (8%) exceeded the drinking water management standard value of EPA(the limit value is 1).The densely populated areas such as Yucheng Dis-trict, Tianquan County, Yingjing County and Shimian County are where the four contaminating materials, i.e., As, Cr6+, Pb and fluoride should be monitored with emphasis. Study results disclosed the health risk control indexes of source water quality of the studied area and thus provided the scientific basis for the water quality control of water sources. This study had worked efficiently in practice. Compared with the same kind of methods which had been found, the paper had the outstanding results for the health risk assessment of the rural drinking water safety.

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Based on ArcGIS and the feature analysis for the water environment and the source identification of water environmental health risks in a typical area in the western edge of Sichuan basin-Mingshan County in Ya'an City of Sichuan Province, China, this study tested the water quality of 41 drinking water sources, applied the health risk evaluation model recommended by USEPA (U.S. Environmental Protection Agency) to calculate and analyze the rural drinking water quality carcinogenic risk(R) and non-carcinogenic risk(hazard index, HI), and drew risk maps including single-factor and integrate factors of carcinogenic and non-carcinogenic substances, the maps were in good agreement with the known spatial distribution of water quality contamination, applied the Tobit regression model to inspect significance and modeling results of HI, pointed out that the first 4 pollutants risk index of water sources were arsenic, fluoride, nitrate and iron, and suggested these 4 kinds of pollutants should be monitored specially. The study revealed the risk level, primary and secondary pollutants, governance priorities, formation mechanism, and provided a scientific basis for risk management for the rural drinking water quality in the study area.

A large number of uncertain problems existing in rural drinking water safety system, it is of great significances to apply Set Pair Analysis (SPA) theory to analyze and study these uncertain problems in rural drinking water safety system. This study applies SPA theory to conduct an integrated evaluation of water quality to rural drinking water safety in Ya'an City, based on classification values of Sanitary Standard for Drinking Water (GB5749-85). This study has worked efficiently in practice. Compared with the same kind of methods which have been found, this paper has the outstanding results for the uncertain problems of health risk assessment of the rural drinking water safety.