Studies On The Regional Health Risk At The Area Of The Sewage Irrigation In Shijiazhuang City

The environmental studies focus at the regional environmental problems in recent years. Studies on the environmental health risk indicate the potential widespread occurrence of health damdage caused by low-level concentration of contaminants in environmental media. Many heavy mental contaminants are poisonous and able to cumulate in organism. Most organic chlorine pollutants (OCPs) are persistent organic pollutants (POPs), which are basic compounds and do not decompose easily. There exist many sites with heavy metal and organic chlorine contaminants at the area of sewage irrigation in Shijiazhuang City, China because of inappropriate handling or disposal of hazardous materials or wastes. Health risk assessment is an important tool to evaluate the potential environmental and health impacts of these contaminated sites. In this thesis, the effect of numerous biological, chemical, physical, behavioral and physiological processes of the contaminants that involve elements of uncertainty and variability were considered. An idealized system dynamics model used to simulate the dynamic process of sewage in multimedia environment was set up to analyze the actuality and development current of the concentration of contamnants in different environmental media. A three-part multimedia transformation model was set up to study the health risk from multimedia transfer of arsenic, cadmium, hydrargyrum and organic chlorine contaminants, the Monte Carlo methods were used to test the uncertainty and variability of the conclusions. An integrative risk exponent was given to denote the total health risk for residents at polluted area from all the contaminants. The method was used to forecast the development currency of the health risk according to the current situation. In the end, some measures for alleviating the health risk were studied and a preparatory framework of the regional health risk management was set up.The main contents are summed up as follows:(1) The relationship between different water resources was analyzed. A system dynamic model of water resource system was set up with the Vensim software, and the pollution situation of water resource was studied. The results showed that a system dynamics model may be helpful for the region health risk analysis, the concentration of heavy mental and organic chlorine contaminants in soil will decreased, and the concentration of heavy mental and organic chlorine contaminants in groundwater will increased from 2000 to 2030.(2) The damage of the contaminants to the residents' health was analyzed. Based on the results of pollution situation of water resource, a multimedia exposure model was set up. The health risk of Arsenic, Hydrargyrum, Plumbum and DDT, HCH was studied. The result showed that a decision based on multimedia risk assessment may different from one based on only one environmental media. The main environmental media that contributed to the total risk may be different according to different contaminants because of different concentration and biologic characteristic. For heavy mental contaminants, soil and groundwater are the main exposure media, ingestion of food and drinking water are the major exposure pathways. For organic chlorinecontaminants, groundwater and air are the main exposure media, ingestion of drinking water are the major exposure pathways. From 2000 to 2030, the health risk of heavy mental and organic chlorine contaminants will keep increasing.(3) A chronic harmful index (HI) was used to assess the total health risk at studied area. Then the uncertainty and variability of the conclusions were tested with the Monte Carlo methods. The results showed that the total health risk in 2002 was under the acceptable level, in 2010 it will be too high for the residents, among which the pollution from heavy mental contaminants was more serious than that from organic chlorine pollutants. The result from Monte Carlo simulation showed that the probability for the total risk less than 1.0708 in thirty years was 50%, it will be 80% for the total risk between 0.9 and 1.3 in thirty years.(4) After analysing the characteristic of the regional health risk, some measures for alleviating the health risk were studied; the system dynamic method was used to compare the different measures.The best measure can be achieved.