| Persistent toxic substances are a kind of strongly toxic pollutant that are difficult to degrade in environment and can enrich and enlarge through the food chain in animal and human beings. Substantial evidences reveal that persistent toxic substances have carcinogenic, teratogenic and mutagenic effects and genetic toxicity, which have great harm on human health and ecosystems. Accordingly, health risk assessment for persistent toxic substances has great realistic and strategic significance in these fields of pollution treatment and prevetion, improving ecological security and environmental quality and promoting sustainable economic development of Shanghai. With the support of the National Nature Science Key Foundation, "Biogeochemical cycling of pollutants in complex environments of tidal flats in the Yangtze Estuary", the bidding project of Shanghai Environmental Protection Bureau, "The source investigation and strategies research of persistent toxic substances in Shanghai", and the Key Program of Shanghai Science Foundation, "The environmental pollution process and control technologies of endocrine disruptors in Shanghai drinking water area", the paper develops human health risk assessment for several kinds of persistent toxic substances in different ambient medium based on the acquired 11,005 data of persistent toxic substances in different ambient medium of Shanghai and adopts the four step rule of health risk assessment put forward by the National Academy of Sciences of United States. Combining with the population characteristics and choosing typical regions of Shanghai, the paper develops human health risk assessment for several kinds of persistent toxic substances in several parks of Shanghai, urban road, atmosphere of industrial area, surface water and suburban vegetable plot, etc. which are all the media close to human life and the environment by using the models for evaluating exposure dose and health risk.This paper's main findings are as followed:1. A filtrating evaluation system for PTS was established. By selecting three fields of physicochemical properties, environmental exposure procedure and environmental toxicology, altogether 11 indexes of PTS, and applying AHP, we established the system of score index in order to identify several kinds of PTS which have larger hazards to human health. The results show that benzo(a) pyrene is of the highest total score in several kinds of persistent toxic substances, followed by chromium (VI), cadmium, lead and benzene hexachloride (BHC, a kind of organo-chlorine pesticides). 2. Combining with the toxicology experiment of snails (a kind of zoobenthos) and applying the average lethal dose method and graphic method, the paper calculates the half lethal dose of mercury to snails. Through extrapolating from uncertainty factor and correction coefficient, the paper gets extrapolation dose about 1 × 10-4mg/kg from zoobenthos to the crowd, which is in the same order of magnitude with the reference dose recommended by EPA.3. According to corresponding evaluation model, the paper estimates the exposure dose of PTS through three exposure ways in different ambient medium. The results show that the exposure dose to dust in the way of direct ingestion for children is 98% of the overall exposure dose in urban park and urban roadside environment, which is of eight times of that for adults in this way. It shows that the way of direct ingestion is the principal way for adults and children exposed to PTS and the health risk of PTS in dust on adults, especially for children should not be overlooked. Compared with the Netherlandish allowable level of human ingested toxic pollutants, the exposure dose of lead for Children is nearly doubled in these parks of Shanghai, while the human exposure dose of lead and chromium in urban roadside is all over the Netherlandish reference level (3.6μg/kg·d and lμg/kg·d accordingly), which should arouse enough attention for the relevant administrative department. When comparing the exposure dose of the same PTS in different ambient medium, it is found that it was the biggest dose in urban parks and roadside dust and the next was in the way of vegetable ingestion.4. Using the health risk assessment model of chemical carcinogens and non-carcinogens and combing with the maximum acceptable risk level recommended by relative agencies and authors, the paper develops the risk assessment of carcinogenic and non-carcinogenic PTS in different ambient medium of Shanghai. The results indicate that the hazard of carcinogenic PTS on human health is far greater than the risk of non-carcinogenic substances. Both of them differs about 7 magnitudes at best. It reveals that some carcinogenic chemical substances in people's surroundings should be as a major decision-making management focus of risk. The risk assessment results of carcinogenic PTS show that chromium has the highest risk and it reaches 10-4 and 10-5 level in urban park and roadside environment of Shanghai, which is over the maximum acceptable risk level recommended by a number of organizations and scholars and also exceeds the acceptable social risk value of EPA (10-710-6/a). It shows that chromium has posed a potential danger to the human health in the above two kinds of environmental background, which requires enough attention for the relevant administrative department. Lead has the highest health risk in non-carcinogenic PTS. It reveals that increasing traffic gives serious lead pollution to the ambient environment in the process of urbanization. The risk level in atmosphere environment of Wujing industrial area is lower than that of inhalation way in urban park and roadside environment of Shanghai. By analyzing PTS health risk of organochlorine pesticides in the trunk stream and tributary stream of upriver Huangpu River, it shows that the risk level of organochlorine pesticides is within 10-14/a, which is less than that of heavy metals. By the way of vegetable ingestion, the human health risk of PTS is higher than that of drinking way for 10 1000 times.5. Using Kriging interpolation method, the exposure dose and health risk is studied in urban parks and roadside environment. The result shows that human health risk still has definitive geographical differences for the same heavy metals and the same mediums.6. Based on the risk level, source of pollutants and human exposure ways of the OCPs, PAHs and toxic heavy metals, such as Cd, Hg and Pb, etc. of Shanghai, referring to monitoring, control and management programs of PTS in domestic and foreign country, and fully considering the social, economic development and pollution control capacity of Shanghai, the paper puts forward adaptive pollution control technology and management strategies in terms of technical, legal, economic and politic aspects which focuses on the heavyly PTS polluting regions.
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