| In recent years,most cities in China have experienced increasingly severe haze weather,which has seriously affected people's health while affecting the visibility of outdoor air,and has aroused constant attention from the government and people from all walks of life.Modern people spend most of their time indoors,so effective measures are taken to reduce the concentration of PM2.5 in the indoor air and reduce the body's PM2.5 health risk.The quality of indoor air quality directly affects people's health.The toxic and harmful substances in the air are harmful to human health by affecting people's respiratory system,blood circulation system,nervous system,and cardiovascular system,ultimately increasing the risk of cancer in humans..The harmful substances in PM2.5 particles are mainly entered into people's bodies through breathing,oral intake,and skin intake.This paper focuses on the stochastic theoretical study of the risk of heavy metals in PM2.5 particles in indoor air and evaluates the health risk level.By investigating the residence time of Changsha residents in different indoor environments,the concentration of PM2.5 in indoor air of different functional rooms in the house was measured and the chemical composition was analyzed.On this basis,indoor PM2.5 health risk assessment and simulation based on stochastic theory was performed.From August 1,2017 to October 28,2017,filters PM2.5 depth in typical residential indoor air in five urban areas including Yuelu District,Furong District,Tianxin District,Kaifu District and Yuhua District of Changsha City.Acquisition and chemical composition analysis,and a questionnaire survey of room staff.Monte Carlo simulations were performed on experimental data and questionnaire data using the Crystallall ball software.The main conclusions are as follows:(1)Questionnaire survey shows that Changsha residents spend about 94% of their time in different indoor environments.Residence time in residential buildings accounts for about 45% of the total indoor time.Long,reach 8h or more daily.(2)The indoor PM2.5 concentration detection of different functional rooms in the residential house found that the mean,maximum and minimum values of the PM2.5 concentrations in different functional rooms are quite different.If the average PM2.5 concentration in the residential air is used,There are significant errors in the value of health risk assessment.In addition,the PM2.5 concentrations in different functional rooms vary,and the PM2.5 concentrations in the kitchen,dining room,and living room are higher than those in the master bedroom,the second bedroom,and the study,and the average concentrations are 98 ug/m3 and 90 ug/ respectively.M3,90 ug/m3,should be combined with different functional rooms for health risk parity.(3)Monte Carlo Simulation Simulation shows that the 95% carcinogenic risk of four carcinogenic metal elements Cr,Ni,As,and Cd in PM2.5 exceeds that of the US Environmental Protection Agency for both carcinogenic risk and safety,whether male or female.The range is 7.2×10-4 for males and 6.5×10-4 for females,which is about 7 times the safety value,and there is a greater risk of cancer.And the 95% cancer risk rate is 2.3 times the average value of the carcinogenic risk.Therefore,using the average value of the PM2.5 concentration to carry out the health risk simulation calculation has a large error,and then this study uses a random theory based indoor PM2.5 health risk assessment Taking full account of its randomness will greatly reduce the experimental error and increase the credibility of the experimental results.(4)Whether male or female,the carcinogenic risk factors of four carcinogenic metal elements in PM2.5 in residential indoor air are ranked Cr>As>Cd>Ni,and the sensitivity of the main uncertainties in the experiment is analyzed.Found that,whether male or female,the uncertainty of cancer risk is mainly CA,ET and BW.The carcinogenic risk contribution values of the four carcinogenic metal elements Cr,Ni,As,and Cd were CA>ET>BW. |
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