Characteristics And Health Risk Effects Of Indoor/Outdoor PM_2.5 And Its Metal Elements Of College Dormitory In Nanjing

Air pollution is one of the main factors leading to premature death,causing nearly one million deaths worldwide every year.Fine particulate matter PM2.5 has a strong permeability,affecting the indoor air quality seriously.Owing to it accessible for PM2.5to human body by respiratory tract,several harmful metal elements associated with PM2.5 leading to teratogenesis and carcinogenesis easily.As an important place for undergraduate to study and live,students spend nearly half of their time in dormitories every day.Therefore,it is of great significance to study exposure assessment of metal elements and health effects of PM2.5 in college dormitories.In this study,PM2.5 samples and indoor environmental parameters were obtained in the living quarters of a university in Nanjing.The mass concentration of PM2.5 and metal elements associated with it inside and outside the dormitory were determined.The influencing factors and permeability factor were obtained by linear regression.After using enrichment factor and geological accumulation index to evaluate the metal pollution level of PM2.5,principal component analysis and positive definite matrix factor analysis were used to analyze the source of PM2.5.Finally,the metal exposure and health risk were evaluated by the method basing on Disability Adjusted of Life Years(DALYs)and EPA health risk assessment model.The main conclusions are as follows:the average temperature,humidity,concentrations of formaldehyde in dormitory meet the requirements of the standard.However,the concentration of CO2 exceeds the limit.The daily average concentration of indoor and outdoor PM2.5 is higher than 75μg/m~3 in a few days.The order in related factors affecting PM2.5 is concentration of outdoor PM2.5>indoor temperature>concentration of indoor CO2>outdoor temperature>indoor humidity.The influencing factors of PM2.5 in student dormitories are more or stronger than those in empty dormitories.In the same environment,the concentrations of Ca,Al,Na,K,Mg,Fe,Zn were higher than those of Cr,Pb,Cu and Ni,Cd,Co.The permeability factors of different metal elements are 0.013～1.4 in dormitory.Metal elements associated with PM2.5indoor are affected by both human activities and natural environment.Cd,Zn,Pb,Cu and Cr are highly polluted by human activities.The metal pollution in outdoor is lower than that in dormitory,and in spring is higher than that in autumn and winter.There was little difference of source among the three dormitories.In autumn and winter,the order of contribution rate is industrial>soil>combustion>traffic.In spring,industrial>combustion>traffic>soil.The contribution rate of industrial sources in dormitory is 22.31～49.09%.The concentration of PM2.5 in student dormitory was 25.39±15.51～44.30±31.72μg/m~3.The time loss caused by PM2.5 in student dormitory is 998.64～1156.86 y/y·100000,about 2.36～3.60 times of that in empty dormitory.The health risk of metal elements associated with PM2.5 was less than the limit.Non carcinogenic risk and carcinogenic risk in spring were 2.42E-03～2.46E-02 and 2.93E-06～2.98E-05,respectively.The non carcinogenic risk values of Pb and Cr are higher than other metals.Cr has a certain degree of carcinogenic risk.Therefore,it is necessary to strengthen the source control of Pb and Cr,especially Cr.The change of health risk of metals is consistent in time and space,closely relating to the concentration of PM2.5 and metal elements.Long time for students staying in the dormitory,the health risk indoor is 6times higher than that of outdoor.More attention should be paid to control indoor PM2.5.