Study On Indoor PM_2.5 Pollution And Its Health Effects

In recent years,particulate matter(PM_2.5)pollution has become one of the most prominent environmental problems in China.Epidemiological studies have discovered the robust causal associations between PM_2.5 exposure and a series of adverse health effects including respiratory and cardiovascular morbidity and mortality.Fixed-site measurements of PM_2.5 were typically used to represent human exposure concentrations for health effects assessment in air pollution studies.However,people spend more than 80% of their time indoors,the difference between indoor and outdoor PM_2.5 concentrations may bias exposure and health effect assessments in epidemiological studies.Therefore,studies on indoor air pollution are important for improving the accurateness of exposure and health impact assessment.To address this need,this study firstly explored the main factors that affecting indoor PM_2.5 based on both indoor and outdoor PM_2.5 concentration monitoring data and questionnaire survey conducted at the same time.Then,constructed a prediction model for indoor PM_2.5 concentration in residential buildings based on the main influencing factors.Afterwards,studied the spatiotemporal characteristics of indoor PM_2.5 concentration distribution at urban scale.Finally,evaluated the impact of indoor PM_2.5 pollution on public Sick Building Syndrome.The main conclusions can be drawn as follows:The results showed that indoor PM_2.5 concentration and its chemical compositions had significant seasonal variation trends.Indoor PM_2.5 concentration between different families was significantly different,due to the outdoor PM_2.5 concentration,indoor sources(cooking,smoking,etc.),ventilation,building characteristics,and socioeconomic variables.This study built an indoor PM_2.5 concentration prediction model for multiple residences using the multizone airflow and contaminant transport program(CONTAM)based on the building characteristics,outdoor PM_2.5 infiltration and indoor source emissions.The accuracy of the model was verified by a good agreement between the model simulations and the measurements(r = 0.89~0.96).The results of the model validation demonstrated the model's ability to predict PM_2.5 concentrations in multiple residences in China with different building characteristics and indoor activities.The spatiotemporal distributions of indoor PM_2.5 levels in Nanjing were predicted by CONTAM based on the geographical distribution of residences,outdoor PM_2.5 concentrations and indoor human activities.Indoor PM_2.5 concentrations showed a significant seasonal variation which was consistent with the trends of outdoor PM_2.5 levels.Due to the protective effect of the building envelope,indoor PM_2.5 concentration was lower than the outdoor level.Moreover,building characteristics plays an important role in the distribution of indoor PM_2.5 levels.Older multistorey residential buildings were found to be more easily affected by outdoor PM_2.5 pollutions than newly built high-rise buildings.The spatial distribution of indoor PM_2.5 over Nanjing was observed in this study.Higher indoor PM_2.5 concentrations were observed in the center,suburb and southwest area of the city due to the effect of building characteristics on outdoor PM_2.5 permeability.The overall population exposure to PM_2.5 would be overestimated by 16.67% if indoor exposure was not taken into account,leading to a bias in the health impacts assessment.This study provides an example for the study of temporal and spatial distribution of indoor PM_2.5 pollution and provides new evidence for the importance of indoor air exposure on population exposure and health effects assessment in epidemiological studies.In addition to the health effect,PM_2.5 pollution may also cause mild adverse to the health of human at the early period of exposure such as Sick Building Syndrome(SBS).The SBS symptoms of the public and residential indoor environmental characteristics in Nanjing were investigated by questionnaire survey.The incidence of general symptoms,mucosal irritation and skin irritation of the population in Nanjing were 14.4%,9.8% and 5.1%,respectively.Combining indoor PM_2.5 prediction model constructed in this study and the location of respondent's dwellings,indoor PM_2.5 concentration was found to be a risk factor for general symptoms and mucosal irritation symptoms.The characteristics of the indoor environment,such as building age,area,number of the occupants,wall/paint peeling,indoor smoking,cleaning frequency,and population perception of indoor air quality were also important factors affecting the incidence of SBS.The study provide evidence for the correlations between indoor PM_2.5 pollution and public SBS.It is necessary to improve indoor air quality,actively control indoor pollution sources to reduce indoor air pollution and its impact on human health.