Since people spend most of their time in a relatively closed and small-scale indoor environment, various pollutants are not easily diffused in the indoor environment, and therefore indoor environmental pollution has become one of the important influencing factors for human health. In China, the extent of human exposure to indoor air pollutants and the relationship between indoor and outdoor have not been adequately studied due to large differences in geography, source distribution, pollution characteristics, economic status and living habits, and systematic studies on indoor/outdoor and individual exposure characteristics are also needed. Therefore, this study takes indoor and outdoor particulate matter as the research object and systematically studies the physicochemical properties and exposure risk characteristics of indoor and outdoor particulate matter. This research also aims to resolve the sources of indoor particulate matter, which is of great value to study the migration mechanisms of organic pollutants in indoor and outdoor environments and to formulate pollution control policies in urban areas.

In this study, a total of 65 indoor particulate matter samples, 36 outdoor particulate matter samples and 7 outside building particulate matter samples were collected in different functional areas and floors in Hefei city, China. Based on various experimental analysis methods (rapid solvent extraction experiment, laser particle size analyzer, scanning electron microscopy-energy spectrometer, high-resolution gas chromatography-mass spectrometer, elemental analyzer-stable isotope mass spectrometer, etc.) and data analysis methods (principal component analysis, isotope tracer method, risk evaluation, etc.), the morphological characteristics, chemical composition, distribution and enrichment characteristics of typical organic pollutants, indoor particulate matter were determined. The main contents of this study are as follows:

(1) The differences in morphological characteristics and material composition of indoor and outdoor particulate matter were comparatively studied, and the effects of particle size and indoor human activities (cooking, smoking, etc.) on the sources of PAHs in the indoor particulate matter were revealed. The particle size of indoor dust is more concentrated in the range of 26-125 μm (26-62 μm and 62-125 μm) and 498-837 μm; compared with indoor particulate matter, outdoor particulate matter has some small (<2.5 μm) and large (>192 μm) particle size composition. The elemental distribution results of indoor particulate matter indicate that it is mainly composed of Fe and Zr-rich particles, in addition to C, O and Ca components; the elemental distribution results of indoor particulate matter indicate that it is mainly composed of Fe, O, Si, Al and Ca elements.

(2) The distribution, enrichment and assignment characteristics of typical organic pollutants in indoor particulate matter in different functional areas were revealed, and the distribution of indoor PAH mean values in different administrative regions of Hefei was found in the following order: Baohe > Jingkai > Yaohai > Shushan > Binhu; the most prominent concentrations of OCPs were Endosulfans and Cis-chlordane; the concentrations of ∑PCBs and ∑OCPs concentrations in different functional areas were decreasing for governmental affairs (AD) > Shushan (CD) > Jingkai (ID) > outdoor (OD) and Shushan (AD) > governmental affairs district (CD) > outdoor (OD) > Jingkai (ID), respectively.

(3) The source distribution characteristics of organic pollutants in indoor particulate matter were studied, and a combination of the C/N isotope tracing method, PCA, PMF, and the diagnostic ratio was proposed to study the sources of somewhat pollutants in indoor particulate matter. It was found that the sources of PAHs in indoor and outdoor dust were mainly combustion heat sources such as automobile exhaust, fossil fuel and biomass combustion, followed by construction dust and indoor anthropogenic activity effects. Indoor sources of PCBs in dust were industrial products, construction dust, and human activity emissions, while sources of PCBs in the outdoor particulate matter were road dust, atmospheric particles from transportation, fossil fuel and coal combustion, and biomass combustion, Sources of indoor OCPs were household hygiene pest control agents and animal ectoparasites, and sources of OCPs in outdoor particulate matter were pesticides for malaria and pest control, and construction ground works, cofferdams, grasslands and forests for termite control. Based on backward trajectory modeling of indoor sources of particulate matter in the study area, it was concluded that particulate matter in Hefei was mainly a mixture of local and regional long-range transport sources.

(4) Assessment of the health risk of exposure to organic pollutants in indoor and outdoor particulate matters suggests that the primary exposure route to PAHs for adults is dermal exposure. For children, it is primarily dietary exposure, while the risk of inhalation exposure for adults is 1-2 orders of magnitude greater than that for children for both indoor and outdoor exposure. This study also finds that the risk is low by analyzing the average daily dose (ADD) of PAHs in indoor and outdoor dust in Hefei. The non-carcinogenic health effects of exposure to PCBs in indoor and outdoor dust were found to be acceptable for all ages; the HI and TCR values for exposure to DL-PCBs were found to be greater than those for NDL-PCBs for indoor and outdoor residents of all ages. For indoor dust, the TCR for infants exposed to DL-PCBs and NDL-PCBs was greater than 1.00E-6 with a probability close to 5%; for outdoor dust, infants, children, adolescents, and adults exposed to NDL-PCBs had TCR values below 1.00E-6, and young children exposed to NDL-PCBs had TCRs greater than 1.00E-6 with a probability close to 5%. Hence, the classification of exposure to OCPs for adults and children follows the same trend: dietary (strong) > dermal > dietary (moderate) > inhalation.