Exposure and health risk assessment of PM2.5-bound polycyclic aromatic hydrocarbons during winter at residential homes: A case study in four Chinese cities.

Residential indoor PM2.5 were concurrently collected in Hong Kong, Guangzhou, Shanghai, and Xi'an during the winter and early spring seasons of 2016-2017, for updating the current knowledge of the spatial variation of indoor air pollution and the potential health risks in China. PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) were characterized, and the associated inhalation cancer risks were assessed by a probabilistic approach. Higher levels of indoor PAHs were identified in Xi'an residences (averaged at 176.27 ng m-3) with those of other cities ranging from 3.07 to 15.85 ng m-3. Traffic-related fuel combustion was identified as a common contributor to indoor PAHs through outdoor infiltration for all investigated cities. Indoor PAHs profiles showed city-specific differences, while distinctions between profiles based on indoor activities or ambient air quality were limited. Similar with the total PAHs concentrations, the estimated toxic equivalencies (TEQ) with reference to benzo[a]pyrene in Xi'an residences (median at 18.05 ng m-3) were above the recommended value of 1 ng m-3 and were magnitudes higher than the other investigated cities with estimated median TEQ ranging from 0.27 to 1.55 ng m-3. Incremental lifetime cancer risk (ILCR) due to PAHs inhalation exposure was identified with a descending order of adult (median at 8.42 × 10-8) > adolescent (2.77 × 10-8) > children (2.20 × 10-8) > senior (1.72 × 10-8) for different age groups. Considering the lifetime exposure-associated cancer risk (LCR), potential risks were identified for residents in Xi'an as an LCR level over 1 × 10-6 was identified for half of the adolescent group (median at 8.96 × 10-7), and exceedances were identified for about 90 % of the groups of adults (10th percentile at 8.29 × 10-7) and seniors (10th percentile at 1.02 × 10-6). The associated LCR estimated for other cities were relatively insignificant.

Effects of indoor activities and outdoor penetration on PM2.5 and associated organic/elemental carbon at residential homes in four Chinese cities during winter.

There is increasing public attention on exposure to PM2.5 and its related health impacts. It is essential to study the pollution levels, sources, and health implications of indoor PM2.5, especially for residential homes, as people tend to spend most of their time indoors. The indoor PM2.5 mass and organic/elemental carbon (OC/EC) during winter and early spring period of 2016-2017 at 68 residential households in four large Chinese cities (i.e. Hong Kong, Guangzhou, Shanghai, and Xi'an) were studied. Average indoor PM2.5 varied by two-fold, lowest in Hong Kong (34.0 ± 14.6 µg m-3) and highest in Xi'an (78.7 ± 49.3 µg m-3), with comparable levels for Guangzhou (47.2 ± 5.4 µg m-3) and Shanghai (50.3 ± 17.9 µg m-3). Lowest air exchange rate (AER, 0.8 ± 0.8 h-1) and PM2.5 indoor/outdoor (I/O) ratio (0.72 ± 0.23) were found for Xi'an households, indicating the limited influence from indoor sources, while importance of indoor PM2.5 sources is signified with the highest PM2.5 I/O ratio (1.32 ± 0.43) identified for Shanghai households. For households in four cities, OC and EC accounted for 29.5%-38.5% and 7.5%-8.9% of the indoor PM2.5 mass, indicating the significance of carbonaceous aerosols. Larger differences between indoor and outdoor OC (2.6-8.4%) than EC (-2.2-1.5%) indicate the presence of indoor OC sources. Decreasing trends of PM2.5 I/O ratio and indoor OC proportion were found as the worsening ambient air quality. On average, 11.8 µg m-3 (23.1%) and 3.02 µg m-3 (18.7%) higher indoor PM2.5 and OC concentrations were identified for households with other indoor combustions (e.g., tobacco smoking, incense burning) compared to those with only cooking activities. For Hong Kong and Shanghai households, increments of 13.2 µg m-3 (54.1%) of PM2.5 and 4.1 µg m-3 (45.4%) of OC were found at households with cooking activities as compared to households with no specific indoor combustion.

Human cancer risk estimation for 1,3-butadiene: An assessment of personal exposure and different microenvironments.

This study estimated the lifetime cancer risk (LCR) attributable to 1,3-butadiene (BD) personal exposure and to other microenvironments, including residential home, outdoor, in-office, in-vehicle, and dining. Detailed life expectancy by country (WHO), inhalation rate and body weight by gender reported by USEPA were used for the calculation, focusing on adult population (25≤Age<65). LCR estimation of the adult population due to personal exposure exceeded the USEPA benchmark of 1×10-6 in many cities. For outdoor BD exposure, LCR estimations in 45 out of 175 cities/sites (sharing 26%) exceeded the USEPA benchmark. Out of the top 20 cities having high LCR estimations, developing countries contributed 19 cities, including 14, 3, 1, 1 cities in China, India, Chile, and Pakistan. One city in the United States was in the list due to the nearby industrial facilities. The LCR calculations for BD levels found in residential home, in-vehicle and dining microenvironments also exceeded 1×10-6 in some cities, while LCR caused by in-office BD levels had the smallest risk. Four cities/regions were used for investigating source distributions to total LCR results because of their sufficient BD data. Home exposure contributed significantly to total LCR value (ranging 56% to 86%), followed by in-vehicle (4% to 38%) and dining (4 to 7%). Outdoor microenvironment shared highly in Tianjin with 6%, whereas in-office contributed from 2-3% for all cities. High LCR estimations found in developing countries highlighted the greater cancer risk caused by BD in other cities without available measurement data.