Pollution Characteristics, Source Identification And Ecological Risk Assessment Of PAHs In Indoor Dust In Shanghai

Polycyclic aromatic hydrocarbons (PAHs), as a serious of persistent organic pollutants, are ubiquitous in the environment. They draw great attention due to their properties of being residual, bioaccumulative, semi-volatile and of significant toxicity (toxic, teratogenic and mutagenic). The destruction brought to ecosystems by urban dust is hidden, potential and of long duration, and hazards of dust particles to the human body are direct, sometimes even fatal. As people spend more than 80% of the time in the indoor environment, research on indoor environmental pollution is gaining more and more attention. Indoor dust can easily become a carrier of pollutants directly or indirectly. It can be inhaled or ingested by human body, and induce various diseases. This study selects university campuses in Shanghai as the study area due to high population density. The present study focused on PAHs of indoor dusts from teaching buildings and dining halls. Combining the heterogeneous composition of urban dust, this paper revealed the characterization of its physical and chemical properties, traced sources of PAHs in dust by utilizing multi-parameter indicators, simulated the bioavailability of PAHs in indoor dust as the preliminary work, evaluated human exposure, and eventually assessed ecological and healthy risk of PAHs in indoor dust in order to provide a theoretical and scientific basis for the comprehensive management of urban persistent organic pollutants.The results of indoor dust in university campuses showed that, total PAH concentrations in dusts from teaching buildings ranged from 9.84-21.44μg/g, with a mean of 12.47μg/g, while PAH concentrations ranged form 9.63-44.13μg/g, with a mean of 19.63μg/g in dusts from dining halls. Carcinogenic component BaP was investigated and reached the level of heavy pollution in some dust samples from both teaching buildings and dining halls.Particle morphology observation showed that most particles were loose, rough and porous, indicating a certain absorption capacity, and can absorb many harmful substances. Round particles were found in most samples, and were speculated to be black carbon materials. Organic carbon and black carbon were significantly correlated with PAH concentrations, and BC contents showed better correlation.The results showed that the majority of PAHs components in teaching buildings were of common source, indicating that PAHs may be affected by the overall region environment. PAHs components in dining halls were found weaker correlation with each other, which showed that there was a variety of sources for PAHs in dining halls, and PAHs pollution in this area was significantly influenced by the unique environment of sampling sites. LMW/HMW values revealed that PAHs in indoor dusts from teaching buildings were mainly from petroleum products release and fossil fuels in incomplete combustion at low-medium temperature, with a small amount from fossil fuel combustion and pyrolysis release. While PAHs in dining halls were main fossil high temperature combustion and fuels pyrolysis source, and PAHs in some sites were from petroleum products and fossil fuels, incomplete combustion at low-medium temperature. Diagnostic ratios and principal component analysis indicated that PAHs in indoor dusts in Shanghai Universities were mainly from incomplete combustion of diesel oil and coal, as well as release of crude oil or coal products. Diesel oil and coal combustion, traffic oil emission contributed to 71.37 percent, and crude oil or coal products contributed to 16.39 percent of total PAHs in teaching buildings. Diesel oil combustion contributed to 57.69 percent, coal combustion contributed to 20.36 percent and crude oil or coal products contributed to 11.94 percent of total PAHs in dining halls. The results of diagnostic ratios were consistent with that of principal component analysis.To assess the bioavailability of PAHs, cooking oil was used to extract PAHs from indoor dust, and the results showed the PAHs dissolved were in limited quantities, and accounted for 1.5-2.03 percent of total PAHs in duss. Low level of PAHs dissolution may be related to the properties of black carbon, particle shape or lack of equilibrium distribution. Carcinogenic PAHs in indoor dust from dining halls dissolved more easily than that of teaching buildings, among which dissolved BaP proportion ranged 1.90-3.71 percent for teaching buildings, and 2.22-6.37 percent for dining halls, indicating that PAHs in dining halls constituted greater risk of human ingestion and corresponding human health threats can not be ignored.Compared to indoor PAH concentrations from other studies, Shanghai universities in the present study has been at a high level, and posed greater threat to human health and environment relative to the local outdoor environment. Compared to dustfall and outdoor dust in other regions, PAHs pollution level in Shanghai universities approximated to heavily polluted areas. Compared with PAHs governance standards for agricultural soil in Canada, evaluation and governance standards of soil PAHs in Netherlands and sediment quality standards and sediment management standards by the U.S.EPA, indoor dust in Shanghai universities has been polluted seriously by PAHs, and constituted great ecological risk. Calculations results of single factor pollution index and integrated pollution index for PAHs showed that indoor dust in Shanghai universities were seriously contaminated by both component and integrated pollution, posed high ecological risk and health threat for indoor environment and people. Results of PAHs EDI through oral ingestion for indoor dust in Shanghai universities indicated that maximum daily intake were toddlers (1-3 years old), while adults (≥19 years) ingested the minimum. Compared to teaching buildings, there was higher exposure risk of PAHs through oral ingestion in dining halls. Exposure risk through oral ingestion of PAHs in indoor dust in Shanghai universities was at a high level compared with EDI values of other regions. Results of EDI through inhalation showed low exposure risk for human, as well as the toxic risk. The fact that EDI values of inhalation were lower than that of oral ingestion implied oral ingestion could be the dominant exposure path to human for PAHs in indoor dust.