Incremental Lifetime Cancer Risk of PAHs in PM2.5 via Local Emissions and Long-Range Transport during Winter

Abstract

Our study covers the chemical characteristics and health risks of PM2.5 from 2019-2020 at National Taiwan University and City Tunnel in Taipei, Taiwan. Positive Matrix Factorization (PMF) was used to quantify the potential sources of polycyclic aromatic hydrocarbon (PAH). The influences of local pollution (LP), long range transport (LRT) and Power Plant are shown by using bivariate polar plot (BPP), Potential source contribution function (PSCF) and Enrichment Factor (EF) with Positive Matrix Factorization (PMF). Besides, chemical analysis included PAHs, carbonaceous species (OC/EC), water-soluble ions, and trace metals, respectively. Our results indicated that vehicle emissions (gasoline engines: 20.8%, diesel engines: 23.3%) and coal combustion (55.9%) were the major sources of PAHs in the urban site, with higher levels in LP than in LRT. The mean PM2.5 concentrations during the daytime was 13.0 ± 5.64 µg m-3, higher than 10.4 ± 5.16 µg m-3 at nighttime, reflecting high traffic emissions and anthropogenic aerosols during the day. Similar phenomenon was observed for PAHs in the daytime of 3.26 ± 2.36 ng m-3 and 1.91 ± 1.14 ng m-3 at nighttime. Also, due to higher NO3- and K levels, the ions and metals had higher values in the daytime and weekdays than at nighttime and weekends. In contrast, in the City Tunnel, the PM2.5 concentrations difference at the tunnel inlet and tunnel outlet during the daytime was significantly higher 36.4 µg m-3 compared to 27.4 µg m-3 at nighttime due to the heavy traffic during the day. As well, the OC/EC mass fractions at the tunnel inlet and tunnel outlet were 4.00 and 2.73. PSCF revealed a greater value (> 0.6) in the coastal areas of Inner Mongolia and Mainland China, due to long-range transport and industrial emissions. The incremental lifetime cancer risk (ILCR) of Cr6+ was higher in metal (2.60 × 10-5) but did not exceed its tolerable limits.