Seasonal variation, sources, and risk assessment of PM2.5-bound PAHs in Nantong, China: A pre- and post-COVID-19 case study

Abstract

Between 2018 and 2022, a total of 231 PM2.5 samples were collected in Nantong, China, and analyzed online for 16 US EPA PAHs utilizing a variety of analytical methodologies, including high-performance liquid chromatography data analysis, principal component analysis, and characteristic ratio analysis. The seasonal variation and pollution characteristics of 16 PAHs in PM2.5 over a long period in Nantong, China, were analyzed, and correlations and traceability changes with a variety of emission sources were established. Additionally, health assessment models for BaP equivalent concentration, daily exposure dose, lifetime excess risk of cancer, and life expectancy loss were constructed for various ages and genders. The results indicated that the total number of days with BaP concentrations less than the national limit standard of 1.0 ng/m3 was 60.17% (139/231), with rates of 25.40%, 35.71%, and 94.05% from 2019 to 2021, respectively; the total concentration range of 16 PAHs demonstrated a downward trend, but pollution was relatively severe in winter. The seasonal variation showed winter > autumn > spring > summer. The detection rates of 4 and 5 rings were generally high and fluctuated between dropping and increasing. Principal factor analysis and characteristic ratio traceability analysis indicated that PAH pollution is primarily caused by local coal-fired sources and traffic emissions, with a new trend of biomass combustion. Furthermore, BaP remains the primary contributor to carcinogenic factors, and the health risk is higher in females than in males, and in adults than in children. A low level of PAHs in the air may have health benefits. Traffic control and flow restrictions, as well as production restrictions, are all part of Nantong’s COVID-19 pandemic prevention and control policies. These policies contributed to PAH risk prevention and control, as well as pollution reduction.

Characterization and Risk Assessment of PM2.5-Bound Polycyclic Aromatic Hydrocarbons and their Derivatives Emitted from a Typical Pesticide Factory in China

“…The ΣMEQ ranged from 3.60 to 41.09 ng/m 3 , with a mean value of 14.64 ± 12.41 ng/m 3 . These results are comparable to those observed for ambient air samples in Harbin (12.1 ng/m 3 ) [ 6 ] and Beijing (13.5 ng/m 3 ) [ 49 ] but higher than those observed in Nantong (0.09–0.37 ng/m 3 ) [ 31 ]. Additionally, no significant differences in both ΣTEQ and ΣMEQ values were observed between daytime and nighttime samples ( Figure 6 ).…”

“…These trend results are similar to those of other studies [ 7 , 19 , 41 ]. Low-molecular-weight PAHs with high Henry’s constants and vapor pressures mainly exist in the gas phase and are difficult to capture and collect, whereas middle-to-high-molecular-weight PAHs with low Henry’s constants and vapor pressures mainly exist in the particle phase [ 31 , 42 ]. Additionally, high-temperature processes (i.e., the combustion of fuels in industrial boilers in pesticide factories) emit high-molecular-weight PAHs to a greater extent than they emit low-molecular-weight PAHs [ 43 , 44 ].…”

“…The potential health effects of exposure to PM 2.5 -bound PAH emissions were assessed using carcinogenic-equivalent toxicity (TEQ), mutagenic-equivalent toxicity (MEQ), incremental lifetime cancer risk (ILCR), and loss of life expectancy (LLE). TEQ and MEQ represent carcinogenic risk at an equivalent concentration of benzo[a]pyrene (BaP) and are widely used to assess the total toxicity of PAHs [ 6 , 19 , 31 ]. ILCR is a model developed by the United States Environmental Protection Agency that is widely used to quantitatively estimate the risk of cancer caused by exposure to PM 2.5 -bound PAHs, and the model includes inhalation (ILCR Inhalation ), ingestion (ILCR Ingestion ), and dermal contact (ILCR Dermal ) [ 32 , 33 ].…”

“…The parameters used in the ILCR model in present study can be found in previous literature [ 1 , 32 , 34 , 35 , 36 ] and are listed in Supplementary Table S4 . LLE refers to the expected loss of life due to exposure to carcinogenic environmental pollutants [ 31 , 37 ]. Further information and details regarding the calculation methods used in the present study are provided in Supplementary Text S1 .…”