Characteristics and health risk assessment of monoaromatic hydrocarbons pollution in air above plastic runways

Monoaromatic hydrocarbons (MACHs) emitted from polyurethane (PU) plastic runways can pose health risks to individuals engaging in sports on or near these runways. However, the specific pollution characteristics and associated health risks of MACHs in the air above these runways remain poorly understood. This study investigated 22 newly constructed plastic runways in Hubei Province (aged 30–90 days) between August and September 2023. MACHs concentrations were identified and quantified using canister sampling coupled with preconcentration and gas chromatography-mass spectrometry (GC-MS). The health risks associated with MACHs exposure were assessed following the United States Environmental Protection Agency (US EPA) risk assessment framework. Sixteen MACHs compounds were consistently detected in the air above the plastic runways, with a detection rate of 100 %. The mass concentrations of the detected compounds followed this descending order: toluene (8.39 ± 7.76 μg/m³) > m-xylene/p-xylene (4.76 ± 4.29 μg/m³) > benzene (3.23 ± 1.86 μg/m³) > ethylbenzene (3.20 ± 2.78 μg/m³) > 1,2,4-trimethylbenzene (2.52 ± 3.44 μg/m³) > o-xylene (1.61 ± 1.41 μg/m³). Non-carcinogenic risks for the major MACHs compounds were ranked as follows: benzene > xylene isomers >1,2,4-trimethylbenzene >1,2,3-trimethylbenzene >1,3,5-trimethylbenzene > ethylbenzene > toluene. The hazard quotient (HQ) values for all detected compounds were below 1. Carcinogenic risk estimates for benzene and ethylbenzene fell within the range of 10⁻⁶ to 10⁻⁴. Benzene, toluene, ethylbenzene and xylenes (BTEX) concentrations above the plastic runways were higher than those typically observed in urban ambient air. However, both non-carcinogenic and carcinogenic risks were found to be similar to those in urban ambient air due to the lower exposure times and exposure frequency for people on plastic runways. While BTEX levels resembled those found near chemical industrial zones, they were markedly lower than concentrations within chemical industrial parks. Correspondingly, the associated health risks were significantly lower than those in industrial park environments. The findings suggest that the non-carcinogenic risk levels of MACHs were within acceptable thresholds, with benzene, xylene isomers, and 1,2,4-trimethylbenzene identified as primary contributors to non-carcinogenic effects. Carcinogenic risks posed by benzene and ethylbenzene were notable, suggesting potential health hazards with prolonged exposure, particularly for sensitive populations. BTEX-related health risks above plastic runways were comparable to those in urban environments but markedly lower than risks in underground garages or chemical industrial parks. This study supports the widespread use of plastic runways in public spaces but emphasizes the need for regular BTEX monitoring, public awareness of health risks, and appropriate exercise durations and intensities to mitigate potential risks.