What question did this study set out to answer?

To assess pollution characteristics and health risks of volatile halogenated hydrocarbons in Mianyang, China.

April 30, 2026Toxics0 citationsOpen Access

Pollution Characteristics and Assessment of Carcinogenic and Non-Carcinogenic Risks of Volatile Halogenated Hydrocarbons in a Medium-Sized City of the Sichuan Basin, Southwest China

XWXia WanSouthwest University of Science and Technology XFXiaoxin FuSouthwest University of Science and Technology ZZZhou ZhangChinese Academy of Sciences

Key Points

To assess pollution characteristics and health risks of volatile halogenated hydrocarbons in Mianyang, China.
Field observations of atmospheric VHHs during summer in Mianyang.
Measurement of pollutants including chlorofluorocarbons and very short-lived chlorinated substances.
Risk assessment using positive matrix factorization to identify sources.
Carcinogenic risk surpassed acceptable thresholds, notably driven by 1,2-dichloroethane.
Chloromethane and methylene chloride concentrations were significantly elevated compared to global levels.
Cumulative hazard index indicated combined non-carcinogenic risks to the local population.

Abstract

Volatile halogenated hydrocarbons (VHHs) are critical air toxic pollutants, with some ozone-depleting substances (ODSs) strictly regulated by the Montreal Protocol. However, current understanding of the pollution characteristics, sources, and health risks of atmospheric VHHs in Southwest China remains insufficient. This study performed field observations of atmospheric VHHs in summer in Mianyang, a medium-sized industrial city in the Sichuan Basin. Freon-12 (563 ± 20 ppt) and Freon-11 (264 ± 15 ppt) were the most abundant chlorofluorocarbons (CFCs); chloromethane (785 ± 261 ppt) and methylene chloride (563 ± 505 ppt) dominated among VSLSs. The mean concentration of regulated ODSs (1037 ± 33 pptv) was notably lower than unregulated very short-lived chlorinated substances (1887 ± 745 pptv), reflecting effective ODSs phase-out locally, yet enhancements relative to Northern Hemisphere background implied potential leakage from residual tanks. Methylene chloride and trichloroethylene concentrations exceeded global background levels by over 10 times, indicating strong anthropogenic industrial influences. Phased-out CFCs displayed negligible diurnal variation due to stringent emission controls, whereas unregulated VSLSs exhibited a distinct U-shaped diurnal cycle, with peaks driven by morning boundary layer dynamics and evening accumulation. Positive matrix factorization revealed that industrial sources, including electronic solvents (28.6%), industrial processes (27.8%), and solvent usage (23.7%), accounted for 80.1% of total VHHs. The total carcinogenic risk (2.3 × 10−5) surpassed the acceptable threshold (1 × 10−6), dominated by 1,2-dichloroethane, chloroform, carbon tetrachloride, and 1,2-dichloropropane. All individual compounds exhibited mean hazard quotients (HQs) below the non-carcinogenic risk threshold. The cumulative hazard index reached 1.5, suggesting combined non-carcinogenic risks to the local population. These results support VHHs health risk management and ODSs control in Southwest Chinese industrial cities.

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