A comprehensive assessment of VOCs from multi-story swine farms: Sources, mitigation, and integrated risks

As large-scale livestock farming expands and multi-story swine farms proliferate in China, the environmental and health impacts of volatile organic compounds (VOCs) from multi-story swine farms have become a vital concern. This study addresses gaps in farm-scale, year-round, multi-site VOCs characterization and the lack of pollutant-specific control guidance based on odor activity, mitigation practices, and environmental and health risks in multi-story swine farms. Year-round monitoring was conducted at six sites (swine house (SH), manure treatment area (MTA), rooftop (RT), living area (LA), upwind (UW), and downwind (DW)) across two representative multi-story swine farms. The results mapped the annual spatiotemporal profile of emissions, identifying SH and MTA as key sources, summer as the peak season, and oxygenated VOCs (OVOCs) as the dominant category. Odor activity value (OAV) was dominated by volatile sulfur compounds (VSCs) (>92%) at all sites, except at UW in autumn and winter where aromatic hydrocarbons and OVOCs prevailed. We quantified mitigation effectiveness, found that scraper manure cleaning method reduced annual mean VOC concentrations by 176.2 μg m^-3 compared with flushing manure cleaning method, and identified gestating sows and boars as high emitting groups requiring additional control. Aromatic hydrocarbons were the principal drivers of regional ozone (O₃) and secondary organic aerosol (SOA) formation, especially in summer at MTA. Occupational risk analysis showed that exposures to the carcinogens 1,2-dibromoethane and 1,2-dichloroethane and to the non-carcinogen dimethyl sulfide exceeded USEPA thresholds, demonstrating these compounds as priority pollutants. These advances support precise VOC control, sustainable and health protective management, standard setting and regulation, and promote a green, low carbon livestock industry development.