Source heterogeneity drives divergent VOC reactivity, toxicity, and odor impacts in rubber-processing enterprises.

Volatile organic compounds (VOCs) emissions from three representative rubber enterprises were systematically investigated through field sampling of both workshops and stack outlets. Process-dependent differences and source profiles of VOCs were investigated to assess their ozone formation potential (OFP), hazardous air pollutants (HAPs) burden, health risks, odor impacts, and stack derived emission factors (EFs). The recycled-rubber-based enterprise (EC) shared flue duct showed a total VOCs concentration of 176.6 mg/m3, approximately 9.0 times higher than the concentration of the virgin-rubber-based enterprise (EA) and mixed-rubber-based enterprise (EB) stack outlets, with the strongest process dependence and the most complex composition profile. The OFP from stack emissions were dominated mainly by aromatics (37-49%) in EA and alkanes (35-37%) in EB, whereas alkenes and oxygenated VOCs (64%) in EC. The analysis of HAPs further showed that toxicological significance did not necessarily track total VOCs abundance. The EC had the highest HAPs burden and the broadest toxic profile, while non-carcinogenic risk in all investigated units exceeded the benchmark level. Odor assessment indicated that rubber-processing workshops exhibited clear process-specific odor fingerprints, with acetaldehyde and other low-molecular-weight aldehydes identified as recurrent and important odor contributors, while EC workshops showed a more complex odor profile jointly driven by aldehydes, aromatic hydrocarbons, and other oxygenated VOCs. The field-derived EFs for organized discharges were lower than handbook estimates for the EB, but much higher for the EC. These findings highlight the need for process-specific VOCs control and more refined emission inventory development in the rubber industry.