Three-tier sequential screening of key odor markers: transformation pathways and multi-dimensional health risk assessment in intensive swine farms.

Odor pollution from intensive swine production has become a prominent environmental issue that induces public complaints and health hazards. To accurately characterize odor profiles and quantify associated health risks, a typical large-scale swine farm in Tianjin, China, was selected as the study object. A total of 252 air samples were collected from 7 key functional units across four seasons. A three-tier sequential screening system was established by integrating instrumental analysis, sensory evaluation, and statistical correlation to identify characteristic odor markers. A three-dimensional health risk assessment framework was further developed from environmental, occupational, and livestock health perspectives. Results showed that 227 volatile organic compounds (VOCs) were identified, with sulfur compounds being the most abundant, followed by nitrogen-containing and oxygenated compounds. The manure treatment chain was identified as the dominant odor emission source. Six core odor markers were ultimately screened out: hydrogen sulfide, methyl mercaptan, acetic acid, isovaleric acid, p-cresol, and ammonia. These markers were mainly generated from microbial metabolism of sulfur-/nitrogen-containing organic matter. Health risk assessment revealed that hydrogen sulfide in manure treatment units posed significant non-carcinogenic risks to the environment and on-site workers, while risks in swine housing were well-controlled. This study provides a systematic methodology for precise identification, source tracing, and risk control of livestock odor pollution, supporting the green and sustainable development of intensive animal husbandry.