Workplace Presence and Exposure of p-Phenylenediamines and Their Quinones in Rubber Production

p-Phenylenediamines (PPDs), widely utilized as antioxidants in rubber products, have emerged as contaminants of environmental concern, yet their fate and associated health risks in rubber manufacturing environments remain poorly characterized. This study quantified the occurrence and estimated worker exposure based on settled dust concentrations of PPDs and their quinone derivatives (PPD-Qs) in two representative rubber manufacturing sectors, i.e., tire and seal factories, and the surrounding areas. Results showed that median concentrations of ∑PPDs (114 μg/g) and ∑PPD-Qs (354 μg/g) in indoor workshops far exceeded the levels in industrial park road dust (∑PPDs: 1.84 μg/g; ∑PPD-Qs: 0.410 μg/g) and surrounding road dust (∑PPDs: 219 ng/g; ∑PPD-Qs: 217 ng/g) in tire rubber factories. In addition, PPD and PPD-Q concentrations exhibited interfactory disparities (tire factories exceeding seal factories by 397-fold and 227-fold, respectively) and intrafactory variations (peaking in high-temperature/abrasion workshops), highlighting the necessity for targeted ventilation and protection. Distribution patterns differed by facility type, with concentrations halving within 0.3 km of plant boundaries. This study identifies rubber manufacturing, particularly large rubber tire plants, as a major source of PPDs and PPD-Qs, emphasizes the need for targeted worker protection and chemical management in high-emission zones such as mixing and vulcanizing workshops, and provides production-specific contamination profiles to guide effective regulatory and mitigation strategies.