p-phenylenediamines (PPDs) and PPD-quinones (PPD-Qs) in human urine and breast milk samples: Urgent need for focus on PPD-Qs and the establishment of health threshold criteria

• Published in: Journal of hazardous materials Vol. 480; p. 136176
• Main Authors: Wu, Xiaoguo, Hu, Jiangshan, Yuan, Zijiao, Wang, Shanshan, Tong, Lei
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.12.2024
• Subjects: Breast milk; Daily intakes for infants; Difference among human population; PPDs and PPD-Qs; Urine; Urine; PPDs and PPD-Qs; Daily intakes for infants; Difference among human population; Breast milk
• ISSN: 0304-3894; 1873-3336; 1873-3336
• DOI: 10.1016/j.jhazmat.2024.136176

PPDs and their oxidation products, PPD-Qs, are emerging environmental contaminants arising from the addition and oxidation of rubber products. Although numerous studies have been conducted to elucidate their risks, the primary focus has been on 6PPD and 6PPD-Q, with limited attention given to other PPDs and especially other PPD-Qs. This study comprehensively examines the occurrences of frequently used PPDs and their degradation products, PPD-Qs, in human urine and breast milk samples. The average concentrations of ΣPPDs and ΣPPD-Qs in urine were 27 ± 78 ng/mL and 16 ± 12 ng/mL, respectively. IPPD and DNPD were the predominant PPDs, while DPPD-Q, CPPD-Q, and IPPD-Q were the predominant PPD-Qs. Notably, the concentrations of 6PPD, CPPD, and DPPD were significantly lower than their oxidized quinone products. Weak or no correlations were observed between most PPDs and their corresponding PPD-Qs, suggesting that PPD-Qs in the human body are primarily derived from direct environmental intake rather than in vivo conversion of PPDs. PPDs and PPD-Qs were widely detected in breast milk, exhibiting concentrations and patterns similar to those found in urine, with comparable major pollutants. Estimated daily intakes of PPDs + PPD-Qs for infants were several μg/(kg·day), with the 95th percentile intake approaching 10 μg/(kg·day). [Display omitted] •First extensive report of PPD-Qs in both urine and breast milk.•In urine: IPPD and DNPD were the major PPDs, DPPD-Q, CPPD-Q, and IPPD-Q were the major PPD-Qs.•In breast milk: PPDs and PPD-Qs presented similar concentrations and patterns to urine.•EDI of PPDs + PPD-Qs about 10 μg/(kg·day) for infants.