Occurrence of p-phenylenediamine antioxidants in human urine.

ABSTRACT

General populations are widely exposed to various p-phenylenediamine antioxidants (PPDs). N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), a typical p-phenylenediamine antioxidant, has been detected in human urine samples. However, the occurrence of other widely used PPDs in human urine is still unclear. This study comprehensively characterized the occurrence of 9 PPDs in human urine from 151 Chinese adults. Our results showed that all target PPDs were detected in human urine samples, with the total concentrations of PPDs ranging from 0.41 to 38 ng/mL. PPDs in human urine was dominated by 6PPD (mean 1.2 ng/mL, range < LOD - 3.8 ng/mL), followed by N-phenyl-N'-cyclohexyl-p-phenylenediamine (CPPD; 0.85 ng/mL, Female participants (1.4 ± 0.29 and 1.0 ± 0.22 ng/mL, respectively) exhibited significantly higher (p < 0.05) mean urinary concentrations of 6PPD and CPPD than male participants (1.0 ± 0.18 and 0.83 ± 0.18 ng/mL, respectively). Urinary concentrations of N, N'-diphenyl-p-phenylenediamine, CPPD, 7PPD, and 6PPD showed a general decreasing trend with the age of participants. In addition, daily excretion (DE) of PPDs in human urine was estimated, based on the urinary concentrations of detected PPDs. 6PPD had the highest mean DE (34 ng/kg bw/day), followed by CPPD (24 ng/kg bw/day) and 7PPD (19 ng/kg bw/day). To our knowledge, this study first reports the occurrence of 8 PPDs in human urine. More studies are needed to evaluate the toxic effects of human exposure to these PPDs.