Emerging N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) and 6PPD quinone in paired human plasma and urine from Tianjin, China: preliminary assessment with demographic factors

With increasing concerns about N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) and 6PPD-quinone (6PPD-Q), relevant environmental investigations and toxicological research have sprung up in recent years. However, limited information could be found for human body burden assessment. This work collected and analyzed 200 samples consisting of paired urine and plasma samples from participants (50 male and 50 female) in Tianjin, China. Low detection frequencies (DF, <15%) were found except for urinary 6PPD-Q (86%), which suggested the poor residue tendency of 6PPD and 6PPD-Q in blood. The low DFs also lead to no substantial association between two chemicals. Data analysis based on urinary 6PPD-Q showed a significant difference between males and females (p<0.05). No significant correlation was found for other demographic factors (Body Mass Index (BMI), age, drinking, and smoking). The mean values of daily excretion (ng/kg bw/day) calculated using urinary 6PPD-Q for females and males were 7.381 ng/kg bw/day (female) and 3.360 ng/kg bw/day (male), and apparently female suffered higher daily exposure. Further analysis with daily excretion and ALT (alanine aminotransferase)/TSH (thyroid stimulating hormone)/ blood cell analysis indicators found a potential correlation with 6PPD-Q daily excretion and liver/immune functions. Considering this preliminary assessment, systematic research targeting the potential organs at relevant concentrations is required. This is the first study to investigate the abundance of 6PPD and 6PPD-Q in paired plasma and urine samples. 6PPD and 6PPD-Q have already been a focus of attention as emerging contaminants. However, the information of 6-PPD and 6PPD-Q in human body remained unclear. In this work, the poor DF in plasma and relatively high DF in urine showed the importance of urinary excretion. The potential correlations between daily excretion of 6PPD-Q and ALT/ WBC suggested the effects on liver and immune function. This work provided epidemiological evidence of potential health effects of 6PPD and 6PPD-Q.