Presence of 1, 3-diphenylguanidine and its derivatives in human urine and their human exposure.

Recent studies have demonstrated the widespread presence of 1,3-diphenylguanidine (DPG) and its derivatives in environmental matrices. While, the amount of human exposure to these rubber additives remains unclear. In this study, we collected human urine samples from healthy general adults (n = 221) living in Quzhou, China, and analyzed these samples for DPG and its five derivatives. DPG, 1,6-bis(cyano-guanidino)hexane (HCG), 1,3-di-o-tolylguanidine (DTG) and exhibited detection frequencies exceeding 50% in collected human urine. Presence of HCG, 1-(o-tolyl)biguanide (detection frequency 17%), and 1-(4-cyanophenyl)guanidine (6.0%) in human urine was also demonstrated for the first time. The highest mean human urinary concentration was found for DPG (0.89 ng/mL, < LOD-4.7 ng/mL), followed by DTG (0.57 ng/mL, < LOD-3.1 ng/mL) and HCG (0.34 ng/mL, < LOD-1.8 ng/mL). Male participants had consistently higher average human urinary levels of DPG, DTG, and HCG than female subjects, but none of these differences were significant (p > 0.10). DPG and DTQ consistently showed a decline in the human urinary concentrations as age of the participant increased. DPG (mean 170 ng/kg bw/day, median 137 ng/kg bw/day) had the highest human daily exposure amount, followed by DTG (106 ng/kg bw/day, 91 ng/kg bw/day) and HCG (58 ng/kg bw/day, 38 ng/kg bw/day). The study enhances our understanding of human exposure to these rubber additives, which is crucial for assessing their potential health risks.