Human Internal Exposure to Rubber-Derived Chemicals – A Pilot Investigation

Recent studies have demonstrated the widespread occurrence of rubber-derived chemicals (RDCs) in the environment, raising global attention toward this group of emerging contaminants. However, few studies have systematically investigated human internal exposure to the RDCs. Herein, we screened for 21 emerging RDCs in plasma samples from pregnant women (n = 150), sanitation workers (n = 80), and rubber manufacturing workers (n = 162) to explore internal exposure to RDCs in these populations. The results revealed varying detection frequencies (DFs) and concentrations of selected RDCs among different populations. Specifically, N-isopropyl-N′-phenyl-p-phenylenediamine (IPPD), and N,N′-diphenyl-p-phenylenediamine (DPPD) exhibited high DF (>50%) across the three populations, but the levels differed significantly. While rubber manufacturing workers were found to have significantly higher levels of IPPD (median 0.41 ng/mL) than the other two populations (0.31 ng/mL for pregnant women and 0.22 ng/mL for sanitation workers), pregnant women contained the highest levels of DPPD (0.84 ng/mL versus 0.27 ng/mL for sanitation workers and 0.26 ng/mL for rubber manufacturing workers). In addition, five RDCs showed a DF higher than 50% of that in rubber manufacturing workers with age- and sex-specific distributions. These findings constitute a preliminary understanding of human exposure to RDCs, raising concerns about potential health effects.