Benzothiazoles and benzotriazoles in the dust and human urine samples from the e-waste recycling industry: occurrence, distribution, and occupational exposure assessment

Modern e-waste dismantling workshops showed substantially elevated BTH and BTR levels in indoor dust. • 2-OH-BTH predominated in dust, reaching 8100 ng/g in modern e-waste dismantling workshops. • 2-OH-BTH and 1-H-BTR dominated urinary profiles, with 1.8-fold higher concentrations in e-waste workers than rural residents. • BTH EDIs via dust ingestion were ∼ 24-fold higher in workers, yet dust contributed ≤2.33% of total exposure. • Significant intra- and inter-class correlations were observed for BTHs and BTRs in both dust and urine. Benzothiazoles (BTHs) and benzotriazoles (BTRs) are high production volume chemicals widely incorporated into electronic products, yet their environmental occurrence and potential occupational exposure during e-waste recycling remain poorly characterized. In this study, four BTHs and three BTRs were quantified in 113 dust samples collected from a modern e-waste recycling facility and 15 household dust samples, as well as in urine samples from 121 e-waste dismantling workers and 20 rural residents. The median Σ(BTHs+BTRs) in modern e-waste (e.g., cell phone) dismantling workshop dust (3000 ng/g) was approximately 9–10 times higher than that observed in traditional e-waste (e.g., refrigerator) dismantling workshop (350 ng/g), e-waste storage areas (260 ng/g) and suburb residential homes (300 ng/g). These findings indicate substantial accumulation of BTHs and BTRs in indoor dust associated with modern e-waste dismantling activities. 2-Hydroxybenzothiazole (2-OH-BTH) was the predominant congener in e-waste associated dust, accounting for more than 84–95% of Σ(BTHs+BTRs) across different microenvironments, compared with 73% in reference residential dust, suggesting relatively modest differences in congener profiles between recycling and residential environments. In urine, 2-OH-BTH and 1H-BTR were the predominant detected congeners, accounting for 83% and 67% of Σ(BTHs+BTRs) in workers and rural residents, respectively. Their median urinary concentrations in workers were 4.3 and 1.8 ng/mL, respectively, representing 1.8-fold higher levels than those in rural residents (2.4 and 1.0 ng/mL). Significant positive correlations were observed among BTHs, among BTRs, and between the two chemical classes in both dust and urine, suggesting shared or related exposure sources. The median estimated daily intake of BTHs through dust ingestion among workers was 2.60 ng/kg bw/day, approximately 24-fold higher than that estimated for rural residents (0.11 ng/kg bw/day), indicating elevated occupational exposure potential. Nevertheless, dust ingestion accounted for no more than 2.33% of the total BTH exposure estimated from urinary biomonitoring, suggesting that other exposure pathways may make greater contributions to overall internal exposure.