Co-occurrence and distribution of organophosphate tri- and di-esters in dust and hand wipes from an e-waste dismantling plant in central China

Occupational exposure to traditional and emerging organophosphate esters: A comparison of levels across different sources and blood distribution

Currently, there is limited knowledge regarding occupational exposure of traditional and emerging organophosphate esters (OPEs) from e-waste and automobile dismantling activities, and their distribution within the human blood. In the present study, we collected dust and urine samples from e-waste (ED) (n = 91 and 130, respectively) and automobile dismantling (AD) plants (n = 93 and 94, respectively), as well as serum-plasma-whole blood samples (sets from 128 participants) within ED areas for analyzing traditional and emerging organophosphate tri-esters (tri-OPEs) and organophosphate di-esters (di-OPEs). Median concentration of ∑tri-OPEs and ∑di-OPEs in dust (37,400 and 9,000 ng/g in ED, and 27,000 and 14,700 ng/g in AD areas, respectively) and urine samples (11.8 and 21.9 ng/mL in ED areas, and 17.2 and 15.0 ng/mL in AD areas, respectively) indicated that both e-waste and automobile dismantling activities served as important pollution source for OPEs. Dust ingestion has been evidenced to be the main exposure pathway compared to dermal absorption and inhalation. The median concentration (ng/mL) of OPEs in blood matrices descended order as follow: whole blood (13.1) > serum (11.6) > plasma (10.4) for ∑tri-OPEs, and plasma (3.51) > serum (0.36) > whole blood (0.23) for ∑di-OPEs. Concentration ratios of OPEs varied across blood matrices, depending on the compounds, suggesting that the essentiality of appropriate biomonitoring matrix for conducting comprehensive exposure assessments.

Trans-Placental Transfer Mechanisms of Aromatic Amine Antioxidants (AAs) and p-Phenylenediamine Quinones (PPD-Qs): Evidence from Human Gestation Exposure and the Rat Uterine Perfusion Model

Aromatic amine antioxidants (AAs), as rubber additives, and their ozone photochemical oxidation products of p-phenylenediamine quinone (PPD-Qs) have attracted great attention recently due to their wide environmental occurrences and toxicity. However, there is currently no research on the exposure risks during pregnancy and their trans-placental transfer mechanisms. Herein, 20 AAs and six PPD-Qs were analyzed in 60 maternal urine and fifty-six amniotic fluid samples (n = 53 pairs). ΣAAs (median: 8.57 and 15.4 ng/mL) and ΣPPD-Qs (0.236 and 2.29 ng/mL) were both observed, where the median concentration of PPD-Qs was significantly (p < 0.05) higher than that of the parent PPDs (0.130 and 0.092 ng/mL) in the maternal urine and amniotic fluid samples, respectively. The result of the self-established rat uterine perfusion model and molecular docking analysis suggested that passive diffusion and active transport patterns were involved in the trans-placental transfer. This study will raise concerns regarding intrauterine exposure and the trans-placental transfer mechanisms to AAs/PPD-Qs during pregnancy.

Characterizing organophosphate esters and chlorinated paraffins in surface soils affected by diverse e-waste disassembling process in South China: Occurrence, distinct emission, and risk assessment

E-waste recycling activities are a crucial emission source of organic pollutants, posing potential risks to the surrounding environment and human health. To understand the potential impact related to diverse e-waste dismantling activities, we investigated two categories of popular flame retardants (i.e., organophosphate esters (OPEs) and chlorinated paraffins (CPs) and their resultant possible ecological risk in 53 surface soil samples from Qingyuan, a well-known e-waste recycling region in South China. Varied concentrations of ΣOPEs (20.5-8720 ng/g) and ΣCPs (920-16800 ng/g) were observed at diverse dismantling sites, while relatively low levels of ΣOPEs (6.13-1240 ng/g) and ΣCPs (14.8-2870 ng/g) were found in surrounding soils. These results indicated that primitive e-waste dismantling processes were the primary emission source of OPEs and CPs in the studied area, with e-waste dumping and manual dismantling being the most important emission sources for OPEs and CPs. More importantly, CPs could be degraded/transformed into more toxic intermediates via dechlorination and decarbonization during the burning of e-waste. Furthermore, our results indicated the potential ecological risks posed by OPEs and CPs related to e-waste recycling.

Dermal exposure assessment of formal e-waste dismantlers to flame retardants and plasticizers using passive sampling methodologies

The recycling of e-waste can lead to the release of organic chemicals when materials containing additives are subjected to dismantling and grinding. In this context, the exposure of workers from a Catalonian e-waste facility to flame retardants and plasticizers (including organophosphate esters (OPEs), polybrominated diphenyl ethers (PBDEs), novel brominated flame retardants (NBFRs) and dechloranes) was assessed using T-shirts and wristbands as passive samplers. The study area includes an area exclusively dedicated to cathodic ray-tube (CRT) TVs dismantling, and a grinding area where the rest of e-waste is ground. All the families of compounds were detected in both T-shirts and wristbands, with the highest concentration levels corresponding to OPEs, followed by PBDEs, NBFRs, and dechloranes. The CRT area presented higher concentration levels than the grinding area. The compounds with higher concentrations in T-shirts were 2-ethylhexyl diphenyl phosphate (EHDPP), diphenyl cresyl phosphate (DCP) and triphenyl phosphate (TPHP), and the total concentration of all groups ranged between 293 and 8324 ng/dm2-h (hour). In the case of the wristbands, the most abundant compounds were DCP, TPHP, and BDE-209, with total concentrations between 188 and 2248 ng/dm2-h. The two sampling methods appear to be complementary, as T-shirts collect coarser particles, while wristbands also capture volatile compounds. Based on normalized surface and time concentrations, the estimated daily intake (EDI) through dermal contact was calculated and carcinogenic and non-carcinogenic risks (CR and non-CR) associated with this activity assessed. The results show median CR 29 and 16 times below the threshold in CRT and grinding areas respectively. The non-CR medians were 2 and 3 times below the threshold, although in the CRT area one exceptional value surpassed the threshold, suggesting that risk can exist for some workers in the facility.

Comprehensive dietary exposure assessment of the Chinese population to organophosphate esters (OPEs): Results of the sixth China total diet study

Organophosphate esters (OPEs) are emerging pollutants, while data on their occurrence in foods and human dietary intake are limited. Based on the 6th China total diet study conducted in 2016-2019, this study implemented a comprehensive survey of OPEs in plant-derived foods of cereals, potatoes, legumes, fruits, vegetables, and further assessed dietary exposure from both plant- and animal-derived food. The sum concentrations of 15 OPEs in the plant-derived samples ranged from 0.567 to 106 ng/g ww. 2-Ethylhexyl diphenyl phosphate (EHDPP) (median: 1.14 ng/g ww) had the highest level in plant-derived foods, with a proportion of 35.6% in the total median OPEs. Regional distribution analysis showed a higher contamination of OPEs in plant-derived food from northern area of China. Estimated dietary intakes (EDIs) of ∑OPEs for Chinese population were from 109 ng/kg bw/day in Beijing to 1164 ng/kg bw/day in Gansu province, with mean and median of 296 and 222 ng/kg bw/day, respectively. Although animal-derived foods had higher levels of OPEs, plant-derived foods, specifically cereals, was the major source of dietary OPE intake. The EDIs were much lower than reference doses, which suggested the intakes of OPEs via food consumption could not cause significant health risks to the Chinese population at present.

Aromatic amine antioxidants (AAs) and p-phenylenediamines-quinones (PPD-Qs) in e-waste recycling industry park: Occupational exposure and liver X receptors (LXRs) disruption potential

Recently, evidence of aromatic amine antioxidants (AAs) existence in the dust of the electronic waste (e-waste) dismantling area has been exposed. However, there are limited studies investigating occupational exposure and toxicity associated with AAs and their transformation products (p-phenylenediamines-quinones, i.e., PPD-Qs). In this study, 115 dust and 42 hand wipe samples collected from an e-waste recycling industrial park in central China were analyzed for 19 AAs and 6 PPD-Qs. Notably, the median concentration of ∑6PPD-Qs (1,110 ng/g and 1,970 ng/m2) was significantly higher (p < 0.05, Mann-Whitney U test) than that of ∑6PPDs (147 ng/g and 34.0 ng/m2) in dust and hand wipes. Among the detected analytes, 4-phenylaminodiphenylamine quinone (DPPD-Q) (median: 781 ng/g) and 1,4-Bis(2-naphthylamino) benzene quinone (DNPD-Q) (median: 156 ng/g), were particularly prominent, which were first detected in the e-waste dismantling area. Occupational exposure assessments and nuclear receptor interference ability, conducted through estimated daily intake (EDI) and molecular docking analysis, respectively, indicated significant occupational exposure to PPD-Qs and suggested prioritized Liver X receptors (LXRs) disruption potential of PPDs and PPD-Qs. The study provides the first evidence of considerable levels of AAs and PPD-Qs in the e-waste-related hand wipe samples and underscores the importance of assessing occupational exposure and associated toxicity effects.

OPEs-ID: A software for non-targeted screening of organophosphate esters based on liquid chromatography-high-resolution mass spectrometry

Organophosphate esters (OPEs) are widely used as flame retardants and plasticizers, presenting a potential threat to the environment and human health. To date, no automatic software exists for the nontargeted screening of OPEs. In this study, OPEs-ID, a user-friendly software, was developed for the identification of OPEs using liquid chromatography-high-resolution mass spectrometry. The main workflow of OPEs-ID included fragments-dependent precursor ion screening, elemental composition determination, extracted ion chromatograms (EIC) comparison, and molecular structure identification via MetFrag strategy. A mixture of 17 OPE standards was identified with an identification rate of 100% by OPEs-ID. OPEs-ID demonstrated a rate of 94.1% for correctly ranking within the top 1 candidate in a local database (41.2% in PubChem) for the 17 OPE standards, which remarkably improved the identification when compared to conventional in silico fragmentation algorithms. Using a pooled airborne fine particle sample (PM2.5), OPEs-ID could automatically retrieve 22 valid molecules with structure candidates. The detection frequencies of 9 newly identified OPEs were between 13% and 100% in the 32 PM2.5 samples. Their semi-quantification concentrations were comparable to those of some traditional OPEs. Overall, OPEs-ID offers a powerful tool to significantly enrich our understanding of the OPEs present in the environment.