Effect of E-waste Recycling on Urinary Metabolites of Organophosphate Flame Retardants and Plasticizers and Their Association with Oxidative Stress

A review of the present methods used to remediate soil and water contaminated with organophosphate esters and developmental directions

Organophosphate esters (OPEs) are widely used commercial additives, but their environmental persistence and toxicity raise serious concerns necessitating associated remediation strategies. Although there are various existing technologies for OPE removal, comprehensive screening for them is urgently needed to guide further research. This review provides a comprehensive overview of the techniques used to remove OPEs from soil and water, including their related influencing factors, removal mechanisms/degradation pathways, and practical applications. Based on an analysis of the latest literature, we concluded that (1) methods used to decontaminate OPEs include adsorption, hydrolysis, photolysis, advanced oxidation processes (AOPs), activated sludge processes, and microbial degradation; (2) factors such as the quantity/characteristics of the catalysts/additives, pH value, inorganic ion concentration, and natural organic matter (NOM) affect OPE removal; (3) primary degradation mechanisms involve oxidation induced by reactive oxygen species (ROS) (including •OH and SO4•-) and degradation pathways include hydrolysis, hydroxylation, oxidation, dechlorination, and dealkylation; (5) interference from the pH value, inorganic ion and the presence of NOM may limit complete mineralization during the treatment, impacting practical application of OPE removal techniques. This review provides guidance on existing and potential OPE removal methods, providing a theoretical basis and innovative ideas for developing more efficient and environmentally friendly techniques to treat OPEs in soil and water.

Weight of evidence evaluation of the metabolism disrupting effects of triphenyl phosphate using an expert knowledge elicitation approach

Identification of Endocrine-Disrupting Chemicals (EDCs) in a regulatory context requires a high level of evidence. However, lines of evidence (e.g. human, in vivo, in vitro or in silico) are heterogeneous and incomplete for quantifying evidence of the adverse effects and mechanisms involved. To date, for the regulatory appraisal of metabolism-disrupting chemicals (MDCs), no harmonised guidance to assess the weight of evidence has been developed at the EU or international level. To explore how to develop this, we applied a formal Expert Knowledge Elicitation (EKE) approach within the European GOLIATH project. EKE captures expert judgment in a quantitative manner and provides an estimate of uncertainty of the final opinion. As a proof of principle, we selected one suspected MDC -triphenyl phosphate (TPP) - based on its related adverse endpoints (obesity/adipogenicity) relevant to metabolic disruption and a putative Molecular Initiating Event (MIE): activation of peroxisome proliferator activated receptor gamma (PPARγ). We conducted a systematic literature review and assessed the quality of the lines of evidence with two independent groups of experts within GOLIATH, with the objective of categorising the metabolic disruption properties of TPP, by applying an EKE approach. Having followed the entire process separately, both groups arrived at the same conclusion, designating TPP as a "suspected MDC" with an overall quantitative agreement exceeding 85%, indicating robust reproducibility. The EKE method provides to be an important way to bring together scientists with diverse expertise and is recommended for future work in this area.

E-waste: mechanisms of toxicity and safety testing

Currently, information on the toxicity profile of the majority of the identified e-waste chemicals, while extensive and growing, is admittedly fragmentary, particularly at the cellular and molecular levels. Furthermore, the toxicity of the chemical mixtures likely to be encountered by humans during and after informal e-waste recycling, as well as their underlying mechanisms of action, is largely unknown. This review paper summarizes state-of-the-art knowledge of the potential underlying toxicity mechanisms associated with e-waste exposures, with a focus on toxic responses connected to specific organs, organ systems, and overall effects on the organism. To overcome the complexities associated with assessing the possible adverse outcomes from exposure to chemicals, a growing number of new approach methodologies have emerged in recent years, with the long-term objective of providing a human-based and animal-free system that is scientifically superior to animal testing, more effective, and acceptable. This encompasses a variety of techniques, typically regarded as alternative approaches for determining chemical-induced toxicities and holds greater promise for a better understanding of key events in the metabolic pathways that mediate known adverse health outcomes in e-waste exposure scenarios. This is crucial to establishing accurate scientific knowledge on mixed e-waste chemical exposures in shorter time frames and with greater efficacy, as well as supporting the need for safe management of hazardous chemicals. The present review paper discusses important gaps in knowledge and shows promising directions for mechanistically anchored effect-based monitoring strategies that will contribute to the advancement of the methods currently used in characterizing and monitoring e-waste-impacted ecosystems.

Estimated daily intake and cumulative risk assessment of organophosphate esters and associations with DNA damage among e-waste workers in Hong Kong

Organophosphate esters (OPEs) are extensively used as additives in various products, including electronic equipment, which becomes e-waste when obsolete. Nevertheless, no study has evaluated OPEs exposure levels and the related health risks among e-waste workers in Hong Kong. Therefore, 201 first-spot morning urine samples were collected from 101 e-waste workers and 100 office workers to compare eight urinary OPE metabolites (mOPEs) levels in these groups. The concentrations of six mOPEs were similar in e-waste workers and office workers, except for significantly higher levels of diphenyl phosphate (DPHP) in e-waste workers and bis(1-chloro-2propyl) phosphate (BCIPP) in office workers. Spearman correlation analysis showed that most non-chlorinated mOPEs were correlated with each other in e-waste workers (i.e., nine out of ten pairs, including di-p-cresyl phosphate (DpCP) and di-o-cresyl phosphate (DoCP), DpCP and bis(2-butoxyethyl) phosphate (BBOEP), DpCP and DPHP, DpCP and dibutyl phosphate (DBP), DoCP and BBOEP, DoCP and DPHP, DoCP and DBP, BBOEP and DPHP, DPHP and DBP), indicating that handling e-waste could be the exposure source of specific OPEs. The median values of estimated daily intake (EDI) and hazard quotient (HQ) suggested that the health risks from OPEs exposures were under the recommended thresholds. However, linear regression models, Quantile g-computation, and Bayesian kernel machine regression found that urinary mOPEs elevated 8-hydroxy-2-deoxyguanosine (8-OhdG) levels individually or as a mixture, in which DPHP contributed prominently. In conclusion, although e-waste might not elevate the internal OPEs levels among the participating Hong Kong e-waste workers, attention should be paid to the potential DNA damage stimulated by OPEs under the currently recommended thresholds.

Biomarkers of Organophosphate and Polybrominated Diphenyl Ether (PBDE) Flame Retardants of American Workers and Associations with Inhalation and Dermal Exposures

This study evaluated workers' exposures to flame retardants, including polybrominated diphenyl ethers (PBDEs), organophosphate esters (OPEs), and other brominated flame retardants (BFRs), in various industries. The study aimed to characterize OPE metabolite urinary concentrations and PBDE serum concentrations among workers from different industries, compare these concentrations between industries and the general population, and evaluate the likely route of exposure (dermal or inhalation). The results showed that workers from chemical manufacturing had significantly higher (p <0.05) urinary concentrations of OPE metabolites compared to other industries. Spray polyurethane foam workers had significantly higher (p <0.05) urinary concentrations of bis(1-chloro-2-propyl) phosphate (BCPP) compared to other industries. Electronic scrap workers had higher serum concentrations of certain PBDE congeners compared to the general population. Correlations were observed between hand wipe samples and air samples containing specific flame-retardant parent chemicals and urinary metabolite concentrations for some industries, suggesting both dermal absorption and inhalation as primary routes of exposure for OPEs. Overall, this study provides insights into occupational exposure to flame retardants in different industries and highlights the need for further research on emerging flame retardants and exposure reduction interventions.

Investigation of Urinary Metabolites of Organophosphate Esters in Hanoi, Vietnam: Assessment Exposure and Estimated Daily Intake

In recent years, organophosphate esters (OPEs) have become one of the most common additives in various consumer products worldwide, therefore the exposure and impact of OPEs on human health are drawing a lot of attention. In this study, three metabolites of OPEs including bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), diphenyl phosphate (DPhP) and diethyl phosphate (DEP) were investigated in first-morning void urine samples taken from a population (age range: 3-76 years old) in Hanoi, Vietnam. The most dominant urinary OPE metabolite was DEP with the geometric mean of specific gravity adjust (SG-adjusted) concentration were 1960 ng mL-1 and detected frequency (DF) of 98%. Followed by DPhP (8.01 ng mL-1, DF: 100%) and BDCIPP (2.18 ng mL-1, DF: 51%). The results indicated that gender and age might have associations with the OPE metabolites variation in urine samples. The levels of OPE metabolites in urine samples from females were slightly higher than in males. An increase in age seems to have an association with a decrease in DPhP levels in urine. Exposure doses of parent OPEs were evaluated from the unadjusted urinary concentration of corresponding OPE metabolite. The estimated exposure doses of triethyl phosphate (TEP) (mean: 534,000 ng kg-1 d-1) were significantly higher than its corresponding reference dose, suggesting the high potential risk from the current exposure doses of TEP to human health. The results of this work provided the initial information on the occurrence of three OPE metabolites in urine from Hanoi, Vietnam and estimated exposure dose of corresponding parent OPEs.

Quantitative identification of the co-exposure effects of e-waste pollutants on human oxidative stress by explainable machine learning

Global electronic waste (e-waste) generation continues to grow. The various pollutants released during precarious e-waste disposal activities can contribute to human oxidative stress. This study encompassed 129 individuals residing near e-waste dismantling sites in China, with elevated urinary concentrations of e-waste-related pollutants including heavy metals, polycyclic aromatic hydrocarbons (PAHs), organophosphorus flame retardants (OPFRs), bisphenols (BPs), and phthalate esters (PAEs). Utilizing an explainable machine learning framework, the study quantified the co-exposure effects of these pollutants, finding that approximately 23% and 18% of the variance in oxidative DNA damage and lipid peroxidation, respectively, was attributable to these substances. Heavy metals emerged as the most critical factor in inducing oxidative stress, followed by PAHs and PAEs for oxidative DNA damage, and BPs, OPFRs, and PAEs for lipid peroxidation. The interactions between different pollutant classes were found to be weak, attributable to their disparate biological pathways. In contrast, the interactions among congeneric pollutants were strong, stemming from their shared pathways and resultant synergistic or additive effects on oxidative stress. An intelligent analysis system for e-waste pollutants was also developed, which enables more efficient processing of large-scale and dynamic datasets in evolving environments. This study offered an enticing peek into the intricacies of co-exposure effect of e-waste pollutants.

Association between organophosphate flame retardant exposure and lipid metabolism: data from the 2013-2014 National Health and Nutrition Examination Survey

Organophosphate flame retardants (OPFRs) are emerging environmental pollutants that can be detected in water, dust, and biological organisms. Certain OPFRs can disrupt lipid metabolism in animal models and cell lines. However, the effects of OPFRs on human lipid metabolism remain unclear. We included 1,580 participants (≥20 years) from the 2013-2014 National Health and Nutrition Examination Survey (NHANES) to explore the relationship between OPFR exposure and lipid metabolism biomarkers. After adjusting for confounding factors, results showed that one-unit increases in the log levels of diphenyl phosphate (DPhP) (regression coefficient = -5.755; S.E. = 2.289; p = 0.023) and log bis-(1-chloro-2-propyl) phosphate (BCPP) (regression coefficient = -4.637; S.E. = 2.019; p = 0.036) were negatively associated with the levels of total cholesterol (TC) in all participants. One-unit increases in the levels of DPhP (regression coefficient = -2.292; S.E. = 0.802; p = 0.012), log bis (1,3-dichloro-2-propyl) phosphate (BDCPP) (regression coefficient = -2.046; S.E. = 0.825; p = 0.026), and log bis-2-chloroethyl phosphate (BCEP) (regression coefficient = -2.604; S.E. = 0.704; p = 0.002) were negatively associated with the levels of high-density lipoprotein cholesterol (HDL-C). With increasing quartiles of urine BDCPP levels, the mean TC levels significantly decreased in all participants (p value for trend = 0.028), and quartile increases in the levels of DPhP (p value for trend = 0.01), BDCPP (p value for trend = 0.001), and BCEP (p value for trend<0.001) were negatively corelated with HDL-C, with approximately 5.9, 9.9, and 12.5% differences between the upper and lower quartiles. In conclusion, DPhP, BDCPP, and BCEP were negatively related to HDL-C concentration, whereas DPhP and BCPP levels were negatively associated with TC level. Thus, exposure to OPFRs may interfere with lipid metabolism.

Critical review on organophosphate esters in water environment: Occurrence, health hazards and removal technologies

Organophosphate esters (OPEs), which are phosphoric acid ester derivatives, are anthropogenic substances that are widely used in commerce. Nevertheless, there is growing public concern about these ubiquitous contaminants, which are frequently detected in contaminated water sources. OPEs are mostly emitted by industrial operations, and the primary routes of human exposure to OPEs include food intake and dermal absorption. Because of their negative effects on both human health and the environment, it is clear that innovative methods are needed to facilitate their eradication. In this study, we present a comprehensive overview of the existing characteristics and origins of OPEs, their possible impacts on human health, and the merits, drawbacks, and future possibilities of contemporary sophisticated remediation methods. Current advanced remediation approaches for OPEs include adsorption, degradation (advanced oxidation, advanced reduction, and redox technology), membrane filtration, and municipal wastewater treatment plants, degradation and adsorption are the most promising removal technologies. Meanwhile, we proposed potential areas for future research (appropriate management approaches, exploring the combination treatment process, economic factors, and potential for secondary pollution). Collectively, this work gives a comprehensive understanding of OPEs, providing useful insights for future research on OPEs pollution.

Association between urinary organophosphate ester metabolite exposure and thyroid disease risk among US adults: National Health and Nutrition Examination Survey 2011-2014

Background

Organophosphate esters (OPEs) may interfere with thyroid function, but the relationship between OPEs and thyroid disease remains unclear. This study aims to elucidate the relationship between OPEs exposure and thyroid disease risk in the general population in the United States.

Method

Data were obtained from the 2011-2014 National Health and Nutrition Examination Survey cycle. All participants were tested for seven OPE metabolites in their urine and answered questions about whether they had thyroid disease through questionnaires. Logistic regression was employed to analyze the association between exposure to individual OPE metabolites and thyroid disease. Weighted Quantile Sum (WQS) regression modeling was utilized to assess exposure to mixed OPE metabolites and risk of thyroid disease. Bayesian kernel machine regression(BKMR) models to analyze the overall mixed effect of OPE metabolites.

Result

A total of 2,449 participants were included in the study, 228 of whom had a history of thyroid disease. Bis(1,3-dichloro-2-propyl) phos (BDCPP), Diphenyl phosphate (DPHP) and Bis(2-chloroethyl) phosphate (BCEP) were the top three metabolites with the highest detection rates of 91.75%, 90.77% and 86.57%, respectively. In multivariate logistic regression models, after adjustment for confounding variables, individuals with the highest tertile level of BCEP were significantly and positively associated with increased risk of thyroid disease (OR=1.57, 95% CI=1.04-2.36), using the lowest tertile level as reference. In the positive WQS regression model, after correcting for confounding variables, mixed exposure to OPE metabolites was significantly positively associated with increased risk of thyroid disease (OR=1.03, 95% CI=1.01-1.06), with BCEP and DPHP having high weights. In the BKMR model, the overall effect of mixed exposure to OPE metabolites was not statistically significant, but univariate exposure response trends showed that the risk of thyroid disease decreased and then increased as BCEP exposure levels increased.

Conclusion

The study revealed a significant association between exposure to OPE metabolites and an increased risk of thyroid disease, with BCEP emerging as the primary contributor. The risk of thyroid disease exhibits a J-shaped pattern, whereby the risk initially decreases and subsequently increases with rising levels of BCEP exposure. Additional studies are required to validate the association between OPEs and thyroid diseases.

Organophosphate Esters in Building Materials from China: Levels, Sources, Emissions, and Preliminary Assessment of Human Exposure

Source characteristics and health risks of indoor organophosphate esters (OPEs) are limited by the lack of knowledge on emission processes. This study attempted to integrate the contents and emissions of OPEs from indoor building materials to assess human health effects. Thirteen OPEs were investigated in 80 pieces of six categories of building materials. OPEs are ubiquitous in the building materials and ∑13OPE contents varied significantly (p < 0.05) from 72.8 ng/g (seam agent) to 109,900 ng/g (wallpaper). Emission characteristics of OPEs from the building materials were examined based on a microchamber method. Depending on the sample category, the observed initial area-specific emission rates of ∑13OPEs varied from 154 ng/m2/h (carpet) to 2760 ng/m2/h (wooden floorboard). Moreover, the emission rate model was developed to predict the release levels of individual OPEs, quantify source contributions, and assess associated exposure risks. Source apportionments of indoor OPEs exhibited heterogeneities in multiple environmental media. The joint OPE contribution of wallpaper and wooden floorboard to indoor dust was up to 94.8%, while latex paint and wooden floorboard were the main OPE contributors to indoor air (54.2%) and surface (76.1%), respectively. Risk assessment showed that the carcinogenic risks of tris(2-chloroethyl) phosphate (3.35 × 10-7) were close to the acceptable level (1 × 10-6) and deserved special attention.

Organophosphate Triesters and Their Transformation Products in Sediments of Mangrove Wetlands in the Beibu Gulf, South China Sea

As emerging pollutants, organophosphate esters (OPEs) have been reported in coastal environments worldwide. Nevertheless, information on the occurrence and ecological risks of OPEs, especially the related transformation products, in mangrove wetlands is scarce. For the first time, the coexistence and distribution of OP triesters and their transformation products in three mangrove wetlands in the Beibu Gulf were investigated using ultrasonication and solid-phase extraction, followed by UHPLC-MS/MS detection. The studied OPEs widely existed in all the sampling sites, with the total concentrations ranging from 6.43 ng/g dry weight (dw) to 39.96 ng/g dw and from 3.33 ng/g dw to 22.50 ng/g dw for the OP triesters and transformation products, respectively. Mangrove wetlands tend to retain more OPEs than the surrounding coastal environment. Pearson correlation analysis revealed that the TOC was not the sole factor in determining the OPEs' distribution, and degradation was not the main source of the transformation products in mangrove sediments in the Beibu Gulf. The ecological risks of selected OPEs for different organisms were also assessed, revealing a medium to high risk posed by OP diesters to organisms. The levels or coexistence of OPEs and their metabolites in mangroves need constant monitoring, and more toxicity data should be further studied to assess the effect on normal aquatic organisms.

Physiologically based toxicokinetic modelling of Tri(2-chloroethyl) phosphate (TCEP) in mice accounting for multiple exposure routes

Exposure routes are important for health risk assessment of chemical risks. The application of physiologically based toxicokinetic (PBTK) models to predict concentrations in vivo can determine the effects of harmful substances and tissue accumulation on the premise of saving experimental costs. In this study, Tri(2-chloroethyl) phosphate (TCEP), an organophosphate ester (OPE), was used as an example to study the PBTK model of mice exposed to different exposure doses by multiple routes. Different routes of exposure (gavage and intradermal injection) can cause differences in the concentration of chemicals in the organs. TCEP that enters the body through the mouth is mainly concentrated in the gastrointestinal tract and liver. However, the concentrations of chemicals that enter the skin into the mice are higher in skin, rest of body, and blood. In addition, TCEP was absorbed and accumulated very rapidly in mice, within half an hour after a single exposure. We have successfully established a mouse PBTK model of the TCEP accounting for multiple exposure Routes and obtained a series of kinetic parameters. The model includes blood, liver, kidney, stomach, intestine, skin, and rest of body compartments. Oral and dermal exposure route was considered for PBTK model. The PBTK model established in this study has a good predictive ability. More than 70% of the predicted values deviated from the measured values by less than 5-fold. In addition, we extrapolated the model to humans. A human PBTK model is built. We performed a health risk assessment for world populations based on human PBTK model. The risk of TCEP in dust is greater through mouth than through skin. The risk of TCEP in food of Chinese population is greater than dust.

Face mask as an indicator and shield of human exposure to traditional and novel organophosphate esters

Herein, the trapping effectiveness of N95, filter KN95, medical surgical masks (MSMs), and disposable medical masks (DMMs) against 19 airborne traditional and novel organophosphate esters (OPEs) was evaluated. Laboratory simulations (n = 24 for each type of mask) showed that time-dependent accumulation of ∑19OPEs on the four types of masks ranged between 30.1 and 86.6 ng in 24 h, with the highest and lowest median amounts trapped by the N95 masks (53.3 ng) and DMMs (43.2 ng), respectively. The trapping efficiency of the four types of masks for ∑19OPEs decreased over time from 84 % to 39 % in 24 h, with N95 masks showing the highest median efficiency (70 %). Further, field investigations were conducted in five types of microenvironments (train, hospital, bus, supermarket, and canteen), and an analysis of 200 samples showed that ∑19OPEs were accumulated in the masks with a variable amount from 3.7 to 117 ng/mask. Consistent with the laboratory simulations, the N95 masks (29.0 ng/mask) exhibited the highest hourly median amount of trapped OPEs, followed by the KN95 masks (24.5 ng/mask), MSMSs (17.4 ng/mask), and DMMs (15.8 ng/mask). Triethyl phosphate (TEP), tris(1-chloro-2-propyl) phosphate (TCIPP), tri-n-butyl phosphate (TNBP), and cresyl diphenyl phosphate (CDP) as well as 4-isopropylphenyl diphenyl phosphate (4IPPDPP) and 2,4-diisopropylphenyl diphenyl phosphate (24DIPPDPP) were the most commonly detected traditional and novel OPEs. Based on the amount of OPEs trapped on the masks, we estimated the concentration of ∑19OPEs in the train microenvironment to be the highest (222 ng/m3), which is approximately 2-5 times higher than that in the other microenvironments. The results of this study prove that masks can effectively protect humans from exposure to OPEs and act as low-cost indicators of indoor contamination.

Associations of Organophosphate Ester Flame Retardant Exposures during Pregnancy with Gestational Duration and Fetal Growth: The Environmental influences on Child Health Outcomes (ECHO) Program

BACKGROUND

Widespread exposure to organophosphate ester (OPE) flame retardants with potential reproductive toxicity raises concern regarding the impacts of gestational exposure on birth outcomes. Previous studies of prenatal OPE exposure and birth outcomes had limited sample sizes, with inconclusive results.

OBJECTIVES

We conducted a collaborative analysis of associations between gestational OPE exposures and adverse birth outcomes and tested whether associations were modified by sex.

METHODS

We included 6,646 pregnant participants from 16 cohorts in the Environmental influences on Child Health Outcomes (ECHO) Program. Nine OPE biomarkers were quantified in maternal urine samples collected primarily during the second and third trimester and modeled as log 2 -transformed continuous, categorized (high/low/nondetect), or dichotomous (detect/nondetect) variables depending on detection frequency. We used covariate-adjusted linear, logistic, and multinomial regression with generalized estimating equations, accounting for cohort-level clustering, to estimate associations of OPE biomarkers with gestational length and birth weight outcomes. Secondarily, we assessed effect modification by sex.

RESULTS

Three OPE biomarkers [diphenyl phosphate (DPHP), a composite of dibutyl phosphate and di-isobutyl phosphate (DBUP/DIBP), and bis(1,3-dichloro-2-propyl) phosphate] were detected in > 85 % of participants. In adjusted models, DBUP/DIBP [odds ratio (OR) per doubling = 1.07 ; 95% confidence interval (CI): 1.02, 1.12] and bis(butoxyethyl) phosphate (OR for high vs. nondetect = 1.25 ; 95% CI: 1.06, 1.46), but not other OPE biomarkers, were associated with higher odds of preterm birth. We observed effect modification by sex for associations of DPHP and high bis(2-chloroethyl) phosphate with completed gestational weeks and odds of preterm birth, with adverse associations among females. In addition, newborns of mothers with detectable bis(1-chloro-2-propyl) phosphate, bis(2-methylphenyl) phosphate, and dipropyl phosphate had higher birth weight-for-gestational-age z -scores (β for detect vs. nondetect = 0.04 - 0.07 ); other chemicals showed null associations.

DISCUSSION

In the largest study to date, we find gestational exposures to several OPEs are associated with earlier timing of birth, especially among female neonates, or with greater fetal growth. https://doi.org/10.1289/EHP13182.

Organophosphorus flame retardants and their metabolites in paired human blood and urine

Organophosphorus flame retardants (OPFRs) have been shown to be carcinogenic, neurotoxic, and endocrine disruptive, so it is important to understand the levels of OPFRs in human body as well as the modes of external exposure. In this study, we investigated the levels of 13 OPFRs and 7 phosphodiester metabolites in paired human blood and urine, as well as the influencing factors (region, age and gender), and studied the relationship between OPFRs and oxidative stress by urinary metabolites. We found that the concentrations of triphenyl phosphate (TPhP) and tris-(2-ethylhexyl) phosphate (TEHP) in the blood of urban populations were higher than those of rural populations, and that younger populations suffered higher TPhP and 2-ethylhexyl diphenyl phosphate (EHDPP) exposures than older populations. In addition, we found that tris-(2-chloroethyl) phosphate (TCEP), tributyl phosphate (TnBP), TPhP and EHDPP exposure induced oxidative stress. The results of the internal load principal component analysis indicated that dust ingestion, skin exposure, respiration and dietary intake may be the most important sources of TCEP, tris(2-butoxyethyl) phosphate (TBOEP), tri(2-chloroisopropyl) phosphate (TCIPP) and TEHP, respectively, and dust ingestion and skin exposure may be the main sources of TPhP for humans.

Occurrence, source apportionment, and ecological risk assessment of organophosphate esters in surface sediment from the Ogun and Osun Rivers, Southwest Nigeria

Organophosphate esters (OPEs) are synthetic chemicals widely used as e.g., flame retardants and plasticisers in various consumer products. Due to the toxicity of OPEs in aquatic ecosystems, exposure of fauna and flora to these compounds is of potential concern. In this study, the concentrations, profiles, sources, and ecological risk of eight OPEs were investigated in the sediments from the two major rivers in southwest Nigeria. Concentrations of ∑OPEs in surface sediments were in the range 13.1 - 2110 ng/g dry weight (dw) (median: 378 ng/g dw) in the Ogun River and 24.7-589 ng/g dw (median: 174 ng/g dw) in the Osun River. These concentrations are broadly within the range of those reported in surface sediment in previous studies conducted in other locations around the world. Tris (2-butoxyethyl) phosphate (TBOEP) was the dominant OPE in the sediment samples with a median concentration of 337 and 126 ng/g dw for the Ogun and Osun Rivers respectively, while tri-n-butyl phosphate (TnBP) was not detected in any sample. Excluding TBOEP, the chlorinated organophosphate esters: tris(2-chloroethyl) phosphate (TCEP), tris(2-chloro-propyl) phosphate (TCIPP), and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) were the dominant OPEs in the Osun River, while the aryl-OPEs: triphenyl phosphate (TPHP), 2-ethylhexyl diphenyl phosphate (EHDPP), and tri-m-tolyl phosphate (TMTP) were dominant in the Ogun River. Under a median exposure scenario, moderate ecological risk was predicted from exposure to TCIPP in the Osun River. In contrast, under a high exposure scenario, concentrations of TDCIPP (risk quotient, RQ = 5.33-5.37) constituted a high ecological risk in both rivers, with moderate risks observed for TBOEP (RQ = 0.022-0.18) and TCIPP (RQ = 0.097 - 0.16). Therefore, the risk to aquatic organisms from concomitant exposure to mixtures of OPEs in freshwater ecosystems requires further investigation.

Toxicological Mechanisms and Potencies of Organophosphate Esters in KGN Human Ovarian Granulosa Cells as Revealed by High-throughput Transcriptomics

Despite the growing number of studies reporting potential risks associated with exposure to organophosphate esters (OPEs), their molecular mechanisms of action remain poorly defined. We used the high-throughput TempO-Seq™ platform to investigate the effects of frequently detected OPEs on the expression of ∼3000 environmentally responsive genes in KGN human ovarian granulosa cells. Cells were exposed for 48 h to one of five OPEs (0.1 to 50 μM): tris(methylphenyl) phosphate (TMPP), isopropylated triphenyl phosphate (IPPP), tert-butylphenyl diphenyl phosphate (BPDP), triphenyl phosphate (TPHP), or tris(2-butoxyethyl) phosphate (TBOEP). The sequencing data indicate that four OPEs induced transcriptional changes, whereas TBOEP had no effect within the concentration range tested. Multiple pathway databases were used to predict alterations in biological processes based on differentially expressed genes. At lower concentrations, inhibition of the cholesterol biosynthetic pathway was the predominant effect of OPEs; this was likely a consequence of intracellular cholesterol accumulation. At higher concentrations, BPDP and TPHP had distinct effects, primarily affecting pathways involved in cell cycle progression and other stress responses. Benchmark concentration (BMC) modelling revealed that BPDP had the lowest transcriptomic point of departure. However, in vitro to in vivo extrapolation modeling indicated that TMPP was bioactive at lower concentrations than the other OPEs. We conclude that these new approach methodologies provide information on the mechanism(s) underlying the effects of data-poor compounds and assist in the derivation of protective points of departure for use in chemical read-across and decision-making.

Review on typical organophosphate diesters (di-OPEs) requiring priority attention: Formation, occurrence, toxicological, and epidemiological studies

The impact of primary metabolites of organophosphate triesters (tri-OPEs), namely, organophosphate diesters (di-OPEs), on the ecology, environment, and humans cannot be ignored. While extensive studies have been conducted on tri-OPEs, research on the environmental occurrence, toxicity, and health risks of di-OPEs is still in the preliminary stage. Understanding the current research status of di-OPEs is crucial for directing future investigations on the production, distribution, and risks associated with environmental organophosphate esters (OPEs). This paper specifically reviews the metabolization process from tri-OPEs to di-OPEs and the occurrence of di-OPEs in environmental media and organisms, proposes typical di-OPEs in different media, and classifies their toxicological and epidemiological findings. Through a comprehensive analysis, six di-OPEs were identified as typical di-OPEs that require prioritized research. These include di-n-butyl phosphate (DNBP), bis(2-butoxyethyl) phosphate (BBOEP), bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), bis(2-chloroethyl) phosphate (BCEP), bis(1-chloro-2-propyl) phosphate (BCIPP), and diphenyl phosphate (DPHP). This review provides new insights for subsequent toxicological studies on these typical di-OPEs, aiming to improve our understanding of their current status and provide guidance and ideas for research on the toxicity and health risks of di-OPEs. Ultimately, this review aims to enhance the risk warning system of environmental OPEs.

Exposure to dust organophosphate and replacement brominated flame retardants during infancy and risk of subsequent adverse respiratory outcomes

BACKGROUND

Children are highly exposed to flame retardants in indoor environments, partly through inhalation. However, the associations of early life exposure to novel organophosphate (OPFRs) and replacement brominated flame retardants (RBFRs) with adverse respiratory outcomes during childhood are unclear.

METHODS

We used a prospective birth cohort of 234 children recruited from the greater Cincinnati, Ohio metropolitan area between 2003 and 2006. OPFRs and RBFRs were analyzed in dust sampled from the homes' main activity room and the children's bedroom floor at child age 1 year. Caregivers reported subsequent respiratory symptoms every six months until child age 5 years and we measured forced expiratory volume in 1 s as well as peak expiratory flow (PEF) at child age 5 years. We performed generalized estimating equations and linear regression modeling adjusted for covariates to examine the exposure-outcome associations.

RESULTS

Geometric means (GMs) (standard error [SE]) for dust concentrations were 10.27 (0.63) μg/g for total OPFRs (ΣOPFRs) and 0.48 (0.04) μg/g for total RBFRs (ΣRBFRs); GMs (SE) for dust loadings were 2.82 (0.26) μg/m2 for ΣOPFRs and 0.13 (0.01) μg/m2 for ΣRBFRs. Dust ∑OPFRs concentrations at age 1 year were associated with higher subsequent risks of wheezing (relative risk [RR]: 1.68, 95% confidence interval [CI]: 1.20-2.34), respiratory infections (RR: 4.01, 95% CI: 1.95-8.24), and hay fever/allergies (RR: 1.33, 95% CI: 1.10-1.60), whereas ∑OPFRs dust loadings at age 1 year were associated with higher risks of subsequent respiratory infections (RR: 1.87, 95% CI: 1.05-3.34) and hay fever/allergies (RR: 1.34, 95% CI: 1.19-1.51). PEF (mL/min) was lower with higher ∑OPFRs dust loadings (β: -12.10, 95% CI: -21.10, -3.10) and with the RBFR bis(2-ethylhexyl) tetrabromophthalate (β: -9.05, 95% CI: -17.67, -0.43).

CONCLUSIONS

Exposure to OPFRs and RBFRs during infancy may be a risk factor for adverse respiratory outcomes during childhood.

Urinary concentrations of organophosphate esters and associated health outcomes in Korean firefighters

Although firefighters are at an increased risk of occupational exposure to chemicals, such as flame retardants, research on the exposure of Korean firefighters to organophosphate esters (OPEs)-a group of emerging flame retardants-remains limited. Therefore, in the present study, OPE metabolite concentrations in the urine samples of 149 former and current Korean firefighters were measured. Based on the data obtained, the estimated daily intakes (EDIs) of OPEs were calculated. Subsequently, the association between the urinary concentrations of OPE metabolites and the potential determinants of OPE exposure and health outcomes (e.g., obesity and serum lipids) was investigated. We found that bis(1-chloro-2-propyl) phosphate (BCIPP) and bis(2-chloroethyl) phosphate (BCEP) were the most prevalent urinary OPE metabolites, with median concentrations of 2.33 and 1.80 ng/mL, respectively; these concentrations were higher than those reported previously in other countries, such as the USA and China. Moreover, their parent compounds-tris(1-chloro-2-propyl) phosphate (TCIPP) and tris(2-chloroethyl) phosphate (TCEP)-exhibited EDIs of 126 and 94.8 ng/kg bw/day, respectively. Unlike the high detection rate of bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) in other populations, its detection rate in this study was low (6.7%), suggesting regional differences in the exposure pattern of OPEs among countries. Furthermore, occupational characteristics, such as recent participation in firefighting activity, were identified as determinants of the urinary concentrations of OPE metabolites. Total OPE metabolites were inversely associated with body mass index and positively associated with high-density lipoprotein cholesterol. Overall, our findings demonstrate that Korean firefighters are highly exposed to several occupation-related OPEs. Further prospective studies will help elucidate the potential health implications of occupational exposure to OPEs among firefighters.

Nontarget Identification of Novel Organophosphorus Flame Retardants and Plasticizers in Rainfall Runoffs and Agricultural Soils around a Plastic Recycling Industrial Park

Plastic recycling and reprocessing activities may release organophosphate ester (OPE) flame retardants and plasticizers into the surrounding environment. However, the relevant contamination profiles and impacts remain not well studied. This study investigated the occurrence of 28 OPEs and their metabolites (mOPEs) in rainfall runoffs and agricultural soils around one of the largest plastic recycling industrial parks in North China and identified novel organophosphorus compounds (NOPs) using high-resolution mass spectrometry-based nontarget analysis. Twenty and twenty-seven OPEs were detected in runoff water and soil samples, with total concentrations of 86.0-2491 ng/L and 2.53-199 ng/g dw, respectively. Thirteen NOPs were identified, of which eight were reported in the environment for the first time, including a chlorine-containing OPE, an organophosphorus heterocycle, a phosphite, three novel OPE metabolites, and two oligomers. Triphenylphosphine oxide and diphenylphosphinic acid occurred ubiquitously in runoffs and soils, with concentrations up to 390 ng/L and 40.2 ng/g dw, respectively. The downwind areas of the industrial park showed elevated levels of OPEs and NOPs. The contribution of hydroxylated mOPEs was higher in soils than in runoffs. These findings suggest that plastic recycling and reprocessing activities are significant sources of OPEs and NOPs and that biotransformation may further increase the ecological and human exposure risk.

Handwipes as indicators to assess organophosphate flame retardants exposure and thyroid hormone effects in e-waste dismantlers

Dermal exposure is increasingly recognized as an important pathway for organic pollutant exposure. However, data on dermal exposure are limited, particularly with respect to the health effects. This study evaluated association between organophosphorus flame retardants (OPFRs) in handwipes and internal body burden on workers and adult residents in an electronic waste (e-waste) dismantling area. The impact of dermal exposure to OPFRs on thyroid hormones (THs) served as a biomarker for early effects. Triphenyl phosphate (TPhP) was the most detected compound in handwipes, with median levels of 1180, 200, and 24.0 ng in people identified as e-waste bakers, e-waste dismantlers, and adult residents. Among e-waste dismantlers, TPhP levels in handwipes were positively correlated with paired serum TPhP and urinary diphenyl phosphate (DPhP) levels. In multiple linear regression models controlling for sex, age and smoking, TPhP levels in handwipes of e-waste dismantlers were significantly negatively correlated with three THs used to evaluate thyroid function: serum reverse 3,3',5-triiodo-L-thyronine (rT3), 3,3'-diiodo-L-thyronine (3,3'-T2), and 3,5-diiodo-L-thyronine (3,5-T2). These findings suggest that handwipes can act as non-invasive exposure indicators to assess body burden of dermal exposure to TPhP and health effects on THs of e-waste dismantlers. This study highlights importance of OPFR effect on human THs through dermal exposure.

Elevated levels of biomarkers of oxidative stress and renal injury linked to nitrogenous flame retardants exposure in e-waste dismantling site: A case study in China

Nitrogenous flame retardants (NFRs) have aroused worldwide public concern as their nephrotoxic effect. However, knowledge regarding the pathogenesis mechanism of their exposure to induce kidney injury remains largely unknown. In this study, eight NFRs, four oxidative stress biomarkers (OSBs), and one kidney injury biomarker, namely neutrophil gelatinase-associated lipocalin (NGAL), were measured in urine specimens collected from residents living around e-waste disassembly and reference areas, representing two exposure scenarios. Significant higher concentrations of Σ₈NFR (median: 70.6 vs. 33.8 μg/g Cre) and five biomarkers (124 vs. 97.4 μg/g Cre) were found in urines of populations living in e-waste site compared to those in the reference site (p < 0.05). Primary NFRs exhibited significant positive associations with OSBs and NGAL regardless of the population examined, implying that chronic NFRs exposure could induce oxidative stress and kidney damage. By using structure equation model, we found that oxidative stress, particularly DNA and RNA oxidation mediated 16.1% of the total effect of NFRs on NGAL in e-waste related people, but not on the general population. Overall, this study suggests long-term chronic exposure to NFRs can induce oxidative stress and renal injury in humans but the pathogenesis mode may be scenario-specific.

Occurrence, distribution, and ecological risk of organophosphorus flame retardants and their degradation products in water and upper sediment of two urban rivers in Shenzhen, China

Organophosphorus flame retardants (OPFRs) are widely used in various industrial manufacturing processes; thus, their environmental impact in agglomerated industrial areas is of great concern. In this study, seventeen kinds of OPFRs and five kinds of organophosphate diesters (Di-OPs) in water and upper sediment samples from two urban rivers in the agglomerated industrial area of Shenzhen city, China, were investigated. The results showed that the total concentrations of detectable OPFRs ranged from 3438.83 to 12,838.87 ng/L with an average of 6494.94 ng/L in water samples and from 47.16 to 524.46 ng/g (dry weight, dw) with an average of 181.48 ng/g dw in sediment. The values were higher than those in other rivers worldwide. Tris(2-chloroethyl) phosphate (TCEP) is the predominant OPFRs in water and upper sediment, up to 10,664.23 ng/L in water and 414.12 ng/g dw in sediment. The total concentration of OPFRs of sediment samples in the Maozhou River was around twice as high as in the Guanlan River. The results indicated that the level of OPFRs was associated with the industrial activity intensity. Di-OPs exhibited lower concentrations than their parent compounds, and can be attributed to the degradation/metabolism of their parent compounds in the river. The sediment-water partition of OPFRs is significantly correlated with their log Kow values. Risk assessment revealed moderate ecological risks posed by OPFRs in water to aquatic organisms. The present study revealed the pollution status of OPFRs in rivers from agglomerated industrial and residential areas.

Smart technologies for collection and classification of electronic waste

Purpose

The main aim of this study is to understand the role of smart technologies and show the rankings of various smart technologies in collection and classification of electronic waste (e-waste).

Design/methodology/approach

This study presents a framework integrating the concepts of collection and classification mechanisms and smart technologies. The criteria set includes three main, which are economic, social and environmental criteria, including a total of 15 subcriteria. Smart technologies identified in this study were robotics, multiagent systems, autonomous tools, smart vehicles, data-driven technologies, Internet of things (IOT), cloud computing and big data analytics. The weights of all criteria were found using fuzzy analytic network process (ANP), and the scores of smart technologies which were useful for collection and classification of e-waste were calculated using fuzzy VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR).

Findings

The most important criterion was found as collection cost, followed by pollution prevention and control, storage/holding cost and greenhouse gas emissions in collection and classification of e-waste. Autonomous tools were found as the best smart technology for collection and classification of e-waste, followed by robotics and smart vehicles.

Originality/value

The originality of the study is to propose a framework, which integrates the collection and classification of e-waste and smart technologies.

Organophosphate ester exposure among Chinese waste incinerator workers: Urinary levels, risk assessment and associations with oxidative stress

Organophosphate esters (OPEs), which are frequently used as flame retardants and plasticizers in versatile products, are readily released to the external environment. Although workers at municipal waste incineration plants may be extensively exposed to OPEs, only scarce health monitoring and risk assessments have been conducted in this population. In this study, we investigated the levels of eight metabolites of organophosphate esters (mOPEs) and the oxidative stress marker 8-hydroxy-2-deoxyguanosine (8-OHdG) in urine samples from 73 waste incinerator workers and 97 general residents from Shenzhen, China between September 2016 and June 2017. The overall detection rate of mOPEs was 82.2 %-100 %, and higher concentrations of di-p-cresyl phosphate and chlorinated mOPEs [bis(2-chloroethyl) phosphate (BCEP), bis(1-chloro-2propyl) phosphate (BCIPP), bis(1,3-dichloro-2-propyl) phosphate) (BDCIPP)] were found among incinerator workers than among general residents. The incinerator workers also showed significantly higher levels of 8-OHdG than general residents, but the measured levels of most mOPEs were not significantly correlated with the level of 8-OHdG; this may be because co-exposure to multiple toxic compounds can lead to oxidative stress. Risk assessment using Monte Carlo simulations revealed that 95 % of the incinerator workers were free from non-carcinogenic effects due to OPEs exposure (hazard index = 0.27, 95 % CI: 0.09, 0.77). However, the carcinogenic risk of tris(2-chloroethyl) phosphate (TCEP) for incinerator workers was between 10-6 and 10-4. These results indicate that incinerator workers are extensively exposed to OPEs, and better protective measures need to be implemented.

Association between organophosphorus flame retardants exposure and cognitive impairment among elderly population in southern China

The wide application of organophosphorus flame retardants (OPFRs) in consumer products leads to their ubiquitous occurrence. The neurotoxicity of OPFRs has been raised, whereas evidence from the elderly population were rather scarce. Hence, a case-control study was conducted based on the Shenzhen Aging-related Disorder Cohort. A total of 184 cases [Mini-mental State Examination (MMSE) < 24] and 795 participants as controls (MMSE ≥24) were recruited. Eight metabolites of OPFRs (m-OPFRs) in urine samples were measured, including bis(2-butoxyethyl) phosphate (BBOEP), bis(2-chloroethyl) phosphate (BCEP), bis(1-chloro-2-propyl) phosphate (BCIPP), bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), dibutyl phosphate (DBP), di-o-cresyl phosphate (DOCP), di-p-cresyl phosphate (DPCP) and diphenyl phosphate (DPHP). The detection frequencies of m-OPFRs ranged from 88.8 % to 95.4 %. BCEP had the highest median concentration (0.93 μg/L), followed by BCIPP (0.32 μg/L), DPHP (0.27 μg/L) and DBP (0.20 μg/L). Significant correlations were found between all pairs of urinary m-OPFRs with correlation coefficients ranging from 0.22 to 0.71 (p< 0.05). Logistic regression models showed that urinary concentrations of BDCIPP (adjusted odds ratio [OR]: 1.25, 95 % confidential interval [CI]: 1.04-1.50) and DBP (adjusted OR: 1.10, 95 % CI: 1.01-1.20) were positively associated with lower cognitive functions. Furthermore, a nonlinear dose-response relationship was found between urinary BDCIPP concentration and cognitive decline. To our knowledge, this is the first report on OPFR exposure and cognitive impairment among elderly population. Further toxicological tests of BDCIPP and DBP are needed to illustrate these results.

A sequential leaching procedure for efficient recovery of gold and silver from waste mobile phone printed circuit boards

The present study reports a sequential, non-acid process for effective recovery of copper and precious metals from mobile phone printed circuit boards. In this process, gold and silver were first enriched during the synthesis process of cuprous chloride and then leached by thiosulfate method. Results indicated that the distribution of gold and silver in the liquid and solid phases during the synthesis of cuprous chloride process was affected by the [Cu]/[Cu²⁺] ratio. Enrichment of gold and silver in the residue after the cuprous chloride synthesis could be achieved by the adjusting the [Cu]/[Cu²⁺] ratio. The silver and gold leaching rates of the residue after cuprous chloride synthesis (93.8 % silver and 99 % gold) were much higher than those of the raw PCB sample (27.0 % silver and 14.2 % gold) under the same conditions. This process has the advantages of high leaching efficiency, high leaching rate and avoiding the use of HNO₃ or aqua regia commonly used for copper, gold and silver recovery. Thus, this study offers a promising and environmentally friendly method for recovering valuable metals from e-waste.

Spatial distribution and risk assessment of 11 organophosphate flame retardants in soils from different regions of agricultural farmlands in mainland China

The occurrence and distribution of organophosphate flame retardants (OPFRs) in nationwide farmland soils of mainland China are rarely measured. The current study was the first to collect 325 farmland soil samples from 109 cities throughout mainland China. Ten organophosphate esters (OPEs), including alkyl-OPEs, Cl-OPEs, and aryl-OPEs, together with an organophosphate intermediates (TPPO), were determined. The results indicated that ΣOPFRs ranged from 2.41 ng/g to 35.8 ng/g dry weight (dw), and ΣOPFRs in northeastern and southern China were significantly (p < 0.01) higher than those in northwestern and central China. Alkyl-OPEs and Cl-OPEs served as the main components of OPEs, and the novel aryl-OPEs showed the highest detection frequency (> 92 %). Principal component analysis (PCA) was employed to identify the different sources of OPEs, in which atmospheric deposition, irrigation, or direct release of plastic mulch acted as the main input routes in farmland soils. The potential risks of OPFRs were assessed through soil ingestion exposure and ecotoxicological impacts. Our results showed that direct exposure to farmland soils had no high risks to the human body and ecological environments. This study provides new evidence for further understanding the spatial distributions and contamination status of OPFRs in farmland soils throughout mainland China.

E-WASTE threatens health: The scientific solution adopts the one health strategy

The aggressively extractive advanced technology industry thrives on intensive use of non-renewable resources and hyper-consumeristic culture. The environmental impact of its exponential growth means extreme mining, hazardous labour practices including child labour, and exposure burden to inorganic and organic hazardous chemicals for the environment and current and future human generations. Globally, processes such as in-country reduce, reuse and recycle have so far received less attention than outer-circle strategies like the uncontrolled dumping of e-waste in countries that are unprotected by regulatory frameworks. Here, in the absence of infrastructures for sound hazardous e-waste management, the crude recycling, open burning and dumping into landfills of e-waste severely expose people, animal and the environment. Along with economic, political, social, and cultural solutions to the e-waste global problem, the scientific approach based on risk analysis encompassing risk assessment, risk management and risk communication can foster a technical support to resist transgenerational e-waste exposure and health inequalities. This paper presents the latest public health strategies based on the use of integrated human and animal biomonitoring and appropriate biomarkers to assess and manage the risk of e-waste embracing the One Health approach. Advantages and challenges of integrated biomonitoring are described, along with ad-hoc biomarkers of exposure, effect and susceptibility with special focus on metals and metalloids. Indeed, the safe and sustainable management of novel technologies will benefit of the integration and coordination of human and animal biomonitoring.

PFAS use in electronic products and exposure risks during handling and processing of e-waste: A review

Poly- and perfluorinated alkyl substances (PFAS) have been and are used in electronic products due to their unique properties that improve product quality and performance. Ubiquities and persistence of some PFAS detected in environmental samples (water, soil, air) have attracted much attention and regulatory actions in recent years. This review provides an overview of PFAS use in electronic components; trends in quantities of e-waste generation; PFAS exposure pathways during e-waste handling and processing; reported PFAS in environmental samples and samples of serum, blood, and hair collected from people living near and working at e-waste processing sites. Processes used for manufacturing electronic components (e.g., embedded processes, additive manufacturing) make recycling or materials recovery from discarded electronic units and components very difficult and unfeasible. Exposure during numerous processing steps for materials recovery and scavenging at disposal sites can result in PFAS intake through inhalation, ingestion, and dermal routes. Chemical risk assessment approaches have been continuously evolving to consider chemical-specific dosimetric and mechanistic information. While the metabolic fate of PFAS is not well understood, some PFAS bioaccumulate and bind to proteins (but not to lipids) in biota and humans due to their surface-active characteristics and very low solubility in water and fat. It is difficult to associate the adverse health effects due to exposure to e-waste directly to PFAS as there are other factors that could contribute to the observed adverse effects. However, PFAS have been detected in the samples collected from different environmental compartments (e.g., water, soil, leachate, blood sera, rainwater) at and near e-waste processing sites, landfills, and near electronics and optoelectronics industries indicating that e-waste collection, processing, and disposal sites are potential PFAS exposure locations. Better monitoring of e-waste handling sites and detailed epidemiological studies for at risk populations are needed for assessing potential health risks due to PFAS exposure at these sites.

Occupational exposure to organophosphate esters in e-waste dismantling workers: Risk assessment and influencing factors screening

Organophosphate esters (OPEs) are increasingly added in electronic products as alternative flame retardants, which may result in high occupational exposure of electronic waste recycling employees. This study investigated occupational exposure to OPEs in an e-waste recycling site in northern China, with intent to explore the impacts of occupational exposure and dismantling manipulation mode. Human urine samples from three sites with different distances from the core dismantling area, including employees from family workshops and plants with centralized management and residents from nearby areas, were collected and analyzed for OPEs' metabolites (mOPEs). The urinary ∑mOPEs' median concentrations (0.910 ng/mL) of all employees were significantly higher than those of residents in Ziya Town (0.526 ng/mL) and Jinghai downtown (0.600 ng/mL), suggesting the risk of occupational OPEs' exposure associated with e-waste dismantling. However, the spatial variation was insignificant for residents with different distances from the e-waste recycling site. Besides, OPEs' exposure levels were significantly affected by manipulation modes and the urinary ∑mOPEs' median concentrations in the employees of family workshops (1.05 ng/mL) were significantly higher than those in plants with centralized management (0.667 ng/mL). The result suggests that mechanical dismantling and active ventilating measures can reduce the OPEs' occupational exposure risk. Moreover, ∑mOPEs were higher in volunteers with age above 50 years old and in the underweight subgroup. Finally, different categories of mOPEs in human urine showed associations with corresponding OPEs in dust samples in the same area.

OPFRs in e-waste sites: Integrating in silico approaches, selective bioremediation, and health risk management of residents surrounding

A multilevel index system of organophosphate flame retardant bioremediation effect in an e-waste handling area was established under three bioremediation scenarios (scenario I, plant absorption; scenario II, plant-microbial combined remediation; scenario III, microbial degradation). Directional modification of OPFR substitutes with high selective bioremediation was performed. The virtual amino acid mutation approach was utilised to generate high-efficiency selective absorption/degradation mutant proteins (MPs) in a plant-microbial system under varying conditions. In scenario III, the MP's microbial degrading ability to replace molecules was increased to the greatest degree (165.82%). Appropriate foods such as corn, pig liver, and yam should be consumed, whereas the simultaneous consumption of high protein foods such as pig liver and walnut should be avoided; sweet potato and yam are believed to be prevent OPFRs and substitute molecules from entering the human body through multiple pathways for reduced genotoxicity of OPFRs in the populations of e-waste handling areas (the reduction degree can reach 85.12%). The study provides a theoretical basis for the development of ecologically acceptable OPFR substitutes and innovative high-efficiency bioremediation MPs, as well as for the reduction of the joint toxicity risk of multiple ingestion route exposure/gene damage of OPFRs in high OPFR exposure sites.

Exposure of e-waste dismantlers from a formal recycling facility in Spain to inhalable organophosphate and halogenated flame retardants

Concentration levels of 16 organophosphate esters (OPEs) and 18 halogenated flame retardants (HFRs) were measured in airborne fine particulate matter (PM_2.5) from an e-waste dismantling facility in Catalonia (Spain) to assess their occurrence, profiles and potential health risks. Three different areas from the facility were studied, including an area for cathodic ray-tube (CRT) TV dismantling, a grinding area, and the outdoor background. OPEs and HFRs were detected in all samples, with concentrations between 10.4 and 110 ng/m³ for OPEs and from 0.72 to 2213 ng/m³ for HFRs. The compounds with highest concentrations in both working areas were triphenyl phosphate (TPHP) and tris(2-chloroisopropyl) phosphate (TCIPP) for OPEs and decabromodiphenyl ether (BDE-209) for HFRs. Higher concentration levels were found in the CRT area compared to the grinding one, probably due to the lower ventilation and different types of e-waste being processed. OPEs were also detected in the solid e-waste from the facility, highlighting the need to evaluate pollutant levels in e-waste before proceeding to its re-use. Estimated daily intakes via inhalation during workday were calculated, as well as carcinogenic and non-carcinogenic health risks, these being 25 and 50 times lower than threshold risk values in the worst cases, respectively. However, this calculated risk only considers the workday exposure via inhalation, while other routes of exposure (e.g., ingestion, dermal) could bring these values closer to threshold values.

Pollution profiles and human health risk assessment of atmospheric organophosphorus esters in an e-waste dismantling park and its surrounding area

Recycling e-waste has been recognized as an important emission source of organophosphate triesters (tri-OPEs) and organophosphate diesters (di-OPEs), but the presence of di-OPEs in atmosphere has not been studied. Herein, tri-OPEs and di-OPEs in atmosphere of an e-waste dismantling park and surrounding area in South China were monitored for three consecutive years. Thirteen tri-OPEs and seven di-OPEs were identified. In 2017, 2018, and 2019, tri-OPE concentrations in e-waste dismantling park were 1.30 × 10⁸, 4.60 × 10⁶, and 4.01 × 10⁷ pg/m³, while di-OPE concentrations were 1.14 × 10³, 1.10 × 10³, and 0.35 × 10³ pg/m³, respectively, which were much higher than the surrounding area. Tri-OPEs and di-OPEs generated during e-waste dismantling affected surrounding area through diffusion. Triphenyl phosphate (TPhP) and diphenyl phosphate (DPhP) were the predominant congeners of tri-OPEs and di-OPEs, respectively. Additionally, TPhP concentration was extremely higher than other tri-OPEs, so TPhP could be used as an indicator of e-waste dismantling. Spearman correlation analysis showed significant correlations between DPhP and TPhP (R² = 0.53, p < 0.01), bis-(1-chloro-2-propyl) phosphate (BCIPP) and tris(2-chloropropyl) phosphate (TCIPP) (R² = 0.49, p < 0.01), as well as dibutyl phosphate (DBP) and tributyl phosphate (TBP) (R² = 0.53, p < 0.01), indicating that they had the same source. Further, non-carcinogenic risk of them to people via inhalation was acceptable and non-carcinogenic risk of tri-OPEs decreased year by year in surrounding area.

Occurrence of novel organophosphate esters derived from organophosphite antioxidants in an e-waste dismantling area: Associations between hand wipes and dust

Electronic waste (e-waste) is a well-known source of plastic additives in the environment. However, the e-waste-related occupational exposure to organophosphite antioxidants (OPAs) and the relevant oxidation products-novel organophosphate esters (NOPEs)-via different pathways is still unknown. In this study, six OPAs and three NOPEs were measured in 116 dust and 43 hand-wipe samples from an e-waste dismantling area in Central China. The median concentrations of ΣOPAs and ΣNOPEs were 188 and 13,900 ng·g^-1 in workshop dust and 5,250 ng·m^-2 and 53,600 ng·m^-2 on workers' hands, respectively. The increasing concentrations of dust in the form of triphenyl phosphate (TPHP) (p < 0.01) and tris(2,4-di-tert-butylphenyl) phosphate (AO168 = O) (p < 0.05) were strongly associated with the corresponding concentration on workers' hands. Furthermore, men had significantly lower levels of NOPEs on their hands than did women (p < 0.01). Moreover, the hand wipe levels of AO168 = O (41,600 ng·m^-2) was significantly higher than that of the typical OPE (TPHP, 7370 ng·m^-2), and the hand-to-mouth contact (ΣOPAs, 9.48 ng·kg bw^-1·day^-1; ΣNOPEs, 109 ng·kg bw^-1·day^-1) was a more significant and integrated pathway than dust ingestion (ΣOPAs, 0.10 ng·kg bw^-1·day^-1; ΣNOPEs, 5.01 ng·kg bw^-1·day^-1) of e-waste related occupational exposure to these "new" chemicals.

Health consequences of exposure to e-waste: an updated systematic review

Electronic waste (e-waste) contains numerous chemicals harmful to human and ecological health. To update a 2013 review assessing adverse human health consequences of exposure to e-waste, we systematically reviewed studies reporting effects on humans related to e-waste exposure. We searched EMBASE, PsycNET, Web of Science, CINAHL, and PubMed for articles published between Dec 18, 2012, and Jan 28, 2020, restricting our search to publications in English. Of the 5645 records identified, we included 70 studies that met the preset criteria. People living in e-waste exposed regions had significantly elevated levels of heavy metals and persistent organic pollutants. Children and pregnant women were especially susceptible during the critical periods of exposure that detrimentally affect diverse biological systems and organs. Elevated toxic chemicals negatively impact on neonatal growth indices and hormone level alterations in e-waste exposed populations. We recorded possible connections between chronic exposure to e-waste and DNA lesions, telomere attrition, inhibited vaccine responsiveness, elevated oxidative stress, and altered immune function. The existence of various toxic chemicals in e-waste recycling areas impose plausible adverse health outcomes. Novel cost-effective methods for safe recycling operations need to be employed in e-waste sites to ensure the health and safety of vulnerable populations.

Exposure to organophosphate esters in elderly people: Relationships of OPE body burdens with indoor air and dust concentrations and food consumption

Human exposure to OPEs is pervasive and should be of great concern due to associations with adverse health effects, especially in susceptible populations. In this study, body burdens and exposure pathways of OPEs were investigated for 76 healthy elderly people in Jinan, China based on the measured OPE and metabolite concentrations in human bio-samples (whole blood and urine) and paired environmental matrices (air and dust), as well as food frequency questionnaire. Eight of 16 OPEs and 5 of 11 metabolites were detected in > 50% of whole blood and urine samples, respectively. Tri(1-chloro-2-propyl) phosphate (TCIPP), tris(2-chloroethyl) phosphate (TCEP), tri-phenyl phosphate (TPHP), and 2-ethylhexyl di-phenyl phosphate (EHDPP) were frequently detected and abundant in whole blood, while their corresponding metabolites were detected at low frequencies or levels in urine. The reduced metabolic and/or excretory capacity of elderly people may be an important reason, implying a higher health risk to them. Fourteen OPEs had over 50% detection frequencies in indoor air and dust, while 6 di-esters in indoor dust. Tris(2-ethylhexyl) phosphate (TEHP) in indoor dust and tri-n-butyl phosphate (TnBP) in indoor air were positively correlated with paired levels in blood but not with their metabolites (BEHP and DnBP) in urine. Combined with the direct intakes of BEHP and DBP from dust, blood is indicated as more suitable biomarker for TEHP and TnBP exposure. High consumption frequencies of several foods were associated with higher blood concentrations of three OPEs and urinary levels of four di-OPEs, indicating the importance of dietary exposure pathway. Estimated daily total intakes of OPEs via inhalation, dust ingestion, and dermal absorption ranged from 2.78 to 42.0 ng/kg bw/day, which were far less than the reference dosage values. Further studies were warranted to explore the potential health effects of OPE exposure in the elderly populations.

Organophosphate flame retardants, tetrabromobisphenol A, and their transformation products in sediment of e-waste dismantling areas and the flame-retardant production base

Due to the prohibition of polybrominated diphenyl ethers, organophosphate flame retardants (OPFRs) and tetrabromobisphenol A (TBBPA) have become emerging flame retardants. However, knowledge about their occurrence, especially their transformation products, is still limited. This study collected sediment samples from two rivers, i.e., Lianjiang River (located at an e-waste dismantling area) and Xiaoqing River (situated at a flame retardant production base), to investigate the occurrence, composition, and spatiality distribution of OPFRs, TBBPA, and their transformation products. Both targets were detected in the Lianjiang River in the range of 220-1.4 × 10⁴ and 108-3.1 × 10³ ng/g dw (dry weight) for OPFRs and TBBPA, and 0.11-2.35 and 4.8-414 ng/g dw for their respective transformation products, respectively. The concentrations of OPFRs and TBBPA in the Xiaoqing River ranged from 4.15 to 31.5 and 0.76-2.51 ng/g dw, respectively, and no transformation products were detected. Different compositional characteristics of OPFRs and distinct spatial distribution from mainstream and tributary observed between the two rivers are attributed to the difference in the local industries. Spatial distribution and principal component analysis indicated that e-waste dismantling activities could be a vital source of local pollution. Besides, the confluence of tributaries seemed to determine the contaminant levels in the Xiaoqing River. Also, concentration ratios and Spearman's correlation between metabolites and parent chemicals were analyzed. Low concentration ratios (3.6 ×10^-4 to 0.16) indicated a low transformation degree, and Spearman's correlation analysis suggested transformation products were partly stemming from commercial products. Considering the limited study of these transformation products, more studies on their sources, transform mechanism, and toxicity are required.

An adverse outcome pathway based in vitro characterization of novel flame retardants-induced hepatic steatosis

A wide range of novel replacement flame retardants (nFRs) is consistently detected in increasing concentrations in the environment and human matrices. Evidence suggests that nFRs exposure may be associated with disruption of the endocrine system, which has been linked with the etiology of various metabolic disorders, including nonalcoholic fatty liver disease (NAFLD). NAFLD is a multifactorial disease characterized by the uncontrolled accumulation of fats (lipids) in the hepatocytes and involves multiple-hit pathogenesis, including exposure to occupational and environmental chemicals such as organophosphate flame retardants (OPFRs). In the present study we aimed to investigate the potential mechanisms of the nFRs-induced hepatic steatosis in the human liver cells. In this study, we employed an in vitro bioassay toolbox to assess the key events (KEs) in the proposed adverse outcome pathways (AOP) (s) for hepatic steatosis. We examined nine nFRs using AOP- based in vitro assays measuring KEs such as lipid accumulation, mitochondrial dysfunction, gene expression, and in silico approach to identify the putative molecular initiating events (MIEs). Our findings suggest that several tested OPFRs induced lipid accumulation in human liver cell culture. Tricresyl phosphate (TMPP), triphenyl phosphate (TPHP), tris(1,3-dichloropropyl) phosphate (TDCIPP), and 2-ethylhexyl diphenyl phosphate (EHDPP) induced the highest lipid accumulation by altering the expression of genes encoding hepatic de novo lipogenesis and mitochondrial dysfunction depicted by decreased cellular ATP production. Available in vitro data from ToxCast and in silico molecular docking suggests that pregnane X receptor (PXR) and peroxisome proliferator-activated receptor gamma (PPARγ) could be the molecular targets for the tested nFRs. The study identifies several nFRs, such as TMPP and EHDPP, TPHP, and TDCIPP, as potential risk factor for NAFLD and advances our understanding of the mechanisms involved, demonstrating the utility of an AOP-based strategy for screening and prioritizing chemicals and elucidating the molecular mechanisms of toxicity.

Identifying Dermal Uptake as a Significant Pathway for Human Exposure to Typical Semivolatile Organic Compounds in an E-Waste Dismantling Site: The Relationship of Contaminant Levels in Handwipes and Urine Metabolites

Dermal exposure to semivolatile organic compounds (SVOCs) has recently attracted widespread attention; understanding these exposures is particularly important for people whose skin is frequently exposed to different pollution surfaces. In this study, handwipes were collected from exposed occupational workers and local residents near a typical electronic waste (e-waste) dismantling area; urine samples were also sampled. The wipes were analyzed for three typical SVOCs: polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs), and organophosphate flame retardants (OPFRs). The median levels of PAHs, OPFRs, and PBDEs in handwipes from e-waste dismantlers were 96.0, 183, and 238 ng, respectively. The analytes were higher in the handwipes collected from workers than those from residents, indicating that they were subjected to greater dermal exposure during primitive e-waste dismantling activities. Among the three SVOCs, the strongest correlation was found between triphenyl phosphate (TPhP) in handwipes and diphenyl phosphate (DPhP) in paired urine; the next strongest correlations were between PAHs and PBDEs and their corresponding urinary metabolites. The results showed that TPhP contributed the highest exposure to e-waste dismantlers via dermal exposure. Our research highlights the importance of dermal exposure to TPhP, which should be considered in future exposure risk assessments.

Organophosphorus flame retardants (OPFRs) in the seawater and sediments of the Qinzhou Bay, Northern Beibu Gulf: Occurrence, distribution, and ecological risks

The occurrence, distributions, and ecological risks of 11 organophosphate flame retardants (OPFRs) were investigated in the seawater and sediment samples from the Qinzhou Bay. The Σ₁₁OPFRs in the surface seawater and sediments ranged from 150 to 885 ng/L and from <the limit of quantification (LOQ) to 32.2 ng/g dw, respectively, with high levels of OPFRs in the industrialized and port areas. Tris (2-chloro-propyl) phosphate (TCIPP), tris (2-chloroethyl) phosphate (TCEP), and tri-n-butyl phosphate (TNBP) were the dominant OPFRs in the surface seawater and sediments. The Σ₁₁OPFRs concentrations in the sediment core ranged 1.2-18.6 ng/g dw and the vertical trends showed a recent increase of OPFRs emissions, especially for TNBP and triphenyl phosphate (TPHP). Risk assessment revealed that individual OPFR could pose low to medium ecological risks, but the risk from the mixture of OPFRs on aquatic organisms requires more attention.

Flame Retardants-Mediated Interferon Signaling in the Pathogenesis of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a growing concern worldwide, affecting 25% of the global population. NAFLD is a multifactorial disease with a broad spectrum of pathology includes steatosis, which gradually progresses to a more severe condition such as nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and eventually leads to hepatic cancer. Several risk factors, including exposure to environmental toxicants, are involved in the development and progression of NAFLD. Environmental factors may promote the development and progression of NAFLD by various biological alterations, including mitochondrial dysfunction, reactive oxygen species production, nuclear receptors dysregulation, and interference in inflammatory and immune-mediated signaling. Moreover, environmental contaminants can influence immune responses by impairing the immune system’s components and, ultimately, disease susceptibility. Flame retardants (FRs) are anthropogenic chemicals or mixtures that are being used to inhibit or delay the spread of fire. FRs have been employed in several household and outdoor products; therefore, human exposure is unavoidable. In this review, we summarized the potential mechanisms of FRs-associated immune and inflammatory signaling and their possible contribution to the development and progression of NAFLD, with an emphasis on FRs-mediated interferon signaling. Knowledge gaps are identified, and emerging pharmacotherapeutic molecules targeting the immune and inflammatory signaling for NAFLD are also discussed.

Profiles of neonicotinoid insecticides and their metabolites in paired saliva and periodontal blood samples in human from South China: Association with oxidative stress markers

Neonicotinoid insecticides (NEOs) are widely used around the world. The distribution of NEOs in paired saliva and periodontal blood samples was not previously documented in China. In this study, the concentrations of six NEOs and three corresponding metabolites were measured in 188 paired saliva and periodontal blood samples collected from South China. NEOs and their metabolites were frequently detected (68-94%) in paired saliva and periodontal blood, with median levels of 0.01-0.99 ng/mL. 1-Methyl-3-(tetrahydro-3-furylmethyl) urea was the most predominant NEO in paired saliva (39%) and periodontal blood (42%). Gender-related differences in NEOs and their metabolite concentrations were found: males showed lower levels than females. We calculated the concentration ratios between saliva and periodontal blood (S/PB ratios), and found that the median S/PB ratios of NEO and their metabolites were higher than 1, indicating that NEOs and their metabolites were easily excreted via saliva. 8-Hydroxy-2'-deoxyguanosine (8-OHdG) was measured in paired saliva and periodontal blood as a marker of oxidative stress. 8-OHdG concentrations in saliva and periodontal blood were significantly and positively correlated (p < 0.05) with the concentrations of most NEOs and their metabolites in saliva and periodontal blood samples. These findings indicated that exposure to NEOs and their metabolites is associated with oxidative stress. This study is the first to report NEOs and their metabolites in paired saliva and periodontal blood samples collected from South China.

Organophosphate flame retardants and diesters in the urine of e-waste dismantling workers: associations with indoor dust and implications for urinary biomonitoring

Indoor dust ingestion is one of the main pathways for human exposure to organophosphate flame retardants (PFRs). The urinary concentrations of diesters (DAPs) are usually used as biomarkers to assess human exposure to PFRs. In this study, the PFR and DAP levels were measured in morning and evening urine samples of 30 workers from an e-waste dismantling site in southern China. The indoor dust samples were also collected from workshops and houses for analyzing associations between PFR and DAP levels in urine and dust. Tris(1-chloro-2-propyl) phosphate (TCIPP) and triphenyl phosphate (TPHP) were the dominant PFRs in dust, while bis(2-chloroethyl) phosphate (BCEP) and diphenyl phosphate (DPHP) were the major DAPs in dust. A significant positive correlation was observed between TPHP and DPHP concentrations in dust (p < 0.001), suggesting their potentially same source and the degradation of TPHP to form DPHP. TCIPP and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) were the predominant PFRs, and BCEP, bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), and DPHP were the main DAPs in both the morning and evening urine samples. The DPHP levels in evening urine samples were significantly correlated with TPHP and DPHP levels (p < 0.01) in dust. A similar correlation was found for the BCEP levels in the evening urine samples and the TCEP and BCEP levels (p < 0.01) in dust. These results indicated that in addition to being biotransformed from their respective parent PFRs, direct ingestion from indoor dust could also be the potential source for urinary DPHP and BCEP. Since relatively low detection frequencies were observed for bis(1-chloro-2-propyl) phosphate (BCIPP) and bis(butoxyethyl) phosphate (BBOEP) in urine, they may not be the major metabolites of TCIPP and tris(2-butoxyethyl) phosphate (TBOEP), respectively, in the human body. However, BDCIPP can be considered a useful biomarker because it is a unique metabolite of TDCIPP and has high detection frequencies in urine samples. The results of this study indicated the limitations of solely using urinary DAPs as biomarkers for the evaluation of human exposure to PFRs, and certain PFRs as well as hydroxylated PFRs (OH-PFRs) should also be considered for urinary biomonitoring in future studies.

Exposure to organophosphate ester flame retardants and plasticizers during pregnancy: Thyroid endocrine disruption and mediation role of oxidative stress

Organophosphate esters (OPEs) are widely used as flame retardants and plasticizers in consumer and industrial products. Human exposure to OPEs raises concerns due to their endocrine disruptive potentials. Till now, the effects of OPEs on thyroid hormones (THs) and the mediating role of oxidative stress in pregnant women have not been studied. In this study, prenatal urinary concentrations of OPE metabolites (mOPEs), levels of free triiodothyronine (FT3), free thyroxine (FT4), thyroid-stimulating hormone (TSH), and oxidative stress levels of 8-hydroxy-2-deoxy guanosine (8-OHdG) and malondialdehyde (MDA) were measured in pregnant women (n = 360) from a coastal urbanized region and moderate socioeconomic status. Neonatal TSH in heel blood was also measured in newborns (n = 309). Dibutyl phosphate (DBP) and diphenyl phosphate (DPHP) were extensively detected with a median creatinine-adjusted level of 0.19 μg/g and 0.66 μg/g, respectively, and the median of ∑mOPEs was 1.82 μg/g. DBP and DPHP were included in the analysis. The concentrations of DBP and DPHP were positively associated with either maternal or neonatal TSH levels, while not for maternal FT3 and FT4 levels. Positive associations for maternal and neonatal TSH were particularly observed in girls as stratified by newborn sex suggesting a sex-selective difference. Furthermore, 8-OHdG, the biomarker of DNA damage, was found to be a major mediator (>60%) for the association between neonatal TSH and DPHP, suggesting that DNA damage is involved in fetal thyroid function disruption. On the other hand, MDA showed a partially suppressing effect (<40%) for the associations between mOPEs and neonatal TSH, which needs further clarification. For maternal TSH, both 8-OHdG and MDA showed moderate mediating effects while the direct effects of mOPEs on maternal TSH also contributed. These results suggest thyroid disrupting effects of OPE exposure on mothers and fetuses during pregnancy and the potential influence mediated by the oxidative stresses of DNA damage and lipid peroxidation.

Human exposure to halogenated and organophosphate flame retardants through informal e-waste handling activities - A critical review

Informal electrical and electronic waste (e-waste) handling activities constitute a potentially important source of halogenated (HFRs) and organophosphate flame retardants (OPFRs) to the environment and humans. In this review, two electronic databases (ScienceDirect and Web of Science Core Collection) were searched for papers that addressed this topic. A total of 82 relevant studies (including 72 studies selected from the two databases and 10 studies located from the references of the first 72 selected studies) were identified that reported on human external and internal exposure to HFRs and OPFRs arising as a result of informal e-waste handling activities. Compared to the general population, higher levels of external exposure (i.e., inhalation, ingestion, and dermal absorption) and internal exposure (i.e., blood serum, hair, breast milk, urine, and other human matrices) to HFRs and OPFRs were identified for e-waste recyclers and residents inhabiting e-waste dismantling and recycling zones, especially for younger adults and children. Food intake and dust ingestion were the dominant exposure pathways for the majority of brominated flame retardants (BFRs) and dechlorane plus (DP); while inhalation was identified as the most significant pathway of human exposure to OPFRs in informal e-waste sites. The majority of research to date has focused on China and thus future studies should be conducted in other regions such as Africa and South Asia. Other suggested foci of future research are: examination of exposure via dermal contact with e-waste, dietary exposure of local populations to OPFRs, confirmation of the existence of and cause(s) of the higher body burdens of females compared with males amongst populations impacted by informal e-waste handling, and characterisation of exposure of such populations to chlorinated paraffins.

A pilot study of organophosphate esters in surface soils collected from Jinan City, China: implications for risk assessments

Data monitoring is a prerequisite for the occurrence of organophosphate esters (OPEs) in the soil environment in light of their potential toxicity, bioaccumulation, and environmental persistence. In this study, we determined the concentrations and profiles of OPEs in surface soils collected from Jinan City, East China. The soil concentrations of ΣOPE (sum of all OPEs) were in the range of 2.55-581 ng/g dry weight (dw), with an average value of 106 ng/g dw. Industrial soils (mean: 433 ng/g dw) had significantly higher levels of ΣOPE compared with those in urban (42.1 ng/g dw) and farmland soils (7.89 ng/g dw) (p < 0.01), suggesting that industrial activity is an important source of OPEs to ambient soil environment. Tris(1-chloro-2-propyl) phosphate (TCIPP), triphenyl phosphate (TPHP), and tris(2-butoxyethyl) phosphate (TBOEP) were the most abundant OPEs in industrial soils, contributing 30%, 25%, and 20% of ΣOPE, respectively. Principal component analysis revealed that TCIPP, TPHP, and TBOEP in soils derived from respective industrial activities. As compared with other cities within China, the surface soil of Jinan City was mildly contaminated by OPEs, and its human exposure and eco-toxicological risks were found to be negligible. Our study provides current contamination status of OPEs in soils across the multiple functional regions of Jinan, which could be used to support the authorities to make relevant regulations.