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

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.

Can Silicone Passive Samplers be Used for Measuring Exposure of e-Waste Workers to Flame Retardants?

Silicone passive samplers were assessed for measuring personal exposure to 37 flame retardants at three Québec e-waste recycling facilities. Silicone brooches (n = 45), wristbands (n = 28), and armbands (n = 9) worn during a ∼8 h work shift accumulated detectable amounts of 95-100% of the target compounds. Brooch concentrations were significantly correlated with those from active air samplers from which we conclude that the brooches could be used to approximate inhalation exposure and other exposures related to air concentrations such as dermal exposure. The generic sampling rate of the brooch (19 ± 11 m³ day^-1 dm^-2) was 13 and 22 times greater than estimated for home and office environments, respectively, likely because of the dusty work environment and greater movement of e-waste workers. BDE-209 concentrations in brooches and wristbands were moderately and significantly (p < 0.05) correlated with levels in blood plasma; organophosphorus esters in brooches and wristbands were weakly and insignificantly correlated with their metabolite biomarkers in post-shift spot urine samples. Silicone brooches and wristbands deployed over a single shift in a dusty occupational setting can be useful for indicating the internal exposure to compounds with relatively long biological half-lives, but their use for compounds with relatively short half-lives is not clear and may require either a longer deployment time or an integrated biomarker measure.

Diet Shifts Explain Temporal Trends of Pollutant Levels in Indo-Pacific Humpback Dolphins (Sousa chinensis) from the Pearl River Estuary, China

We examined spatiotemporal trends of diet compositions and their relationship with pollutant accumulation levels in 46 weaning Indo-Pacific humpback dolphins (n = 46) from 2004 to 2017 in the Pearl River Estuary (PRE) based on blubber fatty acid signatures using quantitative fatty acid signature analysis in R (QFASAR). Fifty-one potential prey species were tested, among which 13 had a mean relative proportion greater than 1% in dolphin diets. Bombay duck was the predominant prey species, followed by Dussumier's thryssa and mullet, whereas other prey species were present at considerably reduced proportions in diets. The proportion of larger fishes (Bombay duck and mullet) in the diet has exhibited a significant decreasing trend in recent years, whereas the smaller fish (Dussumier's thryssa) steadily increased over the whole period, possibly due to the severe impacts of climate change and other human stressors on large fishes in estuarine waters. The proportions of Bombay duck in the diet were significantly and positively correlated with hepatic Cr levels in dolphins, whereas the temporal change in Bombay duck consumption mirrored that in the hepatic levels of several per- and polyfluoroalkyl substances, because Bombay duck was the most contaminated species among all the prey fishes.

Assessment of the cytotoxic and mutagenic potential of dichlorvos (DDVP) using in silico classification model; a health hazard awareness in Nigeria

Dichlorvos (DDVP) has been abused in Nigeria for suicide attempts, topical applications to treat an ectoparasitic infestation, and indiscriminate use on farm produce. Exposure to this compound in subacute concentration can cause toxicity in different tissues by alteration of the cellular antioxidative defence mechanism. This analysis is aimed at the systematic profiling of DDVP to assess its cytotoxic and mutagenic potential for human vulnerability using an in silico classification model. DDVP was grouped into categories of analogue chemical compounds generated from inventories based on structural alerts that measure the biological effects on cell lines and animal models using the quantitative structure-activity relationship (QSAR) model. The cytotoxic and mutagenic potential of DDVP was assessed by analyzing target endpoints like skin sensitization, oral/inhalation toxicity, neurotoxicity and mutagenicity. DDVP shows moderate sensitization potential that can induce skin irritation during prolonged exposure because of the presence of dichlorovenyl side-chain that interacts with cellular proteins and causes degradation. 50% lethal dose (LD₅₀) of DDVP per body weight was determined to be 26.2 mg/kg in a rat model at 95% confidence range for acute oral toxicity, and 14.4 mmol/L was estimated as 50% lethal concentration (LC₅₀) in the atmosphere due to acute inhalation toxicity. DDVP can also inhibit acetylcholinesterase in the nervous system to produce nicotinic and muscarinic symptoms like nausea, vomiting, lacrimation, salivation, bradycardia, and respiratory failure may cause death. The widely used pesticide causes weak DNA methylation which can repress gene transcription on promoter sites. DDVP is volatile so it can cause oral and inhalation toxicity coupled with neurotoxicity during prolonged exposure. Serum cholinesterase blood tests should be encouraged in federal and state hospitals to investigate related health challenges as DDVP is still used in Nigeria.

Antioxidant alterations link polycyclic aromatic hydrocarbons to blood pressure in children

Exposure to polycyclic aromatic hydrocarbons (PAHs) is associated with changes in blood pressure. However, the association is controversial in different studies, and antioxidants' roles involved in it remain unclear. To investigate the associations among PAH exposure, blood pressure, and antioxidant concentrations, we recruited 403 children (2-7 years old), of which 203 were from Guiyu, an e-waste-recycling area (exposed group), and 200 were from Haojiang, a nearby non-e-waste area (reference group). Levels of blood pressure, plasma vitamin E, serum superoxide dismutase (SOD), serum glutathione peroxidase (GPx), and eight urinary hydroxylated PAHs (OH-PAHs) were measured. Compared with Haojiang children, Guiyu children had higher urinary OH-PAH concentrations but lower systolic pressure, pulse pressure, serum SOD concentration, and serum GPx concentration (all P < 0.05). PAH exposure was associated with lower systolic pressure, pulse pressure, SOD (adjusted β = -0.091, -0.104 and -0.154, respectively, all P < 0.05, in all children), GPx (adjusted β_{∑7LMW-OH-PAHs-T3} = -0.332, only in Haojiang children) and vitamin E (adjusted OR_{∑7LMW-OH-PAHs} = 0.838, 95% CI: 0.706, 0.995, only in Guiyu children). Serum SOD and GPx were associated with higher blood pressure (β_SOD-T2 for diastolic pressure = 0.215 in all children, β_SOD-T3 for systolic pressure = 0.193 in all children, β_SOD-T3 for pulse pressure = 0.281 in high-∑₈OH-PAHs children, β_GPx-T2 = 0.283 and β_GPx-T3 = 0.289 for diastolic pressure in Haojiang children, all P < 0.05). Interactions between PAHs and vitamin E were associated with lower systolic pressure and pulse pressure; simple effects of vitamin E to raise systolic pressure and pulse pressure were only significant in low-∑₈OH-PAHs children. Our results indicate that PAH exposure, especially at high levels, and further antioxidant-decrease are potential risk factors for blood-pressure decrease in children; vascular function of PAH-exposed children may be impaired, manifesting as disordered blood pressure.

Novel and legacy poly- and perfluoroalkyl substances (PFASs) in indoor dust from urban, industrial, and e-waste dismantling areas: The emergence of PFAS alternatives in China

With the phase out of perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA), the composition profiles of poly- and perfluoroalkyl substance (PFAS) in our living environment are unclear. In this study, 25 PFASs were analyzed in indoor dust samples collected from urban, industrial, and e-waste dismantling areas in China. PFOS alternatives, including 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) (median: 5.52 ng/g) and 8:2 chlorinated polyfluorinated ether sulfonate (8:2 Cl-PFESA) (1.81 ng/g), were frequently detected. By contrast, PFOA alternatives, such as hexafluoropropylene oxide dimer acid (HPFO-DA, Gen-X) and ammonium 4,8-dioxa-3H-perfluorononanoate (ADONA), were not found in any of the dust samples. As expected, all legacy PFASs were widely observed in indoor dust, and 4 PFAS precursors were also detected. Dust concentrations of 6:2 Cl-PFESA were strongly correlated (p < 0.05) with those of 8:2 Cl-PFESA regardless of sampling sites. 6:2 Cl-PFESA was also significantly associated with that of PFOS in industrial and e-waste (p < 0.01) areas. Association analysis suggested that the sources of PFOS and its alternatives are common or related. Although ∑Cl-PFESA concentration was lower than that of PFOS (17.4 ng/g), industrial areas had the highest 6:2 Cl-PFESA/PFOS ratio (0.63). Composition profiles of PFASs in the industrial area showed the forefront of fluorine change. Thus, the present findings suggested that Cl-PFESAs are widely used as PFOS alternatives in China, and high levels of human Cl-PFESA exposure are expected in the future. Short-chain PFASs (C4-C7) were the predominant PFASs found in dust samples, contributing to over 40% of ∑total PFASs. Furthermore, perfluoro-1-butanesulfonate/PFOS and perfluoro-n-butanoic acid (PFBA)/PFOA ratios were 2.8 and 0.72, respectively. These findings suggested shifting to the short-chain PFASs in the environment in China. To the authors knowledge this is the first study to document the levels of 6:2 Cl-PFESA, 8:2 Cl-PFESA in indoor dust.

Exposure to heavy metals and its association with DNA oxidative damage in municipal waste incinerator workers in Shenzhen, China

Burning municipal waste produces a great deal of harmful heavy metals, which may lead to elevated exposure in incinerator workers and residents living nearby. However, relevant human exposure studies remain scarce, especially in China. This study aimed to determine the concentrations of ten heavy metals in urine of incinerator workers (n = 119, as the exposed group) and residents living nearby (n = 215, as the control group) from Shenzhen (China), and explore the associations between heavy metal exposure and DNA oxidative stress (indicated by 8-hydroxy-2'-deoxyguanosine or 8-OHdG) in humans. The median urinary concentrations of manganese (Mn), iron (Fe), chromium (Cr), arsenic (As), selenium (Se) and 8-OHdG in the exposed group were significantly higher than those in the control group (p < 0.05), suggesting occupational exposure elevated heavy metal intake for the incinerator workers. Nevertheless, there is no correlation statistically significant between the concentrations of any heavy metal and 8-OHdG in urine in the exposed group, indicating heavy metals releasing from waste incineration were not important factors to induce DNA oxidative stress. To our knowledge, this study firstly reported the concentrations of heavy metal in urine and their associations with DNA oxidative damage in waste incinerator workers in Shenzhen, China.

Benzotriazoles and benzothiazoles prevail in indoor dust from an E-waste dismantling area in South China: Elevated concentrations and implication for human exposure

In this study, 6 BTRs and 9 BTHs were detected in indoor dust samples collected from a typical e-waste dismantling area and adjacent residential areas, as well as from a control urban area. The median ∑BTRs (the total concentrations of BTRs) in e-waste dismantling workshop dust (3830 ng/g) was up to about 21 and 17 times higher than those in the local residential house dust (180 ng/g) and the control urban residential house dust (231 ng/g), respectively. Similarly, significantly higher ∑BTHs (the total concentrations of BTHs) were also found in indoor dust from e-waste workshops (median: 2070 ng/g; range: 590-4430 ng/g) compared to the local residential houses (823 ng/g; 268-3350 ng/g) and the control urban residential houses (930 ng/g; 400-3650 ng/g). These results indicate that e-waste dismantling activities contribute to considerable residues of BTRs and BTHs in indoor dust. Benzotriazole (BTR), benzothiazole (BTH) and 2-hydroxy-benzothiazole (2-OH-BTH) were identified as the predominant compounds across three types of dust samples, cumulatively representing over 80% of ∑BTs (the sum of ∑BTRs and ∑BTHs). The different applications of BTRs and BTHs in e-products were clarified based on correlations analysis. The estimated daily intakes (EDIs) of BTRs and BTHs through dust intake for occupational workers were much higher than those for local and urban residents, implying that a potentially high risk can be posed to occupational workers.

Elevated occupational exposure to chlorinated phosphate esters at a construction materials manufacturing plant

BACKGROUND

Numerous studies have documented that the general population is widely exposed to organophosphate esters (OPEs), yet studies on the emissions of OPEs in the industrial application processes and their occupational exposure are scarce. The aim of this study was to assess the exposure to OPEs for workers engaged in OPE-retarded construction material manufacturing plant in China.

METHOD

Paired dust samples (12 samples each time) from an OPEs retarded building materials manufacturing plant during the plant uptime and downtime have been analyzed for tris(2-chloroethyl)-phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCPP), and other commonly used OPEs. Moreover, nine OPEs metabolites (mOPEs) in urine samples (n = 42) from fourteen workers who engaged in this plant were also measured. The daily exposure doses to OPEs were estimated from the measured urinary concentrations of corresponding mOPEs.

RESULTS

Thirteen out of fourteen studied OPEs (except for tri-n-propyl phosphate, TnPP) were determined in all dust samples from the manufacturing plant, and TCEP and TCPP were the predominant compounds in dust collected from the plant uptime and downtime. Overall, the occupationally exposed population had significantly higher (p < 0.01) urinary levels of mOPE, especially for bis (2-chloroethyl) phosphate (BCEP), relative to the reference population. Workshop workers who directly involved in the production of OPEs treated products had higher OPEs exposure. Risk assessment revealed that cancer risk (1.5 × 10^-6-8.5 × 10^-4) for all workers was larger than 1 × 10^-6 when levels of mOPEs in urine from workers were used for estimating OPEs exposure, revealing moderate to high potential cancer risk to workers from OPEs exposure.

CONCLUSION

To our knowledge, this is the first study reporting emissions of OPEs in OPE-treated products manufacturing processes and the potential exposure of the occupationally exposed population. OPEs, especially for TCEP and TCPP, present at elevated levels and pose moderate to high potential health risks to the exposed workers, emphasizing the importance of strengthening occupational exposure prevention in similar industries.

Predictors and reproducibility of urinary organophosphate ester metabolite concentrations during pregnancy and associations with birth outcomes in an urban population

BACKGROUND

Organophosphate esters (OPEs) are synthetic chemicals used as flame retardants and plasticizers in a variety of goods. Despite ubiquitous human exposures and laboratory evidence that prenatal OPE exposures may disrupt offspring metabolism, perinatal studies of OPE health effects are limited. The objectives of this study were to: 1) Determine predictors and reproducibility of urinary OPE biomarker concentrations during pregnancy, and 2) Estimate the relation of prenatal OPE exposures with birth outcomes and cord blood adipokine and insulin concentrations.

METHODS

We analyzed five OPE metabolites in urine samples collected at up to three visits during pregnancy from 90 women enrolled in the ORigins of Child Health And Resilience in Development (ORCHARD) pregnancy cohort in Baltimore, MD from 2017 to 2019. To quantify the variability of metabolite concentrations during pregnancy, we calculated intraclass correlation coefficients (ICCs) for each metabolite using mixed effects regression models. Using self-reported questionnaire data collected during gestation, we assessed possible sociodemographic and environmental/behavioral predictors of each OPE metabolite using generalized estimating equations to account for repeated exposure measures. We ascertained birth outcomes of 76 offspring from medical records, including weight-for-gestational age, length, ponderal index, and gestational age. In a subset of 37 infants, we measured cord blood concentrations of leptin, adiponectin, and insulin. To account for repeated exposure measures, we used linear structural equation models to assess the relations of standard deviation (SD) increases in prenatal OPE metabolite factor scores with continuous birth outcomes and cord blood biomarker concentrations.

RESULTS

ICCs ranged from 0.09 for isopropylphenyl-phenyl phosphate (ip-PPP) to 0.59 for bis(1,3-dichloro-2-propyl) phosphate (BDCIPP). We observed little consistency in environmental or behavioral predictors of OPE exposures, although concentrations were generally lower for samples collected in the afternoon compared to morning and winter compared to other seasons. In adjusted analyses, a SD increase in BDCIPP concentration was associated with a 0.06 g/cm3 (95% CI: 0.00, 0.12) greater ponderal index. A SD increase in BDCIPP was associated with a 0.37 (95% CI: - 0.62, - 0.13) SD lower insulin concentration and 0.24 (95% CI: - 0.39, - 0.08) SD lower leptin concentration. Other OPEs were not associated with infant outcomes.

CONCLUSIONS

These findings suggest some OPEs may be metabolic disruptors warranting investigation in larger studies.

Organophosphate esters (OPEs) in fine particulate matter (PM2.5) in urban, e-waste, and background regions of South China

Organophosphate esters (OPEs) are a focus of research because they are ubiquitous in the environment; however, there is still a limited understanding of the behaviors and fate of OPEs in the environment. In this study, we measured OPEs in fine particulate matter (PM_2.5) collected from three regions in South China that have potentially different sources. The concentrations of ∑OPEs in the rural electronic waste (e-waste) recycling area (3852-57,695 pg/m³ with a median of 10,955 pg/m³) were significantly higher than those in the urban and background areas with concentrations of 314-9721 pg/m³ (median = 2346 pg/m³) and 667 and 109,599 pg/m³ (median = 2170 pg/m³), respectively. The OPE compositions in the urban and e-waste areas were generally similar. Correlations analysis with other components of PM_2.5 (organic carbon, elemental carbon, and water soluble ions) indicated primary industrial and e-waste sources of OPEs in the urban and e-waste regions, respectively. Correlation analysis also revealed that relative humility played an important role in their air concentrations in the urban and background regions. The air-parcel backward trajectories of the background site demonstrated regional atmospheric transport of OPEs to this region from both the eastern industrial cities and the northern e-waste recycling region.

Dietary intake of legacy and emerging halogenated flame retardants using food market basket estimations in Nanjing, eastern China

Food products are inevitably contaminated by flame retardants throughout their lifecycle (i.e., during production, use, and disposal). In order to evaluate the dietary intake of legacy and emerging halogenated flame retardants (HFRs) in typical market food in China, we investigate the distribution and profile of 27 legacy polybrominated diphenyl ethers (PBDEs) and 16 emerging HFRs (EHFRs) in 9 food categories (meat, poultry, aquatic food, eggs, dairy products, cereals, vegetables, nuts and fruits, and sugar). A total of 105 food samples collected from three markets in Nanjing, eastern China were included for evaluation. The highest concentrations of PBDEs and EHFRs were found in aquatic foods (means of 0.834 ng/g wet weight (ww) and 0.348 ng/g ww, respectively), and the lowest concentrations were found in sugar (means of 0.020 ng/g ww for PBDEs and 0.014 ng/g ww for EHFRs). 2,2',4-tribromodiphenyl ether (BDE-17), a legacy HFR, and hexabromobenzene (HBBz), an EHFR, were the predominant pollutants in the investigated food samples. Concentrations of HBBz and 2,3-dibromopropyl tribromophenyl ether (DPTE) were comparable to those of some PBDEs in certain food samples. The concentrations of the total EHFRs and total PBDEs found in animal-based food samples were significantly greater than those in plant-based food samples. Comparison of the estimated total dietary intake of HFRs and their corresponding non-cancer reference dose (United States Environmental Protection Agency) suggests a low overall health risk. To the best of our knowledge, the present study is the first to simultaneously determine 27 PBDEs and 16 EHFRs in representative foods from Chinese markets. BDE-17, HBBz, and DPTE were the predominant congeners among the 43 investigated HFRs and meat and aquatic foods were the primary sources of PBDEs and EHFRs to the total local dietary intake.

An exploratory analysis of urinary organophosphate ester metabolites and oxidative stress among pregnant women in Puerto Rico

BACKGROUND

Organophosphate esters (OPEs) are used as flame retardants and plasticizers. Oxidative stress, the imbalance of reactive oxygen species and antioxidants, measured prenatally has been associated with adverse birth outcomes including preeclampsia and preterm birth. We are the first study to investigate the relationship between OPEs and oxidative stress among pregnant women.

METHODS

Pregnant women 18-40 yrs. were recruited in Northern Puerto Rico (n = 47) between 2011 and 2015. OPE concentrations of: bis(2-chloroethyl) phosphate (BCEtP), bis(1-chloro-2-propyl) phosphate (BCPP), bis(1,3-dichloro-2-propyl) phosphate (BDCPP), dibutyl phosphate (DNBP), and diphenyl phosphate (DPHP) and biomarkers for oxidative stress, 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 8-isoprostane were measured in urine up to three times during pregnancy. Associations between oxidative stress biomarkers and OPEs were assessed using linear mixed models adjusted for specific gravity, age, BMI, and income.

RESULTS

Metabolites BCEtP, BDCPP, and DPHP were frequently detected (>97%). OPE metabolite concentrations remained stable over time (Intraclass correlation coefficients (ICCs): 0.51-0.60). Metabolites BCEtP, BCPP, and DPHP were associated with an increase in 8-isoprostane and OHdG. An interquartile range (IQR) increase in BDCPP was associated with a 21% increase in 8-isoprostane (p < 0.01), while and IQR increase in DPHP and BCPP was associated with a 12% increase (p = 0.04, p = 0.08, respectively). IQR increases in BDCPP and DPHP were also associated with an 18 and 19% increase in OHdG, respectively (p < 0.01).

CONCLUSION

OPE metabolites were frequently detected and our results suggest that exposure to OPEs is associated with higher levels of oxidative stress. Further investigation into these relationships and birth outcomes is warranted.

Organophosphate ester flame retardants and plasticizers in a Chinese population: Significance of hydroxylated metabolites and implication for human exposure

Organophosphate esters (OPEs) are widely used as flame retardants, plasticizers and defoamers and their exposure are likely associated with a number of adverse effects in humans. In this study, tris(chloroethyl) phosphate and thirteen OPE metabolites including six hydroxylated OPEs (HO-OPEs) were analyzed in 46 urine samples, collected from 8 provinces located across different regions in China. 1-Hydroxy-2-propyl bis(1-chloro-2-propyl) phosphate (BCIPHIPP) and 2-hydroxyethyl bis(2-butoxyethyl) phosphate (BBOEHEP) were major metabolites of their parent compounds with detection frequencies of 54.3%-89.1%, which were all higher than their corresponding OPE diesters (2.2%-6.5%). The urine-based estimated daily intake (EDI) of OPEs ranged from 0.06 ng/kg·bw for tris(2-butoxyethyl) phosphate (TBOEP) to 273 ng/kg·bw for 2-ethylhexyl phenyl phosphate. Analyzed with concentrations in paired dust samples, dust exposure to OPEs and their diesters may explain 0.28%-23.8% of the urine-based EDI of OPEs and the contribution of dust TBOEP was the highest. Although direct exposure to OPE diesters in dust showed a minor contribution, their intake via food and drinking water may account for a larger portion of urinary OPE metabolites. Overall, the hazard quotients of four OPEs indicated no immediate exposure risk for the investigated Chinese residents but the cumulative and long-term chronic effects involving exposure to other OPEs and OPE diesters are worth further concerns.

The environment behavior of organophosphate esters (OPEs) and di-esters in wheat (Triticum aestivum L.): Uptake mechanism, in vivo hydrolysis and subcellular distribution

To reveal the metabolic characteristic of organophosphate esters (OPEs) in plants, uptake efficiency, subcellular distribution and hydrolysis of OPEs and their hydrolysis metabolites in wheat (Triticum aestivum L.) were investigated by hydroponic experiments. Tris(2-chloroethyl) phosphate (TCEP) and bis(2-chloroethyl) phosphate (BCEP) were prone to transporting to shoots by transpiration stream, with the translocation factors of 6.2 and 21 for TCEP and BCEP, respectively, as greater than 40% of TCEP and BECP were distributed in the cell sap due to their hydrophilicity. Hydrophobic OPEs (i.e. tri-n-butyl phosphate [TnBP] and triphenyl phosphate [TPhP]), and their hydrolysis metabolites (di-n-butyl phosphate [DnBP] and diphenyl phosphate [DPhP]) were stored in roots, resulting in low translocation capacity in wheat. As organophosphate diesters with relatively high proportions in cell walls (70-84% of DnBP and 41-43% of DPhP) are difficult to being transmembrane transported due to electrical repulsion of the cytomembrane, it is supposed that cell walls could be a main location for in vivo hydrolysis of OPEs. For DnBP, absorption by roots after in vitro hydrolysis of TnBP in hydroponic media was also an important source in wheat. Inhibition experiments showed that it is usually a non-energy-consuming process for root uptake of OPEs and their hydrolysis metabolites. The uptake of OPEs (i.e. TCEP, TnBP, and TPhP) and DPhP were facilitated diffusion mediated by aquaporins or anion channels, while uptake of BCEP and DnBP were simple diffusion processes. This study illustrated the distribution characteristics and translocation capacity of OPEs and their diester metabolites at the subcellular level.

Estimating renal and hepatic clearance rates of organophosphate esters in humans: Impacts of intrinsic metabolism and binding affinity with plasma proteins

The renal and hepatic clearance rates of organophosphate esters (OPEs) in humans were estimated. Six OPEs and their corresponding diester metabolites (mOPEs) were quantified respectively in 30 paired human plasma and urine samples collected in Hengshui, Hebei province, China. The renal clearance rate (CL_renal) of triphenyl phosphate (TPHP), tris(chloroethyl) phosphate (TCEP) and tris(1,3-dichloro-isopropyl) phosphate (TDCIPP) was estimated to be 68.9, 50.9 and 33.3 mL/kg/day, respectively, while it was not calculated for other three OPEs due to the low detection frequencies in human samples. To estimate the clearance rates of the target OPEs, hepatic clearance rates (CL_h) of OPEs were extrapolated from their in vitro intrinsic clearance data in human liver microsomes (CL_HLM). The calculated CL_h values of TCEP and TDCIPP were comparable to their CL_renal, indicating that the in vitro extrapolation method was suitable for estimating the clearance rates of OPEs. The higher binding affinity of TDCIPP with plasma proteins could reduce its renal clearance. The estimated half-lives of Cl-OPEs in human were longer than those of the aryl- and alkyl-OPEs. This study provided a feasible in vitro method to predict the clearance and half-lives of OPEs in human, which is significant for their accurate health risk assessment.

Urinary metabolites of organophosphate esters and implications for exposure pathways in adolescents from Eastern China

Ten urinary biomarkers of organophosphate esters (OPEs) from six parent OPEs were analyzed in urine from adolescents students in Eastern China. Bis (1,3-dichloro-2-propyl) phosphate, urinary biomarker of tris (1,3-dichloro-2-propyl) phosphate (TDCIPP), was detected in all urine samples with the highest residual concentration of 6.2 ng/mL (median). Bis (1-chloro-propyl) hydroxyl-2-propyl phosphate, dibutyl phosphate, biomarkers of tris (1-chloro-2-propyl) phosphate (TCIPP), tri-n-butyl phosphate (TNBP), respectively, and tris (2-chloroethyl) phosphate (TCEP), were also frequently detected with median concentrations of 1.5, 2.6 and 0.3 ng/mL, respectively. Results indicate that exposure to OPEs, in particular to TDCIPP, TNBP, TCIPP and TCEP, was highly prevalent for adolescent students. The exposure pathways of OPEs were then evaluated according to the OPE internal body burdens (IBBs). Three pathways were identified as the main pathways for adolescents exposed to OPEs including dermal absorption, oral intake of food and dust and inhalation.

Towards establishing indicative values for metabolites of organophosphate ester contaminants in human urine

In 2015, nine laboratories from Belgium, USA, Canada, China, and Australia participated in an interlaboratory exercise to quantify metabolites of organophosphate ester (OPE) contaminants in pooled human urine. Pooled human urine available as SRM 3673 (Organic contaminants in non-smokers' urine) was obtained from the U.S. National Institute of Standards and Technology and was analyzed for its content of OPE metabolites. Each participating laboratory received 10 mL sample and used its own validated method and standards to report the concentrations of the OPE metabolites of its choice. Four OPE metabolites were consistently measured by most laboratories and they were the following diesters: bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), diphenyl phosphate (DPHP), bis(2-chloroethyl) phosphate (BCEP), and bis(1-chloro-2-propyl) phosphate (BCIPP). Concentrations of other OPE metabolites in SRM 3673 were also reported but are only considered as informative values since they were measured by three laboratories at most. All laboratories used liquid chromatography with tandem mass spectrometry (LC-MS/MS) with or without solid-phase extraction (SPE). This is the first study to report indicative values for OPE metabolites in a human urine Standard Reference Material. It is expected that these indicative values obtained for these four metabolites will be used as quality control to ensure compatibility of results in biomonitoring studies and by other researchers who validate their own methods for the quantification of OPE metabolites in human urine.

Organophosphate esters in indoor dust from 12 countries: Concentrations, composition profiles, and human exposure

A total of 20 organophosphate triesters (OPEs), including seven alkyl-OPEs, three chlorinated (Cl)-OPEs, seven aryl-OPEs, and three oligomeric-OPEs were measured in 341 house dust samples collected from 12 countries during the period 2010-2014. OPEs were ubiquitous in indoor dust, and the total concentrations of OPEs (∑OPEs; sum of 20 OPEs) ranged from 49.4 to 249,000 ng/g dry weight (dw). Generally, Cl-OPEs were the predominant compounds (51% of total) in indoor dust samples, with a median concentration of 800 ng/g, followed by alkyl-OPEs (31%), aryl-OPEs (17%), and oligomeric-OPEs (1%), with median concentrations of 480, 270, and 21.9 ng/g, respectively. ∑OPE concentrations in indoor dust from more industrialized countries (South Korea: median, 31,300; Japan: 29,800; and the United States: 26,500 ng/g dw) were one or two orders of magnitude higher than those from less industrialized countries (Greece: 7140, Saudi Arabia: 5310, Kuwait: 4420, Romania: 4110, Vietnam: 1190, China: 1120, Colombia: 374, India: 276, and Pakistan: 138 ng/g dw). Statistically significant positive correlations (0.114 < r < 0.748, p < 0.05) were found among the concentrations of 16 OPEs in dust samples, indicating similar sources of these compounds. The median estimated daily intakes of ΣOPEs via dust ingestion for children and adults were in the ranges of 0.29-64.8 and 0.07-14.9 ng/kg bw/day, respectively.

Short-term variability in levels of urinary phosphate flame retardant metabolites in adults and children from an e-waste recycling site

In the present study, urine samples (n = 258) were collected from adults (n = 42) and children (n = 22) in an electronic waste (e-waste) recycling site. The concentrations and compositions of six di-esters, or the metabolites of phosphate flame retardants (PFRs), were measured at different time points on consecutive days. Bis(2-chloroethyl) phosphate (BCEP), dibutyl phosphate (DBP), bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), and diphenyl phosphate (DPHP) were detected in more than 50% of urine samples. The median concentrations of BCEP, DBP, BDCIPP, and DPHP were 2.43-4.80, 0.09-2.65, 0.46-0.89, and 0.66-1.83 ng/mL in adult urine samples, respectively. For children, the median concentrations of BCEP, DBP, BDCIPP, and DPHP were 1.23, 0.08, 0.06, and 0.29 ng/mL in morning urine samples, and 1.86, 0.12, 0.14, and 0.27 ng/mL in nightfall urine samples, respectively. Nightfall urine had generally higher levels of di-esters than those in morning urine for both adults and children (p < 0.05). Children had significantly lower concentrations of di-esters than adults, indicating the occupational exposure risks of PFRs for adults. Significant correlations were observed in levels of BDCIPP (3 out of 6 groups of samples) and DPHP (2 out of 6 groups of samples) in couples (p<0.05). Significant correlations between parents and boys were only observed in BCEP levels in nightfall urine samples, and in DBP levels in morning urine samples (p<0.05). The results suggest that di-ester concentrations in e-waste recycling workers are highly variable depending on the time that samples are collected, which could further influence the estimation of human exposure to PFRs.

Occurrence, distribution and human exposure to 20 organophosphate esters in air, soil, pine needles, river water, and dust samples collected around an airport in New York state, United States

Organophosphate esters (OPEs) are used in aircraft lubricating oil and hydraulic fluids, and, thus, airplane emissions are thought to be an important source of these chemicals in the environment. In this study, concentrations of 20 OPEs, comprising seven alkyl-OPEs, three chlorinated (Cl)-OPEs, seven aryl-OPEs, and three oligomeric-OPEs, were determined in outdoor air, soil, pine needles, river water, and outdoor dust samples collected around an airport in Albany, New York, in 2018. Elevated ∑OPE concentrations were found in outdoor air, soil, pine needles, outdoor dust, and river water in the ranges of 1320-20,700 pg/m³ (median: 3880), 1.16-73.1 (14.3) ng/g dry weight (dw), 23.2-534 (102) ng/g (dw), 153-2140 (824) ng/g (dw), and 174-24,600 (1250) ng/L, respectively. The total OPE concentrations in air, soil, water, and outdoor dust samples in the study area were dominated by Cl-OPEs, whereas those in pine needles were dominated by aryl-OPEs. The spatial distribution of OPEs in air, soil, and pine needles showed a gradual decreasing trend with increasing distance from the airport. A significant correlation was observed between ∑OPE concentrations in air and soil, and the fugacity ratio showed the flux of OPEs from air to soil. The spatial distribution of OPEs between air and pine needles was similar and highly correlated, suggesting that pine needles are suitable indicators of atmospheric OPE concentrations. In addition to urban activities, aircraft hydraulic/lubricant oils are a major source of OPEs in the vicinity of the airport. The average daily intake of OPEs via air inhalation and outdoor dust ingestion in the vicinity of the airport was up to 1.53 ng/kg bw/day for children and 0.73 ng/kg bw/day for adults.

Simultaneous biomonitoring of 15 organophosphate flame retardants metabolites in urine samples by solvent induced phase transition extraction coupled with ultra-performance liquid chromatography-tandem mass spectrometry

Organophosphate flame retardants and plasticizers (OPFRs) are widely additives in consumer products and building materials. They are frequently detected in environmental media, including indoor air, water, soil, and dust. To provide a low-cost and multi-target tool for monitoring individual exposure to OPFRs, a high-throughput method for simultaneous detection of 15 urinary OFPR metabolites was established using solvent induced phase transition extraction (SIPTE) technique for sample pretreatment and ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) for target quantification. SIPTE is implemented by adding a hydrophobic solvent (methyl tert-butyl ether, used as the phase transition solution) to the homogeneous acetonitrile (ACN) aqueous solution for phase separation. Method performance was validated based on the evaluation indicators. The linear range of this present method was between 0.1 and 50 ng/mL for 15 urinary OPFR metabolites. The limits of detection (LODs) were from 0.012 to 0.25 ng/mL, and the spiked recoveries ranged of 71.3-117.6%, with corresponding relative standard deviations (RSDs) from 4.8 to 25.6%. Unlike most studies only focused on the determination of dialkyl and diaryl phosphate esters (DAPs), our analytical method also covered hydroxylated OPFRs metabolites (OH-OPFRs). Seven DAPs with detection frequencies (DF) more than 60% were detected in a small pilot study (n = 15). Besides, 4-hydroxy diphenyl phosphate (4-HO-DPHP) could be also detected in urine samples. Overall, this newly developed high-throughput analytical method could simultaneously determine 15 urinary OPFRs metabolites and screen these biomarkers of human exposure to OPFRs.

Multiple exposures to organophosphate flame retardants alter urinary oxidative stress biomarkers among children: The Hokkaido Study

Organophosphate flame retardants (PFRs) are used as additives in plastics and other applications such as curtains and carpets as a replacement for brominated flame retardants. As such, exposure to PFR mixtures is widespread, with children being more vulnerable than adults to associated health risks such as allergies and inflammation. Oxidative stress is thought to be able to modulate the development of childhood airway inflammation and atopic dermatitis. To evaluate these associations, the present study investigated the relationship between urinary PFR metabolites, their mixtures and urinary oxidative stress biomarkers in children as part of the Hokkaido Study on Environment and Children's Health. The levels of the oxidative stress biomarkers, such as 8-hydroxy-2'-deoxyguanosine (8-OHdG), hexanoyl-lysine (HEL), and 4-hydroxynonenal (HNE), and of 14 PFR metabolites were measured in morning spot urine samples of 7-year-old children (n = 400). Associations between PFR metabolites or PFR metabolite mixtures and oxidative stress biomarkers were examined by multiple regression analysis and weighted quantile sum regression analysis, respectively. We found that the non-chlorinated PFR metabolites, 2-ethylhexyl phenyl phosphate (EHPHP), bis(2-butoxyethyl) phosphate (BBOEP), and diphenyl phosphate (DPHP) were associated with increased levels of oxidative stress biomarkers. Furthermore, the PFR metabolite mixture was associated with increased levels of HEL and HNE, but not 8-OHdG. The combination of elevated top 2 PFR metabolites was not associated with higher urinary oxidative stress marker levels. This is the first study to report associations between urinary PFR metabolites and oxidative stress biomarkers among children.

Biomonitoring of organophosphate triesters and diesters in human blood in Jiangsu Province, eastern China: Occurrences, associations, and suspect screening of novel metabolites

Since organophosphate (OP) triesters are ubiquitous in environmental matrices, there is an increasing concern regarding human exposure to OP triesters or their metabolites. In this study, we measured levels of 16 OP triesters and 4 OP diesters in n = 99 human blood samples of non-occupationally exposed adults (aged 18-87) from Jiangsu Province, eastern China. Based on the measured concentrations, statistical difference and correlativity were calculated to characterize the population diversity and potential sources of OP triester and diester. Di (2-ethylhexyl) phosphate (DEHP) and 2-ethylhexyl diphenyl phosphate (EHDPP) were found in many participants' blood, with median concentrations of 1.2 (range: n.d. - 44.7, detection frequency: 99%) and 0.85 (n.d. - 28.8, 68%) ng mL^-1, respectively. Blood samples of older participants contained significantly lower concentrations of OP diesters or triesters than their younger counterparts (p < 0.01). Regional- and age-specific differences in the blood concentrations of OP triesters and diesters were attributed to disparities in environmental exposure intensity. EHDPP and tris (phenyl) phosphate (TPHP), the predominant OP triesters, exhibited significant positive correlation (p < 0.01, r = 0.84) suggestive of analogous transport behavior from similar exposure sources to humans. The increased correlations between diphenyl phosphate (DPHP) and TPHP as well as with EHDPP as observed from the multivariate regression suggests that DPHP could be derived from the metabolism of both TPHP (the crucial precursor) and EHDPP. When the blood samples were subsequently screened using high-resolution spectrometry, we detected five novel OP metabolites: glucuronide conjugates of hydroxylated DEHP (OH-DEHP glucuronide conjugate), 2-ethylhexyl monophenyl phosphate (EHMPP), hydroxylated EHMPP (OH-EHMPP), dihydroxylated bis(2-butoxyethyl) phosphate (di-OH-BBOEP), and dihydroxylated tris(butyl) phosphate (di-OH-TNBP). Overall, this study provides novel information regarding the occurrence of OP triesters and diesters, and further suggested several novel OP metabolites in human blood.

Organophosphorus Flame Retardants and Plasticizers in Breast Milk from the United States

Organophosphate esters (OPEs) are used in consumer products as flame retardants and plasticizers. Little is known, however, about the occurrence and profiles of OPEs in human milk. In this study, 14 OPEs were measured in 100 breast milk samples collected from the United States during the period of 2009-2012, using high-performance liquid chromatography and tandem mass spectrometry. The sum concentrations of 14 OPEs in human milk ranged from 0.670 to 7.83 ng/mL, with a mean value of 3.61 ng/mL. The highest mean concentration was found for tris-2-butoxyethyl phosphate (TBOEP, 1.44 ± 0.789 ng/mL), followed by tri-iso-butyl phosphate (TIBP, 0.569 ± 0.272 ng/mL) and tri-n-butyl phosphate (TNBP, 0.539 ± 0.265 ng/mL), which were the dominant OPEs found in breast milk at detection frequencies of >80%. No significant differences were observed between various maternal/infant characteristics and OPE concentrations (p > 0.05), except for TBOEP, for which the median concentrations in Hispanic mothers (0.765 ng/mL) were 2 times lower than those in non-Hispanic mothers (1.48 ng/mL) (p < 0.05). On the basis of the recommended daily milk ingestion rate, the average and the highest daily intakes of total OPEs were calculated to be in the range of 300-542 and 504-911 ng (kg of body weight)^-1 day^-1, respectively. The estimated daily intakes of OPEs did not exceed the current reference doses. Our study establishes baseline data for OPE exposure in breast-fed American children.

Heat evolution and energy analysis of cyanide bioproduction by a cyanogenic microorganism with the potential for bioleaching of precious metals

Precious metals were lost in the current technologies of recovering waste printed circuit boards (WPCBs). Microbe-produced cyanide is considered as an important lixiviant in bioleaching of precious metals from WPCBs. Enhancing cyanide production is the key to industrialization of bioleaching technology. This study identified the precursor form of biogenic cyanide, investigated the energy characteristics of cyanide synthesis, thermal change characteristics of cyanogenic culture, and the potential kinetic relationship between cyanide production and thermal change. We firstly found glycine anion [H₂NCH₂CO₂]- was the precursor form of cyanide in microbial biocatalysis. The bond cleavage pathways from glycine anion to cyanide were analyzed by computation chemical. Results showed decomposition of glycine anion into cyanide was endothermic and non-spontaneous. Formations of [HN = CHCO₂]- and -C≡N have an average energy barrier of 34.05 and 9.15 kcal/mol respectively, while formations of free radicals from anionic intermediates have an average barrier of 71.05 kcal/mol. Cyanide concentration began to increase from 0.48 to 5.27 mg/L when heat production was strongest. Temperature difference between sterile medium and cyanogenic culture reached 0.3 °C. Therefore, metabolic heat brought positive effect on cyanide biosynthesis.

Organophosphate flame retardants (OPFRs) induce genotoxicity in vivo: A survey on apoptosis, DNA methylation, DNA oxidative damage, liver metabolites, and transcriptomics

BACKGROUND

As potential substitutes for polybrominated diphenyl ethers (PBDEs), organophosphate flame retardants (OPFRs) have been frequently detected in the environment. However, the genotoxicity induced by these OPFRs has rarely been described, and the results reported in previous studies are conflicting and inconsistent.

OBJECTIVES

The present study aimed to determine how OPFRs induced genetic toxicity in vivo.

METHODS

Using Chinese rare minnow as a model, the toxicity of three OPFRs was screened with RNA-seq. To verify the OPFR-induced genotoxicity, alkaline comet assay, cell apoptosis analysis, HPLC-based DNA methylation assay, 8-OHdG assay, bioconcentration and biotransformation investigation were performed.

RESULTS

According to transcriptomic data, TDCIPP exposure substantially altered the pathways related to DNA damage, including the cell cycle, DNA replication, Fanconi anemia pathway, p53 signaling pathway, and various DNA repair pathways. Although TBOEP and TPHP did not affect DNA damage, TDCIPP induced DNA damage in a dose-dependent manner. TDCIPP also induced apoptosis, altered the activities of caspase-3 and -9, and increased the 8-OHdG levels, while a significant difference in the levels of DNA methylation induced by OPFRs was not observed.

CONCLUSIONS

Based on these results, TDCIPP induced DNA oxidative damage, eventually leading to genotoxicity in vivo.

Temporal and seasonal variation and ecological risk evaluation of flame retardants in seawater and sediments from Bohai Bay near Tianjin, China during 2014 to 2017

Seawater and sediment samples were collected from 2014 to 2017 at Bohai Bay near Tianjin, China. The median concentration of ΣOPFRs was 2202 ng/l in the seawater from 2017. ΣAlkyl-OPFRs was the predominant constitution in the seawater with a median contribution of nearly 80%, and ΣCl-OPFRs was the major component in the sediment. Regarding BFRs, BDE-209 was the principal one in the sediment. The levels of TEP, TCEP and TBEP in sediments displayed significantly seasonal variations. The summer concentration of TEP was higher than that in both the spring and autumn, and concerning TCEP and TBEP, their lowest concentration occurred in summer. The concentration of ΣOPFRs experienced a rapid increasing during 2014-2016 due to more emissions of OPFRs. The ecological risk evaluation of OPFRs and BFRs suggested a moderate and high risk to the investigated marine region under the high exposure scenario, respectively.

Occurrence and distribution of neonicotinoid insecticides in surface water and sediment of the Guangzhou section of the Pearl River, South China

Little information is available about the occurrence of neonicotinoid insecticides in surface water and sediment of the metropolitan regions around the rivers in China. Here we investigate the residual level of neonicotinoids in the Guangzhou section of the Pearl River. At least one or two neonicotinoids was detected in each surface water and sediment, and the total amount of neonicotinoids (∑₅neonics) in surface water ranged from 92.6 to 321 ng/L with a geometric mean (GM) of 174 ng/L. Imidacloprid, thiamethoxam and acetamiprid were three frequently detected neonicotinoids (100%) from surface water. As for the sediment, total concentration was varied between 0.40 and 2.59 ng/g dw with a GM of 1.12 ng/g dw, and acetamiprid and thiacloprid were the common sediment neonicotinoids. Western and Front river-route of the Guangzhou section of the Pearl River suffered a higher neonicotinoids contamination than the Rear river-route, resulting from more effluents of WWTPs receiving, and intensive commercial and human activities. Level of residual neonicotinoids in surface water was significantly correlated with the water quality (p < 0.01), especially items of pH, DO and ORP, and nitrogen and phosphorus contaminants. Compared with reports about residual neonicotinoids in water and sediment previously, the metropolitan regions of the Guangzhou could be confronted with a moderate contamination and showed serious ecological threats (even heavier than the Pearl Rivers). Our results will provide valuable data for understanding of neonicotinoids contamination in the Pearl River Delta and be helpful for further assessing environmental risk of neonicotinoids.

Exposure of Canadian electronic waste dismantlers to flame retardants

Exposure of e-waste workers to eight halogenated and five organophosphate ester flame retardant chemicals (FRs) was studied at a Canadian e-waste dismantling facility. FR concentrations were measured in air and dust samples collected at a central location and at four work benches over five-24 hour periods spanning two weeks. The highest concentrations in air from workbenches were of BDE-209 (median 156 ng m^-3), followed by Tris(2-chloroethyl) phosphate (TCEP, median 59 ng m^-3). Dust concentrations at the workbenches were higher than those measured at the central location, consistent with the release of contaminated dust during dismantling. Dust concentrations from the workbenches were also dominated by BDE-209 (median 96,300 ng g^-1), followed by Triphenyl phosphate (TPhP, median 47,000 ng g^-1). Most FRs were in coarse particles 5.6-18 μm diameter and ~30% were in respirable particles (<~3 μm). Exposure estimates indicated that dust ingestion accounted for 63% of total FR exposure; inhalation and dermal absorption contributed 35 and 2%, respectively. Some air and dust concentrations as well as some estimated exposures in this formal facility in a high-income country exceeded those from informal e-waste facilities located in low and middle income countries. Although there is demonstrated toxicity of some FRs, FR exposure in the e-waste industry has received minimal attention and occupational limits do not exist for most FRs.

Halogenated flame retardants and organophosphate esters in the air of electronic waste recycling facilities: Evidence of high concentrations and multiple exposures

BACKGROUND

In response to a worldwide increase in production of electronic waste, the e-recycling industry is rapidly rowing. E-recycling workers are exposed to many potentially toxic contaminants, among which flame retardants (FRs), mainly suspected of being endocrine disruptors, are thought to be the most prevalent.

OBJECTIVE

To conduct an exposure assessment of four chemical groups of FRs in Canadian e-recycling facilities, and to identify the main cofactors of exposure.

METHODS

Personal air samples were collected over a workday for 85 workers in six e-recycling facilities, grouped into three facility sizes, and for 15 workers in control commercial waste facilities. Total particulate matter was measured by gravimetry with stationary air samples. FRs were collected on OSHA versatile samplers, which allow particulate and vapor phases collection. Fifteen polybrominated diphenyl ether congeners (PBDEs), nine novel brominated (NBFRs), two chlorinated (ClFRs), and fourteen organophosphate ester (OPEs) flame retardants were analysed by gas chromatography-mass spectrometry. Sociodemographic data, tasks performed and materials processed by participating workers were recorded. Tobit regressions were used to identify cofactors of exposure, and their conclusions were corroborated using semi-parametric reverse Cox regressions.

RESULTS

Thirty-nine of the 40 FRs analysed were detected in at least one air sample in e-recycling, and workers in this industry were exposed on average to 26 (range 12 to 39) different substances. The most detected chemical group of FRs in e-recycling was PBDEs with geometric mean sums of all congeners ranging from 120 to 5100 ng/m³, followed by OPEs with 740 to 1000 ng/m³, NBFRs with 7.6 to 100 ng/m³, and finally ClFRs with 3.9 to 32 mg/m³. The most important cofactor of exposure was the size of the e-recycling facility, with the largest one presenting on average 12 times the concentrations found in the control facility. Among tasks as potential cofactors of exposure, manual dismantling and baler operation exposed workers to some of the highest concentrations of PBDEs and ClFRs. There was a reduction of up to 27% in exposure to FRs associated with a 3-year increase in seniority. Finally, particulate matter concentrations in e-recycling facilities were highly correlated with all chemical classes except OPEs, and were higher in the large facility.

CONCLUSIONS

Among the FRs analysed, PBDE exposure was particularly high in e-recycling. Dust and particulate matter reduction strategies in these workplaces, together with training on proper working practices would certainly be important first steps to lower occupational exposures and prevent potential health effects.

Associations between urinary organophosphate ester metabolites and measures of adiposity among U.S. children and adults: NHANES 2013-2014

BACKGROUND

Organophosphate esters (OPEs) are synthetic chemicals found in many consumer products, including furniture, electronics, processed foods, and building materials. Emerging in vitro and in vivo studies suggest that OPEs are metabolism disrupting compounds; however, epidemiologic studies investigating their associations with adiposity markers are sparse.

OBJECTIVE

We examined cross-sectional associations between OPE biomarkers and adiposity measures among U.S. children and adults participating in the National Health and Nutrition Examination Survey (NHANES: 2013-2014).

METHODS

Concentrations of five OPE metabolites were quantified in urine: diphenyl phosphate (DPHP), bis(1,3-dichloro-2-propyl) phosphate (BDCPP), bis(2-chloroethyl) phosphate (BCEP), dibutyl phosphate (DBUP), and bis(1-chloro-2-propyl) phosphate (BCPP). We conducted covariate-adjusted logistic and linear regressions to examine associations between log2-transformed and dichotomized OPE metabolite concentrations and obesity, body mass index (BMI), and waist circumference (WC), separately among 784 children (6-19 years) and 1672 adults (≥20 years). We also assessed heterogeneity of associations by sex.

RESULTS

DBUP concentrations were inversely associated with the prevalence odds of being obese vs. normal weight in children (adjusted Prevalence Odds Ratio, aPOR: 0.82, 95% Confidence Interval, 95% CI: 0.70, 0.95) and adults (aPOR: 0.83, 95% CI: 0.72, 0.96). DBUP was also significantly associated with lower BMI z-scores (β:-0.08, 95% CI:-0.17, 0.01) and WC (β:-0.71, 95% CI: -1.49, 0.07) in children. BCEP concentrations were associated with increased prevalence odds of being overweight vs. normal weight (aPOR: 1.15, 95% CI: 1.01, 1.32) among children; similar, albeit not statistically significant, relationships were observed with other child adiposity outcomes. Among adults, detectable BCPP concentrations were associated with increased prevalence odds of being obese vs. normal weight (aPOR: 1.70, 95% CI: 1.21, 2.38) and having a high vs. normal WC (aPOR: 1.51, 95% CI: 1.11, 2.07) as well as higher BMI (β: 1.31, 95% CI: 0.30, 2.33). Other OPE metabolites were not consistently associated with adiposity measures among adults. Although associations of BCPP exposure with adiposity outcomes were generally inverse among boys, but not girls, we did not observe consistent evidence of sexually-dimorphic associations for other OPE metabolites.

CONCLUSIONS

Exposure to select OPEs may be differentially associated with body size among children and adults. Given the cross-sectional design of the present study, future prospective studies are needed to confirm these findings.

Human exposure pathways to organophosphate flame retardants: Associations between human biomonitoring and external exposure

Organophosphate flame retardants (PFRs) have largely replaced the market of polybrominated diphenyl ethers (PBDEs). Concerns about PFR contamination and its impact on human health have consequently increased. A comprehensive investigation on the human exposure pathways to PFRs is to be endeavoured. This study investigated the occurrence of PFR metabolites in human urine, serum and hair, correlating them with external exposure data that was presented in our previous studies. Participants from Oslo (n = 61) provided a set of samples, including dust, air, handwipes, food, urine, serum and hair. Associations between PFR metabolites analyzed in the biological samples and the PFRs in environmental samples were explored. Different sampling strategies for dosimeters (e.g. floor/surface dust, personal/stationary air) were also compared to understand which is better for predicting human exposure to PFRs. Seven out of the eleven target PFR metabolites, including diphenyl phosphate (DPHP) and bis(1-chloro-2-propyl)-1-hydroxy-2-propyl phosphate (BCIPHIPP), were frequently detected (DF > 30%) in urine. DPHP was the most frequently detected metabolite in both serum and hair. Several PFR metabolites had higher levels in morning urine than in afternoon urine. Floor dust appeared to be a better proxy for estimating PFR internal exposure than surface dust, air, and handwipes. Some PFRs in handwipes and air were also correlated with their metabolites in urine and hair. Age, beverage consumption and food consumption were negatively associated with DPHP levels in urine. Discrepancies observed between the external and internal exposure for some PFRs call for further investigation on PFR bioaccessibility and clearance.

Temporal variations of PM2.5-bound organophosphate flame retardants in different microenvironments in Beijing, China, and implications for human exposure

In the present study, the temporal distribution of PM_2.5-bound organophosphate flame retardants (OPFRs) was comprehensively investigated in various indoor environments as well as outdoor air in Beijing, China over a one-year period. The mean concentrations of Σ₉OPFRs were 22.7 ng m^-3 and 1.40 ng m^-3 in paired indoor and outdoor PM_2.5, respectively. The concentrations of tri-n-butyl phosphate (TNBP), tris (2-chloroethyl) phosphate (TCEP) and tris (2-chloroisopropyl) phosphate (TCIPP) in indoor PM_2.5 were significantly correlated with those in outdoor PM_2.5. For different indoor microenvironments, mean concentrations of Σ₉OPFRs were in the order of office (29.0 ± 11.7 ng m^-3) > home (24.0 ± 9.4 ng m^-3) > dormitory (19.4 ± 4.9 ng m^-3) > activity room (14.4 ± 3.1 ng m^-3). TCIPP was the most abundant compound in the indoor PM_2.5, followed by TCEP. Significantly higher concentrations of OPFRs were observed in indoor environments with more furnishing, electronics or other materials (p < 0.05). Moreover, lower levels of OPFRs in indoor air were observed at well-ventilated (with higher air exchange rate) indoor sampling sites. Concentrations of Σ₉OPFRs in the activity room, dormitory, homes and outdoor sites generally increased in summer and heating seasons (November 2016 to February 2017). Significant correlations (p < 0.05) were observed between temperatures and mass concentrations of OPFRs with higher vapor pressures, i.e. TNBP, TCEP and TCIPP in all indoor and outdoor samples. Seasonal differences in human exposure were observed and the highest daily exposure dose occurred in summer. Toddlers may suffer the highest exposure risk of PM_2.5-bound OPFRs via inhalation among all age groups. This is one of the very few studies that have revealed the seasonal variation and human exposure of PM_2.5-bound OPFRs in different microenvironments, which shed light on emission sources and fate of OPFRs and potential human exposure pathway.

Organophosphate ester and phthalate ester metabolites in urine from primiparas in Shenzhen, China: Implications for health risks

Organophosphate esters (OPEs) and phthalate esters (PAEs) are extensively used as additives in commercial and household products. However, knowledge on human exposure to OPEs and PAEs remains limited in China. This study aimed to investigate OPE and PAE metabolites in urine samples of primiparas and to evaluate the cumulative risk of OPE and PAE exposure. A total of 8 OPE metabolites and 11 PAE metabolites were measured in urine samples of 84 primiparas from Shenzhen, China. The OPE metabolites were found in at least 72% of the urine samples with bis(2-chloroethyl) phosphate (BCEP) being the dominant analogue. Among the 11 PAE metabolites, mono-n-butyl phthalate (mBP) was the most abundant analogue and had a median concentration (139 μg/L) greater than those reported in urine samples from other countries and regions. A significant, positive correlation was found between Σ₈OPEMs (the sum of 8 OPE metabolites) and body mass index (BMI). The urinary concentration of Σ₁₁PAEMs (the sum of 11 PAE metabolites) was positively associated with the time of computer using by the primiparas. The estimated daily intakes (EDI) of tris(2-chlorethyl) phosphate (TCEP, the parent chemical of BCEP) and di-n-butyl phthalate (DnBP, the parent chemical of mBP) were determined to be 0.47 and 9.14 μg/kg bw/day, respectively. The 95th percentile EDI values for TCEP and DnBP both exceeded their corresponding reference doses. Twelve and fifty-five percentage of the primiparas were estimated to have HI_RfD (hazard index corresponding to reference doses) and HI_TDI (hazard index corresponding to tolerable daily intake) values exceeding 1 for OPEs and PAEs, respectively, suggesting a relatively high exposure risk.

Occurrence of organophosphate flame retardants in farmland soils from Northern China: Primary source analysis and risk assessment

Ninety-eight soil samples were collected from farmland soils from Beijing-Tianjin-Hebei core area, Northern China, where agricultural lands were subjected to contamination from intense urban and industrial activities. Twelve organophosphates flame retardants (OPFRs) were analyzed with total soil concentrations ranging from 0.543 μg/kg to 54.9 μg/kg. Chlorinated OPFRs were dominating at mean level of 3.64 μg/kg and Tris(2-chloroisopropyl) phosphate contributed the most (mean 3.36 ± 5.61 μg/kg, 98.0%). Tris(2-ethylhexyl) phosphate was fully detected at levels of 0.041-1.95 μg/kg. Generally, tris(2-butoxyethyl) phosphate and triphenyl phosphate contributed the most to alkyl- (53.6%) and aryl-OPFRs (54.3%), respectively. The levels of ∑OPFRs close to the core urban areas were significantly higher than those from background sites. The occurrence and fate of OPFRs in soil were significantly associated with total organic carbon content and mostly with fine soil particles (<0.005 mm), and a transfer potential from the atmosphere was predicted with logK_SA values. Comparable soil levels with poly brominated diphenyl ethers s in other studies suggested that the contamination of OPFRs occurred in farmland soil with an increasing trend but currently showed no significant environmental risk based on risk quotient estimation (<1). This investigation warrants further study on behaviors of OPFRs in a soil system and a continual monitoring for their risk assessment.

A nationwide survey of 31 organophosphate esters in sewage sludge from the United States

Organophosphate esters (OPEs) are used as flame retardants and plasticizers in a wide range of consumer products. Nevertheless, studies on the occurrence and inventory of OPEs in sewage sludge are limited. In this study, 20 OP triesters and 11 diesters were measured in 75 archived sewage sludge samples collected from 67 wastewater treatment plants (WWTPs) across the United States (US). The median concentrations of ∑20OP-triesters and ∑11OP-diesters in sludge were 1290 and 78.4 ng/g dry weight (dw), respectively. Sludge samples originating from the Western and Northeastern US contained higher concentrations of OP triesters than did those from the Midwestern and Southern US. Sludge samples from WWTPs with larger treatment capacity (>38 million liters per day) contained higher concentrations of OP diesters (p < 0.05). OP diesters in sludge originated from two sources, triester degradation and direct inputs. Land application of sludge to US soils was estimated to result in annual mass inputs of 12,400-14,900 kg/year of OP triesters and 663-796 kg/year of OP diesters. A hazard assessment was performed for 14 OPEs found in sludge, which suggested a low level of risk at the current land application practices of sludge.

Human exposure to phthalate esters associated with e-waste dismantling: Exposure levels, sources, and risk assessment

Phthalate esters (PAEs) can be released into the environment during the dismantling of electronic waste (e-waste), but urinary levels of PAE metabolites (mPAEs) in humans living in e-waste sites have not been documented. In this study, 11 mPAEs were determined in urine samples collected from participants living in e-waste dismantling sites and a reference area in Southern China. The total urinary concentrations of the 11 mPAEs (∑mPAEs) in the e-waste sites (range: 11.1 ng/mL to 3380 ng/mL) were dominated by mono-(2-isobutyl) phthalate and mono-n-butyl phthalate. Participants living in the e-waste sites had significantly higher (p < 0.05) urinary concentrations of ∑mPAEs (and 5 individual mPAEs) than those in the reference area. Hence, e-waste dismantling activities contributed to human exposure to PAEs. The exposure doses of di-n-butyl phthalate, di(2-ethylhexyl)phthalate, di-iso-butyl phthalate, dimethyl phthalate, and diethyl phthalate were 3.41, 3.04, 1.37, 0.25, and 0.20 μg/kg bw/day, respectively. Furthermore, the health risk assessment in terms of hazard quotient and hazard index showed that approximately 22% of the participants living in the e-waste sites had HI values exceeding 1; importantly, 68% of them were non-adults (i.e., 0-18 years old). In the e-waste sites, 8 of the 11 mPAEs in urine samples had significantly positively associations (r = 0.185-0.358, p < 0.05) with the urinary concentration of 8-hydroxy-2'-deoxyguanosine, a marker of DNA oxidative stress. Therefore, people living in e-waste dismantling areas may have a potential health risk caused by PAE exposure. To the best of our knowledge, this study is the first to measure urinary mPAE levels in people living in e-waste dismantling areas.

Heavy metals in human urine, foods and drinking water from an e-waste dismantling area: Identification of exposure sources and metal-induced health risk

Electronic waste or e-waste dismantling activities are known to release metals. However, the human exposure pathways of metals, and their association with oxidative stress in e-waste dismantling areas (EDAs) remain unclear. In this study, our results revealed elevated geometric mean concentrations in vegetables (Cd 0.096 and Pb 0.35 µg/g fw), rice (Cd 0.15, Pb 0.20, and 12.3 µg/g fw), hen eggs (Cd 0.006 and Pb 0.071 µg/g fw), and human urine (Cd 2.12, Pb 4.98, Cu 22.2, and Sb 0.20 ng/mL). Our calculations indicate that rice consumption source accounted for the overwhelming proportion of daily intakes (DIs) of Cd (61-64%), Cu (85-89%), and Zn (75-80%) in children and adults living in EDA; vegetables were the primary contributors to the DIs of Cd (30-32%); and rice (20-29%), vegetables (28-38%), and dust ingestion (26-45%) were all important exposure sources of Pb. Risk assessment predicted that DIs of Cd, Pb, Cu, and Zn via food consumption poses health risks to local residents of EDAs, and the urinary concentrations of analyzed metals were significantly (Pearson correlation coefficient: r = 0.324-0.710; p < 0.01) associated with elevated 8-OHdG, a biomarker of oxidative stress in humans.

Serum concentrations of bisphenol A and its alternatives in elderly population living around e-waste recycling facilities in China: Associations with fasting blood glucose

In the present study, concentrations of bisphenol A (BPA) and its six alternatives were quantified in serum samples collected from elder population living around an e-waste recycling facilities as well as an reference area in China. BPA, bisphenol AF (BPAF), and bisphenol F (BPF) were frequently detected (detection rates: > 65%) in serum samples collected from residents living near e-waste dismantling facilities, with geometric mean (GM) concentrations of 3.2, 0.0074, and 0.062 ng/mL, respectively. The detection frequencies of other four bisphenols (BPs) in serum samples were lower than 25%, regardless of the sampling areas. Significant difference (Mann-Whitney U-test, p < 0.05) was observed in the serum concentration of BPA, but not BPAF and BPF, between the e-waste recycling and reference areas. This finding indicated e-waste dismantling activities are correlated with human BPA exposure. Significant higher (p < 0.05) detection rates of donors who had abnormal fasting blood glucose (FBG) levels were found in e-waste recycling areas (45%) than those found in reference area. Our results suggested BPA and BPAF exposure might associated with abnormal FBG in participants living in e-waste sites. To our knowledge, this study is first determination of BPs in serum samples and assessment of health risk of elderly people from BPs exposure in e-waste dismantling area.

ROS changes are responsible for tributyl phosphate (TBP)-induced toxicity in the alga Phaeodactylum tricornutum

As a newly emerging environmental contaminant, tributyl phosphate (TBP) is an additive flame retardant of high production volume that is frequently detected in biota and the environment. Despite evidence that TBP is a potential threat to marine organisms, ecotoxicology data for TBP in marine organisms at low trophic levels are scarce. In this study, the acute toxicological effect of TBP on the marine phytoplankton Phaeodactylum tricornutum was thoroughly investigated, and the possible mechanism was explored. The results showed that TBP at concentrations ≥0.2 mg L^-1 significantly inhibited P. tricornutum growth in a clear dose-response manner, with 72-h EC₁₀, EC₂₀, EC₅₀ and EC₉₀ values of 0.067, 0.101, 0.219 and 0.716 mg L^-1, respectively. Algal cells treated with TBP exhibited distorted shapes, ruptured cell membranes and damaged organelles, especially mitochondria. Additionally, apoptosis was triggered, followed by a decrease in mitochondrial membrane potential, indicating that cellular damage occurred during exposure. Although the activities of two antioxidant enzymes, superoxide peroxidase and catalase, were upregulated by TBP at 1.2 mg L^-1, excess reactive oxygen species (ROS) and malondialdehyde still accumulated in algal cells after exposure, suggesting that the cells experienced oxidative stress. Moreover, both growth inhibition and apoptosis were positively correlated with ROS levels and were ameliorated by pretreatment with the ROS scavenger N-acetyl-l-cysteine. Taken together, the results indicate that TBP exposure leads to growth inhibition and cellular damage in P. tricornutum, and a ROS-mediated pathway might contribute to these observed toxicological effects.

Photolysis of enrofloxacin, pefloxacin and sulfaquinoxaline in aqueous solution by UV/H2O2, UV/Fe(II), and UV/H2O2/Fe(II) and the toxicity of the final reaction solutions on zebrafish embryos

In this work, the photolysis of enrofloxacin (ENR), pefloxacin (PEF), and sulfaquinoxaline (SQX) in aqueous solution by UV combined with H₂O₂ or ferrous ions (Fe(II)), as well as Fenton (Fe(II)/H₂O₂) processes, was investigated. In addition, the toxicity of the final reaction solution after UV/H₂O₂/Fe(II) treatment toward zebrafish embryos was determined. The degradation of the test compounds followed pseudo-first-order reaction kinetics. The optimum concentrations of H₂O₂ for ENR, PEF and SQX removal under UV/H₂O₂ treatment were 20, 20 and 5 mM, respectively. The optimum concentrations of Fe(II) for ENR, PEF and SQX removal in the UV/Fe(II) system were 0.25, 10, and 1 mM, respectively. For the UV/H₂O₂/Fe(II) system, pH = 3 is the best initial pH for the degradation of ENR, PEF and SQX with the degradation efficiencies at 100%, 79.1% and 100% after 180 min, respectively. Considering the degradation rate and electrical energy per order of the test compounds, the UV/H₂O₂/Fe(II) process was better than the UV/H₂O₂ and UV/Fe(II) processes because of the greater OH generation. Based on major transformation products of ENR, PEF, and SQX detected during UV/H₂O₂/Fe(II) treatment, the probable degradation pathway of each compound is proposed. The fluorine atom of ENR and PEF was transformed into fluorine ion, and the sulfur atom was transformed into SO₂/SO₄^2-. The nitrogen atom was mainly transformed into NH₃/NH₄⁺. Formic acid, acetic acid, oxalic acid, and fumaric acid were identified in the irradiated solutions and all the test compounds and their intermediates can be finally mineralized. In addition, after the UV/H₂O₂/Fe(II) process, the acute toxicity of the final reaction solutions on zebrafish embryos was lower than that of the initial solution without any treatment. In summary, UV/H₂O₂/Fe(II) is a safe and efficient technology for antibiotic degradation.

Are cell phones an indicator of personal exposure to organophosphate flame retardants and plasticizers?

BACKGROUND

Exposure to organophosphate ester (OPE) flame retardants and plasticizers is widespread and is of concern due to their toxicity.

OBJECTIVES

To investigate relationships between and within OPE concentrations in air, dust, hands, electronic product wipes and urinary metabolites with the goal of identifying product sources and exposure pathways.

METHODS

Women in Toronto and Ottawa, Canada, provided a urine sample, two sets of hand wipes, access to their homes for air and dust sampling, and completed a questionnaire. OPE concentrations were obtained for air and floor dust in the bedroom (n = 51) and most used room (n = 26), hand wipes (n = 204), and surface wipes of handheld (n = 74) and non-handheld electronic devices (n = 125). All air, dust and wipe samples were analyzed for 23 OPE compounds; urine samples (n = 44) were analyzed for 8 OPE metabolites.

RESULTS

Five-8 OPEs were detected in >80% of samples depending on the sample type. OPE median concentrations in hand wipes taken 3 weeks apart were not significantly different. Palms had higher concentrations than the back of hands; both were significantly correlated. Concentrations of 9 OPEs were significantly higher in surface wipes of handheld than non-handheld electronic devices. Six OPEs in hand wipes were significantly correlated with cell phone wipes, with two to four OPEs significantly correlated with tablet, laptop and television wipes. Multiple regression models using hand wipes, cell phone wipes and dust explained 8-33% of the variation in creatinine-adjusted urinary metabolites; air concentrations did not have explanatory power. OPEs in cell phone wipes explained the greatest variation in urinary metabolites.

CONCLUSIONS

Handheld electronic devices, notably cell phones, may either be sources or indicators of OPE exposure through hand-to-mouth and/or dermal uptake.

Metabolites of organophosphate esters in urine from the United States: Concentrations, temporal variability, and exposure assessment

Organophosphate esters (OPEs) are widely used as flame retardants and plasticizers in consumer products, which contributes to widespread exposure of humans. OPE diester metabolites in urine have been used as biomarkers of human exposure to these chemicals. Little is known, however, about occurrence and temporal variability in urinary concentrations of OPE metabolites in humans. In this study, 11 OPE metabolites were measured in 213 urine samples collected from 19 volunteers from Albany, New York, United States, at 3-day intervals for five weeks to investigate temporal variability in urinary concentrations. Diphenyl phosphate (DPHP) and bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) were the major OPE metabolites, detected in all urine samples at specific gravity (SG)-adjusted concentrations (geometric mean, GM) of 1060 and 414 pg/mL and creatinine (Cr)-adjusted concentration (GM) of 404 and 156 ng/g, respectively. Inter-day variability in urinary OPE metabolite concentrations in 19 individuals was evaluated by intraclass correlation coefficients (ICCs). The inter-day variability in Cr-adjusted OPE metabolite concentrations (ICC: 0.31-0.67) was lower than those of SG-adjusted (ICC: 0.19-0.71) and unadjusted urinary concentrations (ICC: 0.24-0.74). BDCIPP (ICC: 0.68) and bis(2-chloroethyl) phosphate (BCEP) (ICC: 0.67) concentrations showed a moderate-to-high reliability over the sampling period, whereas the other nine OPE metabolites exhibited a moderate reliability (ICC: 0.31-0.55). Urine samples were further stratified by gender, age, ethnicity, and body mass index (BMI). The concentrations of BDCIPP and DPHP were significantly lower in males with normal BMI (BMI: 18.5-25 kg/m2) than in females and other BMI categories (p < 0.01). Relatively high ICCs, indicating low inter-day variability, were observed for males (ICC: 0.35-0.71) of 30-40 years of age (ICC: 0.34-0.87) with normal BMI (ICC: 0.28-0.64). The daily exposure doses to OPEs were estimated from urinary concentrations of corresponding OPE metabolites. The estimated doses of triphenyl phosphate (TPHP) and triethyl phosphate (TEP), based on median urinary concentrations of their metabolites, were 19.4 and 24.0 ng/kg bw/day, and the exposure dose to ∑OPEs was estimated at 65.3 ng/kg bw/day. Overall, our results indicate a high ICC for Cr-adjusted urinary concentrations of 11 OPE metabolites in urine.

Concentrations and Dietary Exposure to Organophosphate Esters in Foodstuffs from Albany, New York, United States

Organophosphate esters (OPEs) are ubiquitous contaminants in the environment, but little is known about their occurrence in foodstuffs, an important source of human exposure. In this study, 15 OPEs were measured in foodstuffs and food-packing materials collected from local markets in Albany, New York, United States, for the first time. Among the foodstuffs analyzed, median concentrations of ∑OPEs (sum of 15 OPEs) in meat (6.76 ng/g wet weight; ww) and fish/seafood (7.11 ng/g ww) were higher than those in other food categories. ∑OPEs were found in food packaging at a median concentration of 132 ng/g. The estimated daily dietary intakes (EDIs) of OPE were of 37.9, 135, 56.6, 32.2, and 25.1 ng/kg body weight (bw)/day for infants, toddlers, children, teenagers, and adults, respectively. Meat was a major source (47%) of dietary OPEs exposure in adults, whereas dairy products accounted for 52% of OPE exposures in toddlers.

Urinary metabolites of organophosphate flame retardants in China: Health risk from tris(2-chloroethyl) phosphate (TCEP) exposure

Organophosphate esters (OPs) are substitutes for polybrominated diphenyl ether (PBDE) flame retardants. China is the largest producer of OPs globally, with the production rate increasing at 15% annually. Since some OPs are neurodevelopmental and/or carcinogenic toxicants, human exposure is a concern. In this study, concentrations of eight OP metabolites (mOPs) were measured in human urine samples collected from 13 cities located in Northern, Eastern, Southern, and Southwestern China. All target mOPs were frequently detected with detection rates of 50% to 100%, indicating widespread human exposure to OPs. Bis(2-chloroethyl) phosphate (BCEP; median: 0.68 ng/mL), bis(1-chloro-2-propyl) phosphate (BCIPP; 0.30 ng/mL), diphenyl phosphate (DPHP; 0.30 ng/mL), and dibutyl phosphate (DBP; 0.29 ng/mL) were the dominant mOPs across all participants. Regional differences in concentrations (ΣmOPs varied from 0.86 to 3.7 ng/mL) and composition profiles (contribution of chlorinated mOPs to ΣmOPs varied from 35% to 95%) of mOPs were observed within China. In comparison to the concentrations reported worldwide, urinary DPHP and bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) levels in China were lower, whereas BCEP and DBP levels were comparable or higher. The total daily intake (TDI) of tris(2-chloroethyl) phosphate (TCEP), tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) and triphenyl phosphate (TPHP) were estimated from daily urine excretion rate and the fraction of OP metabolized in human liver microsomes (TDI_HLM) or S9 fraction (TDI_S9). The intake estimates showed that Chinese residents were exposed to TCEP from 96.9 to 46,700 (or 52.2 to 25,200) ng/kg bw/day. Depending on the reference dose, we found that approximately 5% of the individuals exceeded the limit (i.e., 2200 ng/kg bw/day) for TCEP intake. To our knowledge, this is the first nationwide baseline survey to determine urinary levels of mOPs in Chinese residents.

Urinary metabolites of organophosphate flame retardants in 0-5-year-old children: Potential exposure risk for inpatients and home-stay infants

Organophosphate flame retardants (OPFRs) have been commonly observed in indoor dust, food, and drinking water in China, but little is known about their exposure levels or factors leading to exposure in Chinese children. In this study, we measured eight metabolites of OPFRs (mOPFRs) in 227 urine samples collected from 0- to 5-year-old children in China. The high detection rates of mOPFRs (60%-100%) in the collected urine samples demonstrated the widespread exposure of this population to OPFRs. The median concentrations indicated that bis(2-chloroethyl)phosphate (BCEP, 0.85 ng/mL) and diphenyl phosphate (DPHP, 0.27 ng/mL) were the dominant chlorinated mOPFRs and nonchlorinated mOPFRs, respectively. Interestingly, the median urinary levels of bis(1-chloro-2-propyl)phosphate (BCIPP, 6.48 ng/mL) and bis(2-butoxyethyl)phosphate (BBOEP, 0.31 ng/mL) in inpatient infants were one order of magnitude higher (p < 0.01) than those observed in outpatient infants. For home-stay participants, furthermore, infants (0-1 year) had the highest median levels of BCIPP (0.72 ng/mL) and dibutyl phosphate (DBP, 0.14 ng/mL) among the three age groups (i.e., 0-1, >1-3, and >3-5 years), and significantly (p < 0.05) negative age-related relationships were found for both urinary mOPFRs. Two set of data on estimated daily intakes (EDIs) were calculated based on the fraction of OPFR excreted as the corresponding mOPFR (F_UE) in human liver microsomes (EDI_HLM) and S9 fraction (EDI_S9) system, respectively. In general, children have relatively high EDIs of tris(2-chloroethyl)phosphate (TCEP: EDI_HLM = 485 ng/kg bw/day, EDI_S9 = 261 ng/kg bw/day). Furthermore, 17% or 21% of inpatient infants had EDIs that exceeded the reference dose, whereas this value was reduced to 13% in outpatient infants; and this value decreased with age among all home-stay children (0-5 years). Our results indicated that inpatient and home-stay infants had a higher potential risk of OPFR exposure. To our knowledge, this is the first study to identify the elevated urinary levels of mOPFRs in inpatients.

Organophosphorus esters (OPEs) in PM2.5 in urban and e-waste recycling regions in southern China: concentrations, sources, and emissions

Organophosphate esters (OPEs) are novel ubiquitous contaminants that are attracting growing concern, but their emissions into the environment are still poorly understood. In this study, 12 OPEs were measured in fine particulate matter (PM_2.5) at 20 industrial sites in an urban region and four e-waste recycling facilities in a rural region in southern China. There was no significant difference in the concentrations of ∑OPEs between the urban region (519-62,747 pg/m³, median = 2854 pg/m³) and the rural e-waste region (775-13,823 pg/m³, 3321 pg/m³). High OPE concentrations in urban PM_2.5 were generally associated with the electrical, electronic, plastic, and chemical industries. There were no significant correlations between most OPEs in these two regions, suggesting different emission mechanisms. The average emissions of ∑OPEs estimated using a simplified dispersion model were 73.0 kg/yr from the urban industrial point sources and 33.2 kg/yr from the e-waste recycling facilities. The estimated emission inventory from industrial activities in the whole city (3228-4452 kg/yr) was approximately 30-fold higher than that from the e-waste recycling (133 kg/yr) facilities because urban region has a much larger industrial scale. To the best of our knowledge, this is the first effort to model the emissions of OPEs from industrial and e-waste recycling activities to the atmosphere.