Influence of storage vial material on measurement of organophosphate flame retardant metabolites in urine

Organophosphate triesters and their diester degradation products in the atmosphere-A critical review

Organophosphate triesters (tri-OPEs) have found substantial use as plasticizers and flame retardants in commercial and industrial products. Despite upcoming potential restrictions on use of OPEs, widespread environmental contamination is likely for the foreseeable future. Organophosphate diesters (di-OPEs) are known biotic or abiotic degradation products of tri-OPEs. In addition, direct use of di-OPEs as commercial products also contributes to their presence in the atmosphere. We review the available data on contamination with tri-OPEs and di-OPEs in both indoor and outdoor air. Concentrations of tri-OPEs in indoor air exceed those in outdoor air. The widespread discovery of tri-OPE traces in polar regions and oceans is noteworthy and is evidence that they undergo long-range transport. There are only two studies on di-OPEs in outdoor air and no studies on di-OPEs in indoor air until now. Current research on di-OPEs in indoor and outdoor air is urgently needed, especially in countries with potentially high exposure to di-OPEs such as the UK and the US. Di-OPE concentrations are higher at e-waste dismantling areas than at surrounding area. We also summarise the methods employed for sampling and analysis of OPEs in the atmosphere and assess the relative contribution to atmospheric concentrations of di-OPEs made by environmental degradation of triesters, compared to the presence of diesters as by-products in commercial triester products. Finally, we identify shortcomings of current research and provide suggestions for future research.

Exposure to flame retardants in European children - Results from the HBM4EU aligned studies

Many legacy and emerging flame retardants (FRs) have adverse human and environmental health effects. This study reports legacy and emerging FRs in children from nine European countries from the HBM4EU aligned studies. Studies from Belgium, Czech Republic, Germany, Denmark, France, Greece, Slovenia, Slovakia, and Norway conducted between 2014 and 2021 provided data on FRs in blood and urine from 2136 children. All samples were collected and analyzed in alignment with the HBM4EU protocols. Ten halogenated FRs were quantified in blood, and four organophosphate flame retardants (OPFR) metabolites quantified in urine. Hexabromocyclododecane (HBCDD) and decabromodiphenyl ethane (DBDPE) were infrequently detected (<16% of samples). BDE-47 was quantified in blood from Greece, France, and Norway, with France (0.36 ng/g lipid) having the highest concentrations. BDE-153 and -209 were detected in <40% of samples. Dechlorane Plus (DP) was quantified in blood from four countries, with notably high median concentrations of 16 ng/g lipid in Slovenian children. OPFR metabolites had a higher detection frequency than other halogenated FRs. Diphenyl phosphate (DPHP) was quantified in 99% of samples across 8 countries at levels ∼5 times higher than other OPFR metabolites (highest median in Slovenia of 2.43 ng/g lipid). FR concentrations were associated with lifestyle factors such as cleaning frequency, employment status of the father of the household, and renovation status of the house, among others. The concentrations of BDE-47 in children from this study were similar to or lower than FRs found in adult matrices in previous studies, suggesting lower recent exposure and effectiveness of PBDE restrictions.

Organophosphate esters in a cohort of pregnant women: Variability and predictors of exposure

Organophosphate esters (OPEs) are a group of chemicals used as flame retardants and plasticizers that replaced polybrominated diphenyl ethers in consumer products such as furniture and electronics. To characterize exposure to OPEs during fetal development, we measured urinary OPE metabolite concentrations in women twice during pregnancy (16 and 26 weeks' gestation) and at delivery (n = 357). We also previously quantified house dust OPE parent compound concentrations at 20 weeks' gestation (n = 317). Diphenyl phosphate (DPHP) had the highest geometric mean urinary concentrations (1.5-2.3 μg/g creatinine), followed by bis(1,3-dichloro-2-propyl) phosphate (BDCIPP; 0.75-0.99 μg/g creatinine), and bis(2-chloroethyl) phosphate (BCEP; 0.72-0.97 μg/g creatinine), while dibutyl phosphate (DNBP) had the lowest concentrations (0.25-0.28 μg/g creatinine). Urinary OPE metabolites were moderately correlated with each other at 26 weeks (rs: 0.23-0.38, p < 0.001) while the correlations at 16 weeks and delivery were slightly weaker. Intra-class correlations for urinary metabolites measured at three time points were poor (0.16-0.34), indicating high variability within individuals. Dust concentrations of OPE parent compounds were associated with BCEP, BDCIPP, and DPHP concentrations in urine at some but not all time points. In linear mixed models of urinary OPE metabolite concentrations, household size was inversely associated with BCEP concentrations, and being non-white was associated with lower BDCIPP and DPHP concentrations. Urine samples collected in the summer had the highest OPE metabolite concentrations. This study highlights the need to collect multiple urine samples during pregnancy to define exposure patterns and investigate potential periods of susceptibility.

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.

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.

Spatial and temporal distribution of organophosphate esters in the atmosphere of the Beijing-Tianjin-Hebei region, China

High volume air samples were collected from April 2016 to March 2017 at five locations across the Beijing-Tianjin-Hebei (BTH) region, to investigate the atmospheric occurrence of organophosphate esters (OPEs). The mean atmospheric concentrations of ∑₈OPEs (gas and particle phases) varied from 531 ± 393 pg/m³ to 2180 ± 1490 pg/m³ with the highest level observed at the urban sampling site in Tianjin City. ∑₈OPEs were predominated by the chlorinated OPEs (TCEP, TCPP, and TDCIPP), which accounted for 60% ± 16% of the OPE concentrations across the BTH region. Generally, higher levels of gaseous OPEs were found in summer, while higher levels of particle-bound OPEs were observed in winter. The concentrations of gaseous OPEs were positively and significantly correlated with local temperatures (p < 0.05) and relative humidity (p < 0.01), while significantly positive correlations were found between concentrations of particle-bound OPEs and total suspended particulates (TSP) (p < 0.01). These findings confirmed that temperatures, relative humidity and levels of TSP are the main drivers for OPE distributions in different seasons and areas. Gas/particle partitioning of OPEs was also investigated based on the absorption-partitioning model (octanol-air partitioning coefficient (K_oa) -based model) and Junge-Pankow adsorption-partitioning model (J-P model). K_oa-based model generally showed a better performance in comparison with the measured results. The assessment of inhalation exposure risks indicated that relatively higher exposure risks were found in the urban areas, in particular, in Tianjin City (a median value of the estimated daily intake (EDI) of 106 pg/kg body weight/day), suggesting that more attention should be drawn to OPE distributions in the heavily industrialized megacities.

Recent biomonitoring reports on phosphate ester flame retardants: a short review

Organophosphate triesters (PEFRs) are used increasingly as flame retardants and plasticizers in a variety of applications, such as building materials, textiles, and electric and electronic equipment. They have been proposed as alternatives to brominated flame retardants. This updated review shows that biomonitoring has gained incrementally greater importance in evaluating human exposure to PEFRs, and it holds the advantage of taking into account the multiple potential sources and various intake pathways of PEFRs. Simultaneous and extensive internal exposure to a broad range of PEFRs have been reported worldwide. Their metabolites, mainly dialkyl or diaryl diesters, have been used as biomarkers of exposure and have been ubiquitously detected in the urine of adults and children in the general population. Concentrations and profiles of PEFR urinary metabolites are seen to be variable and are highly dependent on individual and environmental factors, including age, country regulation of flame retardants, and types and quantities of emissions in microenvironments, as well as analytical procedures. Additional large biomonitoring studies, using a broad range of urinary diesters and hydroxylated metabolites, would be useful to improve the validity of the biomarkers and to refine assessments of human exposure to PEFRs.

Mining the Chemical Information on Urban Wastewater: Monitoring Human Exposure to Phosphorus Flame Retardants and Plasticizers

At the individual level, exposure to contaminants is generally assessed through the analysis of specific biomarkers in biological matrices. However, these studies are costly and logistically demanding, limiting their applicability to monitor population-wide exposure over time and space. By focusing on a selection of exposure biomarkers to phosphorus flame retardants and plasticizers (PFRs), this study aims to explore the possibility of using wastewater as a complementary source of information about exposure. Wastewater samples were collected from five cities in Europe and analyzed using a previously established method. Substantial differences in biomarker levels were observed between the investigated catchments, suggesting differences in exposure. Time trends in biomarkers observed between 2013 and 2016 were found to agree with results from human biomonitoring studies and reports about production volumes. Using Monte Carlo simulations, average urinary concentrations were estimated. These were generally higher compared to results from human biomonitoring studies. Various explanations for these differences were formulated (i.e., other excretion routes, external sources and different sampling approaches). Obtained results show that wastewater analysis provides unique information about geographical and temporal differences in exposure, which would be difficult to gather using other monitoring tools.

Liquid Chromatography-Tandem Mass Spectrometry Analysis of Biomarkers of Exposure to Phosphorus Flame Retardants in Wastewater to Monitor Community-Wide Exposure

Phosphorus flame retardants and plasticizers (PFRs) are increasingly used in consumer goods, from which they can leach and pose potential threats to human health. Monitoring human exposure to these compounds is thus highly relevant. Current assessment of exposure through analysis of biological matrices is, however, tedious as well as logistically and financially demanding. Analysis of selected biomarkers of exposure to PFRs in wastewater could be a simple and complementary approach to monitoring, over space and time, exposure at the population level. An analytical procedure, based on solid-phase extraction (SPE) and liquid chromatography coupled to tandem mass spectrometry, was developed and validated to monitor the occurrence in wastewater of human exposure biomarkers of 2-ethylhexyldiphenyl phosphate (EHDPHP), tris(2-butoxyethyl) phosphate (TBOEP), triphenyl phosphate (TPHP), tris(2-chloroisopropyl) phosphate (TCIPP), and tris(2-chloroethyl) phosphate (TCEP). Various SPE sorbents and extraction protocols were evaluated, and for the optimized method, absolute extraction recoveries ranged between 46% and 100%. Accuracy and precision were satisfactory for the selected compounds. Method detection limits ranged from 1.6 to 19 ng L^-1. Biomarkers of exposure to PFRs were measured for the first time in influent wastewater. Concentrations in samples collected in Belgium ranged from below the limit of quantitation to 1072 ng L^-1, with 2-ethylhexyl phenyl phosphate (EHPHP) and TCEP being the most abundant. Per capita loads of target biomarkers varied greatly, suggesting potential differences in exposure between the investigated communities. The developed method allowed implementation of the concepts of human biomonitoring at the community scale, opening the possibility to assess population-wide exposure to PFRs.

Temporal Trends in Exposure to Organophosphate Flame Retardants in the United States

During the past decade, use of organophosphate compounds as flame retardants and plasticizers has increased. Numerous studies investigating biomarkers (i.e., urinary metabolites) demonstrate ubiquitous human exposure and suggest that human exposure may be increasing. To formally assess temporal trends, we combined data from 14 U.S. epidemiologic studies for which our laboratory group previously assessed exposure to two commonly used organophosphate compounds, tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) and triphenyl phosphate (TPHP). Using individual-level data and samples collected between 2002 and 2015, we assessed temporal and seasonal trends in urinary bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) and diphenyl phosphate (DPHP), the metabolites of TDCIPP and TPHP, respectively. Data suggest that BDCIPP concentrations have increased dramatically since 2002. Samples collected in 2014 and 2015 had BDCIPP concentrations that were more than 15 times higher than those collected in 2002 and 2003 (10^β = 16.5; 95% confidence interval from 9.64 to 28.3). Our results also demonstrate significant increases in DPHP levels; however, increases were much smaller than for BDCIPP. Additionally, results suggest that exposure varies seasonally, with significantly higher levels of exposure in summer for both TDCIPP and TPHP. Given these increases, more research is needed to determine whether the levels of exposure experienced by the general population are related to adverse health outcomes.