Monitoring indoor exposure to organophosphate flame retardants: hand wipes and house dust

Total organic halogen (TOX) in human urine: A halogen-specific method for human exposure studies

Disinfection by-products (DBPs) are a complex mixture of compounds unintentionally formed as a result of disinfection processes used to treat drinking water. Effects of long-term exposure to DBPs are mostly unknown and were the subject of recent epidemiological studies. However, most bioanalytical methods focus on a select few DBPs. In this study, a new comprehensive bioanalytical method has been developed that can quantify mixtures of organic halogenated compounds, including DBPs, in human urine as total organic chlorine (TOCl), total organic bromine (TOBr), and total organic iodine (TOI). The optimized method consists of urine dilution, adsorption to activated carbon, pyrolysis of activated carbon, absorption of gases in an aqueous solution, and halide analysis with ion chromatography and inductively coupled plasma-mass spectrometry. Spike recoveries for TOCl, TOBr, and TOI measurements ranged between 78% and 99%. Average TOCl, TOBr, and TOI concentrations in five urine samples from volunteers who consumed tap water were 1850, 82, and 21.0μg/L as X^-, respectively. Volunteers who consumed spring water (control) had TOCl, TOBr, and TOI average concentrations in urine of 1090, 88, and 10.3μg/L as X^-, respectively. TOCl and TOI in the urine samples from tap water consumers were higher than the control. However, TOBr was slightly lower in tap water urine samples compared to mineral water urine samples, indicating other sources of environmental exposure other than drinking water. A larger sample population that consumes tap water from different cities and mineral water is needed to determine TOCl, TOBr, and TOI exposure from drinking water.

Characterization of Adipogenic Activity of House Dust Extracts and Semi-Volatile Indoor Contaminants in 3T3-L1 Cells

Obesity and metabolic disorders are of great societal concern and generate significant human health care costs. Recently, attention has focused on the potential for environmental contaminants to act as metabolic disruptors. This study sought to evaluate the adipogenic activity of indoor house dust extracts and a suite of semivolatile organic chemicals (SVOCs) that are often ubiquitously detected in indoor environments. 3T3-L1 cells were exposed to extracts of indoor dust or individual SVOCs and assessed for triglyceride accumulation and preadipocyte proliferation. Ten of 11 house dust extracts exhibited significant triglyceride accumulation and/or proliferation at environmentally relevant levels (<20 μg of dust/well), and significant adipogenic activity was also exhibited by 28 of the SVOCs. Notably, pyraclostrobin, dibutyl phthalate, tert-butyl-phenyl diphenyl phosphate, and the isopropylated triaryl phosphates (ITPs) exhibited near maximal or supra-maximal triglyceride accumulation relative to the rosiglitazone-induced maximum. The adipogenic activity in house dust occurred at concentrations below EPA estimated child exposure levels, and raises concerns for human health impacts, particularly in children. Our results delineate a novel potential health threat and identify putative causative SVOCs that are likely contributing to this activity.

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

Use of organophosphate flame retardants (PFRs) has increased over the past decade with the phase out of polybrominated diphenyl ethers. Urinary metabolites of PFRs are used as biomarkers of exposure in epidemiologic research, which typically uses samples collected and stored in polypropylene plastic cryovials. However, a small study suggested that the storage vial material may influence reported concentrations. Therefore, we aimed to examine the influence of the storage vial material on analytical measurement of PFR urinary metabolites. Using urine samples collected from participants in the Environment and Reproductive Health (EARTH) Study, we analyzed the PFR metabolites in duplicate aliquots that were stored in glass and plastic vials (n = 31 pairs). Bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), diphenyl phosphate (DPHP) and isopropyl-phenyl phenyl phosphate (ip-PPP) were detected in 98%, 97% and 87% of duplicates. We observed high correlations between glass-plastic duplicates for BDCIPP (rs = 0.95), DPHP (rs = 0.79) and ip-PPP (rs = 0.82) (p < 0.0001). Urinary ip-PPP was an average of 0.04 ng/ml (p = 0.04) higher among samples stored in glass, with a mean relative difference of 14%. While this difference is statistically significant, it is small in magnitude. No differences were observed for BDCIPP or DPHP, however future research should seek to reduce the potential for type II error (false negatives). We conclude that storing urine samples in polypropylene plastic cryovials may result in slightly reduced concentrations of urinary ip-PPP relative to storage in glass vials and future research should seek to increase the sample size, reduce background variability and consider the material of the urine collection cup.

Influence of sampling approach on concentrations of legacy and "novel" brominated flame retardants in indoor dust

The study investigates the impact of sampling method on the concentrations of PBDEs (BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, BDE-154, BDE-183, and BDE-209) and NBFRs (PBEB, EH-TBB, BEH-TEBP, BTBPE and DBDPE) in indoor dust. A total of 36 dust samples were collected from 12 homes in Birmingham, UK (3 samples per home comprising researcher collected dust - both RCD from the living room (RCDL) and bedroom (RCDB), with an additional householder vacuum dust sample - HHVD). BDE-209 was the predominant compound, with average concentrations of 2642, 2336 and 2634 ng/g in RCDL, RCDB and HHVD respectively. The next most abundant BFR was BEH-TEBP, followed by DBDPE, with average concentrations of 306, 339 and 233 ng/g for BEH-TEBP and 155, 91 and 152 ng/g for DBDPE in RCDL, RCDB and HHVD respectively. Average concentrations of Σ₆tri-hexa-BDEs were 47, 41, and 24 ng/g in RCDL, RCDB and HHVD respectively. With the exception of Σ₆tri-hexa-BDEs, BDE-153, BDE-99 and to some extent BEH-TEBP, no significant differences were found between BFR concentrations in RCD and HHVD. Statistically significant correlations were observed between concentrations of Σ₆tri-hexa-BDEs, BEH-TEBP and DBDPE in HHVD and in both RCDL and RCDB. However, comparison of estimates of exposure via dust ingestion based on these two sampling methods revealed that using householder vacuum dust underestimates exposure, particularly for Σ₆tri-hexa-BDEs, and to some extent for BEH-TEBP. In contrast, HHVD could be a viable alternative to RCD as a metric of exposure for higher brominated BFRs.

Flame retardants and their metabolites in the homes and urine of pregnant women residing in California (the CHAMACOS cohort)

Organophosphate flame retardants (PFRs), used in consumer products since the 1970s, persist in the environment. Restrictions on penta-polybrominated diphenyl ether (PBDE) flame retardants resulted in increased use of Firemaster^® 550 (FM^® 550), and the organophosphate triesters: tris(1,3- dichloro-2-propyl) phosphate (TDCIPP); tris(chloropropyl) phosphate (TCIPP); tris(2-chloroethyl) phosphate (TCEP); and triphenyl phosphate (TPHP). The objectives of this study were to (1) identify determinants of flame retardants (4 PFRs, PentaBDEs and FM^® 550) in house dust, (2) measure urinary PFR metabolites in pregnant women, and (3) estimate health risks from PFR exposure. We measured flame retardants in house dust (n = 125) and metabolites in urine (n = 310) collected in 2000-2001 from Mexican American women participating in the CHAMACOS birth cohort study in California. We detected FM^® 550 and PFRs, including two (TCEP and TDCIPP) known to the state of California to cause cancer, in most dust samples. The maximum TCEP and TDCIPP dust levels were among the highest ever reported although the median levels were generally lower compared to other U.S. cohorts. Metabolites of TDCIPP (BDCIPP: bis(1,3-dichloro-2-propyl) phosphate) and TPHP (DPHP: diphenyl phosphate) were detected in 78% and 79% of prenatal urine samples, respectively. We found a weak but positive correlation between TPHP in dust and DPHP in 124 paired prenatal urine samples (Spearman rho = 0.17; p = 0.06). These results provide information on PFR exposure and risk in pregnant women from the early 2000's and are also valuable to assess trends in exposure and risk given changing fire safety regulations and concomitant changes in chemical flame retardant use.

Graphene Oxide Nanoprisms for Sensitive Detection of Environmentally Important Aromatic Compounds with SERS

Recent advances in graphene-based sensors have shown that heavily oxidized (GO) and reduced graphene oxide (rGO) are attractive materials for environmental sensing due to their unique chemical and physical properties. We describe here the fabrication of nanostructured GO assemblies with Ag nanoprisms for improved detection with surface enhanced Raman scattering (SERS). Specifically, 100-μm-sized, periodic-nanoprism-array domains were fabricated on top of the GO layers by GO-assisted lithography (GOAL). The atomically thin GO underlayers are shown to attract cyclic aromatic molecules to the surface, likely via π-π stacking interactions. The close proximity of the analyte to GO and nanoprism (NP) tips effectively suppresses fluorescent background and affords a plausible tertiary enhancement of photon emissions via an electron charge transfer (CT) process. The adsorption of analyte to rGO-NP leads to the appearance and/or shift of several Raman bands, which provided a means to gain molecular insights into the graphene-enhanced scattering process. The analytical merits were characterized with model compound Rhodamine 6G, where the detection limit could reach subnanomolar concentrations. The nanoprism GO substrates also prove effective for SERS multiplex measurement of several legacy aromatic pollutants. Three tetrachlorobiphenyl isomers could be identified from a mixture using their autonomous nonoverlapping molecular fingerprints, and the substrate offers remarkable trace detection of 2,2',3,3'-tetrachlorobiphenyl (PCB-77).

Potential Glucocorticoid and Mineralocorticoid Effects of Nine Organophosphate Flame Retardants

Organophosphate flame retardants (OPFRs), as alternatives of polybrominated diphenyl ethers (PBDEs), have been frequently detected in the environment and biota, and could pose adverse effects on organisms. However, information on the potential endocrine disruption of OPFRs, especially their effects on steroid hormone receptors, such as glucocorticoid and mineralocorticoid receptors (GR/MR), is limited. In this study, the dual-luciferase reporter gene assay via GR/MR and a H295R steroidogenesis assay were employed to evaluate the endocrine disruption of nine OPFRs. We found TMPP, TPHP, and TDBPP exhibited both GR and MR antagonistic activities, while TNBP and TDCIPP only showed MR antagonistic property within a concentration range of 10^-8 to 10^-5 mol/L(M). In the H295R steroidogenesis assay, the fold changes of eight steroidogenic genes in response to OPFRs were further studied. We found CYP17,CYP21, and CYP11B1 expression were significantly down-regulated following TMPP, TPHP, or TDBPP exposure at a concentration of 2 × 10^-6 M. Meanwhile TMPP decreased the production of cortisol and TDBPP down-regulated the secretion of aldosterone. Our results indicate that some OPFRs can interact with GR and MR, and have the potential to disturb steroidogenesis. Data provided here will be helpful to comprehensively understand the potential endocrine disruption of OPFRs.

Flame Retardant Chemicals in College Dormitories: Flammability Standards Influence Dust Concentrations

Furniture flammability standards are typically met with chemical flame retardants (FRs). FRs can migrate out of products into dust and are linked to cancer, neurological impairment, and endocrine disruption. We collected 95 dust samples from dormitory common areas and student rooms on two U.S. college campuses adhering to two different furniture flammability standards: Technical Bulletin 117 (TB117) and Technical Bulletin 133 (TB133). Because TB133 requires furniture to withstand a much-more-demanding test flame than TB117, we hypothesized that spaces with TB133 furniture would have higher levels of FRs in dust. We found all 47 targeted FRs, including 12 polybrominated diphenyl ether (PBDE) congeners, 19 other brominated FRs, 11 phosphorus FRs (PFRs), 2 Dechlorane-Plus (DP) isomers, and 3 hexabromocyclododecane (HBCDD) isomers in the 95 dust samples. We measured the highest reported U.S. concentrations for a number of FRs, including BDE 209 (up to 990 000 ng/g), which may be used to meet the TB133 standard. We prioritized 16 FRs and analyzed levels in relation to flammability standard as well as presence and age of furniture and electronics. Adherence to TB133 was associated with higher concentrations of BDE 209, decabromodiphenylethane (DBDPE), DPs, and HBCDD compared to adherence to TB117 in univariate models (p < 0.05). Student dormitory rooms tended to have higher levels of some FRs compared to common rooms, likely a result of the density of furniture and electronics. As flammability standards are updated, it is critical to understand their impact on exposure and health risks.

Firemaster® 550 and its components isopropylated triphenyl phosphate and triphenyl phosphate enhance adipogenesis and transcriptional activity of peroxisome proliferator activated receptor (Pparγ) on the adipocyte protein 2 (aP2) promoter

Firemaster^® 550 (FM550) is a chemical mixture currently used as an additive flame retardant in commercial products, and is comprised of 2-ethylhexyl-2,3,4,5-tertrabromobenzoate (TBB), bis(2-ethylhexyl) tetrabromophthalate (TBPH), triphenyl phosphate (TPP), and isopropylated triphenyl phosphate (IPTP). Animal and in vitro studies suggest that FM550, TPP and IPTP may have adipogenic effects and may exert these effects through PPARγ activation. Using murine 3T3-L1 preadipocytes, we investigated the detailed expression of transcription factors and adipogenic markers in response to FM550 and its components. Further we investigated the mechanism of action of the peroxisome proliferator-activated receptor gamma (PPARγ) on downstream targets of the receptor by focussing on the mature adipocyte marker, adipocyte protein 2 (aP2). In addition, we set to elucidate the components responsible for the adipogenic effects seen in the FM550 mixture. We show that FM550 and its components TPP, IPTP, and TBPH, but not TBB induced lipid accumulation in a dose-dependent manner. Interestingly, despite displaying enhanced lipid accumulation, TBPH did not alter the mRNA or protein expression of terminal differentiation markers. In contrast, FM550, TPP, and IPTP treatment enhanced lipid accumulation, and mRNA and protein expression of terminal differentiation markers. To further delineate the mechanisms of action of FM550 and its components we focussed on aP2 promoter activity. For this purpose we used the enhancer region of the mouse aP2 promoter using a 584-bp reporter construct containing an active PPRE located 5.4 kb away from the transcription start site of aP2. Exposure to FM550, IPTP, and TPP significantly increased PPARγ mediated aP2 enhancer activity. Furthermore, we show that TPP- and IPTP-dependent upregulation of aP2 was significantly inhibited by the selective PPARγ antagonist GW9662. In addition, chromatin immunoprecipitation experiments showed that IPTP and TPP treatment led to the recruitment of PPARγ to the regulatory region of aP2.

Variability and predictors of urinary concentrations of organophosphate flame retardant metabolites among pregnant women in Rhode Island

BACKGROUND

Organophospate flame retardants (PFRs) are chemicals of emerging concern due to restrictions on polybrominated diphenyl ether flame retardant formulations. We describe the occurrence, variability, and predictors of urinary metabolites of PFRs among pregnant women.

METHODS

In 2014-2015, 59 women from Providence, RI provided up to 3 spot urine samples during pregnancy (~12, 28, and 35 weeks' gestation). We created a pooled urine sample per woman and measured nine relevant metabolites in individual and pooled samples. We used linear mixed models to calculate intraclass correlation coefficients (ICCs) across the 3 measurements and to assess sociodemographic and dietary predictors of PFRs.

RESULTS

The median (IQR) of bis-2-chloroethyl phosphate (BCEP), bis(1,3-dichloro-2-propyl) phosphate (BDCPP), and diphenyl phosphate (DPhP), the metabolites most frequently detected, from pooled samples were: 0.31 μg/L (0.17-0.54), 1.18 μg/L (0.64-2.19), 0.93 μg/L (0.72-1.97), respectively. We observed fair to good reproducibility for BCEP (ICC = 0.50), BDCPP (ICC = 0.60), and DPhP (ICC = 0.43), and excellent agreement between the urinary flame retardant metabolite concentrations averaged across pregnancy versus pooled urine sample concentrations for BCEP (ICC = 0.95), BDCPP (ICC = 0.89), and DPhP (ICC = 0.93). Adjusting for pertinent sociodemographic factors and gestational week of urine collection, each 1 kg increase in pre-pregnancy weight was associated with greater BCEP (1.1%; 95% CI: 0.1, 2.1), BDCPP (1.5%; 95% CI: 0.3, 2.7), and DPhP (0.5%; 95% CI: 0.0, 1.1). Dietary factors were generally not associated with urinary flame retardant metabolites.

CONCLUSIONS

Urinary concentrations of BCEP, BDCPP, and DPhP were frequently detected among women in this pilot study and had fair reproducibility across pregnancy. Body size may be an important predictor of urinary flame retardant metabolite concentrations.

Associations between urinary diphenyl phosphate and thyroid function

Triphenyl phosphate (TPHP) is a commonly used organophosphate flame retardant and plasticizer with widespread human exposure. Data on health effects of TPHP are limited. Recent toxicological studies suggest TPHP may alter thyroid function. We used repeated measures to assess the temporal variability in urinary concentrations of the TPHP metabolite, diphenyl phosphate (DPHP), and to examine relationships between DPHP concentrations and thyroid hormones. We sampled 51 adults at months 1, 6, and 12 from 2010 to 2011. Urine samples were analyzed for DPHP. Serum samples were analyzed for free and total thyroxine (fT₄, TT₄), total triiodothyronine (TT₃), and thyroid stimulating hormone (TSH). We assessed variability in DPHP using intraclass correlation coefficients (ICCs) and kappa statistics. We used linear mixed-effects models to examine associations between DPHP and thyroid hormones. DPHP was detected in 95% of urine samples. Mean DPHP concentrations were 43% higher in women than men. DPHP showed high within-subject variability (ICC range, 0.13-0.39; kappa range, 0.16-0.39). High versus low (≥2.65 vs. <2.65ng/mL) DPHP in all participants was associated with a 0.43μg/dL (95% confidence interval: 0.15, 0.72) increase in mean TT₄ levels. In sex-stratified analyses, high versus low DPHP was associated with a 0.91μg/dL (95% CI: 0.47, 1.36) increase in mean TT₄ in women. The association was attenuated in men (βeta=0.19; 95% CI: -0.15, 0.52). We found no significant associations between DPHP and fT₄, TT₃, or TSH. We found evidence that TPHP exposure may be associated with increased TT₄ levels, especially in women.

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.

Prevalence of historical and replacement brominated flame retardant chemicals in New York City homes

BACKGROUND

Until their phase-out between 2005 and 2013, polybrominated diphenyl ethers (PBDEs) were added to household products including furniture, rugs, and electronics to meet flammability standards. Replacement brominated flame retardant (BFR) chemicals, including 2-ethylhexyl-2,3,4,5 tetrabromobenzoate (TBB) and bis(2-ethylhexyl) 2,3,4,5-tetrabromophthalate (TBPH), which are components of the Firemaster 550^® commercial mixture, are now being used to meet some flammability standards in furniture. The objective of this analysis was to evaluate the extent to which mothers and their children living in New York City are exposed to PBDEs, TBB, and TBPH.

METHODS

We measured PBDEs, TBB, and TBPH using gas chromatography mass spectrometry in dust (n = 25) and handwipe (n = 11) samples collected between 2012 and 2013 from mothers and children living in New York City. We defined dust as enriched if the proportional distribution for a given BFR exceeded two-thirds of the total BFR content.

RESULTS

We detected PBDEs and TBPH in 100% of dust and handwipe samples and TBB in 100% of dust samples and 95% of handwipe samples. Dust from approximately two-thirds of households was enriched for either PBDEs (n = 9) or for TBB + TBPH (n = 8). Overall, the median house dust concentration of TBB + TBPH (1318 ng/g dust) was higher than that of ΣPentaBDE (802 ng/g dust) and BDE-209 (1171 ng/g dust). Children generally had higher BFR handwipe concentrations compared to mothers (ΣPentaBDE: 73%, BDE-209: 64%, TBB + TBPH: 55%) and within households, BFR concentrations from paired maternal-child handwipes were highly correlated. Among mothers, we found a significant positive relation between house dust and handwipe BDE-209 and TBB + TBPH concentrations.

CONCLUSION

PBDEs, TBB and TBPH are ubiquitous in house dust and handwipes in a sample of mother-child pairs residing in New York City.

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

In this study, three chlorinated (Cl-mOPs) and five nonchlorinated (NCl-mOPs) organophosphate metabolites were determined in urine samples collected from participants living in an electronic waste (e-waste) dismantling area (n = 175) and two reference areas (rural, n = 29 and urban, n = 17) in southern China. Bis(2-chloroethyl) phosphate [BCEP, geometric mean (GM): 0.72 ng/mL] was the most abundant Cl-mOP, and diphenyl phosphate (DPHP, 0.55 ng/mL) was the most abundant NCl-mOP. The GM concentrations of mOPs in the e-waste dismantling sites were higher than those in the rural control site. These differences were significant for BCEP (p < 0.05) and DPHP (p < 0.01). Results suggested that e-waste dismantling activities contributed to human exposure to OPs. In the e-waste sites, the urinary concentrations of bis(2-chloro-isopropyl) phosphate (r = 0.484, p < 0.01), BCEP (r = 0.504, p < 0.01), dibutyl phosphate (r = 0.214, p < 0.05), and DPHP (r = 0.440, p < 0.01) were significantly increased as the concentration of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of DNA oxidative stress, increased. Our results also suggested that human exposure to OPs might be correlated with DNA oxidative stress for residents in e-waste dismantling areas. To our knowledge, this study is the first to report the urinary levels of mOPs in China and examine the association between OP exposure and 8-OHdG in humans.

Estimation of human exposure to halogenated flame retardants through dermal adsorption by skin wipe

This study was undertaken to determine levels of halogenated flame retardants (HFRs) on skin surface to provide preliminary exposure estimates from dermal absorption. Skin wipes of palms, back-of-hands, and forearms were collected from 30 participants by using gauze pads soaked in isopropyl alcohol. Eight polybrominated diphenyl ethers (PBDEs), two novel brominated FRs, and two Dechlorane Plus (DPs) isomers were determined. BDE209, Decabromodiphenylethane (DBDPE), and 1, 2-Bis (2, 4, 6-tribromophenoxy) ethane (BTBPE) were most frequently detected. BDE209 showed the highest median level (1760 ng m^-2), followed by DBDPE (277 ng m^-2) and anti-DP (64 ng m^-2). The comparison of levels on palms and back-of-hands revealed no statistical differences, but both were significantly higher than the levels on forearms. Detections of HFRs on arms suggested that skin areas covered by clothing were exposed to these chemicals likewise. BDE209 and DPs levels from three repeated samples showed moderate to strong reliability over 3 months, while the levels of other compounds were not statistically reliable. Males had significant higher levels than females for most HFRs, while participants' age, time from last hand washing to sampling, and other behaviors contributed limitedly to the variations in levels. Daily uptakes of HFRs through dermal absorption were estimated. The estimated median total exposure from palms, back-of-hands, and forearms were 25.9, 1.6, and 7.2 ng d^-1 for ∑PBDEs, ∑DPs, and ∑NBFRs, respectively, which were in the same ranges as those from diet and dust ingestion for adults in China, suggesting that dermal absorption would be an important exposure route for HFRs.

Occurrence of organophosphorus flame retardants on skin wipes: Insight into human exposure from dermal absorption

This study surveyed occurrences and influencing factors of organophosphorus flame retardants (PFRs) on skin surface. Skin wipe samples from palms, back-of-hands and forearms of 30 adults were collected by using gauze pads soaked in isopropyl alcohol in Beijing, China. Tris(chloropropyl) phosphate isomers (∑TCPP), tris(2-chloroethyl) phosphate (TCEP) and triphenyl phosphate (TPHP) were the most abundant compounds with detection frequencies higher than 97%. ∑TCPP showed the highest mean level (4.6μg/m²), followed by TPHP (2.4μg/m²) and TCEP (1.6μg/m²). Levels on palms were slightly higher than on back-of-hands, and both were substantially higher than those on forearms. TCEP and ∑TCPP levels were strong reliable in three repeated measurements from 4 participants over a three month period (intraclass correlation of coefficient of 0.91 and 0.95, respectively), while TPHP levels were not. Washing with soap and water removed a large fraction of PFRs on hands with median reduction of 76, 72 and 67% for TCEP, ∑TCPP and TPHP, respectively. Paired dust samples, table surface wipe and hand wipe samples were collected from 17 offices (13 surface wipes and 22 hand wipes) in Beijing. Hand wipe TCEP, ∑TCPP and TPHP were neither correlated with dust samples nor with table surface wipe samples. Two methods were used for dermal exposure assessments. The estimated lower median total exposure from palms, back-of-hands and forearms by the relative absorption method were 0.6, 1.0, 0.3ng/kg BW-d for TCEP, ∑TCPP and TPHP, respectively. These estimates were in the same range as those via dust ingestion for adults in Beijing, suggesting dermal absorption is likely a significant pathway of human PFR exposure.

Predictors of urinary flame retardant concentration among pregnant women

BACKGROUND

Organophosphate compounds are commonly used in residential furniture, electronics, and baby products as flame retardants and are also used in other consumer products as plasticizers. Although the levels of exposure biomarkers are generally higher among children and decrease with age, relatively little is known about the individual characteristics associated with higher levels of exposure. Here, we investigate urinary metabolites of several organophosphate flame retardants (PFRs) in a cohort of pregnant women to evaluate patterns of exposure.

METHODS

Pregnant North Carolina women (n=349) provided information on their individual characteristics (e.g. age and body mass index (BMI)) as a part of the Pregnancy Infection and Nutrition Study (2002-2005). Women also provided second trimester urine samples in which six PFR metabolites were measured using mass spectrometry methods.

RESULTS

PFR metabolites were detected in every urine sample, with BDCIPP, DHPH, ip-PPP and BCIPHIPP detected in >80% of samples. Geometric mean concentrations were higher than what has been reported previously for similarly-timed cohorts. Women with higher pre-pregnancy BMI tended to have higher levels of urinary metabolites. For example, those classified as obese at the start of pregnancy had ip-PPP levels that were 1.52 times as high as normal weight range women (95% confidence interval: 1.23, 1.89). Women without previous children also tended to have higher urinary levels of DPHP, but lower levels of ip-PPP. In addition, we saw strong evidence of seasonal trends in metabolite concentrations (e.g. higher DPHP, BDCIPP, and BCIPHIPP in summer, and evidence of increasing ip-PPP between 2002 and 2005).

CONCLUSIONS

Our results indicate ubiquitous exposure to PFRs among NC women in the early 2000s. Additionally, our work suggests that individual characteristics are related to exposure and that temporal variation, both seasonal and annual, may exist.

Characterization of polyurethane foam (PUF) and sorbent impregnated PUF (SIP) disk passive air samplers for measuring organophosphate flame retardants

This study aimed to characterize the uptake of organophosphate esters (OPEs) by polyurethane foam (PUF) and sorbent-impregnated polyurethane foam (SIP) disk passive air samplers (PAS). Atmospheric OPE concentrations were monitored with high-volume active air samplers (HV-AAS) that were co-deployed with passive air samplers. Samples were analyzed for tris(2-chloroisopropyl) phosphate (TCIPP), tri(phenyl) phosphate (TPhP), tris(2-chloroethyl) phosphate (TCEP), and tris(2,3-dichloropropyl) phosphate (TDCIPP). The mean concentration of ∑OPEs in air was 2650 pg/m³ for the HV-AAS. Sampling rates and the passive sampler medium (PSM)-air partition coefficient (K_PSM-Air) were calculated for individual OPEs. The average calculated sampling rates (R) for the four OPEs were 3.6 ± 1.2 and 4.2 ± 2.0 m³/day for the PUF and SIP disks, respectively, and within the range of the recommended default value of 4 ± 2 m³/day. Since most of the OPEs remained in the linear uptake phase during the study, COSMO-RS solvation theory and an oligomer-based model were used to estimate K_PUF-Air for the OPEs. The estimated values of log K_PUF-Air were 7.45 (TCIPP), 9.35 (TPhP), 8.44 (TCEP), and 9.67 (TDCIPP). Finally, four configurations of the PUF and SIP disks were tested by adjusting the distance of the gap opening between the upper and lower domes of the sampler housing: i.e. 2 cm, 1 cm, no gap and 1 cm overlap. The sampling rate did not differ significantly between these four configurations (p < 0.05).

Human exposure to flame-retardants is associated with aberrant DNA methylation at imprinted genes in sperm

Emerging evidence suggests that early exposure to endocrine disrupting chemicals has long-term consequences that can influence disease risk in offspring. During gametogenesis, imprinted genes are reasonable epigenetic targets with the ability to retain and transfer environmental messages. We hypothesized that exposures to organophosphate (OP) flame-retardants can alter DNA methylation in human sperm cells affecting offspring's health. Sperm and urine samples were collected from 67 men in North Carolina, USA. Urinary metabolites of a chlorinated OP, tris(1,3-dichloro-2-propyl) phosphate, and two non-chlorinated OPs, triphenyl phosphate and mono-isopropylphenyl diphenyl phosphate, were measured using liquid-chromatography tandem mass-spectrometry. Sperm DNA methylation at multiple CpG sites of the regulatory differentially methylated regions (DMRs) of imprinted genes GRB10, H19, IGF2, MEG3, NDN, NNAT, PEG1/MEST, PEG3, PLAGL1, SNRPN, and SGCE/PEG10 was quantified using bisulfite pyrosequencing. Regression models were used to determine potential associations between OP concentrations and DNA methylation. We found that men with higher concentrations of urinary OP metabolites, known to originate from flame-retardants, have a slightly higher fraction of sperm cells that are aberrantly methylated. After adjusting for age, obesity-status and multiple testing, exposure to mono-isopropylphenyl diphenyl phosphate was significantly related to hypermethylation at the MEG3, NDN, SNRPN DMRs. Exposure to triphenyl phosphate was associated with hypermethylation at the GRB10 DMR; and tris(1,3-dichloro-2-propyl) phosphate exposure was associated with altered methylation at the MEG3 and H19 DMRs. Although measured methylation differences were small, implications for public health can be substantial. Interestingly, our data indicated that a multiplicity of OPs in the human body is associated with increased DNA methylation aberrancies in sperm, compared to exposure to few OPs. Further research is required in larger study populations to determine if our findings can be generalized.

Do flame retardant chemicals increase the risk for thyroid dysregulation and cancer?

PURPOSE OF REVIEW

Flame retardant chemicals are added to consumer products to reduce fire incidence and severity; approximately 1.5 million tons of these chemicals are used annually. However, their widespread use has led to their ubiquitous presence in the environment and chronic accumulation in human tissues. We summarize current trends in human flame retardant chemical exposure, and review recent data highlighting concerns for thyroid dysregulation and cancer risk in human populations.

RECENT FINDINGS

Polybrominated diphenyl ethers were once commonly used as flame retardant chemicals, but recently were phased out. Exposure is associated with thyroid dysregulation (mainly T4 reductions) in animals, with new work focusing on specific mechanisms of action. Polybrominated diphenyl ethers also impact human thyroid regulation and are related to clinical thyroid disease, but associations appear both dose and life-stage dependent. Emerging data suggest that common alternate flame retardant chemicals may be more potent thyroid disruptors than their predecessors, which is particularly concerning given increasing levels of exposure.

SUMMARY

Potential health impacts of flame retardant chemicals are only beginning to be understood for 'legacy flame retardant chemicals' (i.e., polybrominated diphenyl ethers), and are largely unevaluated for newer-use chemicals. Cumulatively, current data suggest impact on thyroid regulation is likely, potentially implicating flame retardant chemicals in thyroid disease and cancers for which thyroid dysregulation impacts risk or prognosis.

Early-life chemical exposures and risk of metabolic syndrome

The global prevalence of obesity has been increasing at a staggering pace, with few indications of any decline, and is now one of the major public health challenges worldwide. While obesity and metabolic syndrome (MetS) have historically thought to be largely driven by increased caloric intake and lack of exercise, this is insufficient to account for the observed changes in disease trends. There is now increasing evidence to suggest that exposure to synthetic chemicals in our environment may also play a key role in the etiology and pathophysiology of metabolic diseases. Importantly, exposures occurring in early life (in utero and early childhood) may have a more profound effect on life-long risk of obesity and MetS. This narrative review explores the evidence linking early-life exposure to a suite of chemicals that are common contaminants associated with food production (pesticides; imidacloprid, chlorpyrifos, and glyphosate) and processing (acrylamide), in addition to chemicals ubiquitously found in our household goods (brominated flame retardants) and drinking water (heavy metals) and changes in key pathways important for the development of MetS and obesity.

Atmospheric chemical reactions of alternatives of polybrominated diphenyl ethers initiated by OH: A case study on triphenyl phosphate

Many studies have been performed to evaluate the environmental risk caused by alternative flame retardants (AFRs) of polybrominated diphenyl ethers due to their ubiquitous occurrence in the environment. However, as an indispensable component of the environmental risk assessment, the information on atmospheric fate of AFRs is limited although some AFRs have been frequently and highly detected in the atmosphere. Here, a combined quantum chemical method and kinetics modeling were used to investigate atmospheric transformation mechanism and kinetics of AFRs initiated by OH in the presence of O2, taking triphenyl phosphate (TPhP) as a case. Results show that the pathway involving initial OH addition to phenyl of TPhP to form TPhP-OH adduct, and subsequent reaction of the TPhP-OH adduct with O2 to finally form phenol phosphate, is the most favorable for the titled reaction. The calculated overall reaction rate constant is 1.6×10(-12)cm(3) molecule(-1)s(-1), translating 7.6days atmospheric lifetime of TPhP. This clarifies that gaseous TPhP has atmospheric persistence. In addition, it was found that ice surface, as a case of ubiquitous water in the atmosphere, has little effect on the kinetics of the rate-determining step in the OH-initiated TPhP reaction.

WITHDRAWN: Estimation of human exposure to halogenated flame retardants through dermal adsorption by skin wipe

The Publisher regrets that this article is an accidental duplication of an article that has already been published, http://dx.doi.org/10.1016/j.chemosphere.2016.10.015. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.

Results from Screening Polyurethane Foam Based Consumer Products for Flame Retardant Chemicals: Assessing Impacts on the Change in the Furniture Flammability Standards

Flame retardant (FR) chemicals have often been added to polyurethane foam to meet required state and federal flammability standards. However, some FRs (e.g., PBDEs and TDCIPP) are associated with health hazards and are now restricted from use in some regions. In addition, California's residential furniture flammability standard (TB-117) has undergone significant amendments over the past few years, and TDCIPP has been added to California's Proposition 65 list. These events have likely led to shifts in the types of FRs used, and the products to which they are applied. To provide more information on the use of FRs in products containing polyurethane foam (PUF), we established a screening service for the general public. Participants residing in the US were allowed to submit up to 5 samples from their household for analysis, free of charge, and supplied information on the product category, labeling, and year and state of purchase. Between February 2014 and June 2016, we received 1141 PUF samples for analysis from various products including sofas, chairs, mattresses, car seats and pillows. Of these samples tested, 52% contained a FR at levels greater than 1% by weight. Tris(1,3-dichloroisopropyl)phosphate (TDCIPP) was the most common FR detected in PUF samples, and was the most common FR detected in all product categories. Analysis of the data by purchasing date suggests that the use of TDCIPP decreased in recent years, paralleled with an increase in the use of TCIPP and a nonhalogenated aryl phosphate mixture we call "TBPP." In addition, we observed significant decreases in FR applications in furniture products and child car seats, suggesting the use of additive FRs in PUF may be declining, perhaps as a reflection of recent changes to TB-117 and Proposition 65. More studies are needed to determine how these changes in FR use relate to changes in exposure among the general population.

Consumer Product Chemicals in Indoor Dust: A Quantitative Meta-analysis of U.S. Studies

Indoor dust is a reservoir for commercial consumer product chemicals, including many compounds with known or suspected health effects. However, most dust exposure studies measure few chemicals in small samples. We systematically searched the U.S. indoor dust literature on phthalates, replacement flame retardants (RFRs), perfluoroalkyl substances (PFASs), synthetic fragrances, and environmental phenols and estimated pooled geometric means (GMs) and 95% confidence intervals for 45 chemicals measured in ≥3 data sets. In order to rank and contextualize these results, we used the pooled GMs to calculate residential intake from dust ingestion, inhalation, and dermal uptake from air, and then identified hazard traits from the Safer Consumer Products Candidate Chemical List. Our results indicate that U.S. indoor dust consistently contains chemicals from multiple classes. Phthalates occurred in the highest concentrations, followed by phenols, RFRs, fragrance, and PFASs. Several phthalates and RFRs had the highest residential intakes. We also found that many chemicals in dust share hazard traits such as reproductive and endocrine toxicity. We offer recommendations to maximize comparability of studies and advance indoor exposure science. This information is critical in shaping future exposure and health studies, especially related to cumulative exposures, and in providing evidence for intervention development and public policy.

Urinary biomarkers of flame retardant exposure among collegiate U.S. gymnasts

Flame retardants are widely used in polyurethane foam materials including gymnastics safety equipment such as pit cubes and landing mats. We previously reported elevated concentrations of flame retardants in the air and dust of a U.S. gymnastics training facility and elevated PentaBDE in the serum of collegiate gymnasts. Our objective in this pilot study was to compare urinary biomarkers of exposure to other flame retardants and additives of polyurethane foam including tris(1,3-dichloro-2-propyl) phosphate (TDCIPP), triphenyl phosphate (TPHP) and 2-ethylhexyl- 2,3,4,5-tetrabromobenzoate (EH-TBB) in samples collected from 11 collegiate gymnasts before and after a gymnastics practice (n=53 urine samples total). We identified a 50% increase in the TPHP biomarker (p=0.03) from before to after practice, a non-significant 22% increase in the TDCIPP biomarker (p=0.14) and no change for the EH-TBB biomarker. These preliminary results indicate that the gymnastics training environment can be a source of recreational exposure to flame retardants. Such exposures are likely widespread, as we identified flame retardants in 89% of foam samples collected from gyms across the U.S.

Regional comparison of organophosphate flame retardant (PFR) urinary metabolites and tetrabromobenzoic acid (TBBA) in mother-toddler pairs from California and New Jersey

The use of alternative chemical flame retardants in consumer products is increasing as the result of the phase-out of polybrominated diphenyl ethers. Today, the most commonly detected alternatives in residential furniture include the organophosphate flame retardants (PFRs) and the Firemaster (R) 550 mixture (FM550). Urinary levels of dialkyl and diaryl phosphate esters, and 2-ethylhexyl tetrabromobenzoate (EH-TBB) have been used as biomarkers of human exposure to PFRs and FM550, respectively. In a previous study, we demonstrated that toddlers had significantly higher levels of PFRs relative to their mothers in a cohort from New Jersey; however, it is unclear if there are regional differences in exposure. It is possible that exposure to PFRs may be higher in California relative to other US States due to the California flammability standard, as was seen previously observed for PBDEs. In the current study, we examined urinary levels of PFR metabolites and TBBA in 28 mother-child pairs from California, USA, collected in 2015, and compared them with levels measured in our previous study from New Jersey. Urine samples were extracted using solid-phase extraction and analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS). Diphenyl phosphate (DPHP), isopropyl-phenyl phenyl phosphate (ip-PPP), bis(1,3-dichloro-2propyl) phosphate (BDCIPP) and BCIPHIPP conjugates were detected in 100% of mother and child urine samples, while bis(1-chloro-2-propyl) phosphate (BCIPP), tert-butyl-phenyl phenyl phosphate (tb-PPP) and TBBA were detected in < 50% of samples. Interestingly, BCIPHIPP conjugates were detected in 100% of the urine samples, suggesting ubiquitous exposure to the parent compound, tris(1-chloro-2-propyl) phosphate (TCIPP). The current study found significantly higher BDCIPP levels in California toddlers and higher and ip-PPP levels in mothers as compared to the New Jersey cohort, which may be reflective of California's furniture flammability standard. For example, BDCIPP levels in California children were 2.4 times higher than those in New Jersey children. Consistent with our previous work, the current study showed higher PFR and EH-TBB exposure in children, likely due to increased hand-mouth behavior. Children's DPHP and BDCIPP levels, on average, were 5.9 times and 15 times those of their mothers. Positive correlations between paired mothers and their children were shown for DPHP and BCIPHIPP conjugates but not BDCIPP or ip-PPP. In the children, several predictors of hand-mouth behavior were associated with BDCIPP, DPHP and ip-PPP urine levels, but no associations were observed with BCIPHIPP conjugates.

New insight into the levels, distribution and health risk diagnosis of indoor and outdoor dust-bound FRs in colder, rural and industrial zones of Pakistan

This is the first robust study designed to probe selected flame retardants (FRs) in the indoor and outdoor dust of industrial, rural and background zones of Pakistan with special emphasis upon their occurrence, distribution and associated health risk. For this purpose, we analyzed FRs such as polybrominated diphenylethers (PBDEs), dechlorane plus (DP), novel brominated flame retardants (NBFRs) and organophosphate flame retardants (OPFRs) in the total of 82 dust samples (indoor and outdoor) collected three from each zone: industrial, rural and background. We found higher concentrations of FRs (PBDEs, DP, NBFRs and OPFRs) in industrial zones as compared to the rural and background zones. Our results reveal that the concentrations of studied FRs are relatively higher in the indoor dust samples being compared with the outdoor dust and they are ranked as: ∑OPFRs > ∑NBFRs > ∑PBDEs > ∑DP. A significant correlation in the FRs levels between the indoor and outdoor dust suggest the potential intermixing of these compounds between them. The principal component analysis/multiple linear regression predicts the percent contribution of FRs from different consumer products in the indoor and outdoor dust of industrial, rural and background zones to trace their source origin. The FRs detected in the background zones reveal the dust-bound FRs suspended in the air might be shifted from different warmer zones or consumers products available/used in the same zones. Hazard quotient (HQ) for FRs via indoor and outdoor dust intake at mean and high dust scenarios to the exposed populations (adults and toddlers) are found free of risk (HQ < 1) in the target zones. Furthermore, our nascent results will provide a baseline record of FRs (PBDEs, DP, NBFRs and OPFRs) concentrations in the indoor and outdoor dust of Pakistan.

Organophosphate Esters in Canadian Arctic Air: Occurrence, Levels and Trends

Fourteen organophosphate esters (OPEs) were measured in the filter fraction of 117 active air samples from yearly ship-based sampling campaigns (2007-2013) and two land-based stations in the Canadian Arctic, to assess trends and long-range transport potential of OPEs. Four OPEs were detected in up to 97% of the samples, seven in 50% or less of the samples, and three were not detected. Median concentrations of ∑OPEs were 237 and 50 pg m(-3) for ship- and land-based samples, respectively. Individual median concentrations ranged from below detection to 119 pg m(-3) for ethanol, 2-chloro-, phosphate (3:1) (TCEP). High concentrations of up to 2340 pg m(-3) were observed for Tri-n-butyl phosphate (TnBP) at a land-based sampling location in Resolute Bay from 2012, whereas it was only detected in one ship-based sample at a concentration below 100 pg m(-3). Concentrations of halogenated OPEs seemed to be driven by river discharge from the Nelson and Churchill Rivers (Manitoba) and Churchill River and Lake Melville (Newfoundland and Labrador). In contrast, nonhalogenated OPE concentrations appeared to have diffuse sources or local sources close to the land-based sampling stations. Triphenyl phosphate (TPhP) showed an apparent temporal trend with a doubling-time of 11 months (p = 0.044). The results emphasize the increasing relevance of halogenated and nonhalogenated OPEs as contaminants in the Arctic.

Comprehensive Study of Human External Exposure to Organophosphate Flame Retardants via Air, Dust, and Hand Wipes: The Importance of Sampling and Assessment Strategy

We compared the human exposure to organophosphate flame retardants (PFRs) via inhalation, dust ingestion, and dermal absorption using different sampling and assessment strategies. Air (indoor stationary air and personal ambient air), dust (floor dust and surface dust), and hand wipes were sampled from 61 participants and their houses. We found that stationary air contains higher levels of ΣPFRs (median = 163 ng/m(3), IQR = 161 ng/m(3)) than personal air (median = 44 ng/m(3), IQR = 55 ng/m(3)), suggesting that the stationary air sample could generate a larger bias for inhalation exposure assessment. Tris(chloropropyl) phosphate isomers (ΣTCPP) accounted for over 80% of ΣPFRs in both stationary and personal air. PFRs were frequently detected in both surface dust (ΣPFRs median = 33 100 ng/g, IQR = 62 300 ng/g) and floor dust (ΣPFRs median = 20 500 ng/g, IQR = 30 300 ng/g). Tris(2-butoxylethyl) phosphate (TBOEP) accounted for 40% and 60% of ΣPFRs in surface and floor dust, respectively, followed by ΣTCPP (30% and 20%, respectively). TBOEP (median = 46 ng, IQR = 69 ng) and ΣTCPP (median = 37 ng, IQR = 49 ng) were also frequently detected in hand wipe samples. For the first time, a comprehensive assessment of human exposure to PFRs via inhalation, dust ingestion, and dermal absorption was conducted with individual personal data rather than reference factors of the general population. Inhalation seems to be the major exposure pathway for ΣTCPP and tris(2-chloroethyl) phosphate (TCEP), while participants had higher exposure to TBOEP and triphenyl phosphate (TPHP) via dust ingestion. Estimated exposure to ΣPFRs was the highest with stationary air inhalation (median =34 ng·kg bw(-1)·day(-1), IQR = 38 ng·kg bw(-1)·day(-1)), followed by surface dust ingestion (median = 13 ng·kg bw(-1)·day(-1), IQR = 28 ng·kg bw(-1)·day(-1)), floor dust ingestion and personal air inhalation. The median dermal exposure on hand wipes was 0.32 ng·kg bw(-1)·day(-1) (IQR = 0.58 ng·kg bw(-1)·day(-1)) for ΣTCPP. The selection of sampling and assessment strategies could significantly affect the results of exposure assessment.

Organophosphate esters in dust samples collected from Danish homes and daycare centers

Organophosphates are used in a wide range of materials and consumer products and are ubiquitous in indoor environments. Certain organophosphates have been associated with various adverse health effects. The present paper reports mass fractions of organophosphates in dust samples collected from 500 bedrooms and 151 daycare centers of children living in Odense, Denmark. The identified compounds include: tris(isobutyl) phosphate (TIBP), tri-n-butyl phosphate (TNBP), tris(2-chloroethyl) phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCIPP), tris(1,3-dichloroisopropyl) phosphate (TDCIPP), tris(2-butoxyethyl) phosphate (TBOEP), triphenylphosphate (TPHP), 2-ethylhexyl-diphenyl phosphate (EHDPP), tris(2-ethylhexyl) phosphate (TEHP) and tris(methylphenyl) phosphate (TMPP). Both the number of organophosphates with median values above the limit of detection and the median values were higher for samples from daycare centers than for samples from homes. Organophosphates with median mass fractions above the limit of detection were: TCEP from homes (6.9 μg g(-1)), and TCEP (16 μg g(-1)), TCIPP (5.6 μg g(-1)), TDCIPP (7.1 μg g(-1)), TBOEP (26 μg g(-1)), TPHP (2.0 μg g(-1)) and EHDPP (2.1 μg g(-1)) from daycare centers. When present, TBOEP was typically the most abundant of the identified OPs. The sum of the organophosphate dust mass fractions measured in this study was roughly in the mid-range of summed mass fractions reported for dust samples collected in other countries. On a global scale, the geographical distribution of organophosphates in indoor dust is quite variable, with higher concentrations in industrialized countries. This trend differs from that for phthalate esters, whose geographic distribution is more homogeneous. Exposure to organophosphates via dust ingestion is relatively low, although there is considerable uncertainly in this assessment.

Characterizing Flame Retardant Applications and Potential Human Exposure in Backpacking Tents

Flame retardant (FR) chemicals are applied to products to meet flammability standards; however, exposure to some additive FRs has been shown to be associated with adverse health effects. Previous research on FR exposure has primarily focused on chemicals applied to furniture and electronics; however, camping tents sold in the United States, which often meet flammability standard CPAI-84, remain largely unstudied in regards to their chemical treatments. In this study, FRs from five brands of CPAI-84-compliant, two-person backpacking tents were measured and potential exposure was assessed. Dermal and inhalation exposure levels were assessed by collecting hand wipes from 20 volunteers before and after tent setup and by using active air samplers placed inside assembled tents, respectively. Organophosphate flame retardants (OPFRs) were the most commonly detected FR in the tent materials and included triphenyl phosphate (TPHP), tris(1,3-dichloro-2-propyl)phosphate (TDCIPP) and tris(2-chloroethyl)phosphate (TCEP). Levels of OPFRS measured on hand wipes were significantly higher post-tent setup compared to pre setup, and in the case of TDCIPP, levels were 29 times higher post setup. OPFRs were also detected at measurable concentrations in the air inside of treated tents. Significant, positive correlations were found between FR levels in treated textiles and measures of dermal and inhalation exposure. These results demonstrate that dermal exposure to FRs occurs from handling camping tents and that inhalation exposure will likely occur while inside a tent.

Measuring Personal Exposure to Organophosphate Flame Retardants Using Silicone Wristbands and Hand Wipes

Organophosphate flame retardants (PFRs) are widely used as replacements for polybrominated diphenyl ethers in consumer products. With high detection in indoor environments and increasing toxicological evidence suggesting a potential for adverse health effects, there is a growing need for reliable exposure metrics to examine individual exposures to PFRs. Silicone wristbands have been used as passive air samplers for quantifying exposure in the general population and occupational exposure to polycyclic aromatic hydrocarbons. Here we investigated the utility of silicone wristbands in measuring exposure and internal dose of PFRs through measurement of urinary metabolite concentrations. Wristbands were also compared to hand wipes as metrics of exposure. Participants wore wristbands for 5 consecutive days and collected first morning void urine samples on 3 alternating days. Urine samples were pooled across 3 days and analyzed for metabolites of the following PFRs: tris(1,3-dichloroisopropyl) phosphate (TDCIPP), tris(1-chloro-2-isopropyl) phosphate (TCIPP), triphenyl phosphate (TPHP), and monosubstituted isopropylated triaryl phosphate (mono-ITP). All four PFRs and their urinary metabolites were ubiquitously detected. Correlations between TDCIPP and TCIPP and their corresponding urinary metabolites were highly significant on the wristbands (rs = 0.5-0.65, p < 0.001), which suggest that wristbands can serve as strong predictors of cumulative, 5-day exposure and may be an improved metric compared to hand wipes.

A mechanism-based 3D-QSAR approach for classification and prediction of acetylcholinesterase inhibitory potency of organophosphate and carbamate analogs

Organophosphate (OP) and carbamate esters can inhibit acetylcholinesterase (AChE) by binding covalently to a serine residue in the enzyme active site, and their inhibitory potency depends largely on affinity for the enzyme and the reactivity of the ester. Despite this understanding, there has been no mechanism-based in silico approach for classification and prediction of the inhibitory potency of ether OPs or carbamates. This prompted us to develop a three dimensional prediction framework for OPs, carbamates, and their analogs. Inhibitory structures of a compound that can form the covalent bond were identified through analysis of docked conformations of the compound and its metabolites. Inhibitory potencies of the selected structures were then predicted using a previously developed three dimensional quantitative structure-active relationship. This approach was validated with a large number of structurally diverse OP and carbamate compounds encompassing widely used insecticides and structural analogs including OP flame retardants and thio- and dithiocarbamate pesticides. The modeling revealed that: (1) in addition to classical OP metabolic activation, the toxicity of carbamate compounds can be dependent on biotransformation, (2) OP and carbamate analogs such as OP flame retardants and thiocarbamate herbicides can act as AChEI, (3) hydrogen bonds at the oxyanion hole is critical for AChE inhibition through the covalent bond, and (4) π-π interaction with Trp86 is necessary for strong inhibition of AChE. Our combined computation approach provided detailed understanding of the mechanism of action of OP and carbamate compounds and may be useful for screening a diversity of chemical structures for AChE inhibitory potency.

Hair and Nails as Noninvasive Biomarkers of Human Exposure to Brominated and Organophosphate Flame Retardants

After the phase-out of polybrominated diphenyl ethers (PBDEs), the use of alternative flame retardants (AFRs), such as FireMaster 550, and of organophosphate esters (OPEs) has increased. However, little is known about human exposure to these chemicals. This lack of biomonitoring studies is partially due to the absence of reliable noninvasive biomarkers of exposure. Human hair and nails can provide integrated exposure measurements, and as such, these matrices can potentially be used as noninvasive biomarkers of exposure to these flame retardants. Paired human hair, fingernail, toenail, and serum samples obtained from 50 adult participants recruited at Indiana University Bloomington campus were analyzed by gas chromatographic mass spectrometry for 36 PBDEs, 9 AFRs, and 12 OPEs. BDE-47, BDE-99, 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (TBB), di(2-ethylhexyl) tetrabromophthalate (TBPH), tris(1,3-dichloro-2-propyl)phosphate (TDCIPP), and triphenyl phosphate (TPHP) were the most abundant compounds detected in almost all hair, fingernail, and toenail samples. The concentrations followed the order OPEs > TBB+TBPH > Σpenta-BDE. PBDE levels in the hair and nail samples were significantly correlated with their levels in serum (P < 0.05), suggesting that human hair and nails can be used as biomarkers to assess human exposure to PBDEs.

Nail polish as a source of exposure to triphenyl phosphate

Triphenyl phosphate (TPHP) is primarily used as either a flame retardant or plasticizer, and is listed as an ingredient in nail polishes. However, the concentration of TPHP in nail polish and the extent of human exposure following applications have not been previously studied. We measured TPHP in ten different nail polish samples purchased from department stores and pharmacies in 2013-2014. Concentrations up to 1.68% TPHP by weight were detected in eight samples, including two that did not list TPHP as an ingredient. Two cohorts (n=26 participants) were recruited to assess fingernail painting as a pathway of TPHP exposure. Participants provided urine samples before and after applying one brand of polish containing 0.97% TPHP by weight. Diphenyl phosphate (DPHP), a TPHP metabolite, was then measured in urine samples (n=411) and found to increase nearly seven-fold 10-14h after fingernail painting (p<0.001). To determine relative contributions of inhalation and dermal exposure, ten participants also painted their nails and painted synthetic nails adhered to gloves on two separate occasions, and collected urine for 24h following applications. Urinary DPHP was significantly diminished when wearing gloves, suggesting that the primary exposure route is dermal. Our results indicate that nail polish may be a significant source of short-term TPHP exposure and a source of chronic exposure for frequent users or those occupationally exposed.

High Exposure to Organophosphate Flame Retardants in Infants: Associations with Baby Products

Infant products containing polyurethane foam are commonly treated with organophosphate flame retardants (PFRs), including tris(1,3-dichloro-2-propyl)phosphate (TDCIPP) and triphenyl phosphate (TPHP). Infants may have greater exposure due to greater contact with these products, yet little is known about levels of exposure or the factors contributing to higher exposure. We recruited children age 2-18 months from North Carolina to investigate PFR exposure (n = 43; recruited 2014-2015). Parents provided information on potential sources and modifiers of exposure, and reported whether they owned common infant products. We measured five PFR metabolites in urine samples collected from children. TDCIPP and TPHP metabolites (bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) and diphenyl phosphate (DPHP)) were most commonly detected (>93% detect). Other metabolites were detected infrequently (<35% detect). Although we did not observe a clear age trend for infants, BDCIPP levels were substantially higher than those reported for adults (geometric mean = 7.3 ng/mL). The number of infant products owned was strongly associated with BDCIPP; children with >16 products had BDCIPP levels that were 6.8 times those with <13 (p = 0.02). Infants attending daycare centers also had higher BDCIPP levels (3.7 times those of others; p = 0.07), suggesting time spent in this microenvironment contributes to higher exposure. In contrast, DPHP levels were not related to products owned, time in different microenvironments, or behavior.

My Winding Road: From Microbiology to Toxicology and Environmental Health

I would certainly never have predicted that I would become the director of the National Institute of Environmental Health Sciences (NIEHS) and the National Toxicology Program (NTP) when I was a Jewish girl growing up in Teaneck, New Jersey. My family stressed the importance of education. Yet for a girl there were many not-so-subtle suggestions that the appropriate careers were in teaching or nursing, and the most important thing was to be a wife and mother. Well, I can't disagree with the latter, although I would have to add grandmother to that list of achievements. My parents were both college graduates, but my mom only taught high school English for one year before leaving the field to start our family. My dad returned from World War II and joined his brother in accounting. After my first sister was born, my father joined my mother's family jewelry business and helped to open a second retail store. My mother helped my dad out during the busy times—Christmas and wedding season—but otherwise focused on our growing family of three girls and one boy. This became increasingly challenging when it became clear that my little brother was severely retarded and would require extra care.

Developmental exposure to organophosphate flame retardants causes behavioral effects in larval and adult zebrafish

BACKGROUND

Organophosphate flame retardants (OPFRs) have grown in usage since concerns about the health effects of the previously used polybrominated flame retardants led to their being phased out. The potential for OPFRs to cause adverse health effects of their own is still unexamined. Because of their structural similarities to organophosphate pesticides, which have themselves been heavily researched and shown to be neurobehavioral teratogens, we investigated the possibility that developmental exposure to two OPFRs, triphenyl phosphate (TPHP), and tris(1,3-dichloroisopropyl)phosphate (TDCIPP) might lead to behavioral impairment across the lifespan, as has been observed with the organophosphate pesticide chlorpyrifos.

METHODS

Zebrafish were exposed to 0.03 or 0.3 μM of TPHP, TDCIPP, or chlorpyrifos from 0 to 5 days post fertilization. Vehicle control consisted of 0.03% solution of DMSO. At 6 days post fertilization, larvae were tested on a locomotor assay. Separate cohorts of 6 day old larvae that were not tested on the larval assay were allowed to grow to adulthood. At 12 weeks post fertilization, these adult zebrafish were tested on a battery of behavioral assays that included tests of novel environment exploration, startle habituation, social affiliation, and predator escape.

RESULTS

Developmental exposure altered zebrafish behavior across the lifespan. Larval zebrafish exposed to the 0.03 μM doses of chlorpyrifos or TDCIPP exhibited significant (p<0.05) hyperactivity in the locomotor assay. Organophosphate exposure significantly (p<0.05) altered the time course of adult zebrafish behavior in the novel environment, startle habituation, and social affiliation assays. Predator escape behavior was significantly (p<0.05) reduced in fish exposed to the 0.3 μM dose of TDCIPP. Exposure also caused hyperactivity in adult fish, with fish exposed to the 0.3 μM dose of TDCIPP exhibiting significantly (p<0.05) elevated locomotor behavior in the novel environment assay.

DISCUSSION

Early developmental exposure to OPFRs produced behavioral impairment that persisted into adulthood. These findings support broader research investigating the role of organophosphate compounds, including the OPFRs used here, in developmental neurotoxicity.

Triphenyl phosphate-induced developmental toxicity in zebrafish: potential role of the retinoic acid receptor

Using zebrafish as a model, we previously reported that developmental exposure to triphenyl phosphate (TPP) - a high-production volume organophosphate-based flame retardant - results in dioxin-like cardiac looping impairments that are independent of the aryl hydrocarbon receptor. Using a pharmacologic approach, the objective of this study was to investigate the potential role of retinoic acid receptor (RAR) - a nuclear receptor that regulates vertebrate heart morphogenesis - in mediating TPP-induced developmental toxicity in zebrafish. We first revealed that static exposure of zebrafish from 5-72h post-fertilization (hpf) to TPP in the presence of non-toxic concentrations of an RAR antagonist (BMS493) significantly enhanced TPP-induced toxicity (relative to TPP alone), even though identical non-toxic BMS493 concentrations mitigated retinoic acid (RA)-induced toxicity. BMS493-mediated enhancement of TPP toxicity was not a result of differential TPP uptake or metabolism, as internal embryonic doses of TPP and diphenyl phosphate (DPP) - a primary TPP metabolite - were not different in the presence or absence of BMS493. Using real-time PCR, we then quantified the relative change in expression of cytochrome P450 26a1 (cyp26a1) - a major target gene for RA-induced RAR activation in zebrafish - and found that RA and TPP exposure resulted in a ∼5-fold increase and decrease in cyp26a1 expression, respectively, relative to vehicle-exposed embryos. To address whether TPP may interact with human RARs, we then exposed Chinese hamster ovary cells stably transfected with chimeric human RARα-, RARβ-, or RARγ to TPP in the presence of RA, and found that TPP significantly inhibited RA-induced luciferase activity in a concentration-dependent manner. Overall, our findings suggest that zebrafish RARs may be involved in mediating TPP-induced developmental toxicity, a mechanism of action that may have relevance to humans.