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Advanced oxidation kinetics of aqueous trialkyl phosphate flame retardants and plasticizers.

ABSTRACT: Trialkyl phosphate esters are a class of anthropogenic organics commonly found in surface waters of Europe and North America, due to their frequent application as flame retardants, plasticizers, and solvents. Four trialkyl phosphate esters were evaluated to determine second-order rates of reaction with ultraviolet- and ozone-generated *OH in water. Tris(2-butoxyethyl) phosphate (TBEP) was fastest to react with *OH (kOH,TBEP = 1.03 x 10(10) M(-1) s(-1)), followed sequentially by tributyl phosphate (TBP), tris(2-chloroethyl) phosphate (TCEP), and tris(2-chloroisopropyl) phosphate (TCPP) (kOH,TBP = 6.40 x 10(9), kOH,TCEP = 5.60 x 10(8), and kOH,TCPP = 1.98 x 10(8) M(-1) s(-1)). A two-stage process was used to test the validity of the determined kOH for TBEP and the fastest reacting halogenated alkyl phosphate, TCEP. First, *OH oxidation of TCEP and TBEP, in competition with nitrobenzene was measured in ozonated hydrogen peroxide solutions. Applying multiple regression analysis, it was determined that the UV/H2O2 and O3/H2O2 data sets were statistically identical for each compound. The subsequent validated kOH were used to predict TCEP and TBEP photodegradation in neutral pH, model surface water after chemical oxidant addition and UV irradiation (up to 1000 mJ/cm2). The insignificant difference between the predicted TBEP and TCEP photodegradation and a best-fit of the first-order exponential decay function to the observed TBEP and TCEP concentrations with increasing UV fluence was further evidence of the validity of the determined kOH. TBEP oxidation rates were similar in the surface waters tested. Substantial TCEP oxidation in the model surface water required a significant increase in initial H2O2.

SUBMITTER: Watts MJ

PROVIDER: S-EPMC3679666 | biostudies-literature | 2009 Apr

REPOSITORIES: biostudies-literature

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Advanced oxidation kinetics of aqueous trialkyl phosphate flame retardants and plasticizers.

Watts Michael J MJ Linden Karl G KG

Environmental science & technology 20090401 8

Trialkyl phosphate esters are a class of anthropogenic organics commonly found in surface waters of Europe and North America, due to their frequent application as flame retardants, plasticizers, and solvents. Four trialkyl phosphate esters were evaluated to determine second-order rates of reaction with ultraviolet- and ozone-generated *OH in water. Tris(2-butoxyethyl) phosphate (TBEP) was fastest to react with *OH (kOH,TBEP = 1.03 x 10(10) M(-1) s(-1)), followed sequentially by tributyl phosphat ...[more]

PMID: 19475974

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Project description:BACKGROUND:Following the phase-out of polybrominated diphenyl ethers (PBDEs), organophosphate esters (OPEs) have been increasingly used in consumer products and building materials for their flame retardant and plasticizing properties. As a result, human exposure to these chemicals is widespread as evidenced by common detection of their metabolites in urine. However, little is known about the major exposure pathways, or factors that influence children's exposure to OPEs. Furthermore, little data is available on exposure to the novel aryl OPEs. OBJECTIVES:To examine predictors of children's internal exposure, we assessed relationships between OPEs in house dust and on hand wipes and levels of their corresponding metabolites in paired urine samples (n?=?181). We also examined associations between urinary metabolites and potential covariates, including child's age and sex, mother's educational attainment and race, and average outdoor air temperature. METHODS:Children aged 3 to 6?years provided urine and hand wipe samples. Mothers or legal guardians completed questionnaires, and a house dust sample was taken from the main living area during home visits. Alkyl chlorinated and aryl OPEs were measured in dust and hand wipes, and composite urine samples were analyzed for several metabolites. RESULTS:Tris(2-chloroethyl) phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCIPP), tris(1,3-dichloro-2-propyl) phosphate (TDCIPP), 2-ethylhexyl diphenyl phosphate (EHDPHP), triphenyl phosphate (TPHP), and 2-isopropylphenyl diphenyl phosphate (2IPPDPP) were detected frequently in hand wipes and dust (>80%), indicating that these compounds were near-ubiquitous in indoor environments. Additionally, bis(1-chloro-2-propyl) 1-hydroxy-2-propyl phosphate (BCIPHIPP), bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), diphenyl phosphate (DPHP), mono-isopropyl phenyl phenyl phosphate (ip-PPP), and mono-tert-butyl phenyl phenyl phosphate (tb-PPP) were detected in >94% of tested urine samples, signifying that TESIE participants were widely exposed to OPEs. Contrary to PBDEs, house dust OPE concentrations were generally not correlated with urinary OPE metabolite levels; however, hand wipe levels of OPEs were associated with internal dose. For example, children with the highest mass of TDCIPP on hand wipes had BDCIPP levels that were 2.73 times those of participants with the lowest levels (95% CI: 1.67, 4.48, p?<?0.0001). Of the variables examined, hand wipe level was the most consistent and strongest predictor of OPE urinary metabolite concentrations. Outdoor air temperature was also a significant predictor of urinary BDCIPP concentrations, with a 1?°C increase in temperature corresponding to a 4% increase in urinary BDCIPP (p?<?0.0001). CONCLUSIONS:OPE exposures are highly prevalent, and data provided herein further substantiate hand-to-mouth contact and dermal absorption as important pathways of OPE exposure, especially for young children.

Project description:Chlorinated alkyl and non-chlorinated aryl organophosphate flame retardants (OPFRs) and some brominated flame retardants (FR) were introduced as replacements for polybrominated diphenyl ethers (PBDEs) after PBDEs phase-out in 2004 and 2013. Organophosphorous (OP) insecticides are mainly used in agricultural settings since the Food Quality Protection Act of 1996 phased-out most residential uses of OP insecticides in the United States. Urinary metabolites of FRs and OPs are known exposure biomarkers to FRs and OP insecticides, respectively. For large population-based studies, concurrent quantification of these metabolites using a small urine volume is desirable, but until now was not possible. We developed an analytical approach to quantify in 0.2?mL urine 10 FRs and six OP insecticide metabolites: diphenyl phosphate, bis(1,3-dichloro-2-propyl) phosphate, bis(1-chloro-2-propyl) phosphate, bis(2-chloroethyl) phosphate, dicresyl phosphates, dibutyl phosphate, dibenzyl phosphate, 2,3,4,5-tetrabromobenzoic acid, 2-((isopropyl)phenyl)phenyl phosphate, 4-((tert-butyl)phenyl)phenyl phosphate, dimethyl phosphate, diethyl phosphate, dimethyl thiophosphate, dimethyl dithiophosphate, diethyl thiophosphate, and diethyl dithiophosphate. The method relies on enzymatic deconjugation, automated off-line solid phase extraction, high-performance liquid chromatography, and isotope dilution tandem mass spectrometry. Detection limits ranged from 0.05 to 0.5?ng?mL-1, accuracy from 89 to 118%, and imprecision was <10%. . This method is the first to quantify simultaneously trace levels of 16 biomarkers of FRs and OP insecticides in only four drops of urine. We confirmed the method suitability for use in large epidemiological studies to assess background and occupational exposures to these classes of environmental pollutants by analyzing 303 samples collected from the general population and a group of firefighters. FR metabolite and DAPs concentrations in the general population group were lower than in the firefighters group, and within the ranges reported in the U.S. general population and other non-occupationally exposed populations.

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Advanced oxidation kinetics of aqueous trialkyl phosphate flame retardants and plasticizers.

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Advanced oxidation kinetics of aqueous trialkyl phosphate flame retardants and plasticizers.

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