Di(2-ethylhexyl) adipate (DEHA) is a plasticizer and phthalate substitute used in various consumer products. Relevant population exposures have to be assumed. In this study we describe the ...determination of three specific side chain-oxidized monoester metabolites of DEHA, mono-2-ethyl-5-hydroxyhexyl adipate (5OH-MEHA), mono-2-ethyl-5-oxohexyl adipate (5oxo-MEHA), and mono-5-carboxy-2-ethylpentyl adipate (5cx-MEPA) in human urine as potential biomarkers of DEHA exposure. After enzymatic hydrolysis, urine samples were analyzed by online turbulent flow chromatography for matrix depletion and analyte enrichment coupled to liquid chromatography-electrospray ionization-triple quadrupole-tandem mass spectrometry (online-SPE-LC-MS/MS). For quantification stable isotope dilution was applied with limits of quantification of 0.05 μg/L for 5cx-MEPA and 5OH-MEHA, and 0.1 μg/L for 5oxo-MEHA. Method accuracies (relative recoveries) were between 92 and 109%, and relative standard deviations <5%. We investigated the applicability of the method for internal DEHA exposure assessment in six volunteers who had consumed food wrapped in commercial PVC-cling film containing DEHA and in two small pilot populations without known DEHA exposure (44 pregnant Brazilian women and 32 German adults). In the cling film experiment, we could quantify all three metabolites in all post exposure urine samples, with 5cx-MEPA being most prominent (0.30–10.2 μg/L), followed by 5OH-MEHA (0.12–4.31 μg/L) and 5oxo-MEHA (0.12–2.84 μg/L). In the Brazilian and German samples we could detect DEHA exposures in 43 and 9% of all samples, again with 5cx-MEPA as the most prominent metabolite. Based on validation and pilot biomonitoring results, the method has proven appropriate for DEHA biomonitoring and will be applied in future metabolism and population studies.
•Determination of 3 specific urinary metabolites of the adipate plasticizer DEHA•LC-MS/MS coupled with online turbulent flow chromatography for sample clean-up•LOQs of 0.05–0.1 μg/L low enough to detect environmental background exposures•Metabolites quantifiable in 43% and 9% of samples from 2 pilot populations•Elevated levels after consumption of food wrapped in DEHA containing cling film
Octocrylene (OC) is a UV filter used in sun screens and other personal care products, but also in polymers and food contact materials for stabilization. In this study, we investigate human OC ...metabolism and urinary excretion after oral dosage of approx. 5 mg OC ≙ 61.8–89.5 µg/(kg body weight) in three male volunteers. In a screening approach, we tentatively identified six urinary OC metabolites. For three, renal elimination kinetics was quantitatively investigated using authentic standards: the sidechain oxidation product 2-ethyl-5-hydroxyhexyl 2-cyano-3,3-diphenyl acrylate (5OH–OC), the beta-oxidation product 2-(carboxymethyl)butyl 2-cyano-3,3-diphenyl acrylate (dinor OC carboxylic acid; DOCCA), and the ester hydrolysis product 2-cyano-3,3-diphenylacrylic acid (CPAA). CPAA was the major urinary metabolite, representing 45% (range 40–50%) of the OC dose. 5OH–OC and DOCCA were only minor metabolites with low, but highly consistent renal conversion factors of 0.008% (0.005–0.011%) and 0.13% (0.11–0.16%), respectively. Peak urinary metabolite concentrations were observed between 3.2 h and 4.2 h postdose. All three metabolites were excreted with biphasic elimination kinetics, with considerably longer elimination half-lives for DOCCA (1st phase: 3.0 h; 2nd phase: 16 h) and CPAA (5.7 h and 16 h) compared to 5OH–OC (1.3 h and 6.4 h). 99% of all 5OH–OC was excreted within 24 h compared to 82% of DOCCA and 77% of CPAA. After dermal exposure, we detected the same metabolites with similar ratios in urine, however, at much lower concentrations and with considerably delayed elimination.
Homosalate (HMS) is an organic UV filter used in sunscreens and personal care products worldwide. It has been detected in various environmental matrices and in humans after application of ...HMS-containing products. However, sufficient data on the internal HMS exposure in humans is currently not available. Thus, we aimed at providing an analytical method for the sensitive determination of specific HMS metabolites in human urine. We describe the synthesis of analytical standards for the four oxidative HMS metabolites included in this method: 5-((2-hydroxybenzoyl)oxy)-3,3-dimethylcyclohexane-1-carboxylic acid (HMS-CA) and 3-hydroxy-3,5,5-trimethylcyclohexyl 2-hydroxybenzoate (3OH-HMS), as cis- and trans-isomers, respectively. After enzymatic hydrolysis, urine samples were analyzed using liquid chromatography-electrospray ionization-triple quadrupole-tandem mass spectrometry, including turbulent flow chromatography for online sample cleanup and analyte enrichment (online-SPE-LC-MS/MS). Quantification was performed by stable isotope dilution analysis, using deuterium-labeled HMS-CA as internal standards (cis and trans). Limits of quantification of 0.02–0.04 μg L−1 were sufficiently low to quantify the HMS metabolites for up to 96 h (trans-HMS-CA), 48 h (cis-HMS-CA and 3OH-trans-HMS), and 24 h (3OH-cis-HMS) after a pilot dermal application of a commercially available sunscreen in one human volunteer, showing clear elimination kinetics. Furthermore, in a German pilot population (n = 35), HMS metabolites were above the LOQ precisely in those three individuals who had applied sunscreen within the previous five days, thus corroborating the specificity of the identified metabolites as biomarkers of HMS exposure. The method is currently used in a human metabolism study and will be applied in future population-scale human biomonitoring studies.
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•Four new metabolites of the UV filter homosalate are reported for the first time.•Custom syntheses of all analytical standards are described.•The analytical method allows resolution of further metabolite isomer peaks.•Limits of quantitation (LOQs) are in the range of 0.02–0.04 μg L−1.•The four metabolites can be quantified up to 24–96 h after single sunscreen use.
•Method modifications resulted in improved LOQs for glyphosate and AMPA (0.05 µg/L).•Use of polypropylene vials prevented adsorption of the analytes onto materials.•Different internal standard are ...less prone to mass spectrometric interference.•Representative median values found in a pilot population (n = 41).•Threefold increase in the frequency of samples with glyphosate above the LOQ.
Glyphosate is the highest volume herbicide used worldwide, and its main biodegradation product is aminomethylphosphonic acid (AMPA), both are listed as priority substances in the Human Biomonitoring for Europe (HBM4EU) initiative which aims at improving policy by filling knowledge gaps by targeted research. The objective of the current study was to advance the sensitivity of an existing gas chromatography-tandem mass spectrometry analytical method to measure environmental population exposures. A 50% lower limit of quantification of 0.05 µg/L was achieved for both analytes by slight modifications in sample work-up, and use of another isotope labelled internal standard. In a pilot study, 41 urine samples from the general German population were analysed, of which glyphosate and AMPA could be quantified in 66% and 90% of the samples respectively, which is sufficient to reliably describe distributions of urinary concentrations in the non-occupationally exposed population.
Sources of Variability in Biomarker Concentrations Aylward, Lesa L.; Hays, Sean M.; Smolders, Roel ...
Journal of toxicology and environmental health. Part B, Critical reviews,
01/2014, Letnik:
17, Številka:
1
Journal Article
Recenzirano
Human biomonitoring has become a primary tool for chemical exposure characterization in a wide variety of contexts: population monitoring and characterization at a national level, assessment and ...description of cohort exposures, and individual exposure assessments in the context of epidemiological research into potential adverse health effects of chemical exposures. The accurate use of biomonitoring as an exposure characterization tool requires understanding of factors, apart from external exposure level, that influence variation in biomarker concentrations. This review provides an overview of factors that might influence inter- and intraindividual variation in biomarker concentrations apart from external exposure magnitude. These factors include characteristics of the specific chemical of interest, characteristics of the likely route(s) and frequency of exposure, and physiological characteristics of the biomonitoring matrix (typically, blood or urine). Intraindividual variation in biomarker concentrations may be markedly affected by the relationship between the elimination half-life and the intervals between exposure events, as well as by variation in characteristics of the biomonitored media such as blood lipid content or urinary flow rate. Variation across individuals may occur due to differences in time of sampling relative to exposure events, physiological differences influencing urinary flow or creatinine excretion rates or blood characteristics, and interindividual differences in metabolic rate or other factors influencing the absorption or excretion rate of a compound. Awareness of these factors can assist researchers in improving the design and interpretation of biomonitoring studies.
Phthalates owing to their endocrine-disrupting effects are regulated in certain products, leading to their replacement with substitutions such as di-2-ethylhexyl terephthalate (DEHTP), ...1,2-cyclohexane dicarboxylic acid di(isononyl) ester (DINCH), and di(2-ethylhexyl) adipate (DEHA). However, information on human exposure to these substitutes, especially in susceptible subpopulations such as children, is limited. Thus, we examined the levels and exposure trends of DEHTP, DINCH, and DEHA metabolites in 7 year-old Japanese school children. In total, 180 urine samples collected from 2012 to 2017 were used to quantify 10 DEHTP, DINCH, and DEHA metabolites via isotope dilution liquid chromatography with tandem mass spectrometry. DEHTP and DINCH metabolites were detected in 95.6 and 92.2% of the children, respectively, and DEHA was not detected. This study, annually conducted between 2012 and 2017, revealed a significant (p < 0.05) 5-fold increase in DEHTP metabolites and a 2-fold increase in DINCH metabolites. However, the maximum estimated internal exposures were still below the health-based guidance and toxicological reference values. Exposure levels to DEHTP and DINCH have increased considerably in Japanese school children. DEHA is less relevant. Future studies are warranted to closely monitor the increasing trend in different aged and larger populations and identify the potential health effects and sources contributing to increasing exposure and intervene if necessary.
•We developed a LC–MS/MS method to quantify oxidized monoesters of DEHTP in urine.•Target analytes were chromatographically separated from DEHP metabolite analogues.•Urine samples of the general ...population were positively tested for target analytes.•Oxidized monoesters are promising biomarkers of exposure for human biomonitoring.
Di(2-ethylhexyl) terephthalate (DEHTP) is used as a substitute for ortho-phthalate based plasticizers like di(2-ethylhexyl) phthalate (DEHP) which are discussed and regulated due to their reproductive toxicity. We developed a fast and rugged method to quantify side chain oxidized monoesters of DEHTP in human urine, namely 5OH-MEHTP, 5oxo-MEHTP, 2cx-MMHTP and 5cx-MEPTP. Sample preparation was kept simple with enzymatic deconjugation and a two column assembly for on-line sample clean up. Metabolites were identified with authentic standards and quantified via isotope dilution LC–MS/MS. The limit of quantification was 0.2μg/L for 5cx-MEPTP and 5oxo-MEHTP, 0.3μg/L for 5OH-MEHTP and 0.4μg/L for 2cx-MMHTP. Accuracy (relative recovery: 95.8–111%) and precision (relative standard deviation: <7%) were highly acceptable. In a pilot biomonitoring study with 34 volunteers (aged 25–61 (median 42), 20 female and 14 male) not known to be occupationally exposed to DEHTP, we could detect 5cx-MEPTP above the limit of quantification in 94% of the samples (median: 0.9μg/L, maximum: 38.7μg/L). The other metabolites investigated were detected at a lower rate and at lower concentration levels (5oxo-MEHTP: 21%, maximum: 1.8μg/L; 5OH-MEHTP: 18%, maximum: 3.4μg/L; 2cx-MMHTP: 9%, maximum: 0.9μg/L). All target analytes can be regarded as promising and specific urinary biomarkers for DEHTP exposure. With this method we provide a basis for quantitatively investigating the human metabolism of DEHTP and for performing exposure and risk assessments in the general population and the working environment.
The population is constantly exposed to potentially harmful substances present in the environment, including inter alia food and drinking water, consumer products, and indoor air. Human biomonitoring ...(HBM) is a valuable tool to determine the integral, internal exposure of the general population, including vulnerable subgroups, to provide the basis for risk assessment and policy advice. The German HBM system comprises of five pillars: (1) the development of suitable analytical methods for new substances of concern, (2) cross-sectional population-representative German Environmental Surveys (GerES), (3) time trend analyses using archived samples from the Environmental Specimen Bank (ESB), (4) the derivation of health-based guidance values as a risk assessment tool, and (5) transfer of data into the European cooperation network HBM4EU. The goal of this paper is to present the complementary elements of the German HBM system and to show its strengths and limitations on the example of plasticizers. Plasticizers have been identified by EU services and HBM4EU partners as priority substances for chemical policy at EU level. Using the complementary elements of the German HBM system, the internal exposure to classical phthalates and novel alternative plasticizers can be reliably monitored. It is shown that market changes, due to regulation of certain phthalates and the rise of substitutes, are rapidly reflected in the internal exposure of the population. It was shown that exposure to DEHP, DiBP, DnBP, and BBzP decreased considerably, whereas exposure to the novel substitutes such as DPHP, DEHTP, and Hexamoll®DINCH has increased significantly. While health-based guidance values for several phthalates (esp. DnBP, DiBP, DEHP) were exceeded quite often at the turn of the millennium, exceedances today have become rarer. Still, also the latest GerES reveals the ubiquitous and concurrent exposures to many plasticizers. Of concern is that the youngest children showed the highest exposures to most of the investigated plasticizers and in some cases their levels of DiBP and DnBP still exceeded health-based guidance values. Over the last years, mixture exposures are increasingly recognized as relevant, especially if the toxicological modes of action are similar. This is supported by a cumulative risk assessment for four endocrine active phthalates which confirms the still concerning cumulative exposure in many young children. Given the adverse health effects of some phthalates and the limited toxicological knowledge of substitutes, exposure reduction and surveillance are needed on German and EU-level. Substitutes need to be monitored, to intervene if exposures are threatening to exceed acceptable levels, or if new toxicological data question their appropriateness. It is strongly recommended to reconsider the use of plastics and plasticizers.
•Presentation of the German HBM approach on the example of plasticizers.•10 phthalates or substitutes detectable in >97% of GerES V population.•Reduced exposure to regulated phthalates, increasing exposure to substitutes.•Highest exposure in the group of youngest children.•Cumulative exposure assessment reveals continued concern for young children.
Homosalate (HMS) is a UV filter used in sunscreens and personal care products as a mixture of
cis
- and
trans
-isomers. Systemic absorption after sunscreen use has been demonstrated in humans, and ...concerns have been raised about possible endocrine activity of HMS, making a general population exposure assessment desirable. In a previous study, it was shown that the oral bioavailability of
cis
-HMS (
c
HMS) is lower than that of
trans
-HMS (
t
HMS) by a factor of 10, calling for a separate evaluation of both isomers in exposure and risk assessment. The aim of the current study is the investigation of HMS toxicokinetics after dermal exposure. Four volunteers applied a commercial sunscreen containing 10% HMS to their whole body under regular-use conditions (18–40 mg HMS (kg bw)
−1
). Parent HMS isomers and hydroxylated and carboxylic acid metabolites were quantified using authentic standards and isotope dilution analysis. Further metabolites were investigated semi-quantitatively. Elimination was delayed and slower compared to the oral route, and terminal elimination half-times were around 24 h. After dermal exposure, the bioavailability of
c
HMS was a factor of 2 lower than that of
t
HMS. However, metabolite ratios in relation to the respective parent isomer were very similar to the oral route, supporting the applicability of the oral-route urinary excretion fractions for dermal-route exposure assessments. Exemplary calculations of intake doses showed margins of safety between 11 and 92 (depending on the approach) after single whole-body sunscreen application. Human biomonitoring can reliably quantify oral and dermal HMS exposures and support the monitoring of exposure reduction measures.
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