Quantification of 16 urinary biomarkers of exposure to flame retardants, plasticizers, and organophosphate insecticides for biomonitoring studies

Exposure to organophosphate esters and early menopause: A population-based cross-sectional study

Organophosphate esters (OPEs), increasingly used as new flame retardants and plasticizers in various products, have been found to have reproductive toxicity with overt endocrine disruption potential, yet the relationship between OPEs and early menopause remains unexplored. In the present study, we included 2429 women who participated in the U.S. National Health and Nutrition Examination Survey data (2011-2020) and had data of five urinary OPE metabolite levels and information of menopause characteristics, to investigate the associations of OPEs exposure with premature ovarian insufficiency (POI) and age of menopause. Multivariable adjusted linear and logistic regression were used to assess the associations of urinary OPE metabolites with age of menopause and POI, respectively. Quantile g computation (QGC) models were used to assess the relative contribution of individual metabolites to associations of OPE metabolites mixture. After adjusting for covariates, urinary bis(2-chloroethyl) phosphate (BCEP) concentration was inversely associated with menopause age (β = - 0.21; 95% confidence interval (CI): 0.41, - 0.002). Higher urinary BCEP level (>median) was associated with earlier age at menopause (β = -1.14, 95% CI: 1.83, - 0.46), and elevated odds of having POI (OR = 1.93; 95% CI: 1.02, 3.66). These associations were robust to the further adjustment of cardiometabolic diseases and related traits (e.g., body mass index). Further QGC analyses confirmed that BCEP was the dominant metabolite contributing most to the associations of OPEs mixture with age of menopause (weight = 49.5%) and POI (weight = 75.1%). No significant associations were found for the other four OPE metabolites. In this cross-sectional study, urinary BCEP level was associated with earlier menopause and increased odds of POI, highlighting the potential negative impacts of this chemical and its parent compound tris(2-chloroethyl) phosphate on ovarian function. Further studies are required to validate our findings and reveal potential underlying mechanisms.

Gestational organophosphate esters (OPEs) and executive function in adolescence: The HOME Study

BACKGROUND

Evidence from toxicological studies indicate organophosphate esters (OPEs) are neurotoxic, but few epidemiological studies investigated associations between gestational OPEs and executive function.

OBJECTIVE

To examine the associations between gestational concentrations of OPE urinary metabolites and executive function at 12 years.

METHODS

We used data from 223 mother-adolescent dyads from the Health Outcomes of Measures of the Environment (HOME) Study. Women provided spot urine samples at 16 weeks gestation, 26 weeks gestation, and at delivery for quantification of bis(1,3-dichloro-2-propyl) phosphate, bis-2-chloroethyl phosphate (BCEP), diphenyl phosphate (DPHP), and di-n-butyl phosphate (DNBP). Executive function was assessed at age 12 years using the parent- and self-report Behavior Rating Inventory of Executive Function (BRIEF2). Covariate-adjusted associations between specific gravity-corrected OPEs and BRIEF2 scores were estimated using multiple informant models. Bayesian Kernel Machine Regression (BKMR) was used to assess the impact of all OPEs simultaneously.

RESULTS

Parent- and self-report BRIEF2 indices and composite scores were weakly to moderately correlated (rs = 0.32-0.41). A natural-log unit increase in BCEP at 26 weeks was associated with approximately a 1-point increase on the self-report Cognitive Regulation Index [CRI] (95% CI 0.4, 2.3), the Emotion Regulation Index [ERI] (95% CI 0.3, 2.2), and the Global Executive Composite [GEC] (95% CI 0.4, 2.2), indicating poorer performance. Higher DPHP at 16 weeks was associated with lower parent-report GEC score (β = -1.1, 95% CI -2.3, -0.003). BKMR identified BCEP and DNBP at 26 weeks as important contributors to CRI and ERI, respectively.

CONCLUSION

OPE metabolites during gestational development, particularly BCEP, may influence adolescent executive function. However, since the FDR p-values failed to reach statistical significance, additional studies would benefit from using larger cohorts.

Serum albumin and liver dysfunction mediate the associations between organophosphorus pesticide exposure and hypertension among US adults

BACKGROUND

Human health is commonly threatened by organophosphorus pesticides (OPPs) due to their widespread use and biological characteristics. However, the combined effect of mixtures of OPPs metabolites on the risk of hypertension and potential mechanism remain limited.

OBJECTIVES

To comprehensively investigate the effects between OPPs exposure on hypertension risk and explore and underlying mechanism among US general population.

METHODS

This cross-sectional study collected US adults who had available data on urine OPPs metabolites (dialkyl phosphate compounds, DAPs) from the National Health and Nutrition Examination Survey (NHANES) to assess the relationships of DAPs with hypertension risk. Survey-weighted logistic regression, restricted cubic spline (RCS), and mixed exposure analysis models [weighted quantile sum regression (WQS) and Bayesian kernel machine regression (BKMR)] were used to analyze individual, dose-response and combined associations between urinary DAPs metabolites and hypertension risk, respectively. Mediation analysis determined the potential intermediary role of serum albumin and liver function in the above associations.

RESULTS

Compared with the reference group, participants with the highest tertile levels of DEP, DMTP, DETP, and DMDTP experienced increased risk of hypertension by 1.21-fold (95%CI: 1.02-1.36), 1.20-fold (95%CI: 1.02-1.42), 1.19-fold (95%CI: 1.01-1.40), and 1.17-fold (95%CI: 1.03-1.43), respectively. RCS curve also showed positive exposure-response associations of individual DAPs with hypertension risk. WQS and BKMR analysis further confirmed DAP mixtures were significantly associated with increased risk of hypertension, with DEP identified as a major contributor to the combined effect. Mediation analysis indicated that serum albumin and AST/ALT ratios played crucial mediating roles in the relationships between individual and mixed urinary DAPs and the prevalence of hypertension.

CONCLUSION

Our findings provided more comprehensive and novel perspectives into the individual and combined effects of urinary OPPs matabolites on the increased risk of hypertension and the possible driving mechanism, which would be of great significance for environmental control and early prevention of hypertension.

Metabolomics and proteomics in occupational medicine: a comprehensive systematic review

BACKGROUND

Occupational biomonitoring is essential for assessing health risks linked to workplace exposures. The use of 'omics' technologies, such as metabolomics and proteomics, has become crucial in detecting subtle biological alterations induced by occupational hazards, thereby opening novel avenues for biomarker discovery.

AIMS

This systematic review aims to evaluate the application of metabolomics and proteomics in occupational health.

METHODS

Following the PRISMA guidelines, we conducted a comprehensive search on PubMed, Scopus, and Web of Science for original human studies that use metabolomics or proteomics to assess occupational exposure biomarkers. The risk of bias was assessed by adapting the Cochrane Collaboration tool and the Newcastle-Ottawa Quality Assessment Scale.

RESULTS

Of 2311 initially identified articles, 85 met the eligibility criteria. These studies were mainly conducted in China, Europe, and the United States of America, covering a wide range of occupational exposures. The findings revealed that metabolomics and proteomics approaches effectively identified biomarkers related to chemical, physical, biomechanical, and psychosocial hazards. Analytical methods varied, with mass spectrometry-based techniques emerging as the most prevalent. The risk of bias was generally low to moderate, with specific concerns about exposure measurement and confounding factors.

CONCLUSIONS

Integrating metabolomics and proteomics in occupational health biomonitoring significantly advances our understanding of exposure effects and facilitates the development of personalized preventive interventions. However, challenges remain regarding the complexity of data analysis, biomarker specificity, and the translation of findings into preventive measures. Future research should focus on longitudinal studies and biomarker validation across diverse populations to improve the reliability and applicability of occupational health interventions.

Breast Cancer-Related Chemical Exposures in Firefighters

To fill a research gap on firefighter exposures and breast cancer risk, and guide exposure reduction, we aimed to identify firefighter occupational exposures linked to breast cancer. We conducted a systematic search and review to identify firefighter chemical exposures and then identified the subset that was associated with breast cancer. To do this, we compared the firefighter exposures with chemicals that have been shown to increase breast cancer risk in epidemiological studies or increase mammary gland tumors in experimental toxicology studies. For each exposure, we assigned a strength of evidence for the association with firefighter occupation and for the association with breast cancer risk. We identified twelve chemicals or chemical groups that were both linked to breast cancer and were firefighter occupational exposures, including polycyclic aromatic hydrocarbons, volatile aromatics, per- and polyfluoroalkyl substances, persistent organohalogens, and halogenated organophosphate flame retardants. Many of these were found at elevated levels in firefighting environments and were statistically significantly higher in firefighters after firefighting or when compared to the general population. Common exposure sources included combustion byproducts, diesel fuel and exhaust, firefighting foams, and flame retardants. Our findings highlight breast-cancer-related chemical exposures in the firefighting profession to guide equitable worker's compensation policies and exposure reduction.

Potential mechanisms and modifications of dietary antioxidants on the associations between co-exposure to plastic additives and diabetes

BACKGROUND

The association of plastic additive mixture exposure with diabetes and the modifying effects of dietary antioxidants are unclear.

METHODS

The data from the NHANES 2011-2018 were retrieved, and phthalates and organophosphate esters (OPEs) were selected as exposures. The coexposure effect was analyzed by the environmental risk score (ERS) and quantile g-computation. To mitigate any potential bias caused by using the internal weights, another version of ERS was constructed using the cross-validation approach. The level of dietary antioxidant intake was measured by the composite dietary antioxidant index (CDAI). The biological mechanism underlying the association was studied by the adverse outcome pathway (AOP) framework.

RESULTS

Fifteen chemicals (ten phthalates and five OPEs) were measured in 2824 adult participants. A higher ERS was significantly associated with an increased risk of diabetes (OR per 1-SD increment of ERS: 1.25, 95% CI: 1.13-1.39). This association apparently interacted with the CDAI level (ORlow: 1.83, 95% CI: 1.37-2.55; ORhigh: 1.28, 95% CI: 1.15-1.45; Pinteraction = 0.038). Moreover, quantile g-computation also revealed higher level of combined exposure was positively associated with diabetes (OR: 1.27, 95% CI: 1.05-2.87), and the addition of dietary antioxidants showed a null association (OR: 1.09, 95% CI: 0.85-2.34). The AOP study identified TCPP and TCEP as key chemicals that cause aberrant glucose metabolism and insulin signaling pathways and result in diabetes.

CONCLUSIONS

Coexposure to phthalates and OPEs is positively associated with diabetes, where an antioxidative diet plays a modifying role. Several potential mechanisms have been proposed by AOP framework.

Urinary Concentrations of Organophosphate Flame-Retardant Metabolites in the US Population

Importance

Organophosphate flame retardants (OPFRs) are an important group of pollutants associated with endocrine disorders, cancer, and nephrotoxicity. However, temporal trends in OPFR metabolite concentrations remain understudied.

Objectives

To examine changes in urinary concentrations of OPFR metabolites among US children, youths, and adults from 2011 to 2020, and to evaluate whether sociodemographic factors were associated with variations in temporal trends.

Design, Setting, and Participants

This population-based cross-sectional study used data from 4 US National Health and Nutrition Examination Survey (NHANES) cycles (2011-2012, 2013-2014, 2015-2016, and 2017-2020 [to March 2020 before the COVID-19 pandemic]). The study included children and youths (aged 6-19 years) and adults (aged ≥20 years) with valid urinary concentrations of the following OPFR metabolites: bis(2-chloroethyl) phosphate (BCEtP), bis(1-chloro-2-propyl) phosphate (BCPP), diphenyl phosphate (DPhP), and dibutyl phosphate (DBuP). Data analysis was performed between February and May 2024.

Exposures

Calendar year and key sociodemographic subgroups (age, race and ethnicity, sex, educational attainment, and poverty-to-income ratio).

Main Outcomes and Measures

The main outcome was urinary concentrations of OPFR metabolites among children, youths, and adults. Survey-weighted linear regression models were applied to estimate trends.

Results

The study population of 10 549 NHANES participants included 3154 children and youths (mean [SE] age, 12.5 [0.1] years; 51.2% were male) and 7395 adults (mean [SE] age, 47.8 [0.4] years; 52.0% were women). Among children and youths, mean (95% CI) BCEtP concentrations decreased from 0.68 (0.60-0.77) μg/L in 2011-2012 to 0.41 (0.37-0.45) μg/L in 2017-2020 (P for trend < .001). Among adults, mean (95% CI) BCEtP concentrations decreased from 0.43 (0.37-0.50) μg/L in 2011-2012 to 0.29 (0.27-0.33) μg/L in 2017-2020 (P for trend < .001), and mean BCPP concentrations decreased from 0.15 (0.14-0.17) μg/L to 0.13 (0.12-0.14) μg/L (P for trend = .002). Parent level of educational attainment was associated with concentrations of BCPP and BCEtP among children and youths; however, no significant differences among adults were observed.

Conclusions and Relevance

This study identified variations in temporal trends in urinary concentrations of OPFR metabolites among the US population from 2011 to 2020. In addition, substantial disparities in exposure levels persisted among children with different levels of parent educational attainment. These findings suggest that policy makers should consider socioeconomic factors to further reduce OPFR exposure and promote equity, ensuring a safe living environment for all individuals.

Exposure to organophosphate ester flame retardants and plasticizers and associations with preeclampsia and blood pressure in pregnancy

BACKGROUND

Organophosphate esters (OPEs), flame retardants and plasticizers found widely in consumer products, may impact vascularization processes in pregnancy. Yet, the association between maternal exposure to OPEs and both preeclampsia and blood pressure during pregnancy remains understudied.

METHODS

Within the LIFECODES Fetal Growth Study (N = 900), we quantified 8 OPE metabolites from maternal urine collected at up to 3 time points during pregnancy and created within-subject geometric means. Outcomes included diagnosis of preeclampsia and longitudinal systolic (SBP) and diastolic (DBP) blood pressure measurements (mean = 14 per participant). Cox proportional hazards models were used to estimate associations between OPE metabolites and preeclampsia. Associations between average OPE metabolite concentrations and repeated blood pressure measurements were estimated using generalized estimating equations.

RESULTS

Five OPE metabolites were detected in at least 60% of samples; 3 metabolites detected less frequently (5-39%) were examined in an exploratory analysis as ever vs. never detectable in pregnancy. There were 46 cases of preeclampsia in our study population. Associations between OPE metabolites and preeclampsia were null. We noted several divergent associations between OPE metabolites and longitudinal blood pressure measurements. An interquartile range (IQR) difference in average bis(2-chloroethyl) phosphate concentrations was associated with a decrease in SBP (-0.81 mmHg, 95% confidence interval [CI]: -1.62, 0.00), and, conversely, bis(1-chloro-2-propyl) phosphate was associated with a slight increase in SBP (0.94 mmHg, 95% CI: 0.28, 1.61). We also noted a decrease in SBP in association with several metabolites with low detection frequency.

CONCLUSIONS

We observed null associations between OPE metabolites and preeclampsia, but some positive and some inverse associations with blood pressure in pregnancy. While our study was well-designed to assess associations with blood pressure, future studies with a larger number of preeclampsia cases may be better poised to investigate the association between OPE metabolites and phenotypes of this heterogenous hypertensive disorder of pregnancy.

A randomized controlled trial of a housing intervention to reduce endocrine disrupting chemical exposures in children

Few studies have considered household interventions for reducing endocrine disrupting chemical (EDC) exposures. We conducted a secondary analysis of a randomized controlled trial, originally designed to reduce lead exposure, to evaluate if the intervention lowered EDC exposures in young children. Study participants were children from the Cincinnati, Ohio area (n = 250, HOME Study). Prenatally, families received a housing intervention that included paint stabilization and dust mitigation, or as a control, injury prevention measures. At 24-months, we measured organophosphate esters (OPEs) and phthalates or their metabolites in dust and urine. We measured perfluoroalkyl substances (PFAS) in dust and serum at 24- and 36-months, respectively. We assessed associations between dust and biomarker EDCs using Spearman correlations, characterized EDC mixtures via principal components analysis, and investigated treatment effects using linear regression. To mitigate selection bias, we fit statistical models using inverse probability of retention weights. Correlations between dust EDCs and analogous biomarkers were weak-to-moderate (ρ's ≤ 0.3). The intervention was associated with 23 % (95 % CI: -38, -3) lower urinary DEHP metabolites and, in a per-protocol analysis, 34 % lower (95 % CI: -55, -2) urinary MBZP. Additionally, among Black or African American children, the intervention was associated with lower serum concentrations of several PFAS (e.g., -42 %; 95 % CI: -63, -8 for PFNA). Household interventions that include paint stabilization and dust mitigation may reduce childhood exposures to some phthalates and PFAS in Blacks/African Americans. These findings highlight the need for larger studies with tailored and sustained housing interventions.

Organophosphate Ester Flame Retardants and Plasticizers in Relation to Fetal Growth in the LIFECODES Fetal Growth Study

BACKGROUND

Organophosphate esters (OPEs), used ubiquitously as flame retardants and plasticizers in consumer products, are suspected of having developmental toxicity.

OBJECTIVES

Our study aimed to estimate associations between prenatal exposure to OPEs and fetal growth, including both ultrasound (head circumference, abdominal circumference, femur length, and estimated fetal weight) and delivery [birth weight z-score, small-for-gestational age (SGA), and large-for-gestational age (LGA)] measures of growth.

METHODS

In the LIFECODES Fetal Growth Study (2008-2018), an enriched case-cohort of 900 babies born at the small and large ends of the growth spectrum, we quantified OPE biomarkers in three urine samples per pregnant participant and abstracted ultrasound and delivery measures of fetal growth from medical records. We estimated associations between pregnancy-averaged log-transformed OPE biomarkers and repeated ultrasound measures of fetal growth using linear mixed-effects models, and delivery measures of fetal growth using linear (birth weight) and logistic (SGA and LGA) regression models.

RESULTS

Most OPE biomarkers were positively associated with at least one ultrasound measure of fetal growth, but associations with delivery measures were largely null. For example, an interquartile range (IQR; 1.31  ng / mL ) increase in bis(2-chloroethyl) phosphate concentration was associated with larger z-scores in head circumference [mean difference (difference): 0.09; 95% confidence interval (CI): 0.01, 0.17], abdominal circumference (difference: 0.10; 95% CI: 0.02, 0.18), femur length (difference: 0.11; 95% CI: 0.03, 0.19), and estimated fetal weight (difference: 0.13; 95% CI: 0.04, 0.22) but not birth weight (difference: 0.04; 95% CI: - 0.08 , 0.17). At delivery, an IQR (1.00  ng / mL ) increase in diphenyl phosphate (DPHP) concentration was associated with an SGA birth (odds ratio: 1.46; 95% CI: 1.10, 1.94).

CONCLUSIONS

In a large prospective cohort, gestational OPE exposures were associated with larger fetal size during pregnancy, but associations at delivery were null. DPHP concentrations were associated with heightened risk of an SGA birth. These findings suggest that OPE exposure may affect fetal development. https://doi.org/10.1289/EHP14647.

Determination of pesticide residues in urine by chromatography-mass spectrometry: methods and applications

Introduction

Pollution has emerged as a significant threat to humanity, necessitating a thorough evaluation of its impacts. As a result, various methods for human biomonitoring have been proposed as vital tools for assessing, managing, and mitigating exposure risks. Among these methods, urine stands out as the most commonly analyzed biological sample and the primary matrix for biomonitoring studies.

Objectives

This review concentrates on exploring the literature concerning residual pesticide determination in urine, utilizing liquid and gas chromatography coupled with mass spectrometry, and its practical applications.

Method

The examination focused on methods developed since 2010. Additionally, applications reported between 2015 and 2022 were thoroughly reviewed, utilizing Web of Science as a primary resource.

Synthesis

Recent advancements in chromatography-mass spectrometry technology have significantly enhanced the development of multi-residue methods. These determinations are now capable of simultaneously detecting numerous pesticide residues from various chemical and use classes. Furthermore, these methods encompass analytes from a variety of environmental contaminants, offering a comprehensive approach to biomonitoring. These methodologies have been employed across diverse perspectives, including toxicological studies, assessing pesticide exposure in the general population, occupational exposure among farmers, pest control workers, horticulturists, and florists, as well as investigating consequences during pregnancy and childhood, neurodevelopmental impacts, and reproductive disorders.

Future directions

Such strategies were essential in examining the health risks associated with exposure to complex mixtures, including pesticides and other relevant compounds, thereby painting a broader and more accurate picture of human exposure. Moreover, the implementation of integrated strategies, involving international research initiatives and biomonitoring programs, is crucial to optimize resource utilization, enhancing efficiency in health risk assessment.

Identification of potential chemical biomarkers of hexaconazole using in vitro metabolite profiling in rat and human liver microsomes and in vivo confirmation through urinary excretion study in rats

Hexaconazole (HEX) is an azole fungicide widely used in agricultural practices across various countries and numerous studies have reported the toxic effects of HEX, such as endocrine disruption, immunotoxicity, neurotoxicity and carcinogenicity. Despite its widespread agricultural use and toxic effects, the metabolism of HEX is not completely understood, and information on urinary elimination of HEX or its metabolites is limited. Therefore, in the present study, we aimed to identify HEX metabolites in rat and human liver microsomes followed by their in vivo confirmation using a urinary excretion study in rats to identify potential candidate for exposure biomarkers for human biomonitoring studies. From the in vitro assay, a total of 12 metabolites were observed, where the single oxidation metabolites (M5 and M6) were the most abundant metabolites in both rat and human liver microsomes. The triple oxidation followed by dehydration metabolite, M8 (which could also be hexaconazole acid or hydroxy keto-hexaconazole), and the double oxidation metabolite (M9) were the major metabolites found in rat urine and were detectable in rat urine longer than the parent. These metabolites increased with decreasing concentrations of HEX in the rat urine samples. Therefore, metabolites M8, M9 and M5 could be pursued further as potential biomarkers for assessing and monitoring human exposure to HEX.

Determinants of urinary dialkyl phosphate metabolites in midlife women: the Study of Women's Health Across the Nation Multi-Pollutant Study (SWAN-MPS)

BACKGROUND

Biomonitoring data and determinants of urinary dialkylphosphate (DAP) metabolites, markers of organophosphate pesticides, in racially diverse, non-occupationally exposed populations are scarce.

OBJECTIVE

This study evaluated urinary concentrations and potential determinants of DAP metabolites of organophosphate pesticides in a multi-site, multi-racial/ethnic cohort of women aged 45-56 years, the Study of Women's Health Across the Nation Multi-Pollutant Study (SWAN-MPS).

METHODS

We analyzed 963 urine samples collected in 1999-2000, the baseline of SWAN-MPS for longitudinal studies, and quantified DAP metabolites, including dimethyl alkylphosphates (DMAPs): dimethylphosphate (DMP), dimethylthiophosphate (DMTP), dimethyldithiophosphate (DMDTP); and diethyl alkylphosphates (DEAPs): diethylphosphate (DEP), diethylthiophosphate (DETP), diethyldithiophosphate (DEDTP), using gas chromatography and triple quadrupole mass spectroscopy. Adjusted least squared geometric means (LSGMs) and 95% confidence intervals (CIs) were computed to compare DAP concentrations by socio-demographic, behavioral and dietary factors.

RESULTS

The geometric means (geometric standard deviations) of total DAPs, DMAPs, and DEAPs were 141 (2.63) nmol/L, 102 (2.99) nmol/L, and 26.8 (2.46) nmol/L, respectively. Body mass index (BMI) was inversely associated with DMAPs and DEAPs: LSGM (95% CI) = 68.8 (55.7-84.9) and 21.0 (17.7-25.0) nmol/L for women with obesity vs. 102 (84.7-123) and 30.1 (25.7-35.1) nmol/L for women with normal/underweight, respectively. Fruit consumption was positively (74.9 (62.1-90.2) for less than 5-6 servings/week vs. 105 (84.8-130) nmol/L for 1 serving/day and more) whereas meat consumption was inversely associated with DMAPs (110 (95.0-128) for seldom vs. 82.3 (59.5-114) nmol/L for often consumption). Fresh apple consumption appears to be attributed to the DMAP differences. Alcohol consumption was positively associated with DEAPs (27.5 (23.1-32.7) for 2 drinks/week and more vs. 23.0 (20.0-26.6) nmol/L for less than 1 drink/month). Black women had higher concentrations of DEAPs compared with White women (27.3 (21.2-35.2) vs. 23.2 (20.2-26.7) nmol/L).

IMPACT STATEMENT

Organophosphate pesticides (OPs) are synthetic chemicals and currently the most widely used type of insecticides. We examined multi-site, multi-ethnic cohort of midlife women in the U.S. that offers a unique opportunity to evaluate major determinants of OP exposure. We improved OP metabolite detection rates and obtained accurate concentrations using an improved analytical technique. Our findings suggest that consumptions of fruit, meat and alcohol are important determinants of OP exposure for midlife women. Higher concentrations of diethyl OP metabolites in Black women compared to White women, even after accounting for dietary intake, suggests additional, but unknown racial-ethnic differences that affect exposure.

Investigation of Urinary Metabolites of Organophosphate Esters in Hanoi, Vietnam: Assessment Exposure and Estimated Daily Intake

In recent years, organophosphate esters (OPEs) have become one of the most common additives in various consumer products worldwide, therefore the exposure and impact of OPEs on human health are drawing a lot of attention. In this study, three metabolites of OPEs including bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), diphenyl phosphate (DPhP) and diethyl phosphate (DEP) were investigated in first-morning void urine samples taken from a population (age range: 3-76 years old) in Hanoi, Vietnam. The most dominant urinary OPE metabolite was DEP with the geometric mean of specific gravity adjust (SG-adjusted) concentration were 1960 ng mL-1 and detected frequency (DF) of 98%. Followed by DPhP (8.01 ng mL-1, DF: 100%) and BDCIPP (2.18 ng mL-1, DF: 51%). The results indicated that gender and age might have associations with the OPE metabolites variation in urine samples. The levels of OPE metabolites in urine samples from females were slightly higher than in males. An increase in age seems to have an association with a decrease in DPhP levels in urine. Exposure doses of parent OPEs were evaluated from the unadjusted urinary concentration of corresponding OPE metabolite. The estimated exposure doses of triethyl phosphate (TEP) (mean: 534,000 ng kg-1 d-1) were significantly higher than its corresponding reference dose, suggesting the high potential risk from the current exposure doses of TEP to human health. The results of this work provided the initial information on the occurrence of three OPE metabolites in urine from Hanoi, Vietnam and estimated exposure dose of corresponding parent OPEs.

Single injection by LC-ESI-MS/MS for simultaneous determination of organophosphate tri- and di-esters in plant tissue based on ultrasonic-assisted sequential extraction and single-step purification

A novel methodology based on ultrasonic-assisted sequential extraction, dispersive-SPE purification, and single-injection on liquid chromatography-tandem mass spectrometry (LC-MS/MS) is proposed, for the first time, to simultaneously measure 14 tri-OPEs and 9 di-OPEs in plant tissues. The samples were successively ultrasonicated with a mixture of hexane:dichloromethane (1:1, v/v) and 8% acetic acid in acetonitrile for extracting tri- and di-OPEs purified with graphitized carbon black and quantitated on LC-MS/MS at the same time. The recoveries of targeted tri- and di-OPEs in the matrix spike ranged from 66% to 120% and 71% to 110% respectively. The proposed method was validated by processing eight types of common vegetables including spinach (Spinacia oleracea L.), lettuce (Lactuca sativa), carrot (Daucus carota var. sativa Hoffm.), sweet potato (Solanum tuberosum L.), cucumber (Cucumis sativus L.), tomato (Solanum lycopersicum L.), green beans (Phaseolus vulgaris), and cowpeas (Vigna unguiculata), with the recoveries of surrogates ranging from 84% to 98%.

Evaluation of multiple organophosphate insecticide exposure in relation to altered thyroid hormones in NHANES 2007-2008 adult population

The thyroid gland is susceptible to chemical exposure such as organophosphate insecticides (OPIs). With the ubiquitous nature of these products, humans are simultaneously exposed to a multitude of chemicals. This study aimed to evaluate the association between an individual and a mixture of OPI metabolites and changes in serum thyroid hormone (TH) concentrations. The analyzed data were 1,434 participants from the United States National Health and Nutrition Examination Surveys (NHANES) cycle 2007-2008. Generalized linear model (GLM) regression, weighted quantile sum (WQS), and adaptive least absolute shrinkage and selection operator (adaptive LASSO) regression were used to investigate the associations between urinary OPI metabolites and altered serum THs. In GLM, all of the five urinary OPI metabolites were inversely associated with free triiodothyronine (FT3) among the male subjects; meanwhile, higher thyroglobulin (Tg) was related to dimethylphosphate (DMP). Moreover, in WQS models, the metabolite mixture induced FT3 down-regulation (β = -0.209 (95% CI: -0.310, -0.114)), and caused an increased Tg concentration (β = 0.120 (95% CI: 0.024, 0.212)), however, any significant association was observed among female participants. Consistently, the weighted index and LASSO coefficient demonstrated dimethylthiophosphate (DMTP) as the strongest metabolite in the FT3 model (mean weight= 3.449e-01 and β =-0.022, respectively), and dimethylphosphate (DMP) represented the highest association in the Tg model (mean weight= 9.873e-01 and β =-0.020, respectively). Further research is required to confirm our results and investigate the clinical impacts of these disruptions.

Patterns of urinary organophosphate ester metabolite trajectories in children: the HOME Study

BACKGROUND

Organophosphate esters (OPEs) have replaced flame retardant polybrominated diphenyl ethers as flame retardants in consumer products, but few longitudinal studies have characterized childhood OPE exposure.

OBJECTIVE

We aimed to examine the exposure pattern of urinary OPE metabolites in children.

METHODS

We quantified three urinary OPE metabolites five times in children (1, 2, 3, 5, 8 years) from 312 mother-child pairs in the Health Outcomes and Measures of the Environment (HOME) Study, a prospective pregnancy and birth cohort in Cincinnati, Ohio, USA. We examined the associations of average maternal OPE metabolite concentrations with OPE metabolite concentrations in childhood, characterized childhood OPE trajectories with latent class growth analysis (LCGA), and examined factors related to trajectory membership.

RESULTS

Bis(2-chloroethyl) phosphate (BCEP) had the lowest median concentrations over time (0.66-0.97 mg/L) while the median concentrations of bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) increased with age (1.44-3.80 mg/L). The median concentrations of diphenyl phosphate (DPHP) fluctuated between 1.96 and 2.69 mg/L. Intraclass correlation coefficients for urinary metabolites measured at five time points indicated high variability within individuals (0.13-0.24). Average maternal urinary BCEP and BDCIPP were associated with concentrations in early childhood. Maternal education, the birth year of the child, and having a carpet in the main activity room were associated with BCEP and BDCIPP trajectory while none of the factors were associated with DPHP trajectory.

SIGNIFICANCE

The trajectory analysis showed different patterns of urinary OPE metabolite concentrations, suggesting the need to collect multiple samples to adequately reflect OPE exposure.

IMPACT STATEMENT

In this well-established cohort, we evaluated the patterns of urinary OPE metabolites in children ages 1-8 years. The number of repeated measures over childhood has not been achieved in prior studies. Our results suggested the high variability of urinary OPE metabolites within individuals. Maternal metabolite concentrations during pregnancy were related to child concentrations at ages 1-3 years. BCEP, BDCIPP, and DPHP demonstrated different trajectories in children, which suggests that multiple samples may be required to capture OPE exposure patterns in childhood.

Exposure to OPFRs Is Associated with Obesity and Dysregulated Serum Lipid Profiles: Data from 2017-2018 NHANES

Widespread exposure to organophosphorus flame retardants (OPFRs) has been observed in the general population. Emerging studies have revealed OPFRs possess endocrine-disturbing properties. The present study aims to assess the association between urinary metabolites of OPFRs, BMI, and serum lipid profiles. Data from the National Health and Nutrition Examination Survey (NHANES) 2017-2018 were obtained, with 1334 adults enrolled in the current study. Urinary concentrations of bis (1-chloro-2-propyl) phosphate (BCIPP), bis(2-chloroethyl) phosphate (BCEP), bis(1,3-dichloro-2-propyl) phosphate (BDCPP), dibutyl phosphate (DBUP), and diphenyl phosphate (DPHP) were quantified to assess OPFR exposure. Covariate-adjusted linear and logistic regression models were conducted to explore the associations between log2-transformed concentrations of OPFR metabolites, BMI, obesity, and serum lipid profiles. Stratified analyses were performed to assess the heterogeneity of associations by age, gender, race, etc. Positive associations were found between OPFR exposure and the risk of obesity. The multivariate linear analysis indicated that a one-unit increase in log2-transformed urinary concentrations of BCEP and BDCPP was associated with 0.27 (95% CI: 0.02-0.52, p = 0.0338) and 0.56 (95% CI: 0.25-0.87, p = 0.0004) higher BMI value, respectively. One log2-unit increase in urinary BCEP and BDCPP concentrations was associated with 1.1-fold (95% CI: 1.02-1.18, p = 0.0096) and 1.19-fold (95% CI: 1.09-1.30, p = 0.0001) risk for developing obesity. Furthermore, the non-linear relationship between exposure to OPFRs and obesity was identified. Additionally, multivariable linear regression showed that urinary DPHP concentrations were inversely correlated with serum triglyceride (TG) levels (β = -7.41, 95% CI: -12.13 to -2.68, p = 0.0022). However, no other OPFR metabolites were found to be significantly statistically associated with serum lipid levels after adjusting for potential confounders. In conclusion, environmental exposure to OPFRs might contribute to obesity and dysregulated TG concentrations in adults. Future prospective research is warranted to confirm the causal relationship between metabolites of OPFRs and obesity.

Prenatal exposure to replacement flame retardants and organophosphate esters and childhood adverse respiratory outcomes

BACKGROUND

The association of prenatal exposure to organophosphate esters (OPEs) and replacement brominated flame retardants (RBFRs) with respiratory outcomes has not been previously investigated in humans, despite reports that these chemicals can cross the placenta and alter lung development as well as immune functions.

METHODS

In a cohort of 342 pregnant women recruited between 2003 and 2006 in the greater Cincinnati, Ohio Metropolitan area, we measured indoor dust OPEs and RBFRs at 20 weeks of gestation and urinary OPEs at 16 and 26 weeks of gestation and at delivery. We performed generalized estimating equations and linear mixed models adjusting for covariates to determine the associations of prenatal OPEs and RBFRs exposures with adverse respiratory outcomes in childhood, reported every six months until age 5 years and with lung function at age 5 years. We used multiple informant modeling to examine time-specific associations between maternal urinary OPEs and the outcomes.

RESULTS

Dust concentrations of triphenyl phosphate (TPHP) (RR: 1.40, 95% CI: 1.18-1.66), 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (RR: 1.51, 95% CI: 1.23-1.85), and bis(2-ethylhexyl) tetrabromophthalate (RR: 1.57, 95% CI: 1.28-1.94) were associated with higher risk of wheezing during childhood. Dust TPHP concentrations were associated with higher risk of respiratory infections (RR: 1.43, 95% CI: 1.08-1.94), and dust tris-(2-chloroethyl) phosphate concentrations were associated with hay fever/allergies (RR: 1.11, 95% CI: 1.01-1.21). We also found that dust tris-(2-chloroethyl) phosphate loadings were associated with lower lung function. Urinary OPEs mainly at week 16 of gestation tended to be associated with adverse respiratory outcome, while bis(1-chloro-2-propyl) phosphate and diphenyl phosphate at delivery were associated with lower risk of hay fever/allergies.

CONCLUSIONS

In-utero exposure to OPEs and RBFRs may be a risk factor for adverse respiratory outcomes in childhood, depending on the timing of exposure.

Comprehensive profiling and semi-quantification of exogenous chemicals in human urine using HRMS-based strategies

Chemicals infiltrate our daily experiences through multiple exposure pathways. Human biomonitoring (HBM) is routinely used to comprehensively understand these chemical interactions. Historically, HBM depended on targeted screening methods limited to a relatively small set of chemicals with triple quadrupole instruments typically. However, recent advances in high-resolution mass spectrometry (HRMS) have facilitated the use of broad-scope target, suspect, and non-target strategies, enhancing chemical exposome characterization within acceptable detection limits. Despite these advancements, establishing robust and efficient sample treatment protocols is still essential for trustworthy broad-range chemical analysis. This study sought to validate a methodology leveraging HRMS-based strategies for accurate profiling of exogenous chemicals and related metabolites in urine samples. We evaluated five extraction protocols, each encompassing various chemical classes, such as pharmaceuticals, plastic additives, personal care products, and pesticides, in terms of their extraction recoveries, linearity, matrix effect, sensitivity, and reproducibility. The most effective protocol was extensively validated and subsequently applied to 10 real human urine samples using wide-scope target analysis encompassing over 2000 chemicals. We successfully identified and semi-quantified a total of 36 chemicals using an ionization efficiency-based model, affirming the methodology's robust performance. Notably, our results dismissed the need for a deconjugation step, a typically labor-intensive and time-consuming process.

Associations between exposure to organophosphate esters and overactive bladder in U.S. adults: a cross-sectional study

Background

The relationship between exposure to organophosphate esters (OPEs) and the risk of developing overactive bladder (OAB) is uncertain. The purpose of this study is to examine the potential link between urinary metabolites of organophosphate esters and OAB.

Method

Data from the National Health and Nutrition Examination Survey (NHANES) database of the 2011-2016 cycles were utilized. Four urinary metabolites of organophosphate esters: diphenyl phosphate (DPHP), bis (1,3-dichloro-2-propyl) phosphate (BDCPP), bis (2-chloroethyl) phosphate (BCEP), and dibutyl phosphate (DBUP) were included in the study. Multivariate logistic regression and restricted cubic spline (RCS) were used to evaluate the relationship between urinary OPEs metabolites and OAB. Interaction analysis was conducted on subgroups to confirm the findings.

Results

A total of 3,443 United States (US) adults aged 20 years or older were included in the study, of whom 597 participants were considered to have OAB. After adjusting for potential confounding factors, we found a positive association between DPHP and the risk of overactive bladder. The risk of overactive bladder increased with increasing DPHP concentrations compared with quartile 1 (quartile 2, OR = 1.19, 95% CI, 0.82-1.73, P = 0.34; quartile 3, OR = 1.67, 95% CI, 1.10-2.53, P = 0.02; Q4, OR = 1.75, 95% CI, 1.26-2.43, P = 0.002). However, after dividing the participants by gender, only the female group retained consistent results. Additionally, restricted cubic spline analysis revealed a nonlinear dose-response correlation between DPHP and OAB in female participants. In the subgroup analysis based on age, race, body mass index (BMI), recreational activity, smoking status, drinking status, hypertension, diabetes, and stroke, the interaction analysis revealed that the findings were uniform.

Conclusion

Our findings indicate that exposure to DPHP could elevate the risk of OAB in US adult females. Further experimental studies are needed to explore the underlying mechanism in the future.

Temporal trends and predictors of gestational exposure to organophosphate ester flame retardants and plasticizers

BACKGROUND

Organophosphate esters (OPEs), used as flame retardants and plasticizers, are chemicals of concern for maternal and infant health. Prior studies examining temporal trends and predictors of OPE exposure are primarily limited by small sample sizes.

OBJECTIVES

Characterize temporal trends and predictors of OPE exposure biomarkers.

METHODS

We determined urinary concentrations of eight biomarkers of OPE exposure at three timepoints during pregnancy for participants in the LIFECODES Fetal Growth Study (n = 900), a nested case-cohort recruited between 2007 and 2018. We examined biomarker concentrations, their variability during pregnancy, and temporal trends over the study period. In addition, we identified sociodemographic and pregnancy characteristics associated with biomarker concentrations. Analyses were conducted using both the within-subject pregnancy geometric means and biomarker concentrations measured at individual study visits.

RESULTS

Five OPE biomarkers were detected in at least 60% of the study participants. Biomarkers were not strongly correlated with one another and intraclass correlation coefficients, measuring within-subject variability during pregnancy, ranged from 0.27 to 0.51. Biomarkers exhibited varying temporal trends across study years. For example, bis(1-chloro-2-propyl) phosphate (BCIPP) increased monotonically, whereas bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) and diphenyl phosphate (DPHP), displayed non-monotonic trends with concentrations that peaked between 2011 and 2014. We observed associations between sociodemographic characteristics and OPE biomarkers. In general, concentrations of most OPE biomarkers were higher among participants from racial and ethnic minority populations, participants who were younger, had higher pre-pregnancy body mass index (BMI), and less than a college degree. We observed consistent results using either averaged or visit-specific biomarker concentrations.

SIGNIFICANCE

We observed widespread exposure to several OPEs and OPE biomarkers displayed varying temporal trends in pregnant people from 2007 to 2018. Concentrations of most OPE biomarkers varied according to sociodemographic factors, suggesting higher burdens of exposure among participants with higher pre-pregnancy BMI, those belonging to racial and ethnic minority populations, and lower educational attainment.

Residue levels of organophosphate pesticides and dialkylphosphates in agricultural products in Japan

High urinary levels of dialkylphosphates (DAPs), which are common structures of organophosphate pesticides (OPs), have been associated with several adverse health outcomes in human biomonitoring studies. Previous studies have indicated that dietary OP exposure and ingestion of environmentally degraded DAP, which is inactive with acetylcholinesterase, can lead to an increase in urinary DAP levels in the general population. However, the specific food sources contributing to the intake of OPs and DAPs have not been identified. In this study, we analyzed the levels of OPs and preformed DAPs in various food items. DAP levels were markedly high in certain fruits, such as persimmon, apple juice, kiwi, and mandarin. In contrast, only moderate levels of OPs were detected in these foods. Furthermore, the levels of OPs and DAPs were positively associated with vegetables, whereas no such association was observed in fruits. Increased consumption of certain fruits presumably leads to a marked increase in urinary DAP levels in individuals despite limited exposure to OPs, resulting in reduced reliability of urinary DAPs as a marker of OP exposure. Therefore, the possible effects of dietary habits and the resulting intake of preformed DAPs should be considered when interpreting biomonitoring data of urinary DAPs. Additionally, DAP levels in most organic foods were much lower than those in conventional foods, suggesting that the reduction in urinary DAPs by organic diet intervention may be mainly attributed to the reduced intake of preformed DAPs rather than reduced exposure to OPs. Therefore, urinary DAP levels may not be suitable indicators for evaluating ingested OP exposure.

Urinary concentrations of organophosphate esters and associated health outcomes in Korean firefighters

Although firefighters are at an increased risk of occupational exposure to chemicals, such as flame retardants, research on the exposure of Korean firefighters to organophosphate esters (OPEs)-a group of emerging flame retardants-remains limited. Therefore, in the present study, OPE metabolite concentrations in the urine samples of 149 former and current Korean firefighters were measured. Based on the data obtained, the estimated daily intakes (EDIs) of OPEs were calculated. Subsequently, the association between the urinary concentrations of OPE metabolites and the potential determinants of OPE exposure and health outcomes (e.g., obesity and serum lipids) was investigated. We found that bis(1-chloro-2-propyl) phosphate (BCIPP) and bis(2-chloroethyl) phosphate (BCEP) were the most prevalent urinary OPE metabolites, with median concentrations of 2.33 and 1.80 ng/mL, respectively; these concentrations were higher than those reported previously in other countries, such as the USA and China. Moreover, their parent compounds-tris(1-chloro-2-propyl) phosphate (TCIPP) and tris(2-chloroethyl) phosphate (TCEP)-exhibited EDIs of 126 and 94.8 ng/kg bw/day, respectively. Unlike the high detection rate of bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) in other populations, its detection rate in this study was low (6.7%), suggesting regional differences in the exposure pattern of OPEs among countries. Furthermore, occupational characteristics, such as recent participation in firefighting activity, were identified as determinants of the urinary concentrations of OPE metabolites. Total OPE metabolites were inversely associated with body mass index and positively associated with high-density lipoprotein cholesterol. Overall, our findings demonstrate that Korean firefighters are highly exposed to several occupation-related OPEs. Further prospective studies will help elucidate the potential health implications of occupational exposure to OPEs among firefighters.

Early-life exposure to a mixture of organophosphate esters and child behavior

Organophosphate esters (OPEs), widely used as flame retardants and plasticizers for commercial and residential purposes, are suspected of being neurotoxic. We aimed to assess exposure to an OPE mixture in early life and its relationship to parent-reported child behavior. We measured urinary concentrations of three OPE metabolites, bis-2-chloroethyl phosphate (BCEP), bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), and diphenyl phosphate (DPHP), at pregnancy (16 and 26 weeks of gestation and delivery) and postnatal time points (ages 1, 2, 3, and 5 years) in the Health Outcomes and Measures of the Environment Study, a longitudinal pregnancy and birth cohort in Cincinnati, Ohio, USA (enrolled 2003-2006, n = 219). We used latent variable analysis in structural equations models and quantile g-computation to investigate associations of a mixture of the three OPE metabolites with parent-reported child behaviors at 3 and 8 years, measured using the Behavioral Assessment System for Children, Second Edition. Higher log-transformed urinary OPE latent variable values at 16 weeks were associated with fewer externalizing problem behaviors (ß = -5.74; 95% CI = -11.24, -0.24) and fewer overall behavioral problems at age 3 years (ß = -5.26; 95% CI = -10.33, -0.19), whereas having higher OPEs at delivery was associated with poorer overall behavioral problems at age 3 years (ß = 2.87; 95% CI = 0.13, 5.61). OPE latent variable values at 16 weeks, 26 weeks, and delivery were not associated with child behavior at 8 years. However, higher OPE latent variable values at 3 years were associated with fewer externalizing behaviors at 8 years (ß = -2.62; 95% CI = -5.13, -0.12). The quantile g-computation estimates had directions largely consistent with the latent variable analysis results. Pregnancy and postnatal urinary OPE metabolite mixtures were associated with child internalizing, externalizing, and overall negative behaviors at 3 and 8 years, but we did not identify a consistent pattern in terms of the direction of the effects or a particularly sensitive time point.

Biomonitoring of firefighting forces: a review on biomarkers of exposure to health-relevant pollutants released from fires

Occupational exposure as a firefighter has recently been classified as a carcinogen to humans by International Agency for Research on Cancer (IARC). Biomonitoring has been increasingly used to characterize exposure of firefighting forces to contaminants. However, available data are dispersed and information on the most relevant and promising biomarkers in this context of firefighting is missing. This review presents a comprehensive summary and critical appraisal of existing biomarkers of exposure including volatile organic compounds such as polycyclic aromatic hydrocarbons, several other persistent other organic pollutants as well as heavy metals and metalloids detected in biological fluids of firefighters attending different fire scenarios. Urine was the most characterized matrix, followed by blood. Firefighters exhaled breath and saliva were poorly evaluated. Overall, biological levels of compounds were predominantly increased in firefighters after participation in firefighting activities. Biomonitoring studies combining different biomarkers of exposure and of effect are currently limited but exploratory findings are of high interest. However, biomonitoring still has some unresolved major limitations since reference or recommended values are not yet established for most biomarkers. In addition, half-lives values for most of the biomarkers have thus far not been defined, which significantly hampers the design of studies. These limitations need to be tackled urgently to improve risk assessment and support implementation of better more effective preventive strategies.

Gestational exposure to organophosphate esters and infant anthropometric measures in the first 4 weeks after birth

BACKGROUND

Few studies have examined whether gestational exposure to organophosphate esters (OPEs), widely used chemicals with potential endocrine-disrupting potency and developmental toxicity, is associated with impaired infant growth.

METHODS

We analyzed data from 329 mother-infant pairs in the Health Outcomes and Measures of the Environment (HOME) Study (2003-2006, Cincinnati, Ohio, USA). We quantified concentrations of four OPE metabolites in maternal urine collected at 16 and 26 weeks of gestation, and at delivery. We calculated z-scores using 2006 World Health Organization (WHO) child growth standards for the 4-week anthropometric measures (weight, length, and head circumference), the ponderal index, and weekly growth rates. We used multiple informant models to examine window-specific associations between individual OPE metabolites and anthropometric outcomes. We further modeled OPEs as a mixture for window-specific associations with 4-week anthropometric outcomes using mean field variational Bayesian inference procedure for lagged kernel machine regression (MFVB-LKMR). We stratified the models by infant sex.

RESULTS

Diphenyl phosphate (DPHP) in mothers at 16 weeks, and bis(2-chloroethyl) phosphate (BCEP) and bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) at delivery were positively associated with z-scores of weight, length, and head circumference in all infants at 4 weeks of age. After stratifying by infant sex, positive associations were only observed in males for DPHP at 16 weeks and BCEP at delivery and in females for BDCIPP at delivery. Negative associations not present in all infants were observed in males for di-n-butyl phosphate (DNBP) at 26 weeks of gestation with weight z-score and DPHP at delivery with head circumference z-score. Results were generally similar using MFVB-LKMR models with more conservative 95 % credible intervals. We did not identify consistent associations of gestational OPE metabolite concentrations with the ponderal index and weekly growth rates.

CONCLUSION

In this cohort, exposure to OPEs during gestation was associated with altered infant anthropometry at 4 weeks after birth.

Associations of gestational exposure to organophosphate esters with gestational age and neonatal anthropometric measures: The HOME study

Organophosphate esters (OPEs) are developmental toxicants in experimental studies of animals, but limited evidence is available in humans. We included 340 mother-infant pairs in the Health Outcomes and Measures of the Environment (HOME) Study (Cincinnati, Ohio, USA) for the analysis. We evaluated gestational exposure to OPEs with gestation age at birth and newborn anthropometric measures. We quantified four OPE urinary metabolites at 16 weeks and 26 weeks of gestation. We extracted gestational age at birth, newborn weight, length, and head circumference from the chart review. We calculated z-scores for these anthropometric measures and the ponderal index. We used multiple informant models to examine the associations between repeated OPE measurements and the outcomes. We used modified Poisson regression to estimate the association of gestational exposure to OPEs with preterm birth. We also explored effect modification by infant sex and the potential mediation effect by the highest maternal blood pressure and glucose levels. We found that bis(2-chloroethyl) phosphate (BCEP) at 16 weeks and diphenyl phosphate at 26 weeks of pregnancy were positively associated with gestational age and inversely associated with preterm birth. In female newborns, BCEP at 16 weeks was inversely related to birth weight and length z-scores. In male newborns, we observed negative associations of 26-week di-n-butyl phosphate with the ponderal index at birth. No mediation by the highest maternal blood pressure or glucose levels during pregnancy was identified. In this cohort, gestational exposure to some OPEs was associated with gestational age, preterm birth, and neonatal anthropometric measures. Certain associations tended to be window- and infant sex-specific.

Chlorinated Organophosphate Flame Retardants Impair the Lung Function via the IL-6/JAK/STAT Signaling Pathway

Toxicological studies have revealed the adverse impacts of organophosphate flame retardants (OPFRs) on the respiratory system, while there is a lack of epidemiological evidence, and information for risk assessment remains insufficient. Herein, we investigated the associations of urinary metabolites of OPFRs with the lung function in 987 adults participating in the U.S. National Health and Nutrition Examination Survey 2011-2012. The elevation of three primary metabolites of chlorinated OPFRs [bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), bis(2-chloroethyl) phosphate (BCEP), and bis(1-chloro-2-propyl) phosphate (BCIPP)] was related to pulmonary dysfunction in a sample-weighted regression model. Each one-unit increase in the log-transformed levels of BDCIPP and BCEP was related to 91.52 and 79.34 mL reductions in the forced vital capacity (FVC). Each one-unit elevation in BCIPP was correlated with 130.86, 153.56, 302.26, and 148.24 mL reductions in forced expiratory volume 1st second (FEV₁), FVC, peak expiratory flow rate (PEF), and forced expiratory flow at 25-75% of FVC (FEF_25-75%), respectively. Then, an adverse outcome pathway (AOP) framework was constructed using the Comparative Toxicogenomics Database, the Toxicity Forecaster, and the GeneCards database. Based on the weight of the evidence, BDCIPP, BCEP, BCIPP, and their parent compounds (TDCIPP, TCEP, and TCIPP) may affect the IL-6/Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway, induce airway remodeling, and impair the lung function. Additionally, tobacco smoke exposure may modify the effects of BDCIPP on the lung function (P_int < 0.05) and affect the IL-6-mediated AOP. These results suggested that chlorinated OPFRs were associated with pulmonary dysfunction via the IL-6/JAK/STAT pathway.

Early life organophosphate ester exposures and bone health at age 12 years: The Health Outcomes and Measures of the Environment (HOME) Study

BACKGROUND

No human studies have evaluated early life organophosphate ester (OPE) exposures with bone health outcomes, despite evidence of osteotoxicity.

OBJECTIVES

We assessed associations of urinary OPE metabolites measured across early life with areal bone mineral density (aBMD) and bone mineral content (BMC) at age 12 years.

METHODS

Among 223 mother-child dyads enrolled in the Health Outcomes and Measures of the Environment (HOME) Study, we quantified concentrations of bis-2-chloroethyl phosphate (BCEP), bis-(1,3-dichloro-2-propyl) (BDCIPP), di-n-butyl phosphate (DnBP), and diphenyl phosphate (DPHP) in urine collected from mothers during pregnancy and children at ages 1, 2, 3, 5, and 8 years. At age 12 years, we performed dual energy x-ray absorptiometry and calculated aBMD and BMC z-scores at six skeletal sites. We estimated overall and sex-stratified BMD/BMC z-score differences per interquartile range (IQR) increase in OPE concentrations at multiple exposure timepoints: gestation (average) and 1-3 (average), 5, and 8 years.

RESULTS

In adjusted models, overall associations of BCEP and BDCIPP with total hip and 1/3rd distal radius aBMD and BMC varied significantly by exposure timepoint, as did BDCIPP with whole body aBMD. For example, differences (95 % CI) in total hip aBMD z-score per IQR increase in BDCIPP were 0.33 (0.01, 0.64), -0.10 (-0.34, 0.14), -0.18 (-0.40, 0.05), and 0.14 (-0.09, 0.38) for concentrations during gestation and at 1-3, 5, and 8 years, respectively. Overall DnBP and DPHP associations were generally null at all timepoints. We observed sex-specific associations for some timepoints and skeletal sites. For example, an IQR increase in 8-year DPHP was associated with a 0.21 (0.05, 0.38) greater total hip aBMD z-score among females but -0.19 (-0.43, 0.05) lower z-score among males.

DISCUSSION

Early life OPE exposures may be associated with sex- and exposure period-dependent alterations in early adolescent bone mineral accrual and strength.

Childhood urinary organophosphate esters and cognitive abilities in a longitudinal cohort study

The use of organophosphate esters (OPEs) as flame retardants, which has increased over the past two decades, raises concerns that OPEs may be harmful to humans, especially children. Animal studies and some human studies have reported that OPEs may adversely impact brain development, but few human studies evaluated OPE exposure during early childhood and neurodevelopmental outcomes. We aimed to fill this knowledge gap with the present study on urinary OPE metabolite concentrations at ages 1-5 years and cognitive abilities at 8 years. We used data of 223 children from the Health Outcomes and Measures of the Environment (HOME) Study, a prospective pregnancy and birth cohort in Cincinnati, Ohio. The point estimates for bis-2-chloroethyl-phosphate (BCEP) and bis(1,3-dichloro-2-propyl)-phosphate (BDCIPP) in association with IQ tended to be small and positive, while the point estimates for diphenyl-phosphate (DPHP) were small and negative, with 95% CIs including the null. However, we did find that socioeconomic status (SES) variables modified associations between OPEs and child IQ, with adverse OPE-IQ associations being stronger in socioeconomically disadvantaged children than in others. We identified an additional 1- to 2-point decrease in Full Scale IQ for every log-unit increase in BDCIPP, BCEP, and DPHP among those with lower maternal education, non-white race, lower income, or living in more deprived neighborhoods. We observed similar results for the Perceptual Reasoning, Verbal Comprehension, and Working Memory Index Scores. We suspect that there is residual confounding related to socioeconomic disadvantage, which was not captured with the available SES variables typically used in epidemiologic studies.

Organophosphorus insecticides exposure and sex hormones in general U.S. population: A cross-sectional study

BACKGROUND

Evidence showed organophosphorus (OPs) insecticide exposure is common in general population with endocrine-disrupting effects. However, the association between OPs metabolites and sex hormones remains unclear.

OBJECTIVE

To investigate the association between OPs metabolites and sex hormones.

METHODS

Data of 1438 participants from NHANES 2015-2016 was applied. Urinary OPs metabolites, dialkyl phosphates (DAPs), and serum sex hormones (total testosterone (TT), estradiol (E₂), and sex hormone-binding globulin (SHBG)) were measured. Free androgen index (FAI) and TT/E₂ ratio were also calculated. The generalized linear regression model and restricted cubic spline (RCS) model were employed to evaluate the association and exposure-response curve of DAPs and sex hormones in males and females. The modulation effect of age on their associations in female participants was also explored.

RESULTS

After adjusting for confounding factors, DETP was negatively associated with E₂ (β = -0.03; 95% CI: -0.05, -0.01) and FAI (β = -0.03; 95% CI: -0.06, -0.001) in males. In females, all the four DAP metabolites (DMP, DEP, DMTP, and DETP) were negatively associated with FAI (DMP: β = -0.06, 95% CI: -0.11, -0.01; DEP: β = -0.06, 95% CI: -0.12, -0.01; DMTP: -0.05, 95% CI: -0.09, -0.02; DETP: -0.09, 95% CI: -0.14, -0.04). DETP was also found negatively associated with TT and TT/E₂ ratio in females. The associations between DETP and TT, FAI, and TT/E₂ ratio were modified by gender (P_interaction<0.05). RCS analysis found these associations were in linear decreased exposure-response curves. For females of different age groups, the inverse associations of DETP with TT and FAI remained stable. Decreased FAI with DMP and DMTP was also found in females ≤50 years old.

CONCLUSIONS

Our study indicates OPs metabolites had negative associations with androgen indicators, which was characterized as decreased FAI and E₂ in males and decreased TT, FAI, and TT/E₂ ratio in females, particularly among females ≤50 years old. Further studies are warranted in larger-scale populations.

Ubiquitin proteasomal system is a potential target of the toxic effects of organophosphorus flame retardant triphenyl phosphate

The consumption of the widely used flame retardant Triphenyl phosphate (TPP) is increasing. It is now frequently detected in the environment and also domestically. Although the possibility of dermal exposure to TPP is quite high, little is known about its potential molecular toxicity mechanisms. In this study, we found that TPP caused cytotoxicity on human skin keratinocytes (HaCaT) and significantly inhibited the proliferation and cell migration in a concentration-dependent manner. Additionally, HaCaT cells were sensitive to TPP-induced apoptosis. Reactive oxygen species production was induced with TPP, which increased the protein carbonylation and lipid peroxidation levels. Moreover, TPP inhibited proteasome activity and increased the accumulation of ubiquitinated proteins. Exposure to TPP significantly increased the HSP90, HSP70, GRP94 and GRP78 protein levels. Overall, our findings indicate that TPP may pose a risk to human health and contribute to the current understanding of the risks of TPP at the molecular level.

Simultaneous determination of 16 urinary metabolites of organophosphate flame retardants and organophosphate pesticides by solid phase extraction and ultra performance liquid chromatography coupled to tandem mass spectrometry

Organophosphate flame retardants (OPFRs) and organophosphate pesticides (OPPs), pertaining to organophosphate esters, are ubiquitous in environment and have been verified to pose noticeable risks to human health. To evaluate human exposures to OPFRs and OPPs, a fast and sensitive approach based on a solid phase extraction (SPE) followed by the ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) detection has been developed for the simultaneous analysis of multiple organophosphorus metabolites in urine. The method allows the identification and quantification of ten metabolites of the most common OPFRs and all six dialkylphosphates (DAPs) of OPPs concerning the population exposure characteristics. The method provided good linearities (R² = 0.998-0.999), satisfactory method detection limits (MDLs) (0.030-1.129 ng/mL) and only needed a small volume (200 μL) of urine. Recovery rates ranged 73.4-127.1% at three spiking levels (2, 10 and 25 ng/mL urine), with both intra- and inter-day precision less than 14%. The good correlations for DAPs in a cross-validation test with a previous gas chromatography-mass spectrometry (GC-MS) method and a good inter-laboratory agreement for several OPFR metabolites in a standard reference material (SRM 3673) re-enforced the precision and validity of our method. Finally, the established method was successfully applied to analyze 16 organophosphorus metabolites in 35 Chinese children's urine samples. Overall, by validating the method's sensitivity, accuracy, precision, reproducibility, etc., data reliability and robustness were ensured; and the satisfactory pilot application on real urine samples demonstrated feasibility and acceptability of this method for being implemented in large population-based studies.

Validated single urinary assay designed for exposomic multi-class biomarkers of common environmental exposures

Epidemiological studies often call for analytical methods that use a small biospecimen volume to quantify trace level exposures to environmental chemical mixtures. Currently, as many as 150 polar metabolites of environmental chemicals have been found in urine. Therefore, we developed a multi-class method for quantitation of biomarkers in urine. A single sample preparation followed by three LC injections was optimized in a proof-of-approach for a multi-class method. The assay was validated to quantify 50 biomarkers of exposure in urine, belonging to 7 chemical classes and 16 sub-classes. The classes represent metabolites of 12 personal care and consumer product chemicals (PCPs), 5 polycyclic aromatic hydrocarbons (PAHs), 5 organophosphate flame retardants (OPFRs), 18 pesticides, 5 volatile organic compounds (VOCs), 4 tobacco alkaloids, and 1 drug of abuse. Human urine (0.2 mL) was spiked with isotope-labeled internal standards, enzymatically deconjugated, extracted by solid-phase extraction, and analyzed using high-performance liquid chromatography-tandem mass spectrometry. The methanol eluate from the cleanup was split in half and the first half analyzed for PCPs, PAH, and OPFR on a Betasil C18 column; and pesticides and VOC on a Hypersil Gold AQ column. The second half was analyzed for tobacco smoke metabolites and a drug of abuse on a Synergi Polar RP column. Limits of detection ranged from 0.01 to 1.0 ng/mL of urine, with the majority ≤0.5 ng/mL (42/50). Analytical precision, estimated as relative standard deviation of intra- and inter-batch uncertainty, variabilities, was <20%. Extraction recoveries ranged from 83 to 109%. Results from the optimized multi-class method were qualified in formal international proficiency testing programs. Further method customization options were explored and method expansion was demonstrated by inclusion of up to 101 analytes of endo- and exogenous chemicals. This exposome-scale assay is being used for population studies with savings of assay costs and biospecimens, providing both quantitative results and the discovery of unexpected exposures.

Maternal urinary organophosphate ester metabolite concentrations and glucose tolerance during pregnancy: The HOME Study

BACKGROUND

Endocrine-disrupting chemicals may alter glucose homeostasis, especially during pregnancy. Biomonitoring studies suggest ubiquitous human exposure to organophosphate esters (OPEs), chemicals with endocrine-disrupting capabilities. Few studies have examined the association between maternal exposure to OPEs and blood glucose during pregnancy.

METHODS

With data from 301 pregnant women in the Health Outcomes and Measures of the Environment (HOME) Study, a prospective pregnancy and birth cohort in Cincinnati, Ohio, USA, we examined whether OPE concentrations were associated with changes in blood glucose. We quantified four OPE metabolites in maternal spot urine samples collected at 16- and 26-weeks pregnancy. We extracted results from the glucose challenge test (GCT) and oral glucose tolerance test (OGTT) via medical chart review. Women with GCT ≥ 140 mg/dL or any abnormal values in OGTT (≥ 95 mg/dL fasting glucose, ≥ 180 mg/dL 1-h glucose, ≥ 155 mg/dL 2-h glucose, ≥ 140 mg/dL 3-h glucose) were defined as having elevated glucose levels. We used linear regression and Bayesian Kernel Machine Regression (BKMR) to estimate the associations of individual OPE metabolites and OPE mixtures with blood glucose levels during pregnancy. We used modified Poisson regression to estimate the associations of OPE metabolite concentrations with elevated glucose levels. We further examined effect measure modification by maternal characteristics (age, pre-pregnancy body mass index [BMI], and race/ethnicity).

RESULTS

Diphenyl phosphate (DPHP) had the highest geometric mean concentration of the urinary OPE metabolites (1.83 μg/L at 16 weeks, 1.24 μg/L at 26 weeks). Thirty women (10.0%) had elevated glucose levels. Individual OPE metabolites or their mixtures were not significantly associated with continuous GCT results. We did not observe effect measure modification by maternal age, pre-pregnancy BMI categories, or race/ethnicity. Compared with women in the 1st tertile of average DPHP of 16- and 26 weeks of pregnancy, women in the 3rd tertile tended to have a reduced risk of elevated glucose levels (RR = 0.41, 95% CI = 0.16-1.06, p for trend = 0.06).

CONCLUSION

In this cohort, maternal urinary OPE metabolite concentrations were weakly associated with blood glucose levels during pregnancy.

A QuEChERS-based UPLC-MS/MS method for rapid determination of organophosphate flame retardants and their metabolites in human urine

Organophosphate flame retardants (OPFRs) have been widely used in consumer products to prevent fire spread. However, once released into the atmospheric environment, they may accumulate in humans and undergo metabolic transformation and excretion by urine. In order to clarify the human exposure to OPFRs, a quick, easy, cheap, effective, rugged, and safe method for the simultaneous determination of urinary OPFRs and their metabolites by ultra-performance liquid chromatography-tandem triple quadrupole mass spectrometry was developed. After the optimization by a single-factor or orthogonal experiment, the satisfactory recovery (87.8-119%), matrix effect (-8.88-9.29%), method quantitation limit (3.66-159 ng/L), and inter-day repeatability (1.24 - 10.6%) of most analytes were achieved in artificial urine samples. Based on a monitoring test by the developed method, we propose that urinary bis(1-chloro-2-propyl) phosphate and di-p-cresyl phosphate could be used to trace human exposure to tris(1-chloro-2-propyl) phosphate and tricresyl phosphate, respectively. Most importantly, this is the first study to reveal that 4-hydroxyphenyl diphenyl phosphate (4-OH-TPHP) was dominantly presented in its conjugated form rather than its free form in urine (p = 0.037). Overall, the obtained results contribute a relatively rapid method to help conduct large-scale urine monitoring for revealing the human exposure and risk of OPFRs.

Maternal urinary OPE metabolite concentrations and blood pressure during pregnancy: The HOME study

BACKGROUND

Few studies have examined the association between maternal exposure to organophosphate esters (OPEs) and systolic/diastolic blood pressure (SBP/DBP) during pregnancy.

METHODS

We analyzed data from 346 women with a singleton live birth in the HOME Study, a prospective birth cohort in Cincinnati, Ohio, USA. We quantified four OPE metabolites in maternal spot urine samples collected at 16 and 26 weeks pregnancy, standardized by specific gravity. We calculated intraclass correlation coefficients (ICCs). We extracted the first two recorded BP measurements (<20 weeks), the two highest recorded BP measurements (≥20 weeks), and diagnoses of hypertensive disorders of pregnancy (HDP) via chart review. Women with two BP measurements ≥140/90 mmHg or HDP noted in the chart at ≥20 weeks pregnancy were defined as HDP cases. We used linear mixed models and modified Poisson regression with covariate adjustment to estimate associations between OPE concentrations as continuous variables or in tertiles with maternal BP and HDP.

RESULTS

ICCs of OPEs were 0.17-0.45. Diphenyl phosphate (DPHP) had the highest geometric mean concentration among OPE metabolites. Increasing the average bis(2-chloroethyl) phosphate (BCEP) concentrations were positively associated with two highest recorded DBP ≥20 weeks pregnancy. Compared with women in the 1st DPHP tertile, women in the 3rd tertile at 16 weeks pregnancy had 1.72 mmHg (95% CI: -0.01, 3.46) higher DBP <20 weeks pregnancy, and women in the 3rd tertile of the average DPHP concentrations had 2.25 mmHg (95% CI: 0.25, 4.25) higher DBP ≥20 weeks pregnancy. 33 women (9.5%) were identified with HDP. Di-n-butyl phosphate (DNBP) concentrations at 16 weeks were positively associated with HDP, with borderline significance (RR = 2.98, 95% CI 0.97-9.15). Other OPE metabolites were not significantly associated with HDP.

CONCLUSION

Maternal urinary BCEP and DPHP concentrations were associated with increased BP during pregnancy. Maternal urinary DNBP concentrations were associated with HDP, with borderline significance.

The associations between organophosphate esters and urinary incontinence in the general US population

Organophosphate esters (OPEs) impact health in many ways. Since its relationship with urinary incontinence remains unknown, we aimed to explore their associations in the US general population. We combined the results of urine specimens test and self-reported urinary incontinence conditions from the National Health and Nutrition Examination Survey (NHANES) 2013-2014 among 2666 participants and then conducted linear regression and logistic regression to analyse associations between log2-transformed OPE concentrations and urinary incontinence. We found that 0.92% of men and 15.74% of women complained of mixed urinary incontinence (MUI). The concentrations of diphenyl phosphate (DPHP) were significantly correlated to MUI among women when treated as a continuous variable (adjusted odds ratio (OR) = 1.15; 95% confidence interval (CI), 1.01-1.31; p = 0.0369) and as a categorical variable (adjusted OR = 1.24; 95% CI, 1.03-1.49; p for trend = 0.0245), whereas no positive correlation was found in males. There were no significant associations between the other three OPEs: bis(2-chloroethyl) phosphate (BCEP), bis(1,3-dichloro-2-propyl) phosphate (BDCPP) and dibutyl phosphate (DBUP). The association of DPHP with an increased prevalence OR of MUI in women is a public health concern; future prospective studies are needed to explore its potential mechanism.

Urinary biohazard markers in firefighters

Firefighters are the professional force at high risk of suffering potential health consequences due to their chronic exposure to numerous hazardous pollutants during firefighting activities. Unfortunately, determination of fire emission exposure is very challenging. As such, the identification and development of appropriate biomarkers is critical in meeting this need. This chapter presents a critical review of current information related with the use of different urinary biomarkers of effect and exposure in occupationally exposed firefighters over the last 25 years. Evidence suggests that urinary isoprostanes and mutagenicity testing are promising biomarkers of early oxidative stress. Data indicate that firefighters participating in firefighting activities present with increased urinary biomarkers of exposure. These include polycyclic aromatic hydrocarbons, heavy metals and metalloids, organo-chlorine and -phosphorus compounds, environmental phenols, phthalates, benzene and toluene. More studies are urgently needed to better evaluate firefighter occupational safety and health and to support the implementation of preventive measures and mitigation strategies to promote the protection of this chronically exposed group of workers.

Life Cycle Exposure to Environmentally Relevant Concentrations of Diphenyl Phosphate (DPhP) Inhibits Growth and Energy Metabolism of Zebrafish in a Sex-Specific Manner

Due to commercial uses and environmental degradation of aryl phosphate esters, diphenyl phosphate (DPhP) is frequently detected in environmental matrices and is thus of growing concern worldwide. However, information on potential adverse effects of chronic exposure to DPhP at environmentally realistic concentrations was lacking. Here, we investigated the effects of life cycle exposure to DPhP on zebrafish at environmentally relevant concentrations of 0.8, 3.9, or 35.6 μg/L and employed a dual-omics approach (metabolomics and transcriptomics) to characterize potential modes of action. Exposure to DPhP at 35.6 μg/L for 120 days resulted in significant reductions in body mass and length of male zebrafish, but did not cause those same effects to females. Predominant toxicological mechanisms, including inhibition of oxidative phosphorylation, down-regulation of fatty acid oxidation, and up-regulation of phosphatidylcholine degradation, were revealed by integrated dual-omics analysis and successfully linked to adverse outcomes. Activity of succinate dehydrogenase and protein content of carnitine O-palmitoyltransferase 1 were significantly decreased in livers of male fish exposed to DPhP, which further confirmed the proposed toxicological mechanisms. This study is the first to demonstrate that chronic, low-level exposure to DPhP can retard growth via inhibiting energy output in male zebrafish.

Organophosphate (OP) diesters and a review of sources, chemical properties, environmental occurrence, adverse effects, and future directions

Over the course of the continual phase-outs of toxic halogenated flame retardants (HFRs), there has been an increasing demand for organophosphate esters (OPEs) in global FR markets. OPE-FRs have largely been identified as OP triesters, which have a basic chemical structure of O = P(OR)₃. In addition to OP triesters, OPEs can refer to another class of related substances, namely, OP diesters that have a typical chemical structure of O = P(OR)₂(OH)). OP diesters are known as biotic or abiotic degradation products of OP triesters. In recent years, environmental scientists have proven that OP diesters widely exist in a variety of environmental matrices and biotic samples around the world, implying the potential risks from OP diester exposure to biota and humans in the environment. Here, we have reviewed the scientific literature for studies involving OP diesters and up to the end of 2020. The aim of the present review is to assess the present understanding of the physicochemical properties, sources (industrial production and degradation), environmental occurrence of OP diesters, and adverse effects to exposed organisms. Based on the literature in the Web of Science core collection, we found that at least 23 OP diesters have been reported as contaminants in various environments or as degradation products of OP triesters. The physicochemical properties of OP diesters vary depending on their specific chemical structures. OP diesters containing halogen atoms and aryl groups seem to be more persistent (with greater estimated half-life (t_1/2) values) in environmental matrices. There were multiple sources of OP diesters, including industrial production and biotic or abiotic degradation from OP triesters. Specifically, we found that ten OP diesters are produced somewhere in the world, and the total annual output was estimated to be 17,050 metric tons (this number is underestimated due to the limitation of the available information). In addition, the wide application of OP triesters worldwide makes the degradation of OP triesters another critical source of OP diesters to the environment and to organisms. Current monitoring studies have demonstrated that some OP diesters were detectable in the human body (via both blood and urine samples), indoor dust, wastewater, or sewage sludge worldwide. The highest concentrations of diphenyl phosphate (DPHP) in human urine have been reported as high as 727 ng/mL (children (aged 0-5 years) urine samples from Australia). In addition, adverse effects following direct or indirect exposure to 11 OP diesters in organisms (including animals, bacteria, and algae) have been reported, and the recorded adverse outcomes following exposure to OP diesters included developmental toxicity, alteration of gene expression, and disturbance of nuclear receptor activity. Biomonitoring studies regarding human samples have frequently reported statistically significant associations between the concentrations of OP diesters and markers of human health (mainly related to reproductive toxicity). Finally, on the basis of current knowledge on OP diesters, we propose prospects for related research directions in future studies.

Prenatal exposure to a mixture of organophosphate esters and intelligence among 8-year-old children of the HOME Study

Many environmental chemicals are being identified as suspected neurotoxicants based on the findings of both experimental and epidemiological studies. Organophosphate esters (OPEs), which are among the chemicals that have replaced neurotoxic polybrominated diphenyl ethers (PBDEs) after 2004, have also become an important public health topic as evidence regarding their potential for early-life neurotoxicity is growing. In 233 mother child pairs from Cincinnati, OH, we measured concentrations of the OPE metabolites bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), bis-2-chloroethyl phosphate (BCEP), diphenyl phosphate (DPHP), and di-n-butyl phosphate (DNBP) in the urine of pregnant women at 16 and 26 weeks gestation and at delivery. At age 8 years, we assessed children's cognition using the Wechsler Intelligence Scale for Children-IV. In models adjusted for maternal race, income, body mass index, and IQ, maternal urinary BCEP was associated with a modest increase in child full-scale IQ (ß: 0.81 per a ln-unit BCEP increase; 95 % CI: 0.00, 1.61) while other OPEs were not associated with changes in full-scale IQ or any IQ subscales. Maternal serum PBDE concentrations did not confound the relationships between urinary OPE metabolites and child IQ. Using Bayesian kernel machine regression, we did not find that concentrations of a mixture of OPE metabolites during gestation was associated with any child cognition measures. The results of this study are not consistent with other published work, and a larger sample size would be beneficial to explore potential associations more fully. Therefore, additional studies are necessary to continue studying prenatal OPE exposure and child neurodevelopment and behavior.

Human internal exposure to organophosphate esters: A short review of urinary monitoring on the basis of biological metabolism research

As alternatives to traditional brominated flame retardants, organophosphate flame retardants (OPFRs), especially for organophosphate esters (OPEs) -- the most widely used and investigated OPFRs, have raised people's concern on their environmental and health-related risks over the years. Considering their extensive environmental occurrence and potential adverse effects, precise estimation on the human body burden of OPEs will be conducive to the restrictions on the usage of these compounds scientifically. Biomonitoring research can provide precise information on human exposure to OPEs as it reveals the degree of external exposure from all exposure routes. Knowledge on biotransformation and metabolism of OPEs in the biosystems is of great significance for our understanding of the internal exposure to these compounds. In this study, the biological metabolic processes of nine OPEs prevalent in the environment, involving tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCIPP), tris(1,3-dichloro-2-propyl) phosphate (TDCIPP), tripropyl phosphate (TPrP), tri-n-butyl phosphate (TnBP), tris(2-butoxyethyl) phosphate (TBOEP), triphenyl phosphate (TPhP), 2-ethylhexyl diphenyl phosphate (EHDPP), and tricresyl phosphate (TCrP), are comprehensively reviewed. Specifically, the metabolic pathway, kinetics and mechanism of OPEs are depicted in detail. Under this context, the advances and limitations on biomonitoring of OPE metabolites in human urine are summarized. The requirements of specificity, quantitative stability, high detection frequency/concentration are needed for OPE metabolites to be considered and validated as biomarkers. Thus far, deeper elucidations on the metabolic processes and identification of biomarkers of OPEs are urgently required, given that some OPEs have no suitable biomarkers in human biomonitoring. For better assessment of the body burden of OPEs in humans, reliable and effective methodologies for urine sampling and estimation on internal exposure to OPEs need to be further developed in the future.

Maternal Urinary Organophosphate Esters and Alterations in Maternal and Neonatal Thyroid Hormones

Production of organophosphate esters (OPEs), which represent a major flame-retardant class present in consumer goods, has increased over the past 2 decades. Experimental studies suggest that OPEs may be associated with thyroid hormone disruption, but few human studies have examined this association. We quantified OPE metabolites in the urine of 298 pregnant women from Cincinnati, Ohio, in the Health Outcomes and Measures of the Environment Study (enrolled 2003-2006) at 3 time points (16 and 26 weeks' gestation, and at delivery), and thyroid hormones in 16-week maternal and newborn cord sera. Urinary bis(1,3-dichloro-2-propyl)-phosphate concentrations were generally associated with decreased triiodothyronine and thyroxine levels and increased thyroid-stimulating hormone levels in maternal and newborn thyroid hormones in quartile dose-response analyses and multiple informant models. There was weaker evidence for thyroid hormone alterations in association with diphenyl-phosphate and di-n-butyl-phosphate. Bis-2-chloroethyl-phosphate was not associated with alterations in thyroid hormones in any analyses. We did not observe any evidence of effect modification by infant sex. These results suggest that gestational exposure to some OPEs may influence maternal and neonatal thyroid function, although replication in other cohorts is needed.

Evaluation of a four-zone indoor exposure model for predicting TCPP concentrations in a low-energy test house

Numerous chemicals have been detected in indoor environments that have potential impacts on occupant health and comfort. However, due to limited resources, it's infeasible to assess indoor exposure of each chemical for all indoor conditions through measurements alone. Hence, indoor exposure models have been developed to predict time-varied exposure for a wide range of sources and chemicals under different conditions. The Indoor Environmental Concentrations in Buildings with Conditioned and Unconditioned Zones (IECCU) model was developed by the United States Environmental Protection Agency. This study evaluated the predictive ability of the IECCU by comparing airborne tris(1-chloro-2-propyl) phosphate (TCPP) concentrations measured from 2013 to 2018 in a test house to modeled predictions. Inputs to IECCU included building and environment (i.e., air zone configuration and geometry, interzonal airflow rates and air temperature in each zone), parameters for both source (spray polyurethane foam (SPF)) and sinks (gypsum and wallboard), and simulation conditions. Simulations were conducted using three sets of inputs. Simulation 1 and 2 differed in using quantified versus design inputs for temperatures and airflow rates. Simulation 1 and 3 differed in the configured air zones in the IECCU model. Given the best available inputs (Simulation 1), IECCU predicted basement concentrations that were generally higher but within a factor of three of the measurements. The basement prediction/measurement ratios for all three simulations ranged from 0.5 to 8.3 and the average was 2.9, while the predicted concentrations in the living zone were generally lower but still within an order of magnitude of the measurements. The prediction accuracy decreased with time. For Simulation 1, predicted basement concentrations were on average 1.4 times higher than measurements in 2013 and 2014. However, the ratio increased to 4.7 in 2018. The design inputs of Simulation 2 resulted in greater discrepancy between measurements and predictions than the measured inputs of Simulation 1. In addition, Simulation 2 did not capture diurnal variation as well as Simulation 1. Comparisons of Simulation 1 and 2 demonstrate the importance of using accurate temperature and airflow model inputs for more accurately predicting concentrations. Furthermore, a sensitivity analysis indicated that to improve the accuracy of IECCU predictions for TCPP emission from SPF, efforts are needed to accurately measure the mass transfer parameters for SPF, especially the SPF/air partition coefficient and the initial TCPP concentration in SPF.

Urinary organophosphate esters metabolites, glucose homeostasis and prediabetes in adolescents

BACKGROUND

Emerging experimental evidence indicates that organophosphate esters (OPEs) can trigger glucose metabolic disorders. However, human evidence, especially in adolescents, is unavailable.

OBJECTIVES

We utilized data from the National Health and Nutrition Examination Survey 2011-2014 to evaluate whether urinary OPEs metabolites were associated with prediabetes and glucose homeostasis.

METHODS

A total of 349 adolescents (12-19-year old) who provided at least 8 h fasting blood samples, had urinary OPEs metabolites detected were included. Prediabetes was defined according to the levels of fasting plasma glucose (FPG), 2-h post oral plasma glucose (2 h-OGTT) and glycated hemoglobin A1c (HbA1c). The homeostatic model assessment (HOMA-IR) and the Single Point Insulin Sensitivity Estimator (SPISE) were used to assess insulin resistance and sensitivity, respectively. Multiple binary logistic and linear regressions were used to evaluate the associations with prediabetes and indices of glucose homeostasis. The least absolute shrinkage and selection operator (LASSO) regression was used to assess the associations in a multi-pollutant context.

RESULTS

After adjusting for covariates, certain urinary OPEs metabolites were associated with prediabetes and indices of glucose homeostasis in all adolescents. Stratified analyses by sex revealed that such associations were largely sex-dependent. In females, the multiple pollutant models showed that bis(1,3-32 dichloro-2-propyl) phosphate (BDCIPP) was positively associated with prediabetes [odds ratio (OR) = 2.51, 95%CI:1.29, 4.89, for one scaled unit increase in exposure] and 2 h-OGTT (β = 0.07, 95%CI:0.01,0.12); bis(2-chloroethyl) phosphate (BCEP) was negatively associated with fasting insulin (β = -0.10, 95%CI: 0.19,-0.01) and HOMA-IR (β = -0.10, 95%CI: 0.19,-0.003); and detectable bis(1-choloro-2-propyl) phosphate (BCIPP) (>LOD vs < LOD) was inversely associated with 2 h-OGTT (β = -0.11, 95%CI: 0.21,-0.02). In males, consistent inverse associations were found for detectable di-n-butyl phosphate (DNBP) with prediabetes, FPG, 2 h-OGTT, fasting insulin and HOMA-IR.

CONCLUSION

Urinary OPEs metabolites were associated with prediabetes and indices of glucose homeostasis in adolescents. But such associations varied by sex. Future studies with multiple measurements of OPEs exposure are needed to confirm our findings.

Exposure to Organophosphate esters and metabolic syndrome in adults

BACKGROUND

Organophosphate esters (OPEs) are increasingly used as flame retardants and plasticizers in various products. In vivo and in vitro studies suggest that OPEs can affect metabolic health but the human evidence is lacking.

OBJECTIVES

We analyzed data from the U.S. National Health and Nutrition Examination Survey, 2011-2014, to examine the associations between urinary OPE metabolites and metabolic syndrome (MetS) and its components in adults.

METHODS

We included a total of 1157 adults aged ≥20 years who had information on urinary OPE metabolites, components of MetS and essential covariates in the current analyses. MetS was composed of hyperglycemia, hypertension, hypertriglyceridemia, low high-density cholesterol, and central obesity. Binary logistic regression and weighted quantile sum (WQS) regression were used to assess the associations of individual OPE metabolites and OPEs mixture with MetS and its components. All analyses were conducted in men and women separately. Potential effect modification by age, serum total testosterone (TT) level and menopause status were also examined via stratified analyses as well as by testing the significance of the interaction term with exposure.

RESULTS

After adjusting for confounders, bis(2-chloroethyl) phosphate (BCEP) and bis(1,3-dichloro-2-propyl) phosphate (BDCPP) were positively associated with MetS in a dose-dependent manner (P-trend = 0.02 and 0.02 for BCEP and BDCPP, respectively) in all men. Meanwhile, increasing quartiles of DPHP was positively associated with hyperglycemia (P-trend = 0.03), but DBUP was inversely associated with central obesity (P-trend = 0.02). WQS analyses in all men found that OPEs mixture (OPEs index) was positively associated with MetS [odds ratio (OR) for OPEs index: 1.65; 95%CI :1.21, 2.24], hyperglycemia (OR:1.47; 95%CI:1.09,2.00), and central obesity (OR:1.36; 95%CI:1.01,1.83). Although there was no significant interaction between exposure and effect modifiers, stratified analyses in men suggested that significant associations were mainly limited to those aged < 60 years or those with TT < 437 ng/dL (the median level in men). By contrast, the associations with MetS and its components were sparse and inconsistent in women except for the positive association between OPEs index and central obesity.

CONCLUSIONS

In this cross-sectional study, exposure to OPEs was positively associated with elevated odds of MetS and individual components in men, especially among those aged <60 years or those with relatively low TT level. But the associations were less apparent in women except for the consistent positive association of OPEs mixture with central obesity. Nevertheless, these results need to be interpreted with caution and should be confirmed in future studies, ideally with multiple urine samples collected prospectively to improve the exposure measurement of OPEs.

Biomonitoring in firefighters for volatile organic compounds, semivolatile organic compounds, persistent organic pollutants, and metals: A systematic review

Firefighters are exposed to a wide range of toxic chemicals due to combustion, with numerous biomonitoring studies completed that have assessed exposure. Many of these studies focus on individual classes of chemicals, with a few considering a broad range of systemic exposures. As yet, no review process has been undertaken to comprehensively examine these studies. The aims of this review are to: (1) ascertain whether biomonitoring studies pertaining to firefighters demonstrate occupational exposure to volatile organic compounds, semivolatile organic compounds, and metals; (2) determine and present results of biomonitoring studies; (3) provide any recommendations presented from the literature that may support exposure mitigation; and (4) suggest future study parameters that may assist in providing a greater understanding surrounding the occupational exposure of firefighters. A systematic review was undertaken with regards to firefighters and biomonitoring studies utilising the matrices of blood, urine, semen and breast milk. This yielded 5690 results. Following duplicate removal, inclusion and exclusion criteria screening and full text screening, 34 studies remained for review. Results of over 80% of studies analysed determined firefighters to experience occupational exposure. Results also show firefighters to be exposed to a wide range of toxic chemicals due to fire smoke; potentially exceeding the range of exposure of other occupations. As firefighters may face increased risk of health effects due to the additive, synergistic, and/or antagonistic effects of chemical exposure, all care must be taken to reduce exposure. This may be achieved by considering tactical decisions, increased personal hygiene, and thorough decontamination procedures. Future biomonitoring studies recognising and assessing the range of chemical exposure firefighters face would be beneficial.

Uptake, Accumulation, and Biomarkers of PM2.5-Associated Organophosphate Flame Retardants in C57BL/6 Mice after Chronic Exposure at Real Environmental Concentrations

Although the bioaccumulation of organophosphate flame retardants (OPFRs) in aquatic organisms has been investigated, little information is available about their bioaccumulation in mammals following chronic inhalation exposure. To address this knowledge gap, C57BL/6 mice were exposed to 7 PM_2.5-associated OPFRs via the trachea to study their bioaccumulation, tissue distribution, and urinary metabolites. Low (corresponding to the real PM_2.5 concentrations occurring during winter in Guangzhou), medium, and high dosages were examined. After 72 days' exposure, ∑OPFR concentrations in tissues from mice in the medium dosage group decreased in the order of intestine > heart > stomach > testis > kidney > spleen > brain > liver > lung > muscle. Of the OPFRs detected in all three exposure groups, chlorinated alkyl OPFRs were most heavily accumulated in mice. We found a significant positive correlation between the bioaccumulation ratio and octanol-air partition coefficient (K_OA) in mice tissues for low log K_OW OPFR congeners (log K_OW ≤ 4, p < 0.05). Three urinary metabolites (di-p-cresyl phosphate: DCrP, diphenyl phosphate: DPhP, dibutyl phosphate: DnBP) were detected from the high dosage group. These results provide important insights into the bioaccumulation potential of OPFRs in mammals and emphasize the health risk of chlorinated alkyl OPFRs.