Associations of urinary organophosphate esters metabolites and diet quality with nonalcoholic/metabolic dysfunction-associated fatty liver diseases in adults

Whether exposure to organophosphate esters (OPEs) is associated with metabolic dysfunction-associated fatty liver disease (MAFLD) and nonalcoholic fatty liver disease (NAFLD) remains unclear. A healthy diet is crucial to metabolic health and dietary intake is also an important route for OPEs exposure. However, the joint associations of OPEs, diet quality, and the effect modification by diet quality remain unknown. This study comprised 2618 adults with complete data on 6 urinary OPEs metabolites, 24 h dietary recalls, and definitions of NAFLD and MAFLD from the 2011-2018 National Health and Nutrition Examination Survey cycles. Multivariable binary logistic regression was applied to assess the associations of OPEs metabolites with NAFLD, MAFLD, and components of MAFLD. We also adopted the quantile g-Computation method to examine the associations of OPEs metabolites mixture. Our results revealed that OPEs metabolites mixture and three individual metabolites [i.e., bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), bis(2-chloroethyl) phosphate, and diphenyl phosphate] were significantly and positively associated with NAFLD and MAFLD (P-trend<0.001), with BDCIPP being identified as the dominant metabolite, whereas the 4 diet quality scores were monotonically and inversely associated with both MAFLD and NAFLD (P-trend<0.001). Of note, 4 diet quality scores were by and large negatively associated with BDCIPP, but not with other OPEs metabolites. Joint association analyses revealed that individuals with higher diet quality and lower BDCIPP concentration tend to have lower odds of having MAFLD and NAFLD in comparison with people in the low diet quality and high BDCIPP group, but the associations of BDCIPP were not modified by diet quality. Our findings suggest that certain OPEs metabolites and diet quality exhibited opposing associations with both MAFLD and NAFLD. Individuals adherent to a healthier diet may have a lower level of certain OPEs metabolites, and thus could have lower odds of having NAFLD and MAFLD.

Evaluating how occupational exposure to organophosphates and pyrethroids impacts ADHD severity in Egyptian male adolescents

BACKGROUND

Attention Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder characterized by deficits in attention and hyperactivity/impulsivity that cause impairments to daily living. An area of long-standing concern is understanding links between environmental toxicants, including pesticides, and the development or worsening of ADHD.

OBJECTIVES

The present study evaluated associations between occupational pesticide exposure, specifically organophosphate (OP) pesticides, chlorpyrifos (CPF) and the pyrethroids (PYR) alpha-cypermethrin (αCM) and lambda-cyhalothrin (λCH), and symptoms of ADHD in a longitudinal study among Egyptian adolescent males.

METHODS

Participants (N = 226, mean age = 17) were Egyptian adolescent males who either applied pesticides or were non-applicators. Urinary trichloro-2-pyridinol (TCPy) was measured as a specific metabolite biomarker of exposure to chlorpyrifos. Urinary 3-phenoxybenzoic acid (3-PBA) was measured as a general metabolite biomarker of exposure to pyrethroids, while urinary cis-3-(2,2- dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (cis-DCCA) was measured as a specific biomarker of exposure to αCM and lambda cyhalothric acid (λCH acid) measured as a specific biomarker of exposure to λCH. Ordinal logistic regression models controlling for age were used to determine the likelihood of ADHD development (measured via parent-reported ADHD symptoms) as the level of biomarkers of pesticide exposure increased.

RESULTS

Cis-DCCA was the only biomarker associated with higher likelihood ADHD symptoms (> 0.60 vs. 0-0.17 μg/g creatinine; OR = 2.82, 95% CI: 1.29-6.14). All participants reported clinical levels of ADHD symptoms when compared to national norms used in the United States. TCPy, trans-DCCA and λCH acid were not associated with risk of ADHD symptoms after controlling for levels of cis-DCCA. No other metabolites were associated with the number of ADHD symptoms. There were no interaction effects found for exposure to both OPs and Pyrethroids.

DISCUSSION

The results suggest that exposure to the pyrethroid αCM is associated with more ADHD symptoms. Methodological and cultural considerations in need of further study are discussed.

Prenatal exposure to organophosphate esters is associated with decreased anogenital distance in offspring

BACKGROUND

Evidence from in vitro and rodent studies suggests that organophosphate esters (OPEs) may disrupt sex steroid hormone homeostasis, but no human studies, to date, have examined the effects of in utero exposure to OPEs on offspring reproductive development.

OBJECTIVE

Anogenital distance (AGD) is a sensitive biomarker of fetal hormonal milieu and has been used to assess reproductive toxicity. We evaluated the longitudinal effects of prenatal exposure to OPEs on the AGD of offspring from birth to 4 years.

METHODS

Based on Shanghai-Minhang Birth Cohort Study, pregnant women provided urine samples at a gestational age of 12-16 weeks, which were analyzed for eight OPE metabolites. AGD was measured in offspring at birth and 0.5, 1, and 4 years of age. We used generalized estimating equations (GEE) and Bayesian kernel machine regression (BKMR) models to estimate the associations of prenatal exposure to individual OPE metabolites and OPE mixtures with AGD stratified by sex.

RESULTS

A total of 733 mother-infant pairs were analyzed. Prenatal exposure to diphenyl phosphate and bis-(2-ethylhexyl) phosphate was associated with decreased AGD in boys in GEE models. Bis-(1-chloro-2-propyl) phosphate (BCIPP) showed a similar but marginally significant effect. Prenatal exposure to most OPE metabolites was associated with decreased AGD in girls, with the most profound association observed for bis (2-butoxyethyl) phosphate (BBOEP) and alkyl-OPEs. The OPE mixture was also inversely associated with AGD in both sexes. The single-exposure effects of BKMR models were largely consistent with those observed in the GEE models. In addition, alkyl-OPEs, particularly BBOEP, contributed the most to the decreased AGD in girls, while BCIPP contributed the most to the decreased AGD in boys.

CONCLUSIONS

This study provides the first human evidence that prenatal exposure to OPEs is associated with decreased AGD in offspring. The magnitude of these effects may vary depending on the structure of OPEs.

Determinants of organophosphorus pesticide urinary metabolite levels in pregnant women from the CHAMACOS cohort

Organophosphosphorus pesticides (OPs) are widely used as insecticides in agriculture. Human exposure to OPs has been linked to adverse effects including poorer child neurodevelopment, reduced birth weight, altered serum hormone levels, and reduced semen quality. We measured six OP dialkyl phosphate (DAP) metabolites [three dimethyl alkylphosphates (DMs) and three diethyl alkylphosphates (DEs)] in urine samples collected two times during pregnancy (~13 and ~26 weeks gestation) from 594 women participating in the CHAMACOS birth cohort study and resided in an agricultural community in the United States (U.S.) between 1999 and 2000. Previous studies have shown these women have higher OP exposures compared with the general U.S. population. We examined bivariate associations between prenatal DAP metabolite levels and exposure determinants such as age, season, years living in the US, housing characteristics, fruit and vegetable consumption, occupation and residential proximity to agricultural fields. Final multivariable models indicated that season of urine collection was significantly associated (p < 0.01) with specific gravity-adjusted DM, DE and total DAP metabolites; samples collected in fall and winter had higher concentrations than those collected in spring-summer. Specific gravity-adjusted levels of DM and total DAP metabolites were significantly higher in women who had resided in the U.S. for 5 years or less (p < 0.05). Levels of DM metabolites also increased with daily fruit and vegetable servings (p < 0.01), and levels of DE metabolites were higher in residences with poorer housekeeping quality (p < 0.01) and in mothers that worked in agriculture (p < 0.05). These findings suggest that there are multiple determinants of OP exposure in pregnant women.

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.

Associations between organophosphate esters concentrations and markers of liver function in US adolescents aged 12-19 years: A mixture analysis

Liver disease has become a growing health burden, and little is known about the impairment of liver function caused by exposure to organophosphate esters (OPEs) in adolescents aged 12-19 years in the United States. To investigate the relationship between urinary metabolites of OPEs including diphenyl phosphate (DPHP), bis(1,3-dichloro-2-propyl) phosphate (BDCPP), bis(1-chloroethyl) phosphate (BCPP), bis(2-chloroethyl) phosphate (BCEP), and dibutyl phosphate (DBUP) and liver function in US adolescents aged 12-19 years. Liver function tests (LFTs) include aspartate aminotransferase (AST), albumin (ALB), alanine aminotransferase (ALT), alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT), total bilirubin (TBIL), total protein (TP), and AST/ALT. Meanwhile, potential confounding and interaction effects were assessed. The study sample included 592 adolescents aged 12-19 from two consecutive NHANES cycles (2011-2012, 2013-2014). A composite statistical strategy combining traditional linear regression with advanced multi-pollutant models quantile based g-computation (QGC) and eXtreme Gradient Boosting (XGBoost) regression was used to analyze the joint effects of multiple OPEs on liver function indicators, and to describe the interaction between different OPEs in detail. 592 adolescent participants were 15 (14-17) years old, with similar numbers of males and females (304 vs. 288). The analysis results showed that (1) in the linear regression model, individual DPHP, BCEP exposure and ALP changes, BCEP and AST/ALT changes were positively associated. DPHP, BDCPP were negatively associated with TP changes. (2) The combined effects of various OPEs on ALB, ALT, ALP, GGT, TBIL, TP, and AST/ALT were statistically significant. (3) There is no potential interaction between different OPEs. Several OPEs and their combinations are closely related to the 8 LFT indicators. In addition, data suggest that exposure to OPEs in adolescents may be associated with liver damage. Due to limited evidence in the literature and potential limitations of the current study, our findings require more studies to confirm.

Exposure assessment of aryl-organophosphate esters based on specific urinary biomarkers and their associations with reproductive hormone homeostasis disruption in women of childbearing age

The effects of aryl-organophosphate esters (aryl-OPEs) on female reproduction health are still unclear owing to the lack of specific exposure biomarkers. Here, we analyzed the hydroxylated metabolites of three aryl-OPEs (phenyl diphenyl phosphate [TPhP], 2-ethylhexyl diphenyl phosphate [EHDPP], and tricresyl phosphate [TCrP]) and diphenyl phosphate (DPhP) in urine samples from 913 women of childbearing age, and explored the association between exposure to the aryl-OPEs and reproductive hormone levels. The detection frequencies of 2-ethyl-5-hydroxyhexyl diphenyl phosphate (5-OH-EHDPP), phenyl di-p-tolyl phosphate (4-OH-MDTP), and 4-hydroxyphenyl diphenyl phosphate (4-OH-TPhP) were 94.6 %, 93.3 %, and 84.2 %, respectively. Multivariate linear regression analyses revealed that the quartiles of 4-OH-TPhP were positively associated with the progesterone (P4) level (p-trend = 0.008), and the P level in the highest quartile of 5-OH-EHDPP was 7.2 % (95 % CI, 5.7 % to 8.7 %) higher than that in the lowest quartile. The 17β-estradiol levels in the highest quartiles of 4-OH-TPhP and 5-OH-EHDPP were 15.0 % (95 % CI, 13.7 % to16.1 %) and 5.9 % (95 % CI, 15.7 % to 16.1 %) lower than those in the lowest quartiles, respectively. The anti-Müllerian hormone level linearly increased across the quartiles of 4-OH-MDTP (p-trend = 0.036), and the follicle-stimulating hormone exhibited the opposite trend (p-trend = 0.0047). These results indicate that aryl-OPEs may disrupt hormone homeostasis using their specific biomarkers and may negatively affect female reproduction.

Variability and correlations of synthetic chemicals in urine from a New York City-based cohort of pregnant women

Fetal exposure to environmental chemicals has been associated with adverse health outcomes in children and later into adulthood. While several studies have examined correlations and variability of non-persistent chemical exposures throughout pregnancy, many do not capture more recent exposures, particularly in New York City. Our goal was to characterize exposure to phthalates, bisphenols, polycyclic aromatic hydrocarbons, and organophosphate pesticides among pregnant women residing in New York City who enrolled in the New York University Children's Health and Environment Study (NYU CHES) between 2016 and 2018. We measured urinary chemical metabolite concentrations in 671 women at early, mid, and late pregnancy (median 10.8, 20.8, and 29.3 weeks, respectively). We calculated Spearman correlation coefficients among chemical concentrations at each measurement time point. We compared changes in population-level urinary metabolites at each stage using paired Wilcoxon signed-rank tests and calculated intraclass correlation coefficients (ICCs) to quantify intra-individual variability of metabolites across pregnancy. Geometric means and ICCs were compared to nine other pregnancy cohorts that recruited women in 2011 or later as well as nationally reported levels from women of child-bearing age. Compared with existing cohorts, women in NYU CHES had higher geometric means of organophosphate pesticides (Σdiethylphosphates = 28.7 nmol/g cr, Σdimethylphosphates = 57.3 nmol/g cr, Σdialkyl phosphates = 95.9 nmol/g cr), bisphenol S (0.56 μg/g cr), and 2-naphthalene (8.98 μg/g cr). Five PAH metabolites and two phthalate metabolites increased between early to mid and early to late pregnancy at the population level. Spearman correlation coefficients for chemical metabolites were generally below 0.50. Intra-individual exposures varied over time, as indicated by low ICCs (0.22-0.88, median = 0.38). However, these ICCs were often higher than those observed in other pregnancy cohorts. These results provide a general overview of the chemical metabolites measured in NYU CHES in comparison to other contemporary pregnancy cohorts and highlight directions for future studies.

Variability and predictors of urinary organophosphate ester concentrations among school-aged children

Organophosphate esters (OPE) are flame retardants and plasticizers used in a wide range of consumer products. Despite their widespread use, few studies have characterized pediatric exposures. We assessed variability and predictors of OPE exposures in a cohort panel study of 179 predominantly Black school-aged children with asthma in Baltimore City, MD. The study design included up to four seasonal week-long in-home study visits with urine sample collection on days 4 and 7 of each visit (nsamples = 618). We quantified concentrations of 9 urinary OPE biomarkers: bis(2-chloroethyl) phosphate (BCEtp), bis(1-chloro-2-propyl) phosphate, bis(1,3-dichloro-2-propyl) phosphate (BDCPP), di-benzyl phosphate (DBuP), di-benzyl phosphate, di-o-cresylphosphate, di-p-cresylphosphate (DPCP), di-(2-propylheptyl) phthalate (DPHP), 2,3,4,5-tetrabromo benzoic acid. We assessed potential predictors of exposure, including demographic factors, household characteristics, and cleaning behaviors. We calculated Spearman/tetrachoric correlations and intraclass correlation coefficients (ICCs) to examine within-week and seasonal intra-individual variability, respectively. We assessed OPE predictors using linear models for continuous log2 concentrations (BDCPP and DPHP) and logistic models for odds of detection (BCEtP, DBuP, DPCP), with generalized estimating equations to account for repeated measures. For all OPEs, we observed moderate within-week correlations (rs: 0.31-0.63) and weak to moderate seasonal reliability (ICC: 0.18-0.38). BDCPP and DPHP concentrations were higher in the summer compared to other seasons. DPHP concentrations were lower among males than females (%diff: -53.5%; 95% CI: -62.7, -42.0) and among participants spending >12 h/day indoors compared to ≤12 h (%diff: -20.7%; 95% CI: -32.2, -7.3). BDCPP concentrations were lower among children aged 8-10 years compared to 5-7 years (%diff: -39.1%; 95% CI: -55.9, -15.9) and higher among children riding in a vehicle on the day of sample collection compared to those who had not (%diff: 28.5%; 95% CI: 3.4, 59.8). This study is the first to characterize within-week and seasonal variability and identify predictors of OPE biomarkers among Black school-aged children, a historically understudied population.

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.

Urinary organophosphate metabolite concentrations and birth sizes among women conceiving through in vitro fertilization in Shanghai, China

BACKGROUND

Few studies have examined the adverse birth sizes of preconception exposure to organophosphate pesticides (OPs) in women undergoing in vitro fertilization (IVF).

OBJECTIVES

We investigated the relationship of preconception OP exposure with birth sizes among Chinese women undergoing IVF.

METHODS

This study included 302 couples seeking infertility treatment in the China National Birth Cohort Study, from Shanghai, China, who gave birth to singleton infants between 2018 and 2021. Clinical data were collected from medical records. We measured the concentrations of six nonspecific dialkyl phosphates (DAP) metabolites of OPs [diethylthiophosphate (DETP), diethylphosphate (DEP), diethyldithiophosphate (DEDTP), dimethyldithiophosphate (DMTP), dimethylphosphate (DMP), and dimethyldithiophosphate (DMDTP)] in maternal urine. DMDTP and DEDTP were precluded from further analyses due to the low detection rates. Generalized linear models (GLMs) and weighted quantile sum (WQS) regression analyses were performed to examine the individual and joint effects of OP exposures on gestational age, birth weight, body length, and ponderal index. Odder ratio (OR) of preterm birth were estimated using logistic regression models.

RESULTS

Women in the highest as compared with lowest quartile of DEP had shorter gestational age (β = - 0.68; 95% CI = -1.24, -0.11). The association was modified by sex, with boys showing larger decreases in gestational age (β = - 0.86; 95% CI = -1.60, -0.13). No associations were found between other DAP metabolites and birth sizes. Results from linear models with individual DAP metabolites were corroborated by the WQS regression where DEP had the largest contribution to the overall mixture effect on gestational age (weight = 0.70). Moreover, DEP concentration was associated with an elevated risk of preterm birth (OR = 1.35, 95% CI = 1.11, 2.25).

CONCLUSION

Preconception DEP concentration was associated with shortened gestational age and increased risk of preterm birth, and the association was more pronounced among boys than girls.

Exposure of men living in the greater Montreal area to organophosphate esters: Association with hormonal balance and semen quality

Exposure to organophosphate esters (OPEs) is extensive, yet few studies have investigated their association with hormone levels or semen quality. Here, we studied the association between urinary concentrations of OPEs and their metabolites with hormone levels and semen parameters in men (n = 117) predominantly in the 20-29 years age range who were recruited from the greater Montreal area between 2009 and 2012. Urine, serum, and semen samples were analyzed for OPEs, hormones, and semen quality, respectively. Bis(2-ethylhexyl) phosphate (BEHP), bis(2,4-di-tert-butylphenyl) hydrogen phosphate (B2,4DtBPP), tris(2-chloroisopropyl) phosphate (TCIPP), diphenyl phosphate (DPHP), bis (2-butoxyethyl) phosphate (BBOEP) and di-cresyl phosphate (DCPs) were detected in urine at a frequency ≥ 95%. The highest geometric mean concentration was observed for DPHP (18.54 ng/mL) and the second highest was B2,4DtBPP (6.23 ng/mL). Associations between a doubling in analyte concentrations in urine and hormone levels and semen quality parameters were estimated using multivariable linear regression. B2,4DtBPP levels were positively associated with total T3 (β = 0.09; 95% CI: 0.01, 0.17). DPHP was inversely associated with estradiol (β = -2.56; 95% CI: -5.00, -0.17), and TCIPP was inversely associated with testosterone (β = -0.78; 95% CI: -1.40, -0.17). Concentrations of BCIPP were inversely associated with sperm concentrations (β = -7.76; 95% CI: -14.40, -0.61), progressive motility (β = - 4.98; 95% CI: -8.71, -1.09), and the sperm motility index (β = -9.72; 95% CI: -17.71, -0.96). In contrast, urinary DPHP concentrations were positively associated with the sperm motility (β = 4.37; 95% CI: 0.76, 8.12) and fertility indices (β = 6.64; 95% CI: 1.96, 11.53). Thus, OPE detection rates were high and exposure to several OPEs was associated with altered hormone levels and semen parameters. The possibility that OPEs affect male reproduction warrants further investigation.

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.

Human Exposure to Chlorinated Organophosphate Ester Flame Retardants and Plasticizers in an Industrial Area of Shenzhen, China

Human exposure to organophosphate esters (OPEs) is more pervasive in industrial areas manufacturing OPE-related products. OPE exposure is of great concern due to its associations with adverse health effects, while studies on OPE exposure in industrial districts are scarce. This study aimed to assess human exposure to OPEs in a typical industrial area producing large amounts of OPE-related products in Shenzhen, China. Tris (2-chloroethyl)-phosphate (TCEP), tris (2-chloroisopropyl) phosphate (TCPP) and other common OPEs were analyzed in urine (n = 30) and plasma (n = 21) samples. Moreover, we measured five OPE metabolites (mOPEs) in plasma samples (n = 21). The results show that TCPP and TCEP are dominant compounds, with moderate to high levels compared with those reported in urine and plasma samples from other regions. In addition, di-n-butyl phosphate (DnBP) and diethyl phosphite (DEP) were frequently detected in plasma samples and could be considered as biomarkers. Risk assessment revealed a moderate to high potential health risk from TCEP exposure. Our results provide basic data for human exposure to OPEs in industrial areas and call for the prevention and mitigation of industrial chlorinated OPE pollution.

Organophosphate and Organohalogen Flame-Retardant Exposure and Thyroid Hormone Disruption in a Cross-Sectional Study of Female Firefighters and Office Workers from San Francisco

Occupational exposures to flame retardants (FRs), a class of suspected endocrine-disrupting compounds, are of health concern for firefighters. We sought to characterize exposure to FR compounds and evaluate their association with thyroid hormone levels, a biomarker of early effect, in female firefighters and office workers in San Francisco. In a cross-sectional study, we measured replacement organophosphate and organohalogen FRs in spot urine samples from firefighters (N = 86) and office workers (N = 84), as well as total thyroxine (T4) and thyroid-stimulating hormone in plasma for 84 firefighters and 81 office workers. Median bis(1,3-dichloro-2-propyl)phosphate (BDCPP) levels were 5 times higher in firefighters than office workers. Among firefighters, a doubling of BDCPP was associated with a 2.88% decrease (95% confidence interval -5.28, -0.42) in T4. We did not observe significant associations between FRs and T4 among office workers. In the full group, intermediate body mass index and a college education were associated with higher FR levels. The inverse association observed between FRs and T4 coupled with the lack of studies on women workers and evidence of adverse health effects from FR exposure─including endocrine disruption and breast cancer risk─warrant further research on occupational exposures and identification of opportunities for exposure reduction.

Gestational Exposure to Organophosphate Pesticides and Longitudinally Assessed Behaviors Related to Attention-Deficit/Hyperactivity Disorder and Executive Function

The brain’s prefrontal cortex directs higher-order cognitive and behavioral processes that are important for attention, working memory, and inhibitory control. We investigated whether gestational exposure to organophosphate (OP) pesticides was associated with these abilities in childhood and early adolescence. Between 1999 and 2000, we enrolled pregnant women in a birth cohort drawn from an agricultural region of California. We measured dialkyl phosphate (DAP) metabolites of OP pesticides in maternal pregnancy urine samples (13 and 26 weeks) and estimated associations with behaviors related to attention-deficit/hyperactivity disorder and executive function, assessed longitudinally; 351 families provided neurodevelopmental outcome data at any point when the child was aged 7–12 years. We assessed function across multiple dimensions (e.g., working memory, attention), methods (e.g., behavior reports, child assessment), and reporters (e.g., mothers, teachers, child self-reports). Higher gestational DAP concentrations were consistently associated with behaviors related to attention-deficit/hyperactivity disorder and executive function. For example, a 10-fold increase in gestational DAP concentration was associated with poorer longitudinally assessed Behavior Rating Inventory of Executive Function scores, as reported by mothers (β = 4.0 (95% confidence interval: 2.1, 5.8); a higher score indicates more problems), and Weschler Intelligence Scale for Children—Fourth Edition Working Memory scores (a 3.8-point reduction; β = −3.8 (95% confidence interval: −6.2, −1.3)). Reducing gestational exposure to OP pesticides through public health policy is an important goal.

Beyond Cholinesterase Inhibition: Developmental Neurotoxicity of Organophosphate Ester Flame Retardants and Plasticizers

BACKGROUND

To date, the toxicity of organophosphate esters has primarily been studied regarding their use as pesticides and their effects on the neurotransmitter acetylcholinesterase (AChE). Currently, flame retardants and plasticizers are the two largest market segments for organophosphate esters and they are found in a wide variety of products, including electronics, building materials, vehicles, furniture, car seats, plastics, and textiles. As a result, organophosphate esters and their metabolites are routinely found in human urine, blood, placental tissue, and breast milk across the globe. It has been asserted that their neurological effects are minimal given that they do not act on AChE in precisely the same way as organophosphate ester pesticides.

OBJECTIVES

This commentary describes research on the non-AChE neurodevelopmental toxicity of organophosphate esters used as flame retardants and plasticizers (OPEs). Studies in humans, mammalian, nonmammalian, and in vitro models are presented, and relevant neurodevelopmental pathways, including adverse outcome pathways, are described. By highlighting this scientific evidence, we hope to elevate the level of concern for widespread human exposure to these OPEs and to provide recommendations for how to better protect public health.

DISCUSSION

Collectively, the findings presented demonstrate that OPEs can alter neurodevelopmental processes by interfering with noncholinergic pathways at environmentally relevant doses. Application of a pathways framework indicates several specific mechanisms of action, including perturbation of glutamate and gamma-aminobutyric acid and disruption of the endocrine system. The effects may have implications for the development of cognitive and social skills in children. Our conclusion is that concern is warranted for the developmental neurotoxicity of OPE exposure. We thus describe important considerations for reducing harm and to provide recommendations for government and industry decision makers. https://doi.org/10.1289/EHP9285.

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.

Associations between polyfluoroalkyl substance and organophosphate flame retardant exposures and telomere length in a cohort of women firefighters and office workers in San Francisco

BACKGROUND

Environmental chemical exposures can affect telomere length, which in turn has been associated with adverse health outcomes including cancer. Firefighters are occupationally exposed to many hazardous chemicals and have higher rates of certain cancers. As a potential biomarker of effect, we assessed associations between chemical exposures and telomere length in women firefighters and office workers from San Francisco, CA.

METHODS

We measured serum concentrations of polyfluoroalkyl substances (PFAS), urinary metabolites of flame retardants, including organophosphate flame retardants (OPFRs), and telomere length in peripheral blood leukocytes in women firefighters (N = 84) and office workers (N = 79) who participated in the 2014-15 Women Workers Biomonitoring Collaborative. Multiple linear regression models were used to assess associations between chemical exposures and telomere length.

RESULTS

Regression results revealed significant positive associations between perfluorooctanoic acid (PFOA) and telomere length and perfluorooctanesulfonic acid (PFOS) and telomere length among the whole cohort. Models stratified by occupation showed stronger and more significant associations among firefighters as compared to office workers. Among firefighters in models adjusted for age, we found positive associations between telomere length and log-transformed PFOA (β (95%CI) = 0.57(0.12, 1.02)), PFOS (0.44 (0.05, 0.83)), and perfluorodecanoic acid (PFDA) (0.43 (0.02, 0.84)). Modeling PFAS as categories of exposure showed significant associations between perfluorononanoic acid (PFNA) and telomere length among firefighters. Significant associations between OPFR metabolites and telomere length were seen for bis (1,3-dichloro-2-propyl) phosphate (BDCPP) and telomere length among office workers (0.21(0.03, 0.40)) and bis (2-chloroethyl) phosphate (BCEP) and telomere length among firefighters (- 0.14(- 0.28, - 0.01)). For OPFRs, the difference in the direction of effect by occupational group may be due to the disparate detection frequencies and concentrations of exposure between the two groups and/or potential unmeasured confounding.

CONCLUSION

Our findings suggest positive associations between PFAS and telomere length in women workers, with larger effects seen among firefighters as compared to office workers. The OPFR metabolites BDCPP and BCEP are also associated with telomere length in firefighters and office workers. Associations between chemical exposures and telomere length reported here and by others suggest mechanisms by which these chemicals may affect carcinogenesis and other adverse health outcomes.

A recurring disease outbreak following litchi fruit consumption among children in Muzaffarpur, Bihar-A comprehensive investigation on factors of toxicity

Litchi fruits are a nutritious and commercial crop in the Indian state of Bihar. Litchi fruit contains a toxin, methylene cyclopropyl-glycine (MCPG), which is known to be fatal by causing encephalitis-related deaths. This is especially harmful when consumed by malnourished children. The first case of litchi toxicity was reported in Bihar in 2011. A similar event was recorded in 2014 among children admitted to the Muzaffarpur government hospital, Bihar. Litchi samples sent to ICMR-NIN were analyzed and MCPG was found to be present in both the pulp and seed of the fruit. Diethyl phosphate (DEP) metabolites were found in the urine samples of children who had consumed litchi fruit from this area indicating exposure to pesticide. The presence of both MCPG in litchi and DEP metabolites in urine samples highlights the need to conduct a comprehensive investigation that examines all factors of toxicity.

Maternal urinary concentrations of organophosphate ester metabolites: associations with gestational weight gain, early life anthropometry, and infant eating behaviors among mothers-infant pairs in Rhode Island

BACKGROUND

Organophosphate esters (OPEs)-used as flame retardants and plasticizers-are associated with adverse pregnancy outcomes such as reduced fecundity and live births and increased preterm delivery. OPEs may interfere with growth and metabolism via endocrine-disruption, but few studies have investigated endocrine-related outcomes. The objective of this pilot study (n = 56 mother-infant pairs) was to evaluate associations of OPEs with gestational weight gain (GWG), gestational age at delivery, infant anthropometry, and infant feeding behaviors.

METHODS

We quantified OPE metabolites (bis-2-chloroethyl phosphate [BCEP], bis (1,3-dichloro-2-propyl) phosphate [BDCPP], diphenyl phosphate [DPHP]) in pooled maternal spot urine collected throughout pregnancy (~ 12, 28, and 35 weeks' gestation). We obtained maternal sociodemographic characteristics from questionnaires administered at enrollment and perinatal characteristics from medical record abstraction. Trained research assistants measured infant weight, length, head and abdominal circumferences, and skinfold thicknesses at birth and 6 weeks postpartum. Mothers reported infant feeding behavior via the Baby Eating Behavior Questionnaire (BEBQ). Using multiple linear regression, we assessed associations of log2-transformed maternal urinary OPE metabolites with GWG, gestational age at delivery, infant anthropometry at birth, weekly growth rate, and BEBQ scores at 6 weeks postpartum. We used linear mixed effects (LME) models to analyze overall infant anthropometry during the first 6 weeks of life. Additionally, we considered effect modification by infant sex.

RESULTS

We observed weak positive associations between all OPE metabolites and GWG. In LME models, BDCPP was associated with increased infant length (β = 0.44 cm, 95%CI = 0.01, 0.87) and weight in males (β = 0.14 kg, 95%CI = 0.03, 0.24). BDCPP was also associated with increased food responsiveness (β = 0.23, 95%CI = 0.06, 0.40). DPHP was inversely associated with infant abdominal circumference (β = - 0.50 cm, 95%CI = - 0.86, - 0.14) and female weight (β = - 0.19 kg, 95%CI = - 0.36, - 0.02), but positively associated with weekly growth in iliac skinfold thickness (β = 0.10 mm/wk., 95%CI = 0.02, 0.19). Further, DPHP was weakly associated with increased feeding speed. BCEP was associated with greater infant thigh skinfold thickness (β = 0.34 mm, 95%CI = 0.16, 0.52) and subscapular skinfold thickness in males (β = 0.14 mm, 95%CI = 0.002, 0.28).

CONCLUSIONS

Collectively, these findings suggest that select OPEs may affect infant anthropometry and feeding behavior, with the most compelling evidence for BDCPP and DPHP.

Urinary Organophosphate Metabolite Concentrations and Pregnancy Outcomes among Women Conceiving through in Vitro Fertilization in Shanghai, China

BACKGROUND

Animal studies suggest that pesticide exposure elicits endocrine changes, increases embryo implantation failure, and decreases litter size. However, only a few epidemiological studies have evaluated the effects of pesticides on the outcomes of in vitro fertilization (IVF) pregnancies.

OBJECTIVES

This study examined the associations between preconception organophosphate pesticides (OP) exposure and pregnancy outcomes among women undergoing IVF in a Chinese population.

METHODS

This study included 522 women with infertility who underwent IVF. Women were recruited from a prospective study, the China National Birth Cohort (CNBC), from Shanghai, China, between July 2017 and December 2018. Demographic and clinical information were collected from medical records and through questionnaires. Preconception exposure to OP was assessed by measuring six nonspecific dialkylphosphate (DAP) metabolites [diethylthiophosphate (DETP), diethylphosphate (DEP), diethyldithiophosphate (DEDTP), dimethylthiophosphate (DMTP), dimethylphosphate (DMP), dimethyldithiophosphate (DMDTP)] in urine samples collected at recruitment. Generalized estimating equation (GEE) models were used to evaluate the associations between OP and pregnancy outcomes.

RESULTS

Compared with women in the lowest quartile (Q1) of individual DEP and Σ4DAP (the sum of DMP, DMTP, DEP, and DETP), women in the highest quartile (Q4) had lower odds of successful implantation, clinical pregnancy, and live birth, and most of the negative trends were significant (p-trends<0.05). There were no significant associations between urinary DAP concentrations and early IVF outcomes, including total and mature oocyte counts, best embryo quality, fertilization, E2 trigger levels, and endometrial wall thickness.

CONCLUSION

Preconception OP exposure was inversely associated with successful implantation, clinical pregnancy, and live birth in women who underwent IVF. https://doi.org/10.1289/EHP7076.

Predictors of Urinary Pyrethroid and Organophosphate Compound Concentrations among Healthy Pregnant Women in New York

Our study aimed to investigate dietary and non-dietary predictors of exposure to pyrethroids, organophosphates pesticides and 2,4-D herbicide in two cohorts of pregnant women in New York City: 153 women from the Thyroid Disruption and Infant Development (TDID) cohort and 121 from the Sibling/Hermanos Cohort(S/H). Baseline data on predictors were collected from the women at time of recruitment. We used three different modeling strategies to address missing data due to biomarker values below the limit of detection (<LOD): (1) logistic regression models with biomarkers categorized as (<median, ≥median); (2) linear regression models, imputing the <LOD values with (LOD/√2); (3) regression models, considering <LOD values as left-censored. Generally, all three models identified similar predictors of exposure. We found that ethnicity, higher income and education predicted higher concentrations of most of the biomarkers in both cohorts. Mothers who consumed processed meat in the TDID cohort, and broiled, barbequed food or burgers in the S/H cohort, tended to have lower concentrations of organophosphates and 2,4-D. The choice of modeling led to a few different predictors identified, and the selection of modeling strategy should be based on the study question.

Predictors and reproducibility of urinary organophosphate ester metabolite concentrations during pregnancy and associations with birth outcomes in an urban population

BACKGROUND

Organophosphate esters (OPEs) are synthetic chemicals used as flame retardants and plasticizers in a variety of goods. Despite ubiquitous human exposures and laboratory evidence that prenatal OPE exposures may disrupt offspring metabolism, perinatal studies of OPE health effects are limited. The objectives of this study were to: 1) Determine predictors and reproducibility of urinary OPE biomarker concentrations during pregnancy, and 2) Estimate the relation of prenatal OPE exposures with birth outcomes and cord blood adipokine and insulin concentrations.

METHODS

We analyzed five OPE metabolites in urine samples collected at up to three visits during pregnancy from 90 women enrolled in the ORigins of Child Health And Resilience in Development (ORCHARD) pregnancy cohort in Baltimore, MD from 2017 to 2019. To quantify the variability of metabolite concentrations during pregnancy, we calculated intraclass correlation coefficients (ICCs) for each metabolite using mixed effects regression models. Using self-reported questionnaire data collected during gestation, we assessed possible sociodemographic and environmental/behavioral predictors of each OPE metabolite using generalized estimating equations to account for repeated exposure measures. We ascertained birth outcomes of 76 offspring from medical records, including weight-for-gestational age, length, ponderal index, and gestational age. In a subset of 37 infants, we measured cord blood concentrations of leptin, adiponectin, and insulin. To account for repeated exposure measures, we used linear structural equation models to assess the relations of standard deviation (SD) increases in prenatal OPE metabolite factor scores with continuous birth outcomes and cord blood biomarker concentrations.

RESULTS

ICCs ranged from 0.09 for isopropylphenyl-phenyl phosphate (ip-PPP) to 0.59 for bis(1,3-dichloro-2-propyl) phosphate (BDCIPP). We observed little consistency in environmental or behavioral predictors of OPE exposures, although concentrations were generally lower for samples collected in the afternoon compared to morning and winter compared to other seasons. In adjusted analyses, a SD increase in BDCIPP concentration was associated with a 0.06 g/cm3 (95% CI: 0.00, 0.12) greater ponderal index. A SD increase in BDCIPP was associated with a 0.37 (95% CI: - 0.62, - 0.13) SD lower insulin concentration and 0.24 (95% CI: - 0.39, - 0.08) SD lower leptin concentration. Other OPEs were not associated with infant outcomes.

CONCLUSIONS

These findings suggest some OPEs may be metabolic disruptors warranting investigation in larger studies.

Rapid and sensitive analytical procedure for biomonitoring of organophosphate pesticide metabolites in human urine samples using a vortex-assisted salt-induced liquid-liquid microextraction technique coupled with ultra-high-performance liquid chromatography/tandem mass spectrometry

RATIONALE

Organophosphate pesticides (OPPs) are the most commonly used insecticides around the world in various agricultural and domestic practices, and humans are frequently exposed to these hazardous insecticides that can lead to several chronic health effects. Therefore, a fast and sensitive analytical method is required for biomonitoring the markers of OPPs in humans for exposure estimation. In this study, a fast and sensitive analytical procedure was developed for the determination of the metabolites of OPPs in human urine samples.

METHODS

Metabolites of OPPs were extracted from 2 mL of urine sample using a novel vortex-assisted salt-induced liquid-liquid microextraction (VA-SI-LLME) technique, and the preconcentrated metabolites were analyzed by ultra-high-performance liquid chromatography/tandem mass spectrometry (UHPLC/MS/MS). Various factors affecting the efficiency of VA-SI-LLME were thoroughly investigated.

RESULTS

The metabolites of OPPs exhibited very good linearity over the concentration range between 0.05 and 50 ng mL^-1 with coefficient (r² ) values ranging between 0.9986 and 0.9999. The method showed excellent sensitivity with detection limits ranging from 0.01 to 0.03 ng mL^-1 and quantification limits from 0.03 to 0.05 ng mL^-1 . The developed method was applied to the analysis of real samples and the recoveries ranged between 85.0 and 114.1% with related standard deviations <5%.

CONCLUSIONS

The results showed the VA-SI-LLME/UHPLC/MS/MS method to be a simple, rapid, sensitive, and selective analytical procedure for the biomonitoring of the metabolites of OPPs in humans. This efficient and cost-effective analytical method could be a potential alternative method for the biomonitoring of the metabolites of pesticides in humans.