Demographic and dietary risk factors in relation to urinary metabolites of organophosphate flame retardants in toddlers

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.

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, bioaccumulation, and risk assessment of organophosphate flame retardants in crayfish in the middle and lower reaches of the Yangtze River

Organophosphate flame retardants (OPFRs), a novel class of persistent pollutants, are widely distributed in the environment, and their potential health risks have garnered significant global attention in recent years. Crayfish is a popular freshwater crustacean product in China primarily sourced from the middle and lower reaches of the Yangtze River. The purpose of this study was to investigate the exposure levels of OPFRs in crayfish, assess the health and safety risks associated with crayfish consumption, and explore the bioaccumulation of OPFRs in environmental water and sediment on crayfish. Ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) was employed to analyze 7 common OPFRs in 106 crayfish samples and 76 environmental samples. The results revealed that OPFRs were detected at a high frequency of 100 % in crayfish, with tripropyl phosphate (TPP) being the predominant pollutant found in edible portions while also exhibiting secondary contamination within the crayfish food chain. Monte Carlo modeling combined with @risk risk assessment software demonstrated that TPP present in crayfish muscles had the most substantial impact on health effects, however, overall OPFR exposure did not pose significant risks to human health. Furthermore, analysis of OPFRs bioenrichment ability indicated that crayfish predominantly accumulated these compounds within their edible parts from surrounding environmental water sources, particularly highlighting TPP's potential for bioaccumulation.

Prenatal exposures to organophosphate ester metabolites and early motor development in the MADRES cohort

Organophosphate esters (OPEs) are increasingly considered neurotoxicants which may impact gross and fine motor development. We evaluated associations between prenatal OPE exposures and infant motor development. Third trimester urinary concentrations of nine OPE metabolites were measured in 329 mother-infant dyads participating in the Maternal And Developmental Risks from Environmental and Social Stressors (MADRES) cohort. Child gross and fine motor development at 6, 9, 12, and 18-months were assessed with the Ages and Stages Questionnaire-3 (ASQ-3) and operationalized in models using dichotomous instrument-specific cutoffs for typical motor development. Five OPE metabolites with >60% detection were specific-gravity-adjusted, natural log-transformed, and modeled continuously, while four metabolites with <60% detection were modeled dichotomously (detected/not-detected). We fit mixed effects logistic regression between OPE metabolites and fine/gross motor development and assessed sex-specific effects using a statistical interaction term and sex-stratified models. Among children, 31% and 23% had gross and fine motor scores, respectively, below the ASQ-3 at-risk cutoffs at least once across infancy. A doubling in prenatal diphenyl phosphate (DPHP) exposure was associated with 26% increased odds of potential fine motor delays (ORfine = 1.26, 95% CI: 1.02, 1.57, p = 0.04). We also observed significant interactions by infant sex for associations of detected dipropyl phosphate (DPRP) with gross motor development (pinteraction = 0.048) and detected bis(1-chloro-2-propyl) phosphate (BCIPP) with fine motor development (pinteraction = 0.02). Females had greater odds of potential motor delays for both detected DPRP (females vs males ORgross (95% CI) = 1.48 (0.71, 3.09), p = 0.30 vs 0.27 (0.06, 1.29), p = 0.10) and detected BCIPP (females vs males ORfine (95% CI) = 2.72 (1.27, 5.85), p = 0.01 vs 0.76 (0.31, 1.90), p = 0.56). There were no other significant associations between other metabolites and motor development, despite similar patterns. We found evidence of adverse effects of prenatal OPE exposures on infant motor development with greater adverse effects among female infants with some OPE metabolites.

Toxic trespassers: Uncovering phthalates and organophosphate flame retardants in children's rooms and their health implications

Organophosphate flame retardants (OPEs) and phthalates have garnered significant attention due to their widespread presence in indoor environments. Many recent investigations have reported extensive contamination of indoor dust, air, children's toys, and other environmental compartments with these chemicals. This research aimed to analyze OPEs and phthalates in air (PM10) and dust samples collected from the bedrooms of children (N = 30) residing in various households in Jeddah, Saudi Arabia. High mean levels (ng/g) of phthalates namely DEHP (1438600) and DnBP (159200) were found in indoor dust while TPhP (5620) was the major OPEs in indoor dust. Similarly, DEHP and DnBP were the predominant phthalates in PM10 samples, exhibiting mean levels of 560 and 680 ng/m3, respectively. However, TCPP was the main OPEs with average levels of 72 ng/m3 in PM10 samples. The majority of individual phthalates and OPEs were detected in 90-100 % of the dust samples, whereas in PM10 samples, their presence ranged from 25 % to 100 %. The concentrations of OPEs were notably greater than those of PBDEs and other BFRs previously reported in these samples, suggesting their broader use than alternative BFRs. The estimated long-term non-carcinogenic risk, hazardous index (HI) and daily exposure via dust for children was above threshold levels for DEHP. On the other hand, the cumulative risk of cancer was below the concerning levels. Further research is required to explore diverse groups of chemicals in indoor microenvironments particularly significant for children, such as kindergartens, primary schools, and their rooms at home.

Developmental organophosphate flame retardant exposure disrupts adult hippocampal neurogenesis in Wistar rats

Organophosphate flame retardant (OPFR) contamination is ubiquitous and bio-monitoring studies have shown that human exposure is widespread and may be unavoidable. OPFRs bear structural similarities to known neurotoxicants such as organophosphate insecticides and have been shown to have both endocrine disrupting and developmental neurotoxic effects. The perinatal period in rodents represents a critical period in the organization of the developing nervous system and insults during this time can impart profound changes on the trajectory of neural development and function, lasting into adulthood. Adult hippocampal neurogenesis (AHN) facilitates dentate gyrus function and broader hippocampal circuit activity in adults; however, the neurogenic potential of this process in adulthood is vulnerable to disruption by exogenous factors during early life. We sought to assess the impact of OPFRs on AHN in offspring of dams exposed during gestation and lactation. Results indicate that developmental OPFR exposure has significant, sex specific impacts on multiple markers of AHN in the dentate gyrus of rats. In males, OPFR exposure significantly reduced the number of neural progenitors the number of new/immature neurons and reduced dentate gyrus volume. In females, exposure increased the number of neural progenitors, decreased the number of new/immature neurons, but had no significant effect on dentate gyrus volume. These results further elucidate the developmental neurotoxic properties of OPFRs, emphasize the long-term impact of early life OPFR exposure on neural processes, and highlight the importance of including sex as a biological variable in neurotoxicology research.

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.

Levels of organophosphate flame retardants and their metabolites among 391 volunteers in Taiwan: difference between adults and children

Background

Organophosphate flame retardants (OPFRs) are ubiquitous in the environment. The compositions and concentrations of different OPFRs metabolites vary in different environments depending on different human activities. The objective of the present study was to evaluate the exposure of different age groups to OPFRs in Taiwan.

Methods

Volunteers provided urine samples and responded to questionnaires including demographic factors, underlying disease, lifestyle information, and occupation from October 2021 to January 2022. OPFR measurements were performed using a Waters Acquity Ultra-Performance Liquid Chromatography system coupled with a Waters Xevo TQ-XS mass spectrometer.

Results

A total of 391 volunteers (74 children and 317 adults) were enrolled in this study. The concentrations (presented as μg/g creatinine) of bis(1,3-dichloro-2-propyl) phosphate (BDCPP, p = 0.029) and tri-n-butyl phosphate (TNBP, p = 0.008) were higher in the adult group, while the concentrations of bis-2-chloroethyl phosphate (BCEP, p = 0.024), diphenyl phosphate (DPHP, p < 0.001), tris(1,3-dichloro-2-propyl) phosphate (TDCPP, p = 0.009), and Tris(2-butoxyethyl) phosphate (TBEP, p = 0.007) were higher in the child group. Compared with school age children (>6 years), the concentration of di(2-n-butoxyethyl) phthalate (DBEP, 1.14 vs. 0.20 μg/g creatinine, p = 0.001), DPHP (1.23 vs. 0.54 μg/g creatinine, p = 0.036), TBEP (1.63 vs. 0.29 μg/g creatinine, p < 0.001), and the sum of OPFR metabolites (ΣOPFRs, 6.58 vs. 2.04 μg/g creatinine, p < 0.001) were statistically higher in preschool-aged children. After adjusting for confounding factors, pre-school age [odds ratio (OR): 4.579, 95% confidence interval (CI): 1.389-13.115] and current smoker (OR: 5.328, 95%CI: 1.858-14.955) were independently associated with the risk of ΣOPFRs higher than 90 percentile.

Conclusion

This study revealed the distribution of different OPFRs metabolites in children and adults. DBEP, DPHP, TBEP, and ΣOPFR were higher in preschool-aged children. Pre-school age and current smoking status were independent risk factors for ΣOPFRs higher than 90 percentile.

Frequency of urinary pesticides in children: a scoping review

Pesticides are any mix of ingredients and substances used to eliminate or control unwanted vegetable or animal species recognized as plagues. Its use has been discussed in research due to the scarcity of strong scientific evidence about its health effects. International literature is still insufficient to establish a global recommendation through public policy. This study aims to explore international evidence of the presence of pesticides in urine samples from children and their effects on health through a scoping review based on the methodology described by Arksey and O'Malley. The number of articles resulting from the keyword combination was 454, and a total of 93 manuscripts were included in the results and 22 were complementary. Keywords included in the search were: urinary, pesticide, children, and childhood. Children are exposed to pesticide residues through a fruit and vegetable intake environment and household insecticide use. Behavioral effects of neural damage, diabetes, obesity, and pulmonary function are health outcomes for children that are commonly studied. Gas and liquid chromatography-tandem mass spectrometry methods are used predominantly for metabolite-pesticide detection in urine samples. Dialkylphosphates (DAP) are common in organophosphate (OP) metabolite studies. First-morning spot samples are recommended to most accurately characterize OP dose in children. International evidence in PubMed supports that organic diets in children are successful interventions that decrease the urinary levels of pesticides. Several urinary pesticide studies were found throughout the world's population. However, there is a knowledge gap that is important to address (public policy), due to farming activities that are predominant in these territories.

Urinary levels of organophosphate flame retardants metabolites in a young population from Southern Taiwan and potential health effects

Background

Organophosphate flame retardants (OPFRs) are widely distributed in the environment and their metabolites are observed in urine, but little is known regarding OPFRs in a broad-spectrum young population from newborns to those aged 18 years.

Objectives

Investigate urinary levels of OPFRs and OPFR metabolites in Taiwanese infants, young children, schoolchildren, and adolescents within the general population.

Methods

Different age groups of subjects (n=136) were recruited from southern Taiwan to detect 10 OPFR metabolites in urine samples. Associations between urinary OPFRs and their corresponding metabolites and potential health status were also examined.

Results

The mean level of urinary Σ10 OPFR in this broad-spectrum young population is 2.25 μg/L (standard deviation (SD) of 1.91 μg/L). Σ10 OPFR metabolites in urine are 3.25 ± 2.84, 3.06 ± 2.21, 1.75 ± 1.10, and 2.32 ± 2.29 μg/L in the age groups comprising of newborns, 1-5 year-olds, 6-10 year-olds, and 11-18 year-olds, respectively, and borderline significant differences were found in the different age groups (p=0.125). The OPFR metabolites of TCEP, BCEP, DPHP, TBEP, DBEP, and BDCPP predominate in urine and comprise more than 90% of the total. TBEP was highly correlated with DBEP in this population (r=0.845, p<0.001). The estimated daily intake (EDI) of Σ5OPFRs (TDCPP, TCEP, TBEP, TNBP, and TPHP) was 2,230, 461, 130, and 184 ng/kg bw/day for newborns, 1-5 yr children, 6-10 yr children, and 11-17 yr adolescents, respectively. The EDI of Σ5OPFRs for newborns was 4.83-17.2 times higher than the other age groups. Urinary OPFR metabolites are significantly correlated with birth length and chest circumference in newborns.

Conclusion

To our knowledge, this is the first investigation of urinary OPFR metabolite levels in a broad-spectrum young population. There tended to be higher exposure rates in both newborns and pre-schoolers, though little is known about their exposure levels or factors leading to exposure in the young population. Further studies should clarify the exposure levels and factor relationships.

Sex-specific effects of prenatal organophosphate ester (OPE) metabolite mixtures and adverse infant birth outcomes in the maternal and developmental risks from environmental and social stressors (MADRES) pregnancy cohort

BACKGROUND

Organophosphate esters (OPEs) are used as flame retardants and plasticizers in various consumer products. Limited prior research suggests sex-specific effects of prenatal OPE exposures on fetal development. We evaluated overall and sex-specific associations between prenatal OPE exposures and gestational age (GA) at birth and birthweight for gestational age (BW for GA) z-scores among the predominately low-income, Hispanic MADRES cohort.

METHODS

Nine OPE metabolite concentrations were measured in 421 maternal urine samples collected during a third trimester visit (GA = 31.5 ± 2.0 weeks). We examined associations between single urinary OPE metabolites and GA at birth and BW for GA z-scores using linear regression models and Generalized Additive Models (GAMs) and effects from OPE mixtures using Bayesian Kernel Machine Regression (BKMR). We also assessed sex-specific differences in single metabolite analyses by evaluating statistical interactions and stratifying by sex.

RESULTS

We did not find significant associations between individual OPE metabolites and birth outcomes in the full infant sample; however, we found that higher bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) was associated with earlier GA at birth among male infants (p = 0.04), and a nonlinear, inverted U-shape association between the sum of dibutyl phosphate and di-isobutyl phosphate (DNBP + DIBP) and GA at birth among female infants (p = 0.03). In mixtures analysis, higher OPE metabolite mixture exposures was associated with lower GA at birth, which was primarily driven by female infants. No associations were observed between OPE mixtures and BW for GA z-scores.

CONCLUSION

Higher BDCIPP and DNBP + DIBP concentrations were associated with earlier GA at birth among male and female infants, respectively. Higher exposure to OPE mixtures was associated with earlier GA at birth, particularly among female infants. However, we saw no associations between prenatal OPEs and BW for GA. Our results suggest sex-specific impacts of prenatal OPE exposures on GA at birth.

Occurrence of organophosphorus esters in outdoor air fine particulate matter and comprehensive assessment of human exposure: A global systematic review

Organophosphate esters (OPEs) are widely used in various industrial items, including plastics, textiles, construction materials, electronics, and auto parts. Several studies have investigated the concentration of OPE compounds in the air, where different compounds have been measured. This systematic review aims to investigate and summarize the relationship between exposure concentrations of OPEs in outdoor air and health risk for different OPE compounds, and correlations between OPE compounds in emission sources. PubMed, Scopus, Embase, Web of Science, and Google Scholar were searched from January 2000 to September 2021 to identify relevant research. The quality of the studies was assessed using the OHAT risk of bias tool. Spearman's correlation and principal component analysis (PCA) were used to analyze the results and correlation between OPE compounds. A total of 7669 manuscripts were found from the search in 5 databases. Finally, 46 studies were included in the systematic review. According to the median concentrations in the studies that were included, Tris(1-chloro-2-propyl) phosphate (TCIPP) (25%), trimethylphenyl phosphate(TMPP) (19%), Tri-iso-butyl phosphate (TiBP) (12%), Triphenyl phosphate (TPHP) (9%) and Tris(2-chloroethyl) phosphate (TCEP) (8%) had the greatest concentrations of OPEs overall. The cumulative contribution of the two main factors, F1 and F2, from the principal component analysis (PCA) results is 49.81%. The EDI value for the compounds is TCEP > TCIPP > TiBP > TMPP > 2-Ethylhexyl diphenyl phosphate (EHDPP) > TPHP > Tri(2-Ethylhexyl) phosphate (TEHP) > Tri-m-cresyl phosphate (mTCP) > Tris(1, 3-dichloro-isopropyl) phosphate (TDCPP) > Tri-n-butyl phosphate (TnBP). The total amount of non-carcinogenic risk (HQ) was for children > infants > adults. The highest value of HQ was for TCEP, TCIPP, and TMPP, respectively. The highest carcinogenic risk value was for TCEP and TMPP.

The associations between renal disease severity and exposure to organophosphate flame retardants in patients with chronic kidney disease

Organophosphate flame retardants (OPFRs) are emerging and widespread environmental pollutants with potential health hazards, including nephrotoxicity. However, the exposure patterns and nephrotoxic potential of OPFRs are yet to be investigated in patients with chronic kidney disease (CKD). We conducted a cross-sectional study involving 166 patients with CKD stratified by estimated glomerular filtration rate (eGFR) and severity of proteinuria. The urinary concentrations of 10 OPFR compounds were measured to evaluate the exposure patterns. Clinical and urinary OPFR profiles were compared among subgroups to identify whether the OPFR compounds were independently correlated with eGFR and proteinuria. Additionally, lifestyle factors were compared among subgroups stratified by median concentrations of urinary OPFR compounds associated with renal disease severity. This study revealed universal exposure to OPFRs in the CKD population, with an overall urinary detection rate of 98.80 %. Furthermore, after adjusting for covariates, the urinary concentration of bis(2-chloroethyl) phosphate (BCEP) was identified as an independent predictor of lower eGFR (low vs high eGFR, odds ratio (OR) (95 % confidence interval (CI)), 1.761 (1.032-3.005) per log μg/g creatinine, p = 0.038), and the urinary concentration of bis(2-butoxyethyl) phosphate (BBOEP) was independently correlated with overt proteinuria in CKD patients (with vs without overt proteinuria, OR (95 % CI), 1.813 (1.065-3.086) per log μg/g creatinine, p = 0.028). Moreover, frequent seafood consumption was negatively correlated with urinary BCEP concentration (high vs low BCEP, OR (95 % CI), 0.455 (0.228-0.908), p = 0.025), and age was inversely associated with urinary BBOEP concentration (high vs low BBOEP, OR (95 % CI), 0.968 (0.937-0.999) per year, p = 0.048). In conclusion, our investigation highlights the extensive exposure to OPFRs and the independent association between renal disease severity and urinary BCEP/BBOEP concentrations in the CKD population, indicating the nephrotoxic potential of these pollutants.

Triphenyl phosphate (TPP) promotes hepatocyte toxicity via induction of endoplasmic reticulum stress and inhibition of autophagy flux

Triphenyl phosphate (TPP), a commonly used organophosphate flame retardant, is frequently found in environmental and biota samples, indicating widespread human exposure. Recent studies have shown that TPP causes hepatotoxicity, but the underlying cellular mechanisms are not fully elucidated. Here, by using normal hepatocyte AML12 cells as a model, we showed that TPP induced apoptotic cell death. RNA sequencing analyses revealed that differentially expressed genes induced by TPP were related to endoplasmic reticulum (ER) stress and autophagy. Immunostaining and western blot results further confirmed that TPP activated ER stress. Interestingly, though TPP increased LC3-II, a canonical marker for autophagy, TPP inhibited autophagy flux rather than induced autophagy. Interestingly, TPP-induced ER stress facilitated autophagy flux inhibition and apoptosis. Furthermore, inhibition of autophagy aggravated, and activation of autophagy attenuated apoptosis induced by TPP. Collectively, these results uncovered that ER stress and autophagy flux inhibition were responsible for TPP-induced apoptosis in mouse hepatocytes. Thus, our foundlings provided novel insight into the potential mechanisms of TPP-induced hepatocyte toxicity.

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.

Organophosphate esters in children and adolescents in Liuzhou city, China: concentrations, exposure assessment, and predictors

Dermal contact with dust is commonly considered an important pathway of exposure to organophosphate esters (OPEs), but the importance of OPE uptake from diet is unclear. Herein, we used hand wipes to estimate OPE exposure from indoor dust and examined whether urinary OPE metabolite concentrations were influenced by sociodemographic characteristics, OPE amount in hand wipes, and dietary factors. OPEs were measured in urine and hand wipes from 6 to 18-year-old children and adolescents (n=929) in Liuzhou, China. Sociodemographic and dietary factors were obtained from questionnaire. Six OPE metabolites were detected in >70% of the urine samples, and seven OPEs were detected in >50% of the hand wipes. Estimated daily intakes (EDIs) were calculated using urinary OPE metabolites to investigate the total daily intake of OPEs, in which 0.36-10.1% of the total intake was attributed to the exposure from dermal absorption. In multivariate linear regression models, sex, age, and maternal education were significant predictors of urinary OPE metabolite concentrations. Urinary diphenyl phosphate (DPHP) is positively associated with its parent compounds 2-ethylhexyl-diphenyl phosphate (EHDPP) and triphenyl phosphate (TPHP) in hand wipes. High versus low vegetable intake was associated with a 23.7% higher DPHP (95% confidence interval (CI): 0.51%, 52.1%). Barreled water drinking was associated with a 30.4% (95% CI: 11.8%, 52.0%) increase in bis(1-chloro-2-propyl) 1-hydroxy-2-propyl phosphate (BCIPHIPP) compared to tap water drinking. Our results suggested the widespread exposure to OPEs in children and adolescents. In addition to dermal absorption, dietary intake may be an important exposure source of certain OPEs.

Critical review of analytical methods for the determination of flame retardants in human matrices

Human biomonitoring is a powerful approach in assessing exposure to environmental pollutants. Flame retardants (FRs) are of particular concern due to their wide distribution in the environment and adverse health effects. This article reviews studies published in 2009-2020 on the chemical analysis of FRs in a variety of human samples and discusses the characteristics of the analytical methods applied to different FR biomarkers of exposure, including polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD), novel halogenated flame retardants (NHFRs), bromophenols, incl. tetrabromobisphenol A (TBBPA), and organophosphorous flame retardants (PFRs). Among the extraction techniques, liquid-liquid extraction (LLE) and solid phase extraction (SPE) were used most frequently due to the good efficiencies in the isolation of the majority of the FR biomarkers, but with challenges for highly lipophilic FRs. Gas chromatography-mass spectrometry (GC-MS) is mainly applied in the instrumental analysis of PBDEs and most NHFRs, with recent inclusions of GC-MS/MS and high resolution MS techniques. Liquid chromatography-MS/MS is mainly applied to HBCD, bromophenols, incl. TBBPA, and PFRs (including metabolites), however, GC-based analysis following derivatization has also been used for phenolic compounds and PFR metabolites. Developments are noticed towards more universal analytical methods, which enable widening method scopes in the human biomonitoring of FRs. Challenges exist with regard to sensitivity required for the low concentrations of FRs in the general population and limited sample material for some human matrices. A strong focus on quality assurance/quality control (QA/QC) measures is required in the analysis of FR biomarkers in human samples, related to their variety of physical-chemical properties, low levels in most human samples and the risk of contamination.

Exposure to organophosphate esters in elderly people: Relationships of OPE body burdens with indoor air and dust concentrations and food consumption

Human exposure to OPEs is pervasive and should be of great concern due to associations with adverse health effects, especially in susceptible populations. In this study, body burdens and exposure pathways of OPEs were investigated for 76 healthy elderly people in Jinan, China based on the measured OPE and metabolite concentrations in human bio-samples (whole blood and urine) and paired environmental matrices (air and dust), as well as food frequency questionnaire. Eight of 16 OPEs and 5 of 11 metabolites were detected in > 50% of whole blood and urine samples, respectively. Tri(1-chloro-2-propyl) phosphate (TCIPP), tris(2-chloroethyl) phosphate (TCEP), tri-phenyl phosphate (TPHP), and 2-ethylhexyl di-phenyl phosphate (EHDPP) were frequently detected and abundant in whole blood, while their corresponding metabolites were detected at low frequencies or levels in urine. The reduced metabolic and/or excretory capacity of elderly people may be an important reason, implying a higher health risk to them. Fourteen OPEs had over 50% detection frequencies in indoor air and dust, while 6 di-esters in indoor dust. Tris(2-ethylhexyl) phosphate (TEHP) in indoor dust and tri-n-butyl phosphate (TnBP) in indoor air were positively correlated with paired levels in blood but not with their metabolites (BEHP and DnBP) in urine. Combined with the direct intakes of BEHP and DBP from dust, blood is indicated as more suitable biomarker for TEHP and TnBP exposure. High consumption frequencies of several foods were associated with higher blood concentrations of three OPEs and urinary levels of four di-OPEs, indicating the importance of dietary exposure pathway. Estimated daily total intakes of OPEs via inhalation, dust ingestion, and dermal absorption ranged from 2.78 to 42.0 ng/kg bw/day, which were far less than the reference dosage values. Further studies were warranted to explore the potential health effects of OPE exposure in the elderly populations.

Organophosphate Esters in Indoor Environment and Metabolites in Human Urine Collected from a Shanghai University

In China, organophosphate esters (OPEs) are widely used in indoor environments. However, there is little information regarding the internal and external exposure of university students to OPEs. Therefore, in this study, nine OPEs and eight OPE metabolites (mOPEs) were measured in indoor dust and atmospheric PM2.5 samples from a university campus in Shanghai, as well as in urine samples collected from the university students. The total concentration of OPEs in the indoor dust in female dormitories (1420 ng/g) was approximately twice that in male dormitories (645 ng/g). In terms of indoor PM2.5, the highest OPE concentration was found in meeting rooms (105 ng/m3, on average), followed by chemical laboratories (51.2 ng/m3), dormitories (44.9 ng/m3), and offices (34.9 ng/m3). The total concentrations of the eight mOPEs ranged from 279 pg/mL to 14,000 pg/mL, with a geometric mean value of 1590 pg/mL. The estimated daily intake values based on the indoor dust and PM2.5 OPE samples (external exposure) were 1-2 orders of magnitude lower than that deduced from the concentration of urinary mOPEs (internal exposure), indicating that dermal contact, dust ingestion, and inhalation do not contribute significantly to OPE exposure in the general population. Moreover, additional exposure routes lead to the accumulation of OPEs in the human body.

A review on the occurrence of organophosphate flame retardants in the aquatic environment in China and implications for risk assessment

Organophosphate flame retardants (OPFRs), used extensively as substitutes for polybrominated diphenyl ethers, are ubiquitous environmental contaminants. OPFR pollution in aquatic environments, the main sink of pollutants, has been studied extensively over the past decade. Here, we review the current knowledge on the consumption and applications of OPFRs, and on their ecotoxicity in aquatic environments worldwide. We also synthesize the available evidence on the occurrence of OPFRs in aquatic environments in China (wastewater treatment plant influent and effluent, surface water, sediment, aquatic biota, and drinking water). Across China, the measured concentrations of OPFRs differ by more than three orders of magnitude. Risk assessments based on these measurements indicate a low level of ecological risk from OPFRs in most aquatic environments in China, and a low risk to human health from drinking water and aquatic products. Finally, we identify gaps in the current knowledge and directions for further research on OPFRs in aquatic environments.

Occurrence, distribution, and potential exposure risk of organophosphate flame retardants in house dust in South Korea

Concentrations of organophosphate flame retardants (OPFRs), which are used in various plastic products, were analyzed in house dust samples collected from three Korean cities (Suwon, n = 23; Jeonju, n = 20; Kunsan, n = 42). OPFRs, including tris (2-chloroethyl) phosphate (TCEP), tris (2-chloroisopropyl) phosphate (TCPP), and tris (1,3-dichloro-2-propyl) phosphate (TDCPP), were detected in 95%-100% of the samples analyzed, suggesting the widespread use of these compounds in Korea. The levels of TCEP, TCPP, and TDCPP in Suwon, Jeonju, and Kunsan ranged from the limit of quantitation to 46,000, 28,000, and 2400 ng/g, respectively. The concentrations of all OPFRs were significantly higher in house dust samples from Suwon than from Jeonju and Kunsan; this is likely due to the increased use of these compounds in Suwon, which may be associated with the number, volume, and variety of household products in homes. In Korean homes, the estimated daily intake (EDI) of OPFRs through house dust ingestion was lower than the guideline values; however, the EDI of OPFRs for toddlers was 30-fold greater than for adults, suggesting a limited risk to human health. This is the first comprehensive study of the occurrence and distribution of OPFRs in house dust in Korea.

Uncovering Evidence for Endocrine-Disrupting Chemicals That Elicit Differential Susceptibility through Gene-Environment Interactions

Exposure to endocrine-disrupting chemicals (EDCs) is linked to myriad disorders, characterized by the disruption of the complex endocrine signaling pathways that govern development, physiology, and even behavior across the entire body. The mechanisms of endocrine disruption involve a complex system of pathways that communicate across the body to stimulate specific receptors that bind DNA and regulate the expression of a suite of genes. These mechanisms, including gene regulation, DNA binding, and protein binding, can be tied to differences in individual susceptibility across a genetically diverse population. In this review, we posit that EDCs causing such differential responses may be identified by looking for a signal of population variability after exposure. We begin by summarizing how the biology of EDCs has implications for genetically diverse populations. We then describe how gene-environment interactions (GxE) across the complex pathways of endocrine signaling could lead to differences in susceptibility. We survey examples in the literature of individual susceptibility differences to EDCs, pointing to a need for research in this area, especially regarding the exceedingly complex thyroid pathway. Following a discussion of experimental designs to better identify and study GxE across EDCs, we present a case study of a high-throughput screening signal of putative GxE within known endocrine disruptors. We conclude with a call for further, deeper analysis of the EDCs, particularly the thyroid disruptors, to identify if these chemicals participate in GxE leading to differences in susceptibility.

Hippocampal proteomic analysis reveals the disturbance of synaptogenesis and neurotransmission induced by developmental exposure to organophosphate flame retardant triphenyl phosphate

With the spread of organophosphorus flame retardants (OPFRs), the environmental and health risks they induce are attracting attention. Triphenyl phosphate (TPHP) is a popular alternative to brominated flame retardant and halogenated OPFRs. Neurodevelopmental toxicity is TPHP's primary adverse effect, whereas the biomarkers and the modes of action have yet to be elucidated. In the present study, 0.5, 5, and 50 mg/kg of TPHP were orally administered to mice from postnatal day 10 (P10) to P70. The behavioral tests showed a compromised learning and memory capability. Proteomic analysis of the hippocampus exposed to 0.5 or 50 mg/kg of TPHP identified 531 differentially expressed proteins that were mainly involved in axon guidance, synaptic function, neurotransmitter transport, exocytosis, and energy metabolism. Immunoblot and immunofluorescence analysis showed that exposure to TPHP reduced the protein levels of TUBB3 and SYP in the synapses of hippocampal neurons. TPHP exposure also downregulated the gene expression of neurotransmitter receptors including Grins, Htr1α, and Adra1α in a dose-dependent fashion. Moreover, the calcium-dependent synaptic exocytosis governed by synaptic vesicle proteins STX1A and SYT1 was inhibited in the TPHP-treated hippocampus. Our results reveal that TPHP exposure causes abnormal learning and memory behaviors by disturbing synaptogenesis and neurotransmission.

Exposure levels, determinants and risk assessment of organophosphate flame retardants and plasticizers in adolescents (14-15 years) from the Flemish Environment and Health Study

The ubiquitous use of organophosphate flame retardants and plasticizers (PFRs) in a variety of consumer products has led to widespread human exposure. Since certain PFRs are developmental and carcinogenic toxicants, detailed exposure assessments are essential to investigate the risk associated with environmental exposure levels. However, such data are still lacking for European countries. In this study, concentrations of thirteen PFR metabolites were measured in urine samples from 600 adolescents from Flanders, Belgium. 1-Hydroxy-2-propyl bis(1-chloro-2-propyl) phosphate (BCIPHIPP), diphenyl phosphate (DPHP), bis(1,3-dichloro-isopropyl) phosphate (BDCIPP), 2-hydroxyethyl bis(2-butoxyethyl) phosphate (BBOEHEP), 2-ethylhexyl phenyl phosphate (EHPHP) and 2-ethyl-5-hydroxyhexyl diphenyl phosphate (5-HO-EHDPHP) were frequently detected (>83%) in all participants. Comparisons with study populations from outside the EU showed that urinary levels of DPHP, BDCIPP and BCIPHIPP were generally within the same range. Only exposure to 2-ethylhexyl diphenyl phosphate (EHDPHP) was presumably higher in Flemish adolescents. However, determinants analysis through multivariate regression analyses did not reveal significant predictors that may explain this finding. Significantly higher levels of BDCIPP were observed in participants with new decorations at home, while adolescents with highly educated parents had higher levels of BBOEHEP and BDCIPP. Furthermore, multiple PFR metabolite concentrations followed a seasonal pattern. Estimated daily intakes (EDIs) were calculated from the internal dose by including fractions of urinary excretion (F_UE) estimated in in vitro metabolism studies. EDIs ranged from 6.3 ng/kg bw/day for TBOEP to 567.7 ng/kg bw/day for EHDPHP, which were well below the available oral reference doses for all investigated PFRs. This suggests that the associated risk is low at present. This is the first report on internal exposure to seven commonly used PFRs in a European population.

Determinants of flame retardants in non-occupationally exposed individuals - A review

Flame retardants (FRs) constitute a large group of different substances, some of which have been phased out of the market due to health concerns, while others are still used in many common consumer products to prevent fire hazards. This review addressed the determinants of FRs in non-occupationally exposed individuals based on surveys and questionnaire data. For this literature review, three databases (Scopus, Pubmed and Web of Knowledge) were searched by applying suitable terms, inclusion and exclusion criteria, producing a final selection of 78 articles for review. Based on these surveys there is epidemiological evidence for a significant association (p < 0.05) among human exposure and demographic factors, as well as a significant correlation between exposure to FRs and behavioural and environmental factors. Age, gender, housing characteristics, electrical and electronic equipment and mouthing behaviour (in children) play a leading role in human exposure to FRs as published studies demonstrated. However, the methodological differences among studies such as population size, questionnaire design and statistical analysis did not reveal a complete pattern of human exposure routes. Risk perception and communication are also discussed based on limited available data. Knowledge gaps and future perspectives relating to standardized protocols, elucidation of contamination sources, and risk response of health information from different target groups were also identified.

Modified organophosphorus fire retardant with low toxicity/high flame retardancy using the pharmacophore model associated with Mamdani fuzzy inference approach

The bi-directional selective low toxicity/high flame retardancy organophosphorus fire retardants (OPFRs) derivatives were designed by a comprehensive effect 3D quantitative structure-activity relationship (QSAR) pharmacophore model, and the toxicity and flame retardancy mechanism of OPFR derivatives were explored. The 3D-QSAR comprehensive pharmacophore model was constructed using the toxicity/flame retardancy comprehensive evaluation values of OPFRs for molecular modifications, which were obtained by the Mamdani fuzzy inference approach. The environment-friendly OPFR derivatives (CDPP-F, CDPP-NO2, TPHP-F, TDCIPP-CH2CH3, and TDCIPP-Br) with high flame retardancy showed significantly reduced multi-toxicity effects (biotoxicity, reproductive toxicity, and neurotoxicity) in the comprehensive model. The spatial overlapping volumes of the toxicity/flame retardancy comprehensive effect model with the toxic effect and with flame retardant effect were 1 : 1. The trend (1 : 1) was similar to the degree of improvement of toxicity and flame retardancy of the OPFR derivatives. The toxicity and flame retardancy were decreased by more than 50%. This indicated that the spatial overlapping volumes in the comprehensive model with the toxic and flame retardant mono-models have significant effects. Based on the 2D-QSAR model, molecular docking, and density functional theory, it was found that, in molecular modification, the introduction of electronegative groups to improve the electronic parameters (q+) can reduce the toxicity of OPFRs. An increase in the bond length and bond angle of the molecular side chain increased the steric parameter (MR) that improved the molecular flame retardancy of OPFRs.

Young infants' exposure to organophosphate esters: Breast milk as a potential source of exposure

Organophosphate esters (OPEs) are applied as both flame retardants and plasticizers to a variety of consumer items such as home furnishings, construction materials, and children's products. While some assessments have characterized exposure among toddlers and young children, little is known about the OPE exposure among infants, who are a vulnerable population due to their rapid development. Here, we collected spot urine samples from 6-week-old (n = 100) and 12-month-old infants (n = 63), with about half of the infants evaluated at both ages (n = 52), to characterize OPE exposure and determine what factors contributed to higher exposures. Five of six OPE metabolites analyzed were detected frequently (>70%). Diphenyl phosphate was detected in every urine sample, while bis(2-chloro-isopropyl) phosphate (BCIPP) was the most abundant metabolite measured overall. Concentrations of bis(1-chloro-2-propyl) 1-hydroxy-2-propyl phosphate (BCIPHIPP) and BCIPP [i.e., metabolites of tris(2-chloro-isopropyl) phosphate (TCIPP)] were significantly greater among 6-week-old infants compared to 12-month-olds, while levels of other OPE metabolites were not statistically different in the first year of life. OPE metabolites were generally correlated with one another in samples collected at each age (r_s = 0.25-0.75; p < 0.05), and except BCIPHIPP, concentrations of the same metabolite were correlated over time (r_s = 0.41-0.53; p < 0.05). Breastfeeding at 6 weeks of age and owning a larger number of children's products were associated with increased concentrations of urinary BDCIPP. Infants who were currently receiving breast milk had higher levels of TCIPP metabolites; urinary BCIPP concentrations were 6.2 times higher in infants receiving breast milk at 6 weeks of age, and BCIPHIPP levels were 2.2 times higher for 12-month-old infants receiving breast milk (10^β = 7.2; 95% CI: 1.6-32.1 and 10^β = 3.2; 95% CI: 1.2-8.1, respectively). Differences in the predominant TCIPP metabolite associated with breastfeeding may suggest differences in metabolism with age. Cumulatively, our results suggest levels of OPE exposure may be higher for infants than other age groups, including toddlers and older children.

The influence of an upgrade on the reduction of organophosphate flame retardants in a wastewater treatment plant

The appearance of an increased amount of organophosphate flame retardant (OPFRs) in natural water is related the treated effluents from wastewater treatment plants (WWTPs) and thus understanding the OPFRs concentration and reduction variation in WWTPs would provide valuable insight into OPFR management and reduction. In this study, we have analyzed OPFRs (10 kinds: tris(chloroethyl) phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCPP), tris(1,3-dichloropropyl) phosphate (TDCP), tris(phenyl) phosphate (TPhP), tris(2-ethylhexyl) phosphate (TEHP), diphenylcresylphosphate (DCP), tris(methylphenyl) phosphate (TCP), tris(2-butoxyethyl) phosphate (TBEP), 2-ethylhexyl diphenyl phosphate (EHDP), and tris(butyl) phosphate (TBP)) in both water and sludge samples collected from different phases of a WWTP upgrading. The results show that TCPP and TCEP were mainly present in the aqueous phase, whereas TEHP dominated in the solid phase. The overall OPFR reduction efficiencies were above 40% through whole treatment processes by all the phases. More OPFRs reduction efficiency in primary sedimentation tanks was higher mainly because of bigger tank volume. The anaerobic zone in all cases could decrease OPFRs by over 13%. The removal of OPFRs in the oxic zone highly varied under the influence of the aeration pipe, water temperature, and aeration amount. Compared with chlorinated OPFRs, aryl and alkyl OPFRs were easier to reduce and less affected by the upgrading. Because OPFRs have been widely used in plastic materials such as pipes, WWTP upgrading - which usually requires more aeration and addition of reagents and instruments and the aim of which is normally to reduce more COD, N and P -- has introduced more OPFRs into the water within the WWTP.

Review of emerging contaminant tris(1,3-dichloro-2-propyl)phosphate: Environmental occurrence, exposure, and risks to organisms and human health

Tris(1,3-dichloro-2-propyl)phosphate (TDCPP) is a halogen-containing organophosphorus chemical that is widely employed in various consumer products with a high production volume. As an additive flame retardant (FR), TDCPP tends to be released into the environment through multiple routes. It is ubiquitous in environmental media, biotic matrixes, and humans, and thus is deemed to be an emerging environmental contaminant. To date, significant levels of TDCPP and its primary diester metabolite, bis(1,3-dichloro-2-propyl)phosphate, have been detected in human samples of seminal plasma, breast milk, blood plasma, placenta, and urine, thereby causing wide concern about the potential human health effects resulting from exposure to this chemical. Despite the progress in research on TDCPP over the past few years, we are still far from fully understanding the environmental behavior and health risks of this emerging contaminant. Thus, this paper critically reviews the environmental occurrence, exposure, and risks posed by TDCPP to organisms and human health among the literature published in the last decade. It has been demonstrated that TDCPP induces acute-, nerve-, developmental-, reproductive-, hepatic-, nephron-, and endocrine-disrupting toxicity in animals, which has caused increasing concern worldwide. Simultaneously, TDCPP induces cytotoxicity by increasing the formation of reactive oxygen species and inducing endoplasmic reticulum stress in multiple human cell lines in vitro, and also causes endocrine-disrupting effects, including reproductive dysfunction and adverse pregnancy outcomes, according to human epidemiology studies. This review not only provides a better understanding of the behavior of this emerging contaminant in the environment, but also enhances the comprehension of the health risks posed by TDCPP exposure to ecosystems and humans.

Enhanced Biodegradation/Photodegradation of Organophosphorus Fire Retardant Using an Integrated Method of Modified Pharmacophore Model with Molecular Dynamics and Polarizable Continuum Model

A comprehensive 3D-quantitative structure-activity relationship (QSAR) pharmacophore model was constructed using the values of comprehensive biodegradation/photodegradation effects of 17 organophosphorus flame retardants (OPFRs) evaluated by a normalization method to modify OPFRs with high biodegradation/photodegradation, taking tris(chloro-isopropyl) phosphate (TCPP), tris(2-chloroethyl) phosphate (TCEP) and tris(1-chloro-2-propyl) phosphate (TCIPP)-which occur frequently in the environment, and are the most difficult to degrade as target molecules. OPFR-derivative molecules TCPP-OH shows the highest improvement in biodegradation and photodegradation (55.48% and 46.37%, respectively). On simulating the biodegradation path and photodegradation path, it is found that the energy barrier of TCPP-OH for phosphate bond cleavage is reduced by 15.73% and 52.52% compared to TCPP after modification, respectively. Finally, in order to further significantly improve its biodegradability and photodegradation, the efficiency enhancement in the biodegradation and photodegradation of TCPP-OH are analyzed under the simulated environment by molecular dynamics and polarizable continuum model, respectively. The results of molecular dynamics show that the biodegradation efficiency of the TCPP-OH increased by 75.52% compared to TCPP. The UV spectral transition energy (4.07 eV) of TCPP-OH under the influence of hydrogen peroxide solvation effect is 44.23% lower than the actual transition energy (7.29 eV) of TCPP.

Organophosphate esters and their metabolites in paired human whole blood, serum, and urine as biomarkers of exposure

Although organophosphate diester (di-OPE) metabolites in urine are usually used to assess human exposure to organophosphate esters (OPEs), whether they can reflect human exposure to all OPEs with great differences in chemical structures and properties is still currently unclear. In this study, we detected sixteen OPEs and ten di-OPEs in 52 paired whole blood, serum, and urine samples collected in Beijing, China to investigate the correlations between different compounds and matrices, thus providing proper biomarkers of human exposure to OPEs. The order of the median concentrations of ∑OPEs was whole blood (8.63 ng/mL) > serum (5.71 ng/mL) > urine (0.396 ng/mL), while those of ∑di-OPEs followed the order of urine (16.6 ng/mL) > whole blood (5.97 ng/mL) > serum (3.70 ng/mL). Ethylhexyl diphenyl phosphate (EHDPP) and cresyl diphenyl phosphate (CDPP) were the dominant OPEs in both whole blood and serum samples and were significantly correlated between these two matrices. The distribution of OPEs in human blood was evaluated according to serum-to-whole blood concentration ratios (S:WB ratios). The median S:WB ratios of triethyl phosphate (TEP), tri-n-butyl phosphate (TnBP), bisphenol-A bis(diphenyl phosphate) (BABP), EHDPP, and CDPP were lower than 1, indicating that these OPEs preferred to accumulated in blood cells rather than in serum/plasma. Bis(2-ethylhexyl) phosphate (BEHP) was the major di-OPEs and was detected in almost all whole blood, serum and urine samples. The median whole blood: urine (WB:UR) ratios of di-OPEs were significantly and positively correlated with their logK_ow values, indicating that di-OPEs with low hydrophobicity were prone to excretion via urine. Based on the relationships between OPEs and di-OPEs in these matrices, the parent OPEs in whole blood can be recommended for use as alternative biomarkers of aryl-OPEs exposure in future human biomonitoring studies, in addition to metabolites in urine.

Organophosphate Esters: Are These Flame Retardants and Plasticizers Affecting Children's Health?

PURPOSE OF REVIEW

Organophosphate esters (OPEs) are applied to a variety of consumer products, primarily as flame retardants and plasticizers. OPEs can leach out of products over time and are consequently prevalent in the environment and frequently detected in human biomonitoring studies. Exposure during pregnancy is of particular concern as OPEs have recently been detected in placental tissues, suggesting they may be transferred to the developing infant. Also, studies have now shown that children typically experience higher exposure to several OPEs compared with adults, indicating they may be disproportionately impacted by these compounds. This review summarizes the current literature on reproductive and child health outcomes of OPE exposures and highlights areas for future research.

RECENT FINDINGS

Experimental animal studies demonstrate potential for OPEs to adversely impact health, and a limited number of epidemiologic studies conducted in adult cohorts suggest that OPEs may interfere with the endocrine system. Neurodevelopment is perhaps the most well studied of children's health endpoints, and several studies indicate that prenatal and early life OPE exposures impact both cognitive and behavioral development. Associations have also been reported with reproductive outcomes (e.g., fertilization and pregnancy loss) and with the timing of parturition and preterm birth. Cross-sectional studies also demonstrate associations between OPEs and respiratory health outcomes, allergic disease, and measures of adiposity. An expanding body of research demonstrates that OPEs are associated with adverse reproductive health and birth outcomes, asthma and allergic disease, early growth and adiposity, and neurodevelopment. Still, additional research is urgently needed to elucidate the full impact of OPEs on children's health.

Temporal trends and determinants of PFR exposure in the Hokkaido Study

The phase-out of polybrominated diphenyl ethers (PBDE) flame retardants has led to the rapid increase of alternatives such as phosphate flame retardants and plasticizers (PFRs) in many consumer products. Exposure to these additive chemicals is widespread and potentially harmful to humans and the environment. In the present study, we assessed the exposure to PFRs through the analysis of metabolites in urine collected from 7-year old children from Hokkaido, Japan between 2012 and 2017. This allowed us to investigate temporal and seasonal trends for PFR metabolite concentrations and to study determinants of exposure. Thirteen metabolites of seven PFRs were measured in morning spot urine samples (n = 400). Multiple regression models were used to quantify the yearly increase in metabolite concentrations per sampling year. Information on the demographics, indoor environment and dietary habits of the participants were derived from self-administered questionnaires. PFR metabolite concentrations were comparable to our previous study of school children (7-12 years old). Eight PFR metabolites were detected in >50% of the samples. During the study time period, concentrations of three metabolites increased significantly: bis(1,3-dichloro-2-propyl) phosphate (BDCIPP; 13.3% per year), 1-hydroxy-2-propyl bis(1-chloro-2-propyl) phosphate (BCIPHIPP; 12.9% per year), and 2-ethylhexyl phenyl phosphate (EHPHP; 6.7% per year). We also found seasonality as a determinant for several PFR metabolites, with 2-fold higher levels in summer for BCIPHIPP and BDCIPP. Concentrations were also significantly impacted by ventilation habits. More frequent window opening or use of mechanical ventilation was consistently associated with higher levels of PFR metabolites in children's urine. This is the first study to show that human exposure to PFRs has increased in recent years in Japan, which indicates that further research into this class of chemicals is warranted.

Urinary organophosphate ester concentrations in relation to ultra-processed food consumption in the general US population

BACKGROUND

Ultra-processed foods are highly processed foods which are manufactured with industrial substances to increase convenience and palatability. Some organophosphate esters (OPEs) are used as flame retardants and plasticizers and have been detected in food samples, particularly processed foods. However, little is known about dietary sources of OPEs or whether higher consumption of ultra-processed foods increases exposures.

OBJECTIVES

We evaluated whether higher consumption of ultra-processed food is associated with urinary OPE metabolite concentrations in a nationally representative sample of US children and adults.

METHODS

Among 2242 participants (≥6 years) in the National Health and Nutrition Examination Survey (NHANES) 2013-2014, we used the NOVA classification system to calculate percent of total energy from ultra-processed food using a 24 h dietary recall. Concentrations of 7 OPE metabolites, including diphenyl phosphate (DPHP), bis(1,3-dichloro-2-propyl) phosphate (BDCPP), bis(2-chloroethyl) phosphate (BCEP), dibutyl phosphate (DBUP), di-p-cresyl phosphate (DPCP), 2,3,4,5-tetrabromobenzoic acid (TBBA), and bis(1-chloro-2-propyl) phosphate (BCPP) were measured in urine. We used multivariable linear or logistic regressions to examine associations per 10% higher total energy from ultra-processed foods with percent changes or prevalence of detectable levels of creatinine-standardized OPEs.

RESULTS

In a model adjusting for only urinary creatinine, each 10% higher total energy from ultra-processed food was associated with 3.5% (95% CI: 0.7%, 6.3%) higher DPHP and 8.2% (95% CI: 4.6, 11.9%) higher BDCPP concentrations. However, none of the OPE metabolites was associated with ultra-processed food consumption in models adjusted for sociodemographic characteristics, health behaviors, and BMI (all p-values >0.05). Ultra-processed breads and tortillas; sauces, dressing, and gravies; and milk-based drinks were associated with higher concentrations of BDCPP while frozen and shelf-stable plate meals were associated with lower concentrations. Reconstituted meat or fish products and ultra-processed milk-based desserts were associated with greater odds of detectable levels of BCPP.

CONCLUSION

While some food groups were associated with urinary OPE metabolite concentrations, ultra-processed foods do not appear to be a major source of current OPE exposure in the US.

The association of urinary phosphorous-containing flame retardant metabolites and self-reported personal care and household product use among couples seeking fertility treatment

BACKGROUND

Phosphorous-containing flame-retardants (PFRs) are widely detected. They are used both as a flame retardant as well as plasticizer.

METHODS

A subset of 230 women and 229 men were recruited from Massachusetts General Hospital fertility clinic between 2005 and 2015. At each visit, participants completed a questionnaire of personal care product (PCP) and household product (HP) use. Metabolites [bis(1,3-dichloro-2-propyl) phosphate, diphenyl phosphate (DPHP), isopropylphenyl phenyl phosphate (ip-PPP), tert-butylphenyl phenyl phosphate and bis(1-chloro-2-propyl) phosphate] were measured in urine (1-5 samples; n = 638 women, n = 335 men). Associations were assessed using generalized mixed models, adjusted for SG, age, BMI, smoking, education, and season.

RESULTS

In women, moisturizer (60%), nail polish remover (77%), and nail polish (134%) use were associated (p < 0.05) with an increase in DPHP concentrations, while ip-PPP concentrations increased 21-27% with conditioner, cosmetics, deodorant, and hair product use. Mouthwash and vinyl glove use were associated with a respective 31% and 92% increase in DPHP among men.

CONCLUSIONS

Our exploratory analysis suggests PFRs may be used as a plasticizer in consumer products, and nail polish use contributes to internal DPHP exposure. Further research is needed to understand how PFRs are used in these products and how it relates to exposure.

Neonatal exposure to organophosphorus flame retardant TDCPP elicits neurotoxicity in mouse hippocampus via microglia-mediated inflammation in vivo and in vitro

Tris(1,3-dichloro-2-propyl) phosphate (TDCPP) is a phosphorus-based flame retardant common in consumer goods and baby products. Concerns have been raised about TDCPP exposure and neurodevelopmental toxicity. However, the mechanism and early response for TDCPP-induced neurotoxicity are poorly understood. This study investigates the role of microglia-mediated neuroinflammation in TDCPP-induced neurotoxicity in mice and primary cells. TDCPP was administered to C57BL/6 pups (0, 5, or 50 mg/kg/day) via an oral gavage from postnatal days 10-38 (28 days). The results showed that TDCPP exposure for 28 days altered the gene expression of neuronal markers Tubb3, Nefh, and Nes, and led to apoptosis in the hippocampus. The mRNA levels of pro-inflammatory factors Il-1β, Tnfα and Ccl2 dose dependently increased in the hippocampus at both 24 h and 28 days following exposure, accompanied by microglia activation characterized by an amoeboid-like phenotype. In in vitro studies using the primary microglia isolated from neonatal mice, exposure to TDCPP (0-100 μM) for 24 h resulted in cellular activation. It also increased the expression of genes responsible for inflammatory responses including surface markers and pro-inflammatory cytokines. These changes occurred in a dose-dependent fashion. Neurite outgrowth of primary mouse hippocampal neurons was inhibited by treatment with the conditioned medium harvested from microglia exposed to TDCPP. These results reveal that neonatal exposure to TDCPP induces neuronal damage through microglia-mediated inflammation. This provides insight into the mechanism of TDCPP's neurodevelopmental toxicity, and suggests that microglial cell is a sensitive responder for OPFRs exposure.

Multiple exposures to organophosphate flame retardants alter urinary oxidative stress biomarkers among children: The Hokkaido Study

Organophosphate flame retardants (PFRs) are used as additives in plastics and other applications such as curtains and carpets as a replacement for brominated flame retardants. As such, exposure to PFR mixtures is widespread, with children being more vulnerable than adults to associated health risks such as allergies and inflammation. Oxidative stress is thought to be able to modulate the development of childhood airway inflammation and atopic dermatitis. To evaluate these associations, the present study investigated the relationship between urinary PFR metabolites, their mixtures and urinary oxidative stress biomarkers in children as part of the Hokkaido Study on Environment and Children's Health. The levels of the oxidative stress biomarkers, such as 8-hydroxy-2'-deoxyguanosine (8-OHdG), hexanoyl-lysine (HEL), and 4-hydroxynonenal (HNE), and of 14 PFR metabolites were measured in morning spot urine samples of 7-year-old children (n = 400). Associations between PFR metabolites or PFR metabolite mixtures and oxidative stress biomarkers were examined by multiple regression analysis and weighted quantile sum regression analysis, respectively. We found that the non-chlorinated PFR metabolites, 2-ethylhexyl phenyl phosphate (EHPHP), bis(2-butoxyethyl) phosphate (BBOEP), and diphenyl phosphate (DPHP) were associated with increased levels of oxidative stress biomarkers. Furthermore, the PFR metabolite mixture was associated with increased levels of HEL and HNE, but not 8-OHdG. The combination of elevated top 2 PFR metabolites was not associated with higher urinary oxidative stress marker levels. This is the first study to report associations between urinary PFR metabolites and oxidative stress biomarkers among children.

A Review of a Class of Emerging Contaminants: The Classification, Distribution, Intensity of Consumption, Synthesis Routes, Environmental Effects and Expectation of Pollution Abatement to Organophosphate Flame Retardants (OPFRs)

Organophosphate flame retardants (OPFRs) have been detected in various environmental matrices and have been identified as emerging contaminants (EC). Given the adverse influence of OPFRs, many researchers have focused on the absorption, bioaccumulation, metabolism, and internal exposure processes of OPFRs in animals and humans. This paper first reviews the evolution of various types of flame retardants (FRs) and the environmental pollution of OPFRs, the different absorption pathways of OPFRs by animals and humans (such as inhalation, ingestion, skin absorption and absorption), and then summarizes the environmental impacts of OPFRs, including their biological toxicity, bioaccumulation, persistence, migration, endocrine disruption and carcinogenicity. Based on limited available data and results, this study also summarizes the bioaccumulation and biomagnification potential of OPFRs in different types of biological and food nets. In addition, a new governance idea for the replacement of existing OPFRs from the source is proposed, seeking environmentally friendly alternatives to OPFRs in order to provide new ideas and theoretical guidance for the removal of OPFRs.

Associations between urinary organophosphate ester metabolites and measures of adiposity among U.S. children and adults: NHANES 2013-2014

BACKGROUND

Organophosphate esters (OPEs) are synthetic chemicals found in many consumer products, including furniture, electronics, processed foods, and building materials. Emerging in vitro and in vivo studies suggest that OPEs are metabolism disrupting compounds; however, epidemiologic studies investigating their associations with adiposity markers are sparse.

OBJECTIVE

We examined cross-sectional associations between OPE biomarkers and adiposity measures among U.S. children and adults participating in the National Health and Nutrition Examination Survey (NHANES: 2013-2014).

METHODS

Concentrations of five OPE metabolites were quantified in urine: diphenyl phosphate (DPHP), bis(1,3-dichloro-2-propyl) phosphate (BDCPP), bis(2-chloroethyl) phosphate (BCEP), dibutyl phosphate (DBUP), and bis(1-chloro-2-propyl) phosphate (BCPP). We conducted covariate-adjusted logistic and linear regressions to examine associations between log2-transformed and dichotomized OPE metabolite concentrations and obesity, body mass index (BMI), and waist circumference (WC), separately among 784 children (6-19 years) and 1672 adults (≥20 years). We also assessed heterogeneity of associations by sex.

RESULTS

DBUP concentrations were inversely associated with the prevalence odds of being obese vs. normal weight in children (adjusted Prevalence Odds Ratio, aPOR: 0.82, 95% Confidence Interval, 95% CI: 0.70, 0.95) and adults (aPOR: 0.83, 95% CI: 0.72, 0.96). DBUP was also significantly associated with lower BMI z-scores (β:-0.08, 95% CI:-0.17, 0.01) and WC (β:-0.71, 95% CI: -1.49, 0.07) in children. BCEP concentrations were associated with increased prevalence odds of being overweight vs. normal weight (aPOR: 1.15, 95% CI: 1.01, 1.32) among children; similar, albeit not statistically significant, relationships were observed with other child adiposity outcomes. Among adults, detectable BCPP concentrations were associated with increased prevalence odds of being obese vs. normal weight (aPOR: 1.70, 95% CI: 1.21, 2.38) and having a high vs. normal WC (aPOR: 1.51, 95% CI: 1.11, 2.07) as well as higher BMI (β: 1.31, 95% CI: 0.30, 2.33). Other OPE metabolites were not consistently associated with adiposity measures among adults. Although associations of BCPP exposure with adiposity outcomes were generally inverse among boys, but not girls, we did not observe consistent evidence of sexually-dimorphic associations for other OPE metabolites.

CONCLUSIONS

Exposure to select OPEs may be differentially associated with body size among children and adults. Given the cross-sectional design of the present study, future prospective studies are needed to confirm these findings.

Metabolites of organophosphate esters in urine from the United States: Concentrations, temporal variability, and exposure assessment

Organophosphate esters (OPEs) are widely used as flame retardants and plasticizers in consumer products, which contributes to widespread exposure of humans. OPE diester metabolites in urine have been used as biomarkers of human exposure to these chemicals. Little is known, however, about occurrence and temporal variability in urinary concentrations of OPE metabolites in humans. In this study, 11 OPE metabolites were measured in 213 urine samples collected from 19 volunteers from Albany, New York, United States, at 3-day intervals for five weeks to investigate temporal variability in urinary concentrations. Diphenyl phosphate (DPHP) and bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) were the major OPE metabolites, detected in all urine samples at specific gravity (SG)-adjusted concentrations (geometric mean, GM) of 1060 and 414 pg/mL and creatinine (Cr)-adjusted concentration (GM) of 404 and 156 ng/g, respectively. Inter-day variability in urinary OPE metabolite concentrations in 19 individuals was evaluated by intraclass correlation coefficients (ICCs). The inter-day variability in Cr-adjusted OPE metabolite concentrations (ICC: 0.31-0.67) was lower than those of SG-adjusted (ICC: 0.19-0.71) and unadjusted urinary concentrations (ICC: 0.24-0.74). BDCIPP (ICC: 0.68) and bis(2-chloroethyl) phosphate (BCEP) (ICC: 0.67) concentrations showed a moderate-to-high reliability over the sampling period, whereas the other nine OPE metabolites exhibited a moderate reliability (ICC: 0.31-0.55). Urine samples were further stratified by gender, age, ethnicity, and body mass index (BMI). The concentrations of BDCIPP and DPHP were significantly lower in males with normal BMI (BMI: 18.5-25 kg/m2) than in females and other BMI categories (p < 0.01). Relatively high ICCs, indicating low inter-day variability, were observed for males (ICC: 0.35-0.71) of 30-40 years of age (ICC: 0.34-0.87) with normal BMI (ICC: 0.28-0.64). The daily exposure doses to OPEs were estimated from urinary concentrations of corresponding OPE metabolites. The estimated doses of triphenyl phosphate (TPHP) and triethyl phosphate (TEP), based on median urinary concentrations of their metabolites, were 19.4 and 24.0 ng/kg bw/day, and the exposure dose to ∑OPEs was estimated at 65.3 ng/kg bw/day. Overall, our results indicate a high ICC for Cr-adjusted urinary concentrations of 11 OPE metabolites in urine.

Urinary metabolites of organophosphate flame retardants in 0-5-year-old children: Potential exposure risk for inpatients and home-stay infants

Organophosphate flame retardants (OPFRs) have been commonly observed in indoor dust, food, and drinking water in China, but little is known about their exposure levels or factors leading to exposure in Chinese children. In this study, we measured eight metabolites of OPFRs (mOPFRs) in 227 urine samples collected from 0- to 5-year-old children in China. The high detection rates of mOPFRs (60%-100%) in the collected urine samples demonstrated the widespread exposure of this population to OPFRs. The median concentrations indicated that bis(2-chloroethyl)phosphate (BCEP, 0.85 ng/mL) and diphenyl phosphate (DPHP, 0.27 ng/mL) were the dominant chlorinated mOPFRs and nonchlorinated mOPFRs, respectively. Interestingly, the median urinary levels of bis(1-chloro-2-propyl)phosphate (BCIPP, 6.48 ng/mL) and bis(2-butoxyethyl)phosphate (BBOEP, 0.31 ng/mL) in inpatient infants were one order of magnitude higher (p < 0.01) than those observed in outpatient infants. For home-stay participants, furthermore, infants (0-1 year) had the highest median levels of BCIPP (0.72 ng/mL) and dibutyl phosphate (DBP, 0.14 ng/mL) among the three age groups (i.e., 0-1, >1-3, and >3-5 years), and significantly (p < 0.05) negative age-related relationships were found for both urinary mOPFRs. Two set of data on estimated daily intakes (EDIs) were calculated based on the fraction of OPFR excreted as the corresponding mOPFR (F_UE) in human liver microsomes (EDI_HLM) and S9 fraction (EDI_S9) system, respectively. In general, children have relatively high EDIs of tris(2-chloroethyl)phosphate (TCEP: EDI_HLM = 485 ng/kg bw/day, EDI_S9 = 261 ng/kg bw/day). Furthermore, 17% or 21% of inpatient infants had EDIs that exceeded the reference dose, whereas this value was reduced to 13% in outpatient infants; and this value decreased with age among all home-stay children (0-5 years). Our results indicated that inpatient and home-stay infants had a higher potential risk of OPFR exposure. To our knowledge, this is the first study to identify the elevated urinary levels of mOPFRs in inpatients.

Recent biomonitoring reports on phosphate ester flame retardants: a short review

Organophosphate triesters (PEFRs) are used increasingly as flame retardants and plasticizers in a variety of applications, such as building materials, textiles, and electric and electronic equipment. They have been proposed as alternatives to brominated flame retardants. This updated review shows that biomonitoring has gained incrementally greater importance in evaluating human exposure to PEFRs, and it holds the advantage of taking into account the multiple potential sources and various intake pathways of PEFRs. Simultaneous and extensive internal exposure to a broad range of PEFRs have been reported worldwide. Their metabolites, mainly dialkyl or diaryl diesters, have been used as biomarkers of exposure and have been ubiquitously detected in the urine of adults and children in the general population. Concentrations and profiles of PEFR urinary metabolites are seen to be variable and are highly dependent on individual and environmental factors, including age, country regulation of flame retardants, and types and quantities of emissions in microenvironments, as well as analytical procedures. Additional large biomonitoring studies, using a broad range of urinary diesters and hydroxylated metabolites, would be useful to improve the validity of the biomarkers and to refine assessments of human exposure to PEFRs.

Metabolites of organophosphate ester flame retardants in urine from Shanghai, China

The metabolites of nine organophosphate ester (OPE) flame retardants were measured in 180 urine samples collected from a population (including adults and children) in western Shanghai, China, using liquid chromatography-tandem spectrometry (LC-MS/MS). The total urinary concentrations of nine OPE metabolites ranged 100-23800 pg/mL, with a geometric mean (GM) value of 1450 pg/mL. The concentrations of alkyl-OPE metabolites (879 pg/mL) were approximately an order of magnitude higher than those of aryl-OPE (53.7 pg/mL) and chlorinated-OPE metabolites (52.7 pg/mL). Diphenyl phosphate (DPHP), diethyl phosphate (DEP), di-n-butyl phosphate (DNBP), bis(2-ethylhexyl) phosphate (BEHP), and bis(2-butoxyethyl) phosphate (BBOEP) were the dominant OPE metabolites found in urine. The results showed that an increase in age was associated with a significant decrease in urinary DPHP (r = -0.278, p < 0.01) and DNBP (r = -0.314, p < 0.01) concentrations. The highest concentrations of DPHP (GM = 80.7 pg/mL) and DNBP (GM = 16.9 pg/mL) were found in urine from people living in homes that were less than 10 years old. The urinary DNBP concentration was significantly associated with self-reported symptoms of allergy. Our result establishes baseline value for OPE exposure in a population in China for comparison in future studies.

Mining the Chemical Information on Urban Wastewater: Monitoring Human Exposure to Phosphorus Flame Retardants and Plasticizers

At the individual level, exposure to contaminants is generally assessed through the analysis of specific biomarkers in biological matrices. However, these studies are costly and logistically demanding, limiting their applicability to monitor population-wide exposure over time and space. By focusing on a selection of exposure biomarkers to phosphorus flame retardants and plasticizers (PFRs), this study aims to explore the possibility of using wastewater as a complementary source of information about exposure. Wastewater samples were collected from five cities in Europe and analyzed using a previously established method. Substantial differences in biomarker levels were observed between the investigated catchments, suggesting differences in exposure. Time trends in biomarkers observed between 2013 and 2016 were found to agree with results from human biomonitoring studies and reports about production volumes. Using Monte Carlo simulations, average urinary concentrations were estimated. These were generally higher compared to results from human biomonitoring studies. Various explanations for these differences were formulated (i.e., other excretion routes, external sources and different sampling approaches). Obtained results show that wastewater analysis provides unique information about geographical and temporal differences in exposure, which would be difficult to gather using other monitoring tools.