Human exposure to short-chain chlorinated paraffins and organophosphate flame retardants in relation to paired multiple sources

Trends of Organophosphate Ester Flame Retardant Metabolites in Age- and Sex-Stratified Pooled Australian Urine Samples from the Past Decade (2012-2023)

Organophosphate ester flame retardants (OPFRs) are extensively used as flame retardants and plasticizers in plastic products. Their ubiquitous presence in the environment has raised concerns regarding possible exposure and adverse health effects. Thirteen OPFR biomarkers were measured in pooled, de-identified surplus pathology urine samples collected cross-sectionally between 2012 and 2023 from an Australian population (18,700 individuals represented by 187 pools). We assessed age, sex, and temporal trends of OPFR metabolites detected in >60% of pools. Concentrations in both sexes significantly decreased with age for bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) and only in females for 2-ethylhexyl phenyl phosphate (EHPHP) and 2-ethyl-5-hydroxyhexyl diphenyl phosphate (5-HO-EHDPHP). The opposite was observed in males for 1-hydroxy-2-propyl bis(1-chloro-2-propyl) phosphate (BCIPHIPP) and EHPHP. Levels of BDCIPP, BCIPHIPP, and 5-HO-EHDPHP were significantly higher in males than in females in pools from 2020-2021 and all sampling years combined. A temporal increase in concentrations was observed for BCIPHIPP (males) and EHPHP (females). Risk characterization ratios (RCRs) showed mean exposures below derived no-effect levels (DNELs). Our observed age and sex trends, as well as mean concentrations, were comparable to previously reported trends and levels from Australia and other geographical locations. This study highlights age, sex, and temporal trends of OPFR exposure in Australia.

A critical review of human internal exposure to short-chain chlorinated paraffins and its concerning health risks

Short-chain chlorinated paraffins (SCCPs) are a complex mixture of chlorinated derivatives of n-alkanes with a chain length of 10-13 carbon atoms. SCCPs have been extensively used in industrial applications, although an alarming concern is increasingly raised in hazarding environmental matrices and biological organisms due to the environmental persistence, bioaccumulation potential, biotoxicity, and long-range atmospheric transport. Herein, this study conducted a critical review of human internal exposure to SCCPs and its concerning health risks by thoroughly analyzing 63 relevant articles screened in online databases, including the Web of Science, PubMed, Elsevier ScienceDirect, and China National Knowledge Infrastructure (CNKI). The review focused on various biological matrices, including blood, breast milk, and placenta, to assess human internal exposure to SCCPs, and summarized systematic health risk assessments for external exposures across different population groups. The primary exposure routes of SCCPs were dietary intake and dust ingestion and dermal absorption. Particularly, vulnerable population groups of infants, children, and occupational workers suffered from an elevated health risk of SCCPs, with the daily SCCPs intake approaching or exceeding the tolerable daily intake (TDI). So far, existing literature on an internal exposure to SCCPs by detecting human biological samples is insufficient and lacks a comprehensive, life cycle-wide monitoring of vulnerable and occupational populations. The relationship between human exposure to SCCPs and the consequent adverse health effects requires a further deep mining. Moreover, there is a lack of established exposure warning guidance values, and available internal exposure assessment models of SCCPs are currently limited. The future research priority is to knit together the assessment of human internal exposure to SCCPs and the following health risk by advanced sample pre-treatment and analytical methodologies, standardized operating procedures, and non-targeted screening combined with targeted detection techniques. Through a continuous monitoring of human internal exposure to SCCPs, clear illustration of the exposure-effect relationship and comprehensive health risk assessments via multiple exposure routes, these results shed lights on developing and revising regulatory frameworks for governing the production and handling of SCCPs.

Effects of urinary organophosphate flame retardants in susceptibility to attention-deficit/hyperactivity disorder in school-age children

Our previous studies have revealed a correlation between urinary phthalates (PAE) metabolites and parabens and PM2.5 exposure and susceptibility to attention-deficit/hyperactivity disorder (ADHD) in school-age children. Our goal was to examine the relationships between urinary organophosphate flame retardants (OPFRs) and their metabolites and the susceptibility to ADHD in the same cohort of children. We recruited 186 school children, including 132 with ADHD and 54 normal controls, living in southern Taiwan to investigate five OPFRs (1,3-dichloro-2-propyl phosphate (TDCPP), tri-n-butyl phosphate (TnBP), tris (2-chloroethyl) phosphate (TCEP), tris(2-butoxyethyl) phosphate (TBEP), and triphenyl phosphate (TPHP)) and five OPFR metabolites (bis(1,3-dichloro-2-propyl) phosphate (BDCPP), di-n-butyl phosphate (DNBP), bis(2-chloroethyl) hydrogen phosphate (BCEP), di-(2-butoxyethyl) phosphate (DBEP), and diphenyl phosphate (DPHP)) in urine. ADHD patients' behavioral symptoms and neuropsychological function were assessed using the Swanson, Nolan, and Pelham Version IV Scale (SNAP-IV) and the Conners' Continuous Performance Test 3rd Edition (Conners CPT3), respectively. BCEP was predominant among urinary OPFRs and the metabolites in both the ADHD and control groups. ADHD children had significantly higher levels of urinary BDCPP, BCEP, DBEP, DPHP, TCEP, TBEP, TNBP, TPHP, and Σ10OPFR compared to the controls. After controlling for age, gender, body mass index, PM2.5 exposure scenarios, and urinary phthalate metabolites, parabens, bisphenol-A and creatinine, levels of urinary BDCPP, TDCPP, and TBEP in ADHD children showed significant and dose-dependent effects on core behavioral symptoms of inattention. DNBP levels were positively correlated with neuropsychological deficits (CPT detectability, omission, and commission), while urinary DPHP in ADHD children were negatively related to CPT detectability and commission. Hyperactivity and impulsivity were not correlated with urinary OPFRs and their metabolites in ADHD children. In conclusion, the ADHD symptom of inattention and CPT performance may be closely associated with certain urinary OPFRs and their metabolites, independent of urinary PAE metabolites, parabens, and bisphenol-A in school-age-ADHD children.

Chemical-toxicological insights and process comparison for estrogenic activity mitigation in municipal wastewater treatment plants

Efforts in water ecosystem conservation require an understanding of causative factors and removal efficacies associated with mixture toxicity during wastewater treatment. This study conducts a comprehensive investigation into the interplay between wastewater estrogenic activity and 30 estrogen-like endocrine disrupting chemicals (EEDCs) across 12 municipal wastewater treatment plants (WWTPs) spanning four seasons in China. Results reveal substantial estrogenic activity in all WWTPs and potential endocrine-disrupting risks in over 37.5 % of final effluent samples, with heightened effects during colder seasons. While phthalates are the predominant EEDCs (concentrations ranging from 86.39 %) for both estrogenic activity and major EEDCs (phthalates and estrogens), with the secondary and tertiary treatment segments contributing 88.59 ± 8.12 % and 11.41 ± 8.12 %, respectively. Among various secondary treatment processes, the anaerobic/anoxic/oxic-membrane bioreactor (A/A/O-MBR) excels in removing both estrogenic activity and EEDCs. In tertiary treatment, removal efficiencies increase with the inclusion of components involving physical, chemical, and biological removal principles. Furthermore, correlation and multiple liner regression analysis establish a significant (p < 0.05) positive association between solid retention time (SRT) and removal efficiencies of estrogenic activity and EEDCs within WWTPs. This study provides valuable insights from the perspective of prioritizing key pollutants, the necessity of integrating more efficient secondary and tertiary treatment processes, along with adjustments to operational parameters like SRT, to mitigate estrogenic activity in municipal WWTPs. This contribution aids in managing endocrine-disrupting risks in wastewater as part of ecological conservation efforts.

Analytical methods and biomonitoring results in hair for the assessment of exposure to endocrine-disrupting chemicals: A literature review

Endocrine-disrupting chemicals (EDC) are compounds that alter functions of the endocrine system due to their ability to mimic or antagonize endogenous hormones, or that alter their synthesis and metabolism, causing adverse health effects. Human biomonitoring (HBM) is a reliable method to assess human exposure to chemicals through measurement in human body fluids and tissues. It identifies new sources of exposure and determines their distribution, thereby enabling detection of the most exposed populations. Blood and urine are commonly used for HBM of EDC, but their interest is limited for compounds presenting short half-lives. Hair appears as an interesting alternative insofar as it provides a large exposure window. For the present study, we evaluated the relevance of hair in determining EDC exposure. With this in mind, we undertook a literature review focusing on the bioanalytical aspects and performances of methods developed to determine EDC in hair. The literature review was performed through methodical bibliographical research. Relevant articles were identified using two scientific databases: PubMed and Web of Science, with search equations built from a combination of keywords, MeSH terms and Boolean operators. The search strategy identified 2949 articles. After duplicates were removed, and following title, abstract, and full-text screenings, only 31 were included for qualitative synthesis. Hair collection was mainly performed in the back of the head and preparation involved two processes: cutting into small pieces or grounding to powder. The off-line LC-MS/MS method remains the main technique used to assess EDC through hair. Differences regarding the validation of analytical methods and interpretation of HBM results were highlighted, suggesting a need for international harmonisation to obtain reliable and comparable results. External contamination of hair was identified as a main limitation in the interpretation of results, highlighting the need to better understand EDC transfers through hair and to develop relevant hair decontamination processes.

Stable isotope-assisted mass spectrometry reveals in vivo distribution, metabolism, and excretion of tire rubber-derived 6PPD-quinone in mice

6PPD-quinone (6PPD-Q) has been identified as a ubiquitous contaminant in the surrounding locality, including air particles, roadside soils, dust, and water. Recently, the prevalence of 6PPD-Q in human urine has accentuated the urgency for investigating its biological fate. To address this, we conducted a stable isotope-assisted high-resolution mass spectrometry (HRMS) assay to unveil the distribution, metabolism, excretion, and toxicokinetic properties of this contaminant in a mouse model. Mice were fed with a single dose of deuterated 6PPD-Q-d5 at human-relevant exposure levels. Results indicated that 6PPD-Q was quickly assimilated and distributed into bloodstream and main organs of mice, with the concentrations reaching peaks under 1 h following administration. Notably, 6PPD-Q was primarily distributed in the adipose tissue, marked by a significant Cmax (p < 0.05), followed by the kidney, lung, testis, liver, spleen, heart, and muscle. In addition, our measurement demonstrated that 6PPD-Q can penetrate the blood-brain barrier of mice within 0.5 h after exposure. The half-lives (t1/2) of 6PPD-Q in serum, lung, kidney, and spleen of mice were measured at 12.7 ± 0.3 h, 20.7 ± 1.4 h, 21.6 ± 5.3 h, and 20.6 ± 2.8 h, respectively. Using HRMS combined with isotope tracing techniques, two novel hydroxylated metabolites of 6PPD-Q in the mice liver were identified for the first time, which provides new insights into its rapid elimination in-vivo. Meanwhile, fecal excretion was identified as the main excretory pathway for 6PPD-Q and its hydroxylated metabolites. Collectively, our findings extend the current knowledge on the biological fate and exposure status of 6PPD-Q in a mouse model, which has the potential to be extrapolated to humans.