Nontarget Identification of Novel Organophosphorus Flame Retardants and Plasticizers in Rainfall Runoffs and Agricultural Soils around a Plastic Recycling Industrial Park

Unseen streams tracing emerging contaminants from stormwater to surface water: A brief review

Emerging contaminants (ECs) have raised global concern due to their adverse effect on ecosystems and human health. However, the occurrence and transport of ECs in stormwater remain unclear. The impact of ECs from stormwater on surface water quality and ecosystem health is also poorly documented. In this review, we examined the variations in EC concentrations in surface water resulting from stormwater. During the wet weather, the concentrations of most investigated ECs, e.g., microplastics, per- and polyfluoroalkyl substances, and vehicle-related compounds, significantly increase in surface water, indicating that stormwater may be a critical source of these contaminants. Furthermore, the potential pathways of ECs from stormwater enter surface water are outlined. Studies demonstrate that surface runoff and combined sewer overflows are important pathways for ECs, with discharges comparable to or exceeding those from wastewater treatment plants. Illicit connection also plays an important part in elevated EC concentrations in surface water. Overall, our findings underscore the importance of stormwater as a source for ECs in surface waters, and urge for increased emphasis on, and reinforcement of, stormwater monitoring and control measures to minimize the transport of ECs into receiving water bodies.

Biotic and abiotic transformations of aqueous film-forming foam (AFFF)-derived emerging polyfluoroalkyl substances in aerobic soil slurry

The severe contamination of per- and polyfluoroalkyl substances (PFAS) in aqueous film-forming foam (AFFF)-affected soil and groundwater has raised global concerns. Although extensive studies on the transformation of electrochemical fluorination (ECF)-based PFAS in soil exist, limited research on AFFF-derived emerging fluorotelomer (FT) compounds has been conducted. Herein, a total of 38 PFAS were identified in a composite AFFF formulation through suspect and nontarget screening using high-resolution mass spectrometry (HRMS), and emerging 6:2 FT compounds were particularly prominent. Subsequently, the composite AFFF formulation was introduced to aerobic soil slurry to investigate the transformation behaviors of nine high-abundance polyfluoroalkyl substances. After a 150-day incubation, polyfluorinated sulfonamide betaine and quaternary ammonium compounds showed significant recalcitrance. The tertiary amine- and thioether-based PFAS underwent biotic and abiotic transformations, with half-lives ranging from 2 to 56 days and from 38 to 248 days, respectively. On the basis of the products identified using HRMS, the transformation pathways of FT- and ECF-based PFAS were proposed. Notably, the hydroxylation of tertiary amines and the oxidation of thioethers were two major abiotic reactions. Toxicity prediction revealed that certain transformation products exhibited higher toxicity toward aquatic organisms compared with the parent compounds. This study provides valuable insights into the stability and transformation of emerging PFAS in aerobic soil.

Detection of novel organophosphorus flame retardants and plasticizers in children urines: Associations with oxidative stress damage and thyroid nodule risk

Organophosphorus flame retardants and plasticizers (OPFRs) are prevalent and raise health concerns due to their endocrine-disrupting properties. Clinically detectable thyroid nodules are less common in children than in adults but pose a higher malignancy risk. The effects of OPFRs on children's thyroid nodules and their relation to oxidative stress remain unknown. This cross-sectional study analyzed concentrations of seven OPFRs and three oxidative stress biomarkers (OSBs), namely 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-OHdG), malondialdehyde, and o, o'-dityrosine (diY) in 521 urine samples from children in a coastal urbanized region. Median creatinine-adjusted levels of the seven OPFRs ranged from 0.02 to 0.64 μg/g. Triphenyl phosphine oxide (TPPO) was detected for the first time in children urine. Diphenyl phosphate (DPHP) and isopropyl phenyl phosphate (ip-PPP) were frequently detected, with median levels of 0.46 μg/g and 0.64 μg/g, respectively. Multiple linear regression analyses and mixture models demonstrated that seven OPFRs were positively associated with three OSBs. Furthermore, logistic regression analysis revealed that urinary TPPO and tris(1-chloro-2-propyl) phosphate (TCIPP) were associated with thyroid nodule risk in children, and TPPO and TCIPP further demonstrated sex-dependent association with thyroid nodule risk particularly in girls, although OSBs did not show significant mediating effects. Overall, further studies are warranted to explore the potential mechanisms linking thyroid health with OPFRs exposure and oxidative stress, particularly in children.

Recycling process of decoration and demolition waste is a neglected source for emerging concerns in particulate phase: PAHs as an example

Decoration and demolition waste (DDW) has been widely studied because of its annual surge in output, complex composition, and high utilization potential. DDW recycling is a key element of circular economy, with the potential for emerging pollutants in the particulate phase. Thus, this study selected polycyclic aromatic hydrocarbons (PAHs) as the representative and investigated their emission characteristics and occupational risk in the particulate phase, including 2.5-μm (PM2.5), inhalable (PM10), total suspended particles (TSP), and dust samples of different sizes (75-100 μm, 50-75 μm, and < 50 μm), from dust collectors during DDW recycling. Acenaphthylene (Acy), chrysene (Chr), benz[a]anthracene (BaA), fluoranthene (Fla), pyrene (Pyr), phenanthrene (Phe) were detected in all samples. PM2.5 and dust in 75-100 μm own the highest total occupation risk of 1.51 × 10-13 and 2.07 × 10-15, respectively. Chr and BaA had the control priority with the converted toxicity of 162.82 ng/g and 233.35 ng/g. Moreover, nontarget screening was applied to mining out isophorone, benzophenone, and other carcinogenic micropollutants in the PM2.5, PM10, TSP, and dust samples. Global PAHs from DDW recycling production can reach 193.44 ± 241.80 kg/a under reasonable estimation. This study provides strong evidence that DDW recycling is a neglected source of concern in the particulate phase.

Identification and Prioritization of Emerging Organophosphorus Compounds Beyond Organophosphate Esters in Chinese Estuarine Waters

Organophosphorus compounds (OPCs) pose potential hazards to human health and aquatic ecosystems. However, limited knowledge of emerging OPCs beyond organophosphate esters (OPEs) hinders a thorough understanding of the environmental occurrence and exposure risks. Through target, suspect, and nontarget screening analysis, 64 OPCs were successfully identified in Chinese estuarine waters, including 24 known OPEs and 40 emerging analogues (i.e., quaternary phosphonium, phosphine oxide, organophosphonate, and organothiophosphate esters). Domestic wastewater and agricultural and industrial discharges were factors influencing the OPC distribution patterns. In particular, quaternary phosphoniums and phosphine oxides accounted for over 50% of the total OPC loading in the Yellow and Jia Rivers, which were likely polluted by phosphorus-related industries. Risk quotient (RQ) calculations showed that tetrabutylphosphonium contributed the most to algae toxicity due to the biocidal effects of onium salts, while chloroalkyl OPEs dominated the ecological risks for daphnia and fish. The multicriteria decision analysis approach was further introduced for relative chemical ranking by considering the variations in hazard criteria of environmental occurrence, fate, and toxicity of the OPCs. The results indicate that aryl phosphoniums and aryl phosphine oxides have a hazard priority similar to that of the OPEs and, therefore, require more attention.

An Enhanced Protocol to Expand Human Exposome and Machine Learning-Based Prediction for Methodology Application

The human exposome remains limited due to the challenging analytical strategies used to reveal low-level endocrine-disrupting chemicals (EDCs) and their metabolites in serum and urine. This limits the integrity of the EDC exposure assessment and hinders understanding of their cumulative health effects. In this study, we propose an enhanced protocol based on multi-solid-phase extraction (multi-SPE) to expand human exposome with polar EDCs and metabolites and train a machine learning (ML) model for methodology prediction based on molecular descriptors. The protocol enhanced the measurement of 70 (25%) and 34 (12%) out of 295 well-acknowledged EDCs in serum and urine compared to the hydrophilic-lipophilic balance sorbent alone. In a nontarget analysis of serum and urine from 20 women of childbearing age in a cohort of 498, controlling occupational factors and daily behaviors for high chemical exposure potential, the multi-SPE protocol increased the measurement of 10 (40%) and 16 (53%) target EDCs and identification of 17 (77%) and 70 (36%) nontarget chemicals (confidence ≥ level 3) in serum and urine, respectively. Interestingly, the ML model predicted that the multi-SPE protocol could identify an additional 38% of the most bioactive chemicals. In conclusion, the multi-SPE protocol advances human exposome by expanding the measurement and identification of exposure profiles.

Insight into natural attenuation of tributyl phosphate by indigenous anaerobic microbes in soils: Implication by stable carbon isotope fractionation and microbial community structures

Organophosphate esters (OPEs) are widespread in the environment, with high persistence and toxicity. However, the underlying mechanisms of anaerobic microbial degradation of OPEs remain elusive in the field environment. In this study, the natural attenuation mechanisms of tributyl phosphate (TnBP) by indigenous anaerobic microorganisms in soils were investigated by using compound-specific stable isotope analysis (CSIA) and characterization of microbial communities. The results indicated that dibutyl phosphate (DnBP) was the major degradation product of TnBP. Significant carbon isotope fractionation was observed for TnBP during the anaerobic microbial degradation, and the carbon isotope enrichment factor (εC) was determined to be -2.71 ± 0.13‰. Unlike aerobic degradation with P-O bond cleavage, C-O bond cleavage was verified as the mode to removal a butyl side chain for TnBP to generate DnBP during the anaerobic microbial degradation. Microbial community analysis indicated that Sphingomonans, Nocardioides and Streptomyces were the important contributors to microbial degradation of TnBP in anoxic soils. TnBP altered microbial metabolic functions in anoxic soils, mainly enhancing the biosynthesis of ansamycins, ketone bodies and amino acids, and flagellar assembly, which promoted microbial degradation of TnBP. This study provided a better method to characterize the chemical bond cleavage mode and effect of OPEs on microbial communities, which was a prerequisite for the bioremediation of OPE pollution in soils.

Target and Nontarget Analysis of Organophosphorus Flame Retardants and Plasticizers in a River Impacted by Industrial Activity in Eastern China

Industrial activities are a major source of organophosphorus flame retardants (OPFRs) and plasticizers in aquatic environments. This study investigated the distribution of 40 OPFRs in a river impacted by major industrial manufacturing plants in Eastern China by target analysis. Nontarget analysis using high-resolution mass spectrometry was further employed to identify novel organophosphorus compounds (NOPs). Thirty-four OPFRs were detected in river water samples, with total concentrations of 62.9-1.06 × 103 ng/L (median: 455 ng/L). Triphenylphosphine oxide and diphenyl phosphoric acid were ubiquitously detected up to 620 and 127 ng/L, respectively. Among 26 identified NOPs, 17 were reported for the first time in the environment, including 14 novel organophosphate esters (especially 4 heterocycles and 3 oligomers), 2 organophosphites, and an organophosphonate. Bis(2,4-di-tert-butylphenyl) hydrogen phosphate and 2,2-dimethylpropoxy(propyl)phosphinic acid with high predicted persistence or toxicity were widely detected, with semiquantified concentrations up to 990 and 1.0 × 103 ng/L, respectively. Structurally similar organophosphorus heterocycles exhibited consistent variation trends, suggesting a common emission source. Estimated annual river discharges to the sea were 20.6-37.0 kg/yr for OPFRs and 30.8-161 kg/yr for NOPs. These findings indicate that industrial activities contribute OPFRs and NOPs to the river catchment and its estuary, posing ecological risks to both terrestrial and marine environments.

Nationwide profiling and source identification of organophosphate esters in Korean surface waters using target, suspect, and non-target HRMS analysis

Organophosphate esters (OPEs) are emerging contaminants that serve as alternatives to regulated substances in aquatic environments. A nationwide large-scale assessment for OPEs, including point sources, remains insufficient. To address this issue, we aimed to investigate OPEs occurrence and novel OPEs via comprehensive target, suspect and non-target analysis. Among the 11 target OPEs, 10 were detected at sampling sites distributed evenly nationwide. The highest mean concentrations were measured for tris-(2-butoxyethyl) phosphate (TBOEP) and tris(2-chloroisopropyl) phosphate (TCIPP). The multivariate statistical analysis revealed that TBOEP and TCIPP are essential components for assessing total OPEs pollution. The systematic risk assessment results evaluated the overall risk contribution of TBOEP and the significant risk impact of 2-ethylhexyl diphenyl phosphate. Promising suspect and non-target analysis enabled frequent detection and identification of 6 antioxidant transformation products (TPs), as well as the tentative identification of 14 OPEs and TPs, including 3 di-OPEs. Based on sampling site classification, we confirmed that major OPEs are significantly discharged near point sources. We believe that this is the first attempt to assess the nationwide risk and potential sources of OPEs in Korean surface waters, providing insights that could support further prioritization and regulation efforts.

Structure-Dependent Distribution, Metabolism, and Toxicity Effects of Alkyl Organophosphate Esters in Lettuce (Lactuca sativa L.)

This study provides a comprehensive investigation into the structure-dependent uptake, distribution, biotransformation, and potential toxicity effects of alkyl organophosphate esters (OPEs) in hydroponic lettuce (Lactuca sativa L.). Trimethyl, triethyl, and tripropyl phosphates were readily absorbed and acropetally translocated, while tributyl, tripentyl, and trihexyl phosphates accumulated mainly in lateral roots. The acropetal translocation potential was negatively associated with log Kow values. Trimethyl and triethyl phosphates are less prone to biotransformation, while a total of 14 novel hydrolysis, hydroxylated, and conjugated metabolites were identified for other OPEs using nontarget analysis. The extent of hydroxylation decreases from tripropyl phosphate to trihexyl phosphate, but multiple hydroxylations occurred more frequently on longer chain OPEs. Further comparative toxicity test revealed that hydrolyzed and hydroxylated metabolites have stronger toxic effects on Ca2+-dependent protein kinases (CDPK) than their parent OPEs. Dibutyl 3-hydroxybutyl phosphate particularly induces upregulation of CDPK in lateral roots of lettuce, probably associated with adenine reduction that may play an important role in the self-defense and detoxification processes. This study contributes to understanding the uptake and transformation behaviors of alkyl OPEs as well as their associations with a toxic effect on lettuce. This emphasizes the necessary evaluation of the environmental risk of the use of OPEs, particularly focusing on their hydroxylated metabolites.

Simultaneous determination of quaternary phosphonium compounds and phosphine oxides in environmental water and solid samples by ultrahigh performance liquid chromatography-tandem mass spectrometry

Quaternary phosphonium compounds (QPCs) and phosphine oxides (POs) are emerging contaminants that are attracting increasing attention. In the present study, a method for the quantification of QPCs and POs in multiple environmental media was developed using ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Analytes were extracted from water samples using solid phase extraction, and for the solid samples, ultrasonic extraction was employed. Compared with analytical methods established by previous studies, the approach developed in this study is more suitable for the quantitative analysis of compounds along with high sensitivity. The method quantification limit reached 0.12-2.55 ng⋅L-1 in water samples and 0.004-0.10 ng⋅g-1 in solid samples. The recoveries of target analytes spiked at low, medium and high concentrations in water and solid samples were in the range of 56.4-120 %, with relative standard deviations below 20 % (n = 6). Furthermore, the validated method succeeded in applying to analyse of eight QPCs and four POs in real environmental samples. At least five QPCs and two POs were detected in each environmental medium. This quantitative method would assist in further investigations on the occurrence, migration and the source of QPCs and POs.

Organophosphate ester in surface water of the Pearl River and South China Sea, China: Spatial variations and ecological risks

This study focused on investigating the concentrations, compositional profiles, partitioning behaviors and spatial variations of organophosphate esters (OPEs) in the Pearl River (PR), South China Sea (SCS) region, to evaluate their environmental risks. ∑OPEs concentrations in the surface water of the PR ranged from 117.5 to 854.8 ng/L in the dissolved phase and from 0.5 to 13.3 ng/L in the suspended particulate matter. In the surface seawaters of the northern and western parts of the SCS, ∑OPEs concentrations were 1.3-17.6 ng/L (mean: 6.7 ± 5.2) and 2.3-24.4 ng/L (mean: 7.6 ± 5.5), respectively. The percentage of chlorinated OPEs in surface water samples from the PR to the SCS was 79 ± 15%. Tripentyl phosphate (TPeP) (average: 28.3%) and triphenylphosphate (TPhP) (average: 9.6%) exhibited significant particulate fraction. A significant negative correlation (p < 0.05) between salt concentration and OPE congeners in seawater suggested that river runoff predominantly introduced OPEs into the coastal waters of the SCS. The findings also showed higher levels of OPEs in the PR and estuary than in offshore waters. The OPE loading from the PR into the SCS was estimated to be ∼119 t y-1. The presence of TCEP (RQmax = 2.1), TnBP (RQmax = 0.48) and TPhP (RQmax = 0.3) in PR water samples pose a high risk to aquatic organisms, whereas OPEs (RQ < 0.1) in SCS water samples do not pose a threat to aquatic organisms. This research emphasizes the environmental fate and impact of OPEs on surface waters of the PR and SCS.

Integration of Nontarget Screening and QSPR Models to Identify Novel Organophosphate Esters of High Priority in Aquatic Environment

With the development of large numbers of novel organophosphate esters (OPEs) alternatives, it is imperative to screen and identify those with high priority. In this study, surface water, biofilms, and freshwater snails were collected from the flow-in rivers of Taihu Lake Basin, China. Screened by target, suspect, and nontarget analysis, 11 traditional and 14 novel OPEs were identified, of which 5 OPEs were first discovered in Taihu Lake Basin. The OPE concentrations in surface water ranged from 196 to 2568 ng/L, with the primary homologue tris(2,4-ditert-butylphenyl) phosphate (TDtBPP) being newly identified, which was likely derived from the transformation of tris(2,4-ditert-butylphenyl) phosphite. The majority of the newly identified OPEs displayed substantially higher bioaccumulation and biomagnification potentials in the biofilm-snail food chain than the traditional ones. Quantitative structure-property relationship models revealed both hydrophobicity and polarity influenced the bioaccumulation and biomagnification of the OPEs, while electrostatic attraction also had a contribution to the bioaccumulation in the biofilm. TDtBPP was determined as the utmost priority by toxicological priority index scheme, which integrated concentration, bioaccumulation, biomagnification, acute toxicity, and endocrine disrupting potential of the identified OPEs. These findings provide novel insights into the behaviors of OPEs and scientific bases for better management of high-risk pollutants in aquatic ecosystem.

Contamination Status of Novel Organophosphate Esters Derived from Organophosphite Antioxidants in Soil and the Effects on Soil Bacterial Communities

The contamination status of novel organophosphate esters (NOPEs) and their precursors organophosphite antioxidants (OPAs) and hydroxylated/diester transformation products (OH-OPEs/di-OPEs) in soils across a large-scale area in China were investigated. The total concentrations of the three test NOPEs in soil were 82.4-716 ng g-1, which were considerably higher than those of traditional OPEs (4.50-430 ng g-1), OPAs (n.d.-30.8 ng g-1), OH-OPEs (n.d.-0.49 ng g-1), and di-OPEs (0.57-21.1 ng g-1). One NOPE compound, i.e., tris(2,4-di-tert-butylphenyl) phosphate (AO168 = O) contributed over 65% of the concentrations of the studied OPE-associated contaminants. A 30-day soil incubation experiment was performed to confirm the influence of AO168 = O on soil bacterial communities. Specific genera belonging to Proteobacteria, such as Lysobacter and Ensifer, were enriched in AO168 = O-contaminated soils. Moreover, the ecological function of methylotrophy was observed to be significantly enhanced (t-test, p < 0.01) in soil treated with AO168 = O, while nitrogen fixation was significantly inhibited (t-test, p < 0.01). These findings comprehensively revealed the contamination status of OPE-associated contaminants in the soil environment and provided the first evidence of the effects of NOPEs on soil microbial communities.

Distribution, traceability, and risk assessment of organophosphate flame retardants in agricultural soils along the Yangtze River Delta in China

Severe pollution threatens the ecosystem and human health in the Yangtze River Delta (YRD) in China because of the rapid development of industry in this area. This study examines the types, distribution, concentration, and origin of fourteen typical organophosphate flame retardants (OPFRs) in agricultural soils within the YRD region to offer insights for pollutant control and policy-making. The total concentration of OPFRs (ΣOPFRs) varied between 79.19 and 699.58 μg/kg dry weight (dw), averaging at 209.61 μg/kg dw. Among the OPFRs detected, tributoxyethyl phosphate (TBEP) was identified as the main congener, followed by tri-n-butyl phosphate (TnBP), tris(2-chloroisopropyl) phosphate (TCPP), and trimethyl phosphate (TMP). Source analysis, conducted through correlation coefficients and PCA, indicated that OPFRs in agricultural soils within the YRD region mainly originate from emissions related to plastic products and transportation. The health risk exposure to ΣOPFRs in agricultural soil was considered negligible for farmers, with values below 1.24 × 10-2 and 1.76 × 10-9 for noncarcinogenic and carcinogenic risks, respectively. However, the ecological risk of ΣOPFRs in all the samples ranged from 0.08-1.08, indicating a medium to high risk level. The results offer a comprehensive understanding of OPFR pollution in agricultural soils in the YRD region and can be useful for pollution control that mitigates ecological and health risks in this region.

Nontarget Identification of Novel Organophosphorus Flame Retardants and Plasticizers in Indoor Air and Dust from Multiple Microenvironments in China

The indoor environment is a typical source for organophosphorus flame retardants and plasticizers (OPFRs), yet the source characteristics of OPFRs in different microenvironments remain less clear. This study collected 109 indoor air samples and 34 paired indoor dust samples from 4 typical microenvironments within a university in Tianjin, China, including the dormitory, office, library, and information center. 29 target OPFRs were analyzed, and novel organophosphorus compounds (NOPs) were identified by fragment-based nontarget analysis. Target OPFRs exhibited the highest air and dust concentrations of 46.2-234 ng/m3 and 20.4-76.0 μg/g, respectively, in the information center, where chlorinated OPFRs were dominant. Triphenyl phosphate (TPHP) was the primary OPFR in office air, while tris(2-chloroethyl) phosphate dominated in the dust. TPHP was predominant in the library. Triethyl phosphate (TEP) was ubiquitous in the dormitory, and tris(2-butoxyethyl) phosphate was particularly high in the dust. 9 of 25 NOPs were identified for the first time, mainly from the information center and office, such as bis(chloropropyl) 2,3-dichloropropyl phosphate. Diphenyl phosphinic acid, two hydroxylated and methylated metabolites of tris(2,4-ditert-butylphenyl) phosphite (AO168), and a dimer phosphate were newly reported in the indoor environment. NOPs were widely associated with target OPFRs, and their human exposure risk and environmental behaviors warrant further study.

Discovering Novel Organophosphorus Compounds in Wastewater Treatment Plant Effluents through Suspect Screening and Nontarget Analysis

Limited knowledge on the structure of emerging organophosphorus compounds (OPCs) hampers our comprehensive understanding of their environmental occurrence and potential risks. Through suspect and nontarget screening, combining data-dependent acquisition, data-independent acquisition, and parallel reaction monitoring modes, we identified 60 OPCs (17 traditional and 43 emerging compounds) in effluents of 14 wastewater treatment plants (WWTPs) in Beijing and Qinghai, China. These OPCs comprise 26 organophosphate triesters, 17 organophosphate diesters, 6 organophosphonates, 7 organothiophosphate esters, and 4 other OPCs. Notably, 14 suspect OPCs were newly identified in WWTP effluents, and 16 nontarget OPCs were newly discovered in environmental matrices. Specifically, the cyclic phosphonate, (5-ethyl-2-methyl-1,3,2-dioxaphosphorinan-5-yl)methyl dimethyl phosphonate P-oxide (PMMMPn), consistently appeared in all WWTP effluents, with semiquantitative concentrations ranging from 44.4 to 282 ng/L. Its analogue, di-PMMMPn, presented in 93% of wastewater samples. Compositional differences between the WWTP effluents of two cities were mainly attributed to emerging OPCs. Hazard and ecological risk assessment underscored the substantial contribution of chlorinated organophosphate esters and organothiophosphate esters to overall risks of OPCs in WWTP effluents. This study provides the most comprehensive OPC profiles in WWTP effluents to date, highlighting the need for further research on their occurrence, fate, and risks, particularly for chlorinated OPCs.