► A critical assessment of the current state of knowledge of toxicity, fate, and environmental levels of cVMS is presented. ► An overview of the use, physico-chemical properties, methods of ...detection, of the three most widely used cVMS is reported. ► Knowledge gaps and recommendations for future research on cVMS have been identified.
The fate and behavior of cyclic volatile methylsiloxanes (cVMS) octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) in the environment were reviewed. We evaluated their usage data and patterns, physico-chemical properties, toxicology, partitioning and degradation, methods of detection, and concentrations. The use of cVMS as an intermediate in the formation of silicone polymers, personal care and household products has resulted in their widespread environmental exposure; they have been detected in biogas, air, water, soil, biosolid, sediment, and biota samples. Modeled and experimental results suggest that cVMS may be subject to long-range atmospheric transport, but have low potential to contaminate the Arctic. For D4 and D5, there was no evidence of trophic biomagnification in aquatic food webs, while some aquatic organisms demonstrated a high degree of bioconcentration and bioaccumulation. High concentrations of cVMS observed in indoor air and biosolids resulted from point sources. Concentrations of cVMS in water, sediment, and soil were all below their no-observed-effect-concentrations.
Ever since the interest in organic environmental contaminants first emerged 50years ago, there has been a need to present discussion of such chemicals and their transformation products using simple ...abbreviations so as to avoid the repetitive use of long chemical names. As the number of chemicals of concern has increased, the number of abbreviations has also increased dramatically, sometimes resulting in the use of different abbreviations for the same chemical. In this article, we propose abbreviations for flame retardants (FRs) substituted with bromine or chlorine atoms or including a functional group containing phosphorus, i.e. BFRs, CFRs and PFRs, respectively. Due to the large number of halogenated and organophosphorus FRs, it has become increasingly important to develop a strategy for abbreviating the chemical names of FRs. In this paper, a two step procedure is proposed for deriving practical abbreviations (PRABs) for the chemicals discussed. In the first step, structural abbreviations (STABs) are developed using specific STAB criteria based on the FR structure. However, since several of the derived STABs are complicated and long, we propose instead the use of PRABs. These are, commonly, an extract of the most essential part of the STAB, while also considering abbreviations previously used in the literature. We indicate how these can be used to develop an abbreviation that can be generally accepted by scientists and other professionals involved in FR related work. Tables with PRABs and STABs for BFRs, CFRs and PFRs are presented, including CAS (Chemical Abstract Service) numbers, notes of abbreviations that have been used previously, CA (Chemical Abstract) name, common names and trade names, as well as some fundamental physico-chemical constants.
► A standard is proposed for abbreviations of brominated, chlorinated and phosphorus containing flame retardants (BFRs, CFRs and PFRs). ► The standard is aimed to simplify and promote scientific communication related to BFRs, CFRs and PFRs. ► Structured abbreviations (STABs) are prepared in close relation to the chemical structure of the BFRs, CFRs and PFRs. ► Practical abbreviations (PRABs) are in general derived from the STABs or from commonly used abbreviations from the past. ► Established, emerging, novel and potential BFRs, CFRs and PFRs are defined.
The distribution of dechloranes, a group of chlorinated flame retardants, were investigated in air, soil, and sediment around a newly discovered Dechlorane Plus (DP) production facility in China ...(Anpon). To date, the only known DP manufacturing plant is located in Niagara Falls, NY (OxyChem). Dechloranes including DP, Dechlorane (Mirex), and the recently discovered Dechlorane 602 (Dec 602) were detected in air, soil, and sediment, while Dechlorane 603 and Dechlorane 604 were below detection limit in all matrices. DP air concentrations near the facility ranged from 7737 to 26 734 pg m−3, the greatest reported thus far. Soil concentrations in the same area for DP, Dechlorane, and Dec 602 were 1490 ± 3580 ng g−1, 81.6 ± 96.5 ng g−1, and 7.24 ± 13.2 ng g−1 dry weight, respectively. Interestingly, lower concentrations of DP (4.93 ± 4.34 ng g−1), Dechlorane (30.2 ± 19.9 ng g−1), and Dec 602 (2.14 ± 2.23 ng g−1) were found in sediment from a nearby canal. Spatial trends of Dechlorane and Dec 602 in soil were similar to DP, implying that the DP manufacturing plant may also be a source of these other flame retardants. DP soil concentrations surrounding the facility decreased by an order of magnitude within 7.5 km. The syn-DP fractional abundance (f syn) value (0.40) for the commercial DP product manufactured at Anpon was slightly higher than that (0.20−0.36) produced by OxyChem. The f syn value in most air samples was largely similar to the Chinese commercial DP mixture, while most soil and sediment abundances were lower, suggesting a stereoselective depletion of syn-DP.
Dissolved organic matter (DOM) contains a complex array of chemical components that are intimately linked to many environmental processes, including the global carbon cycle, and the fate and ...transport of chemical pollutants. Despite its importance, fundamental aspects, such as the structural components in DOM remain elusive, due in part to the molecular complexity of the material. Here, we utilize multidimensional nuclear magnetic resonance spectroscopy to demonstrate the major structural components in Lake Ontario DOM. These include carboxyl-rich alicyclic molecules (CRAM), heteropolysaccharides, and aromatic compounds, which are consistent with components recently identified in marine dissolved organic matter . In addition, long-range proton-carbon correlations are obtained for DOM, which support the existence of material derived from linear terpenoids (MDLT). It is tentatively suggested that the bulk of freshwater dissolved organic matter is aliphatic in nature, with CRAM derived from cyclic terpenoids, and MDLT derived from linear terpenoids. This is in agreement with previous reports which indicate terpenoids as major precursors of DOM . At this time it is not clear in Lake Ontario whether these precursors are of terrestrial or aquatic origin or whether transformations proceed via biological and/or photochemical processes.
► Removal efficiencies of D4, D5, and D6 are above 90% in wastewater treatment plants in summer. ► D5 concentrations in effluent have an influence on those in receiving water. ► Potential risks of ...cVMS to aquatic, sediment-dwelling, and terrestrial organisms are low from the reported concentrations.
A comprehensive surveillance program was conducted to determine the occurrence of three cyclic volatile methylsiloxanes (cVMS) octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) in environmental compartments impacted by wastewater effluent discharges. Eleven wastewater treatment plants (WWTPs), representative of those found in Southern Ontario and Southern Quebec, Canada, were investigated to determine levels of cVMS in their influents and effluents. In addition, receiving water and sediment impacted by WWTP effluents, and biosolid-amended soil from agricultural fields were also analyzed for a preliminary evaluation of the environmental exposure of cVMS in media impacted by wastewater effluent and solids. A newly-developed large volume injection (septumless head adapter and cooled injection system) gas chromatography – mass spectrometry method was used to avoid contamination originating from instrumental analysis. Concentrations of D4, D5, and D6 in influents to the 11 WWTPs were in the range 0.282–6.69μgL−1, 7.75–135μgL−1, and 1.53–26.9μgL−1, respectively. In general, wastewater treatment showed cVMS removal rates of greater than 92%, regardless of treatment type. The D4, D5, and D6 concentration ranges in effluent were <0.009–0.045μgL−1, <0.027–1.56μgL−1, and <0.022–0.093μgL−1, respectively. The concentrations in receiving water influenced by effluent, were lower compared to those in effluent in most cases, with the ranges <0.009–0.023μgL−1, <0.027–1.48μgL−1, and <0.022–0.151μgL−1 for D4, D5, and D6, respectively. Sediment concentrations ranged from <0.003–0.049μgg−1dw, 0.011–5.84μgg−1dw, and 0.004–0.371μgg−1dw for D4, D5, and D6, respectively. The concentrations in biosolid-amended soil, having values of <0.008–0.017μgg−1dw, <0.007–0.221μgg−1dw, and <0.009–0.711μgg−1dw for D4, D5, and D6, respectively, were lower than those in sediment impacted by wastewater effluent in most cases. In comparison with the no-observed-effected concentrations (NOEC) and IC50 (concentration that causes 50% inhibition of the response) values, the potential risks to aquatic, sediment-dwelling, and terrestrial organisms from these reported concentrations are low.
The environmental ubiquity of perfluorooctane sulfonate (PFOS) is well-known. However, little is known about the environmental fate of individual PFOS isomers. In this study, we investigated the ...fractionation and the bioaccumulation of PFOS isomers in water, sediment, and biota collected from Lake Ontario. A total of six isomers, three perfluoro-monomethyl-substituted compounds, and three perfluoro-dimethyl isomers in addition to the linear PFOS (L-PFOS) were detected in water, sediment and biota. L-PFOS represented a much higher proportion of total PFOS (sum of linear and branched) in all organisms (>88%) compared to its proportion in technical PFOS (77%). The predominance of L-PFOS suggests a reduced uptake of branched isomers, a more rapid elimination of the branched isomers and/or a selective retention of the L-PFOS. The PFOS isomer profile found in biota was very similar to sediment, even for pelagic organisms such as zooplankton, suggesting greater partitioning of L-PFOS to biota and to sediment. The bioaccumulation factor (BAF) for L-PFOS between lake trout (whole fish) and water was estimated to be 3.4 × 104 L/kg compared with 2.9 × 103 L/kg for the monomethyl-substituted group (MM-PFOS). The remarkable difference between L-PFOS and branched isomer BAFs is due to an enrichment of branched isomers in water. The trophic magnification factor of L-PFOS (4.6 ± 1.0) was greater than MM-PFOS isomers (1.3 ± 0.17 to 2.6 ± 0.51), whereas dimethyl-PFOS showed no biomagnification. The results illustrate the important influence of molecular structure on the bioaccumulation of perfluoroalkyl sulfonates.
The fate of cyclic volatile methylsiloxanes (cVMS) – octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) – was evaluated in a typical ...secondary activated sludge wastewater treatment plant (WWTP). Water samples (influent, primary effluent, and final effluent) and sludge (primary sludge and waste activated sludge) samples were collected at overnight low, morning high, afternoon low, and evening high flows. Concentrations of cVMS in influents fluctuated with the influent flows, ranging from 0.166 to 1.13 μg L−1, 3.47–19.3 μg L−1, and 0.446–3.87 μg L−1 for D4, D5, and D6, respectively. Mass balance analysis of cVMS showed the average mass of D4, D5, and D6 entering and exiting the plant in influent and effluent, respectively, were 109 g d−1, 2050 g d−1, 280 g d−1, and 1.41 g d−1, 27.0 g d−1, 1.90 g d−1. The total removal efficiency of cVMS was >96%. To elucidate their detailed removal mechanisms, Mackay's fugacity-based treatment plant model was used to simulate the fate of cVMS through the WWTP. Due to the unusual combination of high hydrophobicity and volatility of cVMS, volatilization in the aeration tank and adsorption to sludge were the two main pathways of cVMS removal from water in this WWTP based on the experimental and modeled results. The morning and evening high influent mass flows contributed almost equally at approximately 40% of the total daily cVMS mass, with D5 accounting for the majority of this daily loading.
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•Significant diurnal variability of cVMS in influents was observed.•Morning and evening mass flows contributed major daily loading.•Volatilization and adsorption were the two main removal pathways.
The extent of bioaccumulation and trophic transfer of brominated diphenyl ether (BDE) congeners, hexabromocyclododecane (HBCD) diastereoisomers (α, β, and γ), decabromodiphenylethane (DBDPE), and ...bis(2,4,6‐tribromophenoxy)ethane (BTBPE) was examined in a Lake Winnipeg (Canada) food web. Six species of fish, zooplankton, mussels, sediment, and water from the south basin of the lake were selected for study. Significant positive correlations were found between concentrations of total (Σ) polybrominated diphenylethers (PBDEs; p < 0.005), ΣHBCDs (p < 0.0001), BTBPE (p < 0.0001), and lipid content in fish. Strong positive linear relationships also were observed from individual plots of BDE 47, BDE 209, and DBDPE concentrations (lipid wt) and trophic level (based on δ15N), suggesting that these compounds biomagnify in the Lake Winnipeg food web. Biomagnification factors varied for the chemicals studied. Plots of log bioaccumulation factors for mussel and zooplankton versus log octanol–water partition coefficient (Kow) were similar and suggest that neither mussels nor zooplankton are in equilibrium with the water. Fifteen BDE congeners were consistently detected in water (dissolved phase, n = 3), with BDE 47 having the greatest concentration (17 pg/L). The rank order of compounds in water (arithmetic mean ± standard error) were ΣPBDEs (49 ± 12 pg/L) > α‐HBCD (11 ± 2 pg/L) > BTBPE (1.9 ± 0.6 pg/L). Concentrations of DPDPE, BDE 209, and β‐ and γ‐HBCD isomers were below their respective method detection limits (MDLs) in water. Total PBDE concentrations in sediment (n = 4) were greater than any other brominated flame retardant examined in the present study and ranged from 1,160 to 1,610 ng/g (dry wt), with BDE 209 contributing roughly 50% of the total. The γ‐HBCD isomer was detected at concentrations of 50 ± 20 pg/g (dry wt) in sediment, whereas BTBPE and DBDPE were consistently below their respective MDLs in sediment.
The congener 2,2‘,3,3‘,4,4‘,5,5‘,6,6‘-decabromodiphenyl ether (BDE 209) is the primary component in a commonly used flame retardant known as decaBDE. This flame retardant constitutes approximately ...80% of the world market demand for polybrominated diphenyl ethers (PBDEs). Because this compound is very hydrophobic (log K ow ∼ 10), it has been suggested that BDE 209 has very low bioavailability, although debromination to more bioavailable metabolites has also been suggested to occur in fish tis- sues. In the present study, juvenile carp were exposed to BDE 209 amended food on a daily basis for 60 days, fol- lowed by a 40-day depuration period in which the fate of BDE 209 was monitored in whole fish and liver tissues sepa- rately. No net accumulation of BDE 209 was observed throughout the experiment despite an exposure concentration of 940 ng/day/fish. However, seven apparent debrominated products of BDE 209 accumulated in whole fish and liver tissues over the exposure period. These debrominated metabolites of BDE 209 were identified as penta- to octaBDEs using both GC/ECNI-MS and GC/HRMS. Using estimation methods for relative retention times of phenyl substitution patterns, we have identified possible structures for the hexa- and heptabromodiphenyl ethers identified in the carp tissues. Although exposure of carp to BDE 209 did not result in the accumulation of BDE 209 in carp tissues, our results indicate evidence of limited BDE 209 bioavailability from food in the form of lower brominated metabolites.
Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) have been identified as metabolites of PBDEs, and also as compounds of natural origin in the marine environment; however, there has only been ...very limited study of their presence in the abiotic environment. In the present study, OH-PBDEs were determined in samples of surface water and precipitation (rain and snow) collected from sites in Ontario, Canada. OH-PBDEs were detected in all the samples analyzed, although half of the observed peaks did not correspond to any of the 18 authentic standards available. Fluxes of ΣOH-PBDEs ranged from 3.5 to 190 pg/m2 in snow and from 15 to 170 pg/m2/day in rain, and those were higher at three of the southern Ontario locations relative to a single northern remote site. Concentrations of ΣOH-PBDEs ranged from 2.2 to 70 pg/L in water and from <1 to 420 pg/g in particulate organic carbon (POC), and higher values were found near sewage treatment plant (STP) outfalls in Lake Ontario. Partition coefficients (log K oc) for OH-PBDEs ranged from 4.0 to 5.1. The results in this study suggest that OH-PBDEs are ubiquitous in the abiotic environment and most likely are produced through reaction of PBDEs with atmospheric OH radicals. As well, they may be present in surface waters near STPs due to oxidation of PBDEs and inflows from metabolism by humans and animals.
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