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Cationic surfactants have a strong affinity to sorb to phospholipid membranes and thus possess an inherent potential to bioaccumulate, but there are few measurements of bioconcentration in fish. We measured the bioconcentration of 10 alkylamines plus two quaternary ammonium compounds in juvenile rainbow trout at pH 7.6, and repeated the measurements at pH 6.2 for 6 of these surfactants. The BCF of the amines with chain lengths <= C-14 was positively correlated with chain length, increasing similar to 0.5 log units per carbon. Their BCF was also pH dependent and approximately proportional to the neutral fraction of the amine in the water. The BCFs of the quaternary ammonium compounds showed no pH dependence and were >2 orders of magnitude less than for amines of the same chain length at pH 7.6. This indicates that systemic uptake of permanently charged cationic surfactants is limited. The behavior of the quaternary ammonium compounds and the two C-16 amines studied was consistent with previous observations that these surfactants accumulate primarily to the gills and external surfaces of the fish. At pH 7.6 the BCF exceeded 2000 L kg(-1) for 4 amines with chains >= C-13, showing that bioconcentration can be considerable for some longer chained cationic surfactants.

Bioaccumulation assessment is important for cationic surfactants in light of their use in a wide variety of consumer products and industrial processes. Because they sorb strongly to natural surfaces and to cell membranes, their bioaccumulation behavior is expected to differ from other classes of chemicals. Divided over two mixtures, we exposed rainbow trout to water containing 10 alkyl amines and 2 quaternary alkylammonium surfactants for 7 days, analyzed different fish tissues for surfactant residues, and calculated the tissues' contribution to fish body burden. Mucus, skin, gills, liver, and muscle each contributed at least 10% of body burden for the majority of the test chemicals. This indicates that both sorption to external surfaces and systemic uptake contribute to bioaccumulation. In contrast to the analogue alkylamine bases, the permanently charged quaternary ammonium compounds accumulated mostly in the gills and were nearly absent in internal tissues, indicating that systemic uptake of the charged form of cationic surfactants is very slow. Muscle-blood distribution coefficients were close to 1 for all alkyl amines, whereas liver-blood distribution coefficients ranged from 13 to 90, suggesting that the dominant considerations for sorption in liver are different from those in blood and muscle. The significant fraction of body burden on external surfaces can have consequences for bioaccumulation assessment.

Knowing the temperature dependence of the organic carbon/water partition ratios (K-oc) of volatile methylsiloxanes (VMS) is required to understand their environmental fate. We measured the Koc of two linear VMS (IVMS), three cyclic VMS (cVMS), and six polychlorinated biphenyls (PCBs) at 25, 15, 10, and 5 degrees C and calculated their enthalpies and entropies of sorption to organic carbon (Delta H-oc and Delta S-oc, respectively). The Delta H-oc of VMS ranged from -79.2 to -45.8 kJ mol(-1) while the Delta H-oc of the PCBs ranged from -68.7 to -29.3 kJ mol(-1). Previously reported measurements of the enthalpy of phase change between octanol and water (Delta H-ow) for cVMS (11.3-68.8 kJ mol(-1)) differed substantially from our Delta H-oc measurements, even showing different signs (negative versus positive). Literature data of Delta H-oc and Delta H-ow for PCBs (-61 to -17 kJ mol(-1)) are closer to our measured values of Delta H-oc for the PCBs showing the same sign (negative) with differences within a factor of 2 in the majority of the cases. Comparison of all available data for PCBs and VMS indicated that there may be important differences between Delta H-oc and Delta H-ow, especially for the VMS. Therefore, assuming Delta H-oc equals Delta H-ow in environmental fate models may be a source of substantial error.

It is challenging to measure the persistence of chemicals under field conditions. In this work, two approaches for measuring persistence in the field were compared: the chemical mass balance approach, and a novel chemical benchmarking approach. Ten pharmaceuticals, an X-ray contrast agent, and an artificial sweetener were studied in a Swedish lake. Acesulfame K was selected as a benchmark to quantify persistence using the chemical benchmarking approach. The 95% confidence intervals of the half-life for transformation in the lake system ranged from 780-5700 days for carbamazepine to <1-2 days for ketoprofen. The persistence estimates obtained using the benchmarking approach agreed well with those from the mass balance approach (1-21% difference), indicating that chemical benchmarking can be a valid and useful method to measure the persistence of chemicals under field conditions. Compared to the mass balance approach, the benchmarking approach partially or completely eliminates the need to quantify mass flow of chemicals, so it is particularly advantageous when the quantification of mass flow of chemicals is difficult. Furthermore, the benchmarking approach allows for ready comparison and ranking of the persistence of different chemicals., AuthorCount:5

Reaction with hydroxyl radicals (OH) is the major pathway for removal of cyclic volatile methyl siloxanes (cVMS) from air. We present new measurements of second-order rate constants for reactions of the cVMS octamethylcyclotetrasiloxane (D-4), decamethylcyclopentasiloxane (D-5), and dodecamethylcyclohexasiloxane (D-6) with OH determined at temperatures between 313 and 353 K. Our measurements were made using the method of relative rates with cyclohexane as a reference substance and were conducted in a 140-mL gas-phase reaction chamber with online mass spectrometry analysis. When extrapolated to 298 K, our measured reaction rate constants of D-4 and D-5 with the OH radical are 1.9 x 10(-12) (95% confidence interval (CI): (1.7-2.2) x 10(-12)) and 2.6 x 10(-12) (CI: (2.3-2.9) x 10(-12)) cm(3) molecule(-1) s(-1), respectively, which are 1.9x and 1.7x faster than previous measurements. Our measured rate constant for D-6 is 2.8 x 10(-12) (CI: (2.5-3.2) x 10(-12)) cm(3) molecule(-1) s(-1) and to our knowledge there are no comparable laboratory measurements in the literature. Reaction rates for D-5 were 33% higher than for D-4 (CI: 30-37%), whereas the rates for D-6 were only 8% higher than for D-5 (CI: 5-10%). The activation energies of the reactions of D-4, D-5, and D-6 with OH were not statistically different and had a value of 4300 +/- 2800 J/mol.

The sorption of cyclic volatile methyl siloxanes (cVMS) to organic matter has a strong influence on their fate in the aquatic environment. We report new measurements of the partition ratios between freshwater sediment organic carbon and water (K-OC) and between Aldrich humic acid dissolved organic carbon and water (K-DOC) for three cVMS, and for three polychlorinated biphenyls (PCBs) that were used as reference chemicals. Our measurements were made using a purge-and-trap method that employs benchmark chemicals to calibrate mass transfer at the air/water interface in a fugacity-based multimedia model. The measured log K-OC of octamethylcydotetrasiloxane (D-4), decamethylcyclopentasiloxane (D-5), and dodecamethylcydohexasiloxane (D-6) were 5.06, 6.12, and 7.07, and log K-DOC were 5.05, 6.13, and 6.79. To our knowledge, our measurements for K-OC of D-6 and K-DOC of D-4 and D-6 are the first reported. Polyparameter linear free energy relationships (PP-LFERs) derived from training sets of empirical data that did not include cVMS generally did not predict our measured partition ratios of cVMS accurately (root-mean-squared-error (RMSE) for logK(OC) 0.76 and for logK(DOC) 0.73). We constructed new PP-LFERs that accurately describe partition ratios for the cVMS as well as for other chemicals by including our new measurements in the existing training sets (logK(OC) RMSEcVMS: 0.09, logk(DOC) RMSEcVMS: 0.12). The PP-LFERs we have developed here should be further evaluated and perhaps recalibrated when experimental data for other siloxanes become available.

Lipids are the major sorptive phase for many organic chemicals that bioaccumulate in foodwebs. However, lipids are usually operationally defined by the extraction protocol. Large differences in sorptive capacities between species would violate assumptions implicit in widely used lipid-normalization procedures and invalidate generic bioaccumulation factors. We extracted lipids from five species from different trophic levels and domains and determined fractions of triglycerides, phospholipids, and cholesterol. We passively dosed the lipids with cyclic volatile methylsiloxanes and chlorobenzenes via headspace from spiked olive oil to determine their sorptive capacities. Lipids from seal blubber and pork bacon solely composed of triglycerides had capacities similar to that of olive oil; lipids from mussels, herring, and guillemot egg had quantifiable fractions of phospholipids and cholesterol and showed capacities reduced by factors of up to 2.3-fold. Generally, the sorptive capacities of the lipids were not elevated relative to the olive oil controls and are unlikely to explain a substantial part of biomagnification.

Chemical benchmarldng was used to investigate the temporal variation of the persistence of chemical contaminants in a Swedish lake. The chemicals studied included 12 pharmaceuticals, an artificial sweetener, and an X-ray contrast agent. Measurements were conducted in late spring, late autumn, and winter. The transformation half-life in the lake could be quantified for 7 of the chemicals. It ranged from several days to hundreds of days. For 5 of the chemicals (bezafibrate, climbazole, diclofenac, furosemide, and hydrochlorothiazide), the measured persistence was lower in late spring than in late autumn. This may have been caused by lower temperatures and/or less irradiation during late autumn. The seasonality in chemical persistence contributed to changes in chemical concentrations in the lake during the year. The impact of seasonality of persistence was compared with the impact of other important variables determining concentrations in the lake: chemical inputs and water flow/dilution. The strongest seasonal variability in chemical concentration in lake water was observed for hydrochlorothiazide (over a factor of 10), and this was attributable to the seasonality in its persistence.

Of the tens of thousands of chemicals in use, only a small fraction have been analyzed in environmental samples. To effectively identify environmental contaminants, methods to prioritize chemicals for analytical method development are required. We used a high-throughput model of chemical emissions, fate, and bioaccumulation to identify chemicals likely to have high concentrations in specific environmental media, and we prioritized these for target analysis. This model-based screening was applied to 215 organosilicon chemicals culled from industrial chemical production statistics. The model-based screening prioritized several recognized organosilicon contaminants and generated hypotheses leading to the selection of three chemicals that have not previously been identified as potential environmental contaminants for target analysis. Trace analytical methods were developed, and the chemicals were analyzed in air, sewage sludge, and sediment. All three substances were found to be environmental contaminants. Phenyl-tris(trimethylsiloxy)silane was present in all samples analyzed, with concentrations of similar to 50 pg m(-3) in Stockholm air and similar to 0.5 ng g(-1) dw in sediment from the Stockholm archipelago. Tris(trifluoropropyl)trimethyl-cyclotrisiloxane and tetrakis(trifluoropropyl)tetramethyl-cyclotetrasiloxane were found in sediments from Lake Mjosa at similar to 1 ng g(-1) dw. The discovery of three novel environmental contaminants shows that models can be useful for prioritizing chemicals for exploratory assessment., AuthorCount:11

Tens of thousands of tonnes of cyclic volatile methylsiloxanes (cVMS) are used each year globally, which leads to high and continuous cVMS emissions to air. However, field measurements of cVMS in air and empirical information about emission rates to air are still limited. Here we present measurements of decamethylcyclopentasfloxane (D-5) and dodecamethylcyclohexasiloxane (D-6) in air for Zurich, Switzerland. The measurements were performed in January and February 2011 over a period of eight days and at two sites (city center and background) with a temporal resolution of 6-12 h. Concentrations of Ds and D-6 are higher in the center of Zurich and range from 100 to 650 ng m(-3) and from 10 to 79 ng m(-3), respectively. These values are among the highest levels of D-5 and D-6 reported in the literature. In a second step, we used a multimedia environmental fate model parametrized for the region of Zurich to interpret the levels and time trends in the cVMS concentrations and to back calculate the emission rates of D-5 and D-6 from the city of Zurich. The average emission rates obtained for D-5 and D-6 are 120 kg d(-1) and 14 kg d(-1), respectively, which corresponds to per capita emissions of 310 mg capita(-1) d(-1) for D-5 and 36 mg capita(-1) d(-1) for D-6., AuthorCount:6

Cyclic volatile methyl siloxanes (cVMS) are present in technical applications and personal care products. They are predicted to undergo long-range atmospheric transport, but measurements of cVMS in remote areas remain scarce. An active air sampling method for decamethylcyclopentasiloxane (D5) was further evaluated to include hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), and dodecamethylcyclohexasiloxane (D6). Air samples were collected at the Zeppelin observatory in the remote Arctic (79 degrees N, 12 degrees E) with an average sampling time of 81 +/- 23 h in late summer (August-October) and 25 +/- 10 h in early winter (November-December) 2011. The average concentrations of D5 and D6 in late summer were 0.73 +/- 0.31 and 0.23 +/- 0.17 ng/m(3), respectively, and 2.94 +/- 0.46 and 0.45 +/- 0.18 ng/m(3) in early winter, respectively. Detection of D5 and D6 in the Arctic atmosphere confirms their long-range atmospheric transport. The D5 measurements agreed well with predictions from a Eulerian atmospheric chemistry-transport model, and seasonal variability was explained by the seasonality in the OH radical concentrations. These results extend our understanding of the atmospheric fate of D5 to high latitudes, but question the levels of D3 and D4 that have previously been measured at Zeppelin with passive air samplers., AuthorCount:6

Cyclic volatile methyl siloxanes (cVMS) concentrations were analyzed in the pelagic food web of two Norwegian lakes (Mjosa, Randsfjorden), and in brown trout (Salmo trutta) and Arctic char (Salvelinus alpinus) collected in a reference lake (Femunden), in 2012. Lakes receiving discharge from wastewater treatment plants (Mjosa and Randsfjorden) had cVMS concentrations in trout that were up to 2 orders of magnitude higher than those in Femunden, where most samples were close to the limit of quantification (LOO). Food web biomagnification of cVMS in Mjosa and Randsfjorden was quantified by estimation of trophic magnification factors (TMFs). TMF for legacy persistent organic pollutants (POPs) were analyzed for comparison. Both decamethylcyclopentasiloxane (DS) and dodecamethylcyclohexasiloxane (D6) biomagnified with TMFs of 2.9 (2.1-4.0) and 2.3 (1.8-3.0), respectively. Octamethylcyclotetrasiloxane (D4) was below the LOQ in the majority of samples and had substantially lower biomagnification than for D5 and D6. The cVMS TMFs did not differ between the lakes, whereas the legacy POP TMFs were higher in Mjosa than inRandsfjorden. Whitefish had lower cVMS bioaccumulation compared to legacy POPs, and affected the TMF significance for cVMS, but not for POPs. TMFs of D5 and legacy contaminants in Lake Mjosa were consistent with those previously measured in Mjosa., AuthorCount:4

The biomagnification of the cyclic volatile methyl siloxanes octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexatetrasiloxane (D6) was analyzed in the Lake Mjosa food web in Norway from zooplankton and Mysis to planktivorous and piscivorous fish. The trophic magnification factor (TMF) for D5 was determined and compared with TMFs of several legacy contaminants: polychlorinated biphenyl (PCB) congeners 153 and 180, polybrominated diphenyl ether (PBDE) congeners 47 and 99, and p,p'-DDE. D5 showed TMF significantly greater than 1, implying food web biomagnification (TMF = 2.28, CI: 1.22-4.29). This contrasts with two studies that reported TMF < 1, which may reflect variability in TMF between food webs. The Lake Mjosa D5 TMF was sensitive to the species included at the higher trophic level; whole food web TMF differed from TMF excluding smelt (Osmerus eperlanus) or brown trout (Salmo trutta) (TMF-SMELT = 1.62, CI: 0.96-2.72; TMF-TROUT = 3.58, CI: 1.82-7.03). For legacy contaminants (e.g., PCB-153 and PCB-180), the TMFs were less sensitive to the food web composition, and a better model fit was obtained compared to D5. The differences in biomagnification behavior between D5 and the legacy contaminants suggest that the biomagnification of D5 is being governed by species-specific properties such as biotransformation rate or tissue distribution that differ from those of legacy contaminants., AuthorCount:4

Cyclic volatile methylsiloxanes are being subjected to regulatory scrutiny as possible PET chemicals. The investigation of bioaccumulation has yielded apparently contradictory results, with high laboratory fish bioconcentration factors on the one hand and low field trophic magnification factors on the other. In this study, octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) were studied along with polychlorinated biphenyls (PCBs) in sediments, ragworm, and flounder from six sites in the Humber Estuary. Bioaccumulation was evaluated using multimedia bioaccumulation factors (mmBAFs) which quantified the fraction of the contaminant present in the aquatic environment that is transferred to the biota. PCB 180, a known strongly bioaccumulative chemical, was used as a benchmark. The mean mmBAF of D5 was about twice that of PCB 180 in both polycheates and flounder, while for D4 it was 6 and 14 times higher, respectively. The mmBAF of D6 was a factor 5-10 lower than that of PCB180. The comparatively strong multimedia bioaccumulation of D4 and D5, even in the absence of biomagnification, was explained by both compounds having a >100 times stronger tendency to partition into lipid rather than into organic carbon, while PCB 180 partitions to a similar extent into both matrices., authorCount :3

Decabromodiphenyl ethane (dbdpe) is a brominated flame retardant (BFR) used as a replacement for the structurally similar decabromodiphenyl ether (decaBDE), which is a regulated environmental contaminant of concern. Dbdpe has been found in indoor dust, sewage sludge, sediment and biota, but little is known about its occurrence and distribution in the environment. In this paper, sediment was analyzed from 11 isolated Swedish lakes and along a transect running from central Stockholm through the Stockholm archipelago to the open Baltic Sea. Dbdpe was present in all samples. In lake sediment, the levels ranged from 0.23 to 11 ng/g d.wt. and were very similar to the levels of decaBDE (0.48-11 ng/g d.wt.). Since the lakes have no known point sources of BFRs, their presence in the sediments provides evidence for long range atmospheric transport and deposition. In the marine sediment, the dbdpe and decaBDE levels decreased by a factor of 20-50 over 40 km from the inner harbor to the outer archipelago. There the dbdpe and decaBDE levels were similar to the levels in nearby isolated lakes. The results indicate that contamination of the Swedish environment with dbdpe has already approached that of decaBDE, and that this contamination is primarily occurring via the atmosphere.

Decamethylcyclopentasiloxane (D-5) is a volatile compound used in personal care products that is released to the atmosphere in large quantities. Although D-5 is currently under consideration for regulation, there have been no field investigations of its atmospheric fate. We employed a recently developed, quality assured method to measure D-5 concentration in ambient air at a rural site in Sweden. The samples were collected with daily resolution between January and June 2009. The 05 concentration ranged from 0.3 to 9 ng m(-3), which is 1-3 orders of magnitude lower than previous reports. The measured data were compared with D-5 concentrations predicted using an atmospheric circulation model that included both OH radical and D-5 chemistry. The model was parametrized using emissions estimates and physical chemical properties determined in laboratory experiments. There was good agreement between the measured and modeled D-5 concentrations. The results show that D-5 is clearly subject to long-range atmospheric transport, but that it is also effectively removed from the atmosphere via phototransformation. Atmospheric deposition has little influence on the atmospheric fate. The good agreement between the model predictions and the field observations indicates that there is a good understanding of the major factors governing D-5 concentrations in the atmosphere., authorCount :6

Beef and dairy products can be important vectors of human exposure to polybrominated diphenylethers (BDEs), and hence an understanding of BDE transfer from feed to cows' milk and tissue is important for BDE exposure assessment The fate of tri- to hexaBDEs in lactating cows exposed to a naturally contaminated diet was studied by analyzing feed, feces, and milk samples from a mass balance study. Tissue distribution was studied in one cowslaughtered afterthe experiment The carryover rates from feed to milk ranged from 0.15 to 0.35 for the major congeners. Lower values were observed for several of the tetrabrominated congeners, and this was attributed to metabolism. The dietary absorption efficiency decreased with increasing octanol-water partition coefficient of the BDE congener. The absorption behavior was consistent with a model based on chemical lipophilicity, but agreed less well with a model based on effective molecular diameter, and it violated Lipinski's "rule of 5". The lipid normalized concentrations were similar in all tissues analyzed including liver and milk, suggesting that tissue distribution is governed by partitioning into lipids. Overall, the behavior of the tri- to hexaBDEs was consistent with that observed for other classes of halogenated aromatic contaminants such as PCBs and PCDD/Fs, but it differed markedly from the behavior of the hepta- decaBDEs.

Beef and dairy products can be important vectors of human exposure to polybrominated diphenylethers (BDEs), and hence an understanding of BDE transfer from feed to cows’ milk and tissue is important for BDE exposure assessment. The fate of tri- to hexaBDEs in lactating cows exposed to a naturally contaminated diet was studied by analyzing feed, feces, and milk samples from a mass balance study. Tissue distribution was studied in one cow slaughtered after the experiment. The carryover rates from feed to milk ranged from 0.15 to 0.35 for the major congeners. Lower values were observed for several of the tetrabrominated congeners, and this was attributed to metabolism. The dietary absorption efficiency decreased with increasing octanol−water partition coefficient of the BDE congener. The absorption behavior was consistent with a model based on chemical lipophilicity, but agreed less well with a model based on effective molecular diameter, and it violated Lipinski’s “rule of 5”. The lipid normalized concentrations were similar in all tissues analyzed including liver and milk, suggesting that tissue distribution is governed by partitioning into lipids. Overall, the behavior of the tri- to hexaBDEs was consistent with that observed for other classes of halogenated aromatic contaminants such as PCBs and PCDD/Fs, but it differed markedly from the behavior of the hepta- decaBDEs.