PBDEs in the Environment : Time trends, bioaccumulation and the identification of their successor, decabromodiphenyl ethane

Polybrominated diphenyl ethers (PBDEs) are important chemical flame retardants, but also environmental pollutants. Their bromine substitution lends them a different bioaccumulation behaviour than the better studied organochlorines. The contamination of a Swedish lake with lower brominated BDEs was assessed by a retrospective study of pike. The concentrations of tetra- to hexaBDEs increased exponentially up to the mid-1980s and then decreased slowly, possibly reflecting the voluntary reduction in production/usage of the chemicals. Methoxylated PBDEs were found to be present in similar concentrations to the PBDEs, but originated from different sources. The large size of the bromine atom was believed to result in negligible absorption of higher brominated BDEs in wildlife, thus explaining the low levels observed in fish despite high levels in e.g. sediment. However, it was shown that the fully brominated BDE, BDE209, was absorbed to a small extent via the diet. Once absorbed, it was reductively debrominated to lower brominated BDE congeners. Debromination was also observed in dairy cows exposed to higher brominated BDEs in their natural diet. Moreover, the molecular size restricted the transfer of higher brominated BDEs to milk. In contrast to PCBs and lower brominated BDEs, there was no equilibrium between adipose tissues and milk fat, and with increasing bromine substitution a progressively smaller fraction of the ingested PBDEs was transferred to the milk. This thesis highlights differences in uptake, metabolism and excretion for PBDEs compared to the well characterized organochlorines. A knowledge that is useful for risk assessments given the ongoing use of these compounds. Furthermore, a representative of the next generation brominated flame retardants, decabromodiphenyl ethane, a replacement for the BDE209 technical product, was identified for the first time in the environment

Screening of decabromodiphenyl ethane (dbdpe) in lake sediment, marine sediment and peregrine falcon (Falco peregrinus) eggs

Dbdpe has been produced and used for more than 20 years (Umweltbundesamt, 2001). Presumably there have been considerable emissions to the environment. Nevertheless, few scientific studies have been conducted on the environmental behaviour of dbdpe since its introduction to the market. The main objective of this report is therefore to contribute to scientific understanding of the environmental behaviour and occurrence of dbdpe. The work will help to clarify whether dbdpe poses a threat to human health and wildlife. This report is built upon three studies. The first is a screening study of dbdpe in sediments from remote Swedish lakes. The objective of that screening survey was to determine whether dbdpe is present in Swedish lake sediments, and thereby available to the organisms dwelling there. Furthermore, the presence of dbdpe in remote lakes would indicate that long range atmospheric transport and deposition of dbdpe had occurred, because the remote lakes are not expected to have any point sources of BFRs. In the second study, marine sediments along a transect from Stockholm Harbour to the outer archipelago were analyzed for dbdpe. Wastewater treatment plants in Stockholm had been shown to emit dbdpe to Stockholm Harbour. The primary objective of this study was to determine if the marine benthic ecosystem outside Stockholm is exposed to dbdpe, and if so, how far out in the archipelago this exposure reaches. In the third study, Peregrine falcon eggs were analyzed for dbdpe. The eggs of this top predatory bird were hypothesized to be early indicators of dbdpe in Swedish wildlife, since they previously have been shown to accumulate high levels of decaBDE. A comparison of dbdpe and decaBDE concentrations in Peregrine falcon eggs would give information about the relative bioaccumulation potential of these two chemicals

Occurrence and Seasonality of Cyclic Volatile Methyl Siloxanes in Arctic Air

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° N, 12° 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/m3, respectively, and 2.94 ± 0.46 and 0.45 ± 0.18 ng/m3 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.acceptedVersio

Junge relationships in measurement data for cyclic siloxanes in air

In 1974, Junge postulated a relationship between variability of concentrations of gases in air at remote locations and their atmospheric residence time, and this Junge relationship has subsequently been observed empirically for a range of trace gases. Here, we analyze two previously-published datasets of concentrations of cyclic volatile methyl siloxanes (cVMS) in air and find Junge relationships in both. The first dataset is a time series of concentrations of decamethylcyclopentasiloxane (D5) measured between January and June, 2009 at a rural site in southern Sweden that shows a Junge relationship in the temporal variability of the measurements. The second dataset consists of measurements of hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4) and D5 made simultaneously at 12 sites in the Global Atmospheric Passive Sampling (GAPS) network that shows a Junge relationship in the spatial variability of the three cVMS congeners. We use the Junge relationship for the GAPS dataset to estimate atmospheric lifetimes of dodecamethylcyclohexasiloxane (D6), 8:2–fluorotelomer alcohol and trichlorinated biphenyls that are within a factor of 3 of estimates based on degradation rate constants for reaction with hydroxyl radical determined in laboratory studies.ISSN:0045-6535ISSN:1879-129

Organic Carbon/Water and Dissolved Organic Carbon/Water Partitioning of Cyclic Volatile Methylsiloxanes: Measurements and Polyparameter Linear Free Energy Relationships

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 (<i>K</i>_OC) and between Aldrich humic acid dissolved organic carbon and water (<i>K</i>_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 <i>K</i>_OC of octamethylcyclotetrasiloxane (D₄), decamethylcyclopentasiloxane (D₅), and dodecamethylcyclohexasiloxane (D₆) were 5.06, 6.12, and 7.07, and log <i>K</i>_DOC were 5.05, 6.13, and 6.79. To our knowledge, our measurements for <i>K</i>_OC of D₆ and <i>K</i>_DOC of D₄ and D₆ 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 log<i>K</i>_OC 0.76 and for log<i>K</i>_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 (log<i>K</i>_OC RMSE_cVMS: 0.09, log<i>K</i>_DOC RMSE_cVMS: 0.12). The PP-LFERs we have developed here should be further evaluated and perhaps recalibrated when experimental data for other siloxanes become available

Evaluating the Salting-Out Effect on the Organic Carbon/Water Partition Ratios (<i>K</i>_OC and <i>K</i>_DOC) of Linear and Cyclic Volatile Methylsiloxanes: Measurements and Polyparameter Linear Free Energy Relationships

Dissolved inorganic salts influence the partitioning of organic chemicals between water and sorbents. We present new measurements of the salting-out constants (<i>K</i>^s) for partition ratios between water and organic carbon (<i>K</i>_OC) and between water and dissolved organic carbon (<i>K</i>_DOC) of three cyclic volatile methylsiloxanes (cVMS), two linear volatile methylsiloxanes (lVMS), three polychlorinated biphenyls (PCBs), and α-hexachlorocyclohexane (α-HCH). <i>K</i>^s, <i>K</i>_OC, and <i>K</i>_DOC were derived from volatilization rates of the chemicals from mixtures of water and organic carbon with varying concentrations of sodium chloride in a purge-and-trap system. <i>K</i>_OC and <i>K</i>_DOC values at different salinities were determined by fitting their values to reproduce observed volatilization rates using a fugacity-based multimedia model and assuming first-order kinetics for volatilization. The <i>K</i>^s values of cVMS and lVMS ranged from 0.16–0.76. The log <i>K</i>_OC of cVMS and lVMS in fresh water interpolated from our measurements ranged from 5.20 to 7.36 and the log <i>K</i>_DOC values from 5.04 to 6.72. Polyparameter linear free energy relationships (PP-LFERs) trained with data sets without measurements for siloxanes failed to accurately describe the log <i>K</i>_OC and log <i>K</i>_DOC of cVMS and lVMS. Including our measurements for cVMS and lVMS substantially improved the fit. PP-LFERs trained with data for <i>K</i>^s from solubility measurements do not describe our new measurements well regardless of whether or not they are included in the training set, which may reflect differences in the salting-out effect on partitioning to organic carbon versus on solubility