Neutral polyfluoroalkyl substances in the global atmosphere.

Concentrations of neutral per- and polyfluoroalkyl substances (nPFAS) in the atmosphere are of interest because nPFAS are highly mobile percursors for perfluoroalkyl acids. Two calibration studies in Ontario, Canada and Costa Rica established the feasibility of using XAD 2-resin based passive air samplers (XAD-PAS) to reliably determine long term average air concentrations of nPFAS under temperate and tropical climatic conditions. The temporal and spatial distribution of nPFAS was investigated by analyzing XAD-PAS deployed for one year at between 17 and 46 sites on six continents between 2006 and 2011 as part of the Global Atmospheric Passive Sampling (GAPS) study. Higher levels of fluorotelomer alcohols (FTOHs) compared to fluorinated sulfonamides (FOSAs), and fluorinated sulfonamidoethanols (FOSEs) were observed at all sites. Urban sites had the highest levels of nPFAS compared to rural and remote sites, which is also apparent in a positive correlation of nPFAS levels with the proximity of a sampling site to areas of high population density. Levels of FOSAs and FOSEs tended to decrease during the six years of measurements, whereas an initial decline in the concentrations of FTOHs from 2006 to 2008 did not continue in 2009 to 2011. A comparison of nPFAS levels measured in national XAD-PAS networks in Costa Rica and Botswana revealed that the GAPS sites in Tapanti and the Kalahari are representative of the more remote regions in those countries. XAD-PAS derived absolute nPFAS levels at GAPS sites are lower than those measured using another PAS, but are within the range of levels measured with active air samplers. Agreement of relative nPFAS composition is better between samplers, suggesting that the discrepancy is due to uncertain sampling rates.

The effect of different gamma doses on some properties of a CR-39 detector.

In the current study, the bulk etch rate, the removal thickness percentage and the track density have been examined for gamma-irradiated at doses ranging from 0 to 100 kGy. After irradiating CR-39 detectors, they got etched at 70°C in different concentration of NaOH solutions for various time intervals. Results indicate that the bulk etch rate and the removal thickness percentage increase with the increase of gamma absorbed dose and the etchant solution concentration. The track density increases with increase of the etchant solution concentration for irradiated samples (0, 10, 50 kGy) up to 6.25 N NaOH, and then it decreases with the increase of the etchant solution concentration for un-irradiated samples and those irradiated with 10 kGy, and with the high doses the samples' surface got damaged.

Perfluorinated chemicals in the arctic atmosphere.

Twenty high-volume air samples were collected during a crossing of the North Atlantic and Canadian Archipelago in July 2005 to investigate air concentrations of fluorotelomer alcohols (FTOHs) and perfluoalkyl sulfonamido ethanols (PFASs). These commercial chemicals are widely used as surface treatments and are believed to be precursors for perfluorocarboxylic acids (PFCAs) and perfluorooctane sulfonate (PFOS) that accumulate in humans and biota, including those from remote arctic regions. The highest concentrations (sum of gas- and particle-phase) of FTOHs were for 8:2 FTOH (perfluoroctyl ethanol) (5.8-26 pg/m(3)), followed by 10:2 FTOH (perfluorodecyl ethanol) (1.9-17 pg/ m(3)) and 6:2 FTOH (perfluorohexyl ethanol) [BDL (below detection limit) to 6.0 pg/m(3)]. For the PFASs, MeFOSE (N-methyl perfluorooctane sulfonamido ethanol) was dominant and ranged from 2.6 to 31 pg/m(3); EtFOSE (N-ethyl perfluorooctane sulfonamido ethanol) ranged from BDL to 8.9 pg/m(3) and MeFOSEA (N-methyl perfluorooctane sulfonamide ethylacrylate) was BDL in all samples. Air parcel back-trajectories showed that the sampled air was largely representative of the arctic air mass. Air concentrations of target compounds were of the same order of magnitude as reported air concentrations in source regions. For instance, the mean 8:2 FTOH concentration was only a factor of about 3 lower than for three urban samples that were collected in Toronto for comparison. These findings confirm model results that predictthe efficient, long-range atmospheric transport and widespread distribution of FTOHs and related compounds in the arctic region. Mean particulate percentages for FTOHs and PFASs in the cruise samples (mean temperature, 5+/-4 degrees C) were BDL for 6:2 FTOH, 23% for 8:2 FTOH, 15% for 10:2 FTOH, 32% for MeFOSE, and 22% for EtFOSE. Further, the partitioning to particles for MeFOSE and EtFOSE was significantly correlated with inverse absolute temperature, whereas the FTOHs did not show this trend. The Toronto samples (mean temperature, -1+/-1 degree C) showed similar particulate percentages for MeFOSE and EtFOSE; however, the FTOHs were substantially less particle-bound. Although the mechanism for this partitioning is not understood, the results do indicate the need to better account for particle phase transport when modeling the atmospheric fate of these chemicals.

Field deployment of thin film passive air samplers for persistent organic pollutants: a study in the urban atmospheric boundary layer.

This paper reports on the first field deployment of rapidly equilibrating thin-film passive air samplers under ambient conditions. The POlymer-coated Glass (POG) samplers have a coating of ethylene vinyl acetate (EVA) less than 1 microm thick applied to a glass surface. This can be dissolved off after exposure and prepared for the quantification of persistent organic pollutants (POPs) that have partitioned into the film during field exposure. In this study, POGs were deployed at various heights on the CN Tower in Toronto, Canada, to investigate the vertical distribution of selected compounds (PCBs, PAHs, organochlorine pesticides) in the atmospheric boundary layer of an urban area. The feasibility of the method to detect POPs from a few cubic meters of air was demonstrated, indicating the potential for rapid, low-volume sampling of air for ambient levels of POPs. PAH levels declined sharply with height, confirming ground-level emissions in urban areas as sources of these compounds; PCBs did the same, although less strongly. Different sampling events detected different vertical distributions of OC pesticides which could be related to local or distantsources, and variations in POPs on the samplers in these different events/heights demonstrate the dynamic nature of sources and atmospheric mixing of POPs.

Studies of toxaphene in technical standard and extracts of background air samples (Point Petre, Ontario) using multidimensional gas chromatography-electron capture detection (MDGC-ECD).

MDGC-ECD procedures have been used to provide insight into the compositional complexity of some of the specific peaks or clusters observed in the gas chromatographic analysis of a technical toxaphene standard, with reference to individual toxaphene congeners (Parlar # components) that are flow commercially available. These investigations have focussed initially upon those peaks and clusters recently identified (Shoeib. M., Brice, K.A., Hoff, R., 1999. Chemosphere 39, 849-871) as dominant constituents of background ambient air. Multiple electron-capturing components have been found to be present in all the species studied: the available individual toxaphene congeners have been matched against these components where possible. In similar fashion, the responses obtained in equivalent gas chromatographic elution windows from the analysis of typical processed air sample extracts have been investigated, with the results showing clear differences relative to the patterns found in the technical toxaphene standard. In most cases, the air sample shows reduced complexity with fewer components present in the cluster. Also, the presence of interfering responses (due to PCBs and other organochlorines) is quite apparent and significant, showing that major problems and errors could arise when using single-column GC-ECD procedures for quantitation of toxaphene in environmental samples. The presence of certain of the Parlar species in the air samples has been confirmed and in most cases these represent the dominant toxaphene component found in the targeted cluster. Furthermore, the persistence of certain congeners in the atmospheric samples appears to be strongly dependent upon chemical structure, since the congeners in question possess an alternating exo-endo chlorine substitution pattern around the six-membered ring in the bornane skeleton. Such persistence is probably the result of lower metabolization of toxaphene residues in soils, water and sediments leading to a similar pattern in the atmosphere following volatilization.

Airborne concentrations of toxaphene congeners at Point Petre (Ontario) using gas-chromatography-electron capture negative ion mass spectrometry (GC-ECNIMS).

A reliable analytical method has been developed using GC-ECNIMS for the determination of individual toxaphene congeners in ambient air. To allow a reasonable comparison with previous data for toxaphene reported by Muir and co-workers using GC-ECD, this method has adopted their approach of focussing upon the identification and quantification of specific peaks or clusters ("T" species) typically observed in environmental samples, with the sum of these "T" species then being reported as "total toxaphene". Technical toxaphene has been used as the analytical standard, but independent response factors have been assigned to the target peaks and clusters. Because of the appreciable variability in ECNIMS response shown by individual toxaphene congeners, this is considered to be a reasonable and potentially more accurate procedure than the application of a "single response factor" used by many other workers. The methodology has been used for the determination of toxaphene in air samples collected over the annual cycle in 1992 and then from October 1995 to September 1997 at Point Petre, Ontario. Of the forty-four calibrated components, only 10 were detected in all of the air samples collected over the latter 2-year period. Airborne concentrations of toxaphene (defined as the sum of the calibrated components) range from 0.9 pg/m3 to 10.1 pg/m3. A clear seasonality has been observed, with a summer-to-winter concentration ratio of about 6.

The effect of NSAID on T-cell ratios in marginal periodontitis.

The use of NSAID in the treatment of periodontal disease can augment the conventional periodontal therapy. NSAID can block prostaglandin synthesis which is responsible for the progression of periodontal disease. Inhibition of prostaglandin synthesis reduces the alveolar bone loss, loss of attachment, gingival inflammation and consequently pocket depth. Results of the present study show that the use of NSAID increases the T-cell ratios indicating an improvement of T-cell function which is represented clinically by the reduction in G.I scores.