20 Years of Air-Water Gas Exchange Observations for Pesticides in the Western Arctic Ocean.

The Arctic has been contaminated by legacy organochlorine pesticides (OCPs) and currently used pesticides (CUPs) through atmospheric transport and oceanic currents. Here we report the time trends and air-water exchange of OCPs and CUPs from research expeditions conducted between 1993 and 2013. Compounds determined in both air and water were trans- and cis-chlordanes (TC, CC), trans- and cis-nonachlors (TN, CN), heptachlor exo-epoxide (HEPX), dieldrin (DIEL), chlorobornanes (ΣCHBs and toxaphene), dacthal (DAC), endosulfans and metabolite endosulfan sulfate (ENDO-I, ENDO-II, and ENDO SUL), chlorothalonil (CHT), chlorpyrifos (CPF), and trifluralin (TFN). Pentachloronitrobenzene (PCNB and quintozene) and its soil metabolite pentachlorothianisole (PCTA) were also found in air. Concentrations of most OCPs declined in surface water, whereas some CUPs increased (ENDO-I, CHT, and TFN) or showed no significant change (CPF and DAC), and most compounds declined in air. Chlordane compound fractions TC/(TC + CC) and TC/(TC + CC + TN) decreased in water and air, while CC/(TC + CC + TN) increased. TN/(TC + CC + TN) also increased in air and slightly, but not significantly, in water. These changes suggest selective removal of more labile TC and/or a shift in chlordane sources. Water-air fugacity ratios indicated net volatilization (FR > 1.0) or near equilibrium (FR not significantly different from 1.0) for most OCPs but net deposition (FR < 1.0) for ΣCHBs. Net deposition was shown for ENDO-I on all expeditions, while the net exchange direction of other CUPs varied. Understanding the processes and current state of air-surface exchange helps to interpret environmental exposure and evaluate the effectiveness of international protocols and provides insights for the environmental fate of new and emerging chemicals.

A Decade of Global Atmospheric Monitoring Delivers Mixed Report Card on the Stockholm Convention.

Time trends in atmospheric concentrations serve to evaluate how effective the Stockholm Convention is in reducing or eliminating environmental releases of persistent organic pollutants (POPs). Twelve years (2005-2016) of continuous monitoring with a global network of 20 sampling sites reveals that concentrations of the pesticide endosulfan began to drop coincident with its listing as POP in 2011. Concentrations of other POPs started to decrease prior to listing and during the sampling period declined very slowly or not at all. Concentrations of some unintentionally produced POPs (hexachlorobenzene, hexachlorobutadiene) increased to become the most abundant and most widely dispersed POPs in the global atmosphere. Their formation processes and release locations need to be identified to facilitate the Convention's goal of curbing releases from unintentional production.

A multi-pathway exposure assessment for polycyclic aromatic hydrocarbons among residents in the Athabasca oil sands region, Canada.

Due to increasing emissions from ongoing development of the oil sands in Northern Alberta, Canada, there is concern that local residents and organisms are experiencing elevated exposures to hazardous contaminants. We modified an existing human bioaccumulation model (ACC-Human) to represent the local food chain in the Athabasca oil sands region (AOSR), the focus of oil sands development in Alberta. We used the model to assess the potential exposure to three polycyclic aromatic hydrocarbons (PAHs) among local residents that have a high intake of locally sourced traditional foods. To place these estimates into context, we complemented them with estimated PAH intake through market foods and smoking. Our approach was able to produce realistic body burdens of the PAHs in aquatic and terrestrial wildlife and in humans, both in magnitude and with respect to the relative difference between smokers and non-smokers. Over the model simulation period (1967-2009), market food was the dominant dietary exposure route for phenanthrene and pyrene, while local food, and in particular local fish, dominated the intake of benzo[a]pyrene. Exposure to benzo[a]pyrene therefore was also predicted to increase over time in concert with expanding oil sands operations. Those smoking at the average rate of Northern Albertans take in an additional amount of all three PAHs that is at least as large as dietary intake. Estimated daily intake rates are below toxicological reference thresholds for all three PAHs. However, daily intake of BaP in adults is only ∼20 fold below those thresholds and is predicted to increase. Key uncertainties in the assessment included the effect of food preparation on the PAH content in food (e.g., smoking of fish), the limited availability of market food contamination data specific to Canada, and the PAH content of the vapor phase of first-hand cigarette smoke. Considering the satisfactory model evaluation, ACC-Human AOSR should be suited to making predictions of future contaminant exposure based on development scenarios in the AOSR or in response to potential emission reduction efforts. It should also be applicable to other organic contaminants of concern released by oil sands operations.

Atmospheric concentrations and loadings of organochlorine pesticides and polychlorinated biphenyls in the Canadian Great Lakes Basin (GLB): Spatial and temporal analysis (1992-2012).

Long-term air monitoring data for POPs are required to determine the effectiveness of source reduction measures and factors controlling air concentrations. Air samples were collected between 1992 and 2012 at three sites with different geographical characteristics (Burnt Island, Egbert and Point Petre) in the Canadian Great Lakes Basin (GLB) using high-volume samplers and analyzed for organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs). Spatial and temporal trends of gas-phase concentrations of OCPs, selected PCB congeners and Æ©PCBs (84 congeners) were assessed. Egbert had the highest concentrations of some OCPs due to historical [dichlorodiphenyltrichloroethanes (DDTs), dieldrin, γ-hexachlorocyclohexane (γ-HCH)] and current (endosulfan) applications of these pesticides in the surrounding agricultural cropland. This shows that agricultural areas are a source of OCPs to the GLB. High o,p'-/p,p'-DDT ratios were determined and an increasing trend was observed at Point Petre and Burnt Island up to 2004; indicating that the GLB is influenced by dicofol-type DDT sources, which have higher o,p'-/p,p'-DDT ratios than technical DDT. Atmospheric PCB concentrations at Egbert and Point Petre are higher than those measured at Burnt Island, likely due to urban influence and greater populations. Loadings calculations suggest that the atmosphere is a source of α-endosulfan and p,p'-DDT to the lakes and the opposite is true for p,p'-DDE. Long-term decreasing trends were observed for both OCPs and PCBs; consistent with control measures implemented in North America. Atmospheric PCB concentrations are decreasing relatively slowly, with halflives in the range of 9-39 years. Chlordane, α-endosulfan, ß-endosulfan, dieldrin, and DDT-related substances showed halflives in the range of 7-13 years. α-HCH and γ-HCH were decreasing rapidly in air, with halflives of 5 years. Long-term declining trends of PCBs and OCPs suggest that regulatory efforts to reduce emissions to the GLB environment have been effective, but emissions from primary and secondary sources might limit future declines.

Using quantitative structural property relationships, chemical fate models, and the chemical partitioning space to investigate the potential for long range transport and bioaccumulation of complex halogenated chemical mixtures.

Some substances are mixtures of very large number of constituents which vary widely in their properties, and thus also in terms of their environmental fate and the hazard that they may pose to humans and the environment. Examples of such substances include industrial chemicals such as the chlorinated paraffins, technical pesticides such as toxaphene, and unintended combustion side products, such as mixed halogenated dibenzo-p-dioxins and dibenzofurans. Here we describe a simple graphical superposition method that could precede a more detailed hazard assessment for such substances. First, partitioning and degradation properties for each individual constituent of a mixture are estimated with high-throughput quantitative structure-property relationships. Placed in a chemical partitioning space, i.e. a coordinate system defined by two partitioning coefficients, the mixtures appear as 'clouds'. When model-derived hazard assessment metrics, such as the potential for bioaccumulation and long range transport, are superimposed on these clouds, the resulting maps identify the constituents with the highest value for a particular parameter and thus potentially the greatest hazard. The maps also indicate transparently how the potential for long range transport and bioaccumulation is dependent on structural attributes, such as chain length, and the degree and type of halogenation. In contrast to previous approaches, in which the mixture is represented by a single set of properties or those of a few selected constituents, the whole range of environmental fate behaviors displayed by the constituents of a mixture are being considered. The approach is illustrated with three sets of chemical substances.

Global pilot study of legacy and emerging persistent organic pollutants using sorbent-impregnated polyurethane foam disk passive air samplers.

Sorbent-impregnated polyurethane foam (SIP) disk passive air samplers were deployed alongside polyurethane foam (PUF) disk samplers at 20 sites during the 2009 spring sampling period of the Global Atmospheric Passive Sampling (GAPS) Network. The SIP disk samplers consisted of PUF disks impregnated with finely ground XAD-4 resin. The addition of XAD-4 greatly improves the sorptive capacity of the PUF disk samplers for more volatile and polar chemicals, and allows for linear-phase sampling over several weeks for these compounds. The SIP and PUF disks were analyzed for polychlorinated biphenyls (PCBs), neutral polyfluoroalkyl compounds (PFCs), and ionic PFCs. Correlations between sampler-derived air concentrations for PCBs in the PUF and SIP disks samplers were significant (p < 0.05). The SIP disks effectively captured 4-50% more of the low molecular weight PCBs than the PUF disks samplers, and the PUF disks also had limitations for time-weighted passive sampling of neutral PFCs in air. Theoretical uptake curves for PUF disks showed rapid equilibration occurring in just hours for 8:2 FTOH and in a few days for MeFOSE, while theoretical curves for SIP disks showed superior sampling profiles for the neutral PFCs. PFCs were measured on SIP disks at all sites with 8:2 FTOH being the dominant compound detected and urban centers (n = 3) having the highest total neutral PFC concentrations ranging from 51.7 to 248 pg/m(3). A positive correlation was found between the FTOHs and FOSAs/FOSEs (p < 0.001, Pearson correlation) indicating similar contamination sources. The SIP disk appears to be a promising passive air sampler for measuring both emerging and legacy POPs on a global scale. They can also be used as a complement to the PUF disk sampler for capturing broader classes of compounds, or as a replacement for PUF disks entirely, especially when longer than quarterly deployment periods are desired.