Long-term environmental fate of perfluorinated compounds after accidental release at Toronto airport.

Perfluorooctane sulfonate (PFOS; a perfluorinated compound or PFC), its salts, and perfluorooctane sulfonyl fluoride have recently been listed in Annex B of the Stockholm Convention due to their widespread presence, persistence, and toxicity. Because of the persistent nature of PFCs, it is generally presumed that the impact of direct discharges of these chemicals on a receiving environment would be long-lasting. However, long-term environmental fate studies based on field measurements are rare. We examined spatial and long-term (9 year) temporal trends of PFCs in water, sediment, fish, and fish liver collected in 2003, 2006, and 2009 from 10 locations spanning ∼20 km in Etobicoke and Spring Creeks, where an accidental release of fire fighting foam containing PFOS from nearby Toronto International Airport occurred in 2000. Even a decade after the spill, sediment PFOS concentrations are still elevated in Spring Creek Pond which received the foam discharge; however, the major impact is relatively localized likely due to the stormwater management nature of the pond and the diluting effect of Etobicoke Creek. Fish and fish liver PFOS concentrations at a Spring Creek location downstream of Spring Creek Pond declined by about 70 and 85%, respectively, between 2003 and 2009. PFOS in water at locations further downstream in Etobicoke Creek have declined by >99.99% since the spill; however, the 2009 water and fish levels were ∼2-10 times higher than upstream locations likely due to the long-term impact of the spill as well as urbanization. The decrease in the upstream PFOS concentrations likely reflects the reduction of PFOS sources due to phased out production by 3M and regulations on the use of PFOS in fire fighting foams. Field-based sediment/water distribution coefficients (K(D)) and bioaccumulation factors (BAF) were calculated from environmental measurements. Log K(D) values were 0.54-1.65 for perfluoroalkyl sulfonates (PFASs) and 1.00-1.85 for perfluorocarboxylates (PFCAs). Log BAF(fish) ranged from 1.85 to 3.24 for PFASs and 0.88-3.47 for PFCAs, whereas log BAF(fish liver) ranged from 2.1-4.3 for PFASs and 1.0-5.0 for PFCAs.

Great Lakes fish consumption advisories: is mercury a concern?

The majority of the restrictive fish consumption advisories for the Canadian waters of the Great Lakes issued by the Ontario Ministry of the Environment, Canada based on the most restrictive contaminant, are attributed to polychlorinated biphenyls (PCBs) and dioxins/furans. Mercury currently causes about <1-2.5% and 9-16% of the restrictive advisories for the general population (GP) and sensitive population of children under 15 and women of child-bearing age (SP), respectively (the St. Lawrence River is not considered here). Toxaphene causes minor restrictions. At present it is not clear that if PCBs and dioxins/furans were to decrease below their fish consumption advisory guidelines, current fish mercury levels would replace some, most or all of the consumption restrictions. In order to examine this, location-, species- and size-specific fish consumption advisories were calculated for a "mercury only" scenario by disregarding the presence of the other contaminants. In the absence of other contaminants, mercury would replace some of the current advisories caused by other contaminants; however, the overall advisories would be minimally to moderately restrictive (<1-7% for GP; 13-32% for SP). Almost half of the Great Lake blocks considered here would have more than double the unrestricted consumption advisories than they currently have, with Lake Ontario showing the greatest improvement. Certain size ranges of each species across the main basins of the Canadian waters of the Great Lakes would be deemed safe for unrestricted consumption. However, at least some sizes of a number of species from certain locations of each lake would still have "do not eat" advisories issued for the SP, although these restrictions would be minimal for Lake Erie. These results suggest that the current mercury levels in the Canadian Great Lakes fish are of very minor concern for the GP and of moderate concern for the SP.

Temporal trends and spatial distribution of dioxins and furans in lake trout or lake whitefish from the Canadian Great Lakes.

Concentrations of the seventeen 2,3,7,8-substituted, most toxic congeners of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were measured in lake trout (Salvelinus namaycush) or lake whitefish (Coregonus clupeaformis) collected between 1989 and 2003 from the Canadian Great Lakes as a part of the on-going Sport Fish Contaminant Monitoring Program of the Ontario Ministry of the Environment. These monitoring data were used to assess temporal trends and spatial variations of these compounds in the Canadian Great Lakes. Toxic equivalents (TEQs) were calculated using the measured congener concentrations and toxicity equivalency factors (TEFs) published by the World Health Organization in 1998. Five congeners, namely 2,3,7,8-TCDD, 2,3,7,8-TCDF, 1,2,3,7,8-PeCDD, 1,2,3,7,8-PeCDF, and 2,3,4,7,8-PeCDF, were the most dominant congeners among the 17 congeners analyzed. The highest TEQs were found for Lake Ontario lake trout (22-54 pg g(-1)) while the TEQs for the other Canadian Great Lakes were 60-95% lower. Non-parametric Mann-Kendall and Sen's tests performed on TEQs and PCDD/Fs standardized at a mean lake trout length of 60 cm suggest a linearly decreasing trend for PCDD/Fs in lake trout from Lakes Ontario and Huron. There was no monotonously increasing or decreasing trend found for Lake Superior lake trout. The ratios of 2,3,7,8-TCDD to 2,3,7,8-TCDF concentrations were generally constant during the 1989-2003 period with the values being in the order of Lakes Superior (0.05-0.3)