No abstract

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.

No abstract

It is widely accepted that a congener-specific analysis of polychlorinated biphenyls (PCBs), rather than traditional Aroclor equivalent total PCB analysis, is required for risk assessment. This is based on the fact that environmental processes alter the original distribution of PCB congeners in Aroclors and that toxicity varies considerably among the congeners with dioxin-like PCBs (dl-PCBs) generally being among the most toxic. Using the largest known dl-PCB fish dataset, here we present a likely composition of dl-PCBs in fish. In contrast to common perception, we found that the dl-PCB composition is relatively constant (within approximately a factor of 2) regardless of fish species and total PCB level. The abundance of dl-PCBs expressed as a percentage of total PCB (25-75 quartile range) in fish is generally in the order of PCB-118 (3.0-6.2%) > PCB-105 (1.1-2.4%) > PCB-156 (0.39-0.75%) > PCB-167 (0.20-0.43%) > PCB-123 (0.11-0.26%) > PCB-157 (0.09-0.19%) = PCB-114 (0.08-0.18%) > PCB-189 (0.045-0.094%) > PCB-77 (0.018-0.093%) > PCB-126 (0.015-0.036%) > PCB-81 (0.002-0.007%) = PCB-169 (0.001-0.006%). The most toxic dl-PCB congeners PCB-126 and -169 contribute on average only 0.027 and 0.004% of total PCB, respectively. The statistically significant relationships presented between individual di-PCB and total-PCB concentrations can be used as a practical tool to estimate dl-PCBs for risk assessment purposes. A comparison of the dl-PCB pattern presented here with other studies suggests that this dl-PCB composition is applicable to fish from North America and perhaps from other geographical regions throughout the world.