Final Report: BUI Delisting Studies in the Niagara River AOC, 2014-2015

Abstract

From 8 December 2013 to 6 April 2015, 24 mink were caught in the Niagara River AOC, 12 upriver and 12 downriver from Niagara Falls. Average concentrations of total mercury in mink brain and PAH REP in mink liver were 22 and 201 times lower, respectively, than their LOAELs for deformities or reproductive impairment. The average concentration of total PCB in mink liver was 1.15 times higher than the LOAEL for deformities or reproductive impairment, but two mink (one caught upriver and one downriver from Niagara Falls) had very high concentrations of both total PCB and total TEQ (mostly comprised of PCB TEQ). Average concentrations of PCB TEQ and CDD/CDF TEQ in mink liver were 2.9 times higher and 2.9 times lower, respectively, than their LOAELs for deformities or reproductive impairment. The average concentration of total TEQ (sum of PCB, CDD/CDF and PAH) in mink liver was 3.3 times higher than the LOAEL for deformities or reproductive impairment. Mink are one of the most sensitive mammals to CDD/CDF and co-planar PCB congeners, and 67% of the mink trapped in the NR AOC exceeded one or both of the published LOAELs for deformities or reproductive impairment for total PCB and total TEQ. Yet mink are reasonably abundant in suitable habitats in the AOC; thus they are either reproducing there or migrating in from adjacent areas with lower contaminant exposures. The most sensitive biomarker of mink health after exposure to total PCB or total TEQ is the presence of pre-cancerous tissues associated with the jawbone. Of the nine mink with the highest total PCB or total TEQ concentrations, two (22%) had the mildest form and one (11%) had the most severe form of this condition. All of the affected mink were captured in the lower river below Niagara Falls. For the “Bird or Animal Deformities or Reproductive Problems” BUI, in terms of mink health in the NR AOC, it appears that the time for delisting is not yet at hand.