The Lake Washington PCB/PBDE Study: Reductions Required and Recommendations

In 2010, King County was awarded a grant by the U.S. Environmental Protection Agency (EPA) to estimate total polychlorinated biphenyl (tPCB) and total polybrominated diphenylether (tPBDE) loadings to Lake Washington and from the Lake and Ship Canal to Puget Sound in Seattle Washington. The field study component of the project analyzed 146 samples for PCBs and PBDEs from 8 different matrices: (1) ambient Lake Washington water, (2) ambient Ship Canal waters, (3) three streams during both base flow and storm conditions, (4) the Cedar and Sammamish Rivers, (5) three combined sewer overflow (CSO) discharges, (6) six stormwater discharges, (7) combined wet and dry atmospheric deposition, and (8) one highway bridge discharge. Loadings estimates were developed for local drainages, major rivers, stormwater, CSOs, highways runoff and bulk deposition. Fate and bioaccumulation models were then used to describe the partitioning of the total PCB load between lake water, sediment, and biota. These models predicted a linear relationship between loadings and tissue concentrations. Coupling the loading, fate and bioaccumulation models predicts that an 85% loadings reduction is required to reduce tissue concentrations sufficiently to remove the existing WADOH consumption advisory. To achieve reductions of this magnitude, a suite of new or emerging treatment technologies in addition to aggressive source removal efforts to reduce the urban dome of PCBs in the region are going to be required in the Lake Washington watershed