Zinc, boat paint, and Puget Sound

Washington is working to enact laws that protect Puget Sound from toxic chemicals. Part of this work involves identifying sources of contamination which impact aquatic life and ensuring that implementation of legislation does not create new problems. It is important to consider the impact of regulation of one hazardous chemical on the use and release of other hazardous chemicals as part of a pollution reduction strategy. Zinc and copper are both harmful to aquatic life and are present, through various sources, in Puget Sound. Previous estimates of zinc loading to Puget Sound did not include recreational boat paints so Washington needed to know how boat paints contribute to contamination levels.

In this report, NGC assessed loading of zinc from zinc oxide from recreational antifouling boat paint for two scenarios, status quo and under the upcoming copper ban, and reported results to the Washington State Department of Ecology. NGC used a loading estimation method to calculate and compare changes in zinc loading upon the phase-out of copper in recreational antifouling boat point. This method can be further used to explore other potential regulatory changes and how changes impact zinc loading, as well as other hazardous chemicals in boat paint, like VOCs and other biocides.

NGC's report reveals that boat paint, though worst-case scenarios place it among top ten sources of zinc to Puget Sound, accounts for less than 1% of total zinc loading to Puget Sound. Ecology is looking further into improved estimates of zinc loading from other sources, particularly urban runoff from building roofing and siding, chain-link fencing, streetlights, and roof gutters.