A video produced by the University of Washington Center for Urban Waters shows how chemical tracers can identify sources of pollution affecting shellfish growers in Puget Sound’s Skagit Valley.

Fecal coliform pollution is a widespread problem in Puget Sound, resulting in costly beach and shellfish bed closures whenever it is detected. Analytical techniques can now reveal whether polluted water came from humans or livestock, an often contentious issue when cleaning up contaminants. If scientists can find traces of chemicals such as caffeine or cough syrup, they know to look for human sources. In other cases, the presence of certain antibiotics might suggest that the source was livestock.

PSI senior scientist Andy James is leading a project to conduct this analysis in Samish Bay in collaboration with Skagit County Public Works. Funding for the research was provided by the U.S. Environmental Protection Agency.