The primary causes are high temperature and fecal coliform bacteria from agricultural activities and stream habitat modification. High water body temperatures kill fish by reducing the amount of oxygen in the water. The report lists by watersheds water bodies that were assessed. For example, in the Nooksack Watershed in Whatcom County, the Nooksack River is listed as having chromium, mercury, fecal coliform, fine sediment, instream flow, and temperature. Chromium and mercury are heavy metals that accumulate in the water and in living organisms and are highly toxic if breathed or swallowed and can damage living things even at low concentrations.
Fine sediments are soil particles that can hurt fish spawning areas.
The Snohomish River is listed for heavy metals. PAH's come from petroleum products and combustion of other organic materials. PCB's, now banned, were once used in electrical transformers and persist in the environment. Also listed for PCB's are Bellingham Bay and Whatcom Waterway, Saratoga Passage, Port Gardner and Inner Everett Harbor, Elliott Bay, Duwamish Waterway and River, Mercer Slough, Lake Union, Budd Inlet, Inner and Outer Commence-ment Bay, Foss Waterway, Sinclair Inlet, Dyes Inlet, Port Gamble Bay, Liberty Bay, Port Angeles Harbor, the Elwha River, and Port Orchard, Agate Passage, Rich Passage and Tacoma Narrows. The bays and inlets above are also listed for pesticide contamination.