During the 1950's and 1960's, radioactivity from Hanford was found at high concentrations in shellfish in Willapa Bay at the mouth of the Columbia which extended for at least 200 miles into the Pacific Ocean. Beginning in 1959, zinc-59 levels in the oysters at Willapa Bay were being monitored. At that time, levels of zinc-65, a radioactive byproduct of plutonium production, in Pacific coast oysters were 300 times greater oysters from Japanese and Atlantic waters. In the 1960's a Hanford employee set off radiation alarms when he entered the Hanford Site. Upon investigation it was determined that he had become radioactive from eating a can of oyster stew that contained oysters harvested from Willapa Bay.

References

http://www.hanfordchallenge.org/cmsAdmin/uploads/2008_Fish_at_Risk_-_Hanford_and_the_Columbia_River.pdf

http://www.doh.wa.gov/hanford/publications/overview/columbia.html#VC2i3