PSU study finds Oregon oysters contain drugs, other toxins
Author: Laura Gleim
Posted: May 2, 2016

Dr. Elise Granek and PSU student Dominic Galen prepare oysters for testing.

(Portland, Ore.) May 2, 2016 — A new study led by Portland State University researchers finds that native Olympia oysters in Coos and Netarts bays contain a cocktail of pharmaceuticals and other potentially harmful chemicals—including pain relievers, antibiotics, antihistamines, PCBs, mercury and pesticides. 

The chemicals enter the bays via groundwater runoff and wastewater that’s discharged to inland rivers and eventually end up in the ocean. Air pollution deposited on the water may also be a source, especially for heavy metals like mercury.

The PSU-led research team, which includes researchers from the U.S. Geological Survey, Oregon Department of Fish and Wildlife, and Oregon Department of Environmental Quality, found that individual concentrations of chemicals are within the safe levels designated by the Oregon Health Authority. However, the health risks of consuming seafood that contains a combination of these chemicals are unknown, as are the ecological effects.

“There are no federal or state guidelines for screening consumption of multiple contaminant types,” said Elise Granek, associate professor of Environmental Science and Management and fellow of the Institute for Sustainable Solutions at Portland State. “We’ve found oysters that contain pharmaceuticals, carcinogenic compounds and mercury, and we don’t know the effects or synergies of taking this combination of drugs and chemicals together. Commercial and native oysters may contain similar contaminants because the two species both filter their food out of the surrounding water.”

Researchers also found that levels of mercury in the oysters were higher than is present in oysters from the Gulf of Mexico or the coast of France, though still within the Oregon Department of Environmental Quality standard and Oregon Health Authority screening levels. 

The researchers collected and analyzed oysters and estuary sediment from Coos Bay and Netarts Bay and found that types and levels of certain contaminants varied from one bay to the other, as well as from one season to another.

Oregon has two species of oysters—the native Olympia oyster and the commercial Pacific oyster. Harvest of wild stocks of Olympia oysters are prohibited in Oregon due to historically low population levels, though both Olympia and Pacific oysters are commercially raised and harvested for consumption. The study focused only on the native Olympia oyster, which has faced dramatic population decline since the late 1800s. 

“In addition to potential human health risks, the pollutants may affect the growth and reproduction of the oysters themselves—with possible widespread repercussions since oysters play important ecological roles of filtering water and providing habitat for other estuarine and marine species like juvenile salmon,” said Granek.

Granek has applied for grants to further research the effects of wastewater effluent on oysters in Coos Bay and also to study whether eating contaminated seafood leads to measurable levels of the same contaminants in the human bloodstream.

Funding for the research was provided by Oregon Sea Grant and the Oregon Community Foundation. Results of the study were published in the Science of the Total Environment at: .