On July 19, the Oregon Department of Environmental Quality announced it found elevated levels of dioxins in sediment in the Willamette Slough. These levels exceeded DEQ’s human health and ecological screening levels and caused the agency to warn that eating fish from the slough might be unsafe.

The slough is posted while DEQ continues to investigate.

Dioxins are carcinogenic industrial contaminates which break down very slowly. They are found at low levels from natural processes like forest fires, but are dangerous at higher levels.

The screening level for dioxins is 0.001 parts per trillion. Recent testing of slough sludge showed 5.5 – 67.9 parts per trillion.

“The elevated levels of dioxins found in the Willamette Slough may be related to past industrial activities in the area,” DEQ said in July, “including the chlorine bleaching process used at a pulp and paper mill operated by Boise Cascade.”

Boise Cascade operated a mill beside the Slough from 1962 – 2007 and in 2000, the company itself conducted a study that showed elevated levels of dioxins. Later that year, DEQ found that no action on the contaminates was required.

The mill employed several practices that caused pollution, including the chlorine bleaching process known to create dioxins and also by building settling lagoons for liquid waste on Minto-Brown Island, across from the slough. As a result, environmentalists have long expressed concern that dioxin would be found in the sludge.

Two weeks after the July 2016 announcement, Michael Kucinski, DEQ’s Cleanup and Tanks Program Manager for the Western Region, says the agency is still involved in the matter and results may not be known this year.

“DEQ is continuing to work with Boise Cascade to determine the level of risk to public health and the environment,” Kucinski said.

Additional study may include: conducting fish tissue sampling, evaluating how much fishing takes place in the area, further delineating the extent of the contamination and assessing background conditions in the area. “If DEQ finds that dioxin levels are unsafe, the public will be advised about the safety of eating fish caught from the area,” Kucinski adds.  The agency will conduct longer-term studies to focus on the risks to human health and the environment, and the need for specific cleanup actions.

“Additional testing could take months to complete,” Kucinski says, “so DEQ might not have more information about the safety of eating fish until early next year. If DEQ finds that dioxin levels in fish are unsafe, we will work with the Oregon Health Authority on a public health advisory.”

Until then, the area remains posted.