Oregon Public Broadcasting

New research shows bald eagles on the Columbia River are benefiting from a regulation that removed toxins from paper mill wastewater in the 1990s.

U.S. Fish and Wildlife Service research shows bald eagle eggs collected last year have dramatically lower levels of the contaminant dioxin than they did 15 years ago. 

Jeremy Buck is a contaminant specialist for the Fish and Wildlife Service. He says that high concentrations of dioxin can weaken bald eagle egg shells and kill the babies before they hatch. So Buck was pleased when he examined a new set of bald eagle eggs collected last year. The levels of dioxin were down by an average of 75 percent.

"We've seen a dramatic decline in dioxin concentrations that presumably are a direct result of that regulation that the EPA passed in the 1990s, so that's a really good thing for eagles," Buck said.

The U.S. Environmental Protection Agency required pulp and paper mills to reduce the dioxin they release into the Columbia to protect fish and wildlife in 1991.

Buck's recent research also shows that dioxin levels in the eggs didn't drop as much in one area of the lower river. Eggs from the lower estuary -- between Astoria and Cathlamet -- had higher levels of dioxin than the ones farther upriver.

Mary Lou Soscia is the Columbia River manager for the EPA. She says that may reflect the fact that the river naturally dumps sediment from the rest of the basin as it widens at that stretch - including toxins from all over the region.

"The estuary is the bottom of the river, and we might fully expect that the toxics that are discharged throughout the Columbia River Basin might end up in higher quantities," Soscia said.

Bald eagle reproduction rates are still improving in the estuary as contaminant levels drop, Buck said. But the eggs in that area are still less likely to hatch than they are elsewhere in the region.

This story originally appeared on news.opb.org.