Levels of toxic flame retardants found in fish tissue collected from the Spokane River appear to be dropping, and the amount detected in osprey eggs doesn’t seem to jeopardize their ability to develop into healthy chicks, two new studies suggest.
The studies were done cooperatively by the Washington Department of Ecology and the U.S. Geological Survey. The research follows a 2005 study that detected the highest known levels of flame retardants in the state in Spokane River fish.
The studies, released Tuesday, show flame retardant levels in fish tissue dropping by as much as 50 percent between 2005 and 2009. Scientists also studied the eggs of osprey, a fish-eating raptor, because flame retardants accumulate in fat and move up the food chain.
Jani Gilbert, an Ecology spokeswoman, attributed the declines to a gradual phase-out of harmful flame retardants.
“They’re a legacy pollutant and they’re not being used in manufacturing anymore,” she said.
Polybrominated diphenyl ethers, also known as PBDEs, were once commonly used in plastics, fabrics, vehicles and electronics.
Two forms of the flame retardants were taken off the market in 2004. As of January, all computers, TVs and furniture sold in Washington must be PBDE-free.
In people, the flame retardants have been linked to disruption of thyroid function and problems with nervous system development. In laboratory animals, they’ve been tied to cancer.
In Spokane, Ecology officials are testing stormwater to learn more about how PBDEs are getting into the river. The ubiquitous compounds are found in house dust, sewer sludge and treated wastewater.
“We joke that somebody in Spokane is throwing couches into the river,” Gilbert said.
Chad Furl, the primary researcher on the fish tissue project, said some of the drop in PBDE levels might be caused by seasonal fluctuations. In the 2005 study, the fish were caught in the fall, when water levels were low and the fish had more fat.
The 2009 research was done in the spring, when the fishes’ fat stores would typically be lower.
But PBDE reductions were both large and consistent across locations, Furl said.
Six fish species were collected and analyzed from a 60-mile stretch of the Spokane River between the Idaho border and Long Lake. PBDE levels were highest in fish in the Nine Mile area downstream of Spokane. They were higher in sport fish than large-scale suckers, which are osprey’s primary food source.
Only two of the osprey eggs collected from the Spokane River in 2009 had PBDE concentrations of more than 1,000 parts per billion.
At that threshold, scientists think PBDEs could cause problems for the developing embryo.