A new report on PCBs in the Spokane River has mixed news: Levels of the toxic compounds have decreased over the past two decades, but they still don’t meet water quality standards set by Washington state or the Spokane Tribe.

Fish tissue collected between 2003 and 2007 showed substantially lower levels of PCBs than samples taken in the 1990s, according to the Washington Department of Ecology, which released the study results Tuesday. But the reductions weren’t large enough to lift health advisories recommending against eating fish from certain parts of the river, and limiting meals of fish caught in other parts of the river.

PCBs are also known as polychlorinated biphenyls. In addition to causing cancer, PCBs have been linked to other health problems, including developmental issues in children. The manufacture of PCBs was banned in 1979, but they’re still flowing into the river from historic sources.

The study identified the city of Spokane’s storm water system as the largest contributor of PCBs to the river. Last month, the nonprofit Spokane Riverkeeper reached an agreement where the city agreed to clean up parts of the system to reduce PCB loads.

The Spokane River is receiving fewer PCBs than it did in the past, said Rob Duff, an Ecology Department manager. PCBs gradually break down in the environment, but it takes a long time.