By Dan Thesman on Friday, August 28th, 2026 in Columbia Basin News Columbia Basin Top Stories
BURBANK — Health officials have issued a public warning for the McNary Wildlife Refuge after recent water tests revealed elevated levels of toxic blue-green algae.
Water samples collected Tuesday from the west side of Lake Road near the refuge’s visitor center showed microcystin concentrations measuring 101 micrograms per liter, significantly exceeding Washington state recreation safety guidelines, according to the Walla Walla County Department of Community Health.
Microcystin is a potent liver toxin produced by cyanobacteria. Exposure through ingestion, inhalation, or skin contact can trigger serious illness in humans — particularly children — and can cause death in pets and livestock.
While the advisory remains in effect, officials recommend visitors avoid swimming, water skiing, or drinking the water. Boaters are advised to steer clear of algae scum, and anglers should thoroughly clean caught fish and discard the guts. Livestock and pets must be kept away from the shoreline.
Officials urge visitors to heed posted signs. A yellow “WARNING” sign signals that toxic algae is present and the water is unsafe. A red “DANGER” sign indicates extremely high toxin concentrations, meaning the body of water is completely closed to swimming, wading, fishing, or boating.
Anyone exposed to the water should rinse immediately with fresh water. Symptoms of exposure include weakness, lack of coordination, vomiting, diarrhea, rashes, and headaches. People or pets showing symptoms should seek immediate medical or veterinary care.
County health officials will continue routine testing and update advisory signs as conditions evolve.
File photo of 2022 warning regarding toxic algae bloom at McNary Wildlife Refuge