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Health officials: Be wary of harmful algal blooms

by KAYE THORNBRUGH
Staff Writer | June 28, 2025 1:00 AM

COEUR d’ALENE — Because summer is peak season for harmful algal blooms, public health authorities are reminding Idahoans to stay safe and protect their pets when recreating around water.

Cyanobacteria are naturally occurring aquatic organisms. However, under certain conditions, the bacteria can produce toxins that affect human health and the environment. 

Humans and animals can be exposed to cyanotoxins by swimming in or swallowing water impacted by a bloom or consuming fish caught in affected bodies of water. Swallowing water impacted by a bloom can cause stomach pain, nausea and vomiting. Direct skin contact may also cause skin and eye irritation. 

Pets, livestock and wildlife are especially prone to cyanobacteria exposure because they are more likely to swim in or drink affected water. 

Harmful algal blooms, also called HABs, can vary in appearance but can often look like pea soup, grass clippings, spilled paints, mats, green or blue-green foam or dense surface scum, according to the Idaho Department of Environmental Quality. Some blooms may produce a foul odor. 

No HABs have been reported in North Idaho so far this season, according to Panhandle Health District, but as the weather gets hotter, the likelihood of a HAB occurring increases. 

Last summer, in early August, state officials issued public health advisories for Fernan, Avondale and the north arm of Hayden Lake due to the presence of cyanobacteria, also known as a harmful algal bloom.

Katherine Hoyer, public information officer for Panhandle Health District, said PHD partners with the Idaho Department of Environmental Quality and relies on community members to report suspected harmful algal blooms. 

“It’s really the only way that DEQ is able to monitor more of the bodies in North Idaho,” she said. “Their office is not able to patrol water bodies at all times, so we really depend on the public to be our eyes.” 

Community members should avoid water that smells bad, looks discolored or has foam, scum, mats or paint-like streaks on the surface and report it to their regional DEQ office. 

“If it looks funky, stay out,” Hoyer said. 

After DEQ receives a complaint of a possible harmful algal bloom, staff will test the water. Panhandle Health District will issue an alert to the public if a HAB is confirmed. 

Hoyer said pet owners should be mindful of possible HABs. Dogs that swim in affected water often lick their fur after, increasing their exposure to cyanobacteria. 

“That can actually be really bad for a pet,” she said.