Health officials are warning visitors to use caution at Brownlee and Hells Canyon reservoirs after recent testing found high levels of toxin-producing cyanobacteria.
The Idaho Department of Health and Welfare issued a health advisory for the reservoirs, urging people to avoid swimming, wading or other direct contact with the water while the advisory remains in effect.
Cyanobacteria can produce harmful algal blooms that release toxins, which can make people, pets and livestock sick.
Officials said visitors should evaluate water conditions before swimming, boating or allowing pets near the water.
People should not drink or cook with water from affected reservoirs, as boiling or filtering does not remove the toxins and may increase health risks.
Health officials also recommend keeping pets and livestock away from the water.
If animals come into contact with the water, they should be rinsed with clean water immediately.
Symptoms from exposure can include skin irritation, red eyes, coughing, wheezing, stomach pain, vomiting, diarrhea, headaches, muscle weakness or dizziness.
Officials said harmful algal blooms do not always look the same and can appear as mats, foam, spilled paint or surface scum.
Some blooms may also be found below the water's surface.
