May 9, 2023

When in doubt, stay out: Increasing temperatures create potential for toxins in water

PORTLAND, Ore.— As summer approaches, Oregon Health Authority (OHA) reminds people heading outdoors to enjoy Oregon’s lakes, rivers and reservoirs to be on the look-out for potentially toxic cyanobacteria blooms.

Cyanobacteria are beneficial bacteria found in all fresh water worldwide. The bacteria can multiply into blooms in any water body under the right conditions — warm weather, sunlight, water temperature, nutrients and water chemistry. Many blooms are harmless, but some can produce cyanotoxins that make people and animals sick.

Exposure to cyanotoxins occurs when water is swallowed while swimming, or when people breathe in water droplets during high-speed activities such as water-skiing or wakeboarding.

Symptoms of exposure to cyanotoxins include:

• Diarrhea
• Cramps
• Vomiting
• Numbness
• Dizziness and fainting

Although cyanotoxins are not absorbed through the skin, people with sensitive skin can develop a red, raised rash when wading, playing, or swimming in or around a bloom.

Children and pets are particularly sensitive to illness because of their size and activity levels. Dogs can get extremely ill and even die within minutes to hours of exposure to cyanotoxins by drinking the water, licking their fur or eating the toxins from floating mats or dried crust along the shore. Similarly, livestock and wildlife can become ill and die after drinking from waterbodies, troughs or other sources of drinking water affected by blooms and potential toxins.

Only a fraction of freshwater bodies in Oregon are monitored for cyanotoxins. For this reason, it is important for people to carefully observe any water body they choose to recreate in before taking the plunge.

OHA recommends that everyone stay out of water that looks foamy, scummy, thick like pea-green or blue-green paint, or where brownish-red mats are present. Additionally, since blooms can also wash up on the shore, avoid areas with algal mats that are either attached, floating or stranded on the shore.

Even then, looks can be deceiving. Certain blooms grow on or near the bottom of water bodies like lakes and rivers. While some of them make and release toxins into the water, they don’t change how the surface of the water looks, making them hard to see.

Communities looking for visual examples can find pictures of algae blooms in the Algae Bloom Photo Gallery or watch an explainer video on blooms at OHA’s official YouTube channel. If you are unsure, follow OHA’s guidance of “When in doubt, stay out.”

Open recreational areas where blooms are identified can still be enjoyed for activities such as camping, hiking, biking, picnicking and bird watching. By being aware of signs of a bloom and taking appropriate precautions to reduce or eliminate exposure, local communities can also enjoy water activities such as canoeing, boating and fishing, so long as speeds do not create excessive water spray, and fish are cleaned appropriately.

To learn if an advisory has been issued or lifted for a specific water body, visit the Harmful Algae Bloom website or call the Oregon Public Health Division toll-free information line at 877-290-6767.

For health information or to report an illness, contact OHA at 971-673-0440. For campground or lake information, call the local management agency.