Toxic Algae in Oregon

Who tracks blooms in Oregon

The Oregon Health Authority (OHA) runs the state’s recreational harmful algae bloom program. Its monitoring season runs from May to October, and in 2026 it began on May 4. OHA, the Oregon Department of Environmental Quality and trained local staff check reported blooms, and managers of public water bodies can post signs at access points.

Only a fraction of Oregon water bodies are monitored, so OHA is clear that no advisory does not mean no bloom.

Advisory, precaution and lifted

For 2026, OHA is piloting a revised advisory protocol and plans to gather feedback after the season.

The toxin values OHA uses

OHA’s 2024 advisory guidelines set these recreational use values, based on exposure for children ages 6 to 11:

The same guidelines list far lower values for dogs, for example 0.2 micrograms per liter for microcystins. OHA publishes these for information only and does not base advisories on them, which is why water under a precaution can still be dangerous for a dog.

Check before you go

• OHA current advisories lists every advisory and precaution, with a map.
• Call the OHA toll free line at (877) 290-6767.
• Look at the water. Scum, paint like streaks or green flecks are reasons to stay out even with no advisory posted. See what a bloom looks like.

How to report a bloom or illness in Oregon

• Use OHA’s online CyanoHAB reporting form for a suspected bloom. OHA has separate online forms for human illness and animal illness.
• Email hab.health@oha.oregon.gov or call the program at (971) 673-0482.

All three forms are linked from the OHA advisories page.

Keeping people and pets safe

• People: OHA’s advice is “when in doubt, stay out.” Avoid swimming and fast boating that sprays water in your face where an advisory is posted.
• Dogs: keep them out of the water and away from scum and shoreline mats under both advisories and precautions. Rinse them with clean water after any contact and call a vet if they act sick.
• Livestock: move animals to another water source while a bloom is present.
• Drinking water: if you draw water straight from a lake or river, see OHA’s guidance on private intakes and home treatment. Boiling does not remove cyanotoxins.

EPA swimming advisory values

The US Environmental Protection Agency recommends a swimming advisory whenever microcystins are above 8 micrograms per liter or cylindrospermopsin is above 15 micrograms per liter on any single day. Oregon’s values for microcystins and cylindrospermopsin match EPA’s.

You cannot tell whether a bloom is making toxins by looking at it, and toxin levels can change from one week to the next. Only a lab test can tell you what is in the water.

Private and community lakes

OHA’s monitoring centers on public recreation water. HOA lakes, resort and golf course lakes and private lakes are usually never sampled. Our algae ID and cyanotoxin analysis identifies the algae and tests for toxins, and a nutrient plan goes after what feeds the bloom.

Sources, checked November 4, 2026. Oregon Health Authority, Harmful Algae Bloom Advisories. OHA, 2026 Pilot Recreational HAB Advisory Protocol. OHA, Advisory Guidelines for Harmful Cyanobacteria Blooms in Recreational Waters (2024). US EPA, Protecting Human Health from Cyanotoxin Exposure During Recreation. US EPA, Recreational criteria and swimming advisories for microcystins and cylindrospermopsin (2019).