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When in Doubt, Stay Out!

Cyanobacteria (Harmful Algae) Blooms

algae bloom

The Oregon Health Authority (OHA) collects and reviews available information on cyanobacteria blooms, and informs the public through the issuing and lifting of recreational use health advisories when water sampling data warrants.

This information allows people to take protective action to avoid illness before deciding where to recreate. OHA relies on water sampling data provided by our partners. Read more about the water sampling process.

View Current Advisories FAQs


Cyanobacteria Bloom Awareness: You and Your Pet

Since most waterbodies in Oregon are not monitored, OHA staff recommend you become familiar with your surroundings and know the signs of a bloom before you take the plunge.

Don't go into water that looks foamy, scummy, thick like paint, pea-green, blue-green or brownish red. A good rule of thumb for you and your pet is: When in Doubt, Stay Out!

dogIf you believe you or your pet have been exposed to a cyanobacteria bloom, OHA staff are available to answer health related questions and to receive and document illness reports. We will also provide you with contact information for our partners who can give you the most up-to-date information about local recreation areas, water quality and sampling.

Current Cyanobacteria Bloom Advisories

Oregon region map with advisory locations

The most current information on advisories issued and lifted throughout the season.

View a map and table of current recreational use health advisories for cyanobacteria and cyanotoxins 
Sign up for email alerts

Advisory Archive


A yearly presentation of recreational use health advisories issued in Oregon since 2007.

Browse the summaries and view the data for each year

Frequently Asked Questions

FAQ brochure cover

Answers to common questions about blue-green algae blooms.

Browse the list of FAQs or download the brochure in English or Spanish

Advisory and Sampling Guidance

Guidelines covers For lake managers and others who deal with cyanobacteria blooms.

View Advisory and Sampling Guidance

Education and Outreach

harmful algae bloom

Brochures, posters, fact sheets and journal articles that cover basic information, human health, animal health, fish consumption and environmental concerns.



A list of some agencies involved in responding to cyanobacteria blooms.

Activities include: lake management, public health protection, and shellfish safety closures

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