Recreational use health advisory reissued for Ross Island Lagoon, extended to Cathedral Park

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Advisory reissued based on visible scum found in Multnomah County water body
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in effect as of Friday, August 10, 2018

More information from Oregon Health Authority


Delia Hernandez,

Advisory reissued based on visible scum found in Multnomah County water body

The Oregon Health Authority reissued a recreational use health advisory today for Ross Island Lagoon and urges caution in areas of the Willamette River downstream from the lagoon, including downtown north to Cathedral Park.

Ross Island Lagoon is located about a mile south of downtown Portland in Multnomah County. The area of concern includes the downtown reach of the Willamette River.

Oregon Department of Environmental Quality (DEQ) staff collected samples for toxin analysis and results are expected next week. Because the bloom has changed and spread so much since last week, OHA is issuing this advisory as a precautionary measure until sample results are available next week.

OHA first issued a health advisory for the Ross Island Lagoon on Aug. 3 and lifted it Aug. 7 after tests showed toxin levels were below recreational advisory levels.

DEQ also carried out a visual assessment of the river and reported cyanobacteria starting at 100 meters south of Ross Island lagoon. Inside the lagoon, the bloom is thick with scums, blobs and streaking throughout. Dense cyanobacteria continued down the East channel into the mainstem of the Lower Willamette and was present at River Place marina, the swimming dock south of the Hawthorne Bridge and Tom McCall waterfront park. The bloom was visible throughout the Portland reach and on the surface at the Riverscape dock. The bloom intensified to the railroad bridge downstream of Portland Harbor. At Cathedral Park, the bloom was present but less intense.

If present, toxins are usually highest in areas where the bloom is visible, and people can avoid most of the health risks associated with blooms by avoiding those areas. However, it’s possible cyanotoxins can still exist in clear water. Sometimes, cyanobacteria can move into another area, making water that once looked foamy, scummy or discolored now look clear. Dying blooms can also release toxins that may reach into the clear water around them.

People should avoid swimming and high-speed water activities, such as water skiing or power boating, in areas where blooms are identified. Although toxins are not absorbed through the skin, people who have skin sensitivities may experience a puffy red rash at the affected area.

Drinking water directly from affected areas of the river is especially dangerous. OHA public health officials advise recreational visitors that toxins cannot be removed by boiling, filtering or treating water with camping-style filters.

People who draw in-home water directly from the affected area are advised to use an alternate water source because private treatment systems are not proven effective for removing algae toxins. However, public drinking water systems can reduce algae toxins through proper filtration and disinfection. This portion of the Willamette River is not a source of drinking water for a public water system, but if people connected to public water systems have questions about treatment and testing, they should contact their water supplier.

OHA public health officials recommend that those who choose to eat fish from waters where cyanobacteria blooms are present remove all fat, skin and organs before cooking, as cyanotoxins are more likely to collect in these tissues. Fillets should also be rinsed with clean water. Public health officials also advise people to not eat freshwater clams or mussels from the Lower Willamette River and that Oregon Department of Fish and Wildlife regulations do not allow the harvest of these shellfish from freshwater sources. Crayfish muscle can be eaten, but internal organs and liquid fat should be discarded.

Exposure to toxins can produce a variety of symptoms including numbness, tingling and dizziness that can lead to difficulty breathing or heart problems and require immediate medical attention. Symptoms of skin irritation, weakness, diarrhea, nausea, cramps and fainting should also receive medical attention if they persist or worsen. Children and pets are at increased risk for exposure because of their size and level of activity. People who bring their pets to the Lower Willamette River for recreation activities should take special precautions to keep them from drinking from or swimming in the river.

With proper precautions to avoid activities during which water can be ingested or inhaled, people are encouraged to visit the Lower Willamette River and enjoy activities such as canoeing, fishing, hiking, biking, picnicking, and bird watching. Boating is safe as long as speeds do not create excessive water spray. Although inhalation risk is much lower than ingestion, it can present a risk.

For health information or to report an illness, contact the Oregon Health Authority (OHA) at 971-673-0440.

OHA maintains an updated list of all health advisories on its website. To learn if an advisory has been issued or lifted for a specific water body, visit and select “algae bloom advisories,” or call the Oregon Public Health Division toll-free information line at 877-290-6767.

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