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Recreational use health advisory for Lower Willamette River updated to include only Ross Island Lagoon


August 13, 2018

Advisory updated based on toxin testing results

The Oregon Health Authority updated a recreational use health advisory today for the Lower Willamette River to only include Ross Island Lagoon.

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.

Toxin test results from samples collected by the Oregon Department of Environmental Quality (DEQ) Thursday, Aug. 9, show elevated toxins in Ross Island Lagoon but not in areas outside the lagoon where the bloom is more dispersed. No toxins were detected outside the lagoon.

OHA first issued a health advisory for the Ross Island Lagoon Aug. 3 and lifted it Aug. 7 after tests showed toxin levels were below recreational advisory levels. The advisory was re-issued and expanded downstream to Cathedral Park on August 11. Today’s update restricts the area under advisory to Ross Island Lagoon.

While the bloom is visible in other areas of the river, it does not appear to be producing toxins at levels that threaten human health outside Ross Island Lagoon.

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

Because of dogs’ special sensitivity to cyanotoxins, OHA advises dog owners to keep their pets out of the water in any area with visible bloom regardless of whether an advisory is in effect.

Drinking water directly from Ross Island Lagoon at this time 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.

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 Ross Island Lagoon 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 Ross Island Lagoon 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 the Harmful Algae Blooms website and select “algae bloom advisories” or call the Oregon Public Health Division toll-free information line at 877-290-6767.

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 Media contact

Delia Hernández

OHA External Relations


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