PORTLAND Ore. (Reuters) - A regatta fundraiser that was expected to draw hundreds of crew-rowing competitors to downtown Portland this weekend has been canceled because of the presence of toxic blue-green algae on the Willamette River, organizers said on Thursday.
"It was too risky, there are too many people out there with compromised immune systems," said Row for the Cure event co-chair Juanita Chambers.
Many of the roughly 600 athletes registered for the event, a fundraiser for the Susan G. Komen breast cancer nonprofit, are themselves cancer survivors, she said.
The Oregon Health Authority last week declared a 10-mile stretch of the Willamette, which runs through downtown Portland, as hazardous for swimming, boating or fishing after tests showed algae toxins at 50 times safe levels.
"The algae is still visible in areas, although it's certainly less intense than it was last week," agency spokesman Jonathan Modie said on Thursday.
No additional tests will be conducted until the greenish sheen can no longer be seen on the river surface, he added.
Exposure to toxic blue-green algae can cause rashes and stomach problems and is especially dangerous to dogs.
"The advisory definitely will remain in place over the weekend, so we're still encouraging people to avoid all contact with the water," Modie said.
Toxic algae blooms are an ancient phenomenon, heightened in recent years across the United States by agricultural runoff and warmer weather, said David Farrer, a toxicologist for the Oregon Public Health Division.
Most prominently, algae in Lake Erie contaminated the Toledo, Ohio, municipal water system this summer. Blue-green algae also has tainted water in several northern California waterways, including the Klamath River and adjacent reservoirs.
Algae toxins cannot be removed by treating the water or boiling it, and attempts to kill off algae blooms can instead worsen contamination, Farrer said.
In quantities below toxic levels, the cyanobacteria found in these waters are beneficial for the environment, he added.
"It's estimated that 30 percent of the oxygen on the planet comes from blue-green algae," he said.
Until last week there had never been a toxic bloom documented on Portland's major river.
The Row for the Cure Regatta was founded in Portland in 1994, and had never before been canceled, Chambers said. The races are now held in more than two dozen cities across the United States and in Europe, according to the event's website.
Reporting by Courtney Sherwood; Editing by Steve Gorman and Mohammad Zargham