City Seeking Additional Testing After Low Levels of Cyanotoxin Detected in Treated Water Sample

by Master


The City of Wilsonville learned yesterday afternoon, May 31, that a treated water sample recently tested for contaminants revealed trace levels of microcystin, a cyanotoxin produced by cyanobacteria, sometimes referred to as blue-green algae.

The City is rushing a sample to a laboratory in Seattle this morning for more thorough testing; results are expected on Monday.  Based on the result of the test, the City will determine if a public advisory is necessary pursuant to state and federal guidelines. The Environmental Protection Agency strongly recommends obtaining results from a confirmation sample prior to issuing a public advisory.

If necessary, the public advisory would likely apply to anyone who is under the age of six, who has a compromised immune system, who is receiving dialysis treatment, who has a pre-existing liver condition, who is pregnant or nursing, or who has other sensitivity concerns.

EPA has developed guidance with an advisory level for microcystins – one of the four cyanotoxins of greatest concern in drinking water – is 0.3 micorgrams per liter (µg/L). Wilsonville’s sample result was 0.34 µg/L, slightly over the guideline value. A drinking water advisory would only apply to the general population if the microcystins reached levels of 1.6 µg/L or higher.

Unlike other water treatment plants, Wilsonville’s state-of-the-art facility utilizies ozonation, a practice deemed very effective by the EPA for reducing potential exposure to cyanotoxins in drinking water by destroying microorganisms and degrading organic pollutants through the infusion of ozone. As a precaution to reduce cyanotoxins that may be present, the City has adjusted ozone levels.

“We’re being abundantly cautious here, and providing information that allows our community members to make an informed decision,” said City Manager Bryan Cosgrove. “We’re diligently following protocols put in place by the EPA as well as recommendations from state and local authorities, and will put out an advisory if we receive confirmation that we’re above acceptable levels.”

The water test that revealed the cyanotoxins is part of a series of previously scheduled tests administered over a four-month period in 2018 in compliance with the EPA’s Unregulated Contaminants Monitoring Rule (UCMR4). Three previous tests in this series found no cyanotoxins.

Boiling water is not an effective method of removing cyanotoxins. Cyanotoxins are not absorbed through the skin, so daily tasks like washing hands, bathing, cleaning dishes, and laundry pose no health risk.

For more information about water quality, people can visit the Oregon Health Authority’s websiteor call 2-1-1.
Source:  6.1.18 Bill Evans, City of Wilsonville Communications and Marketing Manager: 503-570-1502;

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