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OHA Files Temporary Rules for Cyanotoxin Testing by Water Suppliers

June 29, 2018

PORTLAND, Ore.—The Oregon Health Authority has issued temporary rules requiring drinking water suppliers meeting certain criteria to test their water for toxins from cyanobacteria responsible for harmful algal blooms.

The rules, which take effect Sunday, July 1, also require water suppliers in Oregon to issue a “do-not-drink” advisory if routine and confirmation water samples test above any health advisory level, including those for either vulnerable or general populations. The temporary rules apply to the two cyanotoxins for which the U.S. Environmental Protection Agency has established health advisory levels—microcystins and cylindrospermopsin.

The maximum allowable level of total microcystins in treated water is 0.3 parts per billion (ppb) for vulnerable people and 1.6 ppb for those 6 and older and healthy adults. The maximum allowable level of cylindrospermopsin is 0.7 ppb for vulnerable populations and 3 ppb for those 6 and older and healthy adults. Vulnerable populations include children 5 and younger, the elderly, medically fragile individuals, and pregnant and nursing women.

The rules will remain in place through Dec. 27, 2018. In the meantime, OHA will establish a rules advisory committee to begin developing permanent cyanotoxin testing rules for drinking water through a public process during the fall.

OHA is partnering with the Oregon Department of Environmental Quality to develop a plan for coordinating, receiving and analyzing water samples for cyanotoxins at DEQ’s environmental laboratory in Hillsboro at no cost to water suppliers subject to the rules. For communities that request support, DEQ is prepared to provide testing and analysis of water bodies.

“As harmful algal blooms become the norm in Oregon, as they are around the country, we must address this emerging threat to our drinking water supplies,” said OHA Director Patrick Allen. “These temporary rules close a gap in regulations and will help us protect our drinking water systems so everyone in Oregon is kept safe from exposure to cyanotoxins.”

“DEQ is committed to helping Oregon communities address harmful algal blooms by providing monitoring and analytical expertise,” said DEQ Director Richard Whitman. “The impacts of climate change will continue to exacerbate conditions that lead to algal blooms and having better data will help us understand the threat posed to our water systems and how we can reduce harm.”

And though not required in the temporary rules, OHA also is encouraging water suppliers to notify the public within 24 hours if routine and confirmation samples detect cyanotoxins in treated drinking water, even if the toxins are below health advisory levels.

The rules apply to water suppliers that meet any of the following criteria:

  • Use a surface water source that has had harmful algal blooms or cyanotoxin detections.
  • Use a surface water source downstream from a water body with past harmful algal blooms or cyanotoxin detections.
  • Use a surface water source determined to be susceptible to cyanotoxins based on water quality characteristics that can promote growth of algae, such as the presence of algae and aquatic weeds and water chemistry that includes high levels of chlorophyll-a, phosphorus and pH, and low dissolved oxygen levels.
  • Purchase and supply water from any of these water systems.

OHA Drinking Water Services estimates the new rules affect between 150 and 200 water suppliers with surface water sources and water systems that purchase water from these suppliers. These systems will be required to collect raw water samples every two weeks—beginning July 15 under the temporary rules—each year between May 1 and Oct. 31, which is when cyanobacteria are most common in surface water sources.

If cyanotoxins are detected in raw water in the water source at or above 0.3 ppb for either microcystin or cylindrospermopsin, the water supplier must sample raw and treated water weekly. If cyanotoxins are detected at any level in treated water, daily sampling must occur. Treated water monitoring can return to weekly after two consecutive “non-detects” of cyanotoxins at the entry point for the distribution system.

If treated water results are above any advisory level, the water system must collect a confirmation sample as soon as practical within 24 hours. A do-not-drink advisory must be issued if cyanotoxins are still found above the health advisory level in the confirmation sample of treated water. Water systems that purchase water from a water supplier with a surface water source must collect water samples daily from their distribution systems when a cyanotoxin is found above a health advisory level in the seller’s treated water.

The temporary rules can be found at

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Contact Info:
Media contacts:
Jonathan Modie, OHA, 971-246-9139, [email protected]
Donnie Oliveira, DEQ, 971-275-3709, [email protected]