Detroit Lake algae alert lifted; protocol changed to curb confusion

As the Oregon Health Authority lifted a recreational use health advisory for Detroit Lake on Monday, it said it also is launching a new protocol for lifting advisories at the water body to ensure health officials and the public that a harmful algae bloom has dissipated.

Water monitoring has confirmed that the level of cyanobacterial toxins in Detroit Lake are below recreational guideline values for human exposure. OHA issued its recreational advisory for the lake–located 46 miles southeast of Salem, and spanning Linn and Marion counties–on June 13.

In ending the Detroit Lake advisory, OHA is following a new protocol that calls for lifting a recreational advisory when test results show cyanotoxin levels in water samples taken from Detroit Lake on three consecutive days are below recreational guideline levels, and that City of Salem visual assessments near sampling locations find the algae bloom has subsided.

OHA received below-guideline test results June 20, 21 and 22. The city completed its visual assessment of the lake June 24.

Current OHA guidelines require an advisory to be issued whenever cyanotoxin levels surpass the OHA recreational guideline levels, and then lifted when they drop below those levels. Typically, OHA’s Harmful Algae Bloom Surveillance Program receives cyanotoxin results for recreational water bodies on a bi-weekly basis, but since May 29, OHA has received daily samples for Detroit Lake from the City of Salem.

“The higher-than-usual sampling frequency on Detroit Lake is a reason recreational advisories have been issued and lifted so often, along with changes in toxin levels measured in the daily sampling from the lake,” said David Farrer, Ph.D., toxicologist with the Environmental Public Health Section at the OHA Public Health Division.

Fluctuating test results have made it difficult for community members to keep track of when the advisory is on and when it’s lifted. “We hope this new protocol for Detroit Lake will help reduce some of the confusion among the public about whether a recreational advisory is in place at the lake,” Farrer said.

To protect the public’s health, OHA will continue to issue recreational use advisories at any point cyanotoxin levels surpass OHA recreational guideline levels in Detroit Lake. The new protocol only affects Detroit Lake since it is the only water body currently being tested daily for cyanotoxins.

Although OHA is lifting the recreational advisory for Detroit Lake, OHA officials advise recreational visitors to always be alert to signs of cyanobacteria in all Oregon waters, because blooms can develop and disappear throughout the season. Only a fraction of lakes and waterways in Oregon are monitored for cyanobacteria by state, federal and local agencies, so people are encouraged to be their own best advocate when it comes to keeping themselves and their families safe while recreating.

Detroit Lake is upstream of the source of drinking water for some public water systems. Data provided by the City of Salem for Detroit Lake and the Santiam River has confirmed that toxins are below OHA advisory values for recreational water, and drinking water. While the recreational advisory for Detroit Lake is being lifted, the drinking water advisory for vulnerable populations for the City of Salem will remain in place, until the city is assured that toxins remain below OHA drinking water advisory values.

The drinking water advisory levels for vulnerable populations are different for recreational use than for drinking water. The amount of water people incidentally swallow while recreating (swimming, water skiing, etc.) is much lower than when people use it as a primary drinking water source. For drinking water concerns, visit the City of Salem’s drinking water advisory or the Oregon Health Authority’s Drinking Water Services website at http://healthoregon.org/dws. You can also dial 211 for information on the drinking water advisory.

People and especially small children and pets should avoid recreating in areas where the water is foamy, scummy, thick like paint, pea-green, blue-green or brownish red in color, if a thick mat of blue-green algae is visible in the water, or bright green cells are suspended in the water column. If you observe these signs in the water you are encouraged to avoid activities that cause you to swallow water or inhale droplets, such as swimming or high-speed water activities.

For recreational health information, to report human or pet illnesses due to blooms or cyanotoxins in recreational waters, contact the Oregon Health Authority at 971-673-0440. For information about recreational advisories issued or lifted for the season, contact the Oregon Public Health toll-free information line at 1-877-290-6767 or visit the Harmful Algae Blooms website at http://healthoregon.org/hab and select “Algae Bloom Advisories.”