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Possible human health concern related to toxic algae

August 18, 2016

Health Department received illness reports from people who swam in Lake Tapps over weekend 

Health Department exploring connection between illness reports and presence of toxic algae in Lake Tapps.

TACOMA, Wash. – Posting lakes for toxic algae is common. Illness reports from people that could be linked to toxic algae is rare. After receiving about a dozen illness reports from people who swam at Lake Tapps last weekend, Tacoma-Pierce County Health Department found that toxic algae was present at the lake.

In the abundance of caution, the Health Department is urging people to stay out of the lake. People should not swim, wade, water ski, jet ski or fish at Lake Tapps, and they should keep their pets from going in the water.

“We are investigating the potential link between the toxic algae bloom and the symptoms people have reported, but there is no definitive laboratory test for toxic algae illness,” Brad Harp, Water Resources Program Manager. “We do not have any evidence that this toxic algae situation is related to the caution advisory posted at Allen Yorke Park on July 22.”

The Health Department has not found toxic algae in Lake Tapps previously.

The people who were sick reported symptoms that are consistent with ingestion of microcystin, a toxin produced by several genera of cyanobacteria, including Oscillatoria. The illnesses occurred in people ages 2 to 48 years, all of whom recovered within 48 hours.

Symptoms of microcystin ingestion through recreational water exposure is usually self-limiting gastrointestinal illness. Skin and mucous membrane irritation may also be present. In high doses, microcystin is toxic to the liver.

Swallowing lake water or prolonged skin contact with algae may result in illness such as muscle weakness, vomiting, diarrhea and/or nausea in people. Anyone who swallows water that may contain algae should contact his or her medical provider. Toxic algae can potentially be deadly for pets.

Diagnosis of microcystin intoxication is based on symptoms and a history of exposure to water with blue-green algal bloom. Supportive treatment includes replacement of fluid and electrolytes lost through vomiting and diarrhea. Severe microcystin poisoning causes hypovolemic shock, hypoglycemia, hyperkalemia, and intrahepatic hemorrhage. In extreme cases, death can occur within 24 hours of exposure.

Excessive nutrients from fertilizers, animal and human waste can run off into lakes and contribute to algae growth. Reducing use of fertilizers, properly maintaining septic systems, and properly disposing of pet waste helps improve water quality in lakes, streams, groundwater, and Puget Sound.

For more information on toxic algae, please visit our website at or call (253) 798-6470.

About Tacoma-Pierce County Health Department: Tacoma-Pierce County Health Department’s mission is to protect and improve the health of all people and places in Pierce County. As part of our mission, the Health Department tackles known and emerging health risks through policy, programs and treatment in order to protect public health. We are one of only 134 accredited health departments in the country and among five in the state to have met or exceeded the Public Health Accreditation Board’s quality standards. Learn more at

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