The Tacoma-Pierce County Health Department has lowered its use advisory for exposure to Lake Tapps waters after laboratory tests showed no detectable concentration of toxins associated with algae.

Despite the lower risk to swimmers, the health department still urges caution for people and pets.

“The Health Department has not been able to confirm the presence of toxins in the water, nor the presence of new algal blooms, so our advisory will change to a caution,” said Brad Harp, water program resources manager.

The caution advisory lets people know that because toxic algae poses a possible health concern, they should avoid areas where visible algae may be present.

“The message we have for the public is simple: if you see algae in the water, people and their pets should stay out,” said Harp. “Although the illnesses people have reported are consistent with symptoms of toxic algae exposure, we do not believe the conditions that would further threaten public health are widely present. Again, when in doubt, stay out.”

Tacoma-Pierce County Health Department continues to monitor the presence of algae in the lake and may retest early this week.

The health department has not found toxic algae in Lake Tapps previously. Various conditions influence whether toxic algae produces toxins.

The people who reported illnesses described symptoms that are consistent with ingestion of microcystin, a toxin produced by several genera of cyanobacteria, including Oscillatoria. The illnesses occurred in people ages two to 48 years. Twelve people reported illnesses from swimming over the weekend of Aug. 13-14, and two more reported illness after swimming in the lake on Aug. 16 and 17. Those who reported illness recovered within a few days.

Typical laboratory tests can’t confirm that illness in people is caused by toxic algae.

For more information on toxic algae, please visit the Tacoma-Pierce County Health Department website, www.tpchd.org/toxic-algae or call (253) 798-6470.

– Tacoma-Pierce County Health Department