High levels of microcystin toxin detected in Toad Lake

WHATCOM COUNTY, Wash. — According to a surface water advisory posted Friday, August 21, 2026, testing at Toad Lake detected microcystins at levels exceeding the recreational guidelines set by the US Environmental Protection Agency and the Washington State Department of Health. Microcystin is a toxin produced by blue-green algae.

The advisory states the toxins were detected in floating algae mats at the water surface. The mats form at the bottom of the lake on submerged rocks, sand, mud, or plants and break free to float to the surface. The surrounding water can remain clear when the material washes up on or near the shore.

Microcystin primarily affects the liver, according to the advisory. Symptoms include abdominal pain, nausea, vomiting, headache, diarrhea, sore throat, blistering around the mouth, and pneumonia.

The main danger to people and pets comes from eating or swallowing the algae. The advisory directs people to avoid touching, eating, or swallowing algae and to avoid areas where algae blooms or mats are present. Children should not play with or handle algae mat material.

Pet owners are advised to keep animals away from water with visible algae or algae clumps on the shore. Owners should rinse off any algae on animal fur with clean water and ensure animals do not lick algae from their fur, according to the advisory.

The toxins are naturally occurring. Nutrients in fertilizer, pet waste, agricultural runoff, and wildlife waste provide food for algae growth, according to the advisory.