Thurston County issues toxic algae health advisory for Pattison Lake

Thurston County Public Health & Social Services (PHSS) is reporting a toxic algae bloom in Pattison Lake.

Lab results from a sample taken from Pattison Lake on 10/16/2026 detected Microcystin toxin levels at 135.0 µg/L, which is above the state recreation guideline of 8.0 µg/L.

Algae advisories are still in place for Clear Lake, Offutt Lake and Lake Lawrence.

Microcystins are a liver toxin and a possible human carcinogen. Microcystins can also cause illness in livestock and pets that drink affected water.

Staff will continue to collect weekly samples until they receive two consecutive weeks of samples with microcystin levels below state recreational guidelines.

Even if the lake is visibly clear of algae, toxins may still be present, according to PHSS.

When an algae bloom is present, health officials recommend taking extra precautions to avoid the health risks posed by potential toxins:
-Do not drink the lake water.
-Avoid contact with water containing algae.
-Avoid swimming, wading, windsurfing, and water-skiing in water bodies where algae blooms are present.
-Keep pets and livestock away from where algae blooms are present.
-Do not eat fish that come from the lake during an algae bloom.
-Avoid areas of scum when boating.

For more information about toxic algae blooms and health risks, and to see all Thurston County Algae Alerts, visit: www.thurstoncountywa.gov/algae-advisories.