LAKE COUNTY, Calif. — New testing results that have found record-high levels of cyanotoxin at sampling sites on Clear Lake prompted the Public Health officer on Wednesday night to issue a warning to those who source their water from private intakes on the lake.

“Effective immediately, people on private water systems whose tap water comes from their own private intake into the lake, in the Oaks Arm and Lower Arm of Clear Lake should not drink the water. Very high levels of cyanotoxin have been identified in these areas of the lake, and we are concerned there may be health impacts if private water systems are not effectively filtering out these toxins,” said Public Health Officer Dr. Gary Pace in a statement released shortly before 8:30 p.m. Wednesday.

Pace said more detailed information will be released on Thursday.

The brief message referred to the latest monitoring information from the Big Valley Band of Pomo Indians, which has been conducting testing at 15 sites on Clear Lake with the assistance of the Robinson Rancheria EPA Department.

Big Valley has been conducting a cyanotoxin monitoring program on Clear Lake since 2014.

On Big Valley’s Clear Lake Water Quality Facebook page, a post published shortly before Pace’s message was released noted that, for the second sampling event in a row, they were finding the “highest toxin levels we’ve ever seen on this lake.”

This latest sampling was conducted on Sept. 7. It surpassed levels found on Aug. 25 that also had been noted as record-breaking.

At a site located at Redbud Park in the lake’s Lower Arm, they reported microcystin toxin levels at 160,377.50 micrograms per liter, or µg/L, which they said is extremely high for toxins, “and our lab says it's the highest they've processed.”

Clear Lake Water Quality post continued, “This means it is recommended to stay out of the water in those high toxin areas until further notice, do not touch scum in the water or on shore, do not let pets or other animals drink or go into the water or go near the scum, do not eat fish or shellfish from this water, do not use this water for drinking or cooking.”

The statement and information posted on Big Valley Rancheria’s website explained the highest levels of Anatoxin-a — a neurotoxin cyanotoxin — on Clear Lake, 25.95 µg/L, was found at a site noted as SHADY01, which is located at Shady Acres on Cache Creek.

The latest sampling found nine sites with levels of microcystin, another toxin created by cyanobacteria, at danger levels, which are above 20 µg/L:

— RED01: Redbud Park, Clearlake; 160,377.50 µg/L.
— CLV7: Soda Bay Cove; 5,910.30 µg/L.
— CL-3: Lower Arm, interior of lake; 4,940 µg/L.
— AP01: Austin Park Beach, Clearlake; 4,857 µg/L.
— LC01: Lily Cove, Clearlake; 204 µg/L.
— SBMMEL01: Sulphur Bank Mercury Mine Superfund Site; 54.80 µg/L.
— JB: Jago Bay; 34.35 54.80 µg/L.
— CLOAKS01: Clearlake Oaks next to water treatment; 29.39 µg/L.
— SHADY01: Shady Acres (Cache Creek); 22.40 µg/L.

Four sites had levels of microcystin above the warning level of 6 µg/L:

— LA-03: Lower Arm, interior of the lake; 15.09 µg/L.
— LPTNT: First Street boat ramp, Lakeport; 13.56 µg/L.
— OA-04: Oaks Arm, interior of the lake; 8.76 µg/L.
— KP01: Keeling Park, Nice; 7.53 µg/L.

Four sites were identified with levels of microcystin denoting caution, which is above 0.8 µg/L:

— ELEM01: Elem shoreline; 5.67 µg/L.
— LUC01: Lucerne Harbor Park; 2.79 µg/L.
— BVCL6: Big Valley shoreline; 1.84 µg/L.
— BP: Buckingham Park; 1.26 µg/L.

Two sites below the caution levels, with no signage needed, were found:

— KEYS03: Clearlake Keys, west side; 0.44 µg/L.
— CL-1: Upper Arm, interior of the lake; 0.18 µg/L.

With Anatoxin-a detections of the toxin, the state recommends caution signage. Three sites came back with detects of Anatoxin-a:

— SHADY01: Shady Acres (Cache Creek).
— LPTNT: First Street boat ramp, Lakeport.
— KEYS03: Clearlake Keys, west side.