Press Release: Lake Davis Update

For Immediate Release (C-26-97)
Contact: Communications Office (916) 324-9670
October 24, 1997

555 Capitol Mall, Suite 525
Sacramento, CA 95814
(916) 324-9670
FAX (916) 445-5563

SACRAMENTO--California Secretary for Environmental Protection Peter M. Rooney today issued an update of Cal/EPA efforts to address public health and environmental concerns related to the application of the pesticide rotenone to Lake Davis last week by the California Department of Fish and Game (DFG):

Safety specialists from Cal/EPA's Department of Pesticide Regulation (DPR), in consultation with the Department of Health Services (DHS), are investigating illnesses reported by Lake Davis area residents. DPR enforcement staff were on site during the application to observe the application to ensure that appropriate procedures were followed.

Preliminary air monitoring results indicate that rotenone levels after the treatment were too low to be expected to cause illness. Air samples from the Lake Davis area continue to be analyzed for various substances used in the rotenone mixture. These substances can cause temporary odor-related illness symptoms even at extremely low levels.

The Central Valley Regional Water Quality Control Board on Monday will issue a "notice of violation" against the Department of Fish and Game for violating a condition of a waste discharge requirements.

"Before the treatment began, Cal/EPA and the State Department of Health Services were working with the Resources Agency and the Department of Fish and Game to ensure that the health and safety of the Lake Davis residents were protected," said Rooney. "We continue to work with DHS and the Resources Agency to evaluate and address the public health and water quality concerns following the treatment of Lake Davis. Protection of health and safety is our primary focus."

Illness Investigation: Specialists from DPR, in consultation with the Department of Health Services, will work with the Plumas County Agricultural Commissioner to investigate reported illnesses resulting from the application to the lake. Under state law, DPR and the county agricultural commissioners investigate all reports of pesticide-related illnesses, and a well-defined procedure is in place. Physicians in the area will be interviewed, along with persons who suspect they were made ill. Results of any medical examinations will also be reviewed. DPR specialists will analyze the investigative results to determine if the illnesses reported were related to the application of the rotenone mixture to the lake.

As of October 24, DPR and the county agricultural commissioner had received 16 pesticide illness reports.

Although the rotenone levels detected should not be expected to cause illness, very low levels of odorous solvents such as naphthalene can cause temporary illness symptoms, including headache, dizziness, and eye and throat irritation.

Air Monitoring Results: DFG treated Lake Davis with Nusyn-Noxfish on October 15 and 16. Nusyn-Noxfish, used in Lake Davis to eradicate an infestation of northern pike, is formulated of rotenone (the active ingredient) and several other ingredients, primarily solvents.

The day after the application began, residents downwind of the lake began complaining of odors which they said smelled like kerosene, mothballs, or insect repellent. In response to these complaints, DFG and the Northern Sierra Air Quality Management District asked the State Air Resources Board to conduct air monitoring.

ARB began monitoring on October 18, setting up samplers at Honkers Cove, the dam gate, just below the dam at the spillway, at a bridge 100 yards downstream from the spillway, and at the nearest residence about a half-mile from the lake. Rotenone sampling was done for several days and is continuing.

Very low levels of rotenone were detected at the spillway every day between October 18 through 22. The highest detection at this site was 32 parts per trillion. ARB scientists theorize that as the water was released from the spillway, fine mist droplets were formed which contained low levels of rotenone. At all other sites, rotenone levels were significantly lower or non-detectable.

DPR toxicologists conducted a preliminary analysis of the amount of rotenone detected in the air. They determined that there was over a thousand-fold difference between the lowest level of the formulated product (Nusyn-Noxfish) that caused effects in animal studies and the amount of active ingredient rotenone detected in air sampling. It is unlikely that the levels of rotenone that people were exposed to would result in illnesses. Toxicologists at Cal/EPA's Office of Environmental Health Hazard Assessment concurred with this assessment.

The formulation used by Department of Fish and Game (DFG) included several solvents, including naphthalene, and trace levels of a manufacturing byproduct, trichloroethylene (TCE). Analysis of samples for naphthalene, which has a strong odor, are pending. Monitoring for TCE was done for five consecutive 12-hour periods from 9 a.m. October 18 to 9 p.m. October 20. TCE at 0.5 ppm was found during the first 12-hour sampling period on October 18 below the dam. The other 29 samples taken at this and other sites were negative. The Cal/OSHA workplace exposure limit for airborne TCE is 100 parts per million.

Water Quality Issues: The Central Valley Regional Water Quality Control Board on Monday will issue a "Notice of Violation" against DFG for violating a condition of the Board's waste discharge requirements. The Board had stipulated that impacts on fish from discharges of treated water from the lake were to be limited to no farther than one-half mile downstream of Lake Davis in Big Grizzly Creek. DFG biologists added potassium permanganate at the dam outflow to the creek to protect the trout inhabiting the downstream waters. DFG tests taken on October 17 using a "live well" containing hatchery fish showed that the test fish were dying beyond the one-half mile point downstream. Subsequent Regional Water Board water quality sampling to confirm the identity and concentrations of the chemicals in levels sufficient to kill the fish are still being analyzed.

The Regional Water Board has been working closely with DFG to identify and implement solutions that will keep the rotenone treatment process within the conditions specified in the waste discharge requirements. DFG has implemented these solutions and no further violations have been identified.

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