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Posted on: June 17, 2019

Napa County urges caution related to seasonal algal blooms

NAPA – As the weather heats up, Napa County officials urge recreational water users to avoid close contact with bodies of water containing blue-green algae.

“While there are currently no reports of algal blooms, we want to make sure people are keeping an eye out to protect their loved ones,” said Dr. Karen Relucio, Napa County Public Health Officer. “These algae produce toxins that can cause eye irritation, skin rashes, mouth ulcers, vomiting, diarrhea, and flu-like symptoms.”

Blue-green algae are microscopic bacteria that can be found in freshwater lakes, rivers, and streams. These algal blooms appear as blue-green, white or brown foam, scum or mats that typically float on the water’s surface and collect along shorelines and boat ramp areas. Blooms are caused by slow-moving warm water and high levels of nutrients in the water. They can move, grow, or shrink depending on conditions.

Blue-green algae poisoning is most common in pets. Symptoms, including death, can be more severe in pets because they tend to drink the water from affected lakes and reservoirs. Children and adults can experience serious injury to the liver, kidney, and nervous system if affected water is swallowed. Medical treatment should be sought immediately if a person or pet is suspected to have blue-green algae poisoning.

Common recreational water purification techniques, including camping filters, tablets, and boiling, do not remove toxins from affected water.

The following guidance is recommended for people who recreate in water bodies:

  • Take care that pets and livestock do not drink the water, swim through algae scums or mats, or lick their fur after going in the water. Rinse pets in clean water to remove algae from fur.
  • Avoid wading, swimming, or jet or water skiing in water containing algae blooms, scums, or mats.
  • Do not drink, cook, or wash dishes with untreated surface water from these areas under any circumstances.
  • People should not eat shellfish or fish from these areas. If fish are consumed, remove the guts and liver, and rinse filets in clean drinking water.
  • Get medical treatment if you think that you, your children, your pet, or livestock might have been poisoned by blue-green algae toxins. Be sure to alert the medical professional to the possible contact with blue-green algae.

To report a bloom or an animal or human illness related to a bloom, contact the California State Water Resources Control Board at 916-341-5357 or email

For health-related questions, call Napa County Public Health at 707-253-4270. For assistance with reporting waters that may be affected by a harmful algal bloom, call Napa County Environmental Health at 707-253-4417.

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