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Press Release

Potentially Harmful Blue-Green Algae Blooms Detected in Discovery Bay

Monday, July 17, 2017

Contra Costa health officials and the Central Valley Regional Water Quality Control Board advise people and pets in the Discovery Bay community to avoid contact with local bodies of water because of blue-green algae blooms.

Contra Costa Health Services Environmental Health Division (CCEH) received results this week for several water samples taken in late June from the southwestern section of Discovery Bay. Results found elevated levels of a natural toxin produced by blue-green algae blooms.

"We are advising residents to stay out of the water and keep their pets out of the water in the southwestern portion of Discovery Bay," said CCEH Director, Dr. Marilyn C Underwood, "However, water circulates throughout the community, so the algae can also move and spread and therefore it is prudent to be cautious and to stay out of the water if you see scum or algae blooms."

Exposure to the toxin can cause rashes, skin and eye irritation, allergic reactions, gastrointestinal upset and other symptoms.

"It's important to know that dogs are especially vulnerable to getting sick from this toxin. There have been reports from past incidents of dogs dying after drinking the water or licking algae from their fur after swimming in water with blue-green algae blooms. If your pet gets ill after swimming in water with an algae bloom, take them to the vet immediately," said Christine Joab, Cyanobacteria Coordinator for the Central Valley Water Board.

For a fact sheet to help veterinarians diagnose illness related blue-green algae exposure, visit

Blooms of blue-green algae, also known as cyanobacteria, can look like green, blue-green, white or brown foam or scum floating on top of water, or suspended in the water. Warm water temperatures and nutrients contribute to blooms, but these will eventually subside under cooler conditions.

CCEH will regularly test bodies of water throughout Discovery Bay and update the community while these conditions persist.

"Anyone who had contact with blue-green algae and has now developed symptoms or believes they may have consumed contaminated water should contact their healthcare provider immediately or call California Poison Control at 1-800-222-1222," said Underwood.

No illnesses linked to Discovery Bay algae blooms have been reported in 2017. A child became sick after swimming in Discovery Bay during a similar event in 2016.Only recreational water areas are affected. Tap water in Discovery Bay is unaffected by the algal bloom.

For updates, detailed explanations of posted advisories, a map of sampling sites and other information, visit

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Press Contact
  • Victoria Balladares,
    Contra Costa Heath Services,
  • Miryam Barajas,
    Central Valley Regional Water Board,