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Press Release

Health Officials and Regional Water Board Warn Discovery Bay Residents and Visitors of Possible Blue-Green Algae in the Water

Monday, July 25, 2016

Contra Costa County health officials and the Central Valley Regional Water Quality Control Board are advising people in Discovery Bay to avoid playing in bodies of water in the area after preliminary field tests indicated the presence of potentially harmful blue-green algae.

Exposure to blue-green algae can cause rashes, skin and eye irritation, allergic reactions, gastrointestinal upset, and other effects. At high levels, exposure can result in serious illness or death, according to the California Department of Public Health. Dogs are especially vulnerable to getting sick and there have been several reports through the years of dogs dying following exposure.

"We want people in the area to be on the lookout for water with green material floating in the water," Dr. Marilyn Underwood, the director of the Environmental Health Division of Contra Costa Health Services, the county health department. "Even if you're not sure it's blue-green algae, it's best if your family and your dogs do not to go in the water. When in doubt, stay out."

So far, no one in Discovery Bay has reported becoming ill because of the algae.

Blooms of blue-green algae, also known as cyanobacteria, can look like green, blue-green, white, or brown foam and scum floating on top of or suspended in the water.

County health officials performed the field tests in private-access areas of the man-made bay following complaints from residents. Since the field tests indicated that the water may contain cyanobacterial toxins, samples have been sent to state and federal labs to confirm the preliminary findings. Those test results are expected back in about a week, said Dr. Underwood.

If test results confirm the presence of blue-green algae, Dr. Underwood said warning signs would be posted in Discovery Bay. Dr. Underwood added that potential contamination only affects recreational water areas, not drinking water from the tap in Discovery Bay.

For more information on toxic algae blooms:

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  • Victoria Balladares,
    CCHS Communications Officer,
  • Sue McConnell,
    Central Valley Water Board Section Chief,