According to the July 10 advisory, five beach locations so far have been included in the warning.
The swim areas for Mother’s Beach in Marina Del Rey and Inner Cabrillo Beach in San Pedro are listed under the advisory.
Officials have noted that the highest risk is usually within about 100 yards of storm drains, piers, and creek mouths. The warning extends 100 yards up and down the Castlerock Storm Drain at Topanga County Beach, 100 yards up and down the coast from the lagoon at Topanga Canyon Beach in Malibu, and 100 yards up and down the coast from the Santa Monica Pier.
The public health advisory comes as southern California, including much of Los Angeles County, has experienced several stretches of above-normal heat recently. The National Weather Service has issued heat advisories for large parts of the county.
High temperatures typically encourage more people to visit beaches, and warm conditions can promote bacterial growth. Elevated bacteria levels, however, are often linked to stormwater runoff, creek outflows, or sewage contamination.
The county has placed yellow warning signs at affected locations.
Swimming in water with elevated bacteria can increase the risk of gastrointestinal illness such as nausea, diarrhea, and stomach cramps. Other symptoms include ear infections, eye irritation, skin rashes, and respiratory symptoms in some cases. The risk is generally higher if water is swallowed or a person has open cuts, and for young children, older adults, and people with weakened immune systems.
A bacteria advisory typically concerns water contact, rather than simply being on the sand. Walking, sunbathing, or sitting on the beach is generally considered safe.
The county said it tests beach water regularly, and advisories are updated as new samples become available. Officials recommend checking water conditions before swimming, especially near storm drains, creeks, and runoff areas.
According to officials, warnings have been lifted for the two beach areas where recent sample results identified water quality levels within state standards: Pulga storm drain at Will Rogers State Beach and Ramirez Creek at Paradise Cove.