A report released Wednesday by the Environmental Working Group found variants of the chemicals known as PFAS in 74 community water systems between 2013 and 2019, according to data from state and federal regulators. More than 40 percent of the systems had at least one sample that exceeded the health advisory level set by the U.S. Environmental Protection Agency.
Communities served by systems with highest detections of PFAS include Corona, Camp Pendleton, Oroville, Rosemont and areas of Sacramento.
PFAS chemicals are used to make products water and stain resistant, including carpets, clothing, furniture and cookware. Two of the most well-known chemicals, PFOS and PFOA, have been phased out in the United States. But they don't break down easily and linger in the environment, earning the nickname "forever chemicals."
Studies have linked PFOS and PFOA to a variety of health problems, including cancer, immune system issues and liver and thyroid problems. But there are thousands of variants of PFAS chemicals.
"One of the biggest takeaways here is we're not just detecting just PFOA and PFOS in these systems, but it's a mixture of different PFAS chemicals," said Tasha Stoiber, a senior scientist at the Environmental Working Group.
California does not set maximum contaminant levels for PFAS chemicals or require water agencies to test for them. It does encourage water systems to test for them and offers guidelines on when they should notify the public. If agencies do test, they must report any samples that exceed the guidelines.
Earlier this year, Democratic Gov. Gavin Newsom signed a law allowing state water regulators to order more systems to monitor for PFAS chemicals and to notify the public. The law takes effect Jan. 1.
Meanwhile, the State Water Resources Control Board is developing maximum contaminant levels for PFOS and PFOA. But those are just two of the thousands of variants of PFAS chemicals. Andria Ventura, toxic program manager at the advocacy group Clean Water Action, said setting standards for only two of the chemicals "sends the wrong message to the public."
Ventura said she knows it is difficult to regulate for a class of chemicals this large, but "we need to start investigating how to do that, or how to at least get bigger chunks of these chemicals regulated."
Water systems have responded to the PFAS problem by taking wells offline, blending the contaminated water with cleaner sources and installing treatment systems.
One of the highest concentrations of PFAS chemicals was found earlier this year in a well run by the California Water Service Company in Oroville. For every trillion parts of water, the sample contained 451 parts of six PFAS chemicals. That's more than six times higher than the EPA guidelines.
Spokeswoman Yvonne Kingman said the company does not use the well to supply drinking water to its customers, but the company keeps the well online in case it needs the well for firefighters or as a backup should the main plant go offline. Kingman said the company tests for 14 types of PFAS chemicals.
"The protection of our customers' health and safety is our absolute highest priority, so we've been monitoring this for quite a while," Kingman said.
PFAS chemicals have been a problem near military bases because it is an ingredient in a foam the military uses to fight liquid fuel fires. A 2017 sample at a well in Camp Pendleton, the Marine Corps base in San Diego, contained seven PFAS chemicals for a combined 820 parts per trillion, or 11 times higher than the EPA guidelines.
Camp Pendleton officials stopped using that well after the test, spokesman Capt. David Mancilla said. The base only uses the foam for emergencies, he said.
"The drinking water at MCB Camp Pendleton is safe to drink and meets or exceeds all regulated standards," he said.
The Associated Press contributed to this story.