Cambridge will start getting its drinking water from the MWRA this week after increasing amounts of toxic “forever chemicals” were detected in a sample taken from the city’s municipal supply earlier this month, officials said.

The city is expected to remain in the Massachusetts Water Resources Authority’s system through December after officials discovered the levels of six PFAS chemicals that were above the state limits for drinking water, according to a statement released by the city Friday night. The chemicals have been linked to cancer and other health threats.

The decision to switch to MWRA water was announced the same day the US Environmental Protection Agency moved to designate two of the man-made PFAS chemicals as hazardous substances — PFOA and PFOS. Both were detected in Cambridge water.

Cambridge’s move to MWRA water is being done out of an abundance of caution, the statement said, but the threat posed by the chemicals has impacted many communities across the state. As of early July, 84 community water systems in Massachusetts have tested above the state limit for six PFAS chemicals in drinking water.

Communities have been grappling with the health threat in drinking, including Westminster, where state officials believe PFAS entered groundwater from a composting facility and contaminated more than 200 properties. In Easton, officials last year sued makers of the chemicals for allegations that PFAS have contaminated the town’s drinking water. And in Wayland, officials have had to distribute bottled water to 1,400 households due to elevated PFAS levels in town water.

In May, Massachusetts sued a group of companies for “knowingly contaminating” drinking water and other sources with the chemicals. A state task force called for stricter rules for the chemicals in April and the phase-out of PFAS from consumer products by 2030.

In Cambridge, Owen O’Riordan, the acting city manager, said the city’s move to the MWRA “reflects our commitment” to provide safe water to residents, including pregnant or nursing women, infants, and people with compromised immune systems — all of whom are among those most impacted by increased PFAS levels.

“Massachusetts has some of the strictest PFAS standards in the country, and the Cambridge Water Department is committed to maintaining and supplying high-quality water to our community,” O’Riordan said in the statement.

PFAS, which stands for per- and polyfluoroalkyl substances, resist water, oil, heat, and grease. They have been used for decades in the manufacturing of products such as cookware, clothing, carpets, food packaging materials, firefighting foam, and cosmetics.

The chemicals don’t break down in the environment — researchers have dubbed them “forever chemicals” — and they can seep into community water supplies from sources like manufacturing facilities and septic systems, even artificial turf used on local athletic fields.

Researchers have found evidence that they are carcinogenic and that they can damage the liver; affect fetal growth, organ development, and reproduction.

They can also suppress the immune system’s ability to respond well to vaccinations, according to Wendy Heiger-Bernays, a clinical professor in the Boston University School of Public Health’s Department of Environmental Health.

“They are in our water, they’re in our air, they’re in our homes, they’re in our food, they’re in our rainwater,” Heiger-Bernays said. “And so the presence of them in drinking water is not surprising.”

State-required testing limits six PFAS chemicals to no more than a total of 20 parts per trillion in drinking water; Cambridge’s August sample showed a total of 21.6 parts per trillion, according to the city.

The city has retested the water after the state Department of Environmental Protection raised “quality control questions” Thursday night, Lee Gianetti, a city spokesman, said in an e-mail Saturday.

The Massachusetts Department of Environmental Protection did not respond to requests for comment over the weekend.

Cambridge submits monthly tests to the DEP for the six PFAS chemicals and has complied with state regulations since it began monitoring for the chemicals in August 2019, Gianetti said.

Cambridge’s municipal water comes from the Stony Brook Watershed in the Charles River Basin, located in Lexington, Lincoln, Waltham, and Weston, according to the city. The water, via a mix of tributaries, reservoirs, and pipes, reaches Fresh Pond in Cambridge, where it is pumped into the Walter J. Sullivan Water Purification Facility.

The treated drinking water is then pumped into the underground Payson Park Reservoir in Belmont, where it is available for use, according to the city.

Using the MWRA system will cost the city about $2 million monthly, and officials expect to appropriate the money from the city’s Water Fund, Gianetti said. It was too early to say whether customers will see an increase in water rates as a result, he said.

While relying on the MWRA, Cambridge will install a granular-activated carbon filter media at its purification facility on Fresh Pond Parkway. That work is expected to be completed by November.

That filter “will ensure that our PFAS levels will be reliably and consistently below the MassDEP regulatory standard in the short and long term,” Gianetti said.

The increased levels of PFAS have raised concerns among residents, including Quinton Zondervan, a Cambridge city councilor who has advocated for permanently using MWRA water because of PFAS levels in the municipal supply.

“We just don’t know what is, or is not, a safe level. And that’s a huge problem,” he said.

Heiger-Bernays has reviewed Cambridge’s reported monthly PFAS levels since January, which is available on the city website.

Two of the chemicals with the highest concentrations in Cambridge water were PFOS and PFOA, she said. In June, the EPA issued a warning that “some negative health effects” may occur with concentrations even near zero of either chemical in water.

“Yes, these concentrations should wake up the residents of Cambridge... the fact that concentrations are increasing is concerning,” Heiger-Bernays said in an e-mail. “The fact that PFOA and PFOS are the major ones is problematic — we know the most about the toxicity of these two PFAS.”

Kyla Bennett, director of science policy for Public Employees for Environmental Responsibility in New England, urged Cambridge residents to stop using the city’s water because of the reported levels of PFAS.

Bennett lives in Easton, where the town is spending more than $9 million on a treatment plant to remove the chemicals.

She said she thinks drought conditions are a contributing factor to the increase in Cambridge’s PFAS levels. The conditions helped the chemicals become concentrated in the ground, and then they are flushed by rain into water supplies.

She urged Cambridge residents to obtain PFAS filters for home water use.

“I would not drink that water. I would not use that water. I would not feed that water to my dogs,” Bennett said. “I would buy a filter immediately.”

A list of filters can be found on the nsf.org website, or by searching for “nsf pfas filter” on Google.

Judith Enck, a former EPA regional administrator and the current president of Beyond Plastics, a group working to eliminate plastic pollution, urged Cambridge residents to become “vigilant watchdogs” of the process to determine whether the city municipal water supply is safe — and locate who is responsible for the contamination.

“The city of Cambridge is going to have to work very closely with the Massachusetts DEP on finding the source,” Enck said. “If the polluters still exist, they should be the ones to pay all the costs associated with the drinking water contamination.”

John Hilliard can be reached at john.hilliard@globe.com.

Work at Boston Globe Media