The city’s Walter J. Sullivan Water Purification Facility in a screen capture from a Water Department video.

Cambridge will switch to getting all its drinking water from the Massachusetts Water Resources Authority system starting Tuesday because of rising levels of a worrisome group of chemicals in the city’s own water supply, the city announced Friday. Supply chain problems have also delayed installation of new filters designed to remove more of the chemicals, the announcement said.

The hazardous chemicals, called per- and polyfluoroalkyl substances, have been linked to a broad range of health effects, depending on exposure. The effects include reproductive and immune system problems, cancer, developmental impact in children and interference with hormones.

PFAS, a group of more than 1,000 chemicals, have been used widely since the 1950s in a variety of products including food packaging, firefighting foam and nonstick coatings on cookware. They break down so slowly that they are known as “forever chemicals” and are found throughout the environment. Most people have the chemicals at some level in their blood.

The U.S. Environmental Protection Agency in 2016 recommended a maximum level of 70 parts per trillion in drinking water for two of the most common PFAS chemicals, a tiny amount, but recently signaled that it will reduce that to a limit of practically zero because of recent health findings. In 2020, the Massachusetts Department of Environmental Protection set 20 parts per trillion as the limit for the combined total of six of the chemicals and has not yet responded to the federal agency’s newest advisory.

Cambridge has been measuring PFAS in its water since 2019 and decided this year to buy new water filter material – before the federal government’s move – to meet the state’s limit of 20 parts per trillion. The city’s water had met that limit except for one measurement in September that barely exceeded the maximum: 20.7 parts per trillion.

Now the city says it is measuring “increasing” levels of the chemicals in its treated drinking water and is switching to MWRA water as a precaution, for an estimated $2 million more in monthly costs. The shared water system found no or undetectable levels of the chemicals in its water for two quarters last year and as a result, the state has not required it to test for the chemicals since then. The federal government’s potential limit on the chemicals is so tiny that current laboratory methods can’t detect it.

City councillor Quinton Zondervan has long pushed for the switch to MWRA water. On Friday he said in an email: “As you know, I’ve been advocating for this for a long time, so I’m glad they’re finally doing what I’ve been asking for to protect the health and safety of our residents.”

The city’s announcement said it expected to use MWRA water until the end of this year. Zondervan said Cambridge should not return to using its own water supply even after it installs the new filters, because the filters won’t eliminate PFAS and also because city water has high chloride levels.

The city’s announcement did not mention the ongoing critical drought. The city gets its water from the Hobbs Brook Reservoir in Waltham and the Stony Brook Reservoir in Weston and Waltham. In March this year, before the drought worsened, PFAS levels at Stony Brook were 29 parts per trillion, well above the state limit, according to a presentation to the Water Board in May. The levels were 11.3 ppt at Hobbs Brook Reservoir and 19.3 ppt in Fresh Pond.

Water travels from Hobbs Brook Reservoir to Stony Brook Reservoir and is pumped to Fresh Pond, where it’s stored before treatment at the plant next to Fresh Pond. Then the treated water is pumped to an underground storage reservoir at Payson Park in Belmont. From there it’s distributed by gravity to residences and businesses in Cambridge.

Cambridge turning to the MWRA and its Quabbin Reservoir was last necessary during a 2016 drought, when the city’s water supply ran low.