Baltimore’s water system, which serves 1.8 million homes and businesses in the city and Baltimore County, contains measurable levels of so-called “forever chemicals” that the federal Environmental Protection Agency said last week pose health risks even at minute levels.

The chemicals known as PFAS, used in firefighting foams and in consumer products for their nonstick and stain-resistant properties, were found in the system at a concentration of 4.93 parts per trillion, according to a city Department of Public Works report.

That level is well below a previous health advisory threshold, and below PFAS concentrations recently found at dozens of other sites around Maryland.

But the EPA said last week that any measurable level of PFAS chemicals — they currently cannot be detected at levels below 4 parts per trillion, officials said — suggests water utilities should increase monitoring for the substances and explore technologies and strategies that can reduce them.

In response to that advisory, the Maryland Department of the Environment is planning to do more testing and monitoring and to issue warnings to water customers in Baltimore and elsewhere around the state where measurable levels of PFAS have been found, spokesman Mark Shaffer said. It also may advise operators of some water systems to find alternative sources of water.

City public works officials said they are waiting for guidance from the state agency on next steps.

The EPA announced last week that it was replacing a previous health advisory on PFAS suggesting that concentration below 70 parts per trillion could be considered safe. The new standard, while still not enforceable, sets PFAS health risk thresholds at concentrations near zero, suggesting that the chemicals pose health risks even at levels so low that they cannot be detected.

PFAS, short for per- and poly-fluoroalkyl substances, are a collection of thousands of compounds with chemical bonds so strong they do not degrade, or do so only very slowly, in the environment and remain in a person’s bloodstream indefinitely. They are found in everything from nonstick frying pans to stain-resistant rugs to cosmetics to firefighting foam. They are associated with health risks including cancer and low birth weight.

As more is learned about the chemicals’ prevalence and potential harms, some states have moved to better monitor them and limit their use. Several states have set their own drinking water limits to address PFAS contamination that are tougher than the federal guidance. The Maryland General Assembly passed legislation this year to ban use of PFAS in firefighting foams, paper products for food packaging, and rugs and carpets.

Emily Scarr, director of advocacy group Maryland PIRG, said the EPA advisory backs up concerns many health advocates have long been raising — that there is no “safe” level of PFAS exposure.

She said the PFAS levels reported in Baltimore’s system aren’t so high as to demand immediate action, but the widespread presence of PFAS in drinking water systems across the state and around the country suggests more needs to be done to regulate use and discharge of PFAS and related chemicals.

“I wouldn’t want to cause alarm in Baltimore City,” Scarr said. “There are other communities with much higher levels.”

The Maryland Department of the Environment began monitoring for PFAS in drinking water systems around the state in 2020 with money from an EPA grant, and released results in a pair of reports last July and in April.

In an initial phase of 129 water treatment plants serving 4.3 million Marylanders, 75% of samples had quantifiable levels of PFAS, including 21% at levels of 10 parts per trillion or greater.

Wells in Hampstead and Westminster in Carroll County had the highest levels found in the survey, about 240 parts per trillion, and removed from use.

In a smaller survey of aquifers around the state, more than half of samples contained measurable PFAS.

Shaffer said state environmental regulators are developing guidance for water systems that have detectable levels of the chemicals, including retesting of untreated water as well as testing of finished treated water. The department plans to urge any systems in which PFAS levels of at least 4 parts per trillion are confirmed to inform customers.

In the city’s annual drinking water report, which was released Thursday, the department said that “no additional actions are planned at this time” to address PFAS. The department said it expected EPA to issue federal regulations “in the near future” that would require the additional monitoring. But a department spokeswoman said the report was written before the EPA updated its PFAS advisory.

The report found no violations of any regulatory standards when it comes to the safety of Baltimore’s drinking water.

“A lot has changed throughout the Baltimore region since the arrival of the COVID-19 pandemic. However, the Baltimore City Department of Public Works’ ability to provide safe, high-quality drinking water has remained consistent,” said Jason Mitchell, the public works director, in a news release.

The detection of PFAS in the drinking water comes as the city public works department already is dealing with alarming failures at both of its wastewater treatment plants that have come to light over the past year.

State environment regulators, meanwhile, have faced criticism from EPA for not employing enough inspectors to ensure a healthy drinking water supply.

The Associated Press contributed to this article.