The Environmental Protection Agency on Thursday issued a long-awaited proposal aimed at improving how communities around the nation test for lead in drinking water and forcing quicker action when problems arise.

The overhaul comes nearly three decades after the federal government last updated its lead and copper rule — a regulation that has been criticized as complicated, poorly enforced and not tough enough when it comes to protecting Americans from a toxic metal that scientists say is unsafe at any level.

The EPA’s revamped rule, which has been in the works since 2010, is meant to provide what the agency called a “proactive and holistic approach” to more reliably identify elevated lead levels across 68,000 public water systems and to force utilities to tackle problems faster.

EPA Administrator Andrew Wheeler called the proposal “a major milestone” in a news conference Thursday afternoon in Wisconsin.

“President Trump is committed to ensuring that all Americans, regardless of their Zip code, have access to clean drinking water,” Wheeler said. “Today’s action goes a long way toward fulfilling that promise. ”

However, while Thursday’s sprawling proposal seeks significant changes to the status quo, environmental advocates said the agency’s overhaul fails to take the most important step: requiring the steady removal of the estimated 6 million or more lead service lines that remain underground throughout the nation.

“Everything else is small potatoes,” said Erik Olson, a senior director for the Natural Resources Defense Council. “From a public health standpoint, that’s absolutely critical. There are going to be problems with lead contamination as long as you leave lead pipes in the ground.”

The new proposal does appear to address some of the widely acknowledged problems with the current rule.

Local utilities will be required for the first time to test for lead in child-care facilities and schools. The EPA also said it will require utilities to create an inventory of lead service lines and to make those findings public. It also will require that all test samples be taken at homes with lead service lines, compared with only half under the current rule. When a water utility finds elevated lead levels, it now will have to notify homeowners within 24 hours.

In an effort to close loopholes that critics say have long allowed communities to avoid reporting troubling test results, the EPA also plans to strengthen existing testing protocols. The agency no longer will allow practices such as removing aerators from faucets before testing, giving residents small-necked bottles and instructions to fill them slowly or “pre-flushing” water from lines before taking samples. Each of those tactics can temporarily lower lead levels and mask potential violations.

The EPA also wants to create a new “trigger level” of 10 parts per billion of lead in the water, a standard more stringent than the existing “action level” of 15 parts per billion. If a utility detects lead exceeding 10 parts per billion in enough taps, it could be forced to reevaluate the chemicals it uses to treat the water and must work with state officials on a plan to replace outdated pipes. (Smaller systems serving fewer than 10,000 people will have more flexibility in how to respond to elevated lead levels.)

In addition, water utilities would be required to replace their portion of a lead service line anytime a resident decides to replace the lead pipe leading to his or her home. In communities that exceed the 15 parts per billion federal action level, officials would be required to replace a minimum of 3 percent of lead service lines annually.

That’s a more lenient standard than the current minimum requirement of 7 percent — and one unlikely to sit well with some public health advocates.

“That’s just staggering to me,” said Olson, noting that the amended requirement could more than double the time takes to rid a community of its lead pipes. “It’s exactly the opposite of what we should be doing. That’s exactly the wrong direction."

Asked about that change Thursday, Wheeler disagreed, saying the current rule has “offramps” that allow a utility to come back into compliance and avoid continual replacements. He argued the new rule will actually lead to steadier removal of lead pipes in troubled communities. “Once you hit that trigger, you can’t stop the replacement. It’s a permanent 3 percent per year,” he said.

Although lead exposures have fallen since Congress banned the use of lead pipes in 1986, the toxic metal remains in plumbing fixtures around the country, as well as in millions of underground pipes. Replacing all those pipes could cost as much as $80 billion, according to one EPA estimate, an expense that could fall largely on homeowners and cash-strapped cities.

The EPA was already years into revamping the much criticized lead and copper rule when the water crisis in Flint first gained national attention in 2015. The episode exposed thousands of young children in the city to alarming levels of lead, which can cause irreversible cognitive damage and other health problems, and it put a public spotlight on officials at every level who had failed to prevent the catastrophe.

“It clearly needs to be strengthened,” then-EPA Administrator Gina McCarthy said during a 2016 hearing, even as she insisted that the Flint debacle stemmed from Michigan’s failure to enforce the existing law.

Environmental activists have long argued that the federal rules are too easy to evade and too seldom enforced, and that such shortcomings have contributed to water crises in the District, Flint and, more recently, in Newark. Some state and local officials in charge of implementing the rules have called the requirements too complex and unwieldy. The water industry and individual communities have fretted over the associated costs. And residents have felt misled and lied to about the safety of the water in their taps.

“It’s a national embarrassment,” said Marc Edwards, the Virginia Tech professor who helped to spotlight the lead crisis in Flint, Mich., of the existing rule, which has remained largely untouched since 1991.

The new proposal does not set one enforceable standard for lead, known as a “maximum contaminant level.” Nor does it require that estimated 6 million lead service lines that remain underground around the country be replaced in the near term, as environmental activists had wanted.

The new rule, which will be open for comment for 60 days, also does not lower the agency’s lead “action level,” which remains more lenient than new regulations put in place by Michigan in 2018. There, lawmakers plan to reduce the threshold to 12 parts per billion and require that all lead service lines in the state be replaced by 2040, unless a utility can demonstrate that it needs longer to implement the rule.

Edwards, who has seen water crisis after water crisis erode residents’ trust in government, said none of the EPA’s proposed changes will matter unless public officials do what they haven’t always done in the past.

“Enforcement,” he said, “is everything.”