The Environmental Protection Agency proposed an overhaul of a decades-old rule on testing for lead contamination in drinking water.

The agency is touting the new guidelines as a significant step to reduce the presence of lead in the nation's drinking water supply and as evidence of the Trump administration's commitment to ensuring clean water across the U.S. But critics say the changes will actually slow down the process of removing lead from cities' water systems.

EPA Administrator Andrew Wheeler rolled out the proposed rule, which the agency says is the first "major" overhaul of the Lead and Copper Rule since 1991, during an event in Green Bay, Wis., on Thursday afternoon.

"Today, the Trump Administration is delivering on its commitment to ensure all Americans have access to clean drinking water by proposing the first major overhaul of the Lead and Copper Rule in over two decades," Wheeler said in a statement.

"By improving protocols for identifying lead, expanding sampling, and strengthening treatment requirements, our proposal would ensure that more water systems proactively take actions to prevent lead exposure, especially in schools, child care facilities, and the most at-risk communities."

Critics, though, are pushing back on the agency's claims, arguing that the changes may actually slow progress on removing lead from water.

The rule does not lower the lead action level as many public health experts had hoped. Those experts say the current level, 15 parts per billion (ppb), is too high to meaningfully reduce the blood lead levels of children who are exposed.

Instead of lowering the lead action level, the rule establishes a new two-tier system for addressing lead contamination.

When a city's water hits a new 10 ppb "trigger" level, cities would be required to reevaluate their water treatment processes and possibly add corrosion-control chemicals to city water.

The agency is touting the new trigger level of 10 ppb, saying it would "enable systems to react more quickly should they exceed the 15 ppb action level in the future."

At the heart of the issue is how to deal with the nation's estimated 6 million lead service lines that connect homes to city water supplies.

One improvement in the proposal is that cities would be required to replace a lead service line if a homeowner replaces their portion of the line.

But only at 15 ppb must cities begin to replace the full length of all of the lead service lines in their system. Under the new proposal, though, cities would be required to replace 3 percent of lead service lines each year - lower than the current requirement of 7 percent.

Critics worry easing regulations on how quickly cities must replace their pipes will ensure lead stays in the system even longer.

"It's really just like window dressing to try to make it look like they were being much more stringent when in fact the real action level stayed exactly the same, and they lowered the percent of upgrades to 3 percent from 7 percent. That's very disappointing," said Betsy Southerland, who was director of the Office of Science and Technology at the EPA's Office of Water under the Obama administration.

An EPA official told reporters the agency believes other changes in the proposal will help ensure that more pipes get replaced, including requiring cities to do a census of the lead service lines within their system and still requiring cities to replace pipes even if later testing is below the action level. Cities would be required to do the replacements for two years, rather than just one.

But Southerland said she sees the proposal largely as lip service from an administration that has repeatedly proposed cutting from the budget the assistance that funds city projects to remove lead pipes - something Congress has repeatedly quashed with bipartisan support.

High levels of lead exposure can be extremely harmful and even cause death. Lead exposure is especially worrisome for children, who can experience cognitive disorders and neurological defects when exposed at certain levels.

The Centers for Disease Control and Prevention says there's no safe level of lead in children's blood.

The new EPA rule does not account for lead in pipes in people's homes, leaving it up to individuals to voluntarily pay to replace any lead pipes in their own homes.

Worries about lead exposure from drinking water gained new attention in 2015 after the water contamination scandal in Flint, Mich.

Wheeler has previously said the Obama administration waited too long to act in Flint, where residents were drinking water with alarming levels of lead.

"Part of the problem with Flint was there was a breakdown in once they got the data, once the city of Flint, the state of Michigan, the Obama EPA - they sat on it," Wheeler told CBS in March. "We're not doing that. As soon as we get information that there's a problem, we're stepping in, we're helping the local community get that water system cleaned up."

The latest proposal seeks to address that disconnect, requiring utilities to alert residents within 24 hours if their water tests above the 15 ppb level.

It also specifically targets the effects lead can have on children by requiring water systems to conduct tests at schools and child care facilities.

Updates to those testing requirements would also bar cities from advising homeowners to flush pipes before filling up testing bottles - something that can throw off test results.

But water experts worry that overall, the trigger level is the proposal won't spur enough action from cities, favoring corrosion control in favor of expensive infrastructure replacement.

"I think it's a stop gap measure," said Carl Reeverts, who retired from the EPA in 2014 after serving as deputy director of the drinking water protection division. "Removing lead service lines is the only way to really rid the system of potential exposure to lead in drinking water."

--Updated at 4:27 p.m.