WASHINGTON - The Trump administration Thursday proposed a rewrite of rules for dealing with lead pipes contaminating drinking water, but critics say the changes appear to give water systems decades more time to replace pipes leaching dangerous amounts of toxic lead.

Contrary to regulatory rollbacks in many other environmental areas, the administration has called dealing with lead contamination in drinking water a priority. Communities and families in Flint, Michigan, Newark, New Jersey, and elsewhere have had to grapple with high levels of lead in tap water and with regulatory failures dealing with the health threat.

Lead in drinking water has been linked to developmental delays in children and can damage the brain, red blood cells and kidneys. It is most often caused by lead service lines - pipes connecting a home to a water main - or lead fixtures in a home or school.

At a news conference in Green Bay, Wisconsin, Environmental Protection Agency Administrator Andrew Wheeler announced changes that include requiring water systems to test lead levels in water at schools and child care facilities.

But Wheeler disappointed conservation groups by declining to lower the level of lead contamination in drinking water systems that triggers cleanup action. And another change lowered the amount of lead pipe that water systems have to replace each year once the threshold is hit, cutting it from 7% a year to 3% a year.

That, according to Eric Olson at the Natural Resources Defense Council conservation group, would give water utilities about 20 more years to fully replace all the lead pipes in a contaminated system.

Wheeler said a series of other, smaller changes in the new proposals would offset that. Overall, he argued, the rule changes, if the White House ultimately adopts them, would mean leaking old lead pipes are "replaced at a much faster rate than ever before."

Betsy Southerland, a senior EPA water official under the Obama administration, said the new proposals largely miss the opportunity to boost the urgency of the country's rules, issued in 1991, for cleaning up lead in water systems. Asked her overall impression, she said, "I would say disappointing."