WASHINGTON — Two weeks after setting a nationwide deadline for removal of lead pipes, the Biden administration is imposing strict new limits on dust from lead-based paint in older homes and child-care facilities.

A final rule announced Thursday by the Environmental Protection Agency sets limits on lead dust on floors and window sills in pre-1978 residences and child-care facilities to levels so low they cannot be detected.

Paint that contains lead was banned in 1978, but more than 30 million American homes are believed to still contain it, including nearly 4 million homes where children under the age of 6 live. Lead paint can chip off when it deteriorates or is disturbed, especially during home remodeling or renovation.

“There is no safe level of lead,” said Michal Freedhoff, EPA’s assistant administrator for chemical safety and pollution prevention. The new rule will bring the United States “closer to eradicating lead-based paint hazards from homes and child care facilities once and for all,” she said.

The EPA estimates the new rule will reduce the lead exposures of up to 1.2 million people per year, including 178,000 to 326,000 children under age 6.

Lead is a neurotoxin that can irreversibly harm brain development in children, lower IQ, cause behavioral problems and lead to lifelong health effects. It also affects other organs, including the liver and kidneys.

The new rule, which takes effect early next year, targets levels of lead dust generated by paint. Currently, 10 micrograms per square foot is considered hazardous on floors, and a concentration 10 times that high is considered hazardous on window sills. The new rule brings both of those levels down to no detectable lead.

The proposed rule also would reduce what level is allowed when a lead-abatement contractor finishes work on a property where lead has been identified as a problem. These levels would be 5 micrograms per square foot on the floor and 40 micrograms per square foot for sills.

Individuals and firms that perform abatement work must be certified and follow specific work practices. Testing is required afterward to ensure dust-lead levels are below the new standards.

Environmental justice and public health experts called the EPA rule long overdue, noting that lead poisoning disproportionately affects low-income communities and communities of color.

“We can all breathe a little easier now that the EPA has significantly lowered its dust lead standard to protect children,” said Peggy Shepard, co-founder and executive director of WE ACT for Environmental Justice, a New York-based advocacy group.

Shepard, who serves on the White House Environmental Justice Advisory Council, said public health experts have long understood there is no safe level of lead in a child’s blood, yet New York state leads the nation in cases of children with elevated blood levels. Black children in Harlem living below the poverty line are twice as likely to suffer from lead poisoning as poor white children, she said.

The U.S. government has gradually been reducing the standard for what counts as poisonous levels of lead in children’s blood, with the most recent change occurring in 2021. But the EPA rule marks an effort to take more proactive action.

“When you are relying on the blood lead level in children to indicate whether there is lead in the environment, we are basically using the children as canaries in the mine,” said Dr. Philip Landrigan, a Boston College biology professor who directs the school’s Program for Global Public Health and the Common Good.

The National Child Care Association said when the lead rule was proposed last year that it could hurt many financially struggling child-care centers — especially those in low-income neighborhoods, where the facilities tend to be older. Without appropriate federal funding, the rule could push small, local child-care centers to close, the group said.

Earlier this month, the federal Department of Housing and Urban Development announced $420 million in grants to remove lead hazards from homes, including HUD-assisted homes. Additional HUD grants will continue to be available to help with lead paint removal, the White House said.