In a ruling issued Thursday, the EPA is cracking down on lead paint dust that remains in millions of homes and poses a health risk to young children.

Any level of lead paint dust in is considered hazardous, according to new requirements for identifying and cleaning up the harmful dust in certain homes and child-care facilities across the country, finalized Thursday by the US Environmental Protection Agency.

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.