An estimated 535,000 young children in the United States have harmful levels of lead in their bodies, putting them at risk of lost intelligence, attention disorders and other life-long health problems, according to a new estimate released Thursday by federal health officials.

The new number shows lead poisoning affects 1 in 38 children ages 1 to 5, according to the report by the Centers for Disease Control and Prevention.

“To the extent that Americans think this is a problem of the past, clearly this is evidence there is still a problem,” said Rebecca Morley, executive director of the National Center for Healthy Housing, a non-profit lead-poisoning-prevention advocacy group.

As lead has been removed from gasoline and paint, the CDC notes that substantial progress has been made reducing the number of U.S. children with elevated levels of lead in their bodies.

Children today continue to be exposed to lead from a variety of sources. Experts say lead-contaminated house dust and soil are among the most important sources, with children ingesting lead particles when they put dust-covered hands and toys in their mouths. Many older homes contain lead-based paint, which deteriorates into a fine dust. Soil can be contaminated from paint, but also with fallout from historical factory emissions and vehicles that once burned leaded gasoline.

The CDC report notes that its latest review of lead poisoning data continues to find disparities based on race and income in the amount of lead in children’s bodies. The report said, “These disparities can be traced to differences in housing quality, environmental conditions, nutrition, and other factors designed to control or eliminate lead exposure.”