The Environmental Protection Agency is proposing a major tightening of the health standard for airborne lead. Officials say lead levels in the air have dropped significantly but remain a health concern, especially for children.

The federal lead health standard has not been changed in 30 years.

The EPA on Thursday proposed requiring air concentrations of lead to be nearly cut in half from what they are today.

Lead pollution declined substantially after the toxic material was banned in gasoline. But there are still emissions from industrial sources such as smelters. EPA Deputy Administrator Marcus Peacock said he hoped to have a final rule by the end of the year.

Lead causes neurological problems and learning disabilities, especially in children, and has been linked to heart ailments.