The Environmental Protection Agency proposed a major tightening Thursday of the health standard for airborne lead, saying that current allowable concentrations do not adequately protect public health, especially children. The lead health standard has not been changed since the initial requirement was enacted 30 years ago. Since then, lead pollution has dropped substantially, largely because it was banned for use in gasoline. Lead emissions still are an air quality problem, largely from industrial sources, the agency said. "Our air isn't lead-free yet, so our efforts must continue," said EPA Deputy Administrator Marcus Peacock. The proposal, which would cut allowable airborne lead concentrations by up to 93% from today's standard, is expected to be made final by mid-September. An EPA staff report more than a year ago suggested a broad range of options, including one that would have eliminated the lead standard altogether. But the EPA, which in recent months has come under sharp criticism from health advocates for not being tough enough on mercury and smog air requirements, decided that the lead standard needed to be made tougher, not scrapped. The decision was praised by the American Academy of Pediatrics, which noted the proposal also would require additional monitoring of lead levels in urban areas and near lead sources, and emphasized the need for greater protection for children. But others said the EPA didn't go far enough since the top range of its proposed standard exceeds what a science advisory panel had recommended. "EPA is making progress ... but this standard still falls short of what's needed to protect the public," said Avinash Kar, an attorney for the Natural Resources Defense Council, an environmental advocacy group. Sen. Barbara Boxer, D-Calif., chairman of the Senate Environment and Public Works Committee, said the proposed requirement still "would leave children in harm's way." Peacock said lead emission into the air has declined by 98% since the first standard was imposed in 1978. But, he said, annually about 1,300 tons of lead continues to be released and research has shown that even low levels of exposure to children is damaging. Lead can be inhaled or ingested after it settles out of the air. Once in the body it rapidly is absorbed into the bloodstream, adversely affecting many organs, health experts say. Lead exposure affects the nervous system, results in learning disabilities, lower IQs and is most damaging to children. It also can result in heart problems, high blood pressure anemia and memory loss among adults. The EPA proposed to lower the allowable concentrations of lead in the air to a range of between 0.10 to 0.30 micrograms per cubic meter, compared to the current human health standard of 1.5 micrograms per cubic meter. That means if the air does not meet that standard it will not be considered protective of public health and states or local governments must find ways to reduce lead emissions. An EPA science advisory panel on lead in 2006 said any acceptable range should not exceed 0.20 micrograms per cubic meter.