The head of the Environmental Protection Agency had wanted to set a stricter limit on the main ingredient in smog to better protect children from lung damage before the White House killed the effort.

Documents released Monday by the EPA show that administrator Lisa Jackson proposed lowering the ground-level ozone allowed in the air from 75 parts per billion to 70. The change was initiated in 2009 to revise a level set by the Bush administration that contradicted the agency's scientific advisers.

Last month, the White House tabled the revision until 2013. Republicans had said the $19 billion to $90 billion price tag would hurt the economy.

The agency argued that a stronger limit was needed to comply with the law and protect children.