EPA proposed a supplemental federal implementation plan for the Four Corners power plant on the Navajo Nation in New Mexico to reduce visibility-impairing pollution.

EPA proposed to find that Iowa's SIP is substantially inadequate to maintain the 2006 24-hour NAAQS for fine PM and proposed to finalize a time line for revision.

EPA proposed amendments and revisions to the NESHAP for primary lead smelting due to residual risk and technology reviews, a recent court decision, and a petition for rulemaking.

EPA proposed to retain the current NAAQS for carbon monoxide, except for network design requirements.

EPA proposed to update a portion of the outer continental shelf air regulations for Alaska.

SIP Proposal: Virginia (definition of VOC; see above for direct final rule)