EPA has proposed new national ambient air quality standards (NAAQS) for mercury emissions from gold mining facilities. The proposed rule would establish mercury emissions limits based on existing emissions levels at the best-performing U.S. facilities for three types of processes. For pre-treatment processes, the proposal would limit mercury emissions to 149 pounds per million tons of ore from both new and existing sources. For carbon processes, mercury emissions in existing sources would be limited to 2.6 pounds per ton of concentrate, while new sources would be limited to 0.14 pounds. For non-carbon concentrate processes, emissions from existing sources would be limited to 0.25 pounds per ton of concentrate and emissions from new sources to 0.20 pounds. EPA will accept comments on the proposed rule for 30 days after publication in the Federal Register.