On April 14, 2020, U.S. EPA proposed to retain the current national ambient air quality standards (NAAQS) for particulate matter (PM) without revision. After reviewing the air quality criteria and primary and secondary NAAQS for fine and coarse PM, the agency concluded that there is insufficient scientific evidence to support tightening these standards. U.S. EPA Administrator Andrew Wheeler stated that he believes the current levels will be protective of public health while the agency continues to evaluate PM. U.S. EPA will accept public comment for 60 days after the proposed standards are published in the Federal Register.