The proposed Mercury and Air Toxics Standards (MATS) establish emission limits for hazardous air pollutants from coal- and oil-fired power plants. Under MATS, the EPA expects to achieve a 78% reduction in mercury emissions and a 91% reduction in acid gas emissions from over 1,300 electric generating units. The rule requires continuous emissions monitoring, performance testing, and recordkeeping to demonstrate compliance. Affected sources must meet the new standards within three years of the final rule's publication.