 These cases included suing to block the anti-climate change Clean Power Plan four times, challenging mercury pollution limits twice, ozone pollution limits once, fighting the Cross-State Air Pollution Rule and the Clean Water Rule, as well as fighting regulations on methane emissions.Pruitt stated at his Senate confirmation hearing in January 2017 that the EPA has an "obligation" to regulate carbon dioxide in accordance with a 2007 Supreme Court case and 2009 EPA decision establishing carbon emissions as a threat to public health.Under Pruitt, Oklahoma sued the EPA and lost on challenges to the EPA's regulatory authority over mercury and other toxins, as well as pollutants responsible for creating regional atmospheric haze.