Reuters in Washington
guardian.co.uk, Thursday 27 December 2012 15.21 GMT
US Environmental Protection Agency chief Lisa Jackson announced on Thursday that she will be stepping down from her post after a tenure of almost four years marked by battles with Republicans who fought her proposed environmental regulations.
Under her leadership, the agency declared for the first time that carbon dioxide was a pollutant that could be regulated under the Clean Air Act, leading the EPA to develop a new regulatory regime to limit carbon emissions.
President Barack Obama thanked Jackson for her service, praising her work on mercury pollution limits, fighting climate change and helping set new fuel economy standards.
"Under her leadership, the EPA has taken sensible and important steps to protect the air we breathe and the water we drink," Obama said in a statement.