The US Environmental Protection Agency moved to roll back emissions standards for power plants, the second-largest source of CO 2 emissions in the country, on Wednesday, claiming that the American power sector does not “contribute significantly” to air pollution. Those regulations mandated that coal- and gas-fired power plants reduce their emissions by 90 percent by the early 2030s, primarily by using carbon capture and storage technology. An NYU analysis published earlier this month found that if the US power sector were its own separate country, it would be the sixth-largest emitter in the world. The EPA is also targeting the Mercury and Air Toxics Standards (MATS) rule, which mandates that power plants maintain controls to reduce the amount of mercury and other toxic air pollutants emitted from their plants. Despite progress in reducing mercury emissions since the MATS rule was initially implemented, coal-fired power plants are still the largest source of mercury emissions in the US.