EPA extends comment period on plan to retain SO2 NAAQS

EPA is extending the public comment period from Oct. 18 to Nov. 17 on two draft documents supporting the agency review of sulfur dioxide (SO2) national ambient air quality standards (NAAQS), which recommend that the agency leave the existing one-hour SO2 standard unchanged at 75 parts per billion (ppb). The Obama EPA last revised the SO2 standard in 2010, tightening the standard to 75 ppb over a novel one-hour averaging time, replacing standards of 140 ppb over 24 hours and...