"A little-noticed change in U.S. EPA air policy has turned a national pollution-monitoring network that has been providing data to researchers for 22 years into a regulatory tool, leaving states scrambling to figure out the implications."

"At issue are 90 air monitors in the Clean Air Status and Trends Network, or CASTNET, launched in 1991 by the landmark Clean Air Act amendments to track long-term trends in acid rain pollutants as well as rural ozone, a component of smog.

The network was the exclusive domain of scientists until 2010, when EPA's Office of Air and Radiation 'upgraded' the CASTNET monitors to allow them to be used for regulatory work -- to determine compliance with the ozone standard. So data collected by the monitors will go into EPA's 2011-2013 designations of areas that are in nonattainment for ozone and thus at risk for penalties."

Jason Plautz reports for Greenwire April 30, 2013. [2]