It’s Air Quality Awareness Week and the Environmental Protection Agency is taking the opportunity to share some important medical advice. In a series of tweets and elsewhere online, the agency is drawing attention to the impact of air pollution on health by citing scientific studies and other material. But critics were quick to point out that some of the very studies being highlighted might not be allowed under proposed guidelines to restrict studies used in policy making. Energy Policy Institute at the University of Chicago Director Michael Greenstone comments on the EPA's change in science policy.