As you guys know, the EPA is in place to make sure we minimize our impact on the environment, since this would harm our ecosystem and human health. This includes regulating the quality of our air, making sure we don't have too many pollutants which can cause health issues.
Politicians in the House of Representatives are seeking to undermine the scientific process which guide the EPA's policies, including its air quality standards. Rep. Lamar Smith, Chairman of the House Committee on Science, Space and Technology (sigh), has sponsored the Secret Science Reform Act back in February, which seeks to gain access to the raw data. The Union of Concerned Scientists have written several posts on why this is problematic, and I would highly recommend checking them out.
Basically, the bill would require all data on environmental research to be made public before the EPA can make any regulations. Keep in mind, this research has already gone through the peer-review process, where experts in the field have already validated the methods and conclusions to be sound. Also, this would include research done by various organizations, universities, industries, who would be unlikely to make this data public due to privacy or intellectual property concerns. So in reality, this bill would effectively tie the EPA's hands.
ETA: Guys, please read through the last paragraph before commenting. The main issue isn't about releasing the data (although that can be its own separate discussion). The issue is that by making it a requirement without any way for the EPA to enforce it, the EPA can't make any new rules.