The Environmental Protection Agency (EPA) has concluded that no further measures are needed to address air quality issues from renewable fuels, as per the Clean Air Act (CAA). This decision follows a study, known as the "anti-backsliding study," which evaluated whether the renewable fuel volumes required under the CAA would worsen air quality due to changes in vehicle emissions. After inviting public comments on the proposed determination announced in June 2020, the EPA decided that existing measures are sufficient to manage the air quality impacts. The study and details about this decision can be found on the EPA's website.
Simple Explanation
The EPA says that the way they plan to use renewable fuels won’t make the air dirtier, so they don’t need any new plans to fix it. They looked at the problem carefully and decided the current rules are good enough.