This action revises EPA's definition of VOCs in relation to preparing state implementation plans (SIPs) to attain the national ambient air quality standard for ozone. This revision adds the compounds propylene carbonate and dimethyl carbonate to the list of compounds which are excluded from the definition of VOC on the basis that these compounds make a negligible contribution to tropospheric ozone formation. This final rule is effective on February 20, 2009. POC is William L. Johnson, Office of Air Quality Planning and Standards, Air Quality Policy Division, Mail code C539-01, Research Triangle Park, NC 27711, telephone (919) 541-5245.; fax number: 919-541-0824; e-mail address: Johnson.WilliamL@epa.gov (Federal Register: January 21, 2009 [Rules and Regulations], Page 3437-3441).