On or after the date the Administrator promulgates the designation of an area as a nonattainment area pursuant to
section 7407(d) of this title with respect to any national ambient air quality standard (or any revised standard, including a revision of any standard in effect on
November 15, 1990), the Administrator may classify the area for the purpose of applying an attainment date pursuant to paragraph (2), and for other purposes. In determining the appropriate classification, if any, for a nonattainment area, the Administrator may consider such factors as the severity of nonattainment in such area and the availability and feasibility of the pollution control measures that the Administrator believes may be necessary to provide for attainment of such standard in such area.