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Baseline Year for the Baseline Year Test (in 40 CFR 93.119)

Certain nonattainment areas are required to use one or both of the interim emissions tests before they have adequate or approved motor vehicle emissions budgets for the relevant national ambient air quality standard (NAAQS). Please consult 40 CFR 93.109 to determine the test(s) applicable to your area.

One of the interim emissions tests is the baseline year test, where projected on-road mobile source emissions are compared to on-road mobile source emissions in the baseline year. The following table indicates what baseline year must be used for comparison for each relevant NAAQS. Please refer to 40 CFR 93.119 for additional details about the baseline year test.

If you are determining conformity for the: Then the baseline year is: According to:
2015 Ozone NAAQS
  • Annual NAAQS of 0.070 ppm
2017 40 CFR 93.119(e)(4)
2012 PM2.5 NAAQS
  • Annual NAAQS of 12.0 µg/m3
2014 40 CFR 93.119(e)(4)
2008 Ozone NAAQS
  • 8-hour NAAQS 0.075 ppm
2011 40 CFR 93.119(e)(4)
2006 PM2.5 NAAQS
  • 24-hour NAAQS of 35 µg/m3
2008 40 CFR 93.119(e)(4)
1997 PM2.5 NAAQS
  • annual NAAQS of 15.0 µg/m3
  • 24-hour NAAQS of 65 µg/m3
2002 40 CFR 93.119(e)(3)
1997 8-hour ozone NAAQS
  • 0.08 ppm, avg. over an 8-hour period
2002 40 CFR 93.119(e)(3)
  • 24-hour NAAQS of 150 µg/m3
1990 40 CFR 93.119(e)(2)

For additional information about NAAQS, please refer to EPA’s NAAQS website at:

For information about areas designated nonattainment for each NAAQS, refer to EPA’s “Green Book” on the web at: