A statistical method is developed to classify geographical regions according to the air quality standards for criteria pollutants. A geographic location is designated by the U.S. Environmental Protection Agency as an area of nonattainment when it does not meet the air quality standard for one of the criteria pollutants. A statistical model for air pollution is presented. This model is used to interpolate ground measurements of pollution levels at locations where there are no air quality monitors with the objective of determining the geographic areas of nonattainment. The approach presented here for interpolation takes into account that spatial patterns of air pollutants change with location. Estimates of probabilities of nonattainment are also provided, and they are used to classify the nonattainment areas by degree of severity. The approach is applied using available data from 513 sites throughout the eastern USA where ground-level ozone is measured hourly.