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Start Over You searched for: Year 1990 Remove constraint Year: 1990 Resource Type Polygon data Remove constraint Resource Type: Polygon data Subject Air quality—Standards Remove constraint Subject: Air quality—Standards

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1990. United States. Bureau of Transportation Statistics and Stackhouse, Cecil. This polygon shapefile depicts nonattainment and maintenance areas for the United States and its Territories for the enforcement of the ozone (O3)1... United States. Bureau of Transportation Statistics.
1990. United States. Bureau of Transportation Statistics and Stackhouse, Cecil. This polygon shapefile depicts nonattainment and maintenance areas for the United States and its Territories for the enforcement of the particulate... United States. Bureau of Transportation Statistics.