The polygon geometry was digitised initially following descriptions set out in the Air Quality Regulations 2011 (SI 180 of 2011) and amended by the EPA on 1 January 2013 following a review.The EPA outline the areas to be included in Zone A, Zone B and Zone C. The remaining area of Ireland is classed as Zone D. The EPA uses Electoral Districts to outline the areas to be included in each Zone. The polygon geometry was taken from the Electoral Districts geometry. Each ED listed was selected and dissolved together. Zones A, B and C polygons were then used to erase sections of the Republic of Ireland polygon which then became Zone D. The name of each zone it provided in the regulations. Spatial Accuracy: The geometry is taken from three Ordnance Survey Ireland datasets, Electoral Districts, refer to the metadata for details