The department develops multiple plans to meet federal standards for six criteria pollutants: lead, ozone, particulate matter, carbon monoxide, nitrogen dioxide and sulfur dioxide. These plans constitute one main state implementation plan (SIP).
The EPA reviews pollutant standards every five years. Sometimes, a review results in a tightened standard. When this happens, the multi-step process to draw up a new SIP begins again. States are allowed to submit boundary designation recommendations to the EPA for consideration when establishing the final boundary designations. For most criteria pollutants, states are given one year to submit their recommendations and EPA finalizes boundary designations within two years. It's not uncommon for work on the old and new standards to overlap. The department considers input from all stakeholders when developing a SIP.
EPA has approved maintenance plans and redesignation requests that affect portions of Jackson and Jefferson counties. EPA has redesignated these two nonattainment areas to attainment for the 2010 sulfur dioxide standard. The Nonattainment Area Map provides an overview about the remaining/ current nonattainment areas in the state.