The U.S. Environmental Protection Agency (EPA) announced its revisions to the national ambient air quality standards (NAAQS) for ozone in November and proposed changes were published in the Federal Register December 17. These changes were of particular interest to League members because if an area exceeds air quality limits--and is consequently designated as being in "nonattainment"--then the federal air law can reduce federal transportation funding for local governments.
NAAQS Background
The Clean Air Act (CAA) requires EPA to set NAAQS for ozone (the main component in urban smog) and five other pollutants considered harmful to public health and the environment. In addition, it requires EPA to periodically review the standards to ensure that they provide adequate health and environmental protection. The federal law also requires EPA to update those standards as necessary, a process which led to the latest proposed changes. The NAAQS are used to determine what areas are in nonattainment, meaning they do not meet federal air quality standards for ozone. Then, EPA sets nonattainment boundaries based on recommendations from the states. The designation can have important implications for growth and development because it gives EPA the authority to review proposed highway projects and long-range transportation plans.
Effect on Transportation Funding
As mentioned, attaining NAAQS affects transportation funding. In tandem with the requirement for all areas to attain the air quality standards, the CAA also contains a transportation conformity requirement for these areas. With this second requirement, the CAA promotes a goal of ensuring that federal funding and project approval decisions go to transportation activities that are consistent with the law's air quality goals. The conformity process applies to metropolitan transportation plans, transportation improvement programs (TIPs), and projects funded or approved by the Federal Highway Administration (FHWA) or the Federal Transit Administration (FTA) in areas that do not meet or previously have not met air quality standards for ozone or the five other pollutants.
As required by the CAA, the N.C. Division of Air Quality (DAQ) develops a State Implementation Plan (SIP), which describes how North Carolina will keep the air clean enough so that the state does not violate the NAAQS. In the SIP, the State estimates emissions from factories, power plants, dry cleaners, bakeries, construction equipment, lawn equipment, biogenics, vehicles and other sources. To assure that the sources do not violate the standards, the law limits how much certain sources can pollute. If the emissions for an area exceed the limits established in the SIP, then under the transportation conformity requirement, federal money cannot be spent to fund transportation projects in that area. In North Carolina, the State and municipalities share responsibilities for building and maintaining transportation infrastructure such as roads and bridges.
Ozone Standard: Current and Proposed
NAAQS include both primary and secondary standards. Primary standards set limits to protect public health, including the health of at-risk populations such as people with pre-existing heart or lung disease, children, and older adults. Secondary standards set limits to protect public welfare, including protection against visibility impairment, damage to animals, crops, vegetation, and buildings.
In the recently-noticed standard, EPA proposed creating tougher limits by reducing both the primary and secondary standard within a range of 65-70 parts per billion (ppb) over an 8-hour average. The current standard is 75 ppb.
EPA last updated ozone standards in 2008, lowering the allowable level from 80 ppb to 75 ppb measured over 8 hours. North Carolina created air quality plans for controlling ozone in nonattainment areas and achieved the desired result; DAQ staff indicated that the whole state is currently in attainment based on the 2008 standard of 75 ppb and 2012-2014 data.
However, some North Carolina counties' current ozone levels (indicated in the map below) could exceed EPA's proposed standard, depending on where the standard falls in the proposed range. For example, if EPA chose to set the ozone standard at 65 ppb, many areas of the state would be pulled into nonattainment. However, only Mecklenburg County would be considered in nonattainment if the new standard was set at 70 ppb. EPA does not plan to promulgate the actual standard until October at the earliest.

EPA projects that the vast majority of U.S. counties will meet the proposed standards by 2025 with rules and programs that are currently in place or under way. EPA will make attainment or nonattainment designations for any revised standards by October 2017. Those designations would be based on 2014-2016 air quality data, which DAQ staff indicated bodes well for North Carolina because the state's ozone levels will continually improve with the passage of time.
The 90-day comment period ends March 17, 2015, and EPA projects that the final standards will be signed by October 1.