2015 Ozone NAAQS

What are the new ozone NAAQS?

On November 26, 2014, the US Environmental Protection Agency (EPA) completed the federally mandated 5-year review of the national ambient air quality standard (NAAQS) for ozone and proposed a revised ground-level ozone standard range of 0.065-0.070 parts per million (ppm). The binding Final Rule was signed on October 1, 2015. The Final Rule sets 0.070 ppm (70 ppb) for both primary and secondary standards. For more information on the new ozone NAAQS see the EPA's webpage: http://www.epa.gov/ozone-pollution.

What are current ozone levels for South Carolina?

The design value, or DV, is the metric that the EPA uses to determine if an area meets the NAAQS. In the case of ozone, the DV is defined as the three year average of the annual 4th highest daily maximum 8 hour average ozone concentration at each monitor in an area. The highest DV for an area is compared with the NAAQS. If the highest DV is higher than the NAAQS, then the area could be designated as "nonattainment."

Most South Carolina monitors have shown a continuous improvement since 2008. Please note that this chart is in parts per billion (ppb). 70 ppb = 0.070 ppm.


DHEC's most current design values (2015) are shown in the map below.

How will attainment with the ozone NAAQS be determined?


The next step is for DHEC to report to the Governor's Office on ozone Design Values (DV) and possible nonattainment boundaries (if any), based on 2013-2015 ozone season data.  In turn, the Governor's Office makes recommendations to the EPA, due by October 1, 2016.  If the EPA disagrees with any of the Governor's recommendations, a "120-day letter" follows.  This gives the state a 120-day window to produce new information to support the Governor's recommendation, prior to the EPA's final decision on the designation.  There is also a 30-day public comment period.  The final designation is due no later than October 1, 2017, and will likely be based on the 2014-2016 DV.

South Carolina's ozone attainment recommendation

On September 30, 2016, the state made a recommendation to the EPA that all areas of South Carolina be designated attainment. This recommendation was based on 2013-2015 ozone monitoring results in accordance with the Clean Air Act. Two monitors, N. Spartanburg Fire Station #2 and Ashton, did not meet the 90% data completeness criterion in 40 CFR part 50 Appendix U over the 3-year period. DHEC also submitted a demonstration to show that on the missing days no conditions existed conducive to ozone concentrations above the 2015 NAAQS. The complete package submitted to EPA is here.

How could a nonattainment designation affect a particular area?

If an area is found to be nonattainment, certain additional provisions of the Clean Air Act apply. For more information on nonattainment, see DHEC's brochure on nonattainment areas.

What can I do?

DHEC has helped establish local air quality coalitions, which promote local action.

For more information on what you can do, visit our How to Help Reduce Ozone page.