SO2 Average Values for 2013-2015 in NC Counties

In 2010, EPA revised the sulfur dioxide (SO2) standard to a 1-hour standard at a level of 75 parts per billion (ppb). To determine if the standard is met, a continuous 3-year average concentration is calculated from daily measurements and compared to the requirements of the standard.

The table below shows the 3-year average SO2 concentrations for the 5 highest reported values by county for 2013-2015.

SO2 levels in North Carolina are low, ranging from 2.7 percent to 42.7 percent of the standard. These values are higher than the previous 3-year period.

Additionally, for many years, SO2 has been measured at several sites across the state on a rotating basis. This monitoring is conducted at five sites operated for 12 months every 3 years.   For these sites we do not have continuous 3-year averages.  The overall monitoring conducted at those sites show no exceedances of the standard.

A map of North Carolina design values in counties with sulfur dioxide monitors from 2013 to 2015. These are the 99th percentile averages.


3-Year Average 
(99th Percentile)


23 ppb


9 ppb


10 ppb

New Hanover

32 ppb


14 ppb


9 ppb