SO2 Average Values for 2014-2016 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 2014-2016.

SO2 levels in North Carolina are low, ranging from 1 percent to nearly twice the standard (183 percent). Brunswick county includes monitoring near CPI USA, an industrial facility, which accounts for the higher design value reported.  Overall values are trending lower than the previous 3-year period with the exception of Brunswick county.

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 2014 to 2016. These are 99th percentile averages.

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3-Year Average 
(99th Percentile)


23 ppb


137 ppb


6 ppb


7 ppb


5 ppb