A color code is used to describe the concentration of ground-level ozone in the air we breathe. Green means no problem with ozone. Yellow means caution should be taken. When the code is orange, red or purple, ozone is at unhealthy levels and people should avoid outside activity.

In 2004, Wake County and the Triangle area did not comply with National Ambient Air Quality Standards. The Triangle area’s ozone levels have improved since 2002.

Much of this improvement is due to significant improvements in motor vehicle emissions, as newer cars replace older models that emitted greater concentrations of nitrogen oxides. The Air Quality Division of the NC Department of Environment and Natural Resources projects that the Triangle area will comply with National Ambient Air Quality Standards by 2007; however, future increases in population and the resultant vehicle miles traveled are projected to outweigh the positive impact of reduced emissions. If that is true, the Triangle area will likely not comply with National Ambient Air Quality Standards in the future unless adequate control measures are implemented to reduce emissions, such as reducing vehicle miles traveled through more extensive use of alternatives to the single-occupant motor vehicle. See Air Control Measures below for more information on what Wake County is doing to improve air quality.

• NC Department of Environment and Natural Resources Division of Air Quality
• Wake County Air Control Measures (.pdf)