Ozone and Your Health, North Carolina Dept. of Health and Human Services:
You might be confused when you hear that ozone can be bad, because you've probably heard a great deal about the importance of the "ozone layer" and how it protects us from the sun's harmful ultraviolet rays. This atmospheric ozone -- found 10 to 30 miles above the Earth's surface -- is good.
But, ozone at ground level is bad. Ozone is a reactive chemical. It has three oxygen atoms and that third oxygen atom is always ready to "react" with something. When that something is your airways, lungs, or eyes, it can hurt you.
How is ground level ozone created?
Three things are necessary to create ground level ozone --- volatile organic compounds (VOCs), oxides of nitrogen (NOx) and sunlight. Cars, power plants, industrial boilers, refineries, chemical plants and other sources emit VOC and NOx. Sunlight "cooks" VOC and NOx, creating ground level ozone.
Current Air Quality along the Gulf Coast, AirNow, September 3, 2010 at 2:00 p.m. EDT:
Because of the BP oil spill in the Gulf of Mexico, the EPA is monitoring air quality in the region. The maps and charts below show current ozone and fine particulate Air Quality Index values at air quality monitors located along the Gulf coast. These maps and charts will be updated hourly to show the most recent conditions.