18 July 2008
All About Ozone
Posted by Dan Satterfield
The Ozone levels soared Friday. We hit 127 on the air quality index in Huntsville. We always get calls and emails from people on days like this who are confused. Didn’t they hear that the ozone was disappearing? Wasn’t that a bad thing? Now we are saying there is too much of it! What gives??
Actually they are right, ozone is a good thing. It is also a bad thing. Here is the scoop!
Ozone is Ozone, but we have two areas of Ozone on Earth. Tropospheric Ozone and Stratospheric Ozone.
Ozone is oxygen by the way. The oxygen we breathe is two oxygen atoms bonded together. Ozone is formed when three atoms of oxygen bond.
The stratospheric ozone is good. It blocks harmful ultraviolet radiation from the sun from making it to the surface. Tropospheric Ozone is bad. It causes allergy like symptoms and is bad for your health.
The bad ozone (near the ground) is formed from exhaust gases from burning coal and oil. sunlight interacts with these pollutants and through a photochemical reaction, Ozone is produced. Some of this ozone will make it to the stratosphere eventually, and become good Ozone.
One of the greatest success stories of international cooperation is the Montreal Protocol. Scientists discovered in the 1970’s that chemicals used in air conditioners, and in aerosol cans were reaching the stratosphere and reacting chemically with the Ozone to destroy it. These CFC’s (Chlorofluorocarbons) were essentially phased out and replaced with more safe alternatives. This agreement is why you will have a tough time buying Freon these days! The Montreal Protocol has been amended a few times since 1985 to phase out other Ozone destroying chemicals as well.
Now the famous Ozone hole that develops in the Austral Spring each year over Antarctica is still there and bigger than ever, but atmospheric models now show that the Ozone hole will be mostly gone by 2065.
This is a good thing, in more ways than one! We did not appreciate it at the time, but it turns out that Ozone is a potent Greenhouse gas!
There is some significant new research coming out in August from NASA Scientist James Hansen. He apparently has evidence that Ozone, and some other pollutants have been responsible for more of the planet’s warming in the past few decades than thought.
Tropospheric Ozone is the reason we have an Air Quality Alert this weekend (July 2008) here in Huntsville.
The clean air act specifies that cities should try to keep Ozone levels below a certain standard. The current standard is 76 ppb (Parts per billion). It was just lowered from 80 ppb this year. When the air quality index is at 100, that indicates that the 8 hour average of Ozone was at 76 ppb. Friday’s number was 127, so we were well above the standard.
One last thing and perhaps most important. Politics is involved in this standard. The EPA has a Science Advisory Committee that advises the EPA on what level of Ozone is dangerous to health. The panel last year Unanimously recommended that the standard be lowered to somewhere between 60-70 ppb. The EPA lowered it 4 ppb from 80 to 76.
The EPA says an AQI number of 90 is moderate air quality. The top scientific experts say it is unhealthful. So what do I tell my viewers?? I am doing both.
The EPA is now proposing doing away with this science advisory committee. This proposal has met with some fierce criticism from the scientific community.