Wednesday, May 02, 2007

Like Getting A Sunburn On Your Lung!

I’ve never heard anyone describe it like that, but that’s what someone from the American Lung Association said today about what ozone does to your lungs. Now that Smog Season has begun, we all need to pay attention to smog alerts and better understand what ozone is and what it does.

Ozone is created when oxides of nitrogen (NOx) and volatile organic compounds (VOCs) are heated by the sun:

Some types of man-made NOx and VOC are: car and truck exhaust, industrial emissions, power plants, gasoline vapors, and chemical solvents. But these compounds do occur naturally from lightning, biomass burning, and soil. Believe it or not, trees, plants and flowers release substantial amounts of VOCs. So the “ingredients” for ozone are ALWAYS present, but we only measure high levels of ozone when either the sun is very strong or it is very hot and the weather patterns become stagnant.

One of our earliest ever high-ozone days occurred in April 2003. April is a month when the sun angle is high. When high pressure is sitting over the south, like it does nearly every summer, the air mass doesn’t change much. So on one day, the sun will heat the NOx, and VOC and create a certain amount of ozone. The next day, under the same air mass, the ozone doesn’t break down that much. On the next day, the sun creates new ozone from car exhaust, etc. and adds that the ozone left-over from the previous day. So by the third day, you can have quite a problem. When the air mass changes, either by a cold front moving through or rain comes in and washes the NOx ,VOCs and ozone out of the air, we can catch a brief break.

Ozone isn’t our only problem when it comes to air quality. Tiny microscopic dust floating in our air can irritate our lungs and cause breathing problems as well. This dust, called particulate matter (PM) is solid matter or liquid droplets from smoke, fly ash, or condensing vapors that can be suspended in the air for long periods of time. PM results from all types of combustion, such as the incomplete burning of diesel fuel in buses, trucks and cars. PM can also come from burning wood stoves and fireplaces.

The EPA came up with a way to express the Air Quality using a color-coded scale which converts different amounts of ozone and PM into a number between 0 and 300, called the AQI (Air Quality Index). When the AQI is above 100, then a Smog Alert is in effect. Since this is mainly a problem in the summer, Atlanta’s “smog season” runs from May 1 to September 30.

So what should you do when a Smog Alert is in effect? Well, a Code Orange alert is a threat mainly to children, the elderly and people with respiratory illness, such as asthma. We call these people a “Sensitive Group”. If you fall into one of these categories, or care for a child or older person, limit the amount of time you spend outside. This is especially true during the late afternoon or early evening hours from 5 pm to 9 pm. Here is an example of the hour-by-hour readings of AQI from the first day of Smog Season 2007, May 1:

Notice at after 1800 (6pm), the blue line climbs and stays above the red line. This indicates that the AQI got above 100.

The next level of alert is Code Red and this occurs when the Air Quality climbs over 150. At this point, even people who don’t have a history of respiratory illness could be affected by the air and should limit outdoor activity. But people in the Sensitive Group category should not even go outside during Code Red.

Finally, there are times when the Air Quality is unhealthy for everyone. This rare occurrence is Code Purple, when the Air Quality rises above 200.

Each day on CBS 46 News, we will show you the air quality forecast for the next day. You can also see this by going to

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