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07-23-12 What is ozone?

Question of the Week
July 23, 2012
What is “ozone”?
This summer we have experienced high ozone levels throughout Tennessee. 
Ozone is molecular oxygen, but contains three oxygen atoms per molecule (O3) as opposed to the usual O2 we breathe and routinely administer to our patients.  Ozone is typically formed at ground level usually during the summer when heat, sunlight and man-made air pollutants (nitrous oxides, NOX) are high.  Much of Tennessee, the Midwest, Mid-Atlantic States and the northeast have experienced record levels of heat, sunlight and therefore elevated levels of ozone.  Ozone is another chemical which in the right dose is toxic to humans.  Ozone is inhaled and can damage the respiratory tract leading to several adverse health effects.  Ozone is not “scrubbed” by the upper respiratory tract very efficiently because of its low water solubility.  It reaches the lower respiratory tract and damages epithelial cells resulting in inflammation, increase in reactivity and an increase in epithelial permeability.  In the general population symptoms include coughing, throat irritation, pain, burning or chest discomfort with deep breaths, chest tightness, wheezing or shortness of breath.  In patients with asthma or other chronic respiratory disease their symptoms are exacerbated and may occur sooner and more frequently.
The Air Quality Index (AQI) can be used to predict when patients may be more prone to get symptoms.  The AQI is like a snapshot of the amount of pollutants in the air that affect air quality. The higher the number, the worse the quality. Ideally, the number is less than 50.  AQI is reported in the news but can also be found at http://www.epa.gov/airnow and is frequently updated during the day.  Two basic strategies to recommend to your patients when AQI is expected to be high are to reduce the time spent outdoors, and to reduce the level or duration of outdoor activities (or both).   Planning activities early in the day or at night helps reduce exposure to ozone also.
This question prepared by: John Benitez, MD, MPH  Medical Toxicologist