The highest levels of ozone in the atmosphere are in the stratosphere, in a region also known as the ozone layer between about 10 km and 50 km above the surface (or between about 6 and 31 miles). Here it filters out photons with shorter wavelengths (less than 320 nm) of ultraviolet light, also called UV rays, (270 to 400 nm) from the Sun that would be harmful to most forms of life in large doses. These same wavelengths are also among those responsible for the production of vitamin D in humans. Ozone in the stratosphere is mostly produced from ultraviolet rays reacting with oxygen.
Low level ozone (or tropospheric ozone) is an atmospheric pollutant. It is formed by the reaction of sunlight on air containing hydrocarbons and nitrogen oxides that react to form ozone directly at the source of the pollution or many kilometers down wind. The ozone reacts directly with some hydrocarbons such as aldehydes and thus begins their removal from the air, but the products are themselves key components of smog. The atmospheric lifetime of tropospheric ozone is about 22 days; its main removal mechanisms are being deposited to the ground. There is evidence of significant reduction in agricultural yields because of increased ground-level ozone and pollution which interferes with photosynthesis and stunts overall growth of some plant species.
Down at near ground level, ozone is considered an environmental pollutant. This is why you hear pollutant advisory warnings for people with respiratory problems such as asthma when the ozone level is too high. It is now well documented, that people who live in areas where there is a chronic high ozone levels suffer from decreased lung capacity and functioning over time.
Ozone is also an indoor pollutant, which is the source of the controversy for vendors of machines of various kinds that emit ozone. The EPA has in its wisdom mandated “safe” ozone levels, the thinking being along the lines that a little bit of poison will not hurt you too much and most peoples immune systems can cope with filtering out toxins quite effectively. The American Lung Association is less ambiguous on their position and states there are no safe levels of ozone for people with compromised immune systems. For these people Ozone is an irritant to the throat, eyes and nose as well as the lungs.
Health Effects of Ozone
Ozone is a gas, so most likely you get exposed to it by inhaling it in its gaseous form. If you inhale too much of it you get sick but the level to which you can tolerate it differs widely among individuals including gender, pulmonary health, prior respiratory or allergy problems. Severe reactions to even brief exposure to ozone unfortunately include death, lung cancer and impaired lung functioning as individuals lose their ability to exhale particles which have now become “stickier”. Milder or more transient symptoms include coughing or wheezing, headaches or dizziness, vomiting or nausea, inability to concentrate, shortness or tightness of breath. The list goes on.
Protect Yourself from Ozone Exposure
We are not able to live in an “ozone free” world but at least we can take some reasonable precautions, in the same way as we now stay away from second handhand smoke.
- Stay indoors when your local weather bureau has issued an ozone alert.
- Avoid air cleaners which emit ozone.
- Do not go immediately into a hotel room after it has been ozonated.
- Put printers and laser copiers at a distance from your personal work space.
- Use a good hepa air filter in your work place.