Is Ozone Harmful for Your Lungs? Even "Safe" Levels Cause Damage

Ozone (O3) is a highly reactive gas. It is composed of three oxygen atoms. Depending on where it is in the atmosphere, ozone affects us in either good or bad ways.


"Stratospheric ozone" is formed naturally. It appears when solar ultraviolet (UV) radiation interacts with molecular oxygen (O2). The stratospheric "ozone layer" extends from approximately six miles to 30 miles above Earth's surface. It helps reduce the amount of harmful UV radiation that reaches Earth's surface.
"Tropospheric" (ground-level) ozone forms primarily from reactions between two major classes of air pollutants. Those two classes of pollutants are "volatile organic compounds" (VOCs) and "nitrogen oxides" (NOx). These reactions depend on the presence of heat and sunlight. This means that more ozone forms in the summer months.
This ground-level ozone could impair lung function—even in concentrations below the current U.S. clean-air standard, according to researchers in California.

Linked to Breathing Problems

Ozone has long been linked to inflammation in the lungs and breathing problems, of course, but what is interesting about this study is that researchers found that when 31 young adults exercised at various levels of ozone exposure over several hours, some surprising results were recorded.
The participants' average lung function began to deteriorate when ozone concentrations stood at 70 parts per billion (ppb).This level is below the current U.S. National Ambient Air Quality Standard (NAAQS), which states that people should be exposed to ozone levels of no more than 75 ppb averaged over eight hours.
The research team presents their finding this way: if healthy young adults exercise outside at ozone levels of 70 ppb for several hours (taking a long hike, for instance) about half will suffer respiratory symptoms. These symptoms could include coughing or pain during deep breathing.
The researchers were quick to add that the degree of response to ozone varies greatly from one person to the next. They caution that it is important for even healthy people to be conscious of their respiratory symptoms when exercising for long periods—especially in areas where ozone levels may be elevated, even if the levels are below the current NAAQS.
The research team concluded that this is particularly important for people with asthma or other lung conditions.
The researchers did not definitively say whether the clean-air standard for ozone should be lowered. They say that the data from this study and other recent ones need to be analyzed before any recommendations can be made.8