Ozonehttp://www.Merriam-webster.com is a highly reactive form of oxygen. In the upper atmosphere, ozone forms a protective layer that shields us from the sun’s ultraviolet rays. At ground level, ozone is a harmful air pollutant and a primary constituent of urban smog. Ozone is produced when air pollutants from automobile emissions and manufacturing operations interact with sunlight. Long-term exposure to high concentrations of ozone can cause a significant reduction in lung function, inflammation of the airways, and respiratory distress. People with lung diseases are particularly vulnerable to the respiratory effects of ozone. Results from an NIEHS-funded study show that children who played three or more outdoor sports in areas with high ozone concentrations were more than three times as likely to develop asthma as children who did not engage in sports activities.