Lungs are ozone's primary target. Studies on animals show that ozone damages cells in the lung's airways, causing inflammation and swelling. It also reduces the respiratory system's ability to fight infection and remove foreign particles. Ozone may pose a particular health threat to those who already suffer from respiratory problems such as asthma, emphysema and chronic bronchitis. Ozone may also pose a health threat to the young, elderly and cardiovascular patients.
Ozone affects healthy people as well.
In 1990, the State Air Resources Board established a new health advisory level in response to mounting evidence that smog affects healthy, exercising adults at lower levels than previously believed. During a health advisory, everyone, including healthy adults and children are advised to avoid prolonged, vigorous outdoor exercise. Susceptible individuals, including those with heart or lung disease, should avoid outdoor activities until the advisory is cancelled. Currently, the federal Environmental Protection Agency is reviewing the adequacy of the federal health standard for ozone and is considering tightening it. Ozone, an invisible gas, is not emitted directly into the air, but forms when nitrogen oxides from fuel combustion and volatile organic gases from evaporated petroleum products react in the presence of sunshine.