How Ozone Pollution Affects Your Health
The effects of ozone on lung health have been studied at great length using laboratory animals, clinical subjects and human populations. Researchers have found time and time again that ozone is dangerous at levels currently experienced in the United States. In 2004 and 2005, it became clear that it can be deadly as well.
The first strong evidence arrived late in 2004, when two important studies documented that short-term exposure to ozone can shorten lives. One study looked at 95 cities across the United States over a 14-year period. That study compared the impact of ozone on death patterns during several days after the ozone measurements. Even on days when ozone levels were below the current national standard, the researchers found an increased risk of premature death associated with increased levels of ozone. They estimated that over 3,700 deaths annually could be attributed to a 10-parts-per-billion increase in ozone levels.35 Another study, published the same week, looked at 23 European cities and found similar effects on mortality from ozone exposure.36
Confirmation came in the summer of 2005. EPA commissioned three groups of researchers working independently to review all the research around deaths associated with short-term high levels of ozone. The three teams—at Harvard, Johns Hopkins and New York University—used different approaches and conducted additional research, all published in the journal Epidemiology. All three studies report a small, but substantial association between daily ozone levels and increased deaths.37 Writing a commentary on these reviews, David Bates, MD, explained how these premature deaths could occur:
“Ozone is capable of causing inflammation in the lung at lower concentrations than any other gas. Such an effect would be a hazard to anyone with heart failure and pulmonary congestion, and would worsen the function of anyone with advanced lung disease.”38
Five groups of people are especially vulnerable to the effects of breathing ozone. They are: children, senior citizens, people who work or exercise outdoors, people with pre-existing respiratory disease (i.e., asthma or COPD) and “responders” who are otherwise healthy but have an enhanced reaction to ozone.
Ozone’s effect on an individual’s health can depend on many factors, including: whether they are part of a susceptible population group, how concentrated the ozone is, how rapidly they breathe and how long they are exposed to the ozone.
Many areas in the United States produce enough ground-level ozone during the summer months to cause health problems that can be felt right away. These immediate problems are:
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shortness of breath,
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chest pain when inhaling deeply,
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wheezing and coughing, and
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increased susceptibility to respiratory infections.
Exposure to ozone increases:
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risk of premature mortality,
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pulmonary inflammation,
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the risk of asthma attacks, and
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the need for medical treatment and for hospitalization of persons with asthma.
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Two new studies published in 2005 explored ozone’s ability to reduce lung function, or the ability of the lungs to work efficiently. Each study looked at otherwise healthy groups with long exposure to ozone: outdoor postal workers in Taiwan and college freshmen who were lifelong residents of Los Angeles or the San Francisco Bay area. Both studies found that the long exposure to elevated ozone levels had decreased their lung function.40
Short-term exposure to ozone also has been linked to aggravation of chronic obstructive pulmonary disease (COPD).41 Repeated inflammation due to exposure to ozone over a period of years can lead to a chronic “stiffening” of the lungs.
Inhaling ozone may affect the heart as well as the lungs. One new study linked exposures to high ozone levels for as little as one hour to a particular type of cardiac arrhythmia that itself increases the risk of premature death and stroke.42 A French study found that exposure to elevated ozone levels for one to two days increased the risk of heart attacks for middle-aged adults without heart disease.43
