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Frequent Questions

This section provides information for counseling patients about ozone, asthma, and respiratory symptoms.

  1. Is ambient ozone exposure a risk factor for triggering asthma attacks in people with asthma?
  2. Should I recommend that my patients with asthma reduce their ozone exposure on days when air quality is unhealthy?
  3. How can an individual reduce his/her exposure to ozone?
  4. Should I advise my patients with asthma to alter medication usage on specific days or during longer periods when air quality is unhealthy?
  5. Are there any clinical effects of long-term exposure to ozone in healthy individuals?
  6. Should I advise my healthy patients without asthma to reduce exposure when air quality is unhealthy even if they do not experience any acute symptoms?
  7. What symptoms can short-term ozone exposure produce?
  8. How quickly should ozone-induced respiratory symptoms resolve in individuals without asthma?
  9. Where can my patients find information about the health effects of ozone exposure?
  10. How can a patient find out what times of day are typically more polluted for a given location?
  11. How can a patient find out when air quality is predicted to be unhealthy?

1. Is ambient ozone exposure a risk factor for triggering asthma attacks in people with asthma?
Yes. Respiratory symptoms consistent with worsening asthma, medication usage, and emergency room visits may be increased during or following days when ozone levels are unhealthy. As with most triggers, some individuals are more severely affected than others.

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2. Should I recommend that my patients with asthma reduce their ozone exposure on days when air quality is unhealthy?
In general, yes. People whose asthma is known to be more affected by ozone exposure will benefit the most from exposure reductions, while others may experience less benefit.

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3. How can an individual reduce his/her exposure to ozone?
Exposure can be reduced by reducing the time spent outdoors or reducing the level or duration of outdoor activity during the times of day that ozone levels tend to be highest in your area. These times of poorest air quality are typically in the afternoon and early evening for most locations, but this can vary by location.

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4. Should I advise my patients with asthma to alter medication usage on specific days or during longer periods when air quality is unhealthy?
There is no information available to specifically address this question for ozone exposure. Beta-adrenergic agonist use will likely temporarily reduce airway obstruction due to ozone exposure. However, it may also allow continued activity, which may increase overall exposure. There is one study that indicates that regular treatment of mild persistent asthmatics with an inhaled corticosteroid will reduce the level of neutrophilic inflammation following a single ozone exposure without reducing the immediate lung function or symptom effects.  Whether this will result in a reduced risk of a later asthma exacerbation has not been studied nor have the effects of a short course of inhaled steroids. 

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5. Are there any clinical effects of long-term exposure to ozone in healthy individuals?
The answer to this is not known. Daily experimental ozone exposure does affect the post-natal development of the respiratory tract in nonhuman primates. Some epidemiological studies suggest that young adults raised in areas of higher air pollution have a greater degree of airway obstruction than similar adults raised in areas of lower air pollution. Also, there is some evidence that long-term ozone exposure may increase the risk of developing new asthma, particularly in males. On the other hand, because there are many factors (genetic and environmental) that may interact to cause asthma, long-term ozone exposure alone does not appear to account for a large part of the asthma or other respiratory disease in the population living in some cities of the United States with high ozone levels.

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6. Should I advise my healthy patients without asthma to reduce exposure when air quality is unhealthy even if they do not experience any acute symptoms?
There are data suggesting that frequent exposure to ozone over many years may increase the risk of developing respiratory disease; however, these data are not conclusive. A simple approach would be to reduce exposure when it can be done with little cost or inconvenience. Whether a more vigorous approach to reducing such exposures is warranted or whether exposure reduction is unnecessary remains to be clarified.

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7. What symptoms can short-term ozone exposure produce?
Cough; pain, burning, or discomfort in the chest on taking a deep breath; and shortness of breath may be experienced during and after exposure. In addition individuals with asthma may experience symptoms of airway obstruction such as wheezing and shortness of breath.

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8. How quickly should ozone-induced respiratory symptoms resolve in individuals without asthma?
They should begin to improve immediately upon cessation or reduction of exposure and should have disappeared completely within 48 hours after the exposure ends.

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9. Where can my patients find information about the health effects of ozone exposure?
Information about the health effects of ozone may be found on the AIRNow Web site in the Publications section and the Your Health section. Copies of these publications may be ordered, free of charge, from the National Service Center for Environmental Publications (NSCEP) (http://www.epa.gov/ncepihom/) Web site.
Your publication requests can also be mailed, called or faxed directly to:
U.S. Environmental Protection Agency
National Center for Environmental Publications (NSCEP)
P.O. Box 42419
Cincinnati, OH 42419
1-800-490-9198
(513) 489-8695 (fax)
Please use the EPA Document Number, which is usually bolded or highlighted, when ordering from NSCEP.

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10. How can a patient find out what times of day are typically more polluted for a given location?
On the AIRNow Web site (http://airnow.gov), there is a clickable map of the United States. Clicking on a state will lead to contact information for the state or local air quality agency that issues air quality forecasts. These agencies will be able to provide information about local diurnal ozone patterns.

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11. How can a patient find out when air quality is predicted to be unhealthy?
Air quality forecasts can be found with weather forecasts, either in local newspapers, or on TV or the radio. Forecasts may also be found on national news media such as The Weather Channel and in USA Today. At about 4:15 PM Eastern time, next day forecasts are available on the AIRNow Web site at (http://www.airnow.gov/index.cfm?action=airnow.national_summary).

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