Outdoor Asthma Triggers

The EPA estimates that the chance that a child with asthma will have an attack on a high outdoor pollution day is 40% greater. In addition, a recent study that looked at the correlation between ozone levels and asthma found that time spent playing outside was associated with a higher rate of asthma in communities with high ozone pollution. Other outdoor asthma triggers include:

  • fine particulates (soot)
  • ground level ozone (smog)
  • diesel exhaust
  • sulfur dioxide, nitrogen dioxide and carbon monoxide
  • pollen and mold

Major sources of outdoor pollutants associated with asthma include:

  • power plants
  • passenger vehicles
  • diesel buses and trucks

There is a natural division of responsibility in the control of indoor and outdoor pollutants that trigger asthma attacks. For example, there are things that parents can do to reduce their children’s exposures to tobacco smoke, roach dust, dust mites and molds. Landlords have a responsibility to provide housing that is free of roach infestation, water leaks and other defects which give rise to asthma hazards. But neither parents nor landlords control pollution in the outdoor air. That must be done by government and industry.

Lead poisoning is a good example of the division of responsibility for indoor and outdoor pollution. Until the early 1980s, when EPA regulations began to remove lead from gasoline and to reduce industrial lead emissions, an astonishing 88% of children nationally were lead poisoned (by the current definition), as compared to less than 2% today. This is a dramatic public health success, though lead poisoning levels are still unacceptably high, particularly among poor children living in deteriorated housing. Parents and building owners still have a serious responsibility to protect children from lead paint hazards and soil contaminated from past leaded gasoline use. But these measures by themselves, without the dramatic drop in air lead levels, would never have reduced lead poisoning so substantially.

A brochure from the Northeast Ohio Ozone Task Force warns parents of asthmatic children that on high ozone days they should limit their children’s time outdoors. Do we really want a public health policy which tells parents of asthmatic children to try to find a safe place in the house where their children must hide when the outside air is too damaging to their lungs?


“Association of Ambient Ozone Exposure with Airway Inflammation and Allergy in Adults with Asthma” by Sumita Khatri, M.D., M.S. et al. Journal of Asthma 46:777–785, 2009.

Rationale. Previous studies have demonstrated associations of high ozone levels with increased epidemiologic as well as lung function measures of asthma activity. Objectives. In an observational study during the summer months, we hypothesized that higher ambient ozone levels are associated with more frequent symptoms, higher airway and systemic inflammation, as well as worse lung function in asthmatics as compared with non-asthmatic individuals. Methods. Thirty-eight asthmatics and thirteen healthy control subjects residing in metropolitan Atlanta were enrolled during peak ozone season. Medical histories, quality-of-life questionnaires, spirometry, serum immunoglobulin (IgE), peripheral eosinophil counts, and exhaled nitric oxide (NO) were obtained during study visits. Personal ozone exposures over the 2 days before presentation were estimated based on location and activity surveys. Main results. Upper airway symptoms were more frequent in asthmatics. Higher levels of ozone were associated with worse airflow obstruction, lower quality of life scores, greater eosinophilia, and higher exhaled NO levels in asthmatics. Finally, both asthmatics and non-asthmatics with allergies showed associations between air quality and airway inflammation. Conclusions. In adults with asthma but not controls studied during peak ozone season, increasing ozone exposure predicted lower lung function and increased biomarkers of respiratory and systemic inflammation. These associations were enhanced in atopic participants, both with and without asthma. Importantly, the study findings were noted while atmospheric ozone levels were predominantly within the current and revised national air quality standards.

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