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Asthma and the Environment

Asthma attacks have been linked to exercise, respiratory infections, and exposure to environmental factors such as allergens, tobacco smoke, and indoor and outdoor air pollution. Asthma attacks can be reduced by taking medication and avoiding exposure to known triggers.

A number of studies have reported associations between air pollution exposures and asthma. For example, researchers have found an association between increased hospital admissions for asthma and particulate matter, an outdoor air pollutant.

Air pollution, such as ozone and particle pollution, can make asthma symptoms worse and trigger attacks. Adults and children with asthma are more likely to have symptoms when ozone and particle pollution are in the air. Ozone is often found in smog and particle pollution is often found in haze, smoke, and dust.

Ozone is often worst on hot summer days, especially in the afternoons and early evenings. Particle pollution can be bad any time of year, even in winter. It can be especially bad:

  • when the weather is calm, and air pollution can build up,
  • near busy roads, during rush hour, and around factories that produce air pollution and,
  • when smoke is in the air from wood stoves, fireplaces, or burning vegetation.

Important asthma triggers are:

  • environmental tobacco smoke, also known as secondhand smoke;
  • dust mites;
  • outdoor air pollution;
  • cockroach allergen;
  • pets;
  • mold;
  • strenuous physical exercise;
  • some medicines;
  • bad weather, such as thunderstorms, high humidity, or freezing temperatures;
  • some foods and food additives; and strong emotional states that can lead to hyperventilation and an asthma attack.
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