Air pollution may worsen asthma symptoms and trigger asthma attacks. Exposure to air pollution when their mother was pregnant and in childhood may also increase a person’s risk of developing asthma. Monitoring air pollution levels can help asthmatics avoid health effects.

People with asthma have airways that are sensitive to various substances, or triggers, in the air. Air pollution and other airborne irritants are among the most common asthma triggers.

Air pollution is the presence of pollutants in the air that are hazardous to humans and other living things.

This article explores how air pollution affects asthma and what people with asthma should know about air pollution.

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Research suggests that air pollution at high concentrations may trigger asthma flares because it inflames and irritates the lining and receptors in a person’s airways. This causes the airways to tighten and swell, a common symptom of asthma.

Air pollution also contains substances that are toxic to the respiratory tract. Exposure to certain pollutants can trigger oxidative stress, a feature seen in severe asthma.

Oxidative stress is a condition where there are too many unstable molecules, known as free radicals, in the body and not enough antioxidants (substances that prevent cell damage) to get rid of them.

It can lead to tissue damage, such as from inflammation and hyperresponsiveness, in a person’s airways. Airway hyperresponsiveness is when a person’s airways are more sensitive to stimuli, such as pollutants, and narrow too much in response.

Ozone, a common air pollutant, triggers asthma attacks and makes it difficult to breathe deeply, as well as reducing lung function.

Learn more about the types and causes of asthma here.

Does air pollution cause people to develop asthma?

A 2020 review suggests that indoor and outdoor air pollution can contribute to the development of asthma.

The effects of oxidative stress due to air pollution can cause genetically susceptible people to develop asthma.

Exposure to traffic-related air pollution (TRAP), particularly during the second trimester of pregnancy, also has links with an increased risk of asthma development in children.

Childhood exposure to TRAP also increases the risk of asthma. A 2020 study found that exposure to air pollution early in life increased a person’s risk of developing asthma from childhood to early adulthood.

A mother’s exposure to secondhand smoke and maternal smoking may also increase an unborn infant’s risk of developing asthma, but genetic predisposition can also play a role.

Read more about the effects of air pollution on pregnancy here.

The types of air pollutants that can affect asthma are as follows:

Pollutant typeOzoneNitrogen oxideParticulate matter (PM2.5)
Effect on airways• inflammation
• oxidative stress
• airway hyperresponsiveness
• inflammation
• oxidative stress
• airway hyperresponsiveness
• inflammation
• oxidative stress

Particulate matter (PM2.5) consists of tiny particles of solids and liquids in the air. These particles can include:

  • soot
  • dust
  • dirt
  • smoke
  • liquids

Fine PM2.5 particles typically deposit throughout the respiratory tract, particularly in a person’s small airways and alveoli — tiny air sacs in the lungs.

Larger (coarse) particulate matter mainly deposits in the upper airways. Examples are organic debris from soil, road dust and metals, and roadway particles such as brake wear.

A 2017 study found that those with exposure to coarse particulate matter were more likely to develop asthma and need hospitalization or emergency visits.

Learn more about how the respiratory system works here.

Researchers have conducted numerous studies on the association between air pollution and asthma.

A 2017 study found that exposure to specific components of TRAP had a positive association with asthma onset.

Findings from a retrospective study show that air pollution is an independent risk factor for exacerbating asthma in the absence of viral infections.

A study in Denmark found that children with exposure to higher levels of PM2.5 are more likely to develop persistent wheezing and asthma.

Learn more about how pollution from traffic increases death risk here.

The United States Environmental Protection Agency (EPA) monitors air pollution levels using the Air Quality Index (AQI). AQI levels of 101 or higher are dangerous to people with asthma, but even AQI levels of 50–100 can worsen asthma symptoms.

People with asthma can get more information on the quality of air where they live from Many local weather forecasts also warn the public of high air pollution.

Various states and cities across the U.S. also call Action Days when AQI levels are at concerning levels. These levels are as follows:

AQI colorLevel of concernAQI levelsAir quality description
yellowmoderate50–100Air quality may pose a health risk for some people who are sensitive to air pollution, such as those with asthma.
orangeunhealthy for sensitive groups101–150Groups that are sensitive to air pollution may experience health effects. However, it is less likely that it will affect the general public.
redunhealthy151–200Groups that are sensitive to air pollution may experience more severe health effects. Air quality may also cause health effects in the general public.

Learn more about how air pollution can affect health here.

The American Lung Association advises people to take the following steps:

  1. Check for daily air pollution forecasts in TV weather reports, radio, online, and in newspapers.
  2. Avoid going outdoors when air pollution is high.
  3. Avoid exercising near high-traffic areas.
  4. Use less energy in the home because generating electricity and other energy sources creates air pollution.
  5. Look for alternatives to driving a car, such as using public transportation, carpooling, walking, or riding a bike.
  6. Do not burn trash or wood.
  7. Keep public places tobacco-free, and do not smoke indoors.

People with asthma can speak with a healthcare professional about the possibility of increasing their medication when air pollution is high. A person can include this in their own or their children’s asthma action plan.

A person should contact a healthcare professional immediately if they experience:

  • feeling faint, weak, or dizzy
  • finding it challenging to perform their usual routines
  • a cough that does not go away
  • wheezing, especially if it is different from their usual breathing pattern
  • wheezing that does not get better even after taking medications

Here are some common questions about air pollution and asthma.

Which climate is worst for asthma?

Extreme weather and sudden weather changes can irritate the airways. Some types of weather that can trigger asthma symptoms are:

Learn about other common asthma triggers here.

What are the potential sources of indoor air pollution?

There are many potential sources of indoor air pollution. They typically release gas or particles and include:

  • tobacco products
  • building materials and furnishings, such as flooring, upholstery, or insulation containing asbestos
  • humidification devices and central cooling and heating systems
  • personal care and hobby products
  • household cleaning products
  • excess moisture
  • outdoor pollution, such as pesticides and radon

Air pollution is a significant contributor to the development of asthma. It can also trigger and worsen symptoms in people with asthma.

It is vital for people with asthma to stay informed of air pollution levels and take necessary precautions to avoid triggering asthma attacks.

They should also talk with a healthcare professional if they experience any signs that their asthma is worsening.