How does pollution cause asthma?

July 3, 2024
Avatar for Jyoti Kinghorn, PhDJyoti Kinghorn, PhD
Air pollution causes asthma

Asthma is a chronic disease of the respiratory airways in which the airways in the lungs become inflamed. When someone breathes in polluted air, the pollutants in the air make contact with the airways in their lungs. In asthma, the body instigates an immune response to counter these environmental triggers causing inflammation and swelling which makes the airways narrower.

As less air passes through the lungs, the person experiences the typical symptoms of asthma such as coughing, shortness of breath, wheezing, and tightness of the chest. During a severe asthma attack, the person may feel dizzy and lightheaded and may need their quick-relief inhaler medication to help them breathe. Asthma can be serious and life-threatening. Thousands of children in the US lose their lives before the age of 5 due to lower respiratory issues caused by air pollution.

Air pollution can cause and exacerbate asthma

Air pollution is a well-known risk factor for developing asthma. Repeated exposure to pollutants in the air can cause asthma in children as well as adults. Studies have shown that exposure of mothers to air pollution even before they got pregnant, and during all stages of their pregnancy increased the risk of their children developing asthma during childhood. Children also had a higher risk of developing asthma if their mothers smoked during pregnancy.

Air pollution also worsens asthma. The pollutants irritate the lungs, cause inflammation that swells the airways and severely restricts the airflow, which results in asthma attacks and worsening asthma over time.

Types of air pollution that cause asthma

Air pollution can come from outdoor or indoor sources. It is estimated that outdoor air pollution causes 4.2 million deaths globally and indoor air pollution causes 3.8 million deaths.

Outdoor air pollution

Outdoor air pollution comes from sources such as industrial and vehicular emissions, mineral dust, pollen, and forest fires.

Indoor air pollution

Indoor air pollution comes from a variety of sources such as:

  • household dust
  • mold
  • smoke from burning tobacco, incense, or wood
  • vacuum dust
  • lint from fabrics
  • cleaning and cosmetic sprays
  • radon gas
  • pesticides (e.g. bug spray)
  • construction and paint products
  • degassing of new carpets and vinyl floors
  • Leaking in of pollutants from the outside

The quality of air indoors can be 2-5 times worse than outdoors.

Hazardous pollutants in the air

After studying various outdoor and indoor pollutants, the EPA has designated about 188 environmental pollutants as hazardous. These include gases such as ozone, ground-level or tropospheric ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and methane.

Another harmful pollutant is particulate matter. Particulate matter (PM) consists of small solid particles and liquid droplets of pollutants in the air. PM can be inhaled from polluted air with soot, dust, dirt, smoke, etc. PM is categorized based on size. PM10 are inhalable particles that are 10 micrometers or smaller. PM2.5 are smaller particles that are 2.5 micrometers and smaller. While larger particles clog up the upper airways of the lung, PM2.5 particles are so small that they penetrate deeper and deposit throughout the small airways and the alveoli (small air sacs) of the lungs.

Science links asthma to specific pollutants

Different research studies have found specific pollutants associated with the development of asthma.

  • In the US, ozone and PM2.5 were found to be the most significantly associated with worsening asthma and decreases in how well the lungs work (pulmonary function).
  • Cases of asthma due to non-viral causes were 2-3 times higher in urban kids than kids living in rural areas.
  • Exposure to nitrate, PM2.5, and PM10 was significantly associated with an increased risk of asthma and persistent wheezing.
  • PM2.5 and black carbon (released into the air from vehicle exhausts) were associated with lower pulmonary function that developed in mid-childhood (7-10 years of age).

Global warming makes things worse

The harms of air pollution are increasing because of global warming. Rising temperatures are resulting in increased ozone levels in the breathing air. Also, the prolonged warm weather is causing longer pollen seasons. Pollens are among the triggers that can set off asthma attacks

Inherited genetic changes and epigenetic changes affect asthma risk

Genetic and epigenetic risk factors 

Risk factors for developing asthma include both pollution-related and genetic risk factors.

Genetic risk factors

The presence of genetic factors known as asthma-associated loci on the DNA can make a person susceptible to asthma. There are at least 212 asthma-associated loci that have been identified in the genome of asthma patients. These factors are inherited from one’s parents and are not affected by the environment or air quality.


Epigenetic risk factors related to pollution

Epigenetic changes link air pollution to the development and exacerbation of asthma. Such changes are not in specific genes. Instead, they change the general structure of the DNA which affects the availability of that part of the DNA to the cellular machinery that would encode it into functional proteins. Epigenetic changes may make a sequence of DNA less accessible, more accessible, or have its expression silenced. The DNA sequence is thereby unable to “do its job”. The parts of the genome that are impacted may affect immune reactions which inflame the airways of the lungs in response to contact with pollutants.

Clean air reduces asthma risk

How to avoid asthma attacks from air pollution

Keep track of air quality

Keep a tab on the daily air quality in your area through television weather reports or online resources such as This website can show you the air quality by zip code, city, or state. The reports indicate the air quality on a map using color codes. Green indicates good air quality, yellow indicates moderate air quality, and red indicates unhealthy air quality. The website also reports PM10 and PM2.5 levels.

Avoid exposure to outdoor pollutants

If pollutants outside trigger your or your child’s asthma attacks, you can take measures to avoid contact with them.

  • Use air conditioning at home.
  • Minimize outside time on days with poor air quality.
  • If you must go out, traveling in a car with air conditioning can be helpful.
  • Even on good or moderate air quality days, avoid exercising or taking children to playgrounds near areas of high traffic.
  • Avoid going out if there is smoke from a forest fire, vegetation burning, or trash burning.
  • When necessary, wear a respiratory mask.

Avoid exposure to indoor pollutants

If you suspect that pollutants inside the house are causing asthma attacks, find out the triggers to try to avoid them.

  • If a new vinyl floor, carpet, paint job, construction, or repair in your house is triggering attacks, find a space in the house that is most free of pollutants and use an air purifier until the air is clean again. If the outside air is cleaner, consider camping out to sleep.
  • Clean the house often to remove dust, pet hair, dander, dust mites, etc. Notice how you feel after cleaning and eliminate cleaning products that worsen your asthma symptoms. Usually, asthma symptoms show up the day after the exposure.
  • Avoid burning wood at home.
  • Also void burning wood near your home such as in the yard. Do not burn trash.
  • Use exhaust that vents outside the house for cooking.
  • Keep a log of using fine powder and spray-on cosmetics. Notice if you feel asthma symptoms worsening after using a product.
  • Get a kit or low-cost indoor air monitor to check for indoor air quality. Radon gas can cause lung cancer, so check for radon gas levels too. You may be able to order free kits from your state to check for radon levels. Unfortunately, the CDC and EPA do not provide free indoor air monitors.
  • Use the EPA’s problem-solving tool and checklists to identify the possible causes of health complaints you may be having in your home or classroom.
  • When the outdoor air quality is good, spend more time outside preferring green spaces.

The information provided in our blog posts is for informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this blog.

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