Causes & Risk Factors

What are the causes of COPD?1-5

Chronic obstructive pulmonary disease (COPD) has many possible causes, but one is by far the most common: tobacco smoke. Nine out of ten cases of COPD are smoking related. Most cases of COPD are caused by different kinds of “exposures,” which are toxic irritants in the air that a person breathes. COPD caused by exposure can result from:

  • Inhaling a small amount of irritants over a long period of time, or
  • Inhaling a large amount of irritants over a short period of time.

However, COPD does not only affect current and former smokers – around one in six people with COPD have never smoked at all. Sometimes, natural or genetic features can cause certain people to be born with a higher chance of developing COPD. For these people, their risk of COPD does not depend on exposure to airborne irritants. Developing COPD from these kinds of causes is much more rare than COPD caused by exposure to irritants.

Which kind of exposure is the main cause of COPD?7

Tobacco smoke is the number-one cause of COPD around the world. Between 15% and 20% of smokers will develop COPD during their lives. Regularly inhaling any kind of tobacco smoke can cause COPD. This includes pipes and cigars as well as cigarettes. Breathing in others’ tobacco smoke at home or in the workplace (also called “second-hand smoking” or “passive smoking”) can even cause people who have never personally smoked to develop COPD.

What other kinds of exposures can cause COPD?7,8

Exposure to other types breathable particles can also irritate the lungs and cause COPD to develop or get worse:

  • Airborne irritants in the workplace
  • Indoor air pollution
  • Outdoor air pollution

Breathing in dangerous irritants in the workplace is a known cause of COPD. This affects people who work in places where they breathe in particles that irritate their lungs on a regular basis. These particles can come from substance such as:

  • Chemicals
  • Dust
  • Fumes
  • Vapors

It usually takes many years of exposure to powerful irritants for COPD to develop. However, that doesn’t change the fact that it is important to be aware of air quality in a workplace.

Indoor air pollution in the home can also be a cause of COPD. This is more common in countries where people cook food and heat their homes by burning certain types of natural fuels. Burning fuel indoors in a home that is not well ventilated can cause persistent lung irritation over time, which leads to COPD. This cause mainly affects women and children in those countries who spend large amounts of time in the home.

High levels of outdoor air pollution, mostly in urban areas, is known to be harmful for people with COPD. It can cause more frequent exacerbations, for instance. Researchers are not yet sure whether exposure to outdoor air pollution can cause COPD by itself. However, it can make people with high levels of exposure to other types of irritants – such as smokers – more likely to develop COPD.

What are the causes of COPD not linked to exposure?1-6

Some people are born with a rare genetic condition called alpha-1 antitrypsin (called “AAT” for short) deficiency. People with AAT deficiency have livers that do not to make enough of a certain kind of important protein called AAT. This protein’s job is to help protect the lungs from damage. Because they don’t have enough AAT to protect their lungs, breathing irritants can be very harmful for people with AAT deficiency.

AAT deficiency is very rare, but people with this condition can develop COPD without ever being exposed to any irritants like tobacco smoke. People with AAT deficiency are also much more likely to develop COPD if they do smoke.

Some people with COPD have never been exposed to irritants, and do not have the AAT deficiency. For this reason, scientists think that the tendency to develop COPD might be passed down though families on other genes, too. Future research may be able to identify this genetic link in certain families.

Some people with asthma can develop COPD if their asthma is not treated in the right way, and their airways are constantly inflamed over a long period of time. People who experienced many respiratory infections during childhood can sometimes develop COPD as well.

Who has a higher risk of developing COPD?1-8

A person’s risk of developing COPD generally depends on the total amount of all the different kinds of exposure that he or she receives throughout life. For example, a person who is a smoker, and also works in a place with airborne irritants, is more likely to get COPD than a non-smoking co-worker.

The following groups of people have a higher risk of developing COPD:

  • People 40 years of age or older, who are current or former smokers
  • People with a family history of COPD, who are current or former smokers
  • People with asthma who smoke
  • People who began smoking during their teenage years
  • People whose mothers smoked during pregnancy with them
  • People who had asthma or frequent respiratory infections as a child
  • People exposed to workplace irritants over many years
  • People exposed to indoor air pollution over many years

By providing your email address, you are agreeing to our privacy policy. We never sell or share your email address.

Written by: Anna Nicholson | Last reviewed: July 2015.