How Does Smoking Affect Alveoli in the Lungs?

alveoli of the lings
Illustration of alveolar sacs in lungs. Science Picture Co/Collection Mix: Subjects/Getty Images

Alveoli (singular is alveolus) are tiny, delicate air sacs deep within the lungs. They look like little clusters of grapes at the ends of the bronchial branches in the lungs.

They are an essential part of the body's respiratory system, which is the part of the body that allows you to breathe. Alveoli function to move oxygen in and carbon dioxide (CO2) out of your bloodstream. Smoking can lead to lung disease and tobacco smoke can damage the alveoli and impair their ability to function.  

How Many Alveoli Are in the Lungs?

When we inhale, air enters the lungs and travels through passageways to reach 480,000,000 alveoli.

The size of a single alveolus has an approximate diameter of 200-500 microns, regardless of lung size. As a point of reference, one micron is a millionth of a meter. The diameter of a human hair is about 70 microns, so one alveolus would be close to equal the diameter of three human hairs put together. Tiny!

Alveoli contain collagen and elastin. Collagen offers firmness to the air sac structure and elastin, bounce. When air is inhaled into the lungs, elastin allows alveoli to expand, and upon exhalation, spring back to their original size.

The total surface area of all alveoli in a healthy adult set of lungs is approximately 70 square meters, or 800 square feet (approximately the size of half a tennis court). 

Alveoli Function in the Lungs

Much of the outside surface area of lung alveoli are covered with tiny capillaries. These capillaries and the walls of alveoli share a very thin membrane that allows oxygen from inhaled air to pass through the walls of alveoli and enter the bloodstream via the capillaries. At the same time, carbon dioxide is pushed out in the same way when the air is exhaled.

The total amount of surface area available for this gas/blood exchange determines how well a person is able to breathe. In a normal healthy adult, there is an abundance of available area for this process.

What Smoking Can Do to Alveoli

Over time, the toxins from inhaled cigarette smoke break the thin walls of alveoli, leaving larger, less efficient air sacs. The sacs also begin to lose their bounce, making it harder to bring in the oxygen and expel carbon dioxide. Both can become partially trapped in the lungs. In a smoker, this process signals the beginning of emphysema, a form of COPD. 

The damage from emphysema cannot be reversed. Once air sacs are broken, they do not mend.

However, if exposure to cigarette smoke stops soon enough, the damage can be halted. If smoking continues, there will come a point where lung damage will progress regardless of whether a person stops smoking or not.

Conditions That Impact Alveoli

In addition to smoking, there are other conditions that can affect alveoli. Some of these conditions can occur due to smoking, but some may be related to other medical conditions. These include:

  • Acute respiratory distress syndrome: This life-threatening condition causes fluids to accumulate in the alveoli.
  • Asthma: This condition causes inflammation and leads to air becoming trapped in the alveoli.
  • Chronic obstructive respiratory disease (COPD): COPD damages the alveoli and reduces the surface area in the lungs, making it more difficult for gas exchange to occur.
  • Emphysema: This chronic lung disease is often the result of smoking and leads to the destruction of alveoli. It causes air to become trapped in the alveoli, making it more difficult to expel air from the lungs.
  • Lung cancer: Some types of lung cancer, such as bronchioloalveolar carcinoma, begin in the alveoli of the lungs.
  • Pneumonia: Lung infection caused by viruses, bacteria, and fungi can cause inflammation in the alveoli.
  • Pulmonary edema: This condition causes fluid to build up in the alveoli, potentially resulting in respiratory failure.

Good Reasons to Stop Smoking Now

The lesson here is to stop smoking as soon as you possibly can. Every cigarette you smoke is hurting your body in numerous ways. Cigarette smoke is full of chemicals that cause cancer and are poisonous. 

Some cigarette additives are radioactive and there is evidence that these chemicals leave permanent radioactive deposits in the smoker's lungs. Researchers believe this is a contributing factor to the risk of ​lung cancer.

Once inhaled, cigarette toxins hitch a ride through your bloodstream via the alveoli where they have access to every organ in your body. It's no wonder that cigarette use is linked to so many diseases.

There is nothing to recommend smoking. We think we enjoy it, but it's an addiction, plain and simple. Taking steps to quit smoking, including creating a smoking cessation plan and finding out what quit smoking resources are available, can help you take care of your lungs and protect your alveoli from further damage.

Frequently Asked Questions

  • How many alveoli are in the lungs?

    Research suggests that there are an average of 480 million alveoli in the lungs, with a range between 274 and 790 million. Lung size and volume is closely related to the alveolar number. Larger lungs have significantly more alveoli.

  • Is there a way to repair or detox your lungs after smoking cigarettes?

    Smoking damages lung alveoli and they do not regenerate after they have been damaged or destroyed. However, stopping smoking now can halt the damage and improve lung health over time. Ways to improve your lung health include avoiding pollutants, getting regular exercise, avoiding infections, and staying hydrated.

  • How long does it take for your lungs to fully recover after you quit smoking?

    Within one month to one year of quitting smoking, the tiny hair-like structures in your lungs known as cilia begin to heal and function normally. Around ten years after quitting, your risk of developing lung cancer drops by half.

  • What keeps the alveoli in the lungs functioning properly and not collapsing?

    The lung cells release a pulmonary surfactant, a fatty substance, that surrounds the alveoli. The substance serves to lower the surface tension, preventing the alveoli from collapsing as you exhale.

8 Sources
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Ochs M, Nyengaard JR, Jung A, Knudsen L, Voigt M, Wahlers T, Richter J, Gundersen HJ. The number of alveoli in the human lung. Am J Respir Crit Care Med. 2004;169(1):120-4. doi:10.1164/rccm.200308-1107OC

  3. The Respiratory System. Alveoli.

  4. Encyclopedia Britannica. Pulmonary alveolus.

  5. COPD Foundation. What is COPD?.

  6. Kelley DE, Boynton MH, Noar SM, et al. Effective message elements for disclosures about chemicals in cigarette smoke. Nicotine Tob Res. 2018;20(9):1047-1054. doi:10.1093/ntr/ntx109

  7. American Lung Association. Protecting your lungs: Tips to keep your lungs healthy.

  8. American Cancer Society. Health benefits of quitting smoking over time.

By Terry Martin
Terry Martin quit smoking after 26 years and is now an advocate for those seeking freedom from nicotine addiction.