Smoker's Lungs vs. Normal Healthy Lungs

Visual, Cellular, Molecular, and Functional Changes in Smoker's Lungs

Many people remember hearing about the difference between smoker's lungs and normal healthy lungs at some point in time. These changes occur on a visual level, on a cellular level (under the microscope), and even on a molecular level.

In addition to these structural changes, there are several functional differences between healthy lungs and smoker's lungs as well, ranging from lung capacity to oxygen exchange. You may even recall the posters depicting the black, ugly-looking lungs of people who smoke. Does that really happen? What does cigarette smoke really do to the lungs?

What Are Smoker’s Lungs?

A smoker’s lungs may have blackish or brownish coloration, have diminished lung capacity, increased elasticity, and contain more infectious bacteria.

Smoker's vs. Normal Healthy Lungs

To really comprehend the effect of tobacco smoke on the lungs we need to take a look at both the anatomy—how the appearance of the lungs changes, and the physiology—how the function of a smoker's lungs differ from those of healthy lungs.

Yet we want to dig even deeper than that. What do a smoker's lungs look like beginning with the changes you can see with your naked eye, down to the genetic changes too small to even be seen under a microscope, but often more ominous?The posters we spoke of earlier didn't lie. Let's start with what you may see if you could look at whole lungs exposed to tobacco.

Lung Appearance

The photo above is honestly what the lungs of a life-long smoker look like on a visual inspection with the naked eye. It's important to state that not all black lungs are related to tobacco smoke.

Other irritants that can be inhaled may cause this appearance as well, such as the black lung disease sometimes seen in coal miners. Yet, it's very easy to tell when looking at a set of lungs whether or not a person smoked during his life.

Many people wonder what the black or brown color comes from.

When you inhale cigarette smoke, there are thousands of tiny carbon-based particles that are inhaled.

Our bodies have a special way of dealing with these particles to get them out of the way if you will.

As soon as you inhale a puff of cigarette smoke, your body is alerted to the fact that toxic particles have invaded. Inflammatory cells rush to the scene. One type of white blood cell called macrophages may be thought of as the "garbage trucks" of our immune systems. Macrophages essentially "eat" the nasty brown-black particles in cigarette smoke in a process called phagocytosis.

Since these particles could be damaging even to garbage truck cells, they are walled off in tiny vesicles and stored as toxic waste. And there they sit. As more and more macrophages containing debris build up in the lungs and lymph nodes within the chest, the darker the lungs appear.

You may be wondering if the brown and black color ever goes away. After all, macrophages don't live forever. When a macrophage dies, and the vesicles of cigarette waste are released, younger macrophages rush to the scene and ingest the particles. This process can occur over and over during a person's life.

This is not to say that healing doesn't take place when someone quits smoking. It does. But the discoloration in the lungs may remain indefinitely.

Smoker's Lungs at a Cellular Level

Taking a step down in size and looking at the lungs more closely, an increasing number of tobacco-related injuries are found. Under a microscope, the cells and surrounding tissues become visible as a well-appointed city, but a city ravaged by the toxic cloud of smoke that has descended upon it. Different structures in the respiratory tract are affected in different ways.


The cilia are tiny hair-like appendages that line the bronchi, and the smaller bronchioles. The job of the cilia is to catch foreign material that finds its way into the airways and propel it up and out of the lungs to the throat in a wave-like manner. From the throat, this material can then be swallowed and destroyed by stomach acids.

Unfortunately, toxins in cigarette smoke such as acrolein and formaldehyde paralyze these tiny cilia so they cannot perform their function. This result is that other toxins (over 70 of them carcinogens) and infectious organisms end up being left within the lungs where they can do damage both at the cellular level and at the molecular level, changes that can, in turn, lead to cancer and other diseases.


Inflammatory cells that are drawn to the scene in the airways secrete mucus in response to the harmful chemicals in cigarette smoke. This mucus can limit the amount of oxygen-rich air that reaches the smallest airways where gas exchange takes place. Mucus can also provide a nourishing breeding ground for the growth of harmful bacteria.

The Airways

Under the microscope, the airways can appear stretched out—like the elastic in an old pair of shorts. This decrease in elasticity caused by components of tobacco smoke has important functional repercussions as well (discussed later on).

The Alveoli

The alveoli are the smallest of airways and the final lung-based destination of oxygen that we breathe in. These alveoli contain elastin and collagen which allows them to expand with inspiration and deflate with expiration. Altogether, the surface area of your alveoli is around 70 square meters, and if you laid them flat and placed them end to end they would cover a tennis court.

Toxins in cigarette smoke damage these tiny structures in a few ways. It is easy for toxins to damage the thin walls causing them to rupture. Cigarette smoke also damages the alveoli that remain intact, decreasing their ability to expand and contract.

Damage to the alveoli is a self-perpetuating problem. As more alveoli become damaged, there is more air trapping in the alveoli (air cannot be breathed out) which results in the dilation and rupture of more alveoli.

In general, a large percent of the alveoli must be damaged before symptoms—hypoxia due to less oxygen being present for exchange to take place—occurs. Problems with oxygen exchange between the alveoli and capillaries are discussed further under function.

The Capillaries

At the cellular level, it's not just lung tissue that is damaged. The tiniest of blood vessels, the capillaries, that are closely associated with the smallest airways are also damaged by tobacco smoke.

Just as smoking can cause the damage to larger blood vessels (that can eventually lead to heart attacks), it can cause scarring and thickening of the capillary walls in the lungs—walls that oxygen needs to pass through in order to combine with the hemoglobin in red blood cells to be carried from the lungs to the rest of the body.

Genetics and Epigenetics

To really understand how smoking causes some lung diseases such as lung cancer, we need to look deeper inside the cells to the molecular level. This is a level that we can't see directly through a microscope.

In the nucleus of each of our lung cells lives our DNA—the blueprint of the cell. This DNA contains the instructions for making every protein that is needed for the cell to grow, function, repair itself, and tell the cell it is time to die when it becomes old or damaged.

You may have heard that a series of mutations in a cell is responsible for the link between lung cancer and smoking, but many mutations usually take place prior to a cell becoming cancerous.

There are usually thousands of mutations in a single lung cell exposed to tobacco.

Some genes in lung cells code for proteins that are responsible for the growth and division of the cell. One type of genes called oncogenes, cause cells to grow and divide (even when they shouldn't). Other genes, called tumor suppressor genes, code for proteins which repair damaged DNA or eliminate damaged cells which cannot be repaired.

Several carcinogenic components in cigarette smoke have been found to cause mutations but studies have even shown ways in which tobacco specifically causes the damage which may lead to cancer. For example, some tobacco carcinogens cause mutations in the p53 gene, a tumor suppressor gene that codes for proteins that repair damaged cells or eliminate them so that a cancer cell isn't born.


Finally, in addition to genetic changes caused by smoking, tobacco can cause "epigenetic" changes in lung cells as well. Epigenetic changes refer not to actual changes in the DNA of a cell, but the way that genes are expressed.

According to a 2017 study, DNA methylation (epigenetic changes) that can be detected in the blood of people who smoke are associated with an increased risk of lung cancer. Unlike genetic changes in cells, epigenetic changes are more likely to be reversible with a healthy lifestyle.


Just as there are many changes that occur structurally in the lungs of someone who smokes, there are several changes that take place on a functional level as well.

Pulmonary function tests comparing people who smoke with those who do not smoke often show changes very early on, even in teens who smoke, and long before any symptoms occur.

Some people who smoke feel reassured that if they are breathing without problems, they don't have a problem. Yet a large percent of lung tissue is usually destroyed before any symptoms occur.

To understand this better, consider that people who have a whole lung removed (a pneumonectomy), and are otherwise healthy, can adapt so that they can carry on a reasonably normal lifestyle. Some have even climbed mountains.

Relative Lung Capacity

Smoking can affect measurements of lung function in a number of ways.

Total Lung Capacity

The total lung capacity (TLC), or the total amount of air you can breathe in taking the deepest breath possible is decreased by smoking in several ways. Smoking can result in damage to muscles in the chest reducing the expansion necessary to take a deep breath.

The elasticity of the smooth muscle in the airways is likewise affected, and combined with the loss of elasticity, can limit the amount of air breathed in as well.

And at a microscopic level, when fewer alveoli are present (due to destruction by cigarette smoke), or air can't reach the alveoli (due to cigarette-related damage to the airways and build up of mucus), the intake of breath is also affected. These forces all work together to decrease lung capacity.

If a smoker goes on to develop COPD, their TLC will go up because the obstruction will lead to air being trapped in the lungs and thus overall lung volumes go up. As TLC goes up, the diaphragms are flattened and put at a mechanical disadvantage for effective ventilation, which leads to significant dyspnea.

Forced Expiratory Volume

In addition to lung capacity, smoking results in difficulty in exhaling the carbon dioxide that is transferred from the capillaries in the lungs to the alveoli. As noted above, decreased elasticity of the larger airways and decreased recoil of the alveoli leads to air trapping. This results in a decrease in forced expiratory volume.

Smoking Cessation Helps

Thankfully, researchers have noted that one of the benefits of quitting smoking that occurs after only 2 weeks is an increase in both lung capacity and expiratory volume.

Oxygen Exchange

It's not just the ability of oxygen to enter and pass down to the alveoli, or even the number of healthy alveoli present. Oxygen that reaches that alveoli must pass through the single cell lining of the alveoli and then through the double cell layer of the capillaries to reach the hemoglobin in red blood cells to be delivered to the rest of the body.

Diffusing Capacity

As noted above, cigarette smoke can affect both the alveoli and the lining of the capillaries making the passage of oxygen and carbon dioxide between the two more difficult. Not only is there less surface area available for gas exchange, but the exchange is compromised. It's harder for oxygen to pass through the scarred walls of the alveoli and capillaries.

The diffusing capacity is a pulmonary function test which measures this ability of a gas to make this transition from the alveoli into the bloodstream. We've known for several decades that cigarette smoking can reduce diffusing capacity.

Other Physiological Changes

There are many more changes that occur in the lungs of someone who smokes, and the ones mentioned here only touch the surface. We mentioned how cigarette smoke can affect the capillaries, but also affects every blood vessel in the body. Damage to the larger blood vessels can lead to changes in blood flow that compromise the delivery of blood to the capillaries in the lungs in the first place.

And it's not just the arteries. Cigarette smoking is associated with a significantly increased risk of blood clots in the legs (deep venous thrombosis). These blood clots can in turn break off and travel to the lungs (pulmonary emboli) causing further damage, resulting in less healthy lung tissue (if a person survives).

While some of these changes are not reversible, it is never too late to quit smoking both to minimize the damage and to allow your body to repair the damage that can be restored and healed.

The Bottom Line

Looking at all of the structural and functional changes in the lungs of someone who smokes stresses the importance of smoking cessation, though it's not just the lungs that are of concern.

There are a multitude of diseases caused by smoking, with tobacco playing a role in nearly every body system. It is also not just lung cancer that is of concern. Take a look at this list of cancers caused by smoking if you still feel any reluctance to stop today.

If you still need a few facts to encourage you to quit:

  • 30% of cancers are due to smoking
  • Overall, one in five deaths are due to smoking
  • Smoking is responsible for 80% of lung cancers, the leading cause of cancer deaths in both men and women
  • Smoking is responsible for 80% of COPD deaths, the fourth leading cause of death in the United States

But the news isn't all bad:

  • Heart disease risk drops drastically within a year of quitting
  • Stroke risk drops significantly two to five years after quitting
  • The risk of many cancers declines significantly by five years post-quitting

Quitting Smoking

Thankfully, quitting smoking at any time can stop further damage from being done to your lungs and can reduce your risk of developing the diseases and cancers linked to the habit. We know it's not easy. Yet it's possible. Start today with quit smoking lesson 101 - reasons to quit in order to make this attempt your final and successful attempt to kick the habit.

A Word From Verywell

It can be somewhat overwhelming to look at the vast number of ways that smoking affects both the structure and function of the lungs, but the important point is that smoking does not affect the lungs in just one way. Even if we had a way to bypass the damage caused, say, to alveoli, smoking would still be a problem. I

n other words, there's no healthy alternative to quitting. Despite this vast amount of damage, our bodies are amazingly resilient, and repair begins only seconds after the last puff.

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6 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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