The Effects of Carbon Monoxide From Cigarette Smoking

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As of Dec. 20, 2019, the new legal age limit is 21 years old for purchasing cigarettes, cigars, or any other tobacco products in the U.S.

Carbon monoxide (CO) is a poisonous, colorless, and odorless gas that is produced when carbon-containing fuels burn incompletely. It is present in indoor and outdoor air in varying amounts from vehicle exhaust, gas stoves, wood-burning stoves, furnaces and cigarette smoke—which can contain high levels of carbon monoxide. 

Carbon Monoxide in the Human Body

When carbon monoxide enters the lungs through breathing, it binds with hemoglobin in red blood cells to make carboxyhemoglobin (COHb), which is then transported into the bloodstream. Once this happens, oxygen cannot bind with receptors on the same cell.

Carbon monoxide is much faster at binding with hemoglobin than oxygen (about 200 times faster). So when CO is present in the lungs, it wins the spot on the red blood cells. This process diminishes the oxygen-carrying capacity in the bloodstream.

Carbon monoxide is quick to connect with red blood cells but is slow to exit the body, taking as much as a day to be exhaled through the lungs.

An abundance of carbon monoxide in the bloodstream starves the body of oxygen. In the worst cases, this can be fatal.

Carbon Monoxide in a Smoker's Body

The normal level of COHb in the bloodstream from environmental exposure to carbon monoxide is less than 1%. For smokers, COHb saturation in the blood is much higher. Factors including brand, number of cigarettes smoked and the amount of time affect saturation levels.

A pack-a-day smoker can have a 3% to 6% COHb level in the blood. In someone who smokes two packs a day, the level may be 6% to 10%. In a three pack-a-day smoker, COHb levels may reach 20%.

Carbon monoxide blood saturation above 1% can cause physical symptoms such as:

  • Increased heart rate
  • Reduced tolerance for exercise
  • Headache and visual distortions can occur at high levels of CO saturation

Lack of oxygen in cells also forces the heart to work harder to distribute oxygen around the body. This makes CO a major contributor to heart disease, including heart attacks and atherosclerosis. Secondhand smoke may also contain high levels of CO.

Smoking and Carbon Monoxide Poisoning 

It is possible to suffer CO poisoning from cigarette smoking if a large number of cigarettes are smoked in quick succession in an enclosed space. In one documented case, a woman made a trip to the emergency room at her local hospital because she felt dizzy and had a headache. Blood work revealed an elevated level of carbon monoxide in her blood.

Her home was checked for a carbon monoxide leak and none was found. A week later she returned to the hospital with the same symptoms. This time, the carbon monoxide in her blood was nearly 25%. She was a heavy smoker and had smoked numerous cigarettes in a short period of time.

For most smokers, symptoms of too much CO in their bloodstream, like a racing heart, headaches, and nausea, will cause them to slow down on the smokes before they need medical help. But the only way to solve the problem for the long term is to quit smoking.

Symptoms of Carbon Monoxide Poisoning

Breathing low levels of CO can cause:

  • Fatigue
  • Increased chest pain in people with chronic heart disease

In otherwise healthy people, inhaling higher levels of carbon monoxide may cause flu-like symptoms (with no fever) such as:

  • Headaches
  • Dizziness
  • Weakness
  • Sleepiness
  • Nausea
  • Vomiting
  • Confusion
  • Disorientation

At very high levels, exposure to carbon monoxide will cause loss of consciousness and death, so it is important to seek medical attention if you experience any of the symptoms above.

A Word From Verywell

Carbon monoxide is just one of many hazardous chemicals in cigarette smoke. To date, more than 7,000 chemical compounds, 250 of which are known to be poisonous and upwards of 70 that have been identified as carcinogens, are known to be present in cigarette smoke.

If you are still smoking, it's time to resolve to quit. Don't fear smoking cessation. Others have done it successfully. You can too.

7 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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  7. National Cancer Institute. Harms of cigarette smoking and health benefits of quitting.

Additional Reading

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