How Do Smoking and Asbestos Exposure Affect Health?

Smoking is the leading cause of preventable death in the U.S., and asbestos exposure is the No. 1 cause of occupational deaths worldwide. Exposure to both can have detrimental effects on respiratory health and cancer risk.

The combination of smoking and asbestos exposure greatly increases a person’s risk of developing lung cancer. It also may accelerate the onset of asbestosis and increase the severity of symptoms. 

Smoking does not increase the risk of mesothelioma among people exposed to asbestos. Researchers do not fully understand why mesothelioma risk doesn’t increase with smoking, but they believe the greater risk of lung cancer relates to a synergistic effect between asbestos and smoking.

Smoking affects the development and severity of asbestos-related diseases in several ways.

  • Smoking represses the immune response to asbestos. When asbestos-exposed mice and human cell lines are exposed to cigarette smoke, central components of the innate immune system known to respond to asbestos are repressed. This is possibly the most influential factor that increases the risk of lung cancer among people exposed to asbestos who smoke.
  • Smoking impairs your lungs’ natural self-cleaning ability. The airways in your lungs are lined with tiny brush-like structures called cilia, which sweep dust particles out to keep your lungs clear. Smoking damages cilia, making it harder for them to expel pollutants, including asbestos fibers.
  • Smoking increases inflammation and scarring in your lungs. Tobacco smoke and asbestos fibers can cause the buildup of scar tissue in your lungs. In addition, smoking changes how your immune system reacts to asbestos, causing your lungs to develop even more scar tissue than they would otherwise. This can accelerate the onset of asbestosis.
  • Smoking reduces your lungs’ ability to absorb oxygen. Tobacco smoke gradually destroys many of your lungs’ alveoli — the tiny air sacs that transfer oxygen into the bloodstream. This adds to the breathing difficulty caused by any scar or cancer tissue that has formed around lodged asbestos fibers.
smoker and non smoker lungs comparison.
Smokers inhale toxic smoke into their lungs that reduces oxygen absorption and causes inflammation and scarring.

Studies have estimated that between 50% and 80% of asbestos workers are smokers. This factor, combined with the synergistic effect of asbestos and smoking, helps explain why cases of asbestos-related lung cancer outnumber other asbestos-related cancers, including mesothelioma. 

Smoking and Mesothelioma

Smoking has not been directly linked to mesothelioma. The primary cause of mesothelioma is asbestos exposure. However, smoking is a risk factor for developing asbestos-related lung cancer. If asbestos exposure has occurred, you may have an increased risk of developing mesothelioma.

Decades of research have not found an increased risk of mesothelioma among asbestos workers who smoke. 

Only one study from 2002 found a common gene mutation among a group of smokers with mesothelioma, but a 2013 study looking deeper into the topic found no relationship.

Smoking does worsen the pulmonary symptoms of mesothelioma and reduces your body’s overall ability to heal. Doctors advise all patients with cancer or respiratory illnesses to avoid tobacco smoke.

Smoking, Asbestos and Lung Cancer

The Centers for Disease Control and Prevention says smoking is the cause of 80% to 90% of lung cancer cases, while asbestos exposure is the primary cause in only about 4% of cases.

Any amount of asbestos exposure contributes to the incidence of lung cancer, even in heavy smokers, according to a 2020 study published in Environmental Research and Public Health. 

Both smoking and asbestos exposure can independently cause lung cancer, but when the two are combined the risks multiply. Decades of studies have shown varying degrees of multiplicative risk, which is likely affected by the exposure levels among the participants. 

A 2013 study involving more than 50,000 medical records from insulation workers revealed how occupational asbestos exposure and smoking have a synergistic effect on lung cancer death rates.

Occupational asbestos exposure on its own was associated with a lung cancer death rate five times higher than average. When asbestos exposure was combined with smoking, the death rate was 28 times higher than average. Among those who also developed asbestosis, the death rate was 36.8 times higher.

The study also showed quitting smoking gradually reduces a person’s risk of lung cancer, whereas the hazards caused by asbestos exposure are irreversible.

Death rate when asbestos exposure was combined with smoking

The death rate was 28 times higher than average when asbestos exposure was combined with smoking
Smoking combined with asbestos exposure significantly increased the death rate of insulation workers.
Source: American Journal of Respiratory and Critical Care Medicine, 2013

Smoking and Asbestosis

According to research by the Agency for Toxic Substances and Disease Registry, smoking increases the risk of asbestosis among those exposed to asbestos. 

Asbestosis is a chronic pulmonary disease in which the lungs undergo slow and repetitive scarring, or fibrosis. There is no known cure. Asbestosis is caused by the inhalation of asbestos fibers and is most prevalent among workers with long and heavy exposure to asbestos. 

A 1995 study published in American Journal of Respiratory and Critical Care Medicine concluded smokers have increased rates of asbestosis progression.

An earlier report showed approximately 12% of asbestosis patients might develop lung cancer. Asbestos-exposed smokers who develop asbestosis have a significantly increased risk of dying from lung cancer. 

The effect of smoking on asbestosis has been a point of debate among researchers, with some experts believing smoking contributes to asbestosis and others challenging this notion. 

Significant evidence exists to show how much smoking can worsen symptoms of asbestosis, including breathlessness.

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Asbestos in Cigarettes

In the U.S., one tobacco product is known to have been manufactured with asbestos as an ingredient: Kent Micronite filtered cigarettes. From 1952 to 1956, H&V Specialties manufactured cigarette filters for the Lorillard Tobacco Company using a type of asbestos called crocidolite.

Close-up detail of a 1952 Kent Micronite filter cigarette, showing the mouthpiece end with fibrous tufts of tiny crocidolite fibers.
Cigarette filters manufactured using asbestos exposed smokers to an even higher risk of cancer.

Lorillard marketed Kent Micronites as the safest cigarettes ever invented, claiming the design was inspired by high-tech industrial filtration technology. Unfortunately, crocidolite is now widely considered the most toxic form of asbestos.

Although crocidolite was used in certain specialized filters, the crimped crepe paper of the Micronite cigarette filter did not prevent consumers from inhaling microscopic crocidolite fibers when they smoked Kent cigarettes. 

One study found a smoker could inhale “an average of 170,000 crocidolite airborne structures” from only two puffs on a Kent Micronite.

In general, cigarette filters do not make cigarettes significantly safer. The filters typically only trap the largest tar particles, allowing most of the toxic substances in cigarettes to pass through. 

The Kent Micronite filter made smoking more dangerous by adding asbestos to the list of cancer-causing substances smokers were exposed to.