According to a variety of studies over the last two decades, while cigarette smoking does not lead to mesothelioma, cigarette smokers who are exposed to asbestos are about 50 to 84 times more likely to develop asbestos-related lung cancer.
Smoking causes the most preventable deaths in the United States. Almost 500,000 Americans die from a smoking-related cause each year. The link between smoking and lung cancer, lung diseases and other respiratory issues is well known, but the habit can also heighten the risk of asbestos-related diseases, like mesothelioma, following exposure to the toxin. Smokers have an altered inflammatory response due to the trauma experienced within the lungs from cigarettes. This unbalance leads to the greater risk of hardening, scarring and damaging lung tissue following exposure to asbestos.
Mesothelioma and Smoking
There is no direct link between smoking and mesothelioma, as the only known cause of the cancer is asbestos exposure. However, research has shown that smoking is a risk factor for mesothelioma if asbestos exposure has occurred.
The increased risk of developing mesothelioma is caused in part by there being fewer cilia (hair-like structures that move debris out of airways) in the lungs of a smoker. With each cigarette smoked, the functionality of cilia is temporarily impaired. With long-term smoking leading to fewer cilia, the lungs are unable to properly clean themselves of dangerous particles, like asbestos fibers.
The job of cilia is further complicated by the elevated mucus levels and decreased oxygen intake in a smoker's lungs. The mucus can not only cause infection, but may also trap asbestos fibers. The scarring incurred from these fibers is compounded by the compromised alveoli, or air sacs, within the lungs. The alveoli are damaged when smoking, leading to more scarring within the lungs. The scarring hinders oxygen intake, which can escalate any breathing difficulty experienced due to the presence of asbestos within the lungs.
The risks of asbestos exposure and smoking may be even more severe in those who work in high-risk industries. Occupational asbestos exposure is the most common cause of mesothelioma and other asbestos diseases, with an estimated 125 million people exposed to asbestos on the job each year. Because of the high incidence rate, the National Cancer Institute advises that people who have experienced occupational exposure should not smoke or quit smoking to mitigate mesothelioma risk. Often, workers face exposure to higher concentrations of asbestos fibers during long durations of time, increasing the risk of mesothelioma. Should these workers also smoke, the asbestos and toxins from cigarettes can further irritate and scar lung tissue, which may lead to the asbestos cancer developing and progressing more quickly than the usual long latency period of 10 – 50 years.
Continuing to smoke once the cancer has developed can also worsen a mesothelioma patient's overall quality of life. Studies show that smoking exacerbates the symptoms associated with pleural mesothelioma, such as shortness of breath and cough. Smoking after diagnosis can also worsen side effects experienced from common treatments, as well as lessen the effectiveness of the treatments. Smoking may also lead to a co-occurring cancer diagnosis, such as non-asbestos lung cancer, oral cancer or esophageal cancer, among others.
Quitting smoking improves overall health immediately and reduces risk of mesothelioma and numerous other cancers. For some cancer patients, the benefits of quitting smoking can include improved circulation and normalization of blood carbon monoxide levels. Research has also shown it may increase life expectancy and reduce the risk of dying by 30 – 40%.
Smoking and Asbestosis
Asbestosis is a chronic lung condition that develops after experiencing asbestos exposure. Over time, inhalation of asbestos fibers causes scarring and inflammation of the lung tissue. Researchers believe that smokers have an elevated risk of asbestosis because smokers’ lungs are already damaged from cigarettes and face additional scarring and irritation from the toxic fibers. The damage to the lungs from smoking before asbestos exposure ultimately allows more asbestos fibers in the lungs, leading to rapid development of disease.
Research has also shown secondhand or environmental tobacco smoke can increase the risk for asbestosis and other asbestos diseases for fetuses. The exposure to smoke when in utero can alter the child’s immune response to asbestos later in life, making them more susceptible to disease after asbestos exposure. The risk is compounded when the exposure to environmental tobacco smoke continues into early development.
For smokers diagnosed with asbestosis, the severity of the condition and its symptoms increase with age. Asbestosis treatment options are focused on improving a patient's ability to breathe through use of inhalers and other medications. Smoking can disrupt the benefits from the treatment regime. Additionally, among both smokers and nonsmokers, those who have asbestosis have an elevated risk of developing lung cancer and mesothelioma, making treatment even more important.
Asbestos-Related Lung Cancer and Smoking
Studies have found that asbestos-related lung cancer accounts for about 3% of all lung cancer diagnoses. Though smoking is the most common cause of lung cancer, exposure to asbestos can also develop tumors in the lung tissue that lead to the disease.
The risk of asbestos-related lung cancer is compounded in smokers and those who have asbestosis. A study analyzing the prevalence of lung cancer among insulators found that there was an increased rate of cancer among smokers who were also exposed to asbestos on the job. Specifically, researchers found:
- Smokers who faced asbestos exposure were 14.4 times as likely to develop lung cancer than nonsmokers.
- In workers who developed asbestosis and still smoked, the risk of lung cancer was nearly 37 times higher than in nonsmokers.
- Asbestos exposure and smoking led to a risk of dying of lung cancer more than 28 times higher than nonsmokers.
While smoking causes an increased lung cancer risk in asbestos workers, studies have shown that after quitting smoking there is a significant drop in incidence rate. Thirty years after quitting smoking, asbestos workers have the same risk of developing lung cancer as a nonsmoker. In a 2013 study, researchers found that within 10 years of quitting, participants’ lung cancer mortality rates were the same as those who had never smoked. In the study, lung cancer mortality was 177 deaths per 10,000 among current smokers, and after participants quit, smoking mortality dropped to 90 deaths per 10,000.
Asbestos in Cigarettes
Asbestos has known fire retardant properties and because of this ability, the carcinogen was used as an additive in Lorillard’s Kent cigarette filters. The company's filters were made with crocidolite asbestos from 1952 – 1956. One filter from a Kent cigarette manufactured during this time period contained 10 mg of crocidolite. Within the first two puffs of an asbestos-containing cigarette, microscopic asbestos fibers could be found in the cigarette smoke. If a person smoked a pack of these Kent cigarettes a day, they would inhale more than 100 million crocidolite fibers a year.
A study analyzing asbestos-related disease among the workers producing the asbestos-containing cigarette filters found elevated rates of disease. Of the 33 men evaluated, eight died from lung cancer, five from malignant mesothelioma and five due to asbestosis. Additionally, among the workers still living, there have been four cases of asbestosis and two lung cancer diagnoses.
Anyone who smoked or was exposed to a loved one’s cigarette smoke from Kent cigarettes at this time should consult a doctor about their increased risk of asbestos-related diseases.
Author: Linda Molinari
Editor in Chief, Mesothelioma Cancer AllianceRead about Linda
Reviewer: Annette Charlevois
Patient Support CoordinatorRead about Annette
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