Asbestos and cancer
Asbestos is a group of six naturally occurring fibrous minerals known for their fire-resistant properties, historically utilized in various building materials and products. However, exposure to asbestos fibers, which can be released into the environment through both natural and human activities, is linked to serious health risks, particularly several types of cancer. Notably, asbestos is a known human carcinogen that can lead to malignant mesothelioma, a cancer affecting the lining of the lungs or abdomen, often with a long latency period of 30 years or more before symptoms appear.
In addition to mesothelioma, asbestos exposure is associated with laryngeal cancer, ovarian cancer, and possibly cancers of the gastrointestinal tract and kidneys. Individuals particularly at risk include workers in industries such as mining, shipbuilding, and construction, as well as their families due to secondary exposure. Despite regulations introduced to limit asbestos use and mitigate risks, thousands of asbestos-related deaths continue to be reported annually. Awareness of the dangers of asbestos remains critical, especially for those undertaking home renovations where remnants of asbestos-containing materials may still be present.
Subject Terms
Asbestos and cancer
Asbestos refers to six naturally occurring fibrous silicate minerals: the serpentine mineral chrysotile and the amphibole minerals actinolite, amosite, anthophyllite, crocidolite, and tremolite. The fire-resistant properties of these minerals have been known since ancient times. Their fibers are released into the environment from both natural and human sources. They are found in indoor and outdoor air, soil, drinking water, food, and even some medicines and personal care products. Although there are a variety of forms of asbestos, some more associated with cancer than others, all forms of asbestos share a common characteristic: because asbestos consists of silica crystals, the fibers are inherently irritating to human tissue.
Quick Facts
ROC status: Known human carcinogen since 1980
Also known as: Chrysotile, actinolite, amosite, anthophyllite, crocidolite, tremolite
Related cancers: Pleural and peritoneal mesothelioma, laryngeal cancer, ovarian cancer, skin cancers, possibly kidney cancer, gastrointestinal cancers, and others
Exposure routes: Inhalation and ingestion
Where found: Materials for roofing, thermal and electrical insulation, cement pipe and sheets, flooring, gaskets, friction materials, coatings, plastics, textiles, paper, and other products
At risk: Workers in asbestos mining and milling, shipyards, building demolition, insulation, brake repair, and asbestos abatement, and their families
Etiology and Symptoms of Associated Cancers
Several asbestos-related conditions are nonmalignant. These include asbestos warts (callus-like growths that form when asbestos fibers become embedded in the skin), asbestosis, pleural plaques, pleural thickening, and pleural effusions (the collection of fluid around the lung a few years after asbestos exposure).
Inhaled or ingested asbestos fibers lead to the two most serious asbestos-related disorders: the noncancerous asbestosis, in which scarred and increasingly stiff lung tissue progressively reduces breathing capacity, and the cancer known as mesothelioma. These diseases may take years or decades to develop, although there have been cases of adolescents developing mesothelioma within only a few months of initial asbestos exposure.
Malignant mesothelioma takes two main forms. In pleural mesothelioma, tumors form on the outer lining of the lungs. In peritoneal mesothelioma, tumors form on the peritoneum, the sac containing the abdominal organs. The rarer forms of malignant mesothelioma are pericardial mesotheliomas and mesotheliomas of the tunica vaginalis, affecting the heart and testicles, respectively.
Malignant mesothelioma has a low survival rate because it is rarely detected in its early stages. By the mid-to-late 2020s, it was only 7 to 24 percent after five years, according to the American Cancer Society (ACS). When localized, the survival rate was higher, with the average of all stages being around 12 percent. Thirty or more years can pass between first exposure to asbestos and a mesothelioma diagnosis. In the miod-2020s, the average age of mesothelioma patients was between sixty-seven and seventy-two years old.
Symptoms of malignant mesothelioma, including chest pain, cough, weight loss, and shortness of breath, are often attributed to more common diseases such as asthma. As the cancer spreads, lung capacity is diminished, and the patient eventually succumbs to the inability to take in sufficient oxygen, if not to the failure of other organs after the cancer metastasizes.
Asbestos exposure has also been associated with cancers of the ovaries, stomach, liver, and other organs. Researchers have observed digestive tract cancers in workers exposed to crocidolite, amosite, and chrysotile, although study results are inconsistent. An excess of laryngeal cancer has been reported in shipyard workers, chrysotile miners, insulation workers, and others exposed to asbestos. People living near asbestos factories or mines or living with asbestos workers have also developed mesothelioma. However, the evidence for an association between gastrointestinal cancer risk and exposure to asbestos in drinking water is mixed, with some studies suggesting a link and others finding none. Smokers who are also exposed to asbestos are at a synergistically (rather than additively) greater risk of developing lung cancer.
History
In the 1930s, researchers established that asbestos presented especially high risks of causing lung diseases in miners, shipyard workers, and others who either manufactured or worked with materials incorporating asbestos, such as insulation. It soon became evident that exposure to minute amounts of asbestos could lead to asbestos-related disorders. Miners’ spouses developed mesothelioma after being exposed to asbestos through doing laundry, for example, while children became victims through exposure to their parents’ work clothes in the home.
In the United States, asbestos was one of the first hazardous air pollutants regulated by the Clean Air Act of 1970. The first lawsuits resulting from occupational exposures began in the late 1960s and increased in 1973 when the Fifth Circuit Court of Appeals applied strict liability in Borel v. Fibreboard Paper Prods. Corp. In 1976, Congress passed the Toxic Substances Control Act, under which the US Environmental Protection Agency (EPA) imposed regulations regarding asbestos, including a requirement that asbestos abatement occur in schools. The International Labour Organization’s Asbestos Convention of 1986 mandated that national laws should “prescribe the measures to be taken for the prevention and control of, and protection of workers against, health hazards due to occupational exposure to asbestos.” Three years later, the EPA banned most all asbestos applications and mandated an eight-year phaseout of asbestos in consumer products. However, in 1991, a federal court overturned this ruling and limited the ban. More than three decades later, in 2024, the EPA banned importing and using the most common form, chrysotile, with phaseouts for the automotive parts and chlor-alkali industries. By then, asbestos exposure was still responsible for thousands of deaths a year in the US alone. Worldwide, asbestos-related deaths remained around 90,000 annually.
Despite those efforts, the widespread historical use of asbestos fibers in multiple applications means that exposure remains a concern in the twenty-first century. Although asbestos is no longer as widely used in industry, which has reduced exposure in the workplace, people still risk exposure when engaging in home improvement projects, such as ripping out old flooring or replacing ceiling tiles.
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