What Is Asbestos? How Does It Form? Is It Linked to Earthquakes? Which Cancer Risks Does It Increase?

Asbestos is a naturally occurring mineral fiber that resists heat and chemicals, is nonabrasive and does not conduct electricity. It was therefore widely used throughout much of the 20th century in industries including construction and insulation, automotive brake and clutch parts, shipbuilding and electrical equipment.

However, research since the 1970s has revealed serious health risks. Asbestos fibers can spread easily through the air and, when inhaled, damage the lungs and cause diseases such as asbestosis, lung cancer and mesothelioma (cancer of the lung lining). Because of these risks, many countries have banned or restricted asbestos use.

What Is Asbestos?

Asbestos is a group of naturally occurring silicate minerals. Their fine, fibrous structures make them resistant to heat, abrasion and chemicals, nonflammable and electrically nonconductive. Asbestos is divided into two main categories: serpentinite and amphibolite.

• Serpentinite asbestos: Chrysotile, also called white asbestos, is the most widely used type and the only one in this category. Its flexible, soft fibers offer advantages in processing and use.
• Amphibolite asbestos: This category includes crocidolite (blue asbestos), amosite (brown asbestos), anthophyllite, tremolite and actinolite. These types have stiff, straight fibers and are less flexible.

How Does Asbestos Form, and Where Is It Found?

Asbestos is a group of silicate minerals occurring naturally in the Earth’s crust. Its formation is linked to igneous and metamorphic processes. Complex, long-term geological interactions produce the minerals’ characteristic fibrous structures.

• Igneous processes: Asbestos minerals can form as igneous rocks, including basic and ultrabasic igneous rocks such as basalt, cool and crystallize. Chrysotile asbestos formation is generally associated with igneous processes.
• Metamorphic processes: Asbestos minerals can also form during metamorphism of rocks that initially contained no asbestos. Under high pressure and temperature, these rocks undergo chemical and physical changes over geological time. These processes promote the formation of amphibole asbestos types.

Asbestos deposits occur in various regions worldwide. Mining was an important industry, particularly in countries such as Russia, China, Kazakhstan, Brazil and Canada. As its adverse health effects became understood and its use was banned or restricted, asbestos mining declined substantially.

Is There a Link Between Earthquakes and Asbestos Exposure?

Yes. There is a relationship between debris produced by major earthquakes and asbestos exposure. Collapsed structures, particularly older buildings containing asbestos materials, can release fibers into the air, increasing exposure risk for people nearby.

Some studies have examined asbestos exposure from post-earthquake rubble. For example, studies after the 2009 L’Aquila earthquake in Italy and the 2011 Christchurch earthquake in New Zealand showed that demolition and breakage of asbestos-containing building materials released fibers into the air, creating a potential health risk for nearby people.

Measures should be taken in such circumstances to minimize post-earthquake asbestos exposure. Proper rubble and debris management can help prevent environmental dispersal. Appropriate personal protective equipment and air-quality monitoring systems are also important in areas with an exposure risk.

Major-earthquake debris is therefore linked to asbestos exposure, and research provides important information for managing rubble and reducing exposure risks.

Which Cancer Risks Does Asbestos Exposure Increase?

Asbestos particularly increases the risk of mesothelioma (cancer of the lung lining), lung cancer and laryngeal (voice-box) cancer. Some studies also suggest that asbestos may cause soft-tissue and gastrointestinal cancers, particularly stomach and colorectal cancer. Asbestos-associated cancer risks can be presented as follows:

The risk increases in the table are based on a general assessment of asbestos-associated cancer types. They are not precise estimates: actual risk can vary with the level and duration of exposure and other risk factors.

Remember that cancer risk rises with longer and more intense asbestos exposure. Limiting exposure as much as possible and taking appropriate protective measures are important to reduce asbestos-associated cancer risk.

The relationship between asbestos exposure and mesothelioma is illustrated simply below:

How Many Years of Chronic Asbestos Exposure Significantly Increase Cancer Risk?

The time required for asbestos-associated cancers to develop is generally called the “latency period” and varies between individuals. It runs from asbestos exposure to the onset of cancer symptoms. Asbestos-associated cancers, particularly mesothelioma and lung cancer, generally have long latency periods.

Mesothelioma’s latency period is generally 20 to 50 years, although it may develop after as little as 15 or as long as 60 years. For lung cancer, the period is generally 15 to 35 years, but varies with the amount, duration and type of asbestos exposure and individual factors.

Exposure duration and intensity play important roles in increased cancer risk. Even brief, low-level exposure can increase risk, but the risk is higher with long-term, high-level exposure. Smoking also increases the likelihood that asbestos exposure will raise lung cancer risk.

Historical Studies of Mesothelioma and Asbestos Exposure

After years of research, speculation and debate, the world’s medical institutions definitively accepted two important facts about mesothelioma: its pleural origin and its definite association with asbestos exposure.

• The groundbreaking German study: In 1943, Dr. H.W. Wedler became the first to report a link between asbestosis and pleural cancer among German asbestos workers. Cancer was found in around 20% of the workers, with lung cancer more common than mesothelioma. Wedler’s work was well received in Germany, but the political climate led the rest of the world to ignore research from Nazi Germany.
• The South African study: Perhaps the most important study documenting the clear asbestos-cancer link was presented by medical researcher JC Wagner and Dr. Chris Sleggs. In their paper published in 1960 by the British Journal of Medicine, Sleggs and Wagner detailed 33 mesothelioma cases identified in northwestern South Africa, where crocidolite asbestos was mined.
• The American study: American physician Dr. Irving J. Selikoff presented his findings at the 1964 Biological Effects of Asbestos conference sponsored by the New York Academy of Sciences. For over a year, he examined more than 1000 workers from the Union Asbestos & Rubber Company plant in Patterson, New Jersey. Mortality among them was 25% higher than statistically expected. He found that workers had died from various causes, including asbestos, asbestos-related lung cancer and other lung, stomach and colorectal cancers.
• The British study: Another study by British physician Molly Newhouse found mesothelioma cases among people living near an asbestos factory in London who were not employed there. In 1968, the British Medical Journal stated that asbestos was the direct cause of most mesothelioma cases. Debate continued about which types of asbestos were more carcinogenic.

Which Noncancerous Diseases Are Linked to Increased Risk from Asbestos?

Asbestos exposure is known to cause health problems beyond cancer. Associated noncancerous diseases and conditions include:

• Asbestosis: A lung disease caused by inhaled asbestos fibers that makes lung tissue stiff. It can cause breathing problems, chest pain and permanent lung damage.
• Pleural plaques: Asbestos exposure can cause thickened areas in the lung lining (pleura). These are generally harmless but may reduce lung function and cause breathing difficulties.
• Pleural effusion: Asbestos exposure may increase the risk of pleural effusion, a buildup of fluid between the layers of the lung lining. This can cause symptoms such as pain and difficulty breathing.
• Cystic airways: Asbestos exposure is thought to contribute to cystic airway disease, characterized by abnormal airway widening and inflammation, which can cause respiratory problems.
• Obstructive lung disease: Asbestos exposure may increase the risk of obstructive lung diseases such as COPD (chronic obstructive pulmonary disease), characterized by narrowed airways and difficulty breathing.

These health problems generally result from high-level, long-term asbestos exposure. Restricting asbestos use and implementing appropriate occupational health and safety measures are important to reduce exposure risk and help prevent these diseases.