Causes of Mesothelioma: Asbestos Exposure

Causes of Mesothelioma: The Role of Asbestos Exposure

Exposure to asbestos is for sure the most important of the many causes of mesothelioma: it generates many grave health problems, especially regarding the respiratory system. However, this dangerous effect remained undiscovered for a long time, as asbestos was being widely used in various industries (Source).

It causes scarring of lungs, and the most dangerous disease caused due to asbestos exposure is mesothelioma. It is an aggressive form of cancer that is still not satisfactorily treated, thus leading to quick fatal outcomes for most people.

People of certain professions are at higher risk of developing mesothelioma or other diseases due to asbestos exposure. Construction workers, carpenters, plumbers, electricians, mechanics, insulators, workers in various factories, military personnel are all at higher risk of asbestos exposure.

Apart from construction workers, workers in shipyards, power plants, steel mills are also known to be at higher risk. In countries like the United States, where asbestos is not banned, military personnel form the big part of the population that has been exposed to asbestos. Especially naval veterans are considered to be at the highest risk.

Since 2018 the United States increased its imports of asbestos from Russia and Kazakhstan and the Government declared that asbestos is “100 percent safe, once applied”.

Historical Perspectives of Asbestos

Asbestos is a mineral abundant in many places and is one of the six silicate minerals. That is a compound of one of the most common elements called silicon. Crocidolite (blue colored), amosite (brown colored), and chrysotile (white-colored) are the three most commonly used varieties of asbestos in the United States. Out of these three, chrysotile was present in more than 90% of cases in the 20th century, and crocidolite is the most toxic of them.

A huge population worldwide continued to be exposed to asbestos until the end of the 20th century, when the dangers of such exposure were well recognized, and it was regarded as the most important among the causes of mesothelioma. The industrial revolution of the 19th and 20th century along with the boom in the construction industry and rising population lead to an increased number of people being exposed to asbestos. By mid-20th-century risks to such exposure were well studied, and thus started with the downfall of exposure.

By the early 21st century, most of the countries decided to stop producing asbestos, and even going for a complete ban on its use. A notable exception is the United States.

Widespread use of asbestos was fueled mainly due to its strength, fire-resistance, and insulating properties.

Today most of the countries have banned its use and production, but not countries like China and Russia, which are now among the leading producers and users too. As of 2020 these countries did not recognize the exposure to asbestos as the most important of the causes of mesothelioma.

In the United States mining of asbestos has stopped only in 2018, several years ago, although once the country used to be a leader in producing asbestos and related products. However, the United States continues to import asbestos due to industrial requirements.

However, the use of asbestos is much older than most would have imagined. It was a material well known for its various properties in olden times, with one of the earliest uses mentioned 4500 years ago where of course, it was not known that the manipulation of asbestos, was one of the causes of mesothelioma.

For a few millennia asbestos did not have much practical use, except for some anecdotal applications like its usage in making fire-safe tablecloth that could amaze people of earlier ages.

Asbestos gained its importance only in the nineteenth century, with the industrial revolution. In those times, it was the only known material to humans for its excellent insulation and fire resistance qualities.

It was found widespread use in construction, factories, various industries, even in some type of clothing. For more than a century, it remained a material of choice in many ways. With an understanding of health risks posed by it, by the mid of the 20th century, it fell out of favor.

By the early 21st century, it became banned material in most developed nations. Despite being acknowledged as one of the causes of mesothelioma, it is still not banned in the United States.

Asbestos is nevertheless, still present in many old constructions. Thus continuing to pose health risks. Thanks to bans, the peak of asbestos exposure has already happened, and we are already witnessing a sharp fall. We are on the verge of seeing the decline in the diseases caused due to such unintentional exposure.

Exposure To Asbestos and The Causes Of Mesothelioma

No doubt that exposure to asbestos is a 100% preventable health issue. Thus by preventing the use of asbestos, as one of the causes of mesothelioma, we can avoid the disease related to it.

Some level of asbestos has happened in all population groups, as most have inhaled some quantity in their lifetime. It continues to occur to date due to the presence in the environment. None of the amount inhaled has been demonstrated to be safe, and long-term exposure sharply increases the risk of developing cancer. Exposure to asbestos is generally due to the inhalation of microscopic fibers.

Exposure to asbestos can happen at home, at work. Asbestos exposure is quite common during the repair or renovation of older buildings in which asbestos has already been used in large quantities. Some industries continue to use materials that may have traces of asbestos, an example being sandblasting.

Particles of asbestos after the demolition of old buildings or renovation work may remain suspended in the air for hours after the work, thus posing a health risk to a broader population which may not be even aware of such danger and do not even know that is one of the causes of mesothelioma unless they are frequent readers of our blog.

Which Groups Are At Higher Risk Of Asbestos Exposure Related Diseases?

Before its ban in most of the industries by the early 21st century, asbestos was widely used in various industries. Some professions were at higher risk.

Military Veterans

Asbestos has been used in making various military equipment until the late 1990s. Especially those who served until the 1970s has the most significant chances of being exposed to it. Until the 1970s asbestos was almost considered as a wonder material, that is why veterans make up nearly 30% of all cases of mesothelioma.

Those who served in naval ships were at the most significant risk of exposure, where it was used as insulation, in air-conditioning units, pump valves to turbine engines. Asbestos was also used in various army transport equipment, and even in equipment for the air force. The causes of mesothelioma for these veterans is, of course, the exposure to asbestos in vessels inside naval bases.

United States veterans, if proven by a specialist to have suffered from asbestos exposure related, disease can qualify for monthly disability compensation.

High-Risk Jobs

Despite the fact that the use of asbestos has been banned in many industries, specific jobs may still pose a higher risk to exposure like those working in the construction industry, shipyards, chemical industry, power plants, and oil refineries.

September Eleven Attack

It resulted in the release of around 2000 tons of asbestos. Those who worked to clean rubble, or living in the areas nearby got exposed to it. Studies have already demonstrated a higher prevalence of specific asbestos-related health problems in them. In these proven cases, the causes of mesothelioma are related to the exposure to asbestos released after the attack.

Products Containing Asbestos Not Banned In The United States

Due to some of the unique physical properties of asbestos, it remains irreplaceable in specific industries and products:

  • Corrugated and flat cement sheets
  • Specific clothing
  • Pipeline wrap
  • Roof insulation/asbestos-containing felt
  • Vinyl floor tiles
  • Other cement products like cement stones, sand or pipes
  • Clutch facing
  • Components of automatic transmission
  • Certain friction materials
  • Disk and drum brakes
  • Automobile gaskets
  • Roof and non-roof coatings

Many asbestos products are not more produced in the United States, but are still commonly found and thus posing health hazards:

  • Heating vessels and boilers
  • Tubes for electrical wires
  • Containers for corrosive chemicals
  • Components of electrical motors
  • Paddings for heat and fire protection
  • Laboratory furniture
  • Paper products
  • Sealants and coatings
  • Textiles including curtains
src=”https://imedicalsociety.org/wp-content/uploads/2020/02/Brake-linings-300×200-1.png” class=”alignnone size-full wp-image-1987″ /> ASBESTOS CURRENTLY PRESENT IN BRAKE LININGS IS ONE OF THE CAUSES OF MESOTHELIOMA. THESE LININGS ARE NOT BANNED IN THE UNITED STATES.

Routes of Asbestos Exposure

The respiratory route is the primary route of exposure to asbestos due to airborne minute particles of that material, other routes being oral ingestion and dermal.

Exposure due to inhalation of asbestos occurs in many situations like:

  • Working with asbestos-containing materials
  • Working near the people using asbestos
  • From the asbestos workers’ clothing, skin, and hair. For example, the causes of mesothelioma in women are related to washing the clothes of workers that had particles of asbestos.
  • Living near the mining areas.
  • In some areas naturally occurring asbestos may be exposed due to erosion, construction, landscaping or other human activities.

Ingestion is less frequent than inhalation, it happened mostly due to ingestion of asbestos due to mucociliary clearance from the respiratory tract, to less extent due to drinking of contaminated water (e.g., cement pipe), or even due to swimming in contaminated water, however, the latter is not frequent as one of the causes of mesothelioma.

Skin contact is neither the conventional route nor does it pose many health problems, sometimes asbestos fiber may get lodged in the skin thus causing a corn or small inflammation, but we can discard it as one of the most relevant causes of mesothelioma.

Causes Of Mesothelioma And The Methodologies For Detecting Asbestos Related Diseases

People who have worked in an industry related to asbestos, or exposed to it in other ways must always inform the doctor, especially if they have respiratory issues. Identifying asbestos-related diseases are a challenge as they may occur decades after the primary exposure. Early diagnosis is very important in these cases as these patients were exposed to agents regarded as the main causes of mesothelioma. Some of the symptoms of asbestos-related diseases are:

  • Hoarseness, wheezing, or shortness of breath.
  • Cough that keeps getting worse over time.
  • Blood in sputum.
  • Chest pain or feeling of heaviness.
  • Difficulty in swallowing.
  • Enlargement of neck or face.
  • Loss of weight and appetite.
  • Chronic fatigue.

A chest x-ray is often used to visualize the changes in the respiratory system. Biopsy or histological examination is gold-standard in the diagnosis of many of the asbestos-related diseases.

Health Risks of Asbestos Exposure

There is a reason why even a small amount of asbestos exposure is so dangerous. Once the fibers of asbestos have been inhaled, they remain in our body for the whole life, causing a chain of reactions of inflammation, that may cause cancer in the long term.

Asbestos does not cause only cancer or is one of the causes of mesothelioma, it generates a whole range of pulmonary diseases. Damage to other organs is poorly understood.

It is estimated that in the United States in 2020, around 200,000 people are living with asbestos exposure. Below is the list of some of the health risks due to such exposure.

Mesothelioma: One of the rare forms of cancer caused due to exposure to asbestos, that as we mentioned many times is considered the main or one of the main causes of mesothelioma. It is one of the most difficult to treat cancers, with poor prognosis in most cases. It mostly occurs in pleura, followed by the abdominal cavity. It is a cancer of thin serous lining covering internal organs.

Asbestosis: Inflammatory disease of lungs, that results in compromised elasticity thus leading to severe shortness of breath, and increasing the risk of other health issues.

Pleural plaques: Thickening of serous tissue covering the lungs. It typically becomes visible only after a couple of decades after the initial exposure.

COPD: Chronic Obstructive Pulmonary Disease (COPD), although not directly caused by asbestos exposure, surely a person who has been exposed to asbestos is at much higher risk.

Lung Cancer: Apart from mesothelioma which is a cancer of lung lining, asbestos exposure is also related to a higher incidence of lung cancer, in fact, around 4% of all cases of lung cancer are due to asbestos exposure.

How Asbestos Causes Mesothelioma

Because of the high association between the two, and the aggressive nature of mesothelioma, it is a topic that requires further discussion.

Once the asbestos has been inhaled, most of it is cleared due to mucociliary clearance. Nonetheless, small quantities of it reach the lungs and penetrate into the pleural space.

This pleural space is a small space between the thoracic wall and lungs, where it interacts with mesothelial and immune cells, causing inflammatory response and cycle of damage and repair. It is this cycle that in the long term somehow through poorly understood mechanisms leads to the formation of cancer.

Why mesothelial cells? Well, although asbestos is toxic for any type of cells in the lungs, it seems that mesothelial cells are most susceptible to its aforementioned toxic effect. This can explain why it is one of the causes of mesothelioma, and why it is not the cause of other conditions.

There have been several explanations of what causes cancer after asbestos exposure and which are all the possible causes of mesothelioma; no single mechanism is completely self-explanatory; it is entirely possible that cancer is caused due to several mechanisms working together.

Thus, when asbestos fibers are inhaled they are eaten up by immune cells called macrophages, but these cells are not able to digest it, and finally, they disintegrate and release a high amount of inflammatory mediators and reactive oxygen species.

Mesothelial cells are especially sensitive to asbestos, with it being easily engulfed by them. It is quite possible that asbestos interferes with cellular functioning and causes mutations in mesothelial cells, with some of these mutations leading to cancer.

Asbestos fibers also participate in the chemical reaction with complex cellular proteins, forming toxic compounds that are carcinogenic.

And finally, All the above three mechanisms, that are a defect of mesothelial cells, lesions of macrophages and formation of toxic compounds lead to cells releasing inflammatory factors, growth factors, and tumor-forming factors.

Other Types of Cancers

Asbestos is not only about mesothelioma or lung disorders. It is thought that asbestos exposure may lead to ovary cancer, cancer of voice box, cancer to stomach, rectum and much more.

Smoking and Asbestos Exposure

There is substantial scientific evidence that those who smoke and are also exposed to asbestos are at much higher risk of developing cancer, as compared to either asbestos exposure or only smoking. Further research has demonstrated that those who quit smoking can decrease their risk of developing cancer after asbestos exposure. Although smoking does not appear to increase the risk of developing mesothelioma, and it is not identified as one of the causes of mesothelioma, it is strongly recommended that those exposed to asbestos should quit smoking.

Asbestos In a Nutshell

  • It is incredible material– that is why it found such extensive use in various industries. It is an excellent electrical insulator, heat resistance, resistance to chemical corrosions, have exceptional tensile strength. It can be woven into the fabric, added to cement, plastics and much more.
  • It is still in use– although banned for use by most industries, due to its unusual properties, it is still used in specific industries.
  • It remains in many buildings- it was extensively used in the construction for sealing, insulating and much more.
  • It is difficult to get rid of by the body- once, inside the body, it cannot be digested or destroyed or removed by our body. Thus a person may get cancer even after a couple of decades of the initial incorporation.
  • It is still widely mined- although its mining has stopped in the US, it is still being imported for industrial use. The industry is failing to replace it with other materials due to its particular properties not found in any other material.
  • It can cause a vast number of diseases- it not only causes cancer of many organs but may also cause other diseases of the respiratory system.
  • It is one of the causes of mesothelioma– for all the reasons explained in this article.

What Have Expert Agencies To Say?

There are several national and international agencies that study the data and provide recommendations regarding the health risk posed by a specific substance and the study of the causes of mesothelioma.

International Agency for Research on Cancer (IARC)– and organization that is part of WHO, clearly states that asbestos is a risk factor for mesothelioma, lung cancer, voice box cancer, ovary cancer, and other respiratory disorders.

National Toxicology Program (NTP), USA– basis its recommendations on information provided by FDA, CDC, and NIH. It also firmly states asbestos to be cancerous.

US Environmental Protection Agency (EPA)- also recommended stopping using asbestos in any industry due to health risks, including cancer-causing properties. However, in 2017 it changed its position: there is no ban to asbestos and is not proved as one of the causes of mesothelioma. The EPA assured in 2018 that there will be no ban on asbestos and allowed imports from Russia after asbestos was banned in Brazil (1).

Regulation Of Asbestos Levels

Occupational standards

  • Workers should be trained and provided personal protective equipment
  • Workers to be made aware of the health risks of asbestos exposure and that is one of the causes of mesothelioma
  • Inform workers about how smoking increases the risk of lung cancer after exposure

Those who have been exposed to asbestos must undergo regular medical surveillance:

  • Periodic physical examination
  • Chest imaging (x-ray)
  • Test of lung function through spirometry
  • Standard questionnaire.


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