Mesothelioma Causes

The ingestion and inhalation of airborne asbestos fibers are the main causes of mesothelioma. Asbestos is the only known cause of the disease, which is a lethal form of cancer that attacks the mesothelium, a protective membrane that surrounds and blankets many organs within the body. Asbestos exposure on the job has been the primary cause of this disease, which has impacted tens of thousands of American workers whose careers spanned some portion of the twentieth century. Asbestos was a widely used component for thousands of industrial, construction and manufacturing purposes and products up until about 1980. In some nations it is still in use.

When asbestos products deteriorate they become friable, which means they are subject to crumbling – and giving off microscopic asbestos fibers. These fibers can be inadvertently inhaled or ingested without any sensation or knowledge. Once they are in the human body, they remain there as the body cannot use any of the natural processes to rid itself of them.

How Asbestos Fibers Cause Mesothelioma

The mesothelium lines the outer surface of the lungs, forms a sac around the heart, lines the walls of both the chest cavity and the abdominal cavity, and provides protection for several other internal organs. It is in this tissue that asbestos fibers embed themselves, eventually causing abnormal cells to develop and causing a number of other physical abnormalities.

There are three types of mesothelioma, each occurring in a different portion of the mesothelium:

Pleural Mesothelioma develops in two sections of the mesothelium: one membrane that lines the chest cavity wall and another that wraps around the lungs. Together these layers of tissue are known as the pleura. Asbestos fibers that are inhaled work their way through the lung itself into the outer lining of the lung, called the visceral pleura. They embed themselves there or in the parietal pleura, the membrane that lines the chest cavity. Pleural mesothelioma is by far the most common form of the disease, comprising over seventy percent of all mesothelioma cases.

Peritoneal Mesothelioma develops in the membrane lining the abdominal cavity wall. This form of the disease is found in fifteen to twenty percent of all mesothelioma cases. It is believed that the asbestos fibers work their way to the peritoneal mesothelium – called the peritoneum – through the lymph system. As the membrane thickens and, in many cases, generates formation of excessive fluid in the area, the abdomen swells and becomes painful. Peritoneal mesothelioma can lead to intestinal blockages and create problems with other organs in the area.

Pericardial Mesothelioma is the rarest form of the disease, occurring in less than five percent of all cases. It develops when asbestos fibers become lodged in the pericardium, that portion of the mesothelium that forms a sac around the heart. The symptoms for this form of the disease may include development of excessive fluid in the area, causing pressure on the heart. The pericardium may also develop fibrosis, thicken and harden, putting pressure on the heart that may require emergency surgery for relief.

Asbestos in the Workplace

Asbestos products were ubiquitous in manufacturing facilities of the mid 20th Century. Ships and shipyards in particular proved to be risky job locations for asbestos exposure, because asbestos insulation was used throughout the engine rooms and pipe systems of ships as well as on pumps and hydraulic systems of all sorts. Pulp and paper mills, steel mills, oil refineries, chemical plants, textile mills, auto plants – all of these and hundreds of other industries used asbestos products for many purposes. Workers in these and other locations would inhale asbestos fibers given off by worn asbestos products, or by working to replace asbestos insulation, siding, roofing or flooring after it had become worn – and often, deteriorated.

Although it has been proven that even the slightest amount of asbestos exposure can be harmful, most cases of mesothelioma have been seen in individuals who work closely with asbestos fibers on a daily basis. Individuals who work in the following industries are at the highest risk of developing mesothelioma:

  • Shipbuilding
  • Mining
  • Military
  • Construction
  • Demolition
  • Maritime
  • Railroad
  • Pipe fitting
  • Plumbing
  • Roofing
  • Welding
  • Automotive
  • Factory
  • Painting & Drywall
  • Heating and HVAC
  • Power Plants
  • Oil Industry

Asbestos Regulations in the Workplace

Because inhalation and ingestion of asbestos are the primary causes of mesothelioma, the Occupational Safety and Health Administration has set permissible exposure limits on the amount of asbestos that an employee can be exposed to in the workplace. Employee exposure to asbestos cannot exceed 0.1 fiber per cubic meter of space averaged over an eight hour work day or 1 fiber per cubic meter in any thirty minute period. Asbestos exposure on the job is heavily regulated, as is the demolition of old structures containing asbestos and removal of asbestos debris.

Some work environments are required to conduct daily monitoring of asbestos levels to prevent the causes of mesothelioma. All employers of individuals who handle asbestos are required to provide their employees with the following:

  • Protective gear
  • Adequate ventilation
  • Respiratory equipment
  • Showering facilities
  • Proper asbestos training

Even with these precautions, as many as 1.3 million construction workers alone are exposed to the causes of mesothelioma every year. Mesothelioma kills ten thousand people every year. At least two to three thousand people are diagnosed with mesothelioma annually.

Secondary Asbestos Exposure Can Cause Mesothelioma

Secondary exposure can contribute to the causes of mesothelioma when workers inadvertently carry asbestos fibers home on their person and family members are exposed. There have been thousands of cases of mesothelioma developed by family members of workers who were exposed to asbestos on a job site. Asbestos miners, construction workers, heating system installers, drywall installers, cement workers, and railroad workers all would come home with dust on their clothing containing asbestos fibers. Wives and sometimes even children who inhaled fibers from this dust developed mesothelioma decades later.


  1. Toxicological Profile for Asbestos U.S. DSS Agency for Toxic Substances and Disease Registry 2001 pp. 62-76
  2. OSHA Asbestos Standards, Occupational Health and Safety Administration,
  3. Better Protection Against Asbestos in the Workplace U.S. Dept. of Labor OSHA Factsheet,

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