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Asbestos: the only known cause of mesothelioma

Asbestos use dramatically declined in the 1980s as awareness that exposure to asbestos could cause mesothelioma exploded.

Indeed, asbestos exposure is the only proven cause of mesothelioma. In eight out of 10 cases of mesothelioma, this cancer can be reliably traced back to asbestos.

That means if someone has mesothelioma, the person almost surely fell ill with this cancer as a result of coming into contact with asbestos sometime much earlier in life. It typically takes 10 to 50 years or longer for mesothelioma to show up after exposure to asbestos. In other words, a person diagnosed with mesothelioma this year was possibly exposed to asbestos at one or more points during the 1950s, 1960s, or 1970s.

Medical scientists are generally agreed that all it takes is a single asbestos exposure to set in motion the biological changes necessary to convert healthy cells into mesothelioma cells.

During the middle of the 20th Century, many products for consumer, industrial, and military use were made with asbestos.

There were several reasons for this. First, as mentioned, asbestos was a common mineral. Being common, it was plentiful and easy to mine, which made it cheap to acquire.

Second, asbestos added to clothing, building materials, and other products rendered them fireproof.

Third, asbestos prevented the intensely hot temperatures of ovens, steam pipes, water heaters, car brakes, and other heat-generating or heat-carrying products from damaging anything (or burning anyone) in too close proximity.

Fourth, asbestos increased the strength of bricks, concrete, and mortar while at the same time reducing their weight.

A short and by no means complete list of goods in which asbestos was used includes appliances, chairs, sofas, bedding, blow dryers, power tools, paints and sealants, electrical wiring, ceiling and floor tiles, mastics and grout, attic insulation, air ducts, personal protective equipment, generators, forges, printing presses, assembly line equipment, and much more.

Seagoing vessels—especially warships belonging to the U.S. Navy but also freighters operated by the merchant marine—were laden with asbestos above and below deck. The heaviest concentrations of the mineral were found in the engine room and the galley. Asbestos also was liberally employed in gun turrets, ships’ magazines, and ammunition conveyor belts.

Viewed under the microscope, a specimen of asbestos can be seen to consist of long fibers. These fibers are surprisingly fragile. It doesn’t take much force to break them apart.

That’s the Achille’s heal of asbestos—its friability (things that are friable are easy to crumble).

When asbestos is rubbed or merely even bumped, tiny bits of it break away. These bits are so small that they are difficult to see. They also are so light in weight that they can float in the air the way that dust particles do.

The danger for people is that a product containing asbestos will be subjected to sufficiently rough handling that some of the fibers will separate and find their way into the air. Once airborne, it is possible that a person might unknowingly inhale them or, alternatively, swallow them.

Inhaled asbestos fibers enter the lungs and remain trapped there. Some of the trapped asbestos may work its way from the lungs into that organ’s surrounding lining—the thin layer of protective tissue known as the pleura.

By mechanisms not yet fully understood, asbestos that lodges within in the pleura causes some of the cells making up the pleura to become inflamed. The inflammation produces plaque, which is a type of scarring. The plaque, in turn, triggers changes to the affected cells’ DNA code.

The DNA code contains instructions that tell the cells how to perform the many different internal functions necessary to be healthy and fully operational. When the DNA code is altered, malfunctions begin to occur. One of these alterations results in the conversion of healthy cells into cancerous ones.

The cancer that forms on the pleura is known as malignant pleural mesothelioma. The cancer that forms on the peritoneum (the pleura-like lining surrounding the organs of the abdomen) is called peritoneal mesothelioma.

Peritoneal mesothelioma is caused by asbestos fibers that are swallowed. These find their way into the intestines and from there can affect the thin tissue lining between the intestines and the abdominal cavity’s inner wall.

It’s unusual but it does happen that inhaled asbestos fibers can mutate the cells of the protective lining wrapped around the heart. The name of this lining is the pericardium. The cancer that forms on the pericardium is called malignant pericardial mesothelioma.

Most people exposed to asbestos do not develop mesothelioma. It is only a relative few who do (which is why there are each year now only about 3,000 new cases of mesothelioma in the U.S., rather than the millions that might be expected in light of how broadly asbestos was once used).

According to the most reliable scientific evidence, whether a person develops mesothelioma following exposure to asbestos depends on several factors.

The first such factor is the amount of asbestos to which the person was exposed. Generally, the more exposure, the greater the potential for mesothelioma (although, as mentioned earlier, only a single, small exposure is enough to cause the cancer in some individuals.)

Keep in mind that asbestos was used in a great many products during the middle of the last century, so a person who is today 80 years old could possibly have been exposed to asbestos in innumerable ways countless times.

Another risk factor for mesothelioma is occupation. People who held jobs in steelmaking, construction, automotive repair, manufacturing, newspaper printing, and military maritime service routinely encountered asbestos in the course of their daily work.

One additional risk factor is genetics. There are some people who have a specific inherited gene defect that makes them particularly vulnerable to the effects of asbestos exposure.

Other risk factors are identified in this free guide available now for downloading.