Mesothelioma risk factors: asbestos and who is at risk

What mesothelioma is

Mesothelioma, also called malignant mesothelioma, is a cancer that forms in the thin layer of tissue that covers organs in the chest or abdomen. NCI says it may be found in the pleura (lining the chest and covering the lungs), the peritoneum (lining the abdomen) or the pericardium (around the heart). It may also form in the heart or testicles, but this is rare (NCI).

MedlinePlus says malignant mesothelioma is rare but serious, and it is often found when it is advanced, which makes it harder to treat (MedlinePlus).

Asbestos: the main risk factor

NCI says being exposed to asbestos can increase the risk of mesothelioma. Most people with mesothelioma have worked or lived in places where they inhaled or swallowed asbestos, which has been used in the building and textile industries (NCI). The NCI asbestos fact sheet adds that most mesotheliomas are thought to be due to asbestos exposure (NCI).

Asbestos is the name for six natural minerals made of fibers that resist heat, fire and chemicals. When products containing asbestos are disturbed, tiny fibers are released into the air; once breathed in, they can stay trapped in the lungs for a long time (NCI).

Who has been exposed

Low levels of asbestos are in the air, water and soil, and NCI says most people do not become ill from that exposure. People who become ill are usually those exposed on a regular basis, most often in a job where they work directly with the material or through substantial environmental contact (NCI). NCI names these groups (NCI):

• Shipbuilding trades, asbestos mining and milling, and making asbestos textiles and other asbestos products.
• Insulation work in the construction and building trades.
• Demolition workers, drywall removers, asbestos removal workers, firefighters and automobile workers.
• People involved in the rescue, recovery and cleanup at the World Trade Center site after September 11, 2001.

Because of regulations and better work practices, NCI says workers today without past exposure are likely to face smaller risks than workers in the past (NCI).

Family members and neighbors

Living with a person who works near asbestos is also a risk factor for mesothelioma (NCI). NCI says this risk is thought to come from fibers brought home on the shoes, clothing, skin and hair of workers. Mesothelioma has also been seen in people without job exposure who live close to asbestos mines (NCI).

Other factors that affect the risk

NCI lists several factors that help decide how asbestos exposure affects a person (NCI):

• Dose: how much asbestos a person was exposed to.
• Duration: how long the exposure lasted.
• The fibers: their size, shape and chemical makeup. Several studies suggest amphibole forms may be more harmful than chrysotile, particularly for mesothelioma, because they tend to stay in the lungs longer.
• Source of the exposure.
• Individual factors such as smoking and pre-existing lung disease.
• Genetic factors such as an inherited (germline) mutation in the BAP1 gene.

Health risks rise with heavier and longer exposure, but NCI notes that asbestos-related diseases have been found in people with only brief exposures (NCI).

Not every person with one or more of these risk factors will develop mesothelioma, and it can develop in some people who don't have any known risk factors (NCI).

What about smoking?

NCI says smoking combined with asbestos exposure does not appear to increase the risk of mesothelioma. It does raise the risk of lung cancer: in smokers exposed to asbestos, that risk is greater than the two risks added together. NCI says anyone who was exposed to asbestos on the job, or suspects they were, should not smoke (NCI). See our lung cancer risk factors guide.

Why it shows up years later

After asbestos exposure, it usually takes a long time for mesothelioma to form (NCI) (MedlinePlus). NCI says it can take from 10 to 40 years or more for symptoms of an asbestos-related condition to appear (NCI). That is why an old job, or a family member's old job, still matters when you talk to a doctor.

Symptoms to check with a doctor

NCI says signs and symptoms may be caused by fluid that collects in the chest or abdomen, by mesothelioma, or by other conditions. Check with your doctor if you have any of these (NCI):

• trouble breathing or a cough
• pain under the rib cage
• pain, swelling or lumps in the abdomen
• constipation
• problems with blood clots
• weight loss for no known reason
• fatigue (feeling very tired)

MedlinePlus notes that it is sometimes hard to tell mesothelioma from lung cancer. A health care provider will likely use a physical exam, imaging tests and a biopsy to find out (MedlinePlus).

Lowering exposure

NCI says workers should use all protective equipment their employers provide and follow recommended safety procedures, including properly fitted NIOSH-approved respirators when required. Workers worried about asbestos at work can talk with coworkers, their health and safety representative and their employer, and OSHA can give more information or inspect if needed (NCI). Federal rules also aim to keep fibers from going home: some employees may need to shower and change before leaving work, store street clothes separately, or wash work clothes apart from other laundry (NCI).

Common questions

Can a short exposure to asbestos cause mesothelioma?

The risk rises with heavier and longer exposure, but NCI says asbestos-related diseases have been found in people with only brief exposures (NCI).

Is there a test that shows how much asbestos I breathed in?

No. A lung biopsy is the most reliable test to confirm exposure, but NCI says such tests cannot show how much asbestos a person was exposed to or whether disease will develop (NCI).

Can you get mesothelioma without asbestos exposure?

Yes. NCI says it can develop in some people who don't have any known risk factors (NCI).