Mesothelioma is a rare type of cancer that affects the protective lining around the chest, abdominal or cardiac cavity. Mesothelioma usually results from exposure to asbestos. Asbestos is a natural mineral that has been used in many products. It is a known human carcinogen.

Asbestos becomes extremely dangerous when its microscopic fibers are released into the air. Asbestos fibers are invisible to the naked eye, so most people are unaware they are inhaling or ingesting these particles.

Many construction workers, shipyard workers, miners, textile workers, factory workers, auto mechanics, first responders and others may have been exposed to asbestos over the years, through direct or second-hand exposure. Veterans are one of the most at-risk groups.

The following are some surprising facts about mesothelioma.

1. The primary cause of mesothelioma is inhalation of airborne asbestos particles.

The primary cause of mesothelioma is inhalation or ingestion of asbestos particles that have become airborne. An estimated 2-10 percent of individuals who are heavily exposed to asbestos particles for long periods of time will be diagnosed with pleural mesothelioma.

2. An estimated 11 million people were exposed to asbestos between 1940 and 1978.

The National Institutes of Health estimates that during the height of asbestos mining and use, which occurred between 1940 and 1978, close to 11 million people were exposed to asbestos fibers.

3. The majority of mesothelioma patients go without symptoms for 25-50 years after being exposed to asbestos.

Most mesothelioma patients experience a significant gap between the date of exposure and the onset of symptoms. The mean latency period for men is 47.9 years and 53.3 years for women. Doctors can have difficultly diagnosing mesothelioma due to the fact that early symptoms tend to be either quite mild or completely nonexistent.

4. Approximately 2,000-3,000 new mesothelioma cases are diagnosed each year.

Due to the long latency period and continued exposure to materials containing asbestos, approximately 2,000-3,000 new mesothelioma cases are diagnosed each year.

5. Men are four times more likely than women to be diagnosed with mesothelioma.

Men were more likely to be exposed to asbestos in the jobs and industries in which they traditionally worked. As a result, men are about 4.6 times more likely than women to be diagnosed with mesothelioma.

6. Dose and duration are not the only factors affecting the risk of developing an asbestos-related disease.

There is no question that the amount of asbestos an individual is exposed to and the length of time he or she is exposed are both key factors affecting the risk of that individual developing an asbestos-related disease. These are not the only factors, however. The source of the exposure, as well as the size, shape and chemical makeup of the fiber itself may also affect a person s risk.

If an individual smokes or already has a pre-existing lung condition, this can also increase his or her chances of being diagnosed with this type of cancer. Race and age may also play a role. The majority of patients who receive a mesothelioma diagnosis are white and over the age of 60.

7. Mesothelioma most commonly occurs in the pleura.

While mesothelioma can affect the lining of the chest, lungs, abdomen or heart, it most commonly occurs in the pleura the membranes surrounding and enveloping the lungs. Between 70 to 90 percent of all mesothelioma cases occur in the pleura, 10 to 30 percent occur in the peritoneum (lining of the abdominal cavity) and 1 percent occur in the pericardium (membrane surrounding the heart).

8. Symptoms of mesothelioma vary depending on where the cancer is located.

Patients with pleural mesothelioma may experience symptoms such as:

Peritoneal mesothelioma affects the lining of the abdomen or stomach (peritoneum). Symptoms for this type of mesothelioma can be similar to those for pleural mesothelioma, however can also include:

Pericardial mesothelioma affects the membrane surrounding the heart. Symptoms for this type of cancer can also be similar to the other types of mesothelioma, and may also include:

9. There is hope for mesothelioma patients.

The current five-year survival rate for mesothelioma patients is around 30 percent. Fortunately there is hope for longer-term survival in those diagnosed with mesothelioma. Surgery, chemotherapy, radiation therapy and clinical trials are some of the treatments available to people fighting this type of cancer.

10. More than half of all mesothelioma patients are included in clinical trials.

Although there is no definitive cure for mesothelioma at this time, more than 175 clinical trials have been conducted since 2011. At least half of the patients diagnosed with mesothelioma will be involved in a clinical trial at some point in their lives.