Millions in U.S. at Risk of Developing Malignant Mesothelioma

More than 20 million people in the United States are at risk of developing malignant mesothelioma due to asbestos exposure, according to researchers at the University of Hawaii Cancer Center.

In the March issue of the Journal of Cell Physiology, the University of Hawaii researchers estimate that malignant mesothelioma mortality rates will increase 5 to 10 percent per year in most industrialized countries until about 2020.

Approximately 2,500 to 3,000 people a year in the U.S. die of mesothelioma, an incurable cancer of the lining of the lung and abdomen associated with asbestos exposure. Asbestos, a mineral fiber, was widely used in many construction materials and types of insulation in the U.S. until the 1980s and is still present in many older houses, factories, power plants, ships, and automobiles. Asbestos is used in some products currently manufactured in the U.S. and imported into the country.

The researchers note that the incidence of malignant mesothelioma among men has continued to rise during the past 50 years, while the incidence among women has stayed largely unchanged. Men are more likely to be employed in hazardous occupations such as construction and demolition work, plumbing, auto repair and insulation where asbestos exposure is most likely.

The researchers estimate that 50 to 80 percent of cases of malignant pleural mesothelioma, a cancer of the lining of the lung, diagnosed in men are linked to asbestos exposure and 20 to 30 percent of cases in women.

Complicating the identification of asbestos exposure is the delayed development of mesothelioma. Symptoms of mesothelioma typically appear 20 to 50 years after exposure, making it difficult for many patients to recall when they may have inhaled asbestos fibers. Many workers may be unaware in fact that they breathed asbestos dust.

When a sufficient number of asbestos fibers lodge in the lungs, the fibers trigger a chronic inflammatory process and release pro-inflammatory molecules by cells in the lining of the lungs, an early step in the development of mesothelioma. Asbestos causes mutations in the mesothelial cells’ DNA, the genetic blueprint, eventually causing normal cells to mutate into malignant cells.

The researchers say that erionite is another potent cancer-causing mineral fiber, capable of causing pleural mesothelioma and peritoneal mesothelioma. Since erionite is considerably less widespread than asbestos, the number of cases of malignant mesothelioma associated with erionite is smaller.