Some cancer risks drop after asbestos exposure ends

NEW YORK (Reuters Health) - The risk of lung cancer in people exposed to asbestos falls after exposure to the toxic substance ends, a new study in Italian asbestos cement workers shows.

And while the risk of mesothelioma in the pleura -- the tissue lining the lung surface and chest wall -- also declined after exposure ended, the workers' risk of mesothelioma in the peritoneum -- the tissue lining the abdominal cavity -- continued to climb, Dr. Corrado Magnani of the University of Eastern Piedmont in Novara, Italy, and colleagues found.

Magnani and associates followed 3,434 male and female workers in order to understand the long-term risks of asbestos-related disease. All were working at the plant in 1950 or had been hired between 1950 and 1986, when the plant halted production.

Both men and women in the group were at increased risk of dying from any cause, any type of cancer, lung cancer, and pleural and peritoneal mesothelioma, the researchers found.

Women were also at greater risk of ovarian and uterine cancer. But the risk of cancer of the larynx (voice box) or cancer of the digestive tract was not greater than would have been expected in the general population.

Overall, the researchers found, that over a 41-year period, there were 480 excess deaths due to cancers and to asbestositis -- a chronic inflammation of the lungs due to asbestos exposure.

The risk of pleural mesothelioma rose steadily with years of asbestos exposure, the researchers found, but began to decline 50 years after exposure had ended.

The risk of lung cancer was highest for men 30 to 39 years after the end of exposure, and for women in the 20 to 29 years after exposure ended, and then began to decline. But the risk for peritoneal mesothelioma continued to rise even 40 years after exposure had ended.

These findings, note Magnani and colleagues, suggest that there may be different mechanisms by which asbestos exposure causes mesothelioma in the pleura and the peritoneum.

SOURCE: Occupational and Environmental Medicine, March 2008.