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Richard Lemen, retired assistant U.S. Surgeon General, said that scientific evidence has shown that all forms of asbestos including chrysotile are associated with increased risk of lung cancer and mesothelioma, a cancer of the lining of the lung or abdomen.

In a short article in the journal Environmental Health Perspectives, Lemen said there is scientific debate about the potency of mineral fibers of various types and lengths. But the fundamental conclusion is that all forms of asbestos are carcinogenic to humans, Lemen said, citing the most recent 2009 evaluation by the International Agency for Research on Cancer.

Only scientists with asbestos industry bias make claims that chrysotile asbestos has not been conclusively linked to mesothelioma, Lemen said. Chrysotile accounts for nearly all asbestos fibers used today. The asbestos industry and countries that export asbestos such as Canada and Russia have vigorously resisted efforts to ban chrysotile.

The International Agency for Research on Cancer’s first evaluation on asbestos, published in 1977, stated that mesotheliomas of the lung and abdomen have been observed after worker exposure to crocidolite, amosite and chrysotile. The three mineral fibers are commonly known as blue asbestos, brown asbestos and white asbestos respectively.

Since then, Lemen said science has not changed its view that all forms of asbestos, including chrysotile, cause mesothelioma.

Malignant mesothelioma, a cancer closely associated with asbestos exposure, remains difficult to detect so researchers have been seeking new ways to help doctors identify the disease earlier and more accurately.

Japanese researchers, writing in the journal Modern Pathology, report that CD146, a protein molecule, may be a sensitive and reliable indicator of malignant pleural mesothelioma, a cancer of the lining of the lung. Once rare, the incidence of malignant mesothelioma has been increasing worldwide and is predicted to peak around 2020. More than 100,000 people die a year of mesothelioma and other asbestos-related diseases, according to the World Health Organization.

Malignant mesothelioma is resistant to conventional cancer treatment and patients typically survive 9 to 17 months after diagnosis. The poor prognosis is partly due to the fact that most cases of malignant mesothelioma are diagnosed only after the patient has an advanced stage of cancer.

The first symptoms that people with malignant pleural mesothelioma often experience are shortness of breath and/or chest pain due to excess fluid around the lungs. Doctors refer to this fluid as pleural effusions. But the symptoms often don’t appear for 30 years or more after asbestos exposure. In many cases, excess pleural fluid or hardened areas on the lining of the lung can be benign so doctors need a way to reliably distinguish between patients with malignant mesothelioma and those with non-cancerous reactions to asbestos. The researchers say analysis of chest fluid is important in patients with a history of asbestos exposure, even if they don’t show other symptoms.

The increased presence of CD146, a protein molecule, has been linked to the advanced stage of several types of malignant cancer including prostate cancer, ovarian cancer and malignant melanoma. But scientists had not previously examined the relation between CD146 and malignant mesothelioma.

For the study, the Japanese researchers examined a total of 51 cases including 23 patients with malignant pleural mesothelioma ranging in age from .44 to 92 years old, and 28 patients with excess fluid around the lung. Their research techniques involved a study of the chemical processes of immune reactions to mesothelioma at the cell level.

In the tissue samples they examined, the researchers noted that the presence of CD146 was much greater in patients with malignant mesothelioma than in patients with benign reactions involving the lining of the lung. It’s typically not present in normal mesothelial cells. Using CD146 as their indicator, the researchers were able to distinguish which patients had malignant mesothelioma in more than 90 percent of the cases they analyzed.

The researchers propose that CD146 is a reliable predictor for distinguishing malignant mesothelioma and benign mesothelial reactions.

A new book entitled “Breathing In America: Diseases, Progress and Hope” by the American Thoracic Society details the toll of occupational-related respiratory disease including mesothelioma—a cancer associated with breathing asbestos dust.

Asbestos exposure causes lung cancer and mesothelioma, a cancer of the lining of the lung or abdomen, as well as other diseases such as asbestosis, a chronic scarring of the lung. In New York and New Jersey in the 1970s, asbestosis could be seen in more than 70 percent of asbestos insulation workers who had worked in the industry for 20 years or longer, according to the report.

Asbestos disease most heavily affects those directly exposed to asbestos in the workplace. Among the occupations typically exposed to asbestos are miners, millers, shipyard workers, asbestos insulators, boilermakers, electricians, plumbers and carpenters. But asbestos disease can also affect families of workers who are indirectly exposed to asbestos dust brought home on the workers’ clothing.

The most common appearance of asbestos-related disease is in the pleura, the thin membrane that covers internal organs including the lungs. Areas of thickened fibrous tissue called pleural plaques may develop and plaques are often a precursor to development of mesothelioma. Excess fluid may also collect, causing shortness of breath and chest discomfort. The fluid —called pleural effusion—is produced apparently in response to the asbestos fibers causing irritation of the pleura.

Worldwide production of asbestos peaked in the 1970s, but miners in Canada, Russia and other countries still dig from the ground more than 2 million tons of asbestos a year. An estimated 125 million people are still exposed to asbestos in the workplace and more than 90,000 people die each year of malignant mesothelioma, lung cancer related to asbestos exposure and asbestosis.

The prognosis for people diagnosed with mesothelioma and lung cancer is bleak with fewer than a fifth of patients diagnosed with mesothelioma or lung cancer surviving more than five years. Research into innovative gene therapies aimed at suppressing tumor growth offer some hope.

Breathing in America was produced as part of the American Thoracic Society’s 2010 Year of the Lung campaign.