A new study by Duke University, in conjunction with the University of Nevada (UNR) and the University of North Carolina, shows that former North Carolina workers employed in asbestos-textile plants have a definitively higher rate of asbestos-related diseases than the population at large.
The study, headed by Dana Loomis, Interim Director, UNR's School of Community Health Sciences, examined 5,770 employees who worked at least one day between January 1, 1950 and December 31, 1973.
The results, which showed that the mortality rate was significantly higher for all causes (1.47 as compared to a value of 1.00 for the general population), also showed that deaths from lung cancer ranked at 1.96 (as compared to a value of 1.00).
The rate of deaths from pleural cancer (also called mesothelioma) was also elevated, as was pneumonoconiosis, with risks for other types of lung cancers and asbestosis rising with cumulative asbestos fiber exposures.
The pleura are the membranes that line the inside of the chest cavity and surround the lungs, enabling the lungs to expand to the appropriate degree inside the diaphragm when people breathe. Pleural mesothelioma is a type of pleural cancer caused primarily by asbestos fibers, and is the most common type of mesothelioma.
Asbestos fibers, inhaled, result in irritation of the pleura, or mesothelial lining. Because the body has no way to expel the fibers, the persistent irritation leads to lesions, which in turn lead to cancer.
Pneumoconiosis, the second category of occupational lung diseases, is an interstitial disease, a classic example of which is pulmonary fibrosis. Interstitial diseases affect the walls of the air sacs inside the lungs, rather than the pleural lining over the lungs, and result in scarring. This, in turn, limits a lung's ability to expand properly. Medication can occasionally slow the progress of pneumoconiosis, but many individuals, once affected, never regain the full use of their lungs, and lung transplants are the only option.
Asbestosis is a breathing disorder specifically caused by inhaling asbestos fibers, and is usually a cumulative effect, arising after years of exposure. The fibers cause lung scarring, which can gradually restrict breathing to such an extent that patients are unable to walk more than a few feet without stopping, and require constant oxygen. The symptoms, which can range from mild to severe depending on exposure and a person's general stamina, commonly don't appear until years after exposure to asbestos fibers.
The Duke, UNR study demonstrated a statistical risk across the entire spectrum of 2 to 3 percent higher for each year asbestos fibers were inhaled - figures which were more consistent among white males than for any other group surveyed. The second at-risk category was white females, and both groups scored higher in the risk assessment categories than black males, presumably because the latter group saw fewer smokers and workers who occupied different regions of the asbestos textile plants, namely preparation and carding operations, where fibers were shorter than in the spinning and twisting sections where white males generally worked, according to transmission electron microscopy, or TEM, analyses.
U.S. Environmental Protection Agency regulations (limiting asbestos to 1 percent of product by weight or volume) have driven the asbestos textile industry overseas. This is good news for American workers, but not so good for workers in places like Korea and Egypt, for example.
Attempts by the United Nations to add asbestos to the list of hazardous substances already on the Rotterdam Convention have been consistently opposed by Canada, which is the world's largest supplier of chrysotile asbestos.