Among other jobs, sheet metal workers install the aluminum ductwork in the crawlspaces of commercial and residential buildings – a prime location for ACMs, or Asbestos Containing Materials.
Construction Trades at Risk
Although virtually everyone on the planet has been exposed to asbestos at some point in their lives, those in the construction trades – including sheet metal workers – are at an elevated risk of asbestos related diseases because their jobs frequently take them into enclosed, poorly ventilated areas were ACMs are present.
A study conducted by prominent asbestos disease researcher Dr. Irving Selikoff on over 1,300 sheet-metal workers from the U.S. and Canada showed that more than 50% had “chest x-ray abnormalities”. Pleural fibrosis, a precursor to full-blown asbestosis, was found in nearly half of those with such abnormalities. Not unexpectedly, the study found that such abnormalities were more marked the longer the subject had been at the job. The average period of time from initial exposure was 39.5 years; most of the subjects had been sheet metal workers for at least 35 years.
Another study funded by the Sheet Metal Occupational Health Institute examined over 18,000 individuals who had been employed for an average of 33 years. 21% of the subjects showed pleural scarring consistent with asbestos-related disease. Significantly, the prevalence of such disease was significantly lower for those who had started working after 1970; prevalence was highest for those who had gone to work prior to 1949.
A third study funded in part by the National Institute for Occupational Safety and Health tracked 122 sheet metal workers from the New England states over a ten-year period. Like the other studies, this one clearly showed a connection between asbestos exposure and loss of lung function. According to this particular study, a “history of shipyard work was a significant contributor” as well as “an important predictor of loss in pulmonary [lung] function even years after shipyard exposure has ceased”.
Asbestosis vs. Mesothelioma
Although both asbestosis and mesothelioma (A form of asbestos cancer) are caused by exposure to asbestos, have lengthy latency periods (time between exposure and appearance of symptoms) and are invariably fatal, they are quite different in how they affect the respiratory system.
Asbestosis is the result of scar tissue which builds up on the inside of the lungs. This is caused by antibodies, known as microphages,that attack asbestos fibers as if they were a virus or other organic pathogen. Because asbestos fibers are literally made of stone (and therefore inorganic), the microphages are destroyed in the attempt. Caustic enzymes similar to digestive acids are released, burning the inner tissues of the alveolar sacs. Over time, this reduces lung capacity; the victim essentially cannot take in enough air for the body’s cells and organs to function properly.
Malignant mesothelioma is a rare type of cancer that attacks the pleural lining, which is the outermost layer of the lungs, in its most common form – known as pleural mesothelioma. Once asbestos fibers are inhaled, they start to burrow through the lung from the inside out. Current medical research indicates that these fibers interact with the cells’ DNA structure, causing them to mutate and become malignant. The exact nature of this interaction is not yet known for certain. The end result is a tumor that spreads over the outer lung surfaces, and often spreads to other areas. The lungs are unable to expand, and the victim eventually dies of asphyxiation.