The only known cause of malignant mesothelioma is heavy or prolonged exposure to asbestos dust. Although work-related exposure is the most well known, it is actually only one of four ways that people come into contact with hazardous levels of airborne asbestos. These four common modes of exposure are:
Occupational Exposure
The exceptionally high rate of mesothelioma cases among workers in asbestos industries as compared to workers in other industries is well documented. Contrary to what many people assume, however, asbestos is not banned in the U.S. and is still present in an extremely wide variety of products. Manufacturing, installing or removing asbestos-containing products such as these carries the greatest risk for occupational asbestos dust exposure.
- Cement products
- Flooring
- Wallboard and patching compounds
- Insulation
- Friction products
- Adhesives
- (See epa.gov for a more detailed list.)
Before OSHA began regulating asbestos exposure in the 1970s, millions of workers suffered prolonged exposure to asbestos. Over the ensuing 30 years, these laws have been gradually strengthened and extended to workers in all industries. Sadly, however, the rules regulating workplace exposure to asbestos are not uniformly implemented or enforced, even today. This continues to leave workers in some industries at serious risk.
The percentage of exposed workers who will develop malignant mesothelioma is very small, but they still number between 2,000 and 3,000 new cases per year. Because the disease can take as long as 40 years to develop, experts expect no decrease in the number of cases over the next few decades.
Secondary Exposure
The dangers of asbestos are not limited to workers in asbestos-related industries. Family members living with asbestos workers are also exposed to hazardous levels of dust the worker brings home on clothes and other articles.
Similar to second-hand smoke, secondary exposure can be enough to induce disease. Several studies estimate that as many as one-quarter of mesothelioma cases are family members of asbestos workers.
Outdoor Environments
Another source of exposure unrelated to occupation is from high-levels of asbestos dust in the outdoor environment. This occurs near plants and industrial centers where asbestos products are used or manufactured, and in areas where naturally occurring asbestos is found in local rock formations.
In one California study, a database of nearly 3,000 mesothelioma deaths over a 9-year period was cross-referenced to known locations of naturally occurring asbestos deposits in Northern and Central California. After adjusting for sex, age and occupational risks, the researchers concluded the incidence of mesothelioma dropped 6% for every six miles farther away a person lived from natural asbestos formations.
Other studies show a similar correlation between increased risk of mesothelioma and living close to asbestos manufacturing facilities or mining operations. Some studies even substantiated higher risk in living on the predominantly downwind side of the asbestos source.
Indoor Environments
Before the Environmental Protection Agency (EPA) first regulated asbestos in 1971, it was an extremely common substance in many building construction materials. It was used in or added to hundreds of products to increase durability, fire-resistance and sound and heat insulation qualities. In the mid-1970s, government-required inspections of schools and public buildings uncovered significant amounts of asbestos present in pipe coverings, fireproofing, soundproofing and insulation.
The mere presence of asbestos in building materials is not a hazard, however. The danger exists only when asbestos dust is released into the air because of deterioration, or by cutting, sawing, drilling or other disturbance. Even though federal laws in the 1980s required and helped fund identification and cleanup of asbestos hazards in schools and public buildings, asbestos has not been completely eradicated.
A review of National Center for Health Statistics data for 2003 revealed that schools and hospitals ranked 3rd and 4th among all businesses reporting mesothelioma cases. Given that it takes up to 40 years after exposure to develop mesothelioma, these victims were probably exposed in the 1960s.
Looking forward, school and hospital workers exposed to asbestos during the 1980s, possibly during cleanup efforts, will not begin exhibiting mesothelioma symptoms until the 2010s or 2020s.
In theory, the same sorts of risks can exist in private homes if asbestos containing materials are deteriorating or disturbed, but we lack statistical data to confirm how frequently this occurs.
You must log in to post a comment.