Asbestos diseases, such as asbestosis or pleural plaques – or even the more fatal forms of asbestos cancer such as lung cancer or mesothelioma – usually occur in people who work directly with the material or who for some other reason are exposed to it on a regular, prolonged, or substantial basis.
Historically, asbestos exposure has been of greatest concern to those involved in mining and milling of the raw material, people in the construction trades, and workers engaged manufacturing or using products containing asbestos. Secondary exposure occurred when people who did not work directly with asbestos were inadvertently exposed to fibers as a result of sharing workspaces where others handled asbestos. For example, electricians who worked in shipyards were exposed when asbestos was used to coat the ships’ pipes and hulls.
In addition to people who worked with asbestos either directly or indirectly, workers’ families and other household contacts were also at risk in the past. Before strict industrial hygiene rules were put in place, asbestos workers went home covered in asbestos dust; family and household members were then exposed via inhalation of the dust from workers’ skin, hair, and clothing, and during laundering of contaminated work clothes. Studies have shown increased rates of asbestos-related illnesses and deaths in the household contacts of asbestos workers.
Finally, asbestos was released into the air and soil around facilities such as refineries, power plants, factories, shipyards, steel mills, vermiculite mines, and building demolitions. People living around these sites were also exposed to asbestos.
Currently, the people most heavily exposed to asbestos in the United States are those in construction trades, and most occupational exposures occur during repair, renovation, removal, or maintenance of asbestos that was installed years ago. An estimated 1.3 million construction workers, as well as workers in building and equipment maintenance, are potentially at risk. Historically most asbestos was used in construction, and even today over 60 percent of asbestos produced is used in this trade. Risk to these workers can be considerable if occupational safety standards are not followed.
One specific group at risk of developing an asbestos-related disease are the people who were involved in rescue, recovery, and cleanup at the site of the September 11, 2001, attacks on the World Trade Center (WTC). When the WTC buildings were attacked, hundreds of tons of asbestos, which had been used in the construction of the North Tower, were released into the atmosphere. First responders – firefighters, police officers and paramedics – as well as the construction workers and volunteers who worked in the rubble at Ground Zero are considered at greatest risk. Residents in close proximity to the WTC towers and those who attended schools nearby may also be in danger of developing asbestosis, pleural plaques, malignant mesothelioma, lung cancer, or any one of a number of asbestos-related illnesses.
Over two-third of WTC rescue and recovery workers experienced new or worsened respiratory symptoms while working at the WTC site. The WTC Worker and Volunteer Medical Screening Program, which was established to identify and characterize possible WTC-related health effects in responders, found that about 28 percent of those tested showed signs of abnormal lung function, and 61 percent of those who had no prior health problems developed respiratory symptoms. However, it is important to remember that debris components other than asbestos may have contributed to these symptoms. The health of these workers and people who lived or attended schools near the WTC towers will need to be monitored to determine the long-term medical consequences of their exposure.
Although experts agree that health risks from asbestos are greater when the exposure is heavier and of longer duration, investigators have found asbestos-related diseases in individuals with only brief exposures. Heavy asbestos exposure peaked during the 1960s and 1970s in western, industrialized nations and declined as worker safety rules were instituted and later as the industrial use of asbestos decreased. But because many of those who develop asbestos-related diseases show signs of illness a long time after their first exposure (sometimes as much as 40 years later), even now workers exposed to asbestos in the 1960s and 1970s are manifesting asbestos-associated diseases.
Estimates have been made of the numbers of cancers that are projected to result from past exposures to asbestos in a number of occupations and industries. From 1940 through 1979, it is estimated that 27.5 million people had potential asbestos exposure at work. Of these, 18.8 million had exposure in excess of that equivalent to two months’ employment in primary manufacturing or as an insulation installer. In 1982, the number of deaths attributable to a form of asbestos cancer was estimated at 8,200 deaths annually. According to the Environmental Working Group, total deaths related to asbestos between 1979 and 2000 was about 230,000.