Sheet Metal Workers Still at Risk For Asbestos Diseases Despite Improved OSHA Standards
Short Term Asbestos Exposure Sill a Health Hazard
There are many construction trades that have historically run the risk of asbestos exposure-sheet metal work is one of the more prevalent occupations with recognized exposure to asbestos. In 1985, the Sheet Metal Workers International Association and the Sheet Metal and Air Conditioning National Association formed the Sheet Metal Occupational Health Institute Trust to examine the health impact of asbestos exposure in the sheet metal industry. In the original study by the Sheet Metal Occupational Health Institute Trust, 32% of the workers studied between 1986 and 1990 were found to have lung abnormalities consistent with occupational lung diseases, known as pneumoconiosis.
In an updated study, Change in Prevalence of Asbestos-Related Disease Among Sheet Metal Workers, 1986-2004, (Laura Welch, MD, et al), a total of 18,211 sheet metal workers were examined between 1986 and 2004 to look for changes in radiographic abnormalities due to occupational lung diseases for different decades of sheet metal work.
Classifications of Sheet Metal Workers Within Study
To look at the relationship between the calendar year an individual started sheet metal work and the frequency of pleural disease, the study was divided up into three groups:
- Before 1949; including work in shipyards during WWII.
- Between 1950 and 1969; a period where asbestos use became more prevalent in the US.
- After 1970; the start of the decade when asbestos use dropped significantly due to the introduction of the Clean Air Act of 1970 and asbestos being labeled as a hazardous air pollutant.
In looking at the unadjusted numbers, sheet metal workers that started in the industry before 1949 had more incidents of asbestos-related diseases than did those that started work between 1950-1969 or after 1970.
Amid all the contributory factors for asbestos diseases amongst sheet metal workers, strong indicators for the prevalence of non-malignant asbestos diseases found in one group more than others were:
- Shipyard work-more prevalent in workers that started before 1949
- Years of smoking
- Years of sheet metal work before 1950
Limited Exposure Fails to Prevent Disease, Latency Period Before Disease Increases
The study also documented a decreasing trend of asbestos diseases in workers that started in the sheet metal trade after 1970 in comparison to those that started before 1949. The results suggest that reduced asbestos exposure due to stricter OSHA regulatory standards and fewer workers with shipyard exposure will reduce the occurrence of asbestos diseases. While recent exposure to asbestos has dropped, the average latency period from 40.5 years (reported in studies from the 1980's) has increased to 45.8 years, indicating that asbestos diseases take longer to develop with lower exposures. According to the updated study (Change in Prevalence of Asbestos-Related Disease Among Sheet Metal Workers, 1986-2004), there is an expectation that these numbers could increase as highly exposed populations continue to age.
Short Duration & High Exposure Level Show Increased Mesothelioma Risk
Between 1940 and 1979, an estimated 27.5 million workers were occupationally exposed to asbestos, including occupations like construction work, shipyards, manufacturing and mining operations among others; 18.8 million of these workers were thought to have had high exposures to asbestos. Some occupations, like the sheet metal trade, routinely exposed workers to air that exceeded 20-40 fibers per cubic centimeter of air (f/cc), levels that are 200-400 times the current OSHA standard of 0.1 f/cc. At this volume of respirable asbestos, even short-term (months) exposure resulted in an increased risk of mesothelioma and lung cancer.
According to the 2002 Work Related Lung Disease report from the National Institute for Occupational Safety and Health (NIOSH), the estimated number of hospital discharges with a diagnosis of asbestosis increased from 5,000 in 1990 to 20,000 in 2000. Due to the long latency time between exposure and the development of mesothelioma or asbestos lung cancer, many asbestos disease cases currently being diagnosed are due to exposure that originated between 1940 and 1970. Today, watching for changes in health is important, as workers from that era are coming into the latency window for developing asbestos diseases.