NIOSH Safety and Health Topic:Occupational Cancer |
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Based on well-documented associations between occupational exposures and cancer, it is estimated that approximately 20,000 cancer deaths and 40,000 new cases of cancer each year in the U.S. are attributable to occupation. Millions of U.S. workers are exposed to substances that have tested as carcinogens in animal studies. However, less than 2% of chemicals in commerce have been tested for carcinogenicity. Cancer is a group of different diseases that have the same feature, the uncontrolled growth and spread of abnormal cells. Each different type of cancer may have its own set of causes. Many factors play a role in the development of cancer. The importance of these factors is different for different types of cancer. A person's risk of developing a particular cancer is influenced by a combination of factors that interact in ways that are not fully understood. Some of the factors include:
In many cases, these factors may act together or in sequence to cause cancer. Cancer ClustersScenario
Worker pulling a hydraulic cleaner from an open vinyl chloride
reactor at Avon Lake, OH in 1974, prior to the exposure controls
mandated by the OSHA standard. Vinyl chloride is known to cause
angiosarcoma of the liver.
Three members of the staff of an elementary school were diagnosed with cancer in 1997 and 1998; one person each with brain, liver, and ovarian cancer. Since 1998, four cases of breast cancer also were diagnosed. Increased concern among employees regarding the potential association between the workplace and the cancers prompted a request for an investigation. The information below addresses cancer clusters in general and shows how this type of information would be used to respond to this scenario. Cancers often appear to occur in clusters, which scientists define as an unusual concentration of cancer cases in a defined area or time. A cluster also occurs when the cancers are found among workers of a different age or sex group than is usual. The cases of cancer may have a common cause or may be the coincidental occurrence of unrelated causes. Although the occurrence of a disease may be random, the distribution of that disease may not be uniform, and clusters of disease may arise by chance alone. When cancer in a workplace is described, it is important to determine the primary site of the cancer. What do we look for when evaluating a cancer cluster?
Conclusions for the scenario above
Workers on top of a coke oven. Work on top of coke ovens is known to
cause lung and skin cancer, and thought to cause kidney cancer.
The distribution of types of cancer did not appear unusual given the age and gender of the employees. No known biologically significant exposures were identified. The building only became occupied in 1992, therefore, given what we know about latency periods, none of the cancer cases met the latency criterion. Given this information, it was concluded that the cancers reported among these workers were unlikely to be the result of employment at the elementary school. This scenario illustrates the key questions that are answered in response to cancer cluster inquiries. Historical experience at NIOSH has shown that most reports of cancer clusters indicate the coincidental occurrence of cancer in workforce members. In most situations, particularly in non-industrial work environments, it is not possible to link the cancers to exposures at work. Carcinogenic Agents
National Academies EvaluationWorker and Public Health Activities Program Administered by the Department of Energy and the Department of Health and Human Services – Evidence Package General: Causes, Specific Diseases
Regulation and Policy
Surveillance
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