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. 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 Clusters 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. Because cancer is a common disease, cancer can be found among people at any workplace. In the United States, one in two men and one in three women will develop cancer over the course of their lifetime. These figures show the unfortunate reality that cancer occurs more often than many people realize. Disease or tumor rates are very variable in small populations and rarely match the overall rate for a larger area, such as the state, so that for any given time period some populations have rates above the overall rate and others have rates below the overall rate. So, even when there is excess, this may be completely consistent with the expected random variability. Cancer clusters thought to be related to a workplace exposure usually consist of the same types of cancer. When several cases of the same type of cancer occur and that type is not common in the general population, it is more likely that an occupational exposure is involved. When the cluster consists of multiple types of cancer, without one type predominating, an occupational cause of the cluster is less likely. When a known or suspected cancer-causing agent is present and the types of cancer occurring have been linked with these exposures in other settings, we are more likely to make the connection between cancer and a workplace exposure. We also look to see whether cancer is occurring among employees in particular jobs or areas of the workplace. This can help to identify exposures. The time between first exposure to a cancer-causing agent and clinical recognition of the disease is called the latency period. Latency periods vary by cancer type, but usually are 15 to 20 years, or longer. Because of this, past exposures are more relevant than current exposures as potential causes of cancers occurring in workers today. Often, these exposures are hard to document. Carcinogenic Agents
NIOSH Carcinogen List General: Causes, Specific Diseases
Overview of Preventable Industrial Causes of
Occupational Cancer
NIOSH: Cancer Research Methods
NIOSH:
Cancer Research Methods Workshop
The Importance of Information Dissemination in
the Prevention of Occupational Cancer Cancer Clusters (CDC Web site) Agencies, Organizations, etc.
American Cancer Society (ACS Web site) Regulation and Policy
OSHA Standards Surveillance
Work Related Lung Disease Surveillance Report 2002
Section 13. Lung Cancer
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