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Asbestos hazards epidemiology

Cases of Cancer Clusters

A well-known cancer cluster was discovered in the 1960s and continues to be studied today. The use of asbestos, a naturally occurring mineral, was prevalent in factories, shipyards and building products throughout the 1950s and 1960s. Many individuals who were exposed to asbestos on the job developed a disease known as mesothelioma. Many individuals also developed lung cancer. These diseases were directly linked to asbestos exposure and this exposure is still the largest known cause of mesothelioma in the world today.

Between 1941 and 1971 many women were exposed to a drug called diethylstilbestrol (DES). This synthetic hormone was prescribed for women to prevent miscarriage. It was also used to prevent breast engorgement during pregnancy. Over 10 million women were exposed to the hormone and the cancer cluster was discovered after many daughters developed vaginal clear cell carcinoma. This rare cancer is directly linked to exposure in the womb to DES. It is the largest known cause of vaginal clear cell carcinoma.

These two cases are examples of cancer clusters in very specific situations with clear-cut exposures and development of very rare forms of cancer. Other historical cases include the development of leukemia and lymphoma in chemical workers who were exposed to the chemical benzene, dye workers exposed to aniline compounds who developed bladder cancer and farmers who developed skin cancer after extreme exposure to the sun.

Cancer is not the only disease that can sometimes occur in clusters. Other disease clusters have also helped to identify environmental hazards like bacteria contaminated foods, and a respiratory illness now known as SARS. Epidemiologists study these types of environmental factors as well as those known to cause cancer.