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During the 18th century, 3 important observations launched the field of cancer epidemiology (epidemiology is the study of causes, distribution, and control of diseases):

• In 1713, Bernardino Ramazzini, an Italian doctor, reported the virtual absence of cervical cancer and relatively high incidence of breast cancer in nuns and wondered if this was in some way related to their celibate lifestyle. This observation was an important step toward identifying and understanding the importance of hormones (like the changes that come with pregnancy) and sexually-transmitted infections and cancer risk.
• In 1775, Percival Pott of Saint Bartholomew’s Hospital in London described an occupational cancer in chimney sweeps, cancer of the scrotum, which was caused by soot collecting in the skin folds of the scrotum. This research led to many more studies that identified a number of occupational carcinogenic exposures and led to public health measures to reduce a person’s cancer risk at work.
• Thomas Venner of London was one of the first to warn about tobacco dangers in his Via Recta, published in London in 1620. He wrote that “immoderate use of tobacco hurts the brain and the eye and induces trembling of the limbs and the heart.” And 150 years later, in 1761, only a few decades after recreational tobacco became popular in London, John Hill wrote a book entitled Cautions Against the Immoderate Use of Snuff. These first observations linking tobacco and cancer led to epidemiologic research many years later (in the 1950s and early 1960s) which showed that smoking causes lung cancer and led to the US Surgeon General’s 1964 report Smoking and Health.

Epidemiologists continue to search for factors that cause cancer (like tobacco use, obesity, ultraviolet radiation), as well as those things that can help protect against cancer (such as physical activity and a healthy diet). This research provides evidence to guide public health recommendations and regulations.

As molecular biologists learn more about how factors cause or prevent cancer, this information is used to study molecular epidemiology, which is the study of interactions between genes and external factors.