In 1775, a surgeon named Percivall Pott at St. Bartholomew’s Hospital in London noticed an increase in cases of scrotal cancer among the chimney sweeps who came to his clinic. He pushed beyond the usual explanations of this disease as venereal in nature. His work built on that of the 18th-century Italian doctor Bernardino Ramazzini, who noticed diseases among certain professions. His work mentioned soot as an agent for causing cancer. Pott stumbled onto the idea that an external agent, a carcinogen, was behind the scrotal cancer. Therefore, people could potentially prevent cancer. As laws in England raised the age at which boys could apprentice as chimney sweeps, and then forbade the practice entirely, the epidemic of scrotal cancer disappeared.

In the 1760s, a British apothecary named John Hill claimed that “snuff—oral tobacco—could also cause lip, mouth, and throat cancer” (239) and published a colorfully written pamphlet to that effect. Tobacco use was becoming popular in England and exploded after the development of cigarettes. The craze also spread to America. As so many people were smoking (90% of men by the turn of the 20th century in some places), it was difficult to discern its effects. Its dangers vanished in what one historian called “the cigarette century” (242).