The applicability of Congress' power to the agents and instruments of commerce is implied in Marshall's opinion in Gibbons v. Ogden, 628 where the waters of the State of New York in their quality as highways of interstate and foreign transportation were held to be governed by the overriding power of Congress.
Lung cancer today is primarily caused by the inhalation of smoke from cigarettes, which is also why the disease was quite rare prior to the 20th century. Lung cancer was not even recognised medically until the 18th century, and as recently as 1900 only about 140 cases were known in the published medical literature.
Three percent of American adults are smokeless tobacco users. They run the same risks of gum disease, heart disease, and addiction as cigarette users, but an even greater risk of oral cancer. Each year about 30,000 Americans are diagnosed with oral and pharyngeal cancers, and more than 8,000 people die of these diseases.