In response to the emerging scientific evidence that cigarette smoking posed a significant health risk to the user, in the early 1950's the major cigarette manufacturers began widespread promotion of filtered cigarettes to reassure smokers that, regardless of whatever unhealthy constituents were in cigarette smoke, filters were a "scientific" breakthrough. Advertisements for Viceroy's "health guard filter" stated, "DENTISTS ADVISE-Smoke VICEROYS-The...