Last month, New York Mayor Bloomberg proposed a ban on outdoor smoking in and on 1,700 parks, plazas, and beaches. The City Council in Cambridge, Massachusetts recently followed New York's lead (Chronicle 10/4/10), joining a number of college campuses and California cities. This radical intrusion into private lives is rationalized as a public health measure to protect citizens from secondhand smoke. It's therefore worth reviewing the debate from the past decade when it became the accepted view that secondhand smoke is a public health risk. Anti-smoking activists state with assurance that "the science is settled"; secondhand smoke murders 3,000 or...