DEBATE over e-cigarettes — battery-powered cigarette look-alikes that heat liquid nicotine but emit a harmless vapor — is raging. New York City and Chicago are considering adding e-cigarettes to their bans on smoking in bars, restaurants and parks, and Los Angeles is moving to restrict e-cigarette sales, even though e-cigarettes don’t generate smoke and, while not proved to be entirely safe for users, are undoubtedly less hazardous than tobacco cigarettes.

The evidence, while still thin, suggests that many e-cigarette users, hoping to kick the habit, use e-cigarettes as a safer alternative to tobacco. Research also suggests that e-cigarettes may be better at helping to sustain smoking cessation than pharmaceutical products like nicotine patches or gums.

No one believes nicotine addiction is a good thing, and our qualified support for e-cigarettes is not one we reach lightly. Although some e-cigarette manufacturers have no links to the tobacco industry, Big Tobacco is consuming an ever-greater share of the e-cigarette market. It is hard for public health advocates like us to look favorably on anything the industry wants. But history shows that harm reduction — the doctrine that many risks cannot be eradicated and that efforts are best spent on minimizing the resulting harm — has had an important place in antismoking efforts and suggests that regulation is better than prohibition.

It’s been only a half-century since the federal government took an interest in making tobacco products safer. In 1964, Surgeon General Luther L. Terry issued a watershed report definitively linking smoking with lung cancer. But he also described research into new kinds of cigarettes as “a promising avenue for further development.” In the early 1970s, the government spent some $6 million a year to try to develop safer tobacco products. Even the health secretary Joseph A. Califano Jr., who called smoking “Public Enemy No. 1,” saw, in 1978, a place for “research aimed at creating a less hazardous cigarette.” As late as 1981, the surgeon general advised smokers who couldn’t or wouldn’t quit to switch to low-tar and low-nicotine brands.