ELECTRONIC cigarettes made their American debut seven years ago. People have bickered about them ever since. Some praise e-cigarettes—which deliver a vapour with nicotine, but no tobacco—for helping traditional smokers to quit. Others fret that they will promote nicotine addiction and reduce the stigma of smoking, which in America now ranks somewhere between theft and public indecency.

On April 24th American regulators stepped in (as the European Parliament did in February). The Food and Drug Administration (FDA) proposed rules for e-cigarettes. These would, among other things, ban sales to children and require firms to list ingredients, include warnings that nicotine is addictive and register new products with the agency. The FDA did not propose banning flavours or advertising, but may do so in future. It will accept comments on its plan until July 9th. Even after it finalises this set of rules, it may later issue further restrictions.

Cities, states and even employers are testing their own rules, too. For example UPS, a shipping company, is charging workers who use e-cigarettes more for their health insurance. (Only non-union workers, of course; the Teamsters would surely stub out such an idea.) As of April 29th it is forbidden to “vape” in Chicago’s restaurants and shops or even in New York City’s parks. Rhode Island may slap e-cigarettes with an 80% tax. On May 1st city health commissioners will meet in Washington, DC to discuss further rules.

One reason for this jumble is that information about e-cigarettes—what they contain, who uses them and under what circumstances—is still cloudy. Last year the Lancet, a medical journal, reported that e-cigarettes were as effective as nicotine patches in prompting smokers to quit. But the FDA cautions that the evidence is still slim. E-cigarettes may feed smokers’ addiction when they cannot puff tobacco, rather than prompting them to abstain. Non-smokers might start “vaping”. Different studies find that e-cigarettes contain different amounts of nicotine and other toxins.

For now, makers of e-cigarettes are puffing ahead. American sales of e-cigarettes reached $724m in the year to April 12th, 72% above what they were in same period last year, according to Nielsen, a research firm. The day that the FDA proposed its rules, Altria, a tobacco company, said it would launch a new line of e-cigarettes in June.