New York City Mayor Michael Bloomberg will sign into law Monday a ban on using electronic cigarettes anywhere conventional cigarette use is prohibited. Critics says the new restriction may – contrary to its stated intent – harm public health.

Bloomberg will sign the legislation, approved Dec. 19 by the city council in a 43-8 vote, around 2 p.m., spokeswoman Evelyn Erskine says.

The ban is the latest – and last – in the billionaire mayor's decade-long campaign against smoking. In 2003 the mayor signed into law a ban on smoking in bars and restaurants. In 2011 the ban was extended to include city parks and beaches. And on Nov. 19 he signed a bill raising the city's tobacco age to 21.

The last day of Bloomberg's 12 years in office is Tuesday.

Charles Connor, former president and CEO of the American Lung Association, is one notable opponent of the new rule.

"Above all else, the role of our government should be to further advance the nation's efforts to reduce the harm and death toll caused by combustible tobacco products," Connor said in a statement.

"Electronic cigarettes are poised to revolutionize the tobacco industry by one day making traditional cigarettes obsolete," said Connor, whose mother died last December from smoking-related lung failure and who now advises a group promoting the use of e-cigarettes. "By impulsively and inaccurately lumping vaping in with traditional cigarette smoking, a ban on these game-changing devices will discourage other smokers from trying a positive alternative."

Gregory Conley, a consultant to the e-cigarette industry on legislative issues, agrees.

"Banning something that helps smokers quit, solely because it looks like smoking, is a new height of absurdity for Mayor Bloomberg," says Conley, who formerly served as spokesman of Consumer Advocates for Smoke-free Alternatives.

"There will be no public health benefits from the passage of this law," Conley says. "Inevitably some smokers will interpret the ban to mean that e-cigarettes are just as hazardous as cigarettes. Sending that signal to smokers is simply irresponsible. Indeed, the ban will actually hamper Mayor Bloomberg's long-stated quest to eradicate smoking."

Unlike conventional cigarettes, which burn tobacco leaves, e-cigarettes vaporize a liquid that's a blend of propylene glycol and/or vegetable glycerine, combined with flavoring and tobacco-derived nicotine.

E-cigarette sales in the U.S. are projected to exceed $1.7 billion in 2013, according to a Wells Fargo Securities estimate, doubling 2012 sales.

The long-term effects of smoking e-cigarettes have not been studied, but even anti-tobacco hawks acknowledge the devices are likely healthier than their combustible cousins.

A 2012 study by University of Perugia researchers in Italy found the particulate matter of exhaled e-cigarette vapor is significantly lower than tobacco smoke, conceivably reducing or eliminating second-hand inhalation. A large-scale study by New Zealand researchers, published in September by The Lancet, found e-cigarettes are as effective as nicotine patches in helping smokers quit. Various nicotine concentrations are offered by e-cigarette companies, allowing users to wean themselves off the drug.

Although often a trend-setter, New York City is extending its smoking ban after several other states and cities did so.

Across the Hudson, then-Gov. Jon Corzine, D-N.J., extended his state's smoking ban to cover e-cigarettes in 2010. Utah followed in 2012. Health regulators - rather than city councilmen - in Boston and Seattle also added e-cigarettes to local smoking bans, in 2011 and 2010. But the Big Apple measure may propel another round of rules elsewhere.

Audrey Silk, founder of the smokers' rights group New York City Citizens Lobbying Against Smoker Harassment, says the newest nicotine restriction proves that Bloomberg's anti-smoking crusade has "nothing to do with smoke."

Rather, she says, "as we've been screaming, this has to do with socially engineering a section of society that smokes."

Silk believes Bloomberg is a "control freak" who "has a God complex."

"He's saving nobody's lives. We're all going to die," says Silk, who smokes conventional cigarettes.