In the near future, all 1.2 million American households residing in public housing units may be banned from smoking tobacco indoors – but the now-commonplace proposed regulation is inflaming passions, with the Department of Housing and Urban Development threatening to include e-cigarettes in the ban.

The department explicitly requested input Thursday about whether to include the vapor-producing devices when it issues a final regulatory rule sometime after a 60-day public comment period, and familiar battle lines already are drawn.

The American Lung Association and the Campaign for Tobacco-Free Kids say e-cigarette use should be banned by HUD even if the devices are less harmful than their known cancer-cousin relatives, as they emit nicotine, pose a small fire risk and emit particles into the air.

On the other side are consumer advocates and e-cigarette trade groups, who say including the devices in smoking bans would discourage people from transitioning from cigarettes to a likely less harmful alternative.

“Vapor products create no smoke and leave behind no lingering smell, so outside of hiring peeping Toms, there is simply no way to enforce such a ban,” scoffs Gregory Conley, president of the American Vaping Association trade group.

Julie Woessner, executive director of the Consumer Advocates for Smoke-free Alternatives Association, says “it is unlikely that anyone who was dedicated to vaping instead of smoking would obey this rule since there is no way it could be enforced.”

“It is generally a bad idea to create laws that we know people are going to flout, thus undermining the legitimacy of all laws,” she says.

But Erika Sward, an assistant vice president at the American Lung Association, says even if compliance isn’t 100 percent, applying the ban to e-cigarettes would be worth it.

Sward says people usually comply voluntarily with smoking bans. About 600 housing authorities – comprising about 200,000 households – already ban smoking indoors, and at least two – in Boulder, Colorado, and Springfield, Massachusetts – this year added e-cigarettes to their policies, she notes.

“E-cigarettes are a tobacco product and because they are unregulated and many of the chemicals and exposures are unknown we must err on the side of protecting public health,” Sward says. “We know smoking and exposing people to secondhand smoke is like jumping off a 15-story building. We don’t know yet if using e-cigarettes and exposing people to e-cigarettes is jumping off an eight-story building or a five-story building.”

E-cigarettes work by heating an oftentimes flavored liquid made of propylene glycol and/or vegetable glycerin that’s laced with tobacco-derived nicotine. The two most popular base liquids aren’t carcinogenic when ingested, but their effect when heated and inhaled is unclear.

Research has shown e-cigarettes pose lower health risks than traditional cigarettes and fill homes with less particulate matter.

But Vince Willmore, a vice president at the Campaign for Tobacco-Free Kids, says lingering uncertainty over the long-term health effects of e-cigarettes should tip the scales toward a prohibition on indoor use.

“E-cigarettes should be included in the policy both to simplify enforcement and because the health risks of exposure to e-cigarette aerosol is unclear,” he says. “Given the uncertainties about the health impact of e-cigarettes, it is prudent to prevent exposure by non-users, especially children.”

E-cigarette advocates aren’t having it, though. Woessner says lumping the increasingly popular devices with cigarettes would undermine public health and “send the signal that vaping poses similar risks to smoking, when in reality it is about 99 percent less harmful.” (A controversial Public Health England report said they are 95 percent less harmful.)

“Anything that would discourage smokers from making the switch to low-risk e-cigarettes is bad public policy,” she says. “Whatever one's views on forcing smokers to leave their homes to smoke, if that is going to be the policy, we should take advantage of the fact that it encourages smokers to switch to low-risk smoke-free alternatives if they are allowed to vape in their homes.”

Conley says authorities would undermine the success of the cigarette-smoking ban, too, by taking away what’s become a common off-ramp for smokers. “[They would] be losing not just the opportunity for harm reduction among tenants, but also the only viable way to enforce the law,” he says.

A spokesman for another e-cigarette trade group, the Smoke-Free Alternatives Trade Association, said the group plans to weigh in against a possible vapor ban, pointing out low-income users of Medicaid disproportionately smoke cigarettes, costing taxpayers for related health care costs.

It’s unclear which side will win, and there’s sure to be intense lobbying. The outcome may be more symbolic than practically meaningful, however, as HUD Secretary Julian Castro stressed to The New York Times evictions are not meant to be the go-to penalty for violators. The final rule would allow local housing agencies an 18-month transition period.