“Us Tareyton smokers would rather fight than switch.” That was the slogan for Tareyton cigarettes, whose ads featured smokers with blackened eyes. It was as if they’d had to fend off thugs from Kool or Lucky Strike who were intent on prying their precious Tareytons from their nicotine-stained fingers.

I don’t know whether electronic cigarette users are as pugilistic, but after my column last week on whether using those devices — what’s known as “vaping” — is allowed on Metro, I heard from both sides of the matter.

Lyle Feisel of St. Michaels, Md., wrote: “It seems to me that in the issue of e-cigarettes in public places, the first question that needs to be answered is this: If a vaper is vaping vapor in a public place and devapes some prevaped vapor, will I, a habitual breather, unwillingly vape that devaped vapor and thereby absorb some noxious elements or detect some obnoxious odors?”

Or, to look at it from the other direction: “If e-cigs emit only harmless vapor, then why should their use be banned where smoking is banned?” asked Jeff Barron of Easton, Md. “Because people don’t like the way it looks?

The crux of the matter is this: It may be odd to see someone “smoking” a “cigarette” on a Metro train or bus, but am I going to be harmed by e-cigarettes?

According to a Food and Drug Administration spokeswoman, “Further research is needed to assess the potential public health benefits and risks of electronic cigarettes and other novel tobacco products.” (CHRISTIAN HARTMANN/REUTERS)

The industry says no. “It wouldn’t do anything to you,” said Ray Story, head of the Atlanta-based Tobacco Vapor Electronic Cigarette Association. “Some of the cologne would probably be far more repulsive than a couple of people vaping.”

Of course, Ray has a vested interest. He also heads a company that sells e-cigarettes. He says no research has proved a link between second-hand vapor and anything bad. He thinks people should be allowed to vape anywhere, including on public transportation.

“The worst thing we can do is take an individual who’s made a conscious choice to utilize a product that is less harmful [than cigarettes] and then put him back in those smoking areas where for sure he is going to be subject to second- and third-hand smoke,” he said.

Not so fast, said Tobias Schripp, a researcher at the Fraunhofer Institute in Germany who has studied electronic cigarettes.

“It is a common misunderstanding that the exhaled vapor is ‘just water vapor,’ ” Tobias wrote me in an e-mail. A recent study he conducted found that nicotine and propylene glycol — a compound used in fog machines — can be found in e-cigarette exhalations. He did not find formaldehyde, which is common in real cigarettes.

But Tobias pointed out that some people are sensitive to propylene glycol.

So, e-cigs are better than real cigs, but possibly not as good as no cigs at all. Or, as a study by the German Cancer Research Center concluded: “Adverse health effects for third parties exposed cannot be excluded because the use of electronic cigarettes leads to emission of fine and ultrafine inhalable liquid particles, nicotine and cancer-causing substances into indoor air.”

On our side of the Atlantic, an Food and Drug Administration spokeswoman e-mailed: “Further research is needed to assess the potential public health benefits and risks of electronic cigarettes and other novel tobacco products.”

By the way, things are as murky on New York City’s subways as they are on ours. An MTA spokeswoman responded via e-mail: “The advent of electronic cigarettes is such a new phenomenon that it is not specifically addressed in MTA New York City Transit’s current Rules of Conduct. The New York City Police Department provides security and enforcement for all subway rules. We will monitor the situation and see whether an update to the rules is required at some point in the future.”

Mike Kelley of Alexandria questions whether Metro can police e-cigarettes anyway. He said he’s seen more people consuming food on the subway recently without consequence. “If they’ve got clearly defined and widely publicized policies on no eating or drinking on the trains but cannot enforce them, what does it matter if they develop a policy for e-cigarettes?” Mike wrote.

I don’t think the two things are that different, actually: Like eating, vaping involves repeatedly sticking something in your mouth and taking it out. We don’t like it when someone uses a fork to shovel lo mein into his or her pie hole on the Green Line, so why should we tolerate a fake cigarette?

But obviously, more study is needed.

For previous columns, visit washingtonpost.com/johnkelly.