In the past decade, big tobacco has finally developed and marketed a cigarette* that does not cause cancer**.

It's the closest we've come to a cancer-free cigarette, which tobacco companies have been fantasizing about since the 1950s.

But there are a few catches.

*First, they are arguably not even cigarettes, without the tobacco content or taste that the 1.1 billion global smokers enjoy. That's the primary reason why e-cigarettes still represent only a tiny share of the market.

**Second, while e-cigarettes probably won't give you cancer, they may still contribute to heart disease, heart attack, stroke, and other ailments. Ultimately we know very little about the health effects — and given the history of cigarettes, that should worry you.

Cancer-free?

People smoke e-cigarettes to get a nicotine high, similar to the kind one gets with traditional cigarettes.

While the nicotine in e-cigarettes comes from the tobacco plant, it is separated from tar and other plant material that cause cancer when smoked.

Because there hasn't been any research into the long-term effects of inhaling nicotine vapor from an e-cigarette, we can't say for sure that they don't cause cancer. What we can say is that the e-cigarettes are most likely healthier than tobacco cigarettes because they lack the 4,000 plus chemicals from the tobacco leaves.

E-cigarettes hold nicotine in liquid form, which gets heated into a vapor and released when a user sucks on the end.

That nicotine high

The stimulating effects of nicotine are immediate.

It makes its way through the mucus membranes of your lungs and into your bloodstream, then into your brain. When it hits your brain, nicotine binds to brain cells that turn on the body’s "wake-up call" pathways. It also releases dopamine, our "feel good" brain chemical, and glutamate, which is involved in learning and memory, reinforcing this good feeling and making your memory of it stronger.

In about an hour, half of the nicotine from that smoke is already broken down and expelled from your body, leaving you craving more.

Regular nicotine users develop a tolerance to the drug, making them use more and more, for example, moving from a cigarette a day to a few packs per week. The same thing can happen with inhaled nicotine.

It can still kill you

E-cigarettes may not cause cancer, but that doesn't make them safe.

Nicotine on its own is an extremely toxic poison similar to pesticides. When you take too much, you can get nicotine poisoning, which causes vomiting and nausea, and headaches.

Even in smaller doses it can be dangerous. When you take in nicotine, your body releases adrenaline — giving you a sudden rush of energy and increasing your heartbeat, blood pressure, and breathing. It also tells your body to pump your blood with sugars. Because of these effects, nicotine use is linked to heart disease, heart attack, and stroke.

A small study, presented at the European Respiratory Society’s annual meeting in February 2012 showed that e-cigarette smoking could have negative effects on people with coronary artery disease who have plaques in their arteries, because it lowers blood oxygen levels after 10 minutes of e-cigarette use. The researchers, from the University of Athens in Greece, suggested that people with these health issues should use other nicotine products to quit smoking.

Another small 2012 study published in the journal Chest also showed changes in lung functioning after use of e-cigarettes.

When asked about the Greek study, Klaus Lessnau, a lung doctor at Lennox Hill Hospital in New York City, told Robert Glatter of Forbes that "electronic cigarettes cannot be recommended to improve lung health, but there is certainly some degree of harm reduction compared to regular cigarette use," because of the presence of fewer toxic and tar-based substances.

More research needed

A 2010 study published in the journal Tobacco Control suggested the five major e-cigarette brands had design flaws, lack of adequate labeling, and potential quality control issues.

The study was led by University of California, Riverside researcher Prue Talbot, who said at the time, "there are virtually no scientific studies on e-cigarettes and their safety. Our study – one of the first studies to evaluate e-cigarettes – shows that this product has many flaws, which could cause serious public health problems in the future if the flaws go uncorrected."

As she noted, the health effects of nicotine, which is addictive, haven’t been adequately studied when separated from tobacco smoke. We know that when a regular cigarette is inhaled, the chemicals in it can cause cancer and lung problems. We don’t know how the body reacts to pure nicotine without these other chemicals — it could have its own set of negative health consequences.

Notably, former Surgeon General Richard Carmona — who highlighted the dangers of second-hand smoke during his tenure under George W. Bush — just joined the board of top selling e-cigarette company NJoy, Inc.

In March, Carmona said that he would be spearheading research into the health effects of inhaled nicotine and e-cigarettes.

Regulation

E-cigarette company NJoy sued the Food and Drug Administration in 2010 to prevent it from regulating the vaporizers as smoking cessation devices. The FDA is trying to regulate them as tobacco products via a proposal currently in the public review period. Beyond that, however, the FDA has limited options.

There is also no minimum age requirement and they are easily attainable online. This means young children purchase them with much less difficulty than buying a pack of smokes. They also come in flavors that kids could like such as chocolate, strawberry, and caramel.

Michael Tolmach, executive officer of Eonsmoke, LLC, told Business Insider in an email that, "Eonsmoke as a brand puts Surgeon General warnings on all products and support legislation that bans the sale of electronic cigarette to minors across all 50 American states and abroad. We only sell to licensed tobacco retailers and stress very harshly of the requirements to validate age when selling e-cigarettes."

Another confusing factor is that with some e-cigarettes, you are also inhaling a flavoring or other additives — not all of which are disclosed on the packaging.

For instance, Eonsmoke and LOGIC e-cigarettes deliver their nicotine using a polyethylene glycol or propolene glycol solution, along with other additives like glycerine and flavorings. Propylene glycol is considered to be safe by the FDA and is used in food, health, and cosmetic products, a LOGIC representative told Business Insider in an email.

With the great preponderance of different styles and brands of e-cigarettes out on the market, it is also difficult to study, since any one brand may have different ingredients or nicotine levels. These levels are sometimes higher than those in a tobacco cigarette.

Will they help you quit?

A recent study published in the journal Addiction in May 2012, showed that "electronic cigarettes can deliver clinically significant amounts of nicotine and reduce cigarette abstinence symptoms and appear to have lower potential for abuse relative to traditional tobacco cigarettes, at least under certain laboratory conditions."

The researchers brought 20 current cigarette smokers into the lab and had them test out e-cigarettes under laboratory conditions. They were then offered the choice of e-cigarette puffs, regular cigarette puffs, or money.

They tested the Vapor King from Vapor4Life in “WOW Cowboy” or “WOW Cowboy Menthol.”

The problem? It took new users 40 puffs of the e-cigarettes to get a good, consistent nicotine delivery — and the effects weren’t as fast or strong as a regular cigarette. They suggest this is because the vaporized nicotine entered the blood stream through the cheek instead of entering through the lungs as tobacco cigarette smoke does.

Experienced electronic cigarette users may be better at using them, however, and could get higher and faster nicotine levels with e-cigarettes, maybe on par with those from a tobacco cigarette, the study said.

Another report by the same researchers, published in February of 2012 in the journal Nicotine & Tobacco Research indicates that this could be true: Experienced e-cigarette smokers had higher nicotine levels and heart rates after they started inhaling nicotine, so they were basically better at smoking the e-cigarette and reliably got the nicotine high they were looking for, about equivalent to smoking tobacco cigarettes.

If the e-cigarettes are able to substitute for the tobacco cigarettes, it’s possible that one could use them to quit: first weaning yourself off of the tobacco, then off the nicotine inhaler, since it’s less addictive than the tobacco.

"We acknowledge that nicotine is an incredibly addictive drug and only advocate using Eonsmoke electronic cigarettes responsibly and by adult smokers only," Tolmach said. "We do not make any therapeutic or medical claims and consider the electronic cigarette as an unhealthy addiction."

Taking over?

Investment bank Citi named e-cigarettes as one of 10 technologies that will change the way the world does business.

A potentially cancer-free cigarette — despite all other concerns — is that big of a deal.

Citi projects $3.2 billion in global sales by 2015, up from $416 million in 2010.

While that's a huge market, however, it remains only a fraction of the global tobacco market, estimated at $700 billion in 2011. Whether e-cigarettes take a larger share will depend on many factors, including improved quality and unresolved questions about health.