Brian Collins tried everything, from patches to gum to going cold turkey. But nothing worked to help him kick his 20-year smoking habit.

"I just ...  I have a very strong addiction to cigarettes," he said.

Collins is 39, and trying to quit has been tough for a guy who started smoking at the age of 16. Enter the e-cigarette.

"It kind of replicates the sensation of smoking a cigarette," Collins said.

Collins is hoping this electronic device could finally help him stop smoking for good. But as for whether e-cigarettes could be a solid harm-reduction tool, a weapon against smoking — not everyone's on board. E-cigarettes' young and evolving technology, plus the tobacco's marred history with harm reduction, have placed these devices in the middle of a big scientific debate.

In the United States, that has meant increased regulations in recent months as researchers try to learn more. Meanwhile, smokers like Collins are left on their own to figure out how to use the devices to quit smoking for good.

A pharmacist in China is credited with inventing the first commercial electronic cigarette in 2003. When early models hit the U.S., Collins was on it, but they didn't work for him. The later versions did. Collins' own orange-and-black one looks more like a futuristic inhaler than a traditional cigarette. It's a mini vaporizer containing parts that essentially heat up and turn liquid, or what's called "juice," into a vapor that can be inhaled through a mouthpiece.

Collins even crafted his own plan to wean himself off of nicotine and then e-cigarettes entirely. He started out vaping liquid containing 12 milligrams of nicotine in it, which is the addictive agent in tobacco and cigarettes. "I'm at 3 milligrams," he said. "So I'm making my way down there."

Already, Collins hasn't lit up a real cigarette in more than a year. His lung capacity has increased significantly, he says, and his blood pressure has returned to normal.

"I just feel healthier overall," he said.

Tobacco's fallout with harm reduction

Collins is but one story. Anti-tobacco advocates have their eye on broader population trends, and they've long been weary of 'safer' cigarette substitutes as viable options for reducing the harms of smoking.

Virginia Berridge thinks that for many, the fallout from decades ago is still raw. She has been studying tobacco in the context of harm reduction as director of the center for history in public health at the London School of Hygiene and Tropical Medicine. The U.K. is a pioneer in the entire field of harm reduction, she says, which essentially aims to reduce the risks associated with drug use instead of the focusing on stopping it completely.

"There has been a much stronger element of maintenance of harm reduction by using drugs or by using drug substitutes [in the U.K.]," she said. "Which you haven't really got in the [United] States, where there's been a much more prohibitionist attitude, I think, toward substances."

This philosophy of reducing the risks associated with drug use as opposed to taking a "just say no" approach has been growing in popularity. Harm reduction first took off around the world amid the HIV/AIDS epidemic of the '80s and '90s, with the emergence of needle exchange programs. Instead of a total cessation approach, the idea was if people are engaging in potentially harmful behavior such as injecting drugs, they could focus on ways to reduce the risks through using clean needles to prevent the spread of HIV and Hepatitis C infections. The programs have succeeded in that aim, though they've been a tougher sell in the U.S.

The public health community similarly embraced harm reduction as an approach for cigarettes. In the '60s and '70s, they even teamed up with the tobacco industry in attempts to create "safer cigarettes." That led to low-tar cigarettes, lights, and filtered ones. But these alternatives were not a success. After much promise and hype, it turns out not only did they not work, they could be more damaging to a person's health.

"People were feeling that they'd been duped by the tobacco industry, which had collaborated in a program where they knew that things were actually or probably almost as harmful as before," said Berridge.

The public health community moved toward a total cessation approach to smoking. Replacement therapies like nicotine patches and gum instead came out of the psychiatric field, Berridge says. So fast-forward to the 2000s as the e-cigarette started gaining traction. It wasn't immediately embraced as a harm-reduction tool for smoking.

"This has become a really polarized sort of area," said Berridge.

Interpreting limited science

As Europe and the U.S. witnessed vape shops pop up left and right, doctors, scientists, and public health proponents had pressing questions: Could these e-cigarettes really be an effective substitute? And at a more elemental level, are they safe?

"I can't answer that question, simply because we don't have enough evidence," said Jaime Hartmann-Boyce, a health research at the University of Oxford who recently reviewed the research to date on e-cigarettes.

Hartmann-Boyce says the types of e-cigarettes and "juices" keep changing, making it all the more tricky to study them in a scientifically rigorous way.

"They haven't been around that long, so there are definitely particular questions about their long-term safety profile," she said. "And we honestly won't know the answer to that until they've been around for longer."

Still, she says, based on the small, randomized controlled studies that are out there, e-cigarettes do appear to help people quit, and limited research suggests they appear to be safer than regular cigarettes.

"I don't think there's anyone out there who's arguing that, compared to not using cigarettes and not inhaling anything that you're not supposed to inhale, electronic cigarettes are a good idea," she said. "But the thing about smoking traditional cigarettes is that they are really, uniquely deadly."

The Royal College of Physicians, the professional body for British doctors, is already advising smokers that e-cigarettes are a helpful way to quit smoking.

Advancing with caution

In the U.S., there's more caution.

"It's not a simple question of 'Are e cigarettes less harmful than other tobacco products?'" said Mitch Zeller, director of the Center for Tobacco Products at the U.S. Food and Drug Administration.

Zeller says people need to keep the bigger picture in mind.

"The public health impact of e-cigarettes — good, bad, or otherwise — really comes down to answers to two fundamental questions," he said. "Who are using the products, and how are they being used?"

He worries that e-cigarettes could be a Trojan horse, renormalizing smoking and giving rise to a whole new generation of young smokers. A federal survey found that e-cigarette use among high school students shot up from about 1.5 percent in 2011 to 13 percent in 2014. He wants more evidence on whether e-cigarettes are helping people quit, as opposed to serving as "nothing more than a bridge" between regular cigarettes.

"There's no question that there might be a bunch of Brians out there. I know that anecdotally just from conversations out there I've had, but the key word was anecdotatlly," said Zeller. "The Preventive Services Task Force has concluded that the evidence is not sufficient to support e-cigarettes as approved cessation aid."

Plus, he doesn't want to make a mistake similar to when the world prematurely accepted low-tar and filtered cigarettes as an answer.

"The science is evolving, and anybody who says the answers are in and e-cigarettes are fundamentally dangerous, or the answers are in and e-cigarettes are fundamentally safe, are ignoring the current state of play, which is we need more science," he said. "We have questions in need of answering."

In the meantime, Zeller's federal agency has come down on vaporizers and e-cigarettes in recent months. They can't be sold to minors and are now considered tobacco products, meaning they have to go through a government review. That includes small shops and manufacturers that do things like create their own liquids. Warning labels are in the pipeline. Meanwhile, his agency is overseeing dozens of independent studies to learn more.

But these stricter regulations have vapers like Brian Collins worried.

"They're starting to destroy businesses that people have created to help other people get away from analogues to the digital cigarette," he said.

Collins believes only the bigger tobacco companies will have the resources to navigate the approval process, crushing the smaller independent guys. And while he recognizes the science isn't in yet and would like more research done on e-cigarettes, he's adopting his own harm-reduction attitude.

"In the meantime, if I can choose between inhaling four chemicals over the thousands of chemicals in cigarettes, I'll take the four chemicals every day," he said.