E-cigarettes, viewed by some users as a less harmful alternative to traditional tobacco products, nonetheless expose young people to the effects of nicotine and present a public health concern, U.S. Surgeon General Vivek Murthy said in a nearly 300-page report published Thursday.

"Although e-cigarettes generally emit fewer toxicants than combustible tobacco products, we know that aerosol from e-cigarettes is not harmless," Murthy said in the report. "Although we continue to learn more about e-cigarettes with each passing day, we currently know enough to take action to protect our nation's young people from being harmed by these products."

Risks of nicotine exposure in young adults include lower impulse control, attention deficits, mood disorders and priming for the use of other addictive substances, according to the Surgeon General's report.

"Nicotine, regardless of its source, is highly addictive and has clear neurotoxic effects especially on the developing brains of adolescents and even into young adulthood," Dr. Benard Dreyer, president of the American Academy of Pediatrics, said at a press conference yesterday.

The report may have an effect on sales at big tobacco companies such as Reynolds American (RAI) and Altria(MO) - Get Report , who are among the largest makers of e-cigarettes.

E-cigarettes vaporize liquids that typically contain nicotine, flavoring and other additives. A 2015 report by Public Health England claimed that e-cigarettes are 95% safer than smoking traditional tobacco products, but their inclusion of nicotine, which comes from tobacco, is cause for some skepticism.

Among middle school and high school students who use tobacco products, e-cigarettes were the most popular in 2015, outranking cigarettes, hookahs, smokeless tobacco, cigars, pipe tobacco and bidis, according to the Centers for Disease Control and Prevention.

Their popularity among this demographic is likely driven by the novelty of the products and a lack of information about their adverse health effects, said Vince Willmore, VP of communications at the Campaign for Tobacco Free Kids.

"A lot of these kids may think they're just inhaling water vapor when that's not the case," he said. "They could also be inhaling nicotine and other harmful chemicals, so this report really plays an important role in educating parents, teachers and youth about the real risks of e-cigarettes."

E-cigarettes were largely unregulated until the FDA finalized a rule that went into effect in August that prohibits sales to anyone under 18 and subjects all products to FDA approval.

The Surgeon General's policy recommendations are stricter, and include the regulation of e-cigarette marketing, prevention of adolescents' access to the products and an increase in prices. The report also condemns the use of enticing flavors and flashy marketing campaigns, claiming that both have played a large part in the recent popularity of e-cigarettes among youth.

"The report finds that the use of sweet flavors is a leading factor in use of e cigarettes," Willmore said. "It also shows that e-cigarette companies abuse marketing campaigns right of the playbook of the tobacco industry."

That's not surprising given the hold the big tobacco companies have on the e-cigarette market.

Reynolds American's Vuse brand of e-cigarettes is the most popular in America with 35.7% of the market, according to November Nielsen data cited by Wells Fargo analysts. Altria's MarkTen XL e-cigarette has a 15.5% share of the market due in part to distribution gains, the analysts said.

The Wells Fargo analysts believe that competition will intensify as the FDA begins to regulate the industry, but Ray Story, CEO of the Tobacco Vapor Electronic Cigarette Association, claims that the regulations make it unlikely that these big companies will soon be dethroned.

"By allowing regulation to be so strict - as it is currently - to where only big tobacco can play in this arena where they make everything so expensive and difficult for products to be sold legally, that right there only benefits big tobacco but it stifles growth," Story said. "Big tobacco will control [the e-cigarette market], and all the smaller players will basically be pushed out of the market."