Concerns about electronic cigarettes, including flavors and marketing that could appeal to young people, underscore the need to regulate the fast-growing industry, according to a congressional report released Monday.

The report (pdf) — written by the staff of Sens. Dick Durbin, D-Ill., and Tom Harkin, D-Iowa, as well as Rep. Henry Waxman, D-Calif., and other legislators — highlights several issues, including the lack of age restrictions and no uniform warning labels for the battery-powered devices that heat a liquid nicotine solution and create vapor that's inhaled.

The new report builds on growing national efforts to learn more about the potentially adverse effects of e-cigarettes. In September 2013, attorneys general of 41 U.S. states sent a letter to the Food and Drug Administration (FDA) urging the body to “take all available measures” to issue clear guidelines for the product, as its use has far outpaced regulatory efforts and the scientific community’s ability to conduct long-term studies.

While the FDA plans to set marketing and product regulations for e-cigarettes in the near future, for now, almost anything goes. A 2009 law gave the FDA the power to regulate a number of aspects of tobacco marketing and manufacturing, though it cannot ban nicotine or cigarettes outright. The agency first said it planned to assert authority over e-cigarettes in 2011 but hasn't yet. The proposed FDA regulation was submitted to the Office of Management and Budget for review in October.

"I can't understand why the FDA is taking this long," Sen. Durbin said in an interview with The Associated Press. "It is clear that the longer they wait, the more young people will be addicted."

The report follows an investigation launched by the congressional delegation in September into the practices of nine e-cigarette makers. The staffs surveyed the companies for information on their marketing practices, steps taken to restrict sales to minors, types of warning labels and claims of health benefits or reduced exposure to potentially harmful or addictive substances.

Among the findings, the report says six of the companies surveyed spent more than $59 million on advertising and promotion of their e-cigarettes in 2013. Several of the companies reported that between 2012 and 2013 their promotional spending more than doubled. Two of the companies' marketing expenses increased more than 300 percent during that time. Sales of e-cigarettes, which are sold under more than 200 brand names, are estimated to have reached nearly $2 billion in 2013.

Durbin said that if the agency "accepts responsibility for this product as they have for tobacco," it could start establishing standards for sales and marketing.

"If they fail to do that, I'm afraid it's going to continue reach into the ranks of our children," he said.

Harkin, chairman of the Senate Health, Education, Labor and Pensions Committee, echoed those concerns in a statement, urging regulators to stop marketing practices that are already illegal for traditional tobacco products.

E-cigarettes have become extremely popular and been touted as a safer alternative to, and a way to quit, regular cigarette smoking. A study published in September by The Lancet, a British medical journal, found that e-cigarettes were as effective as nicotine patches in helping smokers quit.

But some experts worry about potential side effects and whether the devices could actually encourage the use of cigarettes.

A study published last fall by the Centers for Disease Control found that teen use of e-cigarettes had more than doubled between 2011 and 2012, and that there was possibly a causal relationship between their use and regular smoking among children.

Meanwhile, outside of federal efforts to regulate e-cigarettes, a number of U.S. municipalities have moved to curb their use in public places. Earlier this year, both Los Angeles and New York City extended aspects of their existing smoking bans to e-cigarettes.

Al Jazeera and The Associated Press