Despite the dangers, many American adults and teens still use tobacco products, a new study finds.

Researchers looked at more than 46,000 people and found that 28 percent of American adults currently use some form of tobacco, while 9 percent of teens said they used tobacco in the past month.

Tobacco products included cigarettes, cigars, cigarillos, filtered cigars, pipe tobacco, hookahs, snus pouches and other smokeless tobacco.

Even more worrisome, 40 percent of tobacco users turned to more than one product, with cigarettes and e-cigarettes being the most common combination, the researchers said.

"We know with certainty that cigarette smoking is incredibly harmful," said lead researcher Andrew Hyland. He is chairman of the department of health behavior at Roswell Park Cancer Institute in Buffalo, N.Y.

"Cigarette smoking is responsible for 480,000 deaths in the U.S. each and every year, but getting completely off cigarettes quickly leads to improved health," he said.

According to the study, cigarette smoking continues to remain the most common form of tobacco use, Hyland said.

E-cigarettes trailed only cigarettes in popularity for both youths and adults, and hookah (waterpipe) smoking was very high among 18- to 24-year-olds, he added.

Among adults, 23 percent smoked cigarettes and 7 percent of those smokers also used e-cigarettes. Among kids aged 12 to 17, just over 13 percent smoked regular cigarettes, while 11 percent used e-cigarettes as well, the researchers found.

"Another surprising finding was that about four in 10 youth and adult tobacco users reported being current users of two or more tobacco products," Hyland said.

These statistics serve to help identify areas where additional tobacco regulation may be needed, he said.

The report was published Jan. 26 in the New England Journal of Medicine.

This study underscores the importance for fully implementing the Tobacco Control Act, said Erika Sward, assistant vice president for national advocacy at the American Lung Association.

"The act specifically tasks FDA with looking at tobacco use and whether or not certain products or actions by companies would cause people to switch instead of quit," she said. "These findings call into question any positive impact e-cigarettes might have on public health," Sward said.

The lung association is concerned about people using both cigarettes and e-cigarettes, she added.

"We recognize that in many ways, at least for the larger tobacco companies, e-cigarettes are a way for people to keep using their 'cash cow' product, which is regular cigarettes," Sward said. "It's another way to discourage smokers from ending their tobacco addiction for good."

Gregory Conley, president of the American Vaping Association, said these findings have been available for two years or longer, but the U.S. Food and Drug Administration has been dragging its heels when it comes to its mission to regulate tobacco products, including e-cigarettes.