Vapers-or e-cigarette smokers-aren't any safer from developing addiction, finds a new study released Thursday.

The basis of the pro-vaping argument has been that e-cigarettes don't contain the harmful chemicals in and byproducts of tobacco cigarettes.There's nicotine, to be sure, but not all nicotine is the same. Vaping proponents have said that the type found in cigarettes is a highly addictive form, and the type of nicotine in e-cigarettes is less addicting.

But a new study, published in the American Chemical Society'sChemical Research in Toxicology, indicates that nine out of 17 common, commercially available e-cigarettes contained the most addictive kind of nicotine.

Critics have long held that e-cigs contain ingredients that make themessentially a cigarette in terms of addictive power. There is also evidence that e-cigs may not be an effective means to quitting (some research shows that 75% of Americans who vape also smoke).

Three-quarters of U.S. adults favor raising the minimum tobacco age of sale to 21 years, including seven in 10 smokers, according to a new government study.

Support for raising the minimum smoking age was strongest among older adults and those who never smoked, HealthDay reports. The study found 11 percent of adults strongly oppose raising the smoking age to 21, while 14 percent said they were somewhat opposed. The study appears in the American Journal of Preventive Medicine.

"Raising the minimum age of sale [of tobacco products] to 21 could benefit the health of Americans in several ways," Brian King of the Center for Disease Control and Prevention's Office on Smoking and Health, said in a news release. "It could delay the age of first experimenting with tobacco, reducing the likelihood of transitioning to regular use and increasing the likelihood that those who do become regular users can quit."

In June, Hawaii became the first state to pass a law raising the legal smoking age to 21. The law also outlaws the sale, purchase or use of e-cigarettes for anyone under 21. The measure will take effect on January 1, 2016.

The Institute of Medicine issued a report earlier this year that concluded if every state were to immediately ban tobacco sales to those under 21, the smoking rate would fall 12 percent. The decrease would prevent 249,000 premature deaths among the generation born between 2000 and 2019, the report noted.