Current smokers are several times more likely than nonsmokers to try using e-cigarettes, according to a new study published in the American Journal of Public Health.

The study found 40 percent of Americans have heard of e-cigarettes and more than 70 percent believe they are less harmful than regular cigarettes, according to CSPNet.com. The study was conducted by Legacy, a public health group that advocates for tobacco prevention and cessation services.

“Given the poor quality control of these products, consumers are taking unknown risks by using e-cigarettes, with little proven new benefits,” David Abrams, PhD, Executive Director of the Schroeder Institute at Legacy, said in a news release.

Some states are considering laws to regulate e-cigarettes.

E-cigarettes are designed to deliver nicotine in the form of a vapor, which is inhaled by the user. They usually have a rechargeable, battery-operated heating element, a replaceable cartridge with nicotine or other chemicals and a device called an atomizer that converts the contents of the cartridge into a vapor when heated. E-cigarettes often are made to look like regular cigarettes.

Annual sales of e-cigarettes have grown to between $250 million and $500 million in the United States. That is still a small percentage of the estimated $100 billion U.S. tobacco market.

Public health groups say not enough is known about the health effects of e-cigarettes. They are also concerned e-cigarettes, which come in flavors such as cherry, chocolate and piña colada, are attractive to youth.

The U.S. Food and Drug Administration (FDA) announced in April 2011 that it would regulate smokeless electronic cigarettes as tobacco products, treating them the same as traditional cigarettes. The FDA said it would not try to regulate e-cigarettes under stricter rules for drug-delivery devices. In 2010, the FDA lost a court case after it tried to treat e-cigarettes as drug-delivery devices, which must satisfy stricter requirements than tobacco products, including clinical trials to prove they are safe and effective.