Scientists from the Roswell Cancer Park Institute in Buffalo, NY, have announced the findings of two studies respectively looking at evidence on "thirdhand" exposure to nicotine from e-cigarettes and the accuracy of e-cigarette product labels.

Sales of e-cigarettes ("electronic cigarettes") - where nicotine and other cigarette-associated substances are inhaled in a vapor through a battery-operated device - have doubled each year since 2008 in the US. E-cigarettes are not currently regulated by the US Food and Drug Administration (FDA).

Over the past couple of years, various studies have analyzed to what extent e-cigarettes may or may not be harmful to both the smoker and other people.

Medical News Todayreported on a 2012 study finding that, although e-cigarettes contribute less to indoor air pollution than traditional tobacco cigarettes, they are "not entirely emission-free," and so bystanders may be exposed to the released vapor.

That study also criticized the labeling of e-cigarettes, commenting that the inadequate or vague information on the content of the products made it difficult for smokers to know the potential dangers of the contained substances.

E-cigarettes and thirdhand smoke risk

Examining the issue of bystanders' exposure to nicotine from e-cigarettes, the Roswell Park Cancer Institute (RCPI) researchers studied the extent to which e-cigarettes left a nicotine residue on indoor surfaces. This residue is often referred to as "thirdhand smoke."

To do this, the scientists vaporized the contents of three different brands of e-cigarette inside a special chamber. The floors, walls, windows, wood and metal surfaces of the chamber were then individually checked for nicotine levels.

In three out of four of these experiments, the researchers found varying but significant increases in nicotine residue, with the floor and windows of the chamber retaining the highest amounts of residue.

How accurate is the product labeling of e-cigarettes?

The second study from the RCPI team assessed how accurate the product labeling of e-cigarettes is. The researchers analyzed the contents of 32 e-cigarette refill solutions and compared their findings with the claims made by the product manufacturers in their labeling information.

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In e-cigarettes, nicotine and other substances are inhaled in a vapor through a battery-operated device.

They found that the nicotine concentration of 1 in 4 products differed by more than 20% from what the amounts advertised on their labels. Nicotine was also found in some refill solutions that were labeled as being nicotine-free.

"Research conducted by Roswell Park scientists provides a valuable contribution and insight into the content and marketing of e-cigarettes," says Andrew Hyland, PhD, chair of RPCI's Department of Health Behavior.

"This science can inform health policy organizations as they determine e-cigarette regulations, which can and should include smoke-free policies and standards for accurate labeling," he adds.

"The public health community agrees that more scientific inquiry is needed to understand the potential health impact of e-cigarettes," adds Dr. Maciej Goniewicz, who presented the findings of both studies at the annual meeting of the Society for Research on Nicotine and Tobacco on February 8th, 2014.

Dr. Goniewicz adds:

"These studies add to the growing body of scientific evidence that will help to define and delineate a product that is broadly used indoors and is advertised and sold without restrictions."