Many consider electronic cigarettes (e-cigs) to be a positive aid in the cessation of conventional tobacco-burning cigarettes. However, a recent meta-analysis study published in the International Journal of Public Health reported no significant difference in the efficacy of using nicotine e-cigs to stop smoking tobacco-burning cigarettes when compared to other therapies or placebo.

The group from the Department of Clinical Epidemiology and Biostatistics at McMaster University in Ontario, Canada, looked at 569 publications, but only five fit criteria established for inclusion. They concluded that large higher-quality studies should be undertaken in order to guide public policy.

While the upside of e-cigs requires further study, the downside is being recognized and warrants further attention. Growing numbers of middle school children and high school teenagers are finding e-cigs appealing and reporting to have smoked e-cigs.

Part of the appeal is the flavoring that is in many e-cig products. New and existing flavored tobacco and nicotine products are heavily marketed, and they have an appeal to youths.

The Centers for Disease Control and Prevention (CDC) and Food and Drug Administration (FDA) are concerned this is contributing to recent increases in tobacco product use among youths. The inhaling of flavored e-cigs instead of smoking conventional cigarettes may be trading one form of serious threat to health for a different — but still detrimental — threat to health.

Many of the flavorings used in e-cigs are considered safe when consumed as a food product, but that does not mean they are safe when inhaled. Several recent studies should cause concern.

Benzaldehyde, a common ingredient in natural fruit flavors for e-cigs, has been shown to create irritation in the airways in occupational exposure studies. An animal model has shown volatile benzaldehyde to be associated with gastrointestinal disease and lung cancer.

Another study looked at workers who had handled flavoring products over many years and found permanent lung disease. However, cherry-flavored e-cigs have the highest concentration of benzaldehyde, and it is considerably lower than the levels measured in the workplace of flavor workers.

A different study did not identify any health problems among flavor workers inhaling benzaldehyde. For some, this is reassuring. This same study also failed to find health issues related to diacetyl — a chemical associated with popcorn flavoring that is in e-cigs.

Still, other studies disagree. An irreversible lung disease, bronchiolitis obliterans, was found to be associated with the inhalation of diacetyl and was first identified in workers at a microwave popcorn company. Diacetyl has been found in 39 of 51 of the popular flavors of e-cigs identified to be popular among youth smokers.

Over 90 percent of the e-cigs tested had some sort of flavoring considered to be of concern. The concerns over the short- and long-term health consequences of youths smoking e-cigs are not isolated to the obvious risk for nicotine addiction, but the impact on developing vulnerable lungs.

The CDC sees the use of e-cigarettes as a serious problem and states: "Given the millions of current youth tobacco users, it is important for comprehensive tobacco prevention and control strategies to address all forms of tobacco use, including flavored tobacco products, among U.S. youths."