Over the last decade, e-cigarettes have become a $1.5 billion industry. Yet the research on their safety has been scant. The benefits and risks of e-cigarettes are currently being studied, but their popularity has far outpaced the science.
“We should focus on evidence, not theories,” said Dr. Stanton Glantz, a professor in the department of medicine and director of the Center for Tobacco Control Research and Education at UC San Francisco.
A major hurdle in studying e-cigarettes is the fact that there is no standardization across manufacturers; one product is vastly different from the next. However, Glantz said that research does show that they are not harm-free.
Here we compare the ingredients in traditional cigarettes versus e-cigarettes and outline some of the health research.
Traditional cigarettes contain tobacco along with a number of additives to enhance the taste and feel of a cigarette. The use of tobacco is a risk factor for a number of diseases and cancers, and, according to the World Health Organization, is the worldwide leading cause of preventable death.
E-cigarettes do not contain tobacco. Instead, liquid nicotine is heated and vaporized. When a person puffs through the device, the nicotine and flavoring are inhaled as a vapor, similar to the vapor in a fog machine. Studies show the vapor may contain propylene glycol, glycerol and other chemicals that may be associated with respiratory function impairment.
Nicotine is the addictive stimulant found in cigarettes. The amount of nicotine in cigarettes varies by brand, type of cigarette and country of origin. In the United States, a pack of cigarettes contains between eight and 20 milligrams of nicotine. That’s not how much nicotine actually enters the bloodstream, though. When cigarette smoke is inhaled, the nicotine is absorbed through the smoke and roughly one mg is absorbed in the body.
The nicotine in e-cigarettes also varies widely. A 2014 study in the journal Tobacco Control reported that nicotine levels in e-cigarettes range from zero to 34 mg/mL. And the amount of nicotine that gets absorbed in the body is significantly lower than that of regular cigarettes. In a 2013 study published in Nicotine & Tobacco Research, researchers analyzed nicotine levels in vapor from 16 electronic cigarette brands popular in Poland, the U.K. and the U.S. The total level of nicotine generated with a smoke machine that simulated puffing conditions varied from 0.5 to 15.4 mg.
Chemicals in the Flavoring
Electronic cigarette cartridges are available in a variety of flavors that are made using different levels of chemicals. Two chemicals that make up the flavors are diacetyl and acetyl propionyl, which are used to add butter flavoring in products such as microwave popcorn. Although safe for use in food, these toxins have been known to irritate the respiratory tract when inhaled, according to the CDC. In a 2014 study in Nicotine & Tobacco Research, Dr. Konstantinos Farsalinos from the Onassis Cardiac Surgery Center in Athens, Greece, and colleagues tested 159 sweet-flavored e-liquids for the presence of diacetyl and acetyl propionyl. Researchers found that 74.2% of samples contained either of the chemicals, although on average the levels were slightly lower than safety limits established by the National Institute of Occupational Safety and Health, a part of the CDC. More than 40% of the samples, however, did contain levels above the safety limit: the highest amount of diacetyl in samples was almost 500 times higher than safety limits and the highest level of acetyl propionyl was 22 times higher.
Researchers noted that although these chemicals are present in tobacco cigarettes, they are produced during the combustion process and not used as ingredients. Because diacetyl and acetyl propionyl are used as ingredients in sweet-flavored e-cigarettes, they represent an avoidable risk. Authors of the study hope that the e-cigarette industry will take steps to make the products safer by removing this risk.
Particulate Metals and Organic Compounds
Along with higher levels of certain chemicals, research shows that e-cigarettes also contain higher levels of certain metals. Constantinos Sioutas, Fred Champion professor of environmental engineering at USC, and colleagues found that despite a 10-fold decrease in exposure to harmful particles, e-cigarettes contained four times the amount of nickel than traditional cigarettes. Human studies on nickel show that exposure to the industrial chemical increases the risk of lung and nasal cancers. Chromium was also found in secondhand smoke from e-cigarettes. The metal, absent from tobacco cigarettes, can cause coughing and shortness of breath as a result of acute exposure, according to the Environmental Protection Agency. Researchers also found amounts of lead and zinc, although these were lower than levels in tobacco cigarettes.
Sioutas said that elevated levels of nickel in e-cigarettes come from the metal atomizer in the cartridge that is used to vaporize the solution of nicotine. “Nickel is not a nice thing to breathe,” he said. “[E-cigarette] companies could make an effort to replace the material that heats up the liquid to one that is more benign since most of the toxic substance that comes from e-cigarettes comes from this heated element.”
While researchers continue to study the effects of e-cigarettes on populations, it’s important to know that there are risks associated with e-cigarettes, and that they can become just as addictive as tobacco cigarettes.
“A little less toxic puff for puff doesn’t matter,” Glantz said. “The big adverse health consequence is that it keeps people smoking.”