On Thursday, the U.S. Food and Drug Administration (FDA) flexed its regulatory muscles and extended its authority over more tobacco products, including the highly debated electronic cigarettes, or e-cigarettes. In the announcement, the agency said it now has jurisdiction over items that meet the statutory definition of tobacco products—which includes e-cigarettes, pipe tobacco, and hookah tobacco, among others. The FDA says it also plans to crack down on e-cigarettes by proposing a ban of their sale to people under 18 and by requiring health warnings on packaging.  The UK already has stiff regulations on e-cigarettes and some cities in the U.S., like Los Angeles, have banned them in several public places. The trouble with e-cigarettes is that they are so new, and there’s not enough evidence to definitively determine either how effective they are at helping people quit smoking—or the health risks associated with inhaling vaporized nicotine. Here are five things we are still scratching our heads over.  1. Do e-cigarettes actually help people quit—or are they a gateway for new smokers? Some e-cigarette brands claim that they can help people wean themselves off regular cigarettes by supplying would-be quitters with nicotine (but without the carcinogens in conventional cigarette smoke). However, recent research is questioning whether they really help people quit. A recent study published in the journal JAMA Internal Medicine looked at self-reports from 949 smokers–88 of whom used e-cigarettes at the start of the study–in order to determine if e-cigarettes were helping people kick or cut back on nicotine. Researchers found that e-cigarettes did not help people quit, concluding, for now at least, that the case for e-cigarettes as a cessation tool is flimsy at best. (The study size was small, signaling a need for more research.)  There’s also the worry that e-cigarettes are tempting people into trying the real thing. Another study published in March found that adolescents who use e-cigarettes are more likely to smoke other tobacco products and regular cigarettes, which suggests that e-cigarettes are not always the lesser of two evils, but instead, just another vector for nicotine exposure. According to data from the National Youth Tobacco Survey, the percentage of middle school and high school students who have tried e-cigarettes doubled from 3.3% in 2011 to 6.8% in 2012. Of course, there are still not enough studies to reach a firm conclusion that e-cigarettes make people more likely to smoke tobacco—and the FDA says this is not yet determined.  2. How dangerous is liquid nicotine? The health risks associated with the liquid nicotine used in e-cigarettes are not fully understood. A recent New York Times article found that the liquid could be linked to poisonings; the number of poisonings linked to e-cigarette liquids rose to 1,351 in 2013, which is a 300% increase from 2012. The CDC also released a report earlier this month that showed what they called a “dramatic” rise in e-cigarette-related calls to U.S. poison centers. The spike went from one call a month in September 2010 to 215 calls a month in February 2014. Over half of the calls involved kids age five and under, and 42% involved people ages 20 and older. Known symptoms of liquid nicotine ingestion include vomiting, nausea, and eye irritation.  3. Are the vaporizers safe? Though the numbers are small, there have been a few cases of e-cigarettes exploding and harming users and the people around them. E-cigs contain a small lithium battery that heats up the liquid inside. The liquid is made up of nicotine dissolved in a colorless liquid called propylene glycol, with added synthetic flavor and sometimes dyes. When an e-cigarette exploded in a Florida man’s face, Thomas Kiklas, co-founder of the Tobacco Vapor Electronic Cigarette Association, told the Associated Press that the industry does not know of issues with the cigarettes or batteries exploding.  4. Is propylene glycol dangerous? Propylene glycol is a a clear, colorless liquid that becomes vapor when it’s heated. It can also be found in food, cosmetics, and pharmaceutical products, and the small amounts people are typically exposed to are largely believed to be benign. However, it’s uncertain whether inhaling propylene glycol could come with unique health risks. “As for long-term effects, we don’t know what happens when you breathe the vapor into the lungs regularly,” Thomas Glynn, the director of science and trends at the American Cancer Society told ABC News. “No one knows the answer to that.”  5. Can you get addicted to e-cigarettes? As the FDA says, nicotine is “highly addictive.” The FDA says they still don’t know how much nicotine or other potentially harmful chemicals are being inhaled during e-cigarette use. Therefore, it’s hard to tell how much or little damage is being done.
The FDA has cracked down on e-cigs by asserting its regulatory power and proposing a ban on sales to minors