The main reason it’s so hard to say whether e-cigarettes are safe is that they haven’t been around long enough to know. It took decades for the risks of tobacco cigarettes to emerge, and nobody knows yet what the long-term effects of “vaping” will be. If you’re trying to give up real cigarettes, stick with better-studied methods: nicotine gum, patches and counseling. And if you don’t smoke, don’t start with e-cigs just for fun.