There's no evidence that any of the ingredients of e-cigarette vapour are significantly carcinogenic. That may well continue to be true; there is no natural law

There's no evidence that any of the ingredients of e-cigarette vapour are significantly carcinogenic. That may well continue to be true; there is no natural law saying that a habit you dislike must be carcinogenic. There are many possible formulations of e-cigarette liquid, with the only common factor being nicotine. We are extremely confident that nicotine isn't carcinogenic, although it may cause mild cardiovascular harm. If we find out that some of the other ingredients in e-cigarette vapour are toxic or carcinogenic, the industry will voluntarily stop using those ingredients immediately; they already did so with diacetyl.