Nicotine, in many ways like caffeine, affects the cardiovascular system, but calling such effects "issues" in healthy users is unwarranted (heart healthy). According to some sources, tobacco cigarettes contain thousands of ingredients (even by the lowest numbers, significantly more than eliquid, also known as juice), with many of those being known carcinogens. Meanwhile, eliquid typically contains just a handful of ingredients. Assuming eliquid is sourced from reputable vendors and contaminant free, the primary causes for concern are the flavorings, most of which were developed for the food industry. The recent news about diacetyl in eliquid stems from daily occupational exposure at excessive doses in factories producing food products (volatile diacetyl exposure from butter popcorn can be many times greater than eliquids, if present). It was originally isolated from butter and gives thousands of products their creamy butter flavor, irrespective of whether nicotine is present.
