Sales of e-cigarettes, which emerged on the U.S. market less than 10 years ago, are booming, reaching an estimated $2.2 billion in 2014. But very little is known about their potential health risks or benefits. Scientists, health advocates, regulators and lawmakers are struggling to weigh the potential promises and threats of the popular products, according to an article in Chemical & Engineering News (C&EN), the weekly newsmagazine of the American Chemical Society.