E-cigarettes, or vaporizer pens, now have a thriving, growing and vulnerable new market here in Broward County and greater South Florida. Teens looking to experiment with drugs are increasingly using these battery-operated devices, often touted as a healthier alternative to traditional cigarettes, to vape synthetic substances like flakka (an amphetamine-like drug similar to bath salts) and various forms of “legal weed” (such as K2 and Spice). And that has local law enforcement and health officials worried. Inhaling liquid nicotine is one thing, but vaping other less familiar and potentially more dangerous substances is another, they say. And parents of teens — especially — need to be on the alert.