Regarding Dont ban e-cigs; theyre not harmful (Letters, April 29): The writer ridiculed the idea of a ban on e-cigarettes, citing zero harmful effects and saying users only exhale water vapor. Hes wrong. E-cigarettes are designed to deliver nicotine, a potent and addictive alkaloid. As little as 30 milligrams (less than what is contained in two packs of conventional cigarettes) can kill an average adult. How much is in an e-cigarette? Theres no way to tell, since theyre unregulated and no way to know what else has been added to the water e-cigarette users inhale. Nicotine took both of my parents, who died of lung cancer. I dont want to join them. E-cigarette users should keep their poison to themselves!