E-cigarette users’ pee contains more heavy metals as well as signs of exposure to carcinogens and other irritating chemicals than the pee of non-vapers, hinting that the habit might come with serious health risks. At the same time, vapers who switched completely from cigarettes still had lower levels of these substances in their urine than their smoking peers [...] researchers led by Maciej Goniewicz [...] analyzed questionnaires and urine samples submitted by more than 5,100 people between 2013 and 2014 to try to spot patterns of chemical exposures in their pee.