In the past decade, scientists have been finding evidence of microplastic particles throughout the human body, including the brain and blood, the cardiovascular system, the liver, kidneys, stomach, lungs, even the testicles, and the placenta. In the last three years, Kara Meister, an assistant professor of otolaryngology-head and neck surgery at Stanford University, has been collecting tonsils she removed from children—and found microplastic particles in all of them.