According to a new study that observed sea, rock and lake salts, 90 percent of the table salt brands sold around the world contain microplastics. Several years ago, researchers discovered that microplastics were in sea salt, but no one was certain just how extensive the problem was until now. National Geographic reported that researchers in South Korea and at Greenpeace East Asia tested 39 salt brands, and 36 of them contained microplastics.