You have more friends than you think. Human bodies are home to a variety of parasites, many of them associated with pollution, like dirty drinking water. Dr. Elmer Koneman, professor emeritus in the Department of Pathology at the University of Colorado School of Medicine, was nice enough to help us peel back some of the layers for this show.
The idea here is to go from head to toe, looking at critters that should give you some appreciation for the need for environmental protection. This picture is from the middle of the human body -- roundworms that hang out in the small intestine. It's shown here as a harbinger of things to come.
Credit: U.S. Centers for Disease Control and Prevention.