John Wargo has written and taught on the limits and potential of environmental law, with a focus on human health. In his research he has compared the history of five serious and global environmental threats to children’s health in the twentieth century: nuclear weapons testing, pesticides, hazardous sites, vehicle particulate emissions, and hormonally active ingredients in plastics. He has also presented a history of law and science governing pesticides with special attention to the vulnerability of infants and children, and participated in the design of federal and state laws and regulations intended to reduce human exposures to air pollution, pesticides, plastics, metals, mercury, wood smoke, diesel exhaust, flame retardants, and endocrine-disrupting chemicals.