Connor became involved in community health and safety issues because he grew up behind the Raybestos Company, which made asbestos brake liners and emitted asbestos into his community. John watched as many friends and members of his community died due to their exposure to asbestos. He has a light dusting of asbestos in his lungs himself. In the 1970s, he led the fight with Massachusetts Fair Share for a state right-to-know law. In 1983, he helped to found the National Campaign Against Toxics Hazards (which grew into the National Toxics Campaign). He is formerly executive director of the National Toxics Campaign and has been one of the preeminent spokespersons for the nation's grassroots toxics movement.