A two-story house has peeling paint and no yard. Behind it loom industrial smokestacks. Mark R. Cullen, M.D. ’76, HS ’79, professor of medicine and of epidemiology and public health, and director of the Yale Occupational and Environmental Medicine Program at the School of Medicine, used a photograph to frame a lecture in March at the School of Forestry & Environmental Studies. Do children in that house face health risks because of toxins from factories and lead from peeling paint or because they live in an overcrowded, high-crime neighborhood with a crummy school and no recreational facilities?Environmental epidemiologists focus on the physical environment, while social epidemiologists look at patterns of psychological and social stress. Both inquiries, Cullen said, are too narrow. “Neither side explains it all.” Historically, however, the two fields haven’t shared information. Cullen says researchers need to “deal with their agendas in tandem,” because that’s the only way to get a full understanding of a population’s health status. That knowledge can lead to the creation of such initiatives as more recreational space on the street or tougher air pollution standards, which will better address health issues.