During the past several decades, philosophers of science and scientists themselves have become increasingly aware of the complex ways in which scientific knowledge is shaped by its social context. This awareness has called into question traditional notions of objectivity. Working scientists need an understanding of their own practice that avoids the naïve myth that science can become objective by avoiding social influences as well as the reductionist view that its content is determined simply by economic interests. A nuanced perspective on this process can improve research ethics and increase the capacity of science to contribute to equitable public policy, especially in areas such as environmental and occupational health, which have direct implications for profits, regulation, legal responsibility, and social justice. I discuss research into health effects of the 1979 accident at Three Mile Island near Harrisburg, Pennsylvania, USA, as an example of how scientific explanations are shaped by social concepts, norms, and preconceptions. I describe how a scientific practice that developed under the influence of medical and nuclear physics interacted with observations made by exposed community members to affect research questions, the interpretation of evidence, inferences about biological mechanisms in disease causation, and the use of evidence in litigation. By considering the history and philosophy of their disciplines, practicing researchers can increase the rigor, objectivity, and social responsibility of environmental health science.