Epidemiology is the study of the distribution and determinants of disease in populations. Diseases are not randomly distributed in populations, and there are certain risk factors that influence diseases. The Ph.D. in environmental health, with a specialization in epidemiology, provides a comprehensive and advanced background in theoretical and applied quantitative epidemiology as well as substantial expertise related to each student's research topic. The Department of Environmental and Radiological Health Sciences is home to one of the largest environmental health programs in the nation, and the only one that incorporates radiological health into its core curriculum. Students and researchers in environmental health investigate how natural and built environments affect human and animal health and seek solutions to minimize negative health consequences of environmental and workplace exposures. Radiological health has a long tradition at CSU focused on the biological effects of radiation, including laboratory studies of the damaging effects of radiation, and clinical uses of radiation in diagnostic imaging and cancer therapy.