Epidemiology is the applied science central to public health. It provides the methods to study the distribution and determinants of diseases in populations. The focus of epidemiology is on community health, namely, on the prevention of disease, disability and premature death in communities of people as well as animals. Risk evaluation is one of the central steps in the classical health risk assessment paradigm to identify needs for risk management. This chapter evaluates the two independent health risk assessment reports of Davies and Sears commissioned in 2013 by the Alberta Energy Regulator (AER) for the formal hearing, and presents the merits of each. Some of the strengths and weaknesses of each approach are exposed, together with their implications for both science and public policy. Each of the two reports was to shed light on the question of health effects as expressed through community complaints in relation to emissions from the bitumen recovery and transportation processes.