Int. J. Environ. Res. Public Health 2012, 9 2000 One analysis that touches on the topic is a recently issued EPA document, Plan EJ 2014: Legal Tools (hereinafter referred to as EJ Legal Tools), which provides an overview of several discretionary legal authorities that are or may be available to EPA to address environmental justice considerations under Federal statutes and programs [36]. However, this document does not address assessing cumulative effects to develop a realistic picture of how they affect human health or the environment outside of the environmental justice context. Analyzing cumulative effects from multiple stressors allows a more realistic evaluation of a population’s risk to pollutant exposure [15]. In a conventional risk assessment, failure to account for cumulative exposures from pollutants likely results in underestimating the combined exposure effects, to the extent that such exposures are experienced ([11], p. 362; [37], p. 117). Without an assessment of cumulative risks and probable cumulative effects, a regulatory authority charged with protecting human health and the environment may be unable to fulfill its mandate. 1.2. How EPA Uses Risk Assessment 1.2.1. What is Risk Assessment? At its most general, quantified risk assessment entails the evaluation of scientific information on the hazardous properties of environmental agents, the extent of human exposure to those agents, and the risks of adverse effects (human health, or ecological effects) associated with the exposure. The product of the evaluation is a statement regarding the probability, expressed quantitatively or qualitatively, that populations so exposed will be harmed, and to what degree ([38], p. 26; [11], p. 254). Essentially, risk assessment is the process that leads to a characterization of risk ([13], p. 15). “EPA considers risk to be the chance of harmful effects to human health or to ecological systems resulting from exposure to an environmental stressor” [39]. An EPA risk assessment typically follows four basic steps: (1) Hazard Identification: First, the Agency examines whether a stressor has the potential to cause harm to humans and/or ecological systems, and if so, under what circumstances. (2) Dose-Response Assessment: EPA then examines the numerical relationship between exposures and effects. (3) Exposure Assessment: The Agency then examines what is known about the frequency, timing, and levels of contact with a stressor. (4) Risk Characterization: Finally, EPA summarizes and integrates information from the proceeding steps of the risk assessment to synthesize an overall conclusion about the nature and presence or absence of risk [40–42]. Cumulative risk assessment is a type of risk assessment that the NRC defines as “analysis, characterization, and possible quantification of the combined risks to health or the environment posed by multiple agents or stressors” ([13], p. 213 citing [3]). According to NRC, these stressors may be chemical, biologic, radiologic, physical, or psychologic ([13], p. 213 citing [7]). Further, these stressors may be included as quantitative or qualitative elements of an analysis, based on the complexity and context of the decision at issue ([13], p. 215). Thus, a risk assessment may be cumulative even if it lacks a quantitative analysis of all relevant non-chemical stressors ([13], pp. 217–219). For example,