Int. J. Environ. Res. Public Health 2012, 9 1999 little judicial review of the Agency’s authority to consider the results of decisions based on cumulative risk assessment. EPA’s reluctance to assert its authority in this regard suggests that the Agency may be uncertain whether a court would view statutory language directing regulation of a single category of pollutant or medium as sufficient authority to support the practice of regulating that pollutant or medium while considering the impact of multiple pollutants in various media, or considering non-environmental factors. The lack of a definitive judicial statement on whether a cumulative risk approach is permissible leaves the question open for examination. As this article will show, many environmental statutes give EPA a broad mandate (e.g., protecting public health), where there is room for interpreting the statute as allowing use of cumulative risk assessment in decision-making, even if there are few instances where the Agency has followed this approach in the past. Box 1. Defining Cumulative Effects. DEFINING CUMULATIVE EFFECTS In this article, “cumulative effects” means the qualitative and quantitative impacts from exposure to multiple chemical and non-chemical stressors–including the effects on the ecological environment, on human health, or both. This broad term includes (but is not limited to) cumulative exposures, cumulative risks, and measurable cumulative impacts. In this article, we chose cumulative risk assessment methodology as the paradigm for our analysis because it provides a concrete example of a methodology with which to discuss hypothetical court review of an EPA decision. Further, there are compelling reasons why EPA might want to use cumulative risk assessment and the probable cumulative effects evinced through employing that methodology when making human health and ecological policy and rulemaking decisions. First, using cumulative risk assessment methodologies would present the Agency with a more accurate picture of the ecological and human health effects of its decisions than does an analysis of exposure to a single chemical or through a single medium [4,7]. Second, in 2009, the National Research Council (NRC) opined that unless EPA takes account of cumulative risks, risk assessment itself might become irrelevant in many decision contexts [13]. Third, cumulative risk assessment could be particularly helpful in addressing environmental justice (EJ) concern [14], because numerous studies have shown that minority, low-income, and indigenous communities are impacted by multiple environmental hazards, such as industrial facilities, landfills, transportation-related air pollution, poor housing, leaking underground tanks, pesticides, and incompatible land uses [15–33]. There is some research and analysis supporting EPA’s legal authority to consider EJ concerns under various Agency statutory authorities [34–36]. However, there is scarce legal research on EPA’s authority to consider cumulative effects in decision-making outside of the EJ context.