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Cumulative Impact Assessment vs Cumulative Risk Assessment: Knowing the Difference Makes a Difference 

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The environmental news headlines regularly refer to the U.S. Environmental Protection Agency’s (“EPA’s” or “Agency’s”) efforts to 1) release a final “cumulative risk guidance” and 2) to develop more robust approaches to assessing “cumulative impacts” in decision-making. Understanding the differences in timing, scope, and purpose of EPA’s work in these two arenas can be very important to companies seeking to anticipate and proactively address community and regulator concerns.  Understanding and monitoring states with an existing cumulative impact statutory framework will inform how EPA’s efforts to address cumulative impacts in the federal arena unfold as it advances environmental justice priorities identified by the Biden-Harris Administration. 

An Emerging Definition of Cumulative Impact Assessment

In its just released Cumulative Impacts White Paper, EPA lays out topics for consideration by  its’ Science Advisory Board which will meet in early March to discuss the Agency’s draft definitions of “cumulative impacts” and “cumulative impact assessment.” EPA posits that cumulative impacts “refers to the total burden – positive, neutral, or negative – from chemical and non-chemical stressors and their interactions that affect the health, well-being, and quality of life of an individual, community, or population at a given point in time or over a period of time” and that cumulative impact assessment is “the process of accounting for cumulative impacts in the context of problem identification and decision-making. It requires consideration and characterization of total exposures to both chemical and non-chemical stressors, as well as the interactions of those stressors, over time across the affected population.”  EPA goes on to note that “[n]ot all stressors fall under the purview of EPA’s regulatory mandates. While many chemical stressors do, many non-chemical stressors, such as access to medical care, family stress, or community violence, are not factors that can be regulated by EPA. However, because EPA actions and decisions to protect human health and the environment interact with or are affected by the cumulative impacts of both chemical and non-chemical stressors, both must be assessed to understand the full impact of a decision or action.” There still remains an important need to flesh out how regulatory decision makers would impose substantive limits and conditions on facilities to address cumulative impacts.

EPA carefully notes that both terms are “distinct from ‘cumulative risk assessment,’ which EPA is addressing through [separate guidance].” The White Paper dives deeply into the importance of understanding cumulative impacts assessment to best focus Agency efforts on communities disproportionately affected by environmental burdens. 

Notably, this White Paper is also distinct from a “cumulative impacts guidance”1  being developed by EPA’s External Civil Rights Compliance Office (“ECRCO”). The ECRCO guidance will be given to all recipients of EPA funding (i.e. state environmental agencies) to help them analyze, and avoid, whether their actions have a disparate impact effect on a community in violation of the non-discrimination provisions of Title VI of the Civil Rights Act. Still to be seen is how state regulators deploy the ECRCO guidance as they implement delegated federal environmental programs. 

The White Paper also acknowledged the Council on Environmental Quality’s ("CEQ") longstanding definition of cumulative impacts under the National Environmental Policy Act ("NEPA"), while differentiating the draft definition. The field of cumulative impacts assessment is more mature in NEPA than in other areas of the law, requiring project proponents seeking federal permits to consider cumulative impacts in its environmental impact statements ("EIS") from 1978 to 2020. The Biden Administration recently proposed restoring this cumulative impact requirement to “ensure that the NEPA process fully and fairly considers the appropriate universe of effects, [including] effects on communities with environmental justice concerns.”

The Advancing Field of Cumulative Risk Assessment

Risk assessment has been conducted by EPA since the 1970s, and many scientific, congressional, and academic bodies have weighed in to guide EPA’s use of ecological risk assessment, human health risk assessment, and other risk assessment disciplines. A growing field of risk assessment practice is that of cumulative risk assessment, and EPA has also committed to releasing in final form in 2022 updated cumulative risk assessment guidelines. The Agency’s last published work in this arena is a 2003 Framework for Cumulative Risk Assessment.  In that document, EPA defines “cumulative risk” as “the combined risks from aggregate exposures to multiple agents or stressors,” and cumulative risk assessment as “an analysis, characterization, and possible quantification of the combined risks to health or the environment from multiple agents or stressors.” Described as a “first step,” the Framework identifies basic elements of cumulative risk assessment and provides a structure for conducting them. Efforts to update the Framework in the Obama Administration in 2013 never advanced, and external discussions on an updated version of the Framework seemed stalled. However, in September 2021 EPA announced that updated guidelines had been through a “letter peer-review” and would be released in final form. 

Given the length of time EPA’s cumulative risk assessment guidelines have been under wraps, there has been significant chatter about the importance of putting the document out in draft and accepting public comment on it. Manufacturing associations have also noted that public comment and peer-review is appropriate under the Agency’s own Peer Review Handbook, which states that “the more novel or complex the science or technology, the greater the cost implications of the impending decision or public policy, and the more controversial the issue, the stronger the indication is for a more extensive and involved peer review and for an external peer review in particular” and that “generally, these will be products with large impacts. Soon enough, the regulated community will know if these arguments prevailed, or if EPA will release a final document as planned. 

States Making their Mark

State regulators are not waiting for EPA, however, as several have passed or proposed legislation that incorporate cumulative impacts analysis in permitting decisions for facilities located in overburdened communities with EJ concerns. For example, New Jersey, Massachusetts, and New York all recently passed laws requiring a cumulative impact assessment as a prerequisite to obtaining certain permits2 in disadvantaged communities. While other states have suggested that requiring cumulative impacts assessment is beyond the scope of state authority to include in permitting,  pressure is mounting on states to take more holistic approaches to permitting3 – and to look at each renewal or new permit in the context of the total community pollution burden. 

A Look Ahead

With the Biden-Harris Administration’s focus on EJ communities, clearly consideration of cumulative impacts, and advancing the scientific discipline of cumulative risk assessment are both important. Permitted entities should be watching the evolution of these areas, the maturation of definitions, and how the Agency plans to use these tools in the field. With understanding, regulated facilities can not only participate in the process, but offer their own insights into how they – and their neighboring facilities’ – impacts should be considered.


1 https://www.epa.gov/system/files/documents/2021-10/_epaoig_20-e-0333_agency_response2.pdf
See, S.232 Leg., 219th Sess. (N.J. 2020) An Act Concerning The Disproportionate Environmental And Public Health Impacts Of Pollution On Overburdened Communities; S.9, Leg., 192nd Sess. (Ma. 2021) An Act Creating a Next Generation Roadmap for Massachusetts Climate Policy.
Michigan Department of Environment, Great Lakes and Energy (EGLE), EGLE Approves Asphalt Plant Air Permit; Seeks Federal Guidance, support to address EJ concerns, Nov. 15, 2021. Available at https://www.michigan.gov/egle/0,9429,7-135-3308-572438--,00.html 

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