Cumulative Impacts Explained

Cumulative Impacts are defined as the totality of exposures to combinations of chemical and nonchemical stressors and their effects on health, well-being, and quality of life outcomes.

• Cumulative impacts include contemporary exposures to multiple stressors as well as exposures throughout a person’s lifetime. They are influenced by the distribution of stressors and encompass both direct and indirect effects to people through impacts on resources and the environment. Cumulative impacts can be considered in the context of individuals, geographically defined communities, or definable population groups. Cumulative impacts characterize the potential state of vulnerability or resilience of a community. (U.S. EPA. Cumulative Impacts Research: Recommendations for EPA’s Office of Research and Development. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-22/014a, 2022)

Cumulative Impact Assessment is defined as a process of evaluating both quantitative and qualitative data representing cumulative impacts to inform a decision.

• Cumulative impact assessment requires a systematic approach to characterize the combined effects from exposures to both chemical and non-chemical stressors over time across the affected population group or community. It evaluates how stressors from the built, natural, and social environments affect groups of people in both positive and negative ways. The posited elements of a cumulative impact assessment include community role throughout the assessment, such as identifying problems and potential intervention decision points to improve community health and well-being; combined impacts across multiple chemical and non-chemical stressors; multiple sources of stressors from the built, natural, and social environments; multiple exposure pathways across media; community vulnerability, sensitivity, adaptability, and resilience; exposures to stressors in the relevant past and future, especially during vulnerable lifestages; distribution of environmental burdens and benefits; individual variability and behaviors; health and well-being benefits/mitigating factors; uncertainty and variability associated with the data and information; and an approach for how to integrate data and information to assess cumulative impacts. (U.S. EPA. Cumulative Impacts Research: Recommendations for EPA’s Office of Research and Development. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-22/014a, 2022)