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U.S. EPA releases Draft Cumulative Risk Assessment Guidelines for Planning and Problem Formulation

Posted: August 22nd, 2023

Authors: Joe S. 

On June 16, 2023, the United States Environmental Protection Agency (U.S. EPA) released a draft document “Cumulative Risk Assessment (CRA) Guidelines for Planning and Problem Formation” that describes the steps for the planning of CRAs and offers guidance for when cumulative risk assessments could be useful. The CRA guidance is responsive to the charge given by Executive Order 13985 on Advancing Racial Equity and Support of Underserved Communities Through the Federal Government, which directed all agencies of the federal government to “pursue a comprehensive approach to advancing equity for all, including people of color and others who have been historically underserved, marginalized and adversely affected by persistent poverty and inequality.”

How Does a Cumulative Risk Assessment Differ from a Traditional Risk Assessment?

A traditional risk assessment has five steps:

  • Planning
  • Hazard Identification
  • Dose-Response Analysis
  • Exposure Assessment
  • Risk Characterization

A traditional risk assessment usually focuses on the cleanup of a single contaminated site, or the evaluation of the impact of an individual chemical. For many years traditional risk assessment has been criticized because its narrow focus does not allow it to accurately capture the risks associated with exposure in situations where there may be simultaneous exposure to multiple stressors1 that could influence vulnerability.

The new draft CRA guidelines are focused on the “Planning” and “Hazard Identification” steps of a traditional risk assessment and describe how these stages of a traditional risk assessment change when conducting a CRA. The new guidance outlines eight milestones in the CRA planning process. These include:

Cumulative Risk Assessment Planning Milestones

1. Initiating factors

2. Identification of stakeholders

3. Statement of purpose

4. Evaluation of the fit for purpose

5. Scoping summary statement

6. Conceptual Model

7. Weight of evidence evaluation

8. Analysis plan

The first milestone, initiating factors, is aimed at identifying the environmental issue that the CRA is intended to address. For example, this could include informing a regulatory action, addressing a community health concern, or to comply with broader U.S. EPA priorities such as children’s health, environmental justice, or sustainability. The initiating factors are used to help focus the CRA in terms of the geographic area, population, stressors, health effects and the time frame in which the CRA is to be completed.

The second milestone focuses on how to involve stakeholders (i.e., interested members of the public, affected industries, public health or environmental organizations or other government agencies) early and often in the decision-making process. The timing, frequency, and level of community involvement will depend on several factors including regulatory requirements, what environmental issue is being studied, and community interest. Common questions asked during this milestone include:

  • What are the opportunities for stakeholder involvement?
  • Who are the stakeholders?
  • What communication materials are needed to effectively engage stakeholders?
  • What mechanisms will be most effective for engaging different stakeholders?

A statement of purpose (Milestone 3) is used to clearly identify what the CRA is intended to accomplish or produce. At a minimum, the CRA needs to state the initiating factors and the risk management decision the CRA is intended to inform.

The fit for purpose (Milestone 4) stage of a CRA lays out the scope. It identifies the key aspects of the CRA and includes information around the environmental issue being studied such as the stressors being evaluated, dose response factors, demographics, genetic variability, age of the population being evaluated, the health status, health behaviors (e.g., smoking, diet), social determinants (e.g., socioeconomic status, environmental justice factors), other analyses (uncertainty and variability, economic, etc.…), and lastly identifies limitations (e.g., funding, schedule, legal, availability). The fit for purpose milestone generates a scoping summary statement (Milestone 5) which lays out the general objectives, constraints, and boundaries of the CRA.

At this stage of a CRA, the analysis may be broken into “Tiers” where initial conservative estimates of exposure and health effects are made to provide a crude estimate of risk. If the initial tier results in no or low risk, it may inform as to whether more detailed assessment of risk is necessary.

Milestone 6 focuses on developing a conceptual site model (CSM), which is a written or pictorial depiction of the pathways connecting hazards to health outcomes in a population of interest. CSMs are used to inform the work product, and usually incorporate the following considerations:

  • The rationale for the stressors, exposure pathways, exposed population, health endpoints and risk metrics being considered.
  • The basis for the model.
  • The data sources available and resource implications of collecting additional data.

A CSM is intended to be developed iteratively and include input from other stakeholders and experts. CSMs should be updated when new data is available that may alter the original model. An example CSM from the U.S. EPA draft guidance document is provided below.

The weight of evidence (WoE), Milestone 7, is the process used by the CRA Team to identify possible exposure-health response relationships and exposure-response modifiers to be considered in the CSM. The results can be expressed qualitatively or quantitatively, depending on the information available and the needs of the CRA. The WoE will support or be used to provide the evidence base necessary to develop plans for the analysis phase. Evidence evaluation and data quality assessment requirements should be considered throughout the CRA to ensure the final assessment meets the general objectives of the CRA.

The final milestone, Milestone 8, lays out the analysis plan. The analysis plan clearly identifies what analyses will be done and what methods and inputs will be used. The analysis plan should describe any data collection needs, as well as any preliminary risk estimates. The analysis plan should also describe what exposure data is needed and the metrics that will be used to assess health outcomes. The analysis plan should determine what techniques are available to assess cumulative exposure and how it will assess baseline conditions. Lastly, the analysis plan should discuss how it will evaluate the quality of the data obtained as well as outline the cost and schedule for the CRA.

What Does it Mean to You?

The draft CRA guidelines lay the foundation for considering current and anticipated cumulative risk analytical methods. Notably the CRA guidelines do not provide guidance on what health endpoints should be evaluated or which analytical methods to use when conducting a CRA. The draft CRA guidelines do not discuss what is considered a “safe” level of exposure to multiple stressors. U.S. EPA is developing separately a framework for cumulative impact assessment which it identifies as a complementary assessment strategy to CRA that may address these issues. U.S. EPA is accepting comments on the draft CRA guidance until August 30, 2023.

If you have concerns about the potential implications of the draft CRA guidelines or need help parsing through it, feel free to contact your ALL4 Project Manager or Joe Sabato. We’ll continue to monitor cumulative risk and cumulative impact assessment guidance from the U.S. EPA and states as additional tools and guidance documents become available. We can also help you evaluate permitting risks, from EJ concerns to regulatory issues, and assist in developing a strategy to make the permitting of your project as efficient as possible.

1 Stressor is used by U.S. EPA to describe any physical, chemical, biological, or psychosocial agent that could induce an adverse response. In other words, it’s what someone is exposed to that elicits an adverse health effect.


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