An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »


IRIS and the National Academies of Sciences (NAS)

On this page:

NAS Meeting to Evaluate the Protocol for the Inorganic Arsenic IRIS Assessment (July 2019)

A committee of the National Academies of Sciences (NAS) is hosting a public workshop on July 16, 2019, in Washington, D.C., to discuss the updated problem formulation and Systematic Review Protocol for the EPA's Integrated Risk Information System (IRIS) Assessment for Inorganic Arsenic. The committee will evaluate the revised scope of the assessment and determine whether the proposed methods are appropriate to synthesize the scientific evidence and develop conclusions.

The overall goal of this NAS review is to seek input on: (1) whether the refined scope for the assessment is justified; (2) whether the rationale provided in the protocol is sound; and (3) whether methods described to derive cancer risk estimates and non-cancer reference values are appropriate.

More information can be found on the Inorganic Arsenic Meetings & Webinars webpage.

Workshop to Discuss Evidence Integration with the NAS (June 2019)

A committee of the National Academies of Sciences (NAS) hosted a public workshop on June 3-4, 2019, in Washington, D.C.,to discuss evidence integration, which is a summary step of the systematic review in human health assessments conducted by the US Environmental Protection Agency (EPA).

Evidence integration, also referred to as weight-of-evidence evaluation, is a summary step of the systematic review in human health assessments conducted by EPA's Center for Public Health and Environmental Assessment (CPHEA), formerly known as the National Center for Environmental Assessment (NCEA). During this step, conclusions are drawn from each line of evidence that is relevant to the predefined PECO criteria.  Evidence integration generally involves subjecting the relevant evidence to a causal analysis,  which can be conducted using both qualitative and quantitative approaches. This is a structured process by which conclusions are drawn regarding the potential health effects in exposed humans, incorporating judgments about the strength of the human and animal evidence (both within and across lines of evidence) as well as information from mechanistic data necessary to answer key questions. 

During the workshop, the NAS heard from EPA and the public. Workshop topics included, lessons learned from recent international workshops on evidence integration in risk assessment, best practices in evidence integration, approaches for using mechanistic data to integrate evidence from animal and human studies, systematic review-enabled evidence integration case studies, and practical approaches to expedited evidence integration. The objective of the workshop was to explore relevant strategies for addressing challenges that arise for EPA during evidence integration in chemical assessments, with a primary focus on the use of mechanistic data. Poster sessions will accompany the workshop to address topics that are relevant to the workshop session topics.

Top of Page

NAS Workshop to Discuss Strategies and Tools for Conducting Systematic Reviews of Mechanistic Data to Support Chemical Assessments (December 2018)

A committee of the National Academies of Sciences (NAS) hosted a public workshop on December 10-11, 2018, in Washington, D.C., to discuss strategies and tools used by EPA's Integrated Risk Information System (IRIS) Program for conducting systematic reviews of mechanistic data in IRIS chemical assessments.

Mechanistic data are a rich source of information that is increasingly becoming a large component of the evidence used to inform human health risk assessments. Mechanistic studies, which include a variety of designs (i.e., in vitro, in vivo using various routes of exposure, ex vivo, and in silico), report measurements related to a health outcome that inform the biological or chemical events associated with phenotypic effects in both mammalian and non-mammalian model systems. This information can help to identify adverse outcomes associated with chemical exposures, including those that may not be typically evaluated in animal bioassays or human studies.

These studies can also guide the evaluation of the relevance of animal data to human health risk assessment. Despite the importance of considering mechanistic data, incorporation of these studies within a systematic review framework remains challenging. Challenges include: screening large numbers of diverse studies efficiently; developing transparent and reproducible criteria for identifying the most informative mechanistic studies; the lack of well-developed systematic review tools to assess internal validity of in vitro and in silico studies; and underdeveloped structured frameworks to guide integration of mechanistic information with human and animal health effects evidence.

The overall aim of this workshop was to explore the strategies and tools that are being developed across the systematic review community to search, screen, evaluate, and incorporate mechanic information into structured approaches for evidence synthesis and integration.

Top of Page

NAS Workshop to Discuss Advances Made to the IRIS Program (February 2018)

A committee of the National Academies of Sciences (NAS) hosted a public workshop on February 1-2, 2018, in Washington, D.C., to review systematic review and other method advances made by EPA in its Integrated Risk Information System (IRIS) Program.

In 2014, the NAS published a report evaluating the IRIS process. The NAS noted that the IRIS Program had made “substantial improvements” and provided recommendations in a report, Review of EPA’s Integrated Risk Information System [IRIS] Process.

Since 2014, the IRIS Program has continued to make advances in implementing systematic review, and has improved approaches for conducting dose-response analysis to further address recommendations provided by the NAS. EPA requested the NAS convene a panel to evaluate these recent advancements and develop a report for EPA.

During the workshop, the NAS heard from EPA and the public. Workshop topics focused on how IRIS has addressed the 2014 NAS recommendations, including approaches for evidence identification, evidence evaluation, and evidence integration, as well as advances in quantitative methods. The NAS panel has developed a report based on information presented by EPA at the workshop included below:

Top of Page

IRIS Workshop to Discuss the NAS Recommendations (October 2014)

EPA hosted a public workshop on October 15-16, 2014 to discuss recommendations from the National Academy of Science's (NAS) May 2014 report on ways to further improve the scientific quality of IRIS assessments. In their report, the NAS commended EPA for its substantive new approaches, continuing commitment to improving the process, and successes to date.

As a result, EPA announced an agreement with the NAS to arrange for independent experts to attend the IRIS bimonthly public meetings, in order to provide input on the science underlying the development of IRIS assessments through participation in IRIS Public Science Meetings.

These independent experts, speaking on their own behalf, attended the IRIS meetings to contribute to the scientific discussions of issues amongst EPA, stakeholders, and the public. The first meeting where NAS identified experts were invited to join the public discussion on key science questions and preliminary assessment materials was the February 2015 IRIS Public Science meeting. The February 2015 meeting agenda, listed under meeting materials, specifies the discussants that were identified by the NAS.

NAS Review of the IRIS Assessment Development Process (May 2014)

The National Academy of Sciences (NAS) released their review of the IRIS assessment development process. The NAS report applauded EPA’s efforts to improve IRIS and found that the Program had moved forward steadily in planning for and implementing changes in each element of the assessment process.

While recognizing EPA was still implementing changes, they noted that, “overall, the committee expects that EPA will complete its planned revisions in a timely way and that the revisions will transform the IRIS program.” Their report noted that the IRIS Program had made substantial progress in a short time, and the committee offered recommendations that build on EPA’s progress.

These recommendations provide continued direction for further improving the IRIS Program.

Top of Page

NAS Recommendations (April 2011)

The National Academy of Sciences (NAS) offered recommendations to the EPA for improving the development of IRIS assessments in their Review of the Environmental Protection Agency’s Draft IRIS Assessment of Formaldehyde, these recommendations went beyond this report and helped influence the entire IRIS process for developing assessments.

EPA Response

EPA submitted materials to the NAS to support their review of the IRIS assessment development process and implementation of improvements responsive to the 2011 NAS recommendations:

Top of Page