Navigating a Newly Posted IRIS Assessment

By Ashley Mayrianne Jones and Lou D’Amico, Ph.D.

Last week, EPA’s Integrated Risk Information System (IRIS) Program released the final assessment of trimethylbenzenes (TMBs). IRIS assessments provide health effects information and toxicity values for cancer and non-cancer health outcomes by using the best available scientific data.  Government and others combine IRIS toxicity values with exposure information to help characterize public health risks of chemical substances and use these assessments to support decisions designed to protect human health.

But you don’t need to wait until an assessment is finalized to learn more about the science that informs the Agency’s risk assessment and risk management decisions.

EPA is committed to transparency and providing information about its research and assessments. IRIS is no exception. Recently, EPA updated their web presence to help the general public find information faster and easier. As part of this update, EPA made significant changes to the IRIS website.

screenshot of the iris website

The online IRIS database contains crucial information from assessments on chemical substances that can be used to support hazard identification and dose-response assessment – two of the four steps in the human health risk assessment process.

So where to begin?  Well, the first place would be the IRIS Program home page at https://www.epa.gov/iris. There, you’ll find links to general program materials (such as the IRIS multi-year agenda), a calendar of public meetings and workshops, and an  “About IRIS” page, which explains the IRIS process and program history. You can also sign up for the IRIS listserv using the form at the top of the home page. Even more ways to stay up-to-date on IRIS activities are described under “Staying Connected.”

The quickest option to search for a chemical is to enter the chemical name or CASRN (the CAS registry number – a unique identifier for chemical substances) in the “Search IRIS” box on the middle right of the home page. The “Assessments” link under the search bar on the home page allows for more advanced search options.  Using the link, you can browse chemicals alphabetically, by organ or system, and by current stage in the IRIS process. The quick check provides a convenient way of seeing what step of the IRIS process an ongoing chemical assessment is in.  Each chemical in the IRIS database has a chemical-specific webpage, with links to the toxicological reviews (if available), an IRIS summary of the findings, and key information on toxicity values and the organ systems that may be affected by exposure to a chemical.  Toxicological reviews can be lengthy documents though, and the IRIS summary provides a shorter description of the findings for a given chemical.

Anyone can browse the IRIS database or search for a specific chemical assessment, just like the newly added assessment for trimethylbenzenes (TMBs). TMB’s are a group of volatile hydrocarbons produced during petroleum refining and may be inhaled by exposure to vehicle emissions.  The IRIS assessment for TMBs actually contains information on three isomers: 1,2,3-TMB, 1,2,4-TMB, and 1,3,5-TMB, which all have specific chemical pages on the IRIS website.

scrren shot of the specific page within the IRIS website

Whether you’re interested in TMBs or any other chemical, a wealth of information is available on each chemical’s webpage.  The critical systems affected by a chemical are identified, along with toxicity values (like the reference dose and reference concentration for non-cancer effects) and are provided right on the main page.  For example, TMBs are associated with nervous, respiratory, and hematological system effects.  The carcinogenicity of a chemical is also described through a weight-of-evidence characterization, as well as quantitatively, if appropriate.  Each IRIS assessment provides authoritative, peer-reviewed information on a chemical’s toxicity.

A tremendous amount of work goes into completing the 7-step process to finalize a draft IRIS assessment. EPA releases a number of documents along the way, including past drafts of assessments, comments from interagency reviewers, and preliminary materials used early in assessment development.  Your gateway to all this information is through the “History” tab right on the main page for each chemical entry on the database.

IRIS assessments aren’t regulations, but they provide a critical part of the scientific information for decision-making to protect public health across EPA.  They’re also important resources for state environmental and public health agencies, and are widely used by the scientific community in the U.S and the world.

If you have any questions regarding the IRIS Program or the website, you can always contact us at the IRIS hotline at 202-566-1676 or hotline.iris@epa.gov.

About the Authors: Ashley Mayrianne Jones is a student contractor and writer working with the science communication team in EPA’s Office of Research and Development.  Lou D’Amico is the Acting Communications Director for the National Center for Environmental Assessment, which houses the IRIS Program.

Editor's Note: The views expressed here are intended to explain EPA policy. They do not change anyone's rights or obligations. You may share this post. However, please do not change the title or the content, or remove EPA’s identity as the author. If you do make substantive changes, please do not attribute the edited title or content to EPA or the author.

EPA's official web site is www.epa.gov. Some links on this page may redirect users from the EPA website to specific content on a non-EPA, third-party site. In doing so, EPA is directing you only to the specific content referenced at the time of publication, not to any other content that may appear on the same webpage or elsewhere on the third-party site, or be added at a later date.

EPA is providing this link for informational purposes only. EPA cannot attest to the accuracy of non-EPA information provided by any third-party sites or any other linked site. EPA does not endorse any non-government websites, companies, internet applications or any policies or information expressed therein.

Improving IRIS: Please Join the Conversation

By Kacee Deener

IRIS graphic identifier

Over the past few years, EPA has embraced a major new effort to enhance its Integrated Risk Information System (IRIS) Program to improve the scientific foundation of assessments, increase transparency, and improve productivity. IRIS is a human health assessment program that evaluates information on health effects that may result from exposure to environmental contaminants. Information from IRIS is used by EPA and others to support decisions to protect human health.

We think we’ve made terrific progress so far, and we were thrilled that the National Academies’ National Research Council (NRC) agrees. They spent the past two years reviewing IRIS, and in May 2014, they issued a report highlighting our progress and offering recommendations on keeping the progress moving forward (Assistant Administrator Lek Kadeli recently wrote about this on EPA Connect, the Agency’s leadership blog).

In their report, the NRC commended EPA for its substantive new approaches, continuing commitment to improving the process, and successes to date. They noted that the IRIS Program has moved forward steadily in planning for and implementing changes in each element of the assessment process. They also provided several recommendations which they said should be seen as building on the progress we’ve already made.

We are happy to announce that we are taking additional steps to improve the IRIS Program. In October, we will hold a public workshop to discuss specific recommendations from the NRC’s report, which fall under the three broad topics below. We invite you to provide early input by commenting on this blog post, which is the first in a new IRIS blog series geared toward generating online scientific discussion about issues relevant to the IRIS Program. We plan to use blog posts like this more in the future to get your input.

  • Topic 1 – Refining systematic review methodology, including methods to evaluate risk of bias. The NRC stated that EPA should continue to document and standardize its process for evaluating evidence and recommended EPA develop tools for assessing risk of bias in human, animal, and mechanistic studies that are used as primary data sources. The NRC noted the limitations of available approaches for use with observational (nonrandomized) studies, and advocated exploration of differences in applying methods for evaluating epidemiological studies to controlled experimental in vivo and in vitro studies. They noted that these approaches will depend on the complexity and extent of data on a chemical and the resources available to EPA, and that additional methodological work might be needed to develop empirically-supported evaluation criteria for animal or mechanistic studies.
  • Topic 2 – Advancing methodology to systematically evaluate and integrate evidence streams. The NRC stated that EPA should continue to improve its evidence-integration process incrementally, and to enhance its transparency. The committee provided several alternatives for organizing evidence of hazard potential and recommended that the IRIS Program should either continue with the guided-expert-judgment process for evaluating evidence, but make its application more transparent, or adopt a structured approach with rating recommendations. The committee also encouraged the IRIS Program to simultaneously expand its ability to perform quantitative modeling, specifically using Bayesian methods, to inform hazard identification.
  • Topic 3 – Combining quantitative results from multiple studies, presenting appropriate quantitative toxicity information, and advancing analyses and communication of uncertainty. The committee encouraged the IRIS Program to continue its shift towards the use of multiple studies for dose-response assessment, but with increased attention to judging the relative merits of mechanistic, animal and epidemiologic studies, with an ultimate goal of developing formal methods for combining studies and deriving toxicity values in a transparent and replicable manner. The NRC stated that it is critical to consider systematic approaches to synthesizing and integrating the derivation of a range of toxicity values in light of variability and uncertainty. Integral to this latter goal is the NRC recommendation to develop methods to systematically conduct uncertainty analyses and to appropriately communicate uncertainty to the users of IRIS assessments.

We’re interested in hearing your thoughts about the NRC recommendations above. For example, do you have ideas about how we should move forward to address the recommendations in these topic areas? Do you have scientific suggestions for the IRIS Program to consider related to these topics? Do you have suggestions for who we should ask to speak at the workshop? Please add your thoughts, ideas, and suggestions in the comments below and join the conversation!

About the Author: Kacee Deener is the Communications Director in EPA’s National Center for Environmental Assessment.  She joined EPA 13 years ago and has a Masters degree in Public Health.

Editor's Note: The views expressed here are intended to explain EPA policy. They do not change anyone's rights or obligations. You may share this post. However, please do not change the title or the content, or remove EPA’s identity as the author. If you do make substantive changes, please do not attribute the edited title or content to EPA or the author.

EPA's official web site is www.epa.gov. Some links on this page may redirect users from the EPA website to specific content on a non-EPA, third-party site. In doing so, EPA is directing you only to the specific content referenced at the time of publication, not to any other content that may appear on the same webpage or elsewhere on the third-party site, or be added at a later date.

EPA is providing this link for informational purposes only. EPA cannot attest to the accuracy of non-EPA information provided by any third-party sites or any other linked site. EPA does not endorse any non-government websites, companies, internet applications or any policies or information expressed therein.