health effects

Evaluating Studies to Understand if a Chemical Causes Cancer

IRIS graphic identifier

By Kacee Deener

When friends ask me what I do, I always mention the Integrated Risk Information System (IRIS) Program and explain that through IRIS, EPA scientists help protect public health by evaluating scientific information on the health effects that may result from exposure to environmental contaminants.  The questions inevitably come up—how do you do that, and what kind of information do you look at?

Scientists around the world contribute to the knowledgebase about the health effects of chemicals.  A particular area of interest has been chemicals’ potential to cause cancer.

Because EPA’s work must be grounded in the best possible science, we recently updated how we consider some of the cancer research of the Ramazzini Institute (RI), a laboratory in Italy known throughout the world for their extensive work in this area, completing cancer studies for more than 200 compounds.

A few years ago, the National Toxicology Program (NTP) identified differences of opinion between their own scientists and those from the Ramazzini Institute in diagnosing certain types of cancers in a study on methanol.  The scientific community—including EPA—was concerned, since Ramazzini data was included in IRIS evaluations.  We reviewed all of our IRIS assessments to determine which, if any, relied substantially on RI data; we found four that did, and we put those assessments on hold.

To follow up, EPA and the National Institute of Environmental Health Sciences cosponsored a group of scientists with expertise in evaluating tissue samples and making disease diagnoses, a Pathology Working Group (PWG), to review several Ramazzini Institute studies. They found some instances where respiratory infections in Ramazzini study animals made definitive diagnoses difficult, and disagreed with some Ramazzini diagnoses, primarily certain leukemias and lymphomas that had been identified. Therefore, EPA decided not to rely on RI data on lymphomas and leukemias in IRIS assessments. There was agreement, though, in diagnosing solid tumors, and EPA decided to continue to consider Ramazzini Institute solid tumor data in IRIS assessments.

This has been an important issue in the world of chemical risk assessment. Last week, this was highlighted once again when a paper authored by EPA scientists, Scientific Considerations for Evaluating Cancer Bioassays Conducted by the Ramazzini Institute, was published in Environmental Health Perspectives.  The article interprets Ramazzini Institute study results and compares their testing protocols with those used by other federal agencies.  The results were consistent with the PWG findings—Ramazzini Institute results for cancer endpoints other than lymphoma and leukemias, and some cases of tumors of the inner ear and cranium, are generally consistent with those of the National Toxicology Program and other laboratories.  The paper also notes that, while differences in Ramazzini Institute testing protocols can complicate the interpretation of study results, they may also provide chemical risk assessors with insights that might not be observed in other laboratories.

The short answer to my friends’ questions is that EPA works to use the best available science—from across the U.S. and around the world—to support IRIS and our other assessments designed to protect public health.

About the Author:  Kacee Deener is the Communications Director in EPA’s National Center for Environmental Assessment, home of the IRIS Program.  She joined EPA 12 years ago and has a Masters degree in Public Health.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action.

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Writing Down IRIS

By Kacee Deener IRIS

As a scientist now working in science communications, I’m constantly surprised by the writing process.  You put something down on paper, revise it a few times, and then make tweaks here and there until you’re satisfied.  Then you look at it again later, and you make a few more changes.

Turns out lots of things in life are like that—including science programs.  In May 2009, EPA announced a new Integrated Risk Information System – or IRIS – assessment development process.

IRIS is an important program because it provides information on the health effects caused by exposure to chemicals in the environment.  People use IRIS, along with other science information, to inform decisions that protect public health across the U.S.

The new 2009 process was good for the IRIS Program.  But – as I’ve learned with writing – a few tweaks can make something even better.  Since 2009, we’ve learned a lot.  We’ve also received recommendations from the National Research Council (NRC) about improving IRIS assessments and about planning and scoping and stakeholder engagement in risk assessment.  So we’re making some common sense changes that will help us produce more high quality assessments in a timely and transparent manner.

In a nutshell, here’s what we are doing

  • Before beginning an assessment, we will meet with EPA’s regulatory programs – the folks who make decisions that help protect public health – to make sure we understand the big picture of why they need an assessment.
  • We will then hold a public meeting to discuss the plan for the assessment (so we better understand who needs it and why) and gather input about some technical aspects of developing the assessment (for example, are we concerned about people being exposed by breathing the chemical, ingesting it, or both?).
  • Next we will release a literature search for the chemical, evidence tables that summarize the critical scientific studies, and exposure-response figures that graphically depict the responses at different levels of exposure for each study in the evidence table. These materials highlight our thought process for determining which studies are most important for the assessment, help make sure we didn’t miss any important research, and help identify any potential scientific controversies early on.
  • We’re also using “stopping rules” so IRIS assessments are not delayed by ongoing research or scientific debate after certain points of the process have passed.
  • Finally, we’ve strengthened our practices for peer review and conflict of interest.

And this isn’t a complete list – you can read about all of the enhancements on our website.

These changes to IRIS are practical, common-sense improvements that emphasize scientific rigor and transparency.  They will also be good for our stakeholders, so like a well written story, it’s a win-win for everyone involved.

Like a committed science writer, we’ll always be revising whenever improvements are needed, but take a minute to check out the latest edition.  I think you’ll like the improvements.

About the Author: Kacee Deener is the Communications Director in EPA’s National Center for Environmental Assessment, home of the IRIS Program.  She joined EPA 12 years ago and has a Masters degree in Public Health.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action.

Please share this post. However, please don't change the title or the content. If you do make changes, don't attribute the edited title or content to EPA or the author.