Exposing the Missing Link: Advancing Exposure Science to Rapidly Evaluate Chemicals

By Tina Bahadori, Sc.D.

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Acknowledging that exposure is vital to understanding and preventing human and environmental risks, the National Academies of Science in its 2012 report, “Exposure Science in the 21st Century: A Vision and A Strategy,” called for characterizing exposures quickly and cost-effectively at multiple levels of integration—including time, space, and biologic scales—and for multiple and cumulative stressors. The report further emphasized the importance of scaling up methods and techniques to detect exposure in large human and ecologic populations of concern.

To realize this vision, our EPA researchers are leading the forefront of exposure science, developing and testing new paradigms to efficiently generate and collect exposure information. In one area, for example, we are rapidly estimating levels of exposure and developing models to evaluate chemical exposures across consumer products and chemical life cycle.

Just last year, our scientists published several scientific peer-reviewed journal articles about these pivotal efforts and publicly released their exposure estimation tools for anyone to use and to evaluate their utility. Put together as a suite of exposure science tools, the following three examples showcase how advances in our research have transformed exposure science in a very short time.

  • ExpoCast is a tool that implements a collection of models and data to provide high-throughput exposure estimations for thousands of chemicals. Evaluating both farfield and nearfield exposure routes, our tool has been used to develop exposure estimates for approximately 1,900 chemicals; these estimates can be used to prioritize chemicals with the greatest likelihood for exposure.
  • Stochastic Human Exposure and Dose Simulation High-throughput model (SHEDS-HT) produces estimates for thousands of chemicals in a more rapid and cost-effective manner. SHEDS-HT accounts for multiple routes, scenarios, and pathways of exposure to understand the total exposure to these chemicals while retaining population and life stage information.
  • Chemical Product Categories Database (CPCat) catalogs the use of over 40,000 chemicals used in different consumer products. The database compiles chemical use information from multiple sources while product information is gathered from retail stores’ public Material Safety Data Sheets (MSDS).

To further advance the vision for exposure science in the 21st century, EPA invited the academic research community through the Science to Achieve Results (STAR) program to develop and apply new methods and technologies to efficiently collect data that will support a more comprehensive understanding of the science. Recently, we awarded grants—totaling $4.5 million—to five universities to conduct innovative research to advance methods for characterizing real-world human exposures to chemicals associated with consumer products in indoor environments. I am greatly looking forward to the work produced by these ambitious research teams because the data collected and research results will provide much needed and otherwise absent exposure information, and will help advance the relevance and applicability of current models.

Since innovation and transformation occur most rapidly in collaborative environments, on February 3-4, 2015, we will be hosting an EPA Exposure Science in the 21st Century Grants Kickoff meeting to publicly announce the grant recipients and to germinate and facilitate collaborations among EPA exposure scientists and the grant recipients.

The grant recipients include these transdisciplinary teams:

  • University of California, San Francisco—Principle Investigator: Tracey Woodruff Ph.D.
  • Duke University—Principle Investigator: Heather M. Stapleton Ph.D.
  • University of California, Davis—Principle Investigator: Deborah H. Bennett Ph.D.
  • Virginia Tech—Principle investigator: John Little Ph.D.
  • University of Michigan—Principle Investigator: Xudong Fan Ph.D.

To quantify, manage, and prevent risk, we need both exposure and toxicity information. To this end, EPA’s Toxicity Forecaster (ToxCast) which screens thousands of chemicals for potential health effects has proven to be an invaluable resource. Combined with our advances in high-throughput exposure estimations, we are beginning to have a better understanding of the landscape of chemical exposures and how to prioritize them for potential environmental and human health risks.

Our research is still evolving—we hope to maintain this accelerated pace and continue to advance the leading edge of the science. But to ground our research in pragmatic and health protective solutions, we recently requested a new study by the National Academy of Science to provide guidance on how best to integrate these advances into risk-based evaluations.

I believe the time is ripe scientifically—with advances in biotechnology, computational biology and chemistry, informatics, and allied fields—to change the face of chemical risk assessments for existing chemicals, for selection of safer alternatives, and for innovating and designing modern materials and products. I am confident that our research in exposure science will provide the missing link that has long hindered these advances.

About the Author: Tina Bahadori, Sc.D. is the National Program Director for EPA’s Chemical Safety for Sustainability research program. Learn more about her on EPA’s Science Matters: Meet our Scientists web page.

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