computational toxicology

Advancing Chemical Testing by the Thousands

Reposted from EPA Connect, the official blog of EPA leadership.

By Bob Kavlock

Bob Kavlock PortraitStudying thousands of chemicals at a time with the use of high-tech computer screening models and automated, often robot-assisted processes sounds like science fiction. But it’s not. EPA scientists are doing just that, leading the advancement of “high-throughput screening,” fast, efficient processes used to expose hundreds of living cells or isolated proteins to chemicals and then screen them for changes in biological activity—clues to potential adverse health effects related to chemical exposure.

This scientific advance is positioned to transform how we understand the safety of chemicals going forward. Twenty years ago, using high-throughput screening to test chemicals for potential human health risks seemed like technology that belonged in a science fiction television series rather than in real life.

Back then there were several large data gaps that would not allow us to extrapolate from the isolated biological changes we observe on a cellular level to adverse human health effects. However, through our computational toxicology (CompTox) research, which integrates, biology,

Robotic arm moving samples for screening

Robotic arm moves samples for automated chemical screening.

biotechnology, chemistry, and computer science, that is changing. We are helping to transform the paradigm of chemical testing from one that relies almost solely on expensive and time-consuming animal testing methods to one that uses the full power of modern molecular biology and robotics.

A significant part of this effort is the Toxicity Forecaster (ToxCast), launched in 2007. ToxCast allows us to prioritize potentially toxic chemicals for more extensive testing as well as giving us the opportunity to test newer, possibly safer alternatives to existing chemicals. By 2013, we evaluated more than 2,000 chemicals from industrial and consumer products to food additives using more than 500 high-throughput screening assays.

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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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EPA Scientists Presented Open Science at White House

By Tina Bahadori

From weather forecasts, air quality advisories, and portable GPS navigation devices, to waterfowl migration, and the mapping of the human genome, the use of government and government-supported science and data have vastly improved our lives. They have also sparked countless new private businesses and industries leading to economic growth and opportunity for innovators and entrepreneurs in every region of the country.

Recognizing the power and potential of such Open Science, on June 20, 2013 the White House invited four EPA scientists—Drs. Richard Judson, Keith Houck, Matt Martin, and Ann Richard—to present research posters describing their efforts to provide public access to massive amounts of data from chemical safety studies. The scientists presented their posters after the White House’s “Champions of Change” award ceremony. The award ceremony recognized 13 Champions of Change for their efforts to provide the public access to innovative science.

In addition to the 13 Champions of Change, the White House selected 12 scientists (including the EPA researchers) to present posters describing their vision and commitment to Open Science.

EPA scientists at the White House poster session.

EPA scientists Ann Richard and Matt Martin at the White House poster session.

The select group of 25 was chosen from hundreds of nominations submitted to the White House’s request for innovative Open Science leaders. The White House event highlighted outstanding individuals, organizations, and research projects promoting and using open scientific data and publications to accelerate progress.

To exemplify Open Science work, the four EPA scientists presented how they are using advances in computational toxicology to provide open and accessible chemical safety data to help better protect human health and the environment. Each of the EPA scientists are working to harness the power of computer science and innovative new chemical safety assessment methods and tools to provide open, transparent public access to chemical information. For example:

  • Dr. Matt Martin leads a team of Agency scientists and partners who developed the Toxicity Reference database (ToxRefDB). ToxRefDB contains 30 years and $2 billion worth of pesticide registration studies. The database allows scientists and others to search and download thousands of toxicity testing results on hundreds of chemicals that were previously only available on paper or microfiche.
  • Dr. Ann Richard is the leader behind another open, accessible database, the Distributed Structure-Searchable Toxicity Database (DSSTox). DSSTox provides open-access to information on the physical and structural properties of chemicals and links this information to toxicity potential. This is key information for assessing the potential risk of chemicals to human health and the environment.
  • Dr. Richard Judson leads a team of scientists who developed the Aggregated Computational Toxicology online Resource (ACToR). ACToR is EPA’s online warehouse of all publicly available chemical data aggregated from more than 1,000 public sources on more than half a million chemicals. ACToR can be used to query a specific chemical and find available public hazard, exposure, and risk assessment data as well as previously unpublished studies related to cancer, reproductive, and developmental toxicity.
  • Dr. Keith Houck is the driving force behind EPA’s Toxicity Forecaster (ToxCast), a research program advancing the use of automated, rapid chemical tests (called “high-throughput screening assays”) to screen thousands of chemicals in more than 650 assays for toxicity potential. This includes the development of the ToxCast Database (ToxCastDB) which provides publicly accessible, searchable, and downloadable access to all the screening data generated by ToxCast.

These four scientists have led the effort to democratize access to knowledge and information and level the playing field for all those involved and interested in protecting public health and the environment. By doing so, they exemplify the spirit of Open Science celebrated by President Obama’s Champions of Change program.

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.

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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Science Matters: Predicting the Future of Children’s Health

Children's Health MonthTo observe October as Children’s Health Month, we will periodically post Science Matters feature articles about EPA’s children’s health research here on the blog.  Learn more about EPA’s efforts to protect children’s health by going to www.epa.gov/ochp.


According to the Centers for Disease Control and Prevention, approximately one in every 33 babies born in the United States is born with a birth defect. Birth defects can heighten the risk of long-term disability as well as increase the risk of illness, potentially impacting a child for the rest of his or her life. Unfortunately, the causes of most birth defects are unknown.

EPA researchers are tapping powerful, high-tech computer systems and models to better determine how prenatal exposure to environmental factors might impact embryo and fetal development. Working on EPA’s Virtual Embryo (v-Embryo™) project, they create computer models of developing body systems and combine them with data from a number of EPA studies and toxicity databases to “virtually” examine the effects of a variety of prenatal exposures.

Virtual Embryo simulates how chemicals and pesticides, including those that disrupt the endocrine system, interact with important biological processes that could disrupt fetal development.  The chemicals used in simulations are identified by EPA’s Toxicity Forecaster as having the potential to affect development.

The predictions from the computer simulations need to be further tested against non-virtual observations. However, the models provide scientists with a powerful tool for screening and prioritizing the chemicals that need to be more closely examined, greatly reducing the cost and number of targeted studies needed.

“We’ve built small prototype systems, now what we want to do is move into complex systems models that will be more relevant to environmental predictions,” said Thomas B. Knudsen, Ph.D., an EPA systems biologist who is leading the project.

Virtual Embryo models have focused on blood vessel development and limb development, but are being expanded to include early development of the male reproductive system, which is known to be particularly sensitive to endocrine disrupting chemicals.

Knudsen says that having more models is important because different chemicals can affect biological systems in various ways. Luckily, the time it takes to develop new models decreases as researchers’ model-developing knowledge grows.

“The important challenge for us is to try to integrate some of this work with other issues of broad importance to children’s health,” said Knudsen. “We’re focused primarily on embryonic development, but a person doesn’t stop developing at birth. We have to take what we are learning from the embryo and extend that information into life stages beyond birth.”

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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Scientist at Work: Interview with Thomas Knudsen

Dr. Tom Knudsen is a developmental systems biologist at EPA’s Center for Computational Toxicology. His research focuses on developing predictive models of developmental toxicity, building and testing sophisticated computer models such as the Virtual Embryo Project. This effort explores the potential for chemicals to disrupt prenatal development—one of the most important lifestages.

In addition to his research at EPA, Dr. Knudsen is an Adjunct Professor at the University of Louisville, Editor-in-Chief of the scientific journal Reproductive Toxicology, and Past-President of the Teratology Society.

Before joining EPA, he was Professor at the University of Louisville.

How does your science matter?

I am part of an exciting effort to develop new ways to explore development toxicology and prioritize the testing of chemicals using vast amounts of data and biological knowledge, powerful computers, sophisticated computer models and very large databases. Instead of the conventional approach to developmental toxicology, which over the past 50 years or so has relied on tests conducted on pregnant lab animals, we are developing virtual models that are both faster and less expensive.

For example, in the Virtual Embryo project we are using a suite of screening models that look at the interactions of various chemicals with the complex biology of a developing embryo. We think that these models and tools will be a new way of asking questions about how a pregnant woman’s exposure to chemicals in the environment might result in a risk to development.

Our work will help protect human health, greatly increase the number of chemicals we can screen quickly, and reduce costs all at the same time. So I guess it really does matter.

What do you like most about your research?

Most days I feel like I have the best job in the country!

The team that I work with consists of bright and exceptionally talented scientists, among them more than a half dozen outstanding young scientists and post-doctoral fellows. As a like-minded team, we strive to unravel complexity in a biological system such as the embryo.

I really enjoy the many opportunities for productive collaboration here at EPA. The opportunity to conceptualize the Virtual Embryo Project and see it grow and evolve has been most gratifying, not only because of the innovative science that it allows, but also because of the opportunities that it presents for professional development of young scientists.

Click here to keep reading Thomas’s interview.

To read more Scientists at Work interviews, click here.

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.