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Supporting Decisions By the Pie Slice: EPA Researcher Serves Up Data

An EPA statistician is developing innovative ways to translate vast quantities of toxicological data into an accessible, visual format.

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A picture paints a thousand words. Knowledge is power but too much information can overwhelm. An expert makes decisions easier by knowing what to pay attention to and what to ignore. Exit EPA Disclaimer These sayings apply to the work of David Reif, Ph.D., an EPA statistician and geneticist who is developing innovative ways of harnessing huge amounts of information on toxic chemicals to better protect human health and the environment.

Reif has developed a new tool, called the Toxicological Priority Index (ToxPi), which profiles the interactions of chemicals with biological processes in ways the public and decision makers can easily understand. This is especially important because modern scientific methods are generating such a deluge of data that scientists say it can be overwhelming.

Using simple “pie slices” and other visual graphics, Reif can succinctly convey extensive scientific information about how some chemicals interact with the endocrine system, the body’s systems of glands and hormones.  EPA is concerned with effects on the endocrine system because it regulates critical bodily functions such as growth, metabolism, and sexual development.  When these functions are disrupted, the effects can lead to serious health problems, including infertility, birth defects and cancer, sometimes years after exposure.  

ToxPi helps EPA officials and others to better understand environmental chemicals, prioritize those that warrant further testing, and can act as a check on existing chemical test results. The tool was developed as part of EPA’s ToxCast™ program, which takes a broad perspective in evaluating chemicals, and maps their “toxicological signatures” to specific biochemical pathways in the body.

“ToxPi presents information in such a way that experts and the public alike can ‘look under the hood’ as we make all our data available,” Reif says. The larger and more numerous the “slices of pie” in ToxPi figures, the more potentially negative health impacts they may have (See Figure 2 below on the chemicals Bisphenol A and Tebuthiuron from an EPA factsheet (PDF) (2 pp, 243 KB)).

ToxPi Figure

Above illustrates ToxPi "slices" for two chemicals: Bisphenol A (BPA), which is used in plastics, and Tebuthiuron, a herbicide. Different colors show results from various types of vitro assays, or tests, conducted to measure endocrine activity caused by the chemical. The larger green "slice" pointing to 2 o’clock for BPA, for example, illustrates that it produced a more potent reaction in estrogen receptor assays as compared to Tebuthiuron. BPA also ranks above Tebuthiuron in all other ToxPi slices.

The impetus for Reif’s development of decision-support tools, such as ToxPi, was new pesticide and drinking water laws mandating unique chemical testing regimens. These laws call on EPA to develop a screening program to assess the potential for chemicals to interact with the endocrine system. Because of their potential to disrupt still developing systems, endocrine disrupting chemicals are a high priority at EPA as it works to protect babies, infants, and others in the early life stages. Reif works with an interdisciplinary team that has already applied ToxPi to 309 chemicals, including 52 singled out for endocrine screening.  

The tool provides a science-based and efficient way to prioritize chemicals for the new endocrine screening program. The screening prioritization process is supported by ToxPi’s impartial method for selecting chemicals for testing. ToxPi both adds to the reliability of information available for test chemical ranking and makes it understandable. The colored graphs generated by the tool illustrate “why we’re selecting this chemical for further testing,” Reif explains.

ToxPi also saves costs by avoiding redundant testing and reduces the number of test animals required for evaluating chemicals. In addition, it focuses research on the impacts of greatest concern. Reif also says the tool is transparent and flexible in that new information can always be integrated into a chemical’s profile as it is collected.

Other unique patterns of biochemical impacts can be illustrated by the tool beyond the endocrine system. Some EPA researchers are applying it to the growth of embryos to understand developmental toxicity and others are applying it to the human liver. In upcoming rounds of research, EPA plans to scale up the effort from around 300 to more than a thousand chemicals and will include exposure information, increasing the tool’s reach and utility.

For Reif, representing vast amounts of knowledge in visual ways can lead to powerful new insights that allow decision makers, researchers and the public to broaden their understanding, refine their priorities and be familiar with the science base needed for more effective environmental research and action. “Working with my ToxCast™ colleagues exposes me to multiple perspectives and disciplines. ToxPi allows us to bring these perspectives together in unique and accurate ways,” says Reif.


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