New chemical mapping technique could help fill big gaps in safety knowledge

In the U.S., just a tiny fraction of the chemicals used in consumer products have been tested for human health effects. And with the current climate in Congress, it feels unlikely that we’ll see any true reform of the nation’s terribly outdated chemical safety rules anytime soon. In the meantime, scientist Thomas Hartung may have created the next best thing.

In the simplest terms, Hartung and colleagues took what is the world’s largest and richest database of chemical toxicity research — a database produced in accordance with the European Union’s Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) regulations — and designed a computer program that uses that data to predict the toxicity of chemicals for which there is little or no safety data.

According to Hartung, who was actually involved in developing the 2006 REACH regulations and now serves as professor and chair for evidence-based toxicology at Johns Hopkins Bloomberg School of Public Health, the computer program organizes the REACH data into a toxicity map of our current chemical landscape. Organizing the data by toxicity means that researchers can take a substance that hasn’t received safety testing, enter it into the mapping program and — with the click of a mouse — see where it falls on the toxicity map based on chemical similarities it shares with substances that do have a safety record. The mapping process and results were recently published in February in ALTEX: Alternatives to Animal Experimentation.

“This isn’t a replacement for safety testing,” Hartung told me. “But in comparison to what we have, which is essentially no data on thousands of industrial chemicals, this is better than nothing.”

So, where did this mapping idea come from? It goes back to a method known as “read-across,” a common approach used by REACH administrators to fill in gaps in safety knowledge. Read-across, according to the European Chemicals Agency, is a method for predicting unknown properties of one chemical from known properties of similar chemicals. The predictive approach is a commonly used alternative to animal testing under REACH. Hartung has been extremely active in developing and enhancing read-across methods — in fact, just this week, he spoke at a read-across workshop hosted by the U.S. Food and Drug Administration.

The problem, though, is that read-across isn’t easily accessible to the layperson — it takes some technical know-how and knowledge to do it right. On the other hand, Hartung’s new chemical mapping program puts the power of read-across in the hands of everyday people. That’s the idea, anyway, though Hartung is currently being prevented from making the program public. (More on that later.)

To create the chemical toxicity map, Hartung and colleagues downloaded the REACH database of nearly 10,000 registered chemicals and about 800,000 research studies. As it stands, there’s no easy way to search through REACH data unless you know what you’re looking for — a person would have to enter a specific chemical name or toxicity measure and even then, it’s difficult to retrieve a comprehensive safety profile and find similar chemicals. So, Hartung and company wrote 500 pages of code to standardize the data and make it machine-readable. They created a map that groups chemicals by their known toxicities — a map that any computer can read and that makes important human health information accessible by anyone. The map not only has the potential to predict toxicity of the 90,000 chemical substances in consumer products for which there is no safety data, it could also help curb the cost of safety testing and reduce the need for animal testing.

“You can place a substance with no test data into the map, find its neighborhood and infer its safety profile,” said Hartung, who also directs the Johns Hopkins’ Center for Alternatives to Animal Testing. “This is the power.”

For example, Hartung said, the mapping program could help ensure that hazardous consumer product chemicals aren’t simply replaced with different chemicals without a proven safety record. (For an example of this, see our recent coverage of Bisphenol A vs. Bisphenol S.) Hartung also noted that the chemical map wasn’t created to eliminate the need for animal testing, but to reduce unnecessary and redundant animal testing and make current animal testing more precise. For example, he and his colleagues found eye irritation data for 3,500 substances in the REACH database, but more than 9,000 related tests had been done. The finding suggests that lab animals underwent a significant amount of needless testing.

“I’m a physician in a school of public health — my goal is first patient safety,” Hartung said. “But I’m challenging animal testing where other methods can do a better job.”

Hartung is currently in talks with European officials over whether the REACH data he downloaded is part of the public domain or whether the data is owned by the companies that submitted them to the European registry. So, his plan to make the mapping program publicly available is on hold for the moment. However, he and his colleague are moving forward to make the mapping program even better — they hope to add in more data sources, incorporate more sophisticated chemical similarities, hire more programmers and build a Web-based interface.

“Our tool is far from perfect … it’s really only as good as the data of the past,” Hartung told me. “But it’s a tool that can map (the data) we do have and that can nicely show us how much data we don’t have.”

For a full copy of the chemical mapping study, visit ALTEX.

Kim Krisberg is a freelance public health writer living in Austin, Texas, and has been writing about public health for nearly 15 years.

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