From: Andy Soos, ENN
Published March 17, 2011 06:11 PM

How To Test for Toxicity

There are zillions of products and chemicals in the world. Some are obviously toxic. Others are more subtle or simply unknown because they were never studied. Study is expensive and time consuming. Several federal agencies have unveiled a new high-speed robot screening system that will test 10,000 different chemicals for potential toxicity. The system marks the beginning of a new phase of an ongoing collaboration, referred to as Tox21, that is working to protect people’s health by improving how chemicals are tested in this country. The robot system, which is located at the National Institutes of Health Chemical Genomics Center (NCGC), was purchased as part of the Tox21 collaboration established in 2008 between the U.S. Environmental Protection Agency (EPA), the National Institute of Environmental Health Sciences National Toxicology Program, and NCGC, with the addition of the U.S. Food and Drug Administration (FDA) in 2010. Tox21 merges existing resources – research, funding and testing tools – to develop ways to more effectively predict how chemicals will affect human health and the environment.


The 10,000 chemicals the robot system will screen include chemicals found in industrial and consumer products, food additives and drugs. Testing results will provide information useful for evaluating if these chemicals have the potential to disrupt human body processes enough to lead to adverse health effects.

"Tox21 has used robots to screen chemicals since 2008, but this new robot system is dedicated to screening a much larger compound library," said NHGRI Director Eric Green, M.D., Ph.D. The director of the NCGC at NHGRI.

Christopher Austin, M.D.EPA launched ToxCast in 2007 to develop ways to predict potential toxicity and to develop a cost-effective approach for prioritizing the thousands of chemicals that need toxicity testing.

The system uses advanced science tools to help understand how human body processes are impacted by exposures to chemicals and helps determine which exposures are most likely to lead to adverse health effects.

It includes over 500 state-of-the-art rapid tests (called high-throughput assays) that are screening 1,000 environmental chemicals for potential toxicity.  Phase I was completed in 2009 and it profiled over 300 well studied chemicals (primarily pesticides). Data is available from the high-throughput assays is available via the ToxCast Database.  Toxicity signatures from ToxCast are defined and evaluated by how well they predict outcomes from mammalian toxicity tests and identify potential toxicity pathways relevant to human health effects.

Phase I chemicals have over 30 years worth of existing toxicity data since they have been tested already using traditional toxicology methods (primarily animal studies). Data from animal studies can be searched and queried using EPA's Toxicity Reference Database (ToxRefDB) that stores nearly $2 billion worth of studies.

"The addition of this new robot system will allow the National Toxicology Program to advance its mission of testing chemicals smarter, better, and faster,” said Linda Birnbaum, Ph.D., NIEHS and NTP director. “We will be able to more quickly provide information about potentially dangerous substances to health and regulatory decision makers, and others, so they can make informed decisions to protect public health."

Tox21 has already screened more than 2,500 chemicals for potential toxicity using robots and other innovative chemical screening technologies. The Tox21 chemical screening technologies were used to screen the different types of oil spill dispersants for potential endocrine activity during the BP oil spill in the Gulf of Mexico last year.

Though more testing can be done, the correct interpretation of the results is still necessary.

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