Toxicity Testing for the 21st Century: A New Standard

The Physicians Committee

Toxicity Testing for the 21st Century: A New Standard

Collecting enough information to ensure safer chemicals under TSCA requires a shift to human relevant, high-throughput testing methods and strategies. Since these methods do not involve the use of animals, they are often referred to as “alternative methods.” Over the next few years, these “alternatives” will become the new standard for toxicology testing because they offer indisputable scientific, practical, and ethical advantages.

The blueprint for development and implementation of these alternatives is the National Research Council report, Toxicity Testing in the 21st Century: A Vision and a Strategy in 2007.

“Tox21”—short for “21st century toxicology”—has become synonymous with approaches for modernizing toxicity testing and assessment of chemicals. Tox21 is also the name of the collaboration between selected U.S. government agencies, including the Environmental Protection Agency (EPA) and the National Institutes of Health (NIH).

“This report envisions a not-so-distant future in which virtually all routine toxicity testing would be conducted in human cells or cell lines in vitro by evaluating perturbations of cellular responses in a suite of toxicity pathway assays using high throughput robotic-assisted methodologies.”

Toxicity Testing in the 21st Century: A Vision and a Strategy, National Research Council

The EPA commissioned the writing of the NRC’s landmark toxicity testing report, as it and other scientific bodies had long recognized the inherent shortfalls of the current, animal-based approach.

The “NRC Vision” described in the report outlines a practical plan for revolutionizing toxicity testing by harnessing scientific advances in molecular and cell biology, genetics, robotic testing systems, and computational power. These advances, combined with a robust system of environmental monitoring, will create a system of chemical testing and assessment that is more predictive and more protective of human health.

The NRC Vision is based primarily on new toxicity testing methods that can identify unhealthy changes in normal biological processes in response to a chemical. These tests are conducted in human cells, cell lines, or with cellular components. Changes occur within cells and tissues long before the effects of toxicity would become evident in an animal test. For example, cellular changes that lead up to carcinogenicity can be measured in cells, cell lines, or tissues without the need to look for the eventual disease response—in this case, a tumor —in an animal.

In the NRC Vision, a suite of these tests would replace a single animal test. Each test in the suite would measure different changes that occur in response to a chemical, giving a comprehensive picture of the affect the chemical may have on normal cell and tissue function. These test methods can be automated, so scientists can use machines to test hundreds and even thousands of chemicals at the same time, monitoring most of the possible effects on cells, tissues, and organs resulting from exposure to each chemical. This type of screening is called high throughput screening.

Using this approach, regulatory scientists can simultaneously examine numerous possible health effects of exposure to thousands of chemicals. With these data, they can determine which chemicals present a concern and flag those for further testing, setting aside chemicals that present little or no health concerns. This approach would allow scientists to quickly analyze the backlog of chemicals that may not have undergone rigorous safety testing. That would reduce the amount of uncertainty in the chemical market, optimizing protection of human health and the environment. 

Visit the Resources and FAQ pages for more information about the Tox21 effort and the scientific and policy advances that are already occurring—and those that still need to occur—in order to accomplish it.

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