Section 1: Why do we need new approaches for evaluating chemical risks?

The Environmental Protection Agency (EPA) faces daunting challenges when it comes to evaluating the health and environmental effects of chemicals. The problem is three-fold. First, there is a tremendous gap between the growing number of chemicals in commerce and the available data on their health and environmental effects. This is partly due to the shortcomings of the Toxic Substances Control Act (TSCA) [for further explanation, see EDF Senior Scientist Richard Denison's dicussion of key elements for TSCA reform]. Second, advances in scientific research in recent decades have identified new factors to consider in evaluating chemical risks, such as: the effects of low-dose exposures and differential effects based on the timing of exposure; epigenetic and genetic variability in the population; co-exposures to multiple chemicals as well as other factors such as nutrition and stress; and an expanding diversity of potential adverse endpoints. Third, current methods tell us very little about how chemicals act and can miss subtle but nonetheless serious effects that aren’t easily detected by looking for obvious effects in whole animals.

These challenges cannot be met by relying solely on traditional animal-based testing methods—as has been done for decades. Animal testing is time-consuming and costly—both in terms of monetary costs and laboratory animal lives. We cannot fill the data gap and answer the critical questions necessary to evaluate chemical safety in any realistic time frame by traditional testing on animals alone.

In an effort to confront these challenges, EPA (in partnership with other agencies) is investing in the development of new approaches and methods for testing and assessing chemicals. This investment reflects the recognition that traditional, animal-based testing methods cannot by themselves efficiently overcome the policy and scientific challenges facing chemical risk assessment today. The future of toxicity testing must include greater use of higher-throughput, testing methods (using both non-animal tests and tests in novel animal models such as zebrafish), as well as computer modeling. Such methods hold promise not only to allow testing of more chemicals at lower cost, but also to elucidate the underlying mechanisms by which chemicals interact with our biology and, ultimately, pave the way for more accurate and efficient prediction of chemical risks.

But modernizing the approach to testing chemicals is itself a daunting task. If this future vision for toxicity testing is to fulfill the promise of providing more and better information about more chemicals to strengthen our understanding of their potential effects on our health, then we need the active engagement of organizations and researchers dedicated to improving public health in the development and use of the emerging methods. EDF developed this primer to serve as a first step towards fostering this engagement by providing a general introduction to the new testing approaches and the programs underway at the EPA.

To learn the basics behind one of the most developed of these new testing approaches, proceed to Section 2: Introduction to high-throughput in vitro testing.

Graphic of pregnant woman

Fetal development is a particularly susceptible “window of exposure” for harmful chemicals.


We cannot fill the data gap and answer the critical questions…by traditional [chemical] testing on animals alone.