Expert Report

Toxicity Testing in the Twenty-first Century: A Vision and a Strategy (2007)

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Advances in molecular biology and toxicology are paving the way for major improvements in the evaluation of the hazards posed by the large number of chemicals found at low levels in the environment. The National Research Council was asked by the U.S. Environmental Protection Agency to review the state of the science and create a far-reaching vision for the future of toxicity testing. The report finds that developing, improving, and validating new laboratory tools based on recent scientific advances could significantly improve our ability to understand the hazards and risks posed by chemicals. This new knowledge would lead to much more informed environmental regulations and dramatically reduce the need for animal testing because the new tests would be based on human cells and cell components. Substantial scientific efforts and resources will be required to leverage these new technologies to realize the vision, but the result will be a more efficient, informative and less costly system for assessing the hazards posed by industrial chemicals and pesticides.

Key Messages

  • A critical factor for success is the conduct of the transformative research to establish the scientific basis of new toxicity-testing tools and to understand the implications of test results and their application in risk assessments used in decision-making.
  • After chemical characterization, decisions might be made about what further testing is required or whether it is needed at all.
  • Chemical characterization is meant to provide insights to key questions, including a compound's stability in the environment, the potential for human exposure, the likely routes of exposure, the potential for bioaccumulation, possible routes of metabolism, and the likely toxicity of the compound and possible metabolites based on chemical structure or physical or chemical characteristics.
  • In the vision proposed, dose-response models would be developed for environmental agents primarily on the basis of data from mechanistic, in vitro assays as described in the toxicity-testing component.
  • In the vision proposed, toxicity testing has two components: toxicity-pathway assays and targeted testing.
  • Population-based and human exposure data are important components of the committee's toxicity-testing strategy. Those data can help to inform each component of the vision and ensure the integrity of the overall testing strategy.
  • Targeted testing would be used to complement toxicity-pathway tests and to ensure adequate evaluation.
  • The committee's vision for toxicity testing is a process that includes chemical characterization, toxicity testing, and dose-response and extrapolation modeling. At each step, population-based and human exposure data are considered, as is the question of what data are needed for decision-making.