The Future of Toxicity Testing for Environmental Contaminants

Guest Editorial | The future of toxicity testing Toxicity testing and assessment sit on the cusp of a transformational change brought about by the rapid emergence of tools and capabilities in molecular biology and computational and informational sciences. This transformation has the potential to dramatically reshape the philosophy and approaches underlying toxicity testing and the assessment of human health risks associated with exposure to environmental contaminants. Such a transformation is especially significant for agencies that are responsible for implementing congressionally mandated programs under which the risks of exposure to a wide variety of environmental pollutants are assessed and regulated. Most often, such regulatory decisions have relied on toxicity testing data obtained nearly exclusively from experimental animal models. This approach, however, presents challenges in accommodating the need for more efficient and cost-effective means to screen and prioritize chemicals for testing and addressing increasingly complex issues such as life-stage susceptibility and genetic variations in the human population, the risks of concurrent, cumulative exposure to multiple and diverse chemicals, and, fundamental to all, improved understanding of the mechanism through which toxicity occurs. The U.S. Environmental Protection Agency (EPA) has recognized the potential application of emerging science to improve toxicity testing and risk assessment (U.S. EPA 2002, 2004), notably by taking the lead in commissioning the National Research Council (NRC) in 2004 to review existing strategies (NRC 2006) and develop a long-range vision for toxicity testing and risk assessment (NRC 2007). Beyond EPA, other federal programs have also recognized the need for this transformative shift, as reflected in the National Toxicology Program's (NTP) A National Toxicology Program for the 21st Century: Roadmap for the Future (NTP 2004) and the Food and Drug Administration's FDA's Critical Path Initiative (FDA 2008). to provide a framework for EPA to comprehensively move forward to incorporate this new scientific paradigm into future toxicity testing and risk assessment practices. The strategy is centered on three interrelated issues: a) the use of toxicity pathways information in screening and prioritization of chemicals for further testing; b) the use of toxicity pathways information in risk assessment; and c) organizational transition. The last element explicitly recognizes that regulatory offices within EPA will need to be actively involved in overseeing the significant transition to this new paradigm and the translation of the attendant data for regulatory application. Research to address the first issue will build on the efforts of EPA's ToxCast program in identifying and …