Application of the preliminary developmental toxicity screen for chemical hazard identification under the Toxic...

The Office of Toxic Substances (OTS) within the U.S. Environmental Protection Agency (EPA) is authorized to carry forth the mandates of the Toxic Substances Control Act (TSCA). Included among the provisions of TSCA are the development of requirements for testing of "new" and "existing" chemicals that may present an unreasonable risk of injury to health or the environment. There are over 63,000 "existing" chemicals on the TSCA inventory, and EPA in recent years has been receiving an average of over 1,300 submissions for "new" chemicals a year. Since it is illogical and unrealistic to expect that all of these chemicals should be subjected to detailed testing for all potential adverse health and environmental effects, OTS views screening assays as highly useful tools to assign priorities to chemicals for further testing according to standard methodologies. The Chernoff/Kavlock assay (preliminary developmental toxicity screen) was specifically developed to address the need for a developmental toxicity assay to prioritize for further testing the large number of "new" and "existing" chemicals. OTS has been involved in seeking the development of data through the preliminary developmental toxicity screen for purposes of validating the screen and to obtain critical data necessary for evaluating chemicals. OTS believes that the screen has a role in the risk assessment process and has developed a testing protocol, which is included along with other OTS test guidelines; has provided internal guidance on when the screen may be recommended; and has discussed how the data may be applied in prioritizing chemicals for further study.