Non-animal Risk Assessment for Isothiazolinones

In May 2020, EPA requested comment on draft human health and ecological risk assessments for a group of antimicrobial chemicals known as isothiazolinones. Isothiazolinones are used in a variety of products including plastics, household cleaners, and laundry detergents. They frequently cause skin sensitization.

EPA requested comment on the use of an in vitro and artificial neural network-based defined approach instead of using laboratory animal data to evaluate skin sensitization risks for products containing isothiazolinones. This is the first use of this type of defined approach in regulatory risk assessment.

EPA Draft Document: Hazard Characterization of Isothiazolinones in Support of FIFRA Registration Review (April 2020)

The draft risk assessments rely heavily on work done by NTP, NICEATM, and ICCVAM. The in vitro testing was conducted by the NTP Toxicology Branch. NICEATM analyzed the in vitro data and ran the artificial neural network-based defined approach to provide quantitative potency predictions used to determine points of departure. The ICCVAM Skin Sensitization Expert Group reviewed the NTP testing report and the NICEATM analyses before data were provided to EPA for development of the risk assessments. Strickland et al. (2022) described the application of defined approaches to potency classification of isothiozolinones.


Application of Non-animal Test Methods and Defined Approaches to Skin Sensitization Assessment of Isothiazolinone Compounds (June 2020)

Report sections:

  • Main body
  • Appendix A: Burleson Research Technologies, Inc. In Vitro Testing Results
  • Appendix B: Institute for In Vitro Sciences, Inc. h-CLAT Testing Results
  • Appendix C: LLNA Data
  • Appendix D: In Vivo, In Vitro, In Silico, and Defined Approach Results
  • Appendix E: Calculation of Weighted LLNA EC3 for CMIT/MIT