A recent memorandum from the Environmental Protection Agency (EPA) shared comments from peer reviewers on the 2023 draft risk evaluation for Tris(2-chloroethyl) Phosphate (TCEP). This chemical, primarily used as a flame retardant and plasticizer, is undergoing evaluation due to potential environmental and health risks. The peer reviewers provided insights on various aspects of the evaluation, particularly focusing on fate assessment, hazard assessment, and exposure analysis.
Fate Assessment: Extrapolating Anaerobic Degradation
In the absence of specific anaerobic degradation data for TCEP, EPA's methodology assumed that degradation rates are 4 to 9 times slower than under aerobic conditions. Reviewers largely supported this approach as a reasonable estimate, despite some reservations about its accuracy. One reviewer recommended considering newer research for additional insights.
Hazard Assessment: Environmental and Human Health Impacts
Using the Web-ICE application, EPA estimated TCEP's acute toxicity to aquatic species and calculated the hazardous concentration for 5% of species (HC05). Reviewers supported using Web-ICE but recommended incorporating more empirical data to improve the species sensitivity distribution and HC05 estimates. They emphasized the importance of better integrating Web-ICE predictions with additional sources, like the Japan Chemicals Collaborative Knowledge database.
For human health effects, EPA's evidence integration tables evaluated TCEP's potential impact across various endpoints, including neurotoxicity, reproductive toxicity, developmental toxicity, kidney toxicity, and cancer. The reviewers acknowledged the process improvements in systematic review and supported EPA’s overall confidence ratings, which were moderate for each endpoint. They noted that the evidence was sufficient to conclude TCEP's likely neurotoxic and carcinogenic effects, but called for further examination of its developmental impact.
Exposure Analysis and Future Research
Peer reviewers discussed the importance of refining the approach to exposure analysis. The draft evaluation made strides in using advanced models like AERMOD for estimating air deposition and Verner 2008 for assessing infant exposure through human milk. While they acknowledged the progress, they also stressed the need for further research into TCEP's environmental persistence and health impacts to improve regulatory decisions.
EPA's efforts to incorporate peer reviewer feedback into the final risk evaluation for TCEP will be crucial in shaping regulations for this widely-used chemical. The agency aims to publish its final report with comprehensive risk characterization and determination by 2025.
