An ad hoc committee of the National Academies of Sciences, Engineering, and Medicine will conduct a scientific review of the Texas Commission on Environmental Quality (TCEQ) 2020 Ethylene Oxide (EtO) Carcinogenic Dose-Response Assessment Development Support Document, plus appendices 1-5. The committee will review the methods, results, and conclusions of TCEQ’s assessment document and consider whether the conclusions are clearly presented, scientifically supported, and based on the best available scientific information.
Aspects that will be considered during the peer review include:

1. The overall weight of the evidence for a causal relationship between ethylene oxide and breast cancer risk in humans at occupational concentrations and at environmentally relevant concentrations of ethylene oxide in ambient air.

2. The dose-response assessment for ethylene oxide, including:

a. the appropriateness of the selected cancer endpoint(s), key data set for modeling, dose-response model, shape of the dose-response curve, and model fit criteria, in the context of relevant mode of action information;

b. the model accuracy and validation analyses for lymphoid cancer and the conclusions based on those analyses, as well as the additional analyses that assumed a healthy worker effect for lymphoid cancer mortality; and

c. any implications of the endogenous production of ethylene oxide, including from the perspective of biological significance, for risk-based air concentrations.

3. Any additional relevant comments or issues about the TCEQ’s carcinogenic hazard and dose-response assessment of EtO.

Recommendations will be prioritized as follows:

• Tier 1: recommended revisions that are important for TCEQ to consider and address to improve critical scientific concepts, issues, or narrative in the assessment.
• Tier 2: suggested revisions that are encouraged to strengthen or clarify the scientific concepts, issues, or narrative in the assessment but are not critical. Other factors, such as agency practices and resources, might need to be considered by TCEQ before undertaking the revisions.
• Tier 3: considerations that might inform future evaluations of key science issues or inform development of future assessments.