Independent Peer Review of the TCEQ's Revisions to Guidelines to Develop Effects Screening Levels, Reference Values, and Unit Risk Factors
What: Peer Review of Revisions to Guidelines to Develop Effects Screening Levels, Reference Values, and Unit Risk Factors (RG-442) by the Texas Commission on Environmental Quality
Where: This review will be conducted as a letter review only.
When: Final Report Available
Public Comments: Public comments will be accepted via email and will be included as an appendix to the final peer review report. All submitted comments must have your name, organization, mailing address, and email address. All comments should be submitted as a Word file and can be directly emailed to Ms. Alison Willis at email@example.com. Comments are due by July 15, 2011.
In 2006, The Toxicology Division (TD) of the Chief Engineer’s Office released a technical guide (RG-442) used by the Texas Commission on Environmental Quality (TCEQ) to develop Effects Screening Levels (ESLs), inhalation Reference Values (ReVs), and inhalation Unit Risk Factors (URFs). Although this document was primarily written as guidance for the TCEQ staff, it also documented the processes used to develop ESLs, ReVs, and URFs for any interested person with training in inhalation toxicology and risk assessment. ESLs are chemical-specific air concentrations set to protect human health and welfare. Short-term ESLs are based on data concerning acute health effects, the potential for odors to be a nuisance, and effects on vegetation, while long-term ESLs are based on data concerning chronic health and vegetation effects. Welfare-based ESLs (odor and vegetation) are set based on effect threshold concentrations. Health-based ESLs, however, are calculated from ReV and URF toxicity factors. ReVs and URFs are based on the most sensitive adverse health effect relevant to humans. Derivation of a ReV or URF begins with a toxicity assessment involving hazard identification and dose-response assessment based on the chemical’s mode of action. The resulting ReVs and URFs are then used to calculate ESLs that correspond to no significant risk levels.
The Texas Clean Air Act (Chapter 382 of the Texas Health and Safety Code (THSC)) specifically mandates the TCEQ to conduct air permit reviews of all new and modified facilities to ensure that the operation of a proposed facility will not cause or contribute to a condition of air pollution. Because of the comprehensiveness of the language in the THSC, the methods were developed so that ESLs could be derived for as many air contaminants as possible, even for chemicals with limited toxicity data.
Since 2006, new scientific developments in toxicology and risk assessment have resulted in changes to some risk assessment approaches. As a result, the TD has prepared new guidelines that will be entitled “Revisions to Guidelines to Develop Effects Screening Levels, Reference Values, and Unit Risk Factors.” The revised guidelines will contain significant revisions since 2006 including changes to the procedures for developing odor –based ESLs, consideration of the differences between children and adults when assessing risk, identification of health-based effect levels, development of 24-hour acute reference values, guidance on how to determine if an effect is adverse, hazard identification and dose-response modeling of epidemiology studies, and development of oral reference dose (RfD) and oral cancer slope factor (SFo) values. Because of the sweeping changes made to the guidelines, TCEQ has engaged TERA to conduct a letter peer review of the revised guidelines.
▪ Guidelines to Develop Inhalation and Oral Cancer and Non-Cancer Toxicity Factors
▪ Charge to Reviewers
▪ Reviewer Bios
For more information, contact Joan Strawson at Strawson@tera.org or 910.528.9768