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Toxicology Position Papers and White Papers

A compilation of papers written by the TCEQ Toxicology Division.

This position paper was included as Section 2.2 of the 2015 updated RG-442.

The Texas Commission on Environmental Quality revised Section 2.2, Odor-Based ESLs, of Guidelines to Develop Toxicity Factors (publication RG-442) (TCEQ 2012). This position paper was developed to describe how TCEQ toxicologists (1) evaluate available chemical-specific data for chemicals proposed for derivation, and (2) conduct analysis to determine whether development of an odor-based value is needed to prevent odor nuisance conditions. The TCEQ sought public comments on this position paper and a proposed odor ESL list and received several comments. The response to public comments addresses comments received on both of these documents. The list of odor valuesMicrosoft Excel Document represents the substances that the TCEQ has determined have a need for an odor value (i.e., these substances are a product of following the position paper.

Please query the Toxicity Factor Database to search for toxicity factors (including AMCVs and ESLs) to see which value is to be used for permitting purposes (i.e., odor or short-term health).


This Whitepaper directs that, as part of our literature search and review of the available data (during our DSD development process), we will look for any evidence of racial variability in toxicodynamics or toxicokinetics of the chemical's response. If there is significant evidence that shows a particular race is more sensitive to a chemical’s effect(s), this information will be taken into consideration when deriving the chemical toxicity factors.

This Whitepaper supplements the 2015 Texas Commission on Environmental Quality (TCEQ) Guidelines to Develop Toxicity Factors [hereafter referred to as the 2015 updated RG-442].

The TCEQ proposed these guidelines for public comment in April 2017 and posted the final white paper along with the response to public comments in December 2017. This document is not intended to be an explicit instruction manual, but rather a guide to use for any chemical evaluation.

Response to Public Comments

This Whitepaper was included as section 4.6 in the 2015 updated RG-442].

The TCEQ sought public comments on a white paper about its guidelines for developing chemical-specific 24-hour inhalation reference values—a supplement to the 2012 version of publication RG-442. Reference values are used in air monitoring as comparison values. The 24-hour guidelines went through an external peer review, as discussed in the document description and intended use. The TCEQ posted these guidelines for a second public comment period; the document was finalized in June 2014. Please refer to the White Paper to review the final draft.

Response to Public Comments

This Whitepaper was updated in section 3.9.1 in the 2015 updated RG-442].

The Toxicology Division amended Section 3.9.1, “Default Dosimetry Adjustments for Gases,” in the October 2012 version of RG-442 to include information on animal-to-human inhalation gas-dosimetric adjustments based on recommendations in Advances in Inhalation Gas Dosimetry for Derivation of a Reference Concentration (RfC) and Use in Risk Assessment (U.S. EPA 2012, EPA/600/R-12/044). Please refer to the white paper for a discussion of the changes.

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