Nelms_Evaluating potential refinements to existing Thresholds of Toxicological Concern (TTC) values for environmentally-relevant compounds

Metadata Updated: January 14, 2021

The Toxic Substances Control Act (TSCA) mandates the US EPA perform risk-based prioritisation of chemicals in commerce and then, for high-priority substances, develop risk evaluations that integrate toxicity data with exposure information. One approach being considered for chemicals with limited chemical-specific toxicity data is a Threshold of Toxicological Concern (TTC)-to-Exposure ratio. Here, TTC values derived using oral (sub)chronic No Observable (Adverse) Effect Level (NO(A)EL) data from the EPA’s Toxicity Values database (ToxValDB) were compared with published TTC values from Munro et al. (1996). 4554 chemicals with structures present in ToxValDB were assigned into their respective TTC categories using the Toxtree software tool. Chemicals were assigned into the five TTC classes (Cramer structural class I, II, III, containing alerts for genotoxicity and acetylcholinesterase inhibitors). 114 (2.5%) chemicals were determined to be not appropriate for TTC. The TTC values derived from the ToxValDB were similar, but not identical to the Munro TTC values: Cramer I (37.3 compared to 30 ug/kg-day), Cramer II (34.6 compared to 9 ug/kg-day) and Cramer III (3.9 compared to 1.5 ug/kg-day). The 5th percentile values of Cramer classes I and II for the ToxValDB and Munro datasets were not statistically different whereas the class III 5th percentile values were different. Chemical features of the two class III datasets were evaluated to account for the differences in TTC values. The revised Kroes workflow was then applied to a large set of chemicals (~45,000). TTC values derived from this expanded dataset of toxicity values substantiated the original TTC values derived by Munro et al. (1996), reaffirming the utility of TTC as a promising tool in a risk-based prioritisation approach.

This dataset is associated with the following publication: Nelms, M., P. Pradeep, and G. Patlewicz. Evaluating potential refinements to existing Thresholds of Toxicological Concern (TTC) values for environmentally-relevant compounds. REGULATORY TOXICOLOGY AND PHARMACOLOGY. Elsevier Science Ltd, New York, NY, USA, 109: 104505, (2019).

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Public: This dataset is intended for public access and use. License: See this page for license information.

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References

https://doi.org/10.1016/j.yrtph.2019.104505

Dates

Metadata Created Date January 14, 2021
Metadata Updated Date January 14, 2021

Metadata Source

Harvested from EPA ScienceHub

Additional Metadata

Resource Type Dataset
Metadata Created Date January 14, 2021
Metadata Updated Date January 14, 2021
Publisher U.S. EPA Office of Research and Development (ORD)
Unique Identifier Unknown
Maintainer
Identifier https://doi.org/10.23719/1504178
Data Last Modified 2019-10-15
Public Access Level public
Bureau Code 020:00
Schema Version https://project-open-data.cio.gov/v1.1/schema
License https://pasteur.epa.gov/license/sciencehub-license.html
Program Code 020:095
Publisher Hierarchy U.S. Government > U.S. Environmental Protection Agency > U.S. EPA Office of Research and Development (ORD)
Related Documents https://doi.org/10.1016/j.yrtph.2019.104505
Source Datajson Identifier True
Source Hash 0ef15d8aea8f777f180a87ecf575619506dcab79
Source Schema Version 1.1

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