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An evaluation of the implementation of the Cramer classification scheme in the Toxtree software
G Patlewicz1, N Jeliazkova, R J Safford
1European Commission, DG Joint Research Centre, Institute for Health and Consumer Protection, Ispra, Italy. patlewig@hotmail.com
SAR and QSAR in Environmental Research
|October 15, 2008
Summary
The Threshold of Toxicological Concern (TTC) concept provides a way to assess chemical safety without extensive testing. The Toxtree software, based on the Cramer scheme, shows promising results for evaluating chemical exposure risks.
Area of Science:
- Toxicology
- Risk Assessment
- Computational Chemistry
Background:
- Human health risk assessment often relies on toxicological thresholds derived from animal studies.
- The Threshold of Toxicological Concern (TTC) establishes a chemical exposure level below which human health risks are negligible.
- TTC allows for waiving chemical testing based on exposure limits and structural/toxicological data.
Purpose of the Study:
- To evaluate the concordance of the Toxtree software, which implements the Cramer structural scheme for TTC assessment.
- To identify potential modifications for improving the accuracy and utility of the Toxtree software.
- To demonstrate the application of the Toxtree software in evaluating chemical datasets.
Main Methods:
- Utilized two published datasets for evaluation.
- Employed the Toxtree software, based on the Cramer (1978) structural scheme, to classify chemical compounds.
- Analyzed and rationalized inconsistencies between Toxtree classifications and reported data.
Main Results:
- Demonstrated good overall concordance between reported classifications and those generated by Toxtree.
- Identified inconsistencies, primarily related to common food components and normal body constituents.
- Proposed software modifications, including updating chemical lists, to enhance accuracy.
Conclusions:
- Toxtree is a valuable tool for systematic chemical evaluation using the Cramer scheme.
- Updates to internal chemical databases within Toxtree are necessary for improved performance.
- The TTC concept, facilitated by tools like Toxtree, offers an efficient approach to chemical risk assessment.
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