How to Use the TTC Method for Evaluating Impurities in Cosmetic Ingredients in China

In China, when conducting risk assessments for cosmetics, all components must be evaluated. Typically, for impurities present at very low levels that lack toxicological data, the Threshold of Toxicological Concern (TTC) method can be used for assessment.

Q: What is TTC?

A: TTC is a risk assessment approach that assumes a chemical substance poses an extremely low risk to human health if its exposure dose is below a certain threshold. Substances meeting this threshold are deemed safe.

Q: What are the advantages of TTC?

A: When assessing impurities, the lack of toxicological data is common. The TTC method avoids animal testing, reducing costs and ethical concerns.

Q: Which substances are not suitable for the TTC method?

A: The TTC method does not apply to the following: Potent carcinogens, Inorganic substances, Metals and organometallic compounds, Proteins, Steroids, Substances with known or predicted bioaccumulation potential, Nanomaterials, Radioactive substances and Mixtures with undefined chemical structures.

Additionally, in China’s cosmetic risk assessment process, the TTC method cannot be used for ingredients with inhalation exposure risks (during inhalation pathway assessments) and ingredients with preservative, UV-filtering, coloring, hair-dyeing, or whitening functions.

Q: How to use TTC?

A: First, classify the substance using tools like Toxtree to determine its appropriate Cramer classification (Class I, II, or III). Then, combine this classification with the substance’s exposure data to conclude whether it is safe.

Q: How are TTC thresholds defined in China’s cosmetic risk assessments?

A: The thresholds for Cramer Class I: 46 µg/kg body weight/day. The thresholds for Cramer Classes II & III: 2.3 µg/kg body weight/day.

Author

Michael Chang, PhD – Chief Technical Officer, DABT, DCST, CIRS China

Michael graduated from the University of Science and Technology of China. He is a leading technical expert in the risk assessment of chemicals in China. Since 2011, his team has completed more than 300 REACH LR projects and has prepared more than 1,000 risk assessment reports for registration in the EU and China. All reports have been accepted by the authorities. His team has also compiled thousands of SDSs for global enterprises.

He is proficient in various chemical risk assessment software and QSAR models such as EPA-SUIT, QSAR toolbox, VEGA, lUCLID 6, and CHESAR.

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