EMA's HMPC (Committee on Herbal Medicinal Products) has revised the questions & answers document on (traditional) herbal medicines.
With revision 5 the following question was added to the Q&A document as compared to the previous version number 4 from August 2014.
Is testing of benzene (class 1 solvent) for herbal preparations necessary?
Some solvents used for extraction, purification or during manufacture of a herbal preparation may contain benzene as an impurity. As a consequence, there might be benzene residues in herbal preparations.
The most commonly used solvents for the manufacture of herbal preparations are ethanol and water or combinations thereof. Ethanol of chemical origin may contain benzene as an impurity whereas ethanol obtained from fermentation does not normally contain any benzene. Therefore the production process of ethanol used in herbal preparations should be taken into account.
Ethanol, methanol and acetone complying with their European Pharmacopoeia monographs should not exceed 2 ppm of benzene, which is the ICH limit. Therefore, the content of benzene in other solvents should not exceed the ICH limit of 2 ppm either. Where solvents exceeding the ICH limit are used, potential benzene residues should be identified and quantified.
You can find the further explanations on this question on the testing of benzene under question 10 on page 7/19.
To get more details please see the complete Q&A document "Questions & answers on quality of herbal medicinal products/traditional herbal medicinal products".