Researchers sampled 103 dried herb food supplements on sale in Bulgaria and analyses them using macro- and microscopic tests.
They found that the majority of samples failed to meet specification and that there was widespread adulteration and foreign body contamination. 17.5% of samples contained species which are prohibited for consumption due to their pyrrolizidine alkaloid content.
This work implies the need for strengthening control of herbs and spices.
Read the full paper.