Polycyclic aromatic hydrocarbons (PAHs) are a group of more than hundred compounds that are ubiquitous in our environment. Some of these PAHs are known to be carcinogenic, mutagenic and teratogenic. PAHs have been detected in dried herbs that were cultured in The Netherlands as well as in other European countries above the maximum levels in dried herbs set by the EU (EU, 2015) for benzo(a)pyrene and the sum of the following four PAHs benzo(a)pyrene, benzo[a]anthracene, benzo[b]fluoranteen and chrysene. The origin of these PAHs in herbs is unknown. VNK cultivates, harvests and dries herbs including valerian and would like to identify the source of PAHs to comply to the EU limits for PAHs in herbs. The goal of the present study was to identify the source of PAHs found in valerian root, and to identify possible measures to reduce the concentration of PAHs in valerian root.