Presence of insecticidal veterinary medicines in dandelions (Taraxacum officinalis) in public parks in the Netherlands

This study aimed to investigate the presence of insecticidal veterinary medicines in public parks in the Netherlands, and to establish whether these substances might pose a threat to the local entomofauna. Fifteen parks and two control sites were selected across the country and volunteers collected composite samples of dandelion plants. Samples were collected in 2021, 2022 and 2023. Nine insecticidal veterinary medicines were detected in total, including two isomers of permethrin and two metabolites of fipronil. As four out of the six parent compounds detected (fipronil, imidacloprid, permethrin and dinotefuran) are currently primarily marketed for use on pets, it is plausible that these substances originated from dogs and cats visiting the parks. The other two compounds, etofenprox and phoxim, are likely to have originated from airborne deposition, as earlier studies have reported the presence of these substances in polyurethane air filters and untreated vegetation. However, dinotefuran has never been found in previous studies. At two control sites, dandelions did not contain any veterinary medicines. Toxicological literature indicates that the concentrations of permethrin, imidacloprid, fipronil and its metabolites found are likely to have negative effects on butterflies feeding on the dandelions.