Ptaquiloside (PTA), caudatoside (CAU) and ptesculentoside (PTE) are carcinogenic illudane glycosides found in bracken ferns (Pteridium spp.) world-wide. The environmentally mobile PTA entails both acute and chronic toxicity and comparable risk might be associated with the structurally similar CAU and PTE. It is of great concern if these compounds are present in drinking water wells in bracken dominated regions, since they might pose a threat to human health. This study investigates the presence of PTA, CAU, PTE, and their corresponding hydrolysis products pterosins B (PtB), A (PtA) and G (PtG) in water wells in Denmark, Sweden and Spain. In total, 77 water samples from deep groundwater wells (40 – 100 m) and shallow water wells (8 – 40 m) were collected and preserved in the field, pre-concentrated in the laboratory and analysed by liquid chromatography-mass spectrometry (LC-MS).
Deep groundwater wells contained neither illudane glycosides nor their pterosins. However, seven private shallow wells contained at least one of the illudane glycosides and/or pterosins at concentrations up to 0.27 µg L-1 (PTA), 0.75 µg L-1 (CAU), 0.05 µg L-1 (PtB), 0.03 µg L-1 (PtA) and 0.28 µg L-1 (PtG).
Detected concentrations of illudane glycosides in some of investigated wells exceeded the suggested maximum tolerable concentrations of PTA, although they were used for drinking water purpose. Contaminated wells were characterized by shallow depth, lower pH and electrical conductivity compared to deep groundwater wells where no illudane glycosides or pterosins were found.