The naturally occurring phytotoxin ptaquiloside (PTA) has long been known to be both acute toxic and carcinogenic. Contents of more than 1% ptaquiloside on dry weight has been detected in bracken (Pteridium spp.), a fern distributed across the globe in often dense populations. This work focused on the fate of PTA in the soil-water system, from where it may leach to drinking water sources.

PTA was detected in concentrations up to 2.2 µg/L in natural waters receiving drainage from bracken populations, and was found in both surface and groundwater. It was shown that ptaquiloside leached off bracken fronds (the leaves of ferns) in concentrations up to 169 µ/L during rainfall events. Rainfall further determined the concentration in a stream that drained a bracken-covered catchment, suggesting that this is a potent driver of ptaquiloside exposure in the environment. In both pure and natural waters, pH and temperature governed the stability of PTA, with fast decomposition at pH extremes and/or high temperatures. At slightly acidic pH and at temperatures relevant for groundwater, PTA may be stable for months. The effect of standard water treatment procedures has not yet been explored, and dilution from non-bracken areas will generally limit the risk of human exposure where water is sourced from larger catchments.