Leaching behavior and ecotoxicological effects of different game shot materials in freshwater

Lead-based game shot used in hunting near waters is considered a main reason for lead-poisoning of waterfowl and aquatic organisms, prompting discussion about alternatives. This study provides a first comparison of the leaching behavior and resulting ecotoxicological impacts of shot exposed to freshwater, comprising lead-based and alternative shots containing bismuth, copper, steel, tungsten, and zinc. Ecotoxicological effect assessment was based on the acute Daphnia magna 48 h toxicity test according to the EN ISO 6341:2012 guideline. Strong leaching of copper (up to 4.22 μmol/L) and zinc (up to 41.12 μmol/L) from three types of alternative game shot caused significantly increased immobilization rates of up to 100%. In contrast, even the highest leaching of lead did not significantly impair Daphnia mobility. Highest concentrations of dissolved metal ions only matched the declared main components of the respective shots in 3 out of 9 cases. These results demonstrate that metal release from alternative game shot is an underestimated ecotoxicological risk, particularly since release of copper and zinc from alternative shots was demonstrated to be more hazardous for aquatic biota than conventional lead shot. There is an urgent need of managing the use of shot ammunition near waterbodies based on realistic ecotoxicological risk assessments.