Heavy metal pollution from a shooting range revealed by honeybees

Honey bees (Apis mellifera L.) have been established as environmental monitors to assess the aerosol contamination of the environment in the vicinity of beehives. During their wide-ranging foraging trips, these hymenopterans catch particles in flight and while collecting nectar, pollen, or water. This study demonstrates that honeybees can be employed not only to detect major particulate matter emitters, such as mines or industrial plants, but also smaller, localized aerosol sources, such as shooting ranges. During background monitoring of particulate matter pollution, worker bees were collected from hives in rural areas of the canton and the city of Fribourg (Switzerland). The head, wings, and hind legs of the bees were investigated with Scanning Electron Microscopy coupled with X-ray spectroscopy (SEM-EDX). The analyzed particles reflect the vigorous dairy farming activity in the region (home of Gruyère cheese-making), but particles from one beehive were very exotic and typical of gunshot residues. Indeed, a shooting range was within the foraging range of the corresponding beehive. Bees, therefore, could be an ideal tool not only for monitoring significant aerosol sources but also for monitoring small ones.