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. In the present work, we demonstrate that bees can not only be used to detect large particulate matter emitters, such as mines or industrial plants, but also small aerosol sources such as shooting ranges. During a background monitoring of particle matter pollution, worker bees were collected from hives located in the rural part 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 bees from one beehive had very exotic particles, which turned out to be typical of gunshot residues. Indeed, a shooting range was in the roaming territory of the corresponding beehive. Bees, therefore, could be an ideal tool not only for monitoring significant aerosol sources, but also small ones.