Heavy metals on honeybees indicate their concentration in the atmosphere : a proof of concept

The aim of this research was to evaluate as a proof of concept, a quantitative relationship between atmospheric particulate matter (PM10), atmospheric heavy metals (Pb, Ni and Cd) and Pb, Ni and Cd concentrations accumulated on bees reared in a beehive in the urban territory in Milan. For this purpose, a beehive called the Honey Factory, located in the Triennale museum area in Milano, was considered in the trial from May to October 2015. Every two days, bees found dead in the beehive were collected and the concentration of lead, cadmium and nickel on the bees bodies were evaluated through atomic absorption analysis. In the same period, data about atmospheric dust, Lead, Cadmium and Nickel, were daily downloaded by the ARPA website. The comparison between atmospheric and animal data has revealed a tight relation. Linear regressions for animals and atmosphere were calculated: when the concentration of atmospheric lead exceeded the value of 4 ng/m3, bees ‘carried’ about 0.7 mg/kg of lead. When the lead atmospheric concentration was higher than 15 ng/m3, lead on the bee’s body was more than 0.9 mg/kg (y = 0.1006x + 0.573, R2 = 0.98). A similar relationship was detected for Nickel. This study showed that heavy metals accumulated on honeybees depend on the atmospheric concentrations measured during the month before animal sampling and that PM10 pollution level seems to contribute to Pb and Ni levels detected on the animals.Highlights Bees are environmental quality indicators. Pb, Ni, Cd (HM) were detected on bees and in the air. HM on bees depend on the atmospheric concentration.