Predicting atmospheric cadmium and lead using honeybees as atmospheric heavy metals pollution indicators. Results of a monitoring survey in Northern Italy

This study assessed the ability of honeybees as environmental indicators for atmospheric Lead and Cadmium concentrations through regression analyses. For this purpose, honeybees sampling was performed from June to November 2017, in three apiaries in Milano, and in two apiaries in Lodi and in Magenta. Heavy metals were detected on bees through atomic absorption and related to the respective mean atmospheric levels, measured by municipal monitoring units during 30 d before bees collection. The highest values of Cadmium on bees, 0.028–0.385 µg g−1, were detected in Magenta, a suburban-rural site. Lead showed the highest values, 0.244–0.741 µg g−1, in Milano, Orti di Via Padova, an urban ex-industrial area retrained for horticulture, characterised by a planted area rich in biodiversity. Cd and Pb on bees were significantly (p <.001) affected by the respective atmospheric heavy metal concentration, measured by the nearest municipal monitoring station (p <.05) and affected by beehive site type (p <.05). The linear regression models performed for each site, showed that atmospheric metals were significantly better predicted in biodiverse sites than in sites characterised by poor vegetal biodiversity, probably for the necessity of bees of a larger foraging area. This study highlighted the relationship between bee and atmospheric quality of the hive site, confirming and quantifying the ability of bees as “alternative tools” to atmospheric monitoring devices for Cadmium and Lead pollution level. For the local-regional aspect of the study, further studies at larger scale are needed.