Cerium( iv ) oxide nanoparticles induce sublethal changes in honeybees after chronic exposure

The high annual production and use of cerium( iv ) oxide nanoparticles (nCeO 2 s) may lead to their atmospheric release and substantial deposition on plants. This poses a potential threat to pollinators. We investigated the effects of nCeO 2 -spiked food (2–500 mg L −1 ) on summer and winter honeybees ( Apis mellifera carnica ) after chronic 9 days' oral exposure. Acetylcholinesterase (AChE) and glutathione S -transferase (GST) activities were measured in different body compartments (heads, thoraces, and haemolymph). The activity of AChE was assessed in salt-soluble (SS) (containing soluble and membrane AChE) and detergent-soluble (DS) (predominantly membrane-bound AChE) fractions. Exposure of honeybees to nCeO 2 -spiked food had no significant effects on survival up to 500 mg L −1 (