Vehicle-derived ultrafine particulate contaminating bees and bee products

Despite adverse health effects, ultrafine particulate matter (UFP), i.e., PM less than 0.1 μm in diameter, is an emerging pollutant not subject to regulation. UFP may cause both lung inflammation and cardiopulmonary disease and may enter the brain directly via the olfactory bulb, affecting the nervous system. In highly urbanized environments, diesel and gasoline vehicles are among the major sources of UFP including combustion-generated solid particle pollutant and metal-based particles. Metal-based UFP are of much concern, as they may promote inflammation and DNA damage via oxidative stress with generation of free radicals and reactive oxygen species (ROS). We used the honeybee as an alternative sampling system of UFP in an area of the Po Valley (Northern Italy), which is subject to intense traffic. Worker bees are widely recognised as efficient samplers of air pollutants, including airborne PM. During flight and foraging activity, pubescence of the bees promotes the accumulation of electrical charge on the body's surface, enhancing attraction to air pollutants. Bees living near the main Italian highway, the Autostrada A1, displayed a contamination of nanosized Fe-oxides/hydroxides and baryte. Sources of Fe-bearing and baryte ultrafine particles are primarily the vehicles speeding on the motorway. Pollen collected by forager bees and honey produced by the bee colony displayed contamination by nanosized Fe-oxides/hydroxides and baryte. Such a contamination exposes pollinators and humans to UFP ingestion, endangering the safety of food produced at traffic-influenced sites. Given the global spread of traffic, our findings suggest that exposure and environmental impact of ultrafine Fe-oxides/hydroxides and baryte are potentially ubiquitous, although usually overlooked in environmental policy discussions.