Acute and chronic effects of Titanium dioxide (TiO2) PM1 on honey bee gut microbiota under laboratory conditions

Apis mellifera is an important provider of ecosystem services, and during fight and foraging behaviouris exposed to environmental pollutants including airborne particulate matter (PM). While exposureto insecticides, antibiotics, and herbicides may compromise bee health through alterations of thegut microbial community, no data are available on the impacts of PM on the bee microbiota. Here wetested the efects of ultrapure Titanium dioxide (TiO2) submicrometric PM (i.e., PM1, less than 1 µmin diameter) on the gut microbiota of adult bees. TiO2 PM1 is widely used as a fller and whiteningagent in a range of manufactured objects, and ultrapure TiO2 PM1 is also a common food additive,even if it has been classifed by the International Agency for Research on Cancer (IARC) as a possiblehuman carcinogen in Group 2B. Due to its ubiquitous use, honey bees may be severely exposed to TiO2ingestion through contaminated honey and pollen. Here, we demonstrated that acute and chronicoral administration of ultrapure TiO2 PM1 to adult bees alters the bee microbial community; therefore,airborne PM may represent a further risk factor for the honey bee health, promoting sublethal efectsagainst the gut microbiota