Effects of a human food additive, titanium dioxide nanoparticles E171, on Drosophila melanogaster – a 20 generation dietary exposure experiment

Abstract

Although a recent human safety reevaluation of food grade E171 TiO2 was performed by a European Food Safety Authority, not many new data were considered and a major lack of multigenerational studies with reproductive endpoints was noted. In this study, we exposed fruit flies to an estimated daily human E171 consumption concentration for 20 generations. Dietary exposure of 20 consecutive generations of D. melanogaster to E171 resulted in a change in normal developmental and reproductive dynamics, reduced fecundity after repetitive breeding, increased genotoxicity, and the appearance of aberrant phenotypes. This effect can be seen as one of the classical adaptations of the fruit fly population to a stressor. A pattern that was gradually observed over the 20 generations of flies was shorter developmental time coupled with higher fecundity and egg to adult viability in virgin females, but reduced fecundity at subsequent mating events Marks of adaptive evolution and directional selection were also exhibited. The larval stages were at a higher risk of sustaining damage from E171 as they had a slower elimination rate and therefore accumulated 10 times the quantity of TiO2 compared to adults. This is particularly worrisome, since among the human population, children tend to consume higher daily concentrations of E171 than adults do. The genotoxic effect of E171 was statistically significantly higher in each subsequent generation compared to the previous one. Aberrant phenotypes were likely caused by developmental defects induced by E171 since the phenotypic features were not transferred to any progeny even after 5 generations of consecutive crossbreeding. Therefore, exposure to E171 during early developmental period carries a higher risk of toxicity, and again, in the human population, fetuses and young children would be the most endangered cohort. The fact that the daily human consumption concentration of E171 is able to interfere with and influence fruit fly physiological, ontogenetic, genotoxic, and adaptive processes certainly raises safety concerns.