Adult exposure, however, can lead to extensive adhesion of the fine particles , and even to whole body coverage, impaired climbing ability, and early death. This scenario occurs when the adult flies are contacted directly with the nanomaterials as dry powders.
The adhesion effects are related to nanoparticle aggregation state – large aggregate adhere only weakly to fly surfaces and can be removed by natural grooming mechanisms (see top image), whereas finer aggregates overwhelm these mechanisms and dramatically alter the exterior appearance and function of the fly (middle image shows unexposed fly foot (left) and foot coated with fine aggregates of multi-walled carbon nanotubes that impair climbing ability.
In contrast, the larval phase can be raised on a gelatinous food paste that is doped with up to 1000 ppm of carbon nanotubes, C60 fullerene, or carbon black with no detectable effect on egg to adult survivorship. This occurs despite evidence that the nanomaterials are taken up and become sequestered in tissue (see bottom image). The ability larval flies to take up and store nanoparticles in their tissues through the adult stage opens the possibility that nanoparticles may bioaccumulate to higher trophic levels by insect predation, though this has not yet been established. The ability of nanoparticles to adhere to adult fly surfaces, and the ability of those adults to remove the nanoparticles by grooming leads to the possibility of fly-born nanoparticle transport, in analogy to bee pollination or bacterial transport by insects as disease vectors.