Environmental Factor, September 2009, National Institute of Environmental Health Sciences
Superfund Study of Carbon Nanoparticle Toxicity in Adult Flies
By Rebecca Wilson
Researchers at Brown University's NIEHS-funded Superfund Research Program (Brown SRP) report in the latest edition of Environmental Science and Technology that carbon nanoparticles cause a significantly higher mortality rate in adult fruit flies than in very young flies. This finding was observed in a series of experiments conducted on larval and adult Drosophila fruit flies using several types of carbon nanoparticles commonly found in medicine, electronics and office settings.
According to the authors, the findings (http://pubs.acs.org/doi/abs/10.1021/es901079z?prevSearch=[author%3A%2BRand]&searchHistoryKey=) are important because they show that permutations of the same material can have different effects in the environment. "It's not the nanoparticle per se that may be hazardous," said corresponding author David Rand, Ph.D., (http://www.brown.edu/Departments/EEB/rand/) "but the form the particle is in."
In the experiments, Rand, Robert Hurt, Ph.D., (http://research.brown.edu/myresearch/Robert_Hurt) and other Brown SRP researchers exposed Drosophila larvae to one of four types of carbon nanoparticles, carefully blending it into their food so the larvae could not detect it or choose to avoid eating it. The larvae seemed to have no physical or reproductive effects from consuming the nanoparticles, though some of the nanoparticles appeared to be incorporated in the larvae, where they remained through maturation and showed in adult tissue. This could indicate that, with the proper conditions, bioaccumulation to larger animals might occur in nature.
The adult flies weren't so lucky. They were sealed into a test tube that contained a dry sample of the particles, and the test tube was taped, causing the flies to fall into the powdery particles. At that point, the investigators used a timer to determine how long it took the exposed flies to climb back to the top of the test tube. Flies exposed to carbon black and single-walled nanotubes were engulfed in the fine dust and, unable to remove it, died within a few hours. Other materials did not cover the flies so thoroughly, and they were able to remove the particles through normal grooming mechanisms.
Though the exact mechanism of toxicity is unclear, analysis by lead author Xinyuan Liu, a Ph.D. student in chemistry at Brown funded by the SRP, revealed several possibilities. Some flies were covered in dust from head to toe, including their wings, which could have impeded their movement. Still others might have been blinded by the particles covering their eyes or suffocated from particles clogging their spiracles, or breathing holes. "It's like a dinosaur falling into a tar pit," commented Rand. "[The particles] glom onto the flies. They just can't move."
A related experiment was conducted concurrently with those published in Environmental Science & Technology. In this experiment, led by undergraduate student Daniel Vinson, adult Drosophila were covered in nanoparticles and then allowed to walk from one test tube to another, depositing particles along the way. The transport caused clean, control flies to be contaminated with some of the nanoparticles. This experiment demonstrated how insects could be vectors for transporting nanomaterials and other materials, such as bacteria or intestinal parasites.
Citation: Liu X, Vinson D, Abt D, Hurt RH, Rand DM. (http://pubs.acs.org/doi/abs/10.1021/es901079z?prevSearch=[author%3A%2BRand]&searchHistoryKey=) 2009. Differential Toxicity of Carbon Nanomaterials in Drosophila: Larval Dietary Uptake Is Benign, but Adult Exposure Causes Locomotor Impairment and Mortality. Environ Sci Technol 43(16):6357-6363. Epub ahead of print. DOI: 10.1021/es901079z
(Rebecca Wilson is an environmental health information specialist for MDB, Inc., a contractor for the NIEHS Superfund Research Program and Worker Education and Training Program.)