"There are many potential benefits of nanotechnology, but its hazards and risks are poorly understood. This study gives us additional cause for concern," says study leader Eva Oberdörster, Ph.D., an environmental toxicologist with Southern Methodist University in Dallas.
Buckyballs are pure carbon structures shaped like soccer balls that differ from other forms of pure carbon, like diamond and graphite, in the way their atoms are bonded. The structures, also known as fullerenes, are thousands of times smaller than the width of a human hair.
Experts predict the widespread use of these and other nanoparticles in the future. Buckyballs show promise as components of fuel cells, drug delivery systems and cosmetics that delay aging. Although promising, their health risk is unknown.
In a controlled laboratory study, the researcher exposed nine juvenile largemouth bass — confined to 10-Liter aquaria — to a form of water-soluble buckyball (C60) at a dose of 0.5 parts per million.
After 48 hours, the animals developed significant brain damage as measured by lipid peroxidation, or the breakdown of lipids, as shown by laboratory analysis of brain tissue samples. The brain damage seen in the fish exposed to the nanoparticles was severe: 17 times higher than that seen in nine unexposed animals, the researcher says.
"Given the rapid onset of brain damage, it is important to further test and assess the risks and benefits of this new technology before use becomes even more widespread," says Oberdörster. Until further studies are done, no one knows yet whether these and other buckyballs will cause similar brain damage in humans, she emphasizes.
To date, there have been no human studies of the health effect of buckyballs or other manufactured nanoparticles, the researcher says. A few animal studies have shown that nano-sized particles are capable of moving into the brain after being inhaled, but the current study is believed to be the first to show that the particles can actually cause damage to the brain, Oberdörster says.
In addition to damage to the brain, the researcher also investigated altered gene expression in the liver of exposed fish. "We found a variety of genes that were turned on or turned off, indicating a whole-body response to fullerene exposure," she says, adding that these studies represent the first steps in a longer process of studying changes in gene expression.
In particular, Oberdörster found chemical markers in the liver of the exposed fish that indicated the onset of inflammation, a process that has been implicated in an increasing number of diseases.
The researchers still do not know the mechanism by which buckyballs cause damage in the fish. "We don't know if the fullerenes are directly causing lipid peroxidation in the brain tissue or whether it is a secondary effect caused by inflammation," Oberdörster says.
The researcher is planning additional studies in the future to determine the mechanisms of action and to find out how many buckyballs get into the fish's body and where the particles are distributed. She expressed concern that nanoparticles could begin to accumulate throughout the food chain, affecting not just fish, but other animals, plants and possible people.
Researchers worldwide are just beginning to test manufactured nanoparticles for signs of possible toxicity, but it may be years before any reliable human data are available, Oberdörster stresses. As several companies are beginning to manufacture engineered fullerenes, an initial concern is workplace exposure to the particles, she says. People are not currently exposed to engineered fullerenes in consumer products, but their use is expected to increase in the future. This study suggests that an evaluation of human exposure levels should be completed before these particles are widely used in consumer products, the researcher says.
The paper on this research, IEC 21, will be presented at 1:40 p.m. on Sunday, March 28, at the Anaheim Marriott, Grand Ballroom F, during the "Nanotechnology and the Environment" symposium.
Eva Oberdörster, Ph.D., is currently a lecturer in the Department of Biology at Southern Methodist University in Dallas. She is also an adjunct assistant research scientist at Duke University in Durham, N.C.
— Mark T. Sampson