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Carbon 'footballs' harm fish
03 April 2004
From New Scientist Print Edition.
Bob Holmes

Buckyballs, the synthetic carbon molecules that show such promise in nanotechnology, can cause brain damage in fish and kill other aquatic animals. Although the results are preliminary, the suggestion is that nanomaterials could cause harm if released into the environment.

Industry is just beginning to exploit the potential of football-shaped buckyballs - fullerenes - and their chemical kin, cylindrical carbon nanotubes. Although only a handful of factories worldwide produce such molecules, it is envisaged that they will be widely used in areas as diverse as drug delivery, cosmetics, high-tech fibres and as oxidising agents for environmental remediation. "We believe nanomaterials are going to be made in large quantities, so we need to understand their environmental and toxicological effects," says Kirsten Kulinowski, executive director of the Center for Biological and Environmental Nanotechnology at Rice University in Houston, Texas.

To address that question, environmental toxicologist Eva Oberdörster of Southern Methodist University in Dallas used two toxicological tests to measure the effect of waterborne fullerenes on aquatic animals. In the first, she grew daphnia, or water fleas, for three weeks in water containing fullerene concentrations ranging from 5 to 2000 parts per billion. A concentration of 800 ppb was enough to kill half the animals. "That makes this moderately toxic. It's not extremely toxic, but it's not innocuous, either," says Oberdörster, who reported her results this week at a meeting of the American Chemical Society in Anaheim, California.

In a second controlled test using nine juvenile largemouth bass, Oberdörster found that a concentration of 500 ppb led to a 17-fold increase in cellular damage in brain tissue, although it did not kill the fish outright. The type of damage caused, known as lipid peroxidation, can impair the workings of cell membranes and has been linked to Alzheimer's disease in people.

Oberdörster did not find lipid peroxidation in liver or gill tissues, but she did find inflammatory changes in the liver and activation of genes coding for repair enzymes, suggesting that some injury was occurring. More extensive studies with larger samples may help pin down these effects, she says.

Oberdörster's study is not the first to reveal toxic effects of fullerenes or nanotubes. Last year, researchers found that nanotubes can damage the lungs of mice if inhaled (New Scientist, 29 March 2003, p 14) and buckyballs have been shown to kill cells in lab experiments. However, no previous study has looked at what might happen if such materials escaped to the environment.

Nanomaterials are not widely used at present, so no one knows yet what levels of environmental exposure are likely, and whether fish would be exposed to levels like those in Oberdörster's experiments.

Still, as fullerenes move into large-scale production, the fear is that accidental spills will inevitably occur. "It's not 'if' it's going to happen, it's where and when," says Oberdörster. And some potential uses, such as in structural materials and in cosmetics and sunscreens, will almost certainly mean fullerenes find their way into the environment.

The uncertainty about the health and environmental effects of nanomaterials has led a few environmental groups - most notably the ETC group, based in Winnipeg, Canada - to call for a moratorium on their use and development.

Oberdörster, however, sounds a gentler caution. "Fullerenes have some really positive potential. But alongside the development of these technologies, we do need to look at the toxicity."

From issue 2441 of New Scientist magazine, 03 April 2004, page 11

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