Nano Pollution, smallest of dangers


The potential impact of nanoparticles on marine life concerns Southern Methodist University toxicologist Eva Oberdörster, who recently completed a study involving captive large-mouth bass. The tiny particles may be small enough to lodge inside their brain tissue.

In 1941, researchers at Johns Hopkins Hospital made an unsettling discovery: Inhaled nanoscopic particles could travel into the brain. When chimps and rhesus monkeys breathed air laden with poliovirus cells, some of the particles followed the path normally reserved for smell signals, thwarting the protective blood-brain barrier.

Polio has since been contained, but lifeless specks the same size or smaller will be churned out by the ton in coming years as nanotechnology becomes an industrial mainstay. Though the nano boom will likely yield countless commercial benefits-ultraprecise drug delivery systems, improved superconductors-it could also give way to an insidious form of air pollution. Mass production will likely bring environmental exposure, and experts are now examining the potential for toxic nanoparticles (objects typically smaller than one billionth of a meter) to end up inside plants, animals or people.

The potential impact of nanoparticles on marine life concerns Southern Methodist University toxicologist Eva Oberdörster, who recently completed a study involving captive large-mouth bass. Oberdörster exposed the fish to various concentrations of a dome-shaped molecule called Carbon-60. After two days, signs of an immune response to the invaders were found inside the fishes' livers. Evidence suggests the molecules may have even breached the cells protecting the brain and central nervous system.

Carbon-60 is part of a family of precision-engineered nanoparticles called fullerenes, named after architect R. Buckminster Fuller, famous for his geodesic domes. The structure of the molecules and their resistance to heat, among other properties, make them suitable for use in fuel cells, high-temperature lubricants and other products that could wind up in landfills, says nanochemist Vicki Colvin, director of the Center for Biological and Environmental Nanotechnology at Rice University, where fullerenes were first discovered.

But not all fullerenes are toxic, Colvin points out. The type used in the fish study lacked the protective coating often applied to fullerenes to render them nontoxic to living tissue. "Fullerenes have extremely stable surface coatings," she says. More than merely shellacking the sphere, the coating process chemically bonds the surface material to the carbon. Colvin adds that fullerene pollution will likely pale next to the nanoscopic airborne pollution already in existence, from the carbon particles in car exhaust to the manganese oxide in welding fumes. "We're exposed to multi-ton quantities of incidentally created nanoparticles," Colvin says.

Oberdörster's father, Günter Oberdörster, director of the University of Rochester's EPA-funded Particulate Matter Center, has probed the toxicity of those inadvertent particles for years. His most recent research project shows that rats, like monkeys, may be subject to contamination by inhaled ultrafine particles via the olfactory tract, a pathway also found in humans.

Günter Oberdörster cautions against alarm, too: Nanoparticle toxicity is not a given. "Surface chemistry is very important," he says. "Most of the engineered nanoparticles may be harmless. Of course, we don't know that. We need to find out."

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