THE BENEFITS (AND RISKS?) OF NANOTECHNOLOGY: Nanotechnolology offers great promise in medicine and many other fields but does it also pose hazards?
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It seems like a noble goal: amid growing concern about the health risks of nanoparticles, why not keep tabs on the health of people who work with the little buggers? But it turns out that's easier said than done.

"You could probably count the world's published literature on exposure to nanoparticles on both hands," says Paul Schulte, director of the Education and Information Division of the National Institute for Occupational Safety and Health (NIOSH). "And yet a lot of words have been written about nanotechnology, and it leads one to want to take action. We're struggling with finding a scientific basis on which to do that."

Unfortunately, he says, a NIOSH draft proposal—titled "Interim Guidance on Medical Screening of Workers Potentially Exposed to Engineered Nanoparticles''—is limited in the guidance it can provide. The reason: too little information. Scientists have only the broadest suspicions about harm that nanoparticles may cause. How, then, to recommend which workers should be screened and exactly what they should be tested for?

"In essence, you're going on a fishing expedition," says Andrew Maynard, a former NIOSH researcher who is now chief science adviser at the nonprofit Project on Emerging Nanotechnologies, part of the Woodrow Wilson International Center for Scholars in Washington, D.C. "We need to make this link to disease, but you can't just do that by randomly testing people."

NIOSH scientists are not the only ones scratching their heads over the possible dangers of nanotech. It is one of the world's hottest technologies, and experts agree that it poses unpredictable, potentially serious health risks. Beyond that, not much is known.

Nanotechnology involves the manipulation of teeny particles, measuring between one and 100 nanometers. (A nanometer is one billionth of a meter, or roughly 80,000 times smaller than the width of a human hair.) At that size, substances shed some of their usual rules of behavior, which is both the magic and the menace of nanotech.

Physically, nanoparticles are so minute that they can penetrate deep into the body. Animal studies have found, for example, that some can cross the blood–brain barrier, which normally protects the brain from toxins in the bloodstream. That may be great if you are using carbon nanotubes to deliver chemotherapy drugs to people with brain tumors, as cancer researchers in California (at City of Hope, a cancer research and treatment center in Duarte in collaboration with NASA's Jet Propulsion Laboratory in Pasadena), hope to do. It may not be so awesome if the particles enter the bloodstream by accident rather than as part of a medical treatment.

Some of the worry about exposure to engineered nanoparticles arises from their unintended counterparts, often found in air pollution. The puniest bits of soot in diesel exhaust, known as ultrafines, measure on the nanoscale. When inhaled, they journey into the smallest air passages in the lungs, which are off-limits to larger particles. There they cause respiratory problems and, more surprisingly, heart disease, according to University of Rochester researcher Günter Oberdörster and others.

Chemically, nanoparticles tend to be more reactive than larger amounts of the same substance, because they have more surface area and therefore more opportunity to interact with other substances. That means a chemical that's normally harmless might be toxic in minuscule doses. Animal studies show that inhaled nanoparticles can cause pulmonary inflammation, move from the lungs to other organs, and interfere with cell signaling. Shrink something to nanosize and it can do surprising things: change color, become soluble, conduct electricity.

At the same time, the potential benefits are enormous. Medical researchers hold out hope for "nanomiracles" ranging from drugs that fight radiation poisoning to a shoebox-size portable genetics testing lab. Current and potential green applications abound: window coatings that block heat but not light, more efficient solar panels, energy-saving traffic lights. Researchers at Lehigh University in Bethlehem, Pa., say that because of their size and reactivity, iron nanoparticles can decontaminate solvent-soaked soil up to 1,000 times faster than a conventional iron mixture.