'Magical' nanoparticles scrutinized for health effects

SAN FRANCISCO -- Windows cleaned by raindrops, white sofas immune to red wine spills, tiles protected from limescale buildup -- new products created from minute substances called nanoparticles are making such domestic dreams come true.

Based on tiny particles 10,000 times thinner than a strand of hair, the products are some of the early widespread applications of nanotechnology, the science of manipulating atoms and molecules. Nanoparticles are showing up in everything from fabric coatings to socks to plush teddy bears.

In the best-case scenario, these nanoparticles are harmless and can help spare the environment from the overuse of polluting cleaning agents.

But some scientists are concerned that these seemingly magical materials are hitting the market before their effects on human health and the environment have been sufficiently studied.

If a chemical substance has been commercialized before, on a larger than nano-scale, and is included in the Toxic Substances Control Act Chemical Substance Inventory, it is considered as "existing" by the U.S. Environmental Protection Agency -- and the nano-scale version of the material requires no further testing.

Scientists such as Jennifer Sass of the Natural Resources Defense Council say they think that's a mistake, and that nanoparticles should be treated as new and different materials.

That's because the few scientific reports available suggest that nanoparticles can pose a threat to human health and to the environment. For example, fish swimming in water containing modest amounts of fullerenes -- soccer-ball-shaped nanoparticles made out of 60 carbon atoms -- showed a large increase in brain damage. These are the same types of fullerenes being used in various skin products.

Another study showed that rats exposed to manganese oxide nanoparticles accumulated them in the brain.

Scientists also have shown that very small nanoparticles, called quantum dots, penetrate pigskin. Other studies suggest that from the skin, they can travel through the lymphatic duct system to lymph nodes and eventually end up in organs such as the liver, kidney and spleen.

And when inhaled, nanoparticles will go deeper into the lungs than larger particles and reach more sensitive parts. Because of that, scientists are particularly concerned about nanoparticles being used in spray products.

"We have research showing that as a material shrinks in size, it becomes more harmful to the lungs. Nanoparticles tend to be more inflammatory to the lung, and it seems as if the lung has to work harder to get rid of them," said Andrew Maynard, chief science adviser at the Project on Emerging Nanotechnologies in Washington.

The project was established in 2005 by the Woodrow Wilson International Center for Scholars and the Pew Charitable Trusts to ensure that the potential benefits of nanotechnology are realized, at the same time possible risks are minimized.

"We can do great things with this technology, but there is a lack of information on how to use nanoparticles safely," he said.

To get a better picture of what kind of nanomaterials are being commercialized, the EPA in January started a voluntary reporting program, the Nanoscale Materials Stewardship Program. Two companies have so far submitted data, DuPont and Office ZPI, while 10 other companies have committed to reporting.

Researchers are concerned not only with human health, but the effect nanoparticles could have on the environment, especially silver nanoparticles.

Maynard said the antimicrobial effect specific to silver nanoparticles is dangerous to microbes essential for ecologic systems.

In April, scientists at the annual meeting of the American Chemical Society in New Orleans tested six different types of socks, all containing silver nanoparticles to minimize odor. Some of the socks released all of the silver nanoparticles they contained when washed in room-temperature water; others leaked no silver at all.

Sewage treatment works cannot clear the water of the substance, so released silver nanoparticles will end up in rivers, lakes and in seawater.

Samuel Luoma, senior research hydrologist with the U.S. Geological Survey, is studying how the increasing use of silver nanoparticles can affect the environment.

"We know silver itself is very toxic to plants in the aquatic environment and to invertebrates like clams, oysters and snails," Luoma said. "Silver is especially toxic to phytoplankton, the base of many food webs."

Like "normal" silver, nano-size silver will continuously release silver ions, causing adverse effects to water-living organisms. But it's possible the nanoparticles are additionally toxic due to the small size.

It also is unknown how nanosilver affects humans. Normally, silver accumulates in various organs, but do no harm.

"Right now, there is an explosion of these products, but we cannot assess the risk in a rational way," Luoma said. "The simplest thing the government could do is to require information on how much silver is used in each product."

The EPA considers certain use of silver nanoparticles a pesticide, and they therefore need to be registered according to the Federal Insecticide, Fungicide, and Rodenticide Act. But so far, the agency has received no such applications.

Despite the alarming reports, scientists said that silver nanoparticles can be quite useful.

They do a great job in hospitals, killing bacteria resistant to conventional antibiotics. And coating artificial hips and shoulders with silver nanoparticles can hinder bacteria from accumulating and causing infection years after implantation.

"The bottom line here is that we need $100 million to $150 million per year invested in targeted risk research if we are to have a hope of answering some of the critical questions surrounding developing and using nanotechnologies safely," Maynard said.

Reach San Francisco Chronicle writer Ann Fernholm at afernholm(at)sfchronicle.com

(Distributed by Scripps Howard News Service, www.scrippsnews.com.)