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, ... nanoparticles are showing up in everything from fabric coatings to socks to plush teddy bears. 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. 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. 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. 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.