Surface spray called free of nanoparticles

Germany's Federal Institute for Risk Assessment (BfR) has determined that nanoparticles did not cause respiratory problems in more than 100 German consumers who used Magic Nano surface-sealing sprays (C&EN, April 17, page 10). Cleaning-product maker Kleinmann GmbH pulled the sprays from the market in late March when health issues arose. On the basis of information from the manufacturer and its suppliers, along with separate tests that BfR says it commissioned, the sprays were found not to contain any particles of less than 100 nm in size or even the silane active ingredient. The aerosol sprays are intended to form a nanoscale silicon dioxide film on glass and ceramic surfaces to render them dirt- and water-repellant. Ralf Jürgens, a scientist at nanomaterial supplier Nanopool, tells C&EN that the pH of the solution was improperly adjusted during formulation. This caused the silicon-based material to fall out of solution, leaving only solvent in the product. BfR is still investigating whether other components of the spray were to blame.