It was just the type of event that many in the nanotechnology community have feared -- and warned against. In late March, six people went to the hospital with serious (but nonfatal) respiratory problems after using a German household cleaning product called Magic Nano. Though it was unclear at the time what had caused the illnesses -- and even whether the aerosol cleaner contained any nanoparticles -- the events reignited the debate over the safety of consumer products that use nanotechnology.

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