Nanomaterial health effects part 3: conclusion--hazardous issues and the precautionary principle.

This is the third and final paper in a series about nanomaterials and their potential health effects. There has been an incident of apparent respiratory health effects in Germany in consumers using a "nano" cleaning product. Other recently proposed consumer products seem to carry potential health and/or ecological hazards. In light of rapidly evolving nanotechnology the "precautionary principle" in environmental health science is reviewed. Hopefully a balance can be reached that allows the realization of societal benefits from the development and implementation of nanotechnology while preventing its unquestioned use in ways that damage ecology and human health.