Well. It is a big debate and you can compare with irradiation debate. Still it is not established whether nanoparticle has effect on human body. EU is proactive against use of NP. We have to wait few years for the answer.
There are many research papers and medical evidences predict that nanoparticle has problem with inhalation and coronoray diseases. Regulation of nanotechnology is available from this paper published this year.
The Case for Regulating Nanotechnologies:
International, European and National Perspectives
Sekai Ngarize, Karen E. Makuch and Ricardo Pereira