Hazard assessments of manufactured nanomaterials.

BACKGROUND It has been difficult to make reliable hazard assessments of manufactured nanomaterials, because the nanomaterials form large agglomerations in both in vitro and in vivo studies. OBJECTIVE In the New Energy and Industrial Technology Development Organization (NEDO) Project of Japan, the physicochemical properties of many manufactured nanomaterials are being measured, and in vitro and in vivo studies are being performed to determine which endpoints are correspond to the hazards and risks of nanomaterials. Focusing on titanium dioxide, fullerenes and carbon nanotubes, we introduce findings made in inhalation and intratracheal installation studies overseas, and together with the findings made in the NEDO project, and also assess the hazards presented by manufactured nanomaterials. RESULTS AND CONCLUSION A project by NEDO has succeeded in ensuring the stability of dispersion (nanoscale <100 nm) of manufactured nanomaterials, and is developing hazard assessments of manufactured nanomaterials. In these interim reports, the acceptable exposure concentration of titanium dioxide and fullerene was proposed to be 1.2 mg/m(3) and 0.8 mg/m(3) respirable dust in working environment, respectively.