Fullerene c60: inhalation hazard assessment and derivation of a period-limited acceptable exposure level.

Fullerene C-60 has great potential for use in many industry and medical nanotechnology applications. Although the use of nanomaterials has been increasing in the recent years, limited information about its potential hazardous effects is available. Therefore, safety of nanomaterials is a world concern. Before health effects arise in workers and the general population, development and use under appropriate management are desirable. Therefore, we aimed to determine an acceptable exposure level for humans by reviewing the limited animal toxicity data available. Here, we present an initial hazard assessment, including a review of the available toxicity information of the effects of C-60 on the lungs. We then estimated the no-observed-adverse-effect level (NOAEL) of C-60 on rat lung toxicity by using lung retention of C-60 in inhalation exposure and intratracheal instillation tests. The NOAEL of C-60 on rat lung toxicity was estimated to be 3.1 mg/m(3). Because this is the NOAEL for subchronic toxicity, a period-limited acceptable exposure level (AEL(PL)) for humans was proposed, which assumed 15 years of exposure and modification within the next 10 years since more knowledge will be gained in the future. The AEL(PL) of C-60 particles with a geometric mean of 96 nm and a geometric standard deviation (GSD) of 2.0 was estimated to be 0.39 mg/m(3) for healthy workers and 1.4 x 10(-2) mg/m(3) for the general human population. The AEL(PL) of C-60 particles with different sizes was estimated to be 0.39x0.0913/f(work,d=x,GSD=y) mg/m(3) for healthy workers and 0.014x 0.107/f(env,d=x,GSD=y) mg/m(3) for the general human population.