Measurement of the Physical Properties of Aerosols in a Fullerene Factory for Inhalation Exposure Assessment

Abstract

Assessment of human exposure is important for the elucidation of potential health risks. However, there is little information available on particle number concentrations and number size distributions, including those of nanoparticles, in the working environments of factories producing engineered nanomaterials. The authors used a scanning mobility particle sizer and an optical particle counter to measure the particle number size distributions of particles ranging in diameter (D _p ) from 10 nm to >5000 nm in a fullerene factory and used scanning electron microscopy to examine the morphology of the particles. Comparisons of particle size distributions and morphology during non-work periods, during work periods, during an agitation process, and in the nearby outdoor air were conducted to identify the sources of the particles and to determine their physical properties. A modal diameter of 25 nm was found in the working area during the non-work period; this result was probably influenced by ingress of outdoor air. During the removal of fullerenes from a storage tank for bagging and/or weighing, the particle number concentration at D _p <50 nm was no greater than that in the non-work period, but the concentration at D _p >1000 nm was greater during the non-work period. When a vacuum cleaner was in use, the particle number concentration at D _p <50 nm was greater than that during the non-work period, but the concentration at D _p >1000 nm was no greater. Scanning electron microscopy revealed that the coarse particles emitted during bagging and/or weighing were aggregates/agglomerates of fullerenes; although origin of particles with D _p <50 nm is unclear.

Keywords:

• engineered nanomaterials
• morphology
• size distribution
• nanoparticle
• ultrafine particle

ACKNOWLEDGMENTS

This study was funded by Special Coordination Funds for Promoting Science and Technology as part of a research project on the facilitation of public acceptance of nanotechnology. The authors wish to thank the workers who participated in the study. The authors are grateful to S.Takano for her assistance in this work.

Notes

^A The bagging operation includes removal of fullerene from the storage tank, weighing, and use of the vacuum cleaner to facilitate the bagging operation.

^B Note that agitation was not a normal procedure.

*Currently at the Research Center for Environmental Risk, National Institute for Environmental Studies;

**Currently at the Center for Innovation Systems Research, Integrated Research Institute, Tokyo Institute of Technology, Yokohama.