Assessing Exposures to Nanomaterials in the Occupational Environment

This chapter focuses on assessment of exposures to nanomaterials in the occupational environment. Exposure routes for nanomaterials include inhalation, dermal, and ingestion. There is uncertainty regarding the appropriate metric by which intensity should be measured for inhalation and dermal exposures. Mass concentration has been regarded as the most appropriate exposure metric associated with health effects of particle exposures. However, the appropriateness of the mass concentration metric for ultrafine particles remains questionable. Particle number and surface area concentrations have been proposed as more suitable alternatives to the traditional mass metric. Another consideration is that even very low concentrations of nanosized materials in the air represent very high particle number concentrations. Particle size is an important parameter in causing toxicity. As particle size becomes smaller, a greater fraction of atoms are at the surface and quantum effects tend to increase surface reactivity. In light of these points, it is recommended that measurements of airborne particle mass, surface area, and number concentrations be conducted using real-time instruments. There is value in maintaining both the time-averaged results and the real-time data. Real-time measurements of mass, surface area, and number concentrations can be measured directly or calculated through measurements of the particle size distribution.