Challenges in evaluating nanoparticle occupational exposures

In 2006, NIOSH developed a sampling strategy to semi-quantitatively evaluate exposures in nanomaterial workplaces that consisted of a combination of field portable, direct reading instrumentation (DRI) and filter-based air sampling with subsequent laboratory analysis. An analysis of the data from the use of this sampling strategy over the course of 20 field investigations revealed important limitations that required a re-assessment and re-calibration of the strategy to promote a more quantitative approach that could result in intervention recommendations that are evidence based. Metric selection was coordinated with NIOSH toxicological research to ensure consistency in exposure characterization between controlled laboratory study and the field. A hypothesis-driven approach, focus on integrated air sampling, attention to surface contamination, a detailed assessment of engineering control use, and the supplemental use of DRIs to address engineering control deficiencies and worker practices has been used in 10 new field investigations. In our discussion, we elaborate further on usefulness of the new NIOSH direction in exposure characterization and the application in risk assessment models and incorporation into intervention strategies such as control banding.