A structured observational method to assess dermal exposure to manufactured nanoparticles DREAM as an initial assessment tool.

Preliminary results of inventories of exposure scenarios for nanomaterials have indicated possible dermal exposure. Within the NANOSH project focused on occupational safety and health aspects of nanotechnology a shortened version of the observational DeRmal Exposure AssessMent (DREAM) method was used as an initial method to assess dermal exposure. A total of 45 tasks (such as bagging, dumping, and cleaning) involving different manufactured nanoparticles (MNPs) such as carbon nanotubes, fumed silica, and cerium oxide, were observed in industrial and research facilities. In 39 tasks potential dermal exposure (that is, exposure of the skin and clothing) was likely to occur. Exposure resulted from different routes, including direct contact with MNPs as well as the deposition or transfer of MNPs. The survey showed it is both feasible and useful to assess the potential dermal exposure using shortened DREAM questionnaires.

An International comparison of the crystallinity of calibration materials for the analysis of respirable alpha-quartz using X-ray diffraction and a comparison with results from the infrared KBr disc method.

It is important that analytical results, produced to demonstrate compliance with exposure limits are comparable, to ensure controls are monitored to similar standards. Correcting a measurement result of respirable alpha-quartz for the percentage of crystalline material in the calibration dust is good analytical practice and significant changes in the values assigned to calibration materials will affect the interpretation of results by an analyst or occupational hygiene professional. The reissue of the certification for the quartz reference material NIST 1878a in 2005 and differences in comparative values obtained by other work created uncertainty about the values of crystallinity assigned to national calibration dusts for alpha-quartz. Members of an International Organization for Standardization working group for silica measurement ISO/TC146/SC2/WG7 collaborated to investigate the comparability of results by X-ray diffraction (XRD) and to reach a consensus. This paper lists the values recommended by the working group for use with XRD analysis. The values for crystallinity obtained for some of the materials (NIST 1878, Min-U-Sil5 and A9950) were 6-7% lower than the original certification or estimates reported in other comparisons. Crystallinity values obtained by XRD gave a good correlation with BET surface area measurements (r2 = 0.91) but not with mean aerodynamic particle size (r2 = 0.31). Subsamples of two of the materials (A9950 Respirable and Quin 1 Respirable) with smaller particle size distribution than their parent material did not show any significant change in their values for crystallinity, suggesting that the area XRD measurement of these materials within the particle size range collected is more dependent on how the quartz is formed geologically or how it is processed for use. A comparison of results from laboratories using the infrared (IR) and KBr disc method showed that this method is more dependent than XRD on differences in the particle size within the respirable size range, whereas the XRD values were more consistent between the different measurement values obtained on each material. It was not possible to assign a value for percentage purity to each material for users of IR analysis. This work suggests that differences are likely to exist between the results from XRD and IR analysis when measuring 'real' workplace samples and highlights the importance of matching the particle size of the calibration material to the particle size of the workplace dust for measurements of crystalline quartz.