Airborne Monitoring to Distinguish Engineered Nanomaterials from Incidental Particles for Environmental Health and Safety

Abstract

Two methods were used to distinguish airborne engineered nanomaterials from other airborne particles in a facility that produces nano-structured lithium titanate metal oxide powder. The first method involved off-line analysis of filter samples collected with conventional respirable samplers at each of seven locations (six near production processes and one outdoors). Throughout most of the facility and outdoors, respirable mass concentrations were low (<0.050 mg m−3) and were attributed to particles other than the nanomaterial (<10% by mass titanium determined with inductively coupled plasma atomic emission spectrometry). In contrast, in a single area with extensive material handling, mass concentrations were greatest (0.118 mg m−3) and contained up to 39% +/− 11% lithium titanium, indicating the presence of airborne nanomaterial. Analysis of the filter samples collected in this area by transmission electron microscope and scanning electron microscope revealed that the airborne nanomaterial was associated only with spherical aggregates (clusters of fused 10–80 nm nanoparticles) that were larger than 200 nm. This analysis also showed that nanoparticles in this area were the smallest particles of a larger distribution of submicrometer chain agglomerates likely from welding in an adjacent area of the facility. The second method used two, hand-held, direct-reading, battery-operated instruments to obtain a time series of very fine particle number (<300 nm), respirable mass, and total mass concentration, which were then related to activities within the area of extensive material handling. This activity-based monitoring showed that very fine particle number concentrations (<300 nm) had no apparent correlation to worker activities, but that sharp peaks in the respirable and total mass concentration coincided with loading a hopper and replacing nanomaterial collection bags. These findings were consistent with those from the filter-based method in that they demonstrate that airborne nanoparticles in this facility are dominated by "incidental" sources (e.g., welding or grinding), and that the airborne "engineered" product is predominately composed of particles larger than several hundred nanometers. The methods presented here are applicable to any occupational or environmental setting in which one needs to distinguish incidental sources from engineered product.

Nano-objects emitted during maintenance of common particle generators: direct chemical characterization with aerosol mass spectrometry and implications for risk assessments

“…Similar large-scale agglomerates with nanostructured surfaces, as the ones found in this paper, have also been observed by others during different types of mechanical processing of nanomaterials (Peters et al 2009;Methner et al 2010a;Zimmermann et al 2012). Such agglomerates may share similar structures to particles studied during powder dustiness tests (Evans et al 2013).…”

“…Maintenance and cleaning of nanoparticle generators and production equipment may be an important source of MNOs since such emissions often are difficult to control because they often have to take place outside any enclosed environment. Large agglomerates (>1 µm) with nanosized structures have been observed during mechanical cleaning or processing of engineered nanomaterials (Bello et al 2009;Peters et al 2009;Koivisto et al 2012b;Zimmermann et al 2012). A deeper discussion regarding lung deposition and the fate of emitted nanoparticles in the respiratory tract is to a large extent absent but is covered by Koivisto et al (2012a); (2012b) through calculations of deposited dose.…”

Comparison of Nanoparticle Exposure Levels Based on Facility Type—Small-Scale Laboratories, Large-Scale Manufacturing Workplaces, and Unintended Nanoparticle-Emitting Workplaces

“…Exposure assessment and control strategy based on time-weighted average (TWA) approaches may not be appropriate, especially at LAB, because it may not reflect variation between tasks. Therefore, task-based exposure assessment strategies may be a feasible method of evaluating nanoparticle exposure (Peters et al, 2008;Cena and Peters, 2011;Ham et al, 2012).…”

“…Therefore, several instruments have been used to measure nanoparticles (Peters et al, 2008;Ham et al, 2012;Methner et al, 2012). The SMPS could characterize the size distribution of nanoparticles as well as concentration with several channels but it is expensive and heavy.…”

Conceptual model for assessment of inhalation exposure to manufactured nanoparticles

“…The authors concluded that dispersion into the air did not result in much dissociation of the agglomerates present in the bulk powder. Results from workplace measurements suggest that the bimodal size distributions obtained by dustiness tests are representative for workplace conditions (Kuhlbusch et al, 2004;Kuhlbusch and Fissan, 2006;Fujitani et al, 2008;Old and Methner, 2008;Yeganeh et al, 2008;Peters et al, 2009). ART assigns an intrinsic substance emission potential for powders to one of the six classes; that is, solid objects, firm granules or flakes, granules or flakes, coarse dust, fine dust, and extremely dusty product with associated scores (Fransman et al, 2009).…”