Improving Sensitivity and Specificity when Measuring Environmental Exposure to Engineered Nanoparticle Releases with the Use of Low-Background Techniques

Download or read book Improving Sensitivity and Specificity when Measuring Environmental Exposure to Engineered Nanoparticle Releases with the Use of Low-Background Techniques written by Heather Laine Papinchak and published by . This book was released on 2013 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt: As applications of nanotechnology expand, there is an increasing need to develop inexpensive, sensitive, and specific procedures to measure occupational exposures to engineered nanoparticles (ENPs). The use of hand-held direct reading instruments to screen for airborne ENPs is attractive due to the relatively low cost of such commercially available instruments and the immediate feedback provided. However, because ambient air typically contains thousands of non-engineered nanoparticles per cubic centimeter (pt/cm3), this background particle concentration must be accounted for in quantifying ENPs. Incidental nanoscale particles are present in many workplaces due to sources including internal combustion engines, grinding and welding, electric motors, office equipment, printers, and infiltration of contaminated outside air. Because ENP toxicity has not been investigated comprehensively, and because some studies suggest that certain ENPs may be highly toxic, the risk management philosophy of many organizations is that exposure to ENPs above background nanoparticle levels is not acceptable. Industrial hygienists have generally approached ENP sampling with the notion that if ENPs cannot be detected above background levels in the sampling environment, exposure to ENPs is not occurring. If there is a low signal-to-noise ratio, however, this approach underestimates ENP exposure intensity, and large fluctuations in background concentrations could make it difficult to measure actual releases of ENPs. Therefore, it is important to accurately discern between background non-engineered nanoparticle and ENP concentrations. The few ENP exposure studies that have been published tend to inadequately account for background nanoparticles. Tools and techniques were developed to improve the sensitivity and specificity of ENP exposure measurements in research laboratories based on direct reading instruments and filter-based sampling. These research facilities were located at the Lawrence Berkeley National Laboratory (LBNL). A portable fume-hood antechamber enclosure and a portable, bottomless glovebox enclosure were constructed. These enclosures are supplied with air passed through a high efficiency particulate air (HEPA) filter air, and ENP-handling tasks are performed within the enclosures. HEPA filtration greatly reduces the nanoparticle concentration in the supply air and thereby increases the ENP signal-to-noise ratio. Based on measurements made with a commercially available CPC, a 100- to 300-fold increase in sensitivity was achieved with the clean air enclosures. Combined with high-resolution microscopy analysis of particles collected on filter samples of air, employee exposures to ENPs that were previously not detectable using traditional sampling techniques were quantified. Three different monitoring studies are described in this dissertation. The first study characterized airborne metal-oxide LiNi0.45Mn0.45Co0.1-yAlyO2 ENP emissions associated with a nanomaterial synthesis comprised of three steps - heating a precursor solution, combustion, and harvesting - all conducted within a laboratory fume hood. With the use of the cleanroom enclosure, background particle concentration levels of 0-2 pt/cm3 were achieved. A CPC was located in the cleanroom enclosure at waist-level or near the personal breathing zone (PBZ) of the LBNL researcher, and a second CPC was located inside the laboratory fume hood. The maximum of 465,129 pt/cm3 (measured inside the fume hood) was the highest particle concentration recorded in this research. For all the combustion events, I observed plumes of black particles which corresponded in time with the highest particle measurements. To my knowledge, there are no published studies that have shown such high particle number concentrations from ENP synthesis. At the conclusion of the synthesis, ENM was found on fume hood surfaces and equipment, and on the CPC instrument located in the fume hood. ANOVA demonstrated that the mean particle number concentrations were not equal across the three steps (p