Last data update: Jan 27, 2025. (Total: 48650 publications since 2009)
Records 1-5 (of 5 Records) |
Query Trace: Topmiller J[original query] |
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Particle emissions from laboratory activities involving carbon nanotubes
Lo LM , Tsai CSJ , Heitbrink WA , Dunn KH , Topmiller J , Ellenbecker M . J Nanopart Res 2017 18 (293) This site study was conducted in a chemical laboratory to evaluate nanomaterial emissions from 20–30-nm-diameter bundles of single-walled carbon nanotubes (CNTs) during product development activities. Direct-reading instruments were used to monitor the tasks in real time, and airborne particles were collected using various methods to characterize released nanomaterials using electron microscopy and elemental carbon (EC) analyses. CNT clusters and a few high-aspect-ratio particles were identified as being released from some activities. The EC concentration (0.87 μg/m3) at the source of probe sonication was found to be higher than other activities including weighing, mixing, centrifugation, coating, and cutting. Various sampling methods all indicated different levels of CNTs from the activities; however, the sonication process was found to release the highest amounts of CNTs. It can be cautiously concluded that the task of probe sonication possibly released nanomaterials into the laboratory and posed a risk of surface contamination. Based on these results, the sonication of CNT suspension should be covered or conducted inside a ventilated enclosure with proper filtration or a glovebox to minimize the potential of exposure. |
Nano-metal oxides: Exposure and engineering control assessment
Garcia A , Eastlake A , Topmiller JL , Sparks C , Martinez K , Geraci CL . J Occup Environ Hyg 2017 14 (9) 0 In January 2007, the National Institute for Occupational Safety and Health (NIOSH) conducted a field study to evaluate process specific emissions during the production of ENMs. This study was performed using the nanoparticle emission assessment technique (NEAT). During this study, it was determined that ENMs were released during production and cleaning of the process reactor. Airborne concentrations of silver, nickel, and iron were found both in the employee's personal breathing zone and area samples during reactor cleaning. At the completion of this initial survey, it was suggested that a flanged attachment be added to the local exhaust ventilation system. NIOSH re-evaluated the facility in December 2011 to assess worker exposures following an increase in production rates. This study included a fully comprehensive emissions, exposure, and engineering control evaluation of the entire process. This study made use of the nanoparticle exposure assessment technique (NEAT 2.0). Data obtained from filter-based samples and direct reading instruments indicate that reactor cleanout increased the overall particle concentration in the immediate area. However, it does not appear that these concentrations affect areas outside of the production floor. As the distance between the reactor and the sample location increased, the observed particle number concentration decreased, creating a concentration gradient with respect to the reactor. The results of this study confirm that the flanged attachment on the local exhaust ventilation system served to decrease exposure potential. Given the available toxicological data of the metals evaluated, caution is warranted. One should always keep in mind that occupational exposure levels were not developed specifically for nanoscale particles. With data suggesting that certain nanoparticles may be more toxic than the larger counterparts of the same material; employers should attempt to control emissions of these particles at the source, to limit the potential for exposure. |
Performance of particulate containment at nanotechnology workplaces
Lo LM , Tsai CSJ , Dunn KH , Hammond D , Marlow D , Topmiller J , Ellenbecker M . J Nanopart Res 2015 17 435 The evaluation of engineering controls for the production or use of carbon nanotubes (CNTs) was investigated at two facilities. These control assessments are necessary to evaluate the current status of control performance and to develop proper control strategies for these workplaces. The control systems evaluated in these studies included ventilated enclosures, exterior hoods, and exhaust filtration systems. Activity-based monitoring with direct-reading instruments and filter sampling for microscopy analysis were used to evaluate the effectiveness of control measures at study sites. Our study results showed that weighing CNTs inside the biological safety cabinet can have a 37 % reduction on the particle concentration in the worker's breathing zone, and produce a 42 % lower area concentration outside the enclosure. The ventilated enclosures used to reduce fugitive emissions from the production furnaces exhibited good containment characteristics when closed, but they failed to contain emissions effectively when opened during product removal/harvesting. The exhaust filtration systems employed for exhausting these ventilated enclosures did not provide promised collection efficiencies for removing engineered nanomaterials from furnace exhaust. The exterior hoods were found to be a challenge for controlling emissions from machining nanocomposites: the downdraft hood effectively contained and removed particles released from the manual cutting process, but using the canopy hood for powered cutting of nanocomposites created 15-20 % higher ultrafine (<500 nm) particle concentrations at the source and at the worker's breathing zone. The microscopy analysis showed that CNTs can only be found at production sources but not at the worker breathing zones during the tasks monitored. |
Airborne exposure patterns from a passenger source in aircraft cabins
Bennett JS , Jones BW , Hosni MH , Zhang Y , Topmiller JL , Dietrich WL . HVAC&R Res 2013 19 (8) 962-973 Airflow is a critical factor that influences air quality, airborne contaminant distribution, and disease transmission in commercial airliner cabins. The general aircraft-cabin air-contaminant transport effect model seeks to build exposure-spatial relationships between contaminant sources and receptors, quantify the uncertainty, and provide a platform for incorporation of data from a variety of studies. Knowledge of infection risk to flight crews and passengers is needed to form a coherent response to an unfolding epidemic, and infection risk may have an airborne pathogen exposure component. The general aircraft-cabin air-contaminant transport effect model was applied to datasets from the University of Illinois and Kansas State University and also to case study information from a flight with probable severe acute respiratory syndrome transmission. Data were fit to regression curves, where the dependent variable was contaminant concentration (normalized for source strength and ventilation rate), and the independent variable was distance between source and measurement locations. The data-driven model showed exposure to viable small droplets and post-evaporation nuclei at a source distance of several rows in a mock-up of a twin-aisle airliner with seven seats per row. Similar behavior was observed in tracer gas, particle experiments, and flight infection data for severe acute respiratory syndrome. The study supports the airborne pathway as part of the matrix of possible disease transmission modes in aircraft cabins. |
Exploring the use of nonmedical sources of prescription drugs among immigrant Latinos in the rural Southeastern USA
Vissman AT , Bloom FR , Leichliter JS , Bachmann LH , Montano J , Topmiller M , Rhodes SD . J Rural Health 2011 27 (2) 159-167 BACKGROUND: Little is known about access to medicine among immigrant Latinos in the United States (US). This study explored access to, and use of, prescription drugs obtained from nonmedical sources among recently arrived, Spanish-speaking immigrant Latinos in rural North Carolina (NC). METHODS: Our community-based participatory research partnership collected, analyzed, and interpreted data from individual in-depth interviews with Latino community members and rural health service providers. A purposive sample of 30 community members, including traditional healers, religious leaders, transgender Latinos, heterosexual Latino men and women, and Latino gay men, were interviewed to gain emic ("insider") perspectives on use of nonmedical sources of prescription drugs. Six local Latino health service providers also were interviewed to gain etic ("outsider") perspectives on use. RESULTS: Participants described the roles of tiendas (grocers), family, and social networks in accessing treatment advice and prescription drugs. They described health care expectations among immigrants and contingencies for accessing prescription drugs in the US. Prescription medicines (eg, antibiotics, hormones, Viagra, analgesics), injection equipment (eg, syringes), and medical advice were identified as readily available from nonmedical sources. CONCLUSIONS: Increased access to formalized health care and effective health education initiatives are needed to meet the challenges facing immigrant Latinos. |
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