Hyunwook Kim

Assessment of Nanoparticle Exposure in Nanosilica Handling Process: Including Characteristics of Nanoparticles Leaking from a Vacuum Cleaner

Nanosilica is one of the most widely used nanomaterials across the world. However, their assessment data on the occupational exposure to nanoparticles is insufficient. The present study performed an exposure monitoring in workplace environments where synthetic powders are prepared using fumed nanosilica. Furthermore, after it was observed during exposure monitoring that nanoparticles were emitted through leakage in a vacuum cleaner (even with a HEPA-filter installed in it), the properties of the leaked nanoparticles were also investigated. Workers were exposed to high-concentration nanosilica emitted into the air while pouring it into a container or transferring the container. The use of a vacuum cleaner with a leak (caused by an inadequate sealing) was found to be the origin of nanosilica dispersion in the indoor air. While the particle size of the nanosilica that emitted into the air (during the handling of nanosilica by a worker) was mostly over 100u2005nm or several microns (µm) due to the coagulation of particles, the size of nanosilica that leaked out of vacuum cleaner was almost similar to the primary size (mode diameter 11.5u2005nm). Analysis of area samples resulted in 20% (60% in terms of peak concentration) less than the analysis of the personals sample.

Ultrafine Particle Characteristics in a Rubber Manufacturing Factory

BACKGROUNDnAccording to epidemiological research, exposure to rubber fumes can cause various types of cancer and can lead to an increase in death rate because of cardiovascular diseases.nnnOBJECTIVESnIn this study, we have assessed the characteristics of ultrafine particles emitted into the air during the manufacturing of rubber products using waste tires.nnnMETHODSnTo assess the aerosol distribution of rubber fumes in the workplace from a product during curing, we have performed particle number concentration mapping using a handheld condensation particle counter. The particle number concentration of each process, count median diameter (CMD), and nanoparticle ratio (<100nm) were determined using an electrical low-pressure impactor (ELPI), and the surface area concentration was determined using a surface area monitor. The shape and composition of the sampled rubber fumes were analyzed using an ELPI-transmission electron microscopy grid method. Further, the rubber fume mass concentration was determined according to the Methods for the Determination of Hazardous Substances 47/2.nnnRESULTSnThe results of particle mapping show that the rubber fumes were distributed throughout the air of the workplace. The concentration was the highest during the final process of the work. The particle number concentration and the surface area concentration were 545 000cm(-3) and 640 µm(2) cm(-3), respectively, approximately 10- and 4-fold higher than those in the outdoor background. During the final process, the CMD and the nanoparticle ratio were 26nm and 94%, respectively. Most of the rubber fume particles had a compact shape because of the coagulation between particles. The main components of these fumes were silicon and sulfur, and heavy metals such as zinc were detected in certain particles. The filter concentration of the rubber fumes was 0.22mg m(-3), lower than the UK workplace exposure limit of 0.6mg m(-3).nnnCONCLUSIONSnTherefore, the rubber manufacturing process is a potentially dangerous process that produces a high concentration of specific nanoparticles.

Comparison of nanoparticle exposures between fumed and sol-gel nano-silica manufacturing facilities.

Silica nanoparticles (SNPs) are widely used all around the world and it is necessary to evaluate appropriate risk management measures. An initial step in this process is to assess worker exposures in their current situation. The objective of this study was to compare concentrations and morphologic characteristics of fumed (FS) and sol-gel silica nanoparticles (SS) in two manufacturing facilities. The number concentration (NC) and particle size were measured by a real-time instrument. Airborne nanoparticles were subsequently analyzed using a TEM/EDS. SNPs were discharged into the air only during the packing process, which was the last manufacturing step in both the manufacturing facilities studied. In the FS packing process, the geometric mean (GM) NC in the personal samples was 57,000 particles/cm3. The geometric mean diameter (GMD) measured by the SMPS was 64u2005nm. Due to the high-temperature formation process, the particles exhibited a sintering coagulation. In the SS packing process that includes a manual jet mill operation, the GM NC was calculated to be 72,000 particles/cm3 with an assumption of 1,000,000 particles/cm3 when the upper limit is exceeded (5% of total measure). The particles from SS process had a spherical-shaped morphology with GMD measured by SMPS of 94u2005nm.

Assessing real-time performances of N95 respirators for health care workers by simulated workplace protection factors

To assess performances of N95 respirators for Health Care Workers (HCWs) in a simulated health-care setting, we measured the Simulated Workplace Protection Factors (SWPFs) in real-time from the volunteers. A total of 49 study subjects, wearing 3u2005M respirator Model N95 1860 and 1860S, were fit tested using the OSHA Exercise Regimen. The test subjects were asked to perform simulated scenarios, including patient assessments, suction, and intravenous injection (IV) treatment. Two TSI PortaCount instruments continuously measured concentrations in the respirator and the room concentration. For Quantitative Fit Testing (QNFT), 36 out of 49 (73.5%) passed the fit factor (FF) criteria set at 100 and 13 (26.5%) failed. The results of QNFT were found to have a low correlation with SWPF, with R2=0.32. The geometric means (GM) and geometric standard deviations (GSD) of SWPF were 68.8 (1.1) for those subjects who passed and 39.6 (1.3) for those who failed. Real-time assessments of SWPF showed that lower SWPFs were; moving head up and down, and bending at the waist. This study identifies the needs for providing different sizes of respirators for HCWs and the importance of performing fit tests for HCWs regularly. And particular movements were identified as attributing factors affecting more on SWPFs.

Evaluating the efficiency of an asbestos stabilizer on ceiling tiles and the characteristics of the released asbestos fibers

The efficiency of asbestos stabilizers and their adaptability were evaluated by investigating the characteristics of asbestos fibers released from ceiling tiles. The impact of such variables as the wind speed or vibration conditions was also studied along with the asbestos stabilizers. The concentrations of the asbestos fibers released from damaged ceiling tiles treated with stabilizers decreased by 69.5-84.4% compared with those of untreated tiles for all variables, with a statistically significant difference (p<0.001). The effects of the environmental factors on the asbestos concentrations were analyzed through a multiple regression analysis. It was determined that the surface status of the ceiling tiles and stabilizers were the main factors affecting the concentration, and the reliability of these factors was estimated as 58.3%. The lengths of the chrysotile fibers released from the damaged ceiling tiles were in the range of 0.991-79.1 μm for the untreated tiles and 3.74-35.6 μm for the tiles treated with inorganic stabilizers. It was confirmed that inorganic stabilizers are more efficient for damaged ceiling tiles. The results of this study also show that the asbestos concentrations are greatly reduced after treating damaged ceiling tiles with a stabilizer.

Comparison of Fit Factor for Healthcare Workers Before and After Training with the N95 Mask

Objectives: This study compares the differences of fit factors before and after training on the N95 mask. The results will be utilized to suggest the need of providing effective training on respirator use. Methods: A total of 49 study subjects were tested, comprised of nurses from a general hospital and undergraduate nursing students from a medical school. Anthropometric measurements of face length and face width were compared with the NIOSH(National Institute for Occupational Safety and Health) panel. Fit factors(FF) were measured with TSI Portacount Pro+ 8038 before and after on-site training regarding the proper use of respirators. The FF pass/fail criterion was set at 100. Results: Two subjects(4.1 %) passed the fit test before training on use of the N95. However, 36(73.5%) of the 49 passed the test after training. Overall the FF(GM(GSD)) was 13.4(3.2) before training, but improved to 106.6(2.1) after training, which was statistically significant. These findings suggest the efficacy of educational intervention, and the performance of the direct on-site training proved to be better than that of the traditional educational methods. Conclusions: This study showed the effect of on-site training of the N95 respirator among health care workers(HCW). Therefore, providing effective training on the use of N95 for HCWs before their work assignments will greatly reduce exposure to harmful agents. It is recommended that fit testing be mandated to check for adequate protection being provided by the given respirators.

The education and practice program for medical students with quantitative and qualitative fit test for respiratory protective equipment

Tuberculosis infection is prevalent in Korea and health care workers are vulnerable to tuberculosis infection in the hospital. The aims of this study were to develop and validate an education program that teaches senior medical students how to wear and choose the proper size and type of respiratory protective equipment (RPE), which may help reduce the risk of contracting Mycobacterium tuberculosis (MTB) from patients. Overall, 50 senior medical students participated in this education program. Methods of choosing the proper type of RPE, performing a fit check of the RPE, and choosing a suitable mask size were taught by certified instructors using the real-time quantitative fit test (QNFT). The validity of education program was evaluated with qualitative fit test (QLFT) before and after the education as pass or fail. The education program was effective, as shown by the significantly pass rate (increased 30 to 74%) in the QLFT after the education program (p<0.05). Among study participants, changing mask size from medium to small significantly increased the pass rate (p<0.001). Incorporation of this program into the medical school curriculum may help reduce risk of MTB infection in medical students working in the hospital.

199 Evaluation of quantitative fit test results for female health care workers in korea

Introduction Risk of infections due to communicable pathogens among health care workers is very high. Though many counter measures have been implemented, respiratory protective devices (RPD) are very common in use for prevention of the inhalation of pathogens. Nevertheless, proper education and training of RPDs are lacking for health care workers. This study is focused on the actual RPDs use and the fit tests so as to establishing effective training programs. Methods A total of 393 female health care workers were recruited for quantitative fit testing (QNFT), with at least 2 RPDs out of 4 different types of RPDs provided. The U.S. OSHA Fit Test protocol was used to conduct the fit test exercises along with the pass criteria (FF >100). The QNFT results were analysed by division and occupation using STATA. Results Among participants, all occupations showed relatively high pass percentages except doctors who showed about 40% of failure with the Folder shaped mask. For almost all divisions, the cup shaped and the cup shaped small size mask showed the highest fail rate, but the folder shaped mask showed lower failure rates. Within the hospital, different failure rates were observed between divisions; emergency room=13.5%, MICU=3.6%, SICU=8.8%, BMTICU=15.4%, isolation ward=6.7%, respiratory/infection control division=3.7%, PICU=0.0%, and CCU=4.3%, respectively. While no association between types of occupation and QNFT result were observed, QNFT results were statistically significantly different between divisions (χ2=17.122, p=0.017). Discussion The results of this study showed that some RPDs perform better in terms of respiratory protection providedaccording to the subjects’facial shapes. And health care professionalsneed formal educationand training for the use of RPDs, regardless of their occupations. Properdonning experiences of RPDs arehighly recommended and annual QNFT are recommended for checking the effectiveness of RPDs.

Real-time measurement of fibers using an HY-differential mobility analyzer with an optical particle counter (KOFAM)

This study investigated the applicability of an HY-differential mobility analyzer with an optical particle counter (HY-DMA/OPC), named as KOFAM, for counting fibrous matters in real time. Fibers separated from particles by the HY-DMA were counted with an OPC. To assess the KOFAM performance, the proposed method and the conventional gold standard phase contrast microscopy (PCM) method were compared in terms of variables such as recovery, relative difference, coefficient of determination, and conformity. The optimal sheath-to-aerosol (outlet) flow ratio of the internal flow in the HY-DMA was determined to be 1.6:1. In terms of recovery of the HY-DMA, the highest recovery was obtained at a voltage of 500 V regardless of which type of asbestos was tested. The recovery rate for serpentine was 45.5% and that for amphibole was 34.9%. The coefficients of determination of serpentine (R2 = 0.89) and amphibole (R2 = 0.87) were highly correlated. With respect to the coefficient of variation (CV), the KOFAM demonstrated superior performance over the M7400AD and F-1 methods and showed almost no difference from the PCM method (KOFAM: 22.5%, M7400AD: 32.4%, F-1: 88.8%, and PCM: 21.9%). There was no statistically significant difference between concentration measurements of the KOFAM and PCM analyses. Accordingly, it was concluded that the KOFAM can be used as a superior alternative to conventional fiber measurement methods. The preliminary results support the use of the KOFAM for constant measurement of airborne asbestos concentrations in real time.

0026 Development of a new preparation method of human lung tissues for analysing asbestos fibres by tem

Characterisation and quantification of asbestos fibres in human lung tissues are critical for assessing occupational environmental exposures and epidemiological studies of asbestos related disease. To develop a reliable preparation method of human lung tissues for TEM-EDXA analysis, three conventional preparation methods and a new method were compared. Tissue preparation methods compared were; 5% NaOCl(digestion I), 40% KOH(digestion II), a low temperature plasma(ashing), and the new proposed method of 30% H2O2 digestion followed by a low temperature plasma (sequential application of the digestion and ashing). After treatment, aliquot of samples were filtered and filters were carbon coated and jaffe washed for TEM analysis. A total of 90 human tissues were tested for comparison. Results showed that the digestion I method could not detect asbestos fibres because of using limited amount of aliquot sample for analysis. For the digestion II method, organic materials were not completely removed which obscured the images of the asbestos fibres. For the ashing method, clear background images were obtained but some tremolite asbestos fibres were found to be damaged, either bent or broken. Using the proposed method, asbestos fibres were detected clearly and no fibres were damaged. In summary, we proposed a new preparation method for treating asbestos fibres in the human lung tissues for TEM analysis. Not only showed it a superior quality for asbestos fibres detection but also no damages on asbestos fibres observed. Therefore, we are confident that it can be utilised for preparing human lung tissues for TEM analysis.