Impact of Naturally Occurring Asbestos on Asbestos Ban: Regulations and Experience of the Republic of Korea.

This review examined the main issues debated in Korea regarding the production and use of materials containing naturally occurring asbestos (NOA) as impurities, and investigated the impacts of these debates on the asbestos ban, as well as the future implications. In Korea, incidents associated with the production and use of NOA-contaminated talc powders, construction rocks, serpentinites, and dolomite rocks raised public concern and led to accelerating the ban on asbestos. The main controversies concern policies on appropriate asbestos content limits, whether materials containing a trace amount of NOA should be banned, and the control of materials with high human exposure risk. To address recurring controversies, the implementation of preventive measures to manage elongated mineral particles and the use of transmission electron microscopy for more sensitive analysis need to be discussed, along with reaching social agreement on the controversial policies. To minimize the potential exposure to asbestos that may occur during the production and use of industrial minerals in the future, it is necessary to apply occupational exposure control measures and monitor the health effects of the relevant population groups. These national policies on NOA should be prepared based on close collaboration and discussion with policymakers, industry stakeholders, and related academic experts.

Characterization of aerosolized particles from nanoclay-enabled composites during manipulation processes.

Manufacturing, processing, use, and disposal of nanoclay-enabled composites potentially lead to the release of nanoclay particles from the polymer matrix in which they are embedded; however, exposures to airborne particles are poorly understood. The present study was conducted to characterize airborne particles released during sanding of nanoclay-enabled thermoplastic composites. Two types of nanoclay, Cloisite® 25A and Cloisite® 93A, were dispersed in polypropylene at 0%, 1%, and 4% loading by weight. Zirconium aluminum oxide (P100/P180 grits) and silicon carbide (P120/P320 grits) sandpapers were used to abrade composites in controlled experiments followed by real-time and offline particle analyses. Overall, sanding the virgin polypropylene with zirconium aluminum oxide sandpaper released more particles compared to silicon carbide sandpaper, with the later exhibiting similar or lower concentrations than that of polypropylene. Thus, a further investigation was performed for the samples collected using the zirconium aluminum oxide sandpaper. The 1% 25A, 1% 93A, and 4% 93A composites generated substantially higher particle number concentrations (1.3-2.6 times) and respirable mass concentrations (1.2-2.3 times) relative to the virgin polypropylene, while the 4% 25A composite produced comparable results, regardless of sandpaper type. It was observed that the majority of the inhalable particles were originated from composite materials with a significant number of protrusions of nanoclay (18-59%). These findings indicate that the percent loading and dispersion of nanoclay in the polypropylene modified the mechanical properties and thus, along with sandpaper type, affected the number of particles released during sanding, implicating the cause of potential adverse health effects.

Development of the KOSHA Proficiency Testing Scheme on Asbestos Analysis in Korea.

This commentary presents the regulatory backgrounds and development of the national proficiency testing (PT) scheme on asbestos analysis in the Republic of Korea. Since 2009, under the amended Occupational Safety and Health Act, the survey of asbestos in buildings and clearance test of asbestos removal works have been mandated to be carried out by the laboratories designated by the Ministry of Employment and Labor (MOEL) in the Republic of Korea. To assess the performance of asbestos laboratories, a PT scheme on asbestos analysis was launched by the Korea Occupational Safety and Health Agency (KOSHA) on behalf of the MOEL in 2007. Participating laboratories are evaluated once a year for fiber counting and bulk asbestos analysis by phase contrast microscopy and polarized light microscopy, respectively. Currently, the number of laboratory enrollments is > 200, and the percentage of passed laboratories is > 90. The current status and several significant changes in operation, sample preparations, and statistics of assigning the reference values of the KOSHA PT scheme on asbestos analysis are presented. Critical retrospect based on the experiences of operating the KOSHA PT scheme suggests considerations for developing a new national PT scheme for asbestos analysis.

High-strain-rate brain injury model using submerged acute rat brain tissue slices.

Blast-induced traumatic brain injury (bTBI) has received increasing attention in recent years due to ongoing military operations in Iraq and Afghanistan. Sudden impacts or explosive blasts generate stress and pressure waves that propagate at high velocities and affect sensitive neurological tissues. The immediate soft tissue response to these stress waves is difficult to assess using current in vivo imaging technologies. However, these stress waves and resultant stretching and shearing of tissue within the nano- to microsecond time scale of blast and impact are likely to cause initial injury. To visualize the effects of stress wave loading, we have developed a new ex vivo model in which living tissue slices from rat brain, attached to a ballistic gelatin substrate, were subjected to high-strain-rate loads using a polymer split Hopkinson pressure bar (PSHPB) with real-time high-speed imaging. In this study, average peak fluid pressure within the test chamber reached a value of 1584±63.3 psi. Cavitation due to a trailing underpressure wave was also observed. Time-resolved images of tissue deformation were collected and large maximum eigenstrains (0.03-0.42), minimum eigenstrains (-0.33 to -0.03), maximum shear strains (0.09-0.45), and strain rates (8.4×10³/sec) were estimated using digital image correlation (DIC). Injury at 4 and 6 h was quantified using Fluoro-Jade C. Neuronal injury due to PSHPB testing was found to be significantly greater than injury associated with the tissue slice paradigm alone. While large pressures and strains were encountered for these tests, this system provides a controllable test environment to study injury to submerged brain slices over a range of strain rate, pressure, and strain loads.

Compressive strain rate sensitivity of ballistic gelatin.

Gelatin is a popular tissue simulant used in biomedical applications. The uniaxial compressive stress-strain response of gelatin was determined at a range of strain rates. In the quasistatic regime, gelatin strength remained relatively constant. With increase in loading rate, the compressive strength increased from 3kPa at a strain rate of around 0.0013/s to 6MPa at a strain rate of around 3200/s. This dramatic increase in strength of gelatin at high rates is attributed to its shear-thickening behavior and is argued on the basis of hydrocluster formation mechanism and differences in internal energy dissipation mechanism under static and dynamic loading.

Characteristics of Occupational Exposure to Benzene during Turnaround in the Petrochemical Industries.

OBJECTIVES: The level of benzene exposure in the petrochemical industry during regular operation has been well established, but not in turnaround (TA), where high exposure may occur. In this study, the characteristics of occupational exposure to benzene during TA in the petrochemical companies were investigated in order to determine the best management strategies and improve the working environment. This was accomplished by evaluating the exposure level for the workers working in environments where benzene was being produced or used as an ingredient during the unit process. METHODS: From 2003 to 2008, a total of 705 workers in three petrochemical companies in Korea were studied. Long- and short-term (< 1 hr) samples were taken during TAs. TA was classified into three stages: shut-down, maintenance and start-up. All works were classified into 12 occupation categories. RESULTS: The long-term geometric mean (GM) benzene exposure level was 0.025 (5.82) ppm (0.005-42.120 ppm) and the short-term exposure concentration during TA was 0.020 (17.42) ppm (0.005-61.855 ppm). The proportions of TA samples exceeding the time-weighted average, occupational exposure level (TWA-OEL in Korea, 1 ppm) and the short-term exposure limit (STEL-OEL, 5 ppm) were 4.1% (20 samples of 488) and 6.0% (13 samples of 217), respectively. The results for the benzene exposure levels and the rates of exceeding the OEL were both statistically significant (p < 0.05). Among the 12 job categories of petrochemical workers, mechanical engineers, plumbers, welders, fieldman and scaffolding workers exhibited long-term samples that exceeded the OEL of benzene, and the rate of exceeding the OEL was statistically significant for the first two occupations (p < 0.05). CONCLUSION: These findings suggest that the periodic work environment must be assessed during non-routine works such as TA.

A novel method for low load friction testing on living cells.

A low load tribology technique for studying the effects of friction on living cells was developed. Results show a direct relationship between the coefficient of friction (COF) and the extent of cell damage. The COF, mu, for a glass pin on an intact layer of human corneal epithelial cells is determined to be on the order of mu = 0.05 +/- 0.02 (n = 16). The correlations between applied normal load and extent of cell damage, as well as between number of reciprocation cycles and cell damage, are reported. It is also found that cell damage can occur when a loading force as low as 0.5 mN is applied, although the cells appear to be intact.

Evaluation of the critical stroke of an earthworm-like robot for capsule endoscopes.

Recently, the capsule endoscope has been highlighted for the patient's convenience and the possibility of application in the small intestine. However, the capsule endoscope has some limitations in obtaining an image of the digestive organ because its movement depends only on the peristaltic motion. In order to solve these problems, it is necessary to determine the locomotive mechanism of the capsule endoscope. Therefore, the present authors have already proposed an earthworm-like robot, which has a locomotive mechanism. However, this mechanism should be designed so that the earthworm-like robot has a larger stroke than the critical stroke required to perform motion inside the small intestine. In this study, therefore, not only is the modelling of the locomotive process based on a biomechanical study presented but also the movement of the earthworm-like robot in the small intestine is simulated. Through the simulation process, the variation in the critical stroke with regard to the elastic modulus of the mesentery is investigated. Finally, from an in vitro test of the proposed robot, it is found that the experimental result is very similar to that of the simulation. Consequently, the present work will provide guidelines for designing an earthworm-like robot for diagnosis of the small intestine.

Friction enhancement via micro-patterned wet elastomer adhesives on small intestinal surfaces.

A micro-pillar-based silicone rubber adhesive coated with a thin silicone oil layer is investigated in this paper for developing friction-based clamping mechanisms for robotic endoscopic microcapsules. These adhesives are shown to enhance the frictional force between the capsule and the intestinal wall by a factor of about seven over a non-patterned flat elastomer material. In this study, tests performed on fresh samples of pig small intestine are used to optimize the diameter of the micro-pillars to maximize the frictional forces. In addition, the effects of other factors such as the oil viscosity and applied normal forces are investigated. It is demonstrated that the proposed micro-pillar pattern based elastomer adhesive exhibits a maximal frictional force when the pillar diameter is 140 microm and coated silicon oil has a very high viscosity (10,000 cSt). It is also found that the frictional force of the micro-patterned adhesive increases nonlinearly in proportion to the applied normal force. These adhesives would be used as a robust attachment material for developing robotic capsule endoscopes inside intestines with clamping capability.