Occupational Exposure to Refractory Ceramic Fibers in the Semiconductor Scrubber Manufacturing Industry.

Background: Refractory ceramic fibers (RCFs) are a suspected carcinogen but have been widely used as insulations. Depending on the temperature, RCFs can transform into crystalline SiO2, which is a carcinogen that can be present in the air during bulk RCF handling. This study analyzed the physicochemical and morphological characteristics of RCFs at high temperatures and determined the exposure levels during the semiconductor scrubber maintenance. Methods: Sampling was conducted at a company that manufactures semiconductor scrubbers using RCFs as insulation. Bulk RCF samples were collected both before and after exposure to a scrubber temperature of 700°C. Airborne RCFs were collected during scrubber maintenance, and their characteristics were analyzed using microscopes. Results: The components of bulk RCFs were SiO2 and Al2O3, having an amorphous structure. Airborne RCFs were morphologically different from bulk RCFs in size, which could negatively affect maintenance workers' health. 58% of airborne RCFs correspond to the size of thoracic and respirable fibers. RCFs did not crystallize at high temperatures. The exposure caused by airborne RCFs during the scrubber frame assembly and insulation replacement was higher than the occupational exposure limit. Conclusion: Workers conducting insulation replacement are likely exposed to airborne RCFs above safe exposure limits. As RCFs are suspected carcinogens, this exposure should be minimized through prevention and precautionary procedures.

Behavioral characteristics of polyhexamethyleneguanidine (PHMG) particles in aqueous solution and air when sprayed into an ultrasonic humidifier.

Polyhexamethyleneguanidine (PHMG) is widely used as a disinfectant to prevent microbial contamination in ultrasonic humidifiers in Korea; however, sales have been prohibited by the government after an outbreak of severe lung injury among humidifier disinfectant users. This study was therefore conducted to determine the characteristics of PHMG particles in aqueous solution and to investigate the behavior of airborne particles generated when using PHMG as a humidifier disinfectant. Three types of PHMG were selected (manufactured in Korea, USA, and China), with dynamic light scattering (DLS) used to determine their behavioral characteristics in aqueous solution. To determine the airborne behavioral characteristics, PHMG was diluted to obtain high (62.5-65 ppm) and low (6.25-6.5 ppm) concentrations, and then real-time monitoring instruments were used to measure the effect of using a diffusion dryer and thermodenuder to control moisture in a cleanroom. A polycarbonate filter sample was analyzed by field emission-scanning electron microscope-energy dispersive spectrometry (FE-SEM-EDS) to determine the particle morphology. The DLS intensity results for the three products showed a slightly right-shifted (~100 nm) bimodal distribution relative to the airborne particle size distribution. The size of the airborne PHMG particles increased during the spraying due to aggregation, with the particle size of aggregated particles confirmed by FE-SEM to be approximately 20 nm or more. As the PHMG concentration increased by 10 times, the airborne concentrations measured by the real-time monitoring instrument increased by 2-3 times for nanoparticles, and by 45-85 times for 1-10 µm particles during humidifier operation; however, 99% of the particles generated could be classified as PM1. Without ventilation, even after operating the humidifier, the PHMG particles could be airborne for about 2 h until the background concentration was reached. Therefore, we found that the airborne behavior was affected by PHMG concentration. Products from different manufacturers had no effect on the airborne behavior.

Atrial Septal Defect Revealed by Repeat Echocardiography in a Brain-Dead Donor: A Case Report.

BACKGROUND: The number of patients undergoing heart transplantation is limited because of the shortage of donor hearts. Expanding the donor pool with precise evaluation of donor heart is the most practical way to increase the number of patients undergoing heart transplantation. However, echocardiographic evaluation of especially right ventricle (RV) in brain-dead donors is challenging. Repeated echocardiography with volume overload may reveal unrecognized congenital heart disease such as atrial septal defect (ASD). MATERIALS AND METHODS: A case of repeated echocardiography revealed ASD secundum in a donor with significant RV enlargement and dysfunction from previously unknown origin. An almost-discarded donor heart was used in heart transplantation after simple patch closure. RESULTS: The patient was discharged after a month. One year later, he has been doing well without significant adverse events. CONCLUSIONS: RV dysfunction prior to heart transplantation increases the risk of post-transplant graft failure. Secundum-type ASD and ventricular septal defect, which are relatively common adult congenital heart diseases that cause RV enlargement and dysfunction, are not contraindications for heart transplantation. Our case showed that repeat echocardiography revealed congenital heart disease and rescued the almost-discarded heart. This simple maneuver is essential in donor heart evaluation to maximize the utility of marginal donors.