• Nuclear Engineering and Technology
• /
• v.53 no.5
• /
• pp.1634-1641
• /
• 2021

Exposure to gamma-rays is hazardous for humans and other living beings because of their high penetration through the materials. For this reason, shielding materials (usually lead, copper and stainless steel) are used to protect against gamma rays. This study's objective was to prepare ceramic materials for gamma radiation shielding by using different natural bentonite clays. Gamma-ray attenuation performances of the prepared shielding materials at different thicknesses were investigated and evaluated for different gamma-ray energies from different standard point gamma radiation sources (²⁵¹Am, ⁵⁷Co, ¹³⁷Cs, ⁶⁰Co, and ⁸⁸Y). The mass and linear attenuation coefficients of the prepared ceramics vary between 0.238 and 0.443 cm² g^-1 and between 0.479 and 1.06 cm^-1, respectively, depending on their thicknesses. Results showed that these materials could be prioritized because of their evidential properties of gamma radiation protection in radiation applications.

• Food Science and Industry
• /
• v.54 no.1
• /
• pp.2-10
• /
• 2021

Microplastics with a size of less than 5 mm have emerged as an important environmental and food safety issue, as they have been detected not only in marine but also in terrestrial ecosystem and drinking water. Although many studies have been conducted on the exposure of microplastics and the effects on human health, the lack of standardized experimental methods for microplastics has been reviewed as a major problem. In order to overcome this, European countries such as the Netherlands and Germany are conducting a project to develop detection methods for microplastics as well as to establish the risk assessment methodologies for microplastics. Being the microplastics suggested to have a substantially potential risk on human health, reliable risk assessments should be conducted considering the various sources of microplastics, chemical pollutants and biological factors. In addition, international standards and regulations should be applied.

• Genomics & Informatics
• /
• v.20 no.1
• /
• pp.10.1-10.15
• /
• 2022

Human exposure to pollutants has been on the rise. Thus, researchers have been focused on understanding the effect of these compounds on human health, especially on the genetic information by using various tests, among them the somatic mutation and recombination tests (SMARTs). It is a sensitive and accurate method applicable to genotoxicity analysis. Here, a comprehensive bibliometric analysis of SMART assays in genotoxicity studies was performed to assess publication trends of this field. Data were extracted from the Web of Science database and analyzed by the bibliometric tools HistCite, Biblioshiny (RStudio), VOSViewer, and CiteSpace. Results have shown an increase in the last 10 years in terms of publication. A total of 392 records were published in 96 sources mainly from Brazil, Spain, and Turkey. Research collaboration networks between countries and authors were performed. Based on document co-citation, five large research clusters were identified and analyzed. The youngest research frontier emphasized on nanoparticles. With this study, how research trends evolve over years was demonstrated. Thus, international collaboration could be enhanced, and a promising field could be developed.

• Journal of Mushroom
• /
• v.15 no.4
• /
• pp.259-263
• /
• 2017

In this study, we investigated the morphological characteristics and antioxidant ability of mushroom cultivar Lentinula edodes 'Nongjingo' fruiting bodies after exposure to various light conditions. Color differences between mushrooms treated with mixtures of LED light revealed that mushrooms displayed lighter color shades when compared to the control group (fluorescent light treated mushrooms). Redness increased and yellowness decreased after exposure to all treatments other than the fluorescent control. Measurement of growth characteristics of 'Nongjingo' fruiting bodies showed increases after exposure to all mixed LED treatments. In addition, the uniformity of fruiting bodies was higher when using LED light compared to fluorescent light. The measurement of stem diameters did not show a significant difference between the treatments, however, diameters were slightly larger with exposure to white-green LED. Moreover, stem length was longer in the mixed LED treatments when compared to those exposed to fluorescent light. Examination of the ratio of stem diameter to stem length revealed that the diameter of the stem was greater than the length. The antioxidant activity of water extracts made from Nongjingo fruiting bodies grown under mixed LED conditions was compared to those from mushrooms grown under fluorescence light conditions. The highest antioxidant activity was observed from mushrooms treated with white LED; however, no significant difference was found between mushrooms exposed to white-green LED compared to white-blue LED. The treatment showed higher antioxidant ability than vitamin C. Our results confirm that treatment of white LED and white-blue LED affects the growth and antioxidant ability of Nongjingo mushroom fruiting bodies.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.27 no.1
• /
• pp.38-45
• /
• 2017

Objectives: Radon may be second only to smoking as a cause of lung cancer. Radon is a colorless, tasteless radioactive gas that is formed via the radioactive decay of radium. Therefore, radon levels can build up based on the amount of radium contained in construction materials such as phospho-gypsum board or when ventilation rates are low. This study provides our findings from evaluation of radon gas at facilities and offices in an industrial complex. Methods: We evaluated the office rooms and processes of 12 manufacturing factories from May 14, 2014 to September 23, 2014. Short-term data were measured by using real-time monitoring detectors(Model 1030, Sun Nuclear Co., USA) indoors in the office buildings. The radon measurements were recorded at 30-minute intervals over approximately 48 hours. The limit of detection of this instrument is $3.7Bq/m^3$. Also, long-term data were measured by using ${\alpha}-track$ radon detectors(${\alpha}-track$, Rn-tech Co., Korea) in the office and factory buildings. Our detectors were exposed for over 90 days, resulting in a minimum detectable concentration of $7.4Bq/m^3$. Detectors were placed 150-220 cm above the floor. Results: Radon concentrations averaged $20.6{\pm}17.0Bq/m^3$($3.7-115.8Bq/m^3$) in the overall area. The monthly mean concentration of radon by building materials were in the order of gypsum>concrete>cement. Radon concentrations were measured using ${\alpha}-track$ in parallel with direct-reading radon detectors and the two metric methods for radon monitoring were compared. A t-test for the two sampling methods showed that there is no difference between the average radon concentrations(p<0.05). Most of the office buildings did not have central air-conditioning, but several rooms had window- or ceiling-mounted units. Employees could also open windows. The first, second and third floors were used mainly for office work. Conclusions: Radon levels measured during this assessment in the office rooms of buildings and processes in factories were well below the ICRP reference level of $1,000Bq/m^3$ for workplaces and also below the lower USEPA residential guideline of $148Bq/m^3$. The range of indoor annual effective dose due to radon exposure for workers working in the office and factory buildings was 0.01 to 1.45 mSv/yr. Construction materials such as phospho-gypsum board, concrete and cement were the main emission sources for workers' exposure.

• Journal of Life Science
• /
• v.31 no.4
• /
• pp.442-451
• /
• 2021

Microplastics are fragments of any type of plastic with a size less than 5 mm. Ocean pollution by microplastics is now a worldwide concern in relation to marine ecosystems and human health. The widespread contamination by microplastics means that they can be ingested by and accumulated in diverse species of wildlife, such as fish, mussels, oysters, clams, and scallops. Once ingested, the microplastics can be observed in the intestines, liver, and kidney, and even in the brain. Seafood is one of the major sources of protein intake in humans; therefore, seafood consumption could be pathway for human microplastics exposure. Accumulating evidence indicates that repeated oral exposure to microplastics induces pathologic and functional changes in the reproductive, cardiac, gastrointestinal, endocrine, and even nervous systems of rodents. Maternal exposure to microplastics during gestation and lactation alters metabolic homeostasis in the offspring. Given that seafood provides more than 20% of the total protein intake by over 310 million people worldwide, a reasonable assumption is that microplastics could be substantially accumulated in the human body and impair physiological function. In this review, we have summarized the current status of microplastics contamination in the ocean, their accumulation and toxicities in marine animals and rodents, their exposure to humans, and their potential impacts on human health.

• Information Systems Review
• /
• v.25 no.2
• /
• pp.205-227
• /
• 2023

Recently, Virtual Human(VH) has begun to appear in various media, not only on social media, but also in advertisements, music sources, and dramas. Virtual human has become a primary marketing tool for companies, but there also exist concerns when the companies do not disclose the identities of virtual humans. Accordingly, it is necessary to examine users' responses toward content that features virtual humans. This study aimed to examine how the exposure of virtual humans in the content affects users' perceptions. Therefore, the study defined the concept of 'VH Disclosure(VHD)', referring to the exposure of the virtual human's identity, and explored the impact of VH disclosure on attitude toward the ad (Hedonism, Utilitarianism, and Interestingness) and source credibility (Trustworthiness and Expertise). The study conducted an experimental survey with 302 respondents. Regardless of when the ad featured a VH or a human, the results showed that there was no significant difference between users' attitudes and source credibility. The results revealed that it was more effective to disclose the VH in social media feeds than directly reveal the VH's identity in the content. Therefore, this study utilizes a new concept of 'VH Disclosure(VHD)' to enhance the understanding of VH and contributes to establishing marketing strategies optimized for consumers in the creation of virtual human-related content.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.32 no.4
• /
• pp.611-619
• /
• 2005

The aim of this study was to apply the quantitative light-induced fluorescence(QLF) and use of fluorescein-enhanced QLF method for quantitative assessment of early enamel demineralization in vitro, comparing effectiveness of light sources : argon laser, halogen lamp, light emitting diode (LED) and plasma arc lamp. Sixty extracted teeth were used, prepared by gentle pumicing and coating in an acid-resistant nail-varnish, except for an exposure to a demineralizing solution. Teeth were removed at regular intervals (24, 48 and 72hrs), air-dried and QLF image were taken. Mineral loss, as measured by difference of optical density, was recorded. For dyeenhanced QLF a 0.075% sodium fluorescein dye was applied after QLF examination and mineral loss was recorded. The following result were obtained : 1. Comparing with mean difference of optical density, plasma arc lamp was higher than other light sources in all group (p<0.05). 2. Comparing each group with mean difference of optical density, there was significant different using plasma are lamp and halogen lamp. 3. For use of dye-enhanced QLF, comparing with mean difference of optical density, plasma arc lamp were higher than other light sources in all group(p<0.05). 4. With this model dye-enhanced QLF compared with QLF in optical density, dye-enhanced QLF was higher than QLF in optical density. From the results presented in this paper, it was concluded that plasma light source was more effective compared with other light source for the detection and the quantification of early enamel caries.

• Journal of Korean Society for Atmospheric Environment
• /
• v.24 no.1
• /
• pp.72-82
• /
• 2008

Benzene is a very harmful and toxic compound known as human carcinogen by all routes of exposure. Owing to the risky feature of benzene, several countries such as Japan, UK and EU have established the ambient air quality standard and protect from that risk of it. Korea also has designated it as one of the criteria air pollutants and established the concentration limit ($5\;{\mu}g/m^3$) in the air and is going to apply the standard from 2010. Benzene is emitted from various sources such as combustion plants, production processes, waste treatment facilities and also automobiles. Mobile source is known as one of the major emission sources of benzene. In this study, we estimated the domestic emissions of benzene from mobile source and compared the results with those of advanced countries. Mobile source was divided into 2 categories, Le., on-road source and non-road source. The total emissions of benzene from mobile source were estimated as 3,106 tons/yr and 1,612 tons/yr was emitted from on-road source and 1,494 tons/yr was from non-road source. Emission ratio of benzene from on-road source showed that 80.0% was from passenger cars, 10.1% was from taxis, 7.2% was from light-duty vehicles, 2.5% was from heavy-duty vehicles and 0.2% was from buses. In the case of non-road source, the distribution showed that 66.3% was from construction machineries, 14.5% was from locomotives, 11.7% was from ships, 7.1% was from agriculture equipments and 0.5% was from aircrafts. The cold-start emissions were estimated as 942 tons/yr and this value was almost 1.5 times greater than that for hot engine emissions (608 tons/yr). In addition, the fuel-based distribution was 65.9%, 31.1% and 2.8% from gasoline, LPG and diesel vehicles, respectively. The emission ratio from mobile source occupied 65% and 30% of total benzene emissions in USA and UK, respectively. In case of Korea, the emission ratio of benzene from mobile source occupied 29% (15% from on-road source, 14% from non-road source) which showed similar value with UK.

• Journal of Preventive Medicine and Public Health
• /
• v.10 no.1
• /
• pp.94-101
• /
• 1977

Noise pollution, both in the environment and in the workplace, has been recognized as a major health hazard -one that can impair not only a person's hearing but also his physical and mental well-being. As industrialization progresses, the prevalence rate of occupational diseases is increasing, especially hearing loss, which has the highest prevalence rate among the occupational diseases. The major cause of noise is the construction of various large industries without any regulation of noise sources. Therefor, we must establish an enactment to control mechanical noise sources. as soon as possible. For the purpose of controlling the noise source, we must have exact data about such things as the sound level, the frequency of the peak sound and the revolutions per minute (r.p.m.) of the machine (a measure of the power of its motor). This study was undertaken in order to define the noise characteristics, the power of the machine's motor, the change of the sound level and the peak sound as the r.p.m. increases, and the permissible exposure time. The sample size of this study was 74 machines at 11 plants in 6 industries. The results are as follows; 1. The breakdown of the types of mechanical noise noted was : 63.6% continuous normal sound, 26.9% intermittent sound, 4.7% continuous repeating sound and 4.6% impulsive sound. 2. With respect to the type of industry, the overall sound level was the highest in the mechanical industry, with $103.8{\pm}2.8dB(A)$, and lowest in the textile industry, with $89.2{\pm}1.43dB(A)$. 3. With respect to the type of machine, the highest sound level was 124 dB(A) caused by Gauzing(II), in the mechanical industry, and the lowest was 76 dB(A) caused by Attachment (Jup Chack) (I) in the timber industry. 4. The shortest permissible exposure time to Gauzing(II) in the mechanical industry was less than 15 minutes. 5. Among 74 machines, 68.2% of the peak sound was situated in the high frequency range (52.7% at 2 KHz, 4.1% at 4 KHz and 1.4% at 8 KHz). 41.8% of the peak sound was in the middle frequency range (4.1% at 250Hz, 14.8% at 500Hz and 22.9% at 1KHz). 6. If one machine had two motors or more, the peak sound was shifted to the low frequency range. 7. As the r.p.m. increased, the overall and peak sound levels were increased without any change of the frequency of the peak sound. 8. Whenever the machines had the same kind and the same r.p.m., the overall and peak sounds were changed by the physicochemical characteristics of the raw materials and the management.