• Pediatric Infection and Vaccine
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• v.28 no.3
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• pp.149-159
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• 2021

Purpose: Antibiotic exposure during pregnancy may affect the fetus and newborn in many ways. This study investigated the impact of prenatal antibiotic exposure duration on neonatal outcomes in very preterm (VP) or very low birth weight (VLBW) infants. Methods: From September 2015 to December 2020, preterm infants with gestational age less than 32 weeks or with a BW less than 1,500 g who were admitted to the neonatal intensive care unit, and their mothers were enrolled. Prenatal antibiotic exposure was defined as antibiotics received by mothers before delivery, and the patients were categorized into the non-antibiotic group, short-duration (SD; ≤7 days) group, or long-duration (LD; >7 days) groups. Results: A total of 93 of 145 infants were exposed to prenatal antibiotics, among which 35 (37.6%) were in the SD group and 58 (62.4%) were in the LD group. Infants in the LD group had a significantly higher birth weight-for-gestational-age (BW/GA) Z-score than those in the non-antibiotic group, even after the adjustment for confounding factors (beta, 0.258; standard error, 0.149; P<0.001). Multivariate logistic regression analysis showed that prolonged prenatal antibiotic exposure was independently associated with death (adjusted odds ratio [aOR], 8.926; 95% confidence interval [CI], 1.482-53.775) and composite outcomes of death, necrotizing enterocolitis (NEC), and late-onset sepsis (LOS) (aOR, 2.375; 95% CI, 1.027-5.492). Conclusions: Prolonged prenatal antibiotic exposure could increase the BW/GA Z-score and the risk of death and composite outcomes of death, NEC, and LOS in VP or VLBW infants.

• Progress in Medical Physics
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• v.9 no.4
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• pp.217-225
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• 1998

In this paper, the analysis of the relation between noise induced hearing loss and noise exposure is described for the A-weighted noise levels and exposure duration. The hearing loss and sensitivity threshold shift is investigated by changing the various parameters such as the effects of aging and noise exposure. Total hearing loss is proportional to a function of exposure level based upon the integral of pressure with time. If the noise exposure term is large so that the presbycusis may be neglected, the hearing loss due to aging and noise exposure becomes the noise induced hearing loss. It is shown that exposure to excessive noise can cause temporary loss of hearing that may become permanent if the exposure is prolonged or intense. An audiogram taken from a person suffering from noise induced hearing loss will usually show the greatest loss of hearing sensitivity in the 4kHz region, which is typically the region most sensitive to damage resulting from many types of industrial noise.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.22 no.1
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• pp.9-19
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• 2012

Objectives: The aim of this study is to critically review the exposure surrogates and estimates used to associate health effects in wafer fabrication workers such as spontaneous abortion and cancer, as well as to identify the limitations of retrospective exposure assessment methods Methods: Epidemiologic and exposure-assessment studies of wafer fabrication operations in the semiconductor industry were collected. Retrospective exposure-assessment methods used in cancer risk and mortality and reproductive toxicity were reviewed. Results: Eight epidemiologic papers and two reports compared cancer risk among workers in wafer fabrication facilities in the semiconductor industry with the risk of the general population. Exposure surrogates used in those cancer studies were fabrication(vs. non-fabrication), employment duration, manufacturing eras, job title (operator vs. maintenance worker) and qualitative classifications of agents without assessing specific agent or job-specific exposure. In contrast, specific operation, job title and agents were used to classify the exposure of fabrication workers, contributing to finding a significant association with spontaneous abortion (SAB). Conclusion: Further epidemiologic studies of fabrication workers using more refined exposure assessment methods are warranted in order to examine the associations between fabrication work, environment, and specific agents with cancer risk or mortality as used in SAB epidemiologic studies.

• Journal of Microbiology and Biotechnology
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• v.17 no.7
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• pp.1139-1146
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• 2007

Cultures of Saccharomyces cerevisiae were subjected to the effect of PEF (pulse electric field) and a source of selenium. The culture period after which yeast cells were subjected to PEF treatment was optimized, as was the duration of the exposure. Optimization of the nutrient medium composition in S. cerevisiae cultures resulted in an over 1.8-fold increase in selenium accumulation with relation to cultures on the initial substrate. Optimization of the pH value and of culture duration resulted in selenium accumulation increase by approximately 78%. A significant correlation was found between the accumulation of selenium in yeast cells and its concentration in the culture substrate. The highest accumulation of selenium in the biomass of yeast, approx. $240\;{\mu}g/g$ d.m., was obtained after 15-min exposure to PEF on a 20-h culture. An approx. 50% higher content of selenium in cells was recorded, as compared with the control culture without the application of PEF.

• Environmental Mutagens and Carcinogens
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• v.19 no.2
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• pp.102-107
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• 1999

A population monitoring studies for assessing the genotoxicity of occupationally exposed mixed organic solvents to printers were performed by using the chromosome aberration assay and the cytokinesis-blocked micronucleus assay. The incidence of chromosome aberrations and micronuclei was studied in the peripheral blood lymphocytes of 51 male printers and their matched controls in Seoul area. Smoking habits and duration of employment were taken into account. The frequencies of micronucleus in peripheral lymphocytes of printers were significantly different in comparision with control subjects. Also there were significant increase in the frequencies of micronucleus by duration of exposure. The frequencies of chromosome aberrations showed no significant differences between printers and their matched controls.

• Fisheries and Aquatic Sciences
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• v.18 no.1
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• pp.65-71
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• 2015

The functional utility of a transgenic marine medaka Oryzias dancena strain carrying the red fluorescent protein (RFP) gene driven by an endogenous choriogenin H (chgH) promoter was evaluated for its ability to detect waterborne $17{\alpha}$-ethinylestradiol (EE2), a synthetic estrogen derivative. The chgH:rfp transgenic marine medaka larvae showed an age-dependent tendency in the efficiency of EE2-mediated transgene expression, in which transgenic larvae older than 6 days post-hatching displayed a more effective response in their transgene expression to EE2 than did younger hatchlings. During experimental exposures to high concentrations of EE2 (200 to 1,000 ng/L), the transgenic responses in the hatchlings were broadly dose- and duration-dependent. With exposures using lower doses of EE2 (25, 50 and 100 ng/L), EE2-induced transgenic RFP was also observed in the transgenic larvae, although the lower doses required exposure of longer duration. Under the EE2 exposure and microscope assay conditions used in our study, transgenic marine medaka larvae exhibited a similar degree of EE2-mediated RFP phenotype expression at various salinity levels (0, 15 and 30 ppt).

• Archives of Pharmacal Research
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• v.28 no.5
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• pp.587-591
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• 2005

The effect of extremely low frequency (ELF,60Hz) magnetic fields (MFs) on convulsions was investigated in rats. We determined the onset arid duration of convulsions induced by bicuculline alone or by co-exposure to MFs and bicuculline. In addition, we measured the GABA concentrations in the rat brains using HPLC-ECD. MFs strengthened the convulsion induced by bicuculline (0.3, 1, and 3${\mu}g$, I.c.v.), with a shortening of the onset time, but lengthening of the duration time. Co-exposure to MFs and bicuculline decreased the GABA levels in the cortex, hippocampus and hypothalamus, whereas MFs alone reduced the level of GABA only in the hippocampus. These results suggest that the exposure to MFs may modulate bicuculline-induced convulsions due to GABA neurotransmissions in rat brains.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.28 no.3
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• pp.267-272
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• 2018

Objective: This study aimed to test the accuracy of self-reported information used in indirect estimation of pesticide exposure. Methods: To do so, self-reported values on the duration of pesticide application per day were compared with observed values. The number of days of pesticide application per year as recorded in self-administered logs was compared with recalled values. Results: It was found that participants underestimated the duration and frequency of actual pesticide use. High correlations were found between self-reported values and observed values, as well as between recalled values and recorded values. Conclusions: The reason might be that farmers unconsciously under-recall the application of pesticide since many customers prefer eco-friendly agricultural products. Farmers thought the task of applying pesticides to be essential, and this may explain why the participants in this study tended to accurately recall their pesticide-related work.

• Korean Journal of Occupational Health Nursing
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• v.6 no.1
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• pp.53-71
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• 1997

Across sectional study was performed to evaluate the chronic effects on central nerve system(CNS) of cumulative exposure of complex organic solvents, using neurobehavioral test. Subjects were 66 (male) dock yard painters of some large ship industry which is located in Ulsan. The neurobehavioral test battery used in this study was NCTB (Neurabehavioral Core Test Battery recommended by WHO(World Health Organization), which consisted of 7 items-Profile of mood states (POMS), Simple reaction time, Santa Ana dexterity test. Digit span, Digit symbol, Benton visual retention test and Pursuit aiming. The subjects were classified by 3 groups according to duration of employment(group 1 ; less than 9 years, group 2 ; 10-14 years, group 3 ; more than 15 years). The results of performance were analyzed considering of work duration, age, educational level, alcohol drinking, smoking and testing time as confounding factors. Benton visual retention test, pursuit aiming correct dot and sum of dot showed significant differences among the groups, and decreased with increasing work duration. It indicated that the mean scores of performance ability were lowering according to work duration. Besides, the tests that didn't show statistical significances but showed linear trends were depression-dejection, vigor, fatigue of POMS, slowest time of simple reaction time and digit span forward. Most of the neurobehavioral test items were correlated with age and educational level. After controlling of confounding factors-age and educational level, the results followed ; digit span backward was different significantly. Tension-anxiety, depression-dejection, anger-hostility of POMS, SD and slowest time of simple reaction time, Santa Ana dexterity test non-preferred hand, digit span forward, Benton visual retention test and pursuit aiming correct dot decreased with increasing of work duration. The correlation analysis was done in order to find out the relationship between subjective symptom and the scores of neurobehavioral core test battery. According to the results of analysis there were no items that had statistical significant relationship(p<0.05).

• Journal of Environmental Health Sciences
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• v.47 no.2
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• pp.166-174
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• 2021

Objectives: This study aimed to provide temporal Acute Exposure Guideline Levels (AEGL) for a hazardous substance as a pilot study. Methods: As one of the substances designated by the Korea Ministry of Environment as requiring preparations for potential accidents, formaldehyde was selected to estimate the AEGLs. The calculation was based on Haber's formula (Cn×t=k) using valid toxicity data (for humans/animals). A total of 96 points of AEGL levels were provided using an interval of five minutes over eight hours. Results: The AEGL-1 and 2 values were constant for the entire exposure duration at 0.9 ppm and 14 ppm, respectively. The values were obtained from clinical/animal tests, and the adaptation effect after a given exposure duration was also considered. AEGL-3 was based on animal toxicity data, and it was estimated from 127 ppm for the initial five minutes to 35 ppm for eight hours. Conclusions: More specific AEGL levels for formaldehyde could be obtained in this study using toxicity data with Haber's formula. Based on this methodology, it would be also possible to estimate AEGL levels that can be used at the scene of a chemical accident for other substances requiring preparation for potential accidents.