Hyunjoo Kim

Reproductive toxicity of 2-bromopropane in Sprague Dawley rats

OBJECTIVES In an effort to clarify the mass intoxication of workers at an electronic company in Korea, the possible causative chemical for reproductive toxicity, 2-bromopropane (2BP), was investigated. METHODS 2BP was tested through the use of repeated dose experiments among male Sprague Dawley rats. Ten rats were assigned to each treatment group. Vehicle control olive oil and 2BP concentrations of 125 mg/kg, 250 mg/kg, and 500 mg/kg were injected into the intraperitoneum on 28 consecutive days. RESULTS The rats showed significant decreases in body weight depending on the 2BP dose. The right and left testes showed typical weight loss depending on the dose of 2BP. The red blood cells, hemoglobin, and hematocrit showed some degree of decline with the high dose. The amount of hemoglobin, the mean platelet volume, the number of white blood cells, and the number of lymphocytes decreased significantly with the high dose, while the number of granulocytes and monocytes had a tendency to decrease depending on the dose of 2BP. The histopathology of the testes treated with the middle and high 2BP dose showed a typical patch appearance with severely depleted atrophic tubules, exhibiting germ cell necrosis of spermatogonia and spermatocytes in the seminiferous tubules. Leydig cell hyperplasia or hypertrophy in the interstitial tissue was also noticeable. The epididymis showed some degree of atrophy with vacuolization of the epididymal epithelium. CONCLUSIONS The testes are the main target organs tested for 2BP toxicity. 2BP also affect the hematopoietic system and thus induces leukopenia and normocytic anemia. Besides the reproductive organs and the hematopoietic system, no significant toxicity has been found.

Working Hours and Depressive Symptomatology among Full-Time Employees: Results from the Fourth Korean National Health and Nutrition Examination Survey (2007-2009)

OBJECTIVE This study aimed to examine the distribution of working hours and the association between working hours and depressive symptomatology using representative data from a national, population-based survey. METHOD Data came from the fourth Korean National Health and Nutrition Examination Survey (2007-2009), which employed a systematic, stratified cluster-sampling method. We used logistic regression procedures to estimate the importance of weekly working hours as a predictor of depressive symptomatology. RESULTS The prevalence of depressive symptomatology was 10.2%. The work week, which averaged 48.3 hours for the sample as a whole, was longer for men (49.8 hours) than women (45.3 hours), and 12.1% of respondents were engaged in shift work. In logistic regression analyses, compared to those working < 52 hours per week, the odds ratios (OR) of working hours as a predictor of depressive symptomatology were 1.19 [95% confidence interval (95% CI) 0.77-1.85] for those working 52-59 hours per week and 1.62 (95% CI 1.20-2.18) for those working ≥ 60 hours per week, after adjustment for demographic characteristics, health behaviors, socioeconomic status, employment status, and work schedules. It showed a positive dose-response relationship between working hours and depressive symptomatology (P = 0.0059). CONCLUSIONS Working hours in Korea are long. There is an association between working hours and depressive symptomatology, and there seems be a trend in working hours and depressive symptomatology.

Relationship between prolonged standing and symptoms of varicose veins and nocturnal leg cramps among women and men

The relationships between occupational characteristics and symptoms of varicose veins and nocturnal leg cramps and their gender differences were explored in a Korean population. The study population was 2165 workers from various occupations (55.6% female). Multiple logistic regression analyses were conducted to reveal factors related to symptoms of varicose veins and nocturnal leg cramps. The prevalence of varicose veins and nocturnal leg cramps was higher among women than men. The characteristics of standing work were different according to gender. In gender stratified analysis, the odds ratio of varicose veins was significantly high for prolonged standing for male and female workers. However, the odds ratio of nocturnal leg cramps was only significant among prolonged standing male workers. The models including gender, prolonged standing and occupations in this order presented that gender is not significantly associated with varicose veins after occupations were added to the model. Prolonged standing at work may be a more important risk factor for varicose veins and nocturnal leg cramps than biological differences between women and men. Therefore, effective interventions to interrupt or reduce prolonged standing at work should be implemented for the prevention of varicose veins and nocturnal leg cramps. Practitioner Summary: This paper shows associations between occupational characteristics and symptoms of varicose veins and nocturnal leg cramps and their gender differences. These findings will contribute to knowledge of gender-specific occupational risk factors for symptoms in the distal lower extremities.

Ergonomics Job Hazard Evaluation of Building Cleaners

Objective: The objective of this study was to evaluate a work of building cleaners using the ergonomic methods. Background: Previous studies about cleaning worker describe typical physical demands of this work. They found that the most significant risk factors associated with the physical work of cleaners are static loads and repetitive movements and high output of force. Method: A head of ergonomics estimation was work analysis(define of combined task, work tool, work time and frequency of combined task) and posture analysis of worker. Results: The results showed that combined task of building cleaners was classification sweeping, mopping(wet), mopping(oil), moving barrels/carts, dumping trash bags, scrubbing, arrangement of cleaning tool, arrangement of circumferential, moving of cleaning tool, and waiting. The work time of combined task such as mopping(wet) and scrubbing indicated high ratio. The posture analysis of building cleaners indicated high value in bending of the head, lower arm, and hands. Conclusion: The findings appear to indicate that building cleaner were related to high risk of work-related musculoskeletal disorders. So, building cleaner would be required an interventional strategy, improvement of cleaning tools and working environment. Application: If ergonomics rule can be integrated into existing cleaning tools and work environments, the risk of occupational injuries will be reduced.

Study on the Health Status of the Residents near Military Airbases in Pyeongtaek City

OBJECTIVES We conducted an epidemiologic survey to evaluate the effect of the aircraft noise exposure on the health of the residents near the military airbases in Pyeongtaek City. METHODS The evaluation of environmental noise level, questionnaire survey, and health examination were performed for 917 residents. The study population consisted of four groups: subjects who lived in the village close to the fighter airbase (high exposure), subjects who lived along the course of fighters (intermediate exposure), and subjects near a helicopter airbase, and the control group. RESULTS The prevalence of the aircraft noise related accident and irritable bowel syndrome in the exposure groups were higher than that of the control group. The risks of noise induced hearing loss, hypertension and diabetes mellitus were higher in the exposed groups than in the control group. The prevalence of anxiety disorder and primary insomnia were higher in the exposed groups than in the control group. Prevalence odd ratios of the risk for primary insomnia after adjusting age, sex, agricultural noise, and occupation were 4.03 [95% confidence interval (95% CI) 1.56-10.47] for the subject near the helicopter airbase, 1.23 (95% CI 0.40-3.76) for those intermediately exposed to fighter noise, and 4.99 (95% CI 2.14-11.64) for those highly exposed to fighter noise. CONCLUSIONS The results of the present study suggest that the aircraft noise may have adverse effects on hearing function, cardiovascular health and mental health. Therefore, it seems to be needed to take proper measures including the control of the aircraft noise and the management of the exposed peoples health.

Circadian Rhythm of Wrist Temperature among Shift Workers in South Korea: A Prospective Observational Study

Background: Human body temperature varies with circadian rhythm. To determine the effect of shift work on the circadian rhythm of the distal-skin temperature, wrist temperatures were measured. Methods: Wrist-skin temperatures were measured by an iButton® Temperature Logger. It was measured every 3 min for two and eight consecutive working days in the day and shift workers, respectively. Mesor, amplitude, and acrophase were measured by Cosinor analysis. Results: The shift-worker amplitude dropped significantly as the night shift progressed (0.92 to 0.85 °C), dropped further during rest (0.69 °C), and rose during the morning-shift days (0.82 °C). Day workers still had higher amplitudes (0.93 °C) than the morning-shift workers. The acrophase was delayed during the four night-shift days, then advanced during rest days and the morning-shift days. Nevertheless, the morning-shift worker acrophase was still significantly delayed compared to the day workers (08:03 a.m. vs. 04:11 a.m.). Conclusions: The further reduction of wrist-temperature amplitude during rest after the night shift may be due to the signal circadian rhythm disruption. Reduced amplitudes have been reported to be associated with intolerance to shift work. The findings of our study may help to design the most desirable schedule for shift workers.

The Change of Self-Rated Health According to Working Hours for Two Years by Gender

Objective: The aim of this study was to confirm the association between working hours and self-rated health, and to find the degree of changes in health level by working hours according to gender. Methods: This study was based on the 929 workers (571 men and 358 women) from the Korean Labor and Income Panel Study during 2004–2006. To minimize the healthy worker effects, the study subjects included only those who did not have any chronic diseases, and who answered their health status as “moderate” or above in the baseline. Logistic regression analysis was used to confirm the associations between working hours and self-rated health. Results: In men, working hours per week of 47–52 h, 53–68 h, and >68 h were associated with 1.2, 1.3, and 1.1 times increases, respectively, in the odds ratio on worsened self-rated health, compared with the reference group (40–46 h). On the other hand, the risks were 1.0, 2.2, and 2.6 times increases in women. However, the results were different according to gender in the group with less than 40 h. The men with less than 40 h had a 0.9 times odds ratio on worsened self-rated health. For the women with less than 40 h, the odds ratio on self-rated health was 5.4 times higher than the reference group. Conclusions: Working more than 52 h per week had a negative effect on health, regardless of gender. However, in the group with less than 40 h, the negative association between working hours and self-rated health were shown only in women. Health outcomes due to working hours may differ by gender. Therefore, further studies are needed to explore the causes of these results.

Toxic Effects of Methanol among Illegally Dispatched Workers at Aluminum CNC Cutting Process in Small-Scale, Third-Tier Subcontractor Factories of Smartphone Manufacturers in the Republic of Korea

An outbreak of occupational methanol poisoning occurred in small-scale, third-tier factories of large-scale smartphone manufacturers in the Republic of Korea in 2016. To investigate the working environment and the health effects of methanol exposure among co-workers in the methanol poisoning cases, we performed a cross-sectional study on 155 workers at five aluminum Computerized Numerical Control (CNC) cutting factories. Gas chromatography measured air and urinary methanol concentration. In the medical examination, symptom surveys, ophthalmological examinations, and neurobehavioral tests were done. Multiple logistic regression analyses controlling for age and sex were conducted to reveal the association of employment duration with symptoms. Air concentrations of methanol in factory A and E ranged from 228.5 to 2220.0 ppm. Mean urinary methanol concentrations of the workers in each factory were from 3.5 mg/L up to 91.2 mg/L. The odds ratios for symptoms of deteriorating vision and central nervous system (CNS) increased according to the employment duration after adjusting for age and sex. Four cases with an injured optic nerve and two cases with decreased neurobehavioral function were founded among co-workers of the victims. This study showed that the methanol exposure under poor environmental control not only produces eye and CNS symptoms but also affects neurobehavioral function and the optic nerve. The role of subcontracting production and dispatched work under poor environmental control was discussed.

Associations of Shift Work and Its Duration with Work-Related Injury among Electronics Factory Workers in South Korea

This study aimed to explore the association between shift work and work-related injuries. We collected data on workers from an electronics factory. This cross-sectional study included 13,610 subjects, who were assessed based on a self-reported questionnaire about their shift work experiences, work-related injuries, and other covariates. Multiple logistic regression models were used to evaluate the associations between shift work and work-related injuries and were estimated using the odds ratio. We found that the current and past shift workers, compared to non-shift workers, were associated with a 2.7- and 1.7-fold higher risk of work-related injury. There was a dose-response relationship between shift work duration and work-related injury among current female shift workers. Shift work increased the risk of work-related injuries, and the impact could be different depending on gender.

Analysis of Task and Postures of Retail Grocery Store Workers

This study was aiming to examine work time, frequency, work environment, and postures of retail grocery store workers to evaluate the risk of musculoskeletal disorders. An ergonomic evaluation was conducted using job analysis and posture analysis. The four most time-consuming tasks were inspecting (27.4%), arranging (21.4%), cutting (17.6%), and displaying (15.6%). The height and length of the shelves evaluated in the field was inappropriate for workers. The most common posture was a standing posture with neutral back, and bent head, right upper arm, lower arms, and hands. Finally, this paper concluded that `arranging,` `cutting,` and `displaying` seemed more stressful than other operations. The result of the ergonomic evaluation would contribute to design a better workspace in ergonomics.