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.

Working hours and depressive symptoms: the role of job stress factors.

BACKGROUND: South Korea is one of the countries with the longest working hours in the OECD countries. The aim of this study was to evaluate the effect of working hours on depressive symptoms and the role of job stress factors between the two variables among employees in South Korea. METHODS: This study used data from the Korea Working Conditions Survey in 2014. Study subjects included 23,197 employees aged 19 years or older who work more than 35 h per week. Working hours were categorized into 35-39, 40, 41-52, 53-68, and more than 68 h per week. Depressive symptoms were assessed using the WHO's Well-Being Index with a cut-off score of 13. We calculated prevalence ratios of depressive symptoms according to working hours using log-binomial regression. Through the percentage change in prevalence ratios, we identified the extent of the role of job stress factors that explain depressive symptoms. RESULTS: The risks of depressive symptoms were significantly higher in people who worked 35-39 h per week (PR: 1.09, CI: 1.01-1.18), 53-68 h/week (PR: 1.21, CI: 1.16-1.25), and more than 68 h/week (PR: 1.14, CI: 1.07-1.21) than 40 h/week, after adjusting for confounding variables. Job stress explained the effects of long working hours on depressive symptoms in about 20-40% of the groups working more than 40 h/week. Among the factors of job stress, social support was 10-30%, which showed the highest explanatory power in all working hours. Reward explained 15-30% in the more than 52 h working group, and reward was the most important factor in the working group that exceeded 68 h. CONCLUSIONS: We showed the working hours could be an independent risk factor for depressive symptoms in employees. To improve workers' mental health, it is important to strengthen social support in the workplace, to provide adequate rewards as they work, and ultimately to regulate the appropriate amount of working hours.

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.

Combined silicosis and mixed dust pneumoconiosis with rapid progression: A case report and literature review.

BACKGROUND: Rapidly progressive pneumoconiosis (RPP) occasionally occurs in coal workers, particularly those with high exposure to silica. Here, we report the case of a 64-year-old male miller with RPP. CASE SUMMARY: The patient had a persistent cough for one month and had been clinically diagnosed with pulmonary tuberculosis in 2011. He worked in a stone processing factory from the ages of 20 through 37 and has owned his own mill for the past 25 years. His chest radiograph showed significant increases in the size and number of lung nodules since his last follow-up in 2013. By percutaneous needle lung biopsy, the nodular lesions showed diffuse infiltration of phagocytic macrophages and birefringent crystals by polarizing microscopy. He was finally diagnosed with RPP of mixed dust pneumoconiosis combined with silicosis. CONCLUSION: In this case, mixed dust pneumoconiosis with silicosis might be accelerated by persistent exposure to grain dust from working in a mill environment.

The relationship between shift work and mental health among electronics workers in South Korea: A cross-sectional study.

OBJECTIVE: To determine the relationship between shift work and mental health, particularly insomnia, depression, and suicidal ideation, among electronics production workers. METHODS: A survey was conducted with 14,226 workers from an electronics manufacturer in South Korea. After excluding 112 individuals with incomplete responses, 14,114 respondents were analyzed. As part of a larger project, we collected data on respondents' general characteristics, work-related characteristics, and health status; however, in this study, we focused on the data related to shift work and mental health. Insomnia, depression, and suicidal ideation were set as dependent variables and working schedule as set as the independent variable. We performed multiple logistic regression analysis with daytime workers as the reference group. The model was adjusted for age, gender, body mass index, workplace, educational level, and marital status with or without children under 6 years of age. RESULTS: Relative to daytime workers, shift workers had 2.35, 1.23, and 1.17 greater odds of insomnia, depression, and suicidal ideation, respectively. Within the shift worker group, we found that the odds of depression and suicidal ideation increased dramatically when respondents had insomnia. The ORs for depression and suicidal ideation were 4.899 and 7.934, respectively. CONCLUSIONS: Our findings suggest that shift work is related to an increased risk of mental health problems in production workers, and the sleep disturbance related with shift work is a central mechanism for this relationship. Since these results suggest that proactive management of sleep problems might attenuate their detrimental effects on shift worker's mental health.

Toxicity of Methylcyclohexane and Its Effect on the Reproductive System in SD Rats.

OBJECTIVES: There is limited data regarding the toxicity of methylcyclohexane, despite its wide use in rubber adhesives, paint diluents, and cleansing agents. This study aimed to verify the toxicity and influence on the reproductive system of methylcyclohexane after its repeated injection in Sprague Dawley (SD) rats. METHODS: Methylcyclohexane was injected subcutaneously into male and female SD rats once a day, five times a week, for 13 weeks at different doses (0, 10, 100, and 1,000 mg/kg/day) for each group. The toxicity of testing material was verified by observing the change in body and organ weight, hematological change, pathological findings, and effect on the reproductive system at each different concentration. RESULTS: In the 1,000 mg/kg/day group, there were cases of animal deaths. In animals that survived, hematological changes, including a decrease in the red blood cell count, were observed. A considerable weight gain or loss and pathological abnormalities in the liver, kidney, and other organs were found. However, the 10 and 100 mg/kg/day groups did not cause deaths or other specific abnormalities. In terms of reproductive toxicity, there were changes in hormone levels, including a significant decrease in hormones such as estradiol and progesterone (p < 0.001) in male animals. Menstrual cycle change for female animals did not show concentration dependency. CONCLUSION: When injected repeatedly for 13 weeks, methylcyclohexane proved to be toxic for the liver, heart, and kidney at a high dose. The absolute toxic dose was 1,000 mg/kg/day, while the no observed adverse effect level was less than 100 mg/kg/day. The substance exerted little influence on the reproductive system.