Firefighters are constantly exposed to harmful substances in the respiratory tract and require management measures. We comprehensively compared factors affecting the lung function of firefighters to identify management measures that can reduce the deterioration of lung function.

A cross-sectional study was conducted in 1,108 male firefighters. Subjects were surveyed with self-written questionnaires that included a history of smoking, number of workouts per week, work department, and medical history, including diseases that could affect lung function. Body mass index was calculated using an automatic body measurement instrument and body fat, body fat percentage, muscle mass, and skeletal muscle mass were measured using Inbody 770. Based on the body weight obtained from body measurements, skeletal muscle mass height-adjusted skeletal muscle index (hSMI) compared to height was determined. For lung function, forced expiratory volume in one second (FEV₁), forced vital capacity (FVC), FEV₁/FVC, and peak expiratory flow (PEF) were measured using a spirometer HI-801. Analysis of variance and independent t-tests were performed for univariate analysis of factors that could affect lung function, and multiple regression analysis was performed for multivariate analysis.

When the factors relating lung function were analyzed using regression analysis, FEV₁ was negatively correlated with age, body fat percentage, and duty year, positively with height and hSMI. FVC increased with height and hSMI, decreased with age, body fat percentage, and duty year. FEV₁/FVC was related with age, height, body fat percentage and working history. Height and muscle mass were analyzed as related factors on PEF. When the analysis was conducted on firefighters who exercised more than 3 times a week, working history had lower relation with FEV₁ and body fat percentage had no relation with FEV₁/FVC.

We suggest management measures to reduce body fat percentage and increase skeletal muscle mass to maintain lung function in firefighters.

The number of claims of Industrial Accidents Compensation Insurance (IACI) for mental illness has increased. In particular, the approval rate was higher in cases with confirmed incident circumstances such as adjustment disorder, acute stress disorder, and post-traumatic stress disorder. With increased numbers of filed IACI applications and their approval rates, the need to evaluate various work-related incidents and stressors consistently is also increasing.

In January 2015–December 2017, among the cases of industrial accidents filed for mental illness and suicide by the Korea Workers' Compensation and Welfare Service, 76 filed or approved adjustment disorder cases were included. The cases of adjustment disorder were applied in this study to the “Criteria for Recognition of Mental Disorders by Psychological Loads” established in Japan in 2011 and investigated if cases were approved/rejected consistently. Additionally, features with the greatest influence on approval/rejection were examined quantitatively.

The number of applications more than doubled from 2015 to 2017, with the approval rate rising from 66.7% to 90.6%. Among the major categories, applications of adjustment disorder related to “interpersonal relationships” were the largest number of applications. Applications related to “sexual harassment”, “interpersonal relationships”, and “accidents and experiences including fires” showed relatively higher approval rate. The approval rate was the lowest in the case of “change in the amount and quality of work”.

Approved cases tend to have special precedents and strong intensity. The main reasons for the rejection were that there were no special precedents and that the intensity of the case was weak. These 2 were the most important factors in determining approval/rejection.

Combined heat and power generation (CHP generation, also called ‘cogeneration’) is attracting public attention for its high thermal efficiency, without considering possible adverse environmental health effects.This study investigated the potential role of cogeneration plants in inducing 3 environmental diseases: asthma, allergic rhinitis, and atopic dermatitis.

From 1 January 2013 to 31 December 2017, the towns (dongs) of South Korea in which a cogeneration plant started operation were selected as study sites. For comparison, a matched control dong with the most similar Gross Regional Domestic Product for each case dong was selected. The numbers of outpatient visits, inpatient admissions, and emergency visits provided by the National Health Insurance Sharing Service (NHISS) were analyzed using an interrupted time-series design. For air pollutants, the concentrations of 5 air pollutants from the AIRKOREA dataset were used.

A total of 6 cogeneration plants in 6 case dongs started operation during the study period. For overall case dongs, the pre-CHP trend was 1.04 (95% confidence interval [CI]: 1.038–1.042), and the post-CHP trend was 1.248 (95% CI: 1.244–1.253). The intercept change due to the CHP plant was 1.15 (95% CI: 1.137–1.162). For overall control dongs, the pre-CHP trend was 1.133 (95% CI: 1.132–1.135), and the post-CHP trend was 1.065 (95% CI: 1.06–1.069). The intercept change due to the CHP plant was 0.888 (95% CI: 0.878–0.899). Only for CO and NO₂, the relative risk (RR) for overall case dongs was statistically significantly increased, and the RR for the overall control dongs was statistically insignificant.

Possible hazardous emissions, like CO and NO_2, from cogeneration plants could induce environmental diseases in nearby community populations. The emissions from cogeneration plants should be investigated regularly by a governmental agency, and the long-term health outcomes of nearby community residents should be investigated.

Several studies have reported a high prevalence of osteoarthritis (OA) of the knee among agricultural workers. We investigated work-related factors that increase the risk of knee OA among Korean farmers.

Data were extracted from the Jeonnam Center for Farmer's Safety and Health survey, conducted between 2013 and 2015. The sample included 489 farmers (man 240, woman 249). We defined knee OA as radiographic knee OA (≥ Kellgren-Lawrence grade 2) with symptoms (≥ Western Ontario and McMaster Universities Osteoarthritis, Korean version score 29.5). We considered covariates such as cumulative squatting working time (CSWT), cumulative heavy lifting working time (CLWT), body mass index (BMI), and history of knee injury. Odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) were calculated for knee OA and adjusted for relevant covariates.

The results of multivariate logistic regression analysis indicated that knee OA was correlated by factors such as sex, age, BMI, history of knee injury, CSWT, and CLWT. Particularly, CSWT > 20,000 hours (OR: 2.83; 95% CI: 1.35–5.92; reference < 10,000 hours) and CLWT > 5,000 hours (OR: 2.62; 95% CI: 1.14–6.06; reference < 2,000 hours) were associated with an increased risk of knee OA after adjustment for covariates.

Squatting posture and heavy lifting associated with farm work might increase the risk of knee OA among Korean farmers.

Farmers are often exposed to dust, molds, pollen, animal products, insects, and chemicals. Accordingly, they have a high prevalence of respiratory and allergic diseases. Some studies have shown that farmers have a high prevalence of respiratory diseases and symptoms depending on where farmers work. The objective of the present study was to investigate whether certain types of agricultural workplaces are associated with the prevalence of allergic reactions in skin prick tests (SPTs) in South Korea.

A total of 149 farmers, grouped according to their workplaces in greenhouses, poultry houses, or outdoors, answered a self-reported questionnaire about the prevalence of respiratory diseases and symptoms. They were skin-tested using 12 allergens. The questionnaire and the prevalence of positive skin tests were determined for each of the participant groups, and the results were analyzed by multivariate logistic regression.

There were significant differences in the prevalence of allergic reactions to the SPT, chronic obstructive pulmonary diseases (COPDs) and asthma symptoms (wheezing) among the subgroups. The allergic reaction to SPT was the highest in greenhouse workers (30.9%), followed by poultry house workers (15.9%), and outdoor workers (8.1%). The prevalence of COPD was 6.8% in poultry house workers alone and not in other groups. The prevalence of wheezing was the highest at 9.1% in poultry house workers. According to the results of the logistic analysis, the prevalence of allergic reactions to SPT had positive correlations with the types of workplaces. Greenhouse workers had higher risk of SPT sensitization compared to outdoor workers (adjusted odds ratio [OR]: 5.55, 95% confidence interval [CI]: 1.32–32.24). The prevalence of SPT positivity also had an association with the symptoms of sneezing, rhinorrhea, or nasal congestion (adjusted OR: 6.64, 95% CI: 2.06–23.63).

These data demonstrate that the types of workplaces were associated with the prevalence of allergic sensitization. This could be explained by the difference in the type or level of airborne exposures in each workplace. It is also likely that this was caused by differences between groups of individual factors such as age and BMI that influence SPT sensitization.

Studies have investigated the relationship between long work hours and sleep disorders; however, they have focused on shift workers or specific workers who are at high risk of industrial accidents rather than wage workers in general. The purpose of this study is to investigate the effects of long work hours on sleep disorders among non-shift daytime wage workers.

We conducted a secondary analysis of data from the 5th Korean Working Conditions Survey. From the 50,205 total participants, we included 26,522 non-shift daytime wage workers after excluding self-employed people, business owners, unpaid family employees, and wage workers who work nights and shifts. Sleep disorders were categorized into “difficulty in falling asleep,” “frequent waking,” and “waking up with fatigue.” Logistic regression analysis was used to evaluate the influence of long work hours on sleep disorders, and the odds ratios (ORs) were calculated.

The OR of working > 52 hours per week was 1.183 (95% confidence interval [CI]: 1.002–1.394) for the risk of developing insomnia compared with working ≤ 40 hours per week. The OR of waking up with fatigue was 1.531 (95% CI: 1.302–1.801). Long work hours showed no significant relationship with difficulty in falling asleep or with frequent waking.

Working for extended hours was associated with increased fatigue upon waking in non-shift daytime wage workers.

We aimed to determine relationship diabetes according to urinary phthalate metabolites using adult data from Korean National Environmental Health Survey cycle 3 (2015–2017).

This study was conducted on 3,781 adults aged 19 years and older (1,648 men and 2,133 women) based on KoNEHS cycle 3. Participants' data were analyzed by gender; Relationship between phthalate metabolites in the urine and diabetes was analyzed by dividing the sociodemographic variables, health behavior-related variables, and urinary phthalate metabolite concentrations into quartiles. To determine the relationship between urinary phthalate metabolites and the prevalence of diabetes, the odds ratio (OR) was calculated using logistic regression analysis.

Based on the 1st quartile of each metabolite, the ORs for di-2-ethylhexyl phthalate (DEHP) (4th quartile), mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) (2nd quartile, 3rd quartile and 4th quartile), mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP) (4th quartile), mono-(2-ethyl-5-carboxypentyl) phthalate (MECCP) (4th quartile), mono-n-butyl phthalate (MnBP) (3rd quartile and 4th quartile), mono-benzyl phthalate (MBzP) (2nd quartile) and 4th quartile), and mono (3-carboxypropyl) phthalate (MCPP) (3rd quartile and 4th quartile) were significantly higher after the adjustment in men. The ORs for DEHP (2nd quartile, 3rd quartile and 4th quartile), MEHHP (2nd quartile, 3rd quartile and 4th quartile), MEOHP (4th quartile), MECCP (4th quartile), MBzP (4th quartile), and MCPP (4th quartile) were significantly higher after the adjustment in women.

This study investigated relationship between urinary phthalate metabolites and diabetes. The higher urinary phthalate metabolites, the higher the prevalence of diabetes. Further regulation of phthalate may be needed, and further studies are warranted to confirm the association between phthalate concentration and other chronic diseases (such as hypertension, hyperlipidemia, and cardiovascular disease).

Job insecurity and emotional labor are poor job-related factors that are known to cause sleep disturbances in customer service workers. This study investigates the combined effect of emotional labor and job insecurity on sleep disturbance.

This study used data from the Fifth Korean Working Condition Survey and included 15,147 paid workers who serve customers below 65 years. We re-classified into 6 groups based on whether the degree of emotional labor increased (Rarely/Sometimes/Always) or whether job insecurity (No/Yes) was present. We performed propensity score matching for several covariates and calculated odds ratio (OR) and 95% confidence intervals (CIs) for sleep disturbance by logistic regression models using only matched subjects.

Workers exposed to emotional labor and job insecurity had significantly higher risk for 3 dimensions of sleep disturbance (difficulty falling asleep, waking up repeatedly during the sleep, and waking up with feeling of fatigue) (OR [95% CI]: 1.44 [1.22–1.69], 1.18 [0.99–1.40], 1.52 [1.30–1.79] for emotional labor; and 2.00 [1.75–2.29], 2.20 [1.91–2.53], 1.67 [1.45–1.92] for job insecurity). Compared to those who were exposed to both emotional labor rarely and without job insecurity, when workers had both poor job factors, the OR (95% CI) for sleep disturbance for difficulty falling asleep, waking up repeatedly during the sleep, and waking up with feeling of fatigue were 3.05 (2.42–3.86), 2.89 (2.26–3.69), and 2.60 (2.06–3.29), respectively. The relative excess risk due to Interaction of job insecurity and emotional labor was significant only for difficulty falling asleep, but not the other 2 sleep disturbance dimensions.

Customer service workers suffered from severe sleep disturbances according to the existing degree of emotional labor and job insecurity. The combined effect of both could have an additive influence on serious sleep disturbance among customer service workers.

Asbestos is a well-known hazardous substance that causes occupational and environmental diseases including asbestosis (lung fibrosis). Silica exposure which causes silicosis (another type of lung fibrosis) has long been linked to the development of autoimmune diseases; however, there are few studies on the relationship between asbestos exposure and autoimmune diseases.

A total of 54 individuals who had worked in a former asbestos textile factory underwent autoantibody-related blood tests, chest X-ray imaging, and pulmonary function tests. Based on the job exposure matrix (JEM), the estimated asbestos exposure concentrations were determined, and the presence of asbestosis was determined by chest radiography.

Scleroderma (Scl-70) and ribonucleoprotein (RNP) antibodies were significantly lowered in the pleural plaque present group than in the absent group. Additionally, Scl-70, RNP, and Sjögren's syndrome type B (SS-B) antibodies were significantly lowered in the asbestosis present group. When stratifying variables with or without asbestosis, Scl-70, Smith, SS-B, and RNP antibodies decreased in female, crocidolite handling group, and higher estimated asbestos exposure level group.

Contrary to our expectations that autoantibody titers would be higher in groups with high asbestos exposure or in the asbestosis group, those with asbestosis showed lower titers. But as our research has some methodological limitations, the lowered titer of autoimmune antibody in our asbestos exposed subjects could not be simply interpreted as a lowered risk of autoimmune diseases. So careful interpreting should be taken when examine autoantibodies to screening or diagnose autoimmune diseases in people with asbestos exposure. In addition, it is necessary to establish relevance of asbestosis and autoantibodies through further studies of larger scale and higher confidence levels.

We aimed to find the relationship between sleep duration and impaired fasting glucose according to working type in non-regular workers using the 2016 and 2017 Korean National Health And Nutrition Examination (KNHANE, 7th revision).

In the 1st and 2nd year (2016, 2017) of the 7th KNHANE, 16,277 people participated. Minors were excluded because this study was intended for individuals aged 19 years and older. As this study was based on wage workers, unemployment, self-employed workers, employers, unpaid family workers, and those who have insufficient answers such as unknown or no response were excluded. Regular workers were excluded because this study was intended for non-regular workers. Finally, a total of 2,168 people were included in the survey, except those who had been diagnosed with diabetes, had a fasting blood glucose level of 126 mg/dL or higher, or taking hypoglycemic agents or receiving insulin injections. To find the relationship between sleep duration and impaired fasting glucose according to work type in non-regular workers, multiple logistic regression analysis was performed by adjusting the general and occupational characteristics after stratification according to work type. All statistical analyses were performed using the SPSS software (version 26.0; SPSS Inc., Chicago, IL, USA).

In the case of insufficient sleep duration in irregular female workers, the odds ratio (OR) of impaired fasting glucose was statistically insignificant, but in the case of insufficient sleep duration in irregular male workers who have shift work, the odds ratio (OR) of impaired fasting glucose was significantly higher than that of sufficient sleep duration (Model 1, OR: 3.05, 95% confidence interval [CI]: 1.18–7.90; Model 2, OR: 2.81, 95% CI: 1.08–7.29).

Our findings demonstrate that insufficient sleep duration was associated with an increase in fasting blood glucose levels in non-regular male workers working shifts. This means that non-regular workers are in desperate need for adequate sleep and health care. We hope that our study will help improve the health of non-regular workers and more systematic and prospective follow-up studies will be conducted to further improve the health of non-regular workers.

Glyphosate and glufosinate use widely used as herbicide ingredients. There have been several reported cases of chemical burns caused by dermal exposure to glyphosate-containing herbicide, and patients in these cases were discharged without fatal complications. There were no cases of severe symptoms due to non-oral exposure of glufosinate-containing herbicides. Here, we report a case of fatality accompanied with severe chemical burns in an 81-year-old man who did not wash his skin for more than 48 hours after dermal exposure to herbicide containing glyphosate and glufosinate with surfactant (HGlyGluS).

An 81-year-old male with no underlying disease was admitted to the emergency department (ED). He had sprayed HGlyGluS with a manual knapsack sprayer 3 days ago and had not wash away the herbicide. On arrival, he was drowsy and had multiple severe corrosive skin lesions. Skin necrosis (10 × 15 cm) on the right shoulder and skin lesions with subcutaneous fat exposure (15 × 20 cm) on the right thigh were observed. Although he was treated including continuous renal replacement therapy, antibiotic apply, debridement operations, and so on, he was unable to recover and expired.

We suggest that prolonged dermal exposure to HGlyGluS induces fatality. Further studies including prolonged dermal exposure and ingredients of surfactants should be carried out. Also, it is necessary to educate farmers that it is very important to wash immediately after dermal exposure to pesticide.

The purpose of this study was to assess the reliability and validity of the 3-item version of the Work Engagement Scale (WES-3), which is based on the Job Demands-Resources (JD-R) model and was used in the 5^th Korean Working Conditions Survey (KWCS).

This study used data from the 5th KWCS (n = 50,205), which was conducted in 2017 with a sample of the Korean working population. The survey gathered comprehensive information on working conditions to define workforce changes and the quality of work and life. The reliability and internal consistency of the WES-3 were assessed using the corrected item-total correlation and Cronbach's alpha coefficient. Confirmatory factor analysis (CFA) was used to test the construct validity of work engagement. The convergent validity was assessed using the correlation with the WHO-5 well-being index. Correlations between work engagement and JD-R factors were also calculated.

The Cronbach's alpha for work engagement was 0.776, indicating acceptable internal consistency. The model comprising 3 work engagement and 2 burnout items showed an excellent fit (χ²: 382.05, Tucker-Lewis index: 0.984, comparative fit index: 0.994, root mean square error of approximation: 0.043). The convergent validity was significant (correlation coefficient: 0.42). Correlations with burnout and job demands were negligible, whereas correlations with job resources and job satisfaction were weakly positive.

The results of our study confirm that the WES-3 has acceptable reliability and validity.

The destruction of circadian rhythms by night shift work affects major circadian genes, which are known to play a role in advancing or killing the cell cycle through tumor suppressor genes. To find out whether night shift work affects the incidence of colorectal cancer, which was found to be associated with long-term night shift work in previous studies, we surveyed effect of night shift work on colorectal polyps that have a higher incidence than colorectal cancer and can progress to colorectal cancer.

To examine the correlation between rotating night shifts and colorectal polyps, a survey was conducted with 299 men aged 40–60 years from two university hospitals. We examined lifestyle, work history, work patterns, and colonoscopy results. The differences in prevalence among the groups was compared, and prevalence ratio (PR) was calculated via generalized linear modeling.

The prevalence of colorectal polyps in night shift and non-shift workers were 53.0% and 33.5%, respectively. After adjusting for age, smoking status, dietary habits, family history of colorectal cancer, obesity, job type, night shift work (PR: 1.13, 95% CI: 1.02–1.25) was a risk factor of colorectal polyps.

The risk of colorectal polyps was greater in night shift workers than non-shift workers. Also risk of colorectal polyp was higher in older group. Our study investigated colorectal polyp instead of colorectal cancer and lacks information about types and gene mutations of colorectal polyps. Further study is needed to clarify effect of night shift work on development of colorectal cancer.

Mental illness is known to be caused by genetic, biological, and environmental risk factors. Although previous studies have established the link between mental illness and job stress, most of them are limited to major depression disorder. Therefore, this study examined the relationship between job stress and bipolar spectrum disorder (BSD).

This is a cross-sectional study based on a survey conducted in April 2017 at an electronic parts manufacturing company in Busan. In a total of 441 workers, the degree of BSD was identified using the Korean version of the Mood Disorder Questionnaire, and the degree of job stress was identified using the Korean Occupational Stress Scale Short Form. This study also identified general characteristics of workers and job-related factors. The χ² test and Fisher's exact test was conducted to determine the differences among the variables, based on BSD. Multiple logistic regression analysis was conducted to determine the influence of independent variables on BSD.

Cross-analysis showed significant differences between the BSD high-risk and low-risk groups regarding age, sex, occupation, smoking, problem drinking, job stress total score, occupational climate, and major depression disorder symptom. In addition, the significant differences between the BSD high-risk and low-risk groups about job stress were observed in terms of job demand, job insecurity, and occupational climate. A multiple logistic regression analysis revealed that the high-risk group in the job stress group had a higher effect on BSD than the low-risk group (odds ratio [OR]: 2.32, 95% confidence interval [CI]: 1.10–4.88). Among the categories of job stress, high-risk groups in 3 areas—job demand (OR: 2.56, 95% CI: 1.27–5.17), job insecurity (OR: 4.42, 95% CI: 1.19–16.42), and occupational climate (OR: 2.55, 95% CI: 1.29–5.05)—were more likely to have an impact on BSD than the low-risk groups.

This study demonstrated that the high-risk groups of job stress total score, job demand, job insecurity, and occupational climate had a more significant effect on BSD than the low-risk groups. As workers with BSD may have difficulties in their work and personal lives, there is a need to manage job stress to prevention of BSD.

The International Agency for Research on Cancer classified 1,2-dichloropropane (1,2-DCP) as a human carcinogen in 2016. It is necessary to establish a health monitoring system for workers exposed to 1,2-DCP. We investigated the correlation between 1,2-DCP concentration in air and urine to determine whether it is appropriate to measure 1,2-DCP in urine as a biological exposure index (BEI).

Twenty-seven workers from 3 manufacturing industries handling 1,2-DCP participated in this study. Airborne 1,2-DCP was collected by personal air. Urine samples were collected at the end of work and analyzed using gas chromatography-mass spectrometry. Correlation analysis and simple regression analysis were performed to investigate the relationship between 1,2-DCP concentration in urine and air.

Pearson correlation coefficients between total 1,2-DCP in air and urine (uncorrected, creatinine-corrected) were 0.720 and 0.819, respectively. For urine samples analyzed within 2 weeks, the Spearman's rho of 1,2-DCP concentration in urine (uncorrected and creatinine-corrected) was 0.906 and 0.836, respectively. Simple regression analysis of 1,2-DCP in air and urinary 1,2-DCP concentrations within 2 weeks, which showed the highest correlation, revealed that the coefficient of determination of 1,2-DCP concentration in urine (uncorrected and creatinine-corrected) was 0.801 and 0.784, respectively.

As a BEI for workers exposed to 1,2-DCP, urinary 1,2-DCP without creatinine correction better reflects the exposure levels of 1,2-DCP in air.

Female farmers have a high prevalence of knee osteoarthritis (KOA) in South Korea. Femoral bowing has been reported to be related to KOA by increasing load on the mechanical axis. This study aimed to investigate factors related to femoral bowing in Korean female farmers.

We analyzed the legs of 264 female farmers registered with the Korea farmers' knee cohort of Jeonnam Center for Farmers' Safety and Health. A structured questionnaire was used to determine sociodemographic variables, agricultural career, cumulative squatting working time (CSWT), and cumulative heavy lifting working time. Femoral bone density was measured and Kellgren-Lawrence (KL) grades were obtained from the knee radiographs. Mechanical axis angle (MAA), femoral bowing angle (FBA), anatomical lateral distal femoral angle (aLDFA), anatomical medial proximal tibial angle (aMPTA), and condylar-plateau angle (CPA) were measured. We examined the relationship between the FBA and related factors by using multiple linear regression.

The proportion of individuals with radiographic KOA (≥ KL grade 2) in this study was 37.9%. As KL grades increased, MAA, FBA, and CPA increased, whereas aLDFA and aMPTA decreased. FBA increased with age. Multiple linear regression analyses using FBA as a dependent variable showed relationship with higher age, lower height, higher BMI, lower bone mineral density, longer CSWT, and longer agricultural careers.

The results of this study suggest that external factors related to agricultural work in female farmers was associated with femoral bowing, in addition to internal factors such as age, bone density, height, and obesity.

This study aimed to determine the effect of specific working postures on the development of varicose veins (VV). By using Korea's National Health Insurance (NHI) and National Employment Insurance (NEI) data, we analyzed the general characteristic and difference in proportions of VV cases according to occupational working posture.

From the NEI and NHI data, participant demographics, such as gender, age, body mass index, and number of workers in specific occupations or industries were obtained. We classified the 240 occupations into blue-collar (BC) and white-collar (WC) occupations and subdivided them into standing, sitting, and walking groups according to the dominant working posture.

The number of VV patients per 100,000 individuals increased with age, with a higher number of women than men and a higher number of patients in the BC than WC groups. For the BC group, the proportion of VV cases was the highest in the standing group, followed by the walking and sitting groups, but there was no significant difference between standing and walking groups in man. For the WC group, the standing group had a higher proportion of VV cases than the sitting group, but there was no significant difference between the standing and sitting group in man. In the BC group, the proportion of VV cases was the highest among medical and welfare-related elementary workers, bakers and cookie makers, automobile assemblers, cleaning and guarding-related elemental workers, and nurses and dental hygienists. In the WC group, the proportion of VV cases was the highest among food/lodging/tourism/entertainment/sports-related managers, environment/cleaning/protective services-related managers, finance and insurance clerks, accounting book-keeping clerks, and social welfare and counseling professionals.

This study was performed to determine the characteristics of VV with different working posture among Korean workers. It is expected to be the basis of further studies on occupational musculoskeletal diseases.

The concept of work-life balance (WLB) has become an important issue in workers' health and safety. This study aims to investigate the relationship between WLB and occupational injury and work-related musculoskeletal pain.

The study included 27,383 workers who participated in the Fifth Korean Working Conditions Survey. Participants were divided into good WLB and poor WLB groups based on their responses to the five question items which comprised two dimensions: work-on-life conflict (items, 1–3) and life-on-work conflict (items 4 and 5). Occupational injury and musculoskeletal pain were also assessed using the question items. The χ² test and multivariate logistic regression analyses were performed to examine the relationship of WLB to occupational injury and musculoskeletal pain while considering socio-demographic and occupational characteristics and ergonomic and psychological risk factors.

Of the 27,383 participants, 252 (0.9%) had experienced an occupational injury and 6,408 (23.4%) had musculoskeletal pain. The poor WLB group had higher injury rates for both men (1.7%) and women (0.9%) than the good WLB group (1.1% and 0.4%, respectively). Additionally, the prevalence of musculoskeletal pain was higher for both men and women in the poor WLB group (25.2% and 28.0%, respectively) than for men and women in the good WLB group (18.7% and 23.6%, respectively). In the logistic regression analysis, the adjusted odds ratio of WLB for occupational injury was 1.37 (95% confidence interval [CI]: 1.06–1.78), and that for musculoskeletal pain was 1.14 (95% CI: 1.07–1.21), showing positive associations of WLB with both occupational injury and musculoskeletal pain.

Poor WLB causes an increase in occupational injury and musculoskeletal pain. Therefore, an improvement in WLB may reduce the incidence of occupational injury and musculoskeletal pain among workers. Social and policy-related initiatives are needed to improve workers' WLB to reduce occupational injury and musculoskeletal pain.

High concentrations of mercury intake from seafood are known to cause various side effects in humans, including on the nervous system. Various studies have reported the effects of mercury concentrations in humans; however, the association between dyslipidemia, a cardiovascular disease risk factor, and mercury remains controversial. Therefore, this study aimed to investigate the association between mercury accumulation and cholesterol concentrations in a Korean population.

We analyzed data of a sample of 3,228 respondents obtained from the Korean National Environmental Health Survey cycle 3, surveyed between 2015 and 2017, to determine how lipid profiles changed according to the blood mercury concentrations (BHg) and urine mercury concentrations (UHg). Multiple regression analysis was used to determine the effects of mercury concentrations among various factors affecting blood cholesterol levels.

The arithmetic mean (AM) of BHg was 2.91 (2.81–3.02) μg/L, and the geometric mean (GM) was 2.71 (2.59–2.85) μg/L. The AM of UHg was 0.52 (0.48–0.56) μg/L, and the GM was 0.35 (0.33–0.38) μg/L. Lipid profiles were more related to the BHg than to the UHg. Total cholesterol (total-C), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) levels increased significantly as BHg increased in males, and total-C, triglyceride, and LDL-C levels increased significantly in females. Multiple regression analysis indicated that BHg were significantly associated with total-C, HDL-C, and LDL-C levels.

We found an association between mercury exposure and the risk of dyslipidemia; however, further studies are required to elucidate a causal association.

Change in working time arrangement (WTA) can be harmful to workers' sleep and health. This study aimed to investigate the association between change in working time arrangement and sleep disturbance.

This study used data from the Fifth Korean Working Condition Survey and included 33,203 paid workers. We performed a stratified analysis by sex. After dividing the participants into 6 groups based on whether or not they experienced WTA changes, and their weekly working hours (≤40, 41–52, ≥53 hours), we calculated odds ratio (OR) using the weekly working hours ≤40 hours and with no WTA change as the reference group.

Of the 33,203 paid workers, participants who experienced change in working time arrangement had higher prevalence of all three types of sleep disturbance symptoms (difficulty in falling asleep, waking up repeatedly during sleep, and waking up with a feeling of exhaustion and fatigue) in both sexes. Compared to the reference group at 95% confidence interval (CI), the group with change in WTA showed elevated OR values of 1.91 (95% CI: 1.73–2.11), 1.93 (95% CI: 1.74–2.14), 2.47 (95% CI: 2.26–2.71) for male workers; and 1.93 (95% CI: 1.73–2.16), 2.02 (95% CI: 1.80–2.27), 2.24 (95% CI: 2.01–2.50) for female workers, for difficulty in falling asleep, waking up repeatedly during the sleep, waking up with a feeling of exhaustion, and fatigue, respectively.

Workers who experience change in work time arrangement show a high risk of sleep disturbance in both sexes.

Sickness presenteeism (SP) indicates “going to work while being ill.” The importance of SP has only recently been investigated, and the association between SP and employment status has been inconsistent across studies. Therefore, we conducted this study to explore the association between SP and employment status by using presenteeism propensity (PP), which can reflect the individual decision-making process.

The study population included employees participating in the 5th Korean Working Condition Survey. We analyzed data of only employees with at least one health event, which was calculated as the sum of SP and sickness absenteeism days. Employment status was grouped into 3 categories: stable employment, unstable employment (contract period ≥ 1 year), and unstable employment (contract period < 1 year). Survey-weighted logistic regression analysis was conducted to assess the association between employment status and PP (dichotomized as “≤ 0.5” and “> 0.5”).

Unstable employees (contract period ≥ 1 year) had higher odds of PP than stable employees (odds ratio [OR]: 1.23, 95% confidence interval [CI]: 1.03–1.47), whereas unstable employees (contract period < 1 year) had lower odds of PP than stable employees (OR: 0.82, 95% CI: 0.71–0.96).

Employment status was associated with SP. Given the negative health impact of SP, social efforts, such as paid sick leave, are required to reduce SP and enhance the health status of unstable workers.

This study aimed to investigate the association between job stress and suicide ideation/attempts among display manufacturing workers.

Data were collected from 836 workers in a display manufacturing company who participated in health screenings from May 22 to June 16, 2017. The data included general characteristics, night work, job tenure, previous physician-diagnosed chronic diseases, suicidal ideation/suicide attempts, and job stress. We investigated suicidal ideation/suicide attempts that covered the past year by using a self-reported questionnaire. Job stress was measured using the 43-item Korean Occupational Stress Scale. Multiple logistic regression analysis was used to investigate the association between job stress and suicidal ideation/suicide attempts. The mediator effect of depression on suicidal ideation/suicide attempts was tested using a series of logistic regression by applying Baron and Kenny's mediation method.

In the model adjusting for variables (e.g., age, body mass index, smoking, alcohol consumption, regular exercise, shift work, job tenure, chronic disease and depression), physical environment (OR: 3.60, 95% CI: 1.08–12.02), lack of reward (OR: 5.31, 95% CI: 1.54–18.34), and occupation climate (OR: 7.36, 95% CI: 2.28–23.72) were correlated with suicidal ideation/suicide attempts in women. However, all subscales of job stress were not significantly correlated with suicidal ideation/suicide attempts in men. In mediation analysis, job instability and occupational climate were correlated with suicidal ideation/suicide attempts and were mediated by depression in men workers.

In women workers, the experiences of suicidal ideation/suicide attempts were significantly correlated with the physical environment, lack of reward, and occupational climate that were subscales of job stress. In men workers, depression rather than job stress was correlated with experiences of suicidal ideation/suicide attempts.

Sleep disorders are common and serious problems for mental health. This study investigated the relationship between spouses' weekly working hours (SWWH) and sleep problems by using the data from the 5th Korean Working Conditions Survey.

Data from 14,921 wage workers were used in the 5th Korean Working Conditions Survey. General and occupational characteristics, sleep problems are included in the questionnaire. Multivariate logistic regression analysis was used after adjustment for general and occupational characteristics to find the relationship between SWWH and sleep problems.

Compared to those whose spouses worked less than 40 hours per week, risk of trouble falling asleep, waking up repeatedly while sleeping, and waking up with a feeling of exhaustion and fatigue was significantly higher as SWWH increase among those whose spouses worked 53 or more hours per week (odds ratio [OR]: 1.40, 95% confidence interval [CI]: 1.16–1.70; OR: 1.50, 95% CI: 1.23–1.82; OR: 1.51, 95% CI: 1.24–1.83).

SWWH were related to sleep problems among Korean wage workers.

Most of the studies that have examined the association between the sub-factors of occupational stress and depressive symptoms have used cross-sectional data. However, our study has longitudinally measured the occupational stress and depressive symptoms of Korean workers of a semiconductor manufacturing company across six years to intending to investigate the associations between the sub-factors of occupational stress and depressive symptoms using longitudinal data.

Data collected from the workers of a semiconductor manufacturing company. Out of 1,013 recruited workers, 405 (40.0%) completed the survey questionnaires at 3 and 6-year follow-ups. Occupational stress was measured using a shorter version of the Korean Occupational Stress Scale (KOSS), whereas depressive symptoms were assessed using the Korean version of the Center for Epidemiological Studies-Depressive Symptoms Scale (CES-D). The data of male and female participants independently analyzed. Longitudinal associations were analyzed using panel data analysis with fixed effects.

In panel data analysis with fixed effects, job insecurity (B = 0.048, p-value = 0.004) was associated with depressive symptoms among male workers. In female workers, inadequate social support (B = 0.080, p-value < 0.001), job insecurity (B = 0.039, p-value = 0.004), lack of reward (B = 0.059, p-value = 0.004) and discomfort in occupational climate (B = 0.074, p-value < 0.001) were associated with depressive symptoms among female workers.

Temporal changes in the sub-factors of occupational stress were associated with changes in depressive symptoms within the same period. There was a gender difference in occupational stress sub-factors related to depressive symptoms.

There have been no health-related studies of pre-employed firefighters without firefighter-specific job-related factors (FSJRF). This study aimed to evaluate the sleep quality of pre-employed firefighters and to examine the relationship between sleep quality and psychosocial factors.

We conducted a self-report questionnaire survey for 602 pre-employed firefighters at 3 Fire Service Academies after brief lecture about sleep. Sleep quality and psychosocial variables such as depression, anxiety, stress and social support were evaluated. The independent 2 sample t-test, χ² test and multiple logistic regression analysis were used to evaluate the effect of the variables on the sleep quality of pre-employed firefighters.

Among a total of 602 people, 347 (57.6%) had good sleep quality and 255 (42.4%) had poor sleep quality. Pittsburgh Sleep Quality Index score of them was 3.29 ± 1.41) and 7.87 ± 2.20), respectively. 24 (4.0%) were evaluated to have insomnia by Insomnia Severity Index. Logistic regression analyses showed that the depression (adjusted odds ratio [aOR]: 5.940, 95% confidence interval [CI]: 3.124–11.292), anxiety (aOR: 4.233, 95% CI: 2.138–8.381), stress (aOR: 2.880, 95% CI: 1.915–4.330) and social support (aOR: 0.959, 95% CI: 0.939–0.980) have a significant effect on sleep quality after adjusted by sex, age, smoking status, drinking status, caffeine intake, past shift working and circadian rhythm type.

Depression, anxiety, stress and social support were associated with sleep quality among pre-employed firefighters. Repeated follow-up studies of pre-employed firefighters are needed to further assess their change of sleep quality and identify the FSJRF that may affect the sleep quality of firefighters.

The global labor market is moving towards increasing job instability. Relatively few studies have examined the relationship between precarious employment and subjective well-being using quantitative scales. We evaluated the association between wage workers' employment status and their subjective well-being through the Cantril ladder scale using Korean Welfare Panel Survey data (KOWEPS).

This study used KOWEPS data. A total of 4,423 wage workers were divided into permanently employed workers, temporarily employed workers and daily employed workers. The relationship between precarious employment and subjective well-being was analyzed by multiple linear regression adjusted for potential confounding factors.

The more unstable the employment status, the lower the subjective well-being, which can be expressed by the Cantril ladder scale. The mean score of both temporarily employed and daily employed workers were statistically significantly lower (B = −0.454, p < 0.001; B = −0.994, p < 0.001, respectively) than permanently employed workers. This appeared to be the same when occupational and sociodemographic factors were adjusted (B = −0.153, p = 0.002 for temporarily employed, B = −0.610, p < 0.001 for daily employed).

The more unstable the employment status, the lower the subjective well-being score according to the Cantril ladder scale.