Impact of neck posture and insulating stick use on neck disability in Korean line workers: a cross-sectional study.

Background: Occupational neck disability is a prevalent issue, especially among line workers, who are often exposed to elevated levels of cervical ergonomic stress. The aim of this study was to investigate the impact of neck posture and insulating stick use on neck disability in a specific occupational group in Korea. Methods: This cross-sectional study was conducted among 483 line workers in Gwangju and Jeonnam, Korea. Data were collected using the Neck Disability Index, Cervical Degenerative Index, and a structured questionnaire focusing on demographic and occupational factors. Logistic regression analysis was applied to determine the adjusted odds ratio (OR) and 95% confidence interval (CI) for neck posture and factors related to neck disability. Results: Neck disability prevalence was 17.2% among the participants. Multivariate logistic regression analysis showed that factors related to neck disability included age over 60 years (adjusted OR: 3.08; 95% CI: 1.63-5.83), depression (adjusted OR: 8.33; 95% CI: 3.85-18.00), a history of cervical trauma (adjusted OR: 2.13; 95% CI: 1.04-4.40), and radiological degenerative changes in the cervical spine (adjusted OR: 2.33; 95% CI: 1.26-4.33). In particular, the adjusted OR of neck disability among live-line workers was 2.10 (95% CI: 1.12-3.92) when compared with support workers (model 1). Other analysis models showed that use of insulating sticks for more than 10 hours per week (adjusted OR: 2.46; 95% CI: 1.32-4.61) and higher neck extension (adjusted OR: 2.98; 95% CI: 1.14-3.46) were significant work-related risk factors (model 2,3). Conclusions: Neck posture, age, depression, cervical trauma history, degenerative changes in the cervical spine, and use of insulating sticks are significant risk factors for neck disability among line workers in Korea. These findings highlight the need to improve the working environment and reduce the burden of cervical ergonomic stress among line workers.

Population attributable fraction of indicators for musculoskeletal diseases: a cross-sectional study of fishers in Korea.

Background: The musculoskeletal disease (MSD) burden is an important health problem among Korean fishers. We aimed to investigate the indicators of the prevalence of MSD and contributions of significant indicators to MSD in Korean fishers. Methods: This cross-section study included 927 fishers (male, 371; female, 556) aged 40 to 79 years who were enrolled from 3 fishery safety and health centers. The outcome variable was one-year prevalence of MSD in 5 body parts (the neck, shoulder, hand, back, and knee). Independent variables were sex, age, educational attainment, household income, job classification, employment xlink:type, hazardous working environment (cold, heat, and noise), ergonomic risk by the 5 body parts, anxiety disorder, depression, hypertension, diabetes, and hyperlipidemia. The adjusted odds ratio of MSDs by the 5 body parts were calculated using multiple logistic regression analysis. We computed the population attributable fraction (PAF) for each indicators of MSDs using binary regression models. Results: The one-year prevalence of MSD in the neck, shoulder, hand, back, and knee was 7.8%, 17.8%, 7.8%, 27.2%, and 16.2% in males vs. 16.4%, 28.1%, 23.0%, 38.7%, and 30.0% in females, respectively. The ergonomic risk PAF according to the body parts ranged from 22.8%-59.6% in males and 22.8%-50.3% in female. Mental diseases showed a significant PAF for all body parts only among female (PAF 9.1%-21.4%). Cold exposure showed a significant PAF for the neck, shoulder, and hand MSD only among female (25.6%-26.8%). Age was not a significant indicator except for the knee MSD among female. Conclusions: Ergonomic risk contributed majorly as indicators of MSDs in both sexes of fishers. Mental disease and cold exposure were indicators of MSDs only among female fishers. This information may be important for determining priority risk groups for the prevention of work-related MSD among Korean fishers.

Radiographic hand osteoarthritis in women farmers: characteristics and risk factors.

Background: Repetitive hand use increases the risk of hand osteoarthritis (OA). This study aimed to investigate characteristics of and risk factors for hand OA in Korean women farmers. Methods: This cross-sectional study included women farmers resident in Jeollanam-do, Korea. The participants were interviewed, and radiographs were taken of both hands. Radiological hand OA was defined based on the Osteoarthritis Research Society International imaging criteria of joint space narrowing or the presence of osteophytes. The participants were divided into age groups of < 60 and ≥ 60 years. Obesity was defined as body mass index of > 25 kg/m2. Annual working time was divided into < 2,000, 2,000-2,999, and ≥ 3,000 hours. Agricultural working type was divided into rice farming and field farming. Robust Poisson regression was used to identify factors associated with radiographic hand OA, with adjustment for age, obesity, annual working time, and agricultural classification. Results: A total of 310 participants with a mean age of 58.1 ± 7.6 years, were enrolled. The prevalence of radiologically confirmed OA was 49.0%, with an OA prevalence of 39.4% the interphalangeal joint in the thumb (IP1). The prevalence of OA was higher in the distal interphalangeal joint than in the proximal interphalangeal, metacarpophalangeal, and carpometacarpal joints. The prevalence of OA varied by age, annual working time, and agriculture type. Conclusions: Korean women farmers have a high prevalence of OA, particularly in the IP1 joints. OA is associated with age, working hours, and agriculture type.

Characteristics of lumbar disc degeneration and risk factors for collapsed lumbar disc in Korean farmers and fishers.

BACKGROUND: Few studies have investigated the risk factors for lumbar intervertebral disc degeneration among hard physical workers involved in heavy lifting. In this study, we aimed to identify the characteristics of lumbar intervertebral disc degeneration and evaluate the relationship between collapsed lumbar disc and potential risk factors in farmers and fishers. METHODS: This study included 203 farmers (103 men and 100 women) and 166 fishers (95 men and 71 women) aged 40-69 years who had undergone lumbar magnetic resonance imaging and were enrolled in the Korea Farmer's Knee Cohort and the Jeonnam Fishers' Cohort. We evaluated each of the 5 lumbar discs using the Pfirrmann grading system and classified collapsed lumbar intervertebral disc (cLD) as a case with ≥ 1 grade 5 at any disc level. We investigated potential risk factors, such as gender, age, body mass index (BMI), working hours per day, working months per year, and cumulative heavy lifting working time (CLWT). The odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) were calculated. RESULTS: The prevalence of cLD was 19.8% (23.7% among fishers, 21.2% among fishers with farming, and 17.2% among farmers). cLD correlated with factors such as age and occupation. Gender, CLWT and the working time matrix were not significantly associated with cLD. The OR of cLD adjusted by gender, age, BMI, and working time matrix was 1.26 (95% CI: 0.69-2.30) for ≥ 5,000 hours CLWT compared to that for < 2,000 hours CLWT. The OR of cLD adjusted by gender, age, BMI, CLWT, and working time matrix was 2.08 (95% CI: 1.06-4.06) for fishers compared to that for farmers. CONCLUSIONS: Heavy lifting did not show a significant association with cLD in farmers and fishers. However, there is possibility that fishers are at a higher risk of lumbar disc collapse than farmers.

Work-Related Risk Factors of Knee Meniscal Tears in Korean Farmers: A Cross-Sectional Study.

BACKGROUND: Meniscal tears are among the major risk factors for knee osteoarthritis progression. This study aimed to investigate the relationship between meniscal tears and work-related factors in the farming occupation. METHODS: The participants included 486 farmers (238 men and 248 women), aged 40-69 years, who were among the 550 farmers registered in the Korea Farmer's Knee Cohort (KFKC). Data such as those on gender, age, body mass index (BMI), mechanical axis, cumulative heavy-lifting working time (CLWT), cumulative squatting working time (CSWT), and previous knee injury history were collected from the questionnaire, along with whole leg radiographic findings. Two radiologists assessed the magnetic resonance images of both knees to confirm the presence of meniscal tears. The factors related to meniscal tears were analyzed by multiple logistic regression. RESULTS: A total of 54.5% of the farmers (48.7% of men and 60.1% of women) had meniscal tears. These tears were associated with gender, age, and BMI. We also identified an association between meniscal tears and CSWT, an especially important factor in farming [10,000-19,999 working hours, odds ratio = 2.16, 95% confidence interval (CI): 1.14-4.07, ≥20,000 working hours, odds ratio = 2.35, 1.45-3.80]. However, mechanical axis, knee injury history, and CLWT were not significantly related to meniscal tears. CONCLUSION: This study's findings show that squatting for long periods, as an occupational factor, is related to meniscal tears.

Factors related to femoral bowing among Korean female farmers: a cross-sectional study.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Work-related factors of knee osteoarthritis in Korean farmers: a cross-sectional study.

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

Effects of work-related factors on self-reported smoking among female workers in call centers: a cross-sectional study.

OBJECTIVES: This study conducted to investigate work-related factors in relation to smoking among women working in call centers in Gwangju, South Korea. METHODS: From 56 call centers (7320 employees), we selected 10 and conducted a survey using a structured questionnaire by randomly selecting 10% of workers from each center. A total of 387 subjects participated in this survey We analyzed for 375 respondents, after excluding men and those with missing responses. We analyzed the relationships of work-related factors such as emotional labor, workplace violence, employment type, annual salary, working hours, employment period with smoking, using multiple logistic regression analysis. Emotional labor and workplace violence were measured using the Korean Emotional Labor Scale (K-ELS) and Korean Workplace Violence Scale (K-WVS). RESULTS: The prevalence of current smoking among call center female workers was 13.6%. Univariate analysis showed that "Emotional disharmony and hurt", "Experience of psychological and sexual violence from supervisors and co-workers" among items of K-ELS and K-WVS, working hours, annual salary correlated with smoking. After adjusting for emotional labor, workplace violence, employment type, annual salary, working hours, employment period, and age, only working hours show a significant association with smoking. Women who worked 40-49 h had 3.50 times (95% CI = 1.04-11.80) and worked more than 50 h had 8.68 times (95% CI = 1.89-39.78) greater odds of smoking as compared with women who worked less than 40 h. CONCLUSIONS: Smoking was associated with working hours among female workers in call center. However, emotional labor and workplace violence did not show significant relationships with smoking.

Evaluation of the prevalence of musculoskeletal symptoms, presumptive diagnosis, medical care use, and sick leave among female school meal service workers.

BACKGROUND: Most of the school meal service workers in Korea are middle-aged individuals. They have high workload, which increases their incidence of musculoskeletal disorders. This study aimed to evaluate the prevalence and risk factors of subjective musculoskeletal symptoms, presumptive diagnosis, medical care use, and sick leave among female school meal workers. METHODS: We analyzed the results of musculoskeletal disease screening of 1581 female school meal workers. The screening consisted of self-administered questionnaire, history taking by occupational physicians, and physical examination. The prevalence of subjective musculoskeletal symptoms, presumptive diagnosis after initial examination by occupational physicians, use of medical care for more than 7 days, and sick leave due to musculoskeletal diseases during the past year were evaluated in this study. The relative risk of four outcome indicators of musculoskeletal disorders was compared with respect to potential factors, such as age, subjective physical loading, present illness, injury experience, and type of school, using log-binomial regression. RESULTS: The prevalence of subjective musculoskeletal symptom was 79.6%; presumptive diagnosis, 47.6%; hospital visits over 7 days, 36.4%; and sick leave, 7.3%. The relative risk of musculoskeletal symptoms by age (≥50 years vs < 50 years) was 1.04 (95% confidence interval (CI): 1.00-1.09); presumptive diagnosis of musculoskeletal disease, 1.17 (95% CI: 1.06-1.30); hospital visits over 7 days, 1.26 (95% CI: 0.85-1.85); and sick leave, 1.17 (95% CI: 1.02-1.34). The relative risk of musculoskeletal symptoms due to subjective physical loading (very hard vs low) was 1.45 (95% CI: 1.33-1.58); presumptive diagnosis, 2.92 (95% CI: 2.25); hospital visits over 7 days, 1.91 (95% CI: 1.02-3.59); and sick leave, 2.11 (95% CI: 1.63-2.74). CONCLUSIONS: Subjective physical loading was a more important factor in musculoskeletal disorders than the age of female school meal workers.

Environmental Tobacco Smoke Exposure at Home and High-Sensitivity C-Reactive Protein Levels in Three-to-Five-Year-Old Children.

Exposure to harmful environmental factors is particularly detrimental to younger children. We investigated the relationship between environmental tobacco smoke (ETS) exposure in pre-schoolers at home and the level of high-sensitivity C-reactive protein (hs-CRP), a predictive factor for cardiovascular disease. This study was conducted in 2014 and was based on the data of preschool children from the Korean Environmental Health Survey in Children and Adolescents (2012 to 2014), a nationally representative sample. Of 577 children, aged three to five years, 482 were eventually selected for the analysis after excluding those with missing variables, or whose hs-CRP level exceeded the reference value. The proportion of pre-school children exposed to ETS at home was 14.8%. The odd ratios (OR)s of hs-CRP > 1mg/L were 4.90 (95% Confidence Interval (CI) = 1.04-23.17) and 11.66 (95% CI = 1.90-71.65) in the groups exposed to ETS 3-4 times and ≥5 times daily, respectively, compared to the non-exposed group. The risk of elevated levels of hs-CRP showed an increasing trend proportionally to the increase in ETS exposure frequency (p for trend = 0.03). Anti-smoking educational programs for parents and guardians may be helpful to reduce ETS exposure at home.

Cases of acute mercury poisoning by mercury vapor exposure during the demolition of a fluorescent lamp factory.

BACKGROUND: In 2015, workers dismantling a fluorescent lamp factory in Korea were affected by mercury poisoning from exposure to mercury vapor. CASE PRESENTATION: Eighteen out of the 21 workers who participated in the demolition project presented with symptoms of poisoning and, of these, 10 had persistent symptoms even at 18 months after the initial exposure to mercury vapor. Early symptoms of 18 workers included a general skin rash, pruritus, myalgia, sleep disturbance, and cough and sputum production. Following alleviation of these initial symptoms, late symptoms, such as easy fatigue, insomnia, bad dreams, and anxiety disorder, began to manifest in 10 out of 18 patients. Seven workers underwent psychiatric care owing to sleep disturbance, anxiety disorder, and depression, and three workers underwent dermatologic treatment for hyperpigmentation, erythematous skin eruption, and chloracne-like skin lesions. Furthermore, three workers developed a coarse jerky movement, two had swan neck deformity of the fingers, and two received care at an anesthesiology clinic for paresthesia, such as burning sensation, cold sensation, and pain. Two workers underwent urologic treatment for dysfunction of the urologic system and impotence. However, symptomatic treatment did not result in satisfactory relief of these symptoms. CONCLUSION: Awareness of the perils of mercury and prevention of mercury exposure are critical for preventing health hazards caused by mercury vapor. Chelation therapy should be performed promptly following mercury poisoning to minimize damage.

Systemic sclerosis due to crystalline silica exposure among jewelry workers in Korea: two case reports.

BACKGROUND: Occupational exposure to crystalline silica is a potential risk factor for various systemic autoimmune diseases including systemic sclerosis. The etiology of systemic sclerosis is not conclusively known, but there are epidemiological studies that show the relationship between exposure to crystalline silica and risk of systemic sclerosis. Here we report, for the first time, two cases of crystalline silica-related systemic sclerosis in patients who worked in crystal processing in the jewelry-manufacturing field. CASE PRESENTATION: Case 1 is a 57-year-old man who had worked mainly in crystal processing for multiple jewelry-processing companies for 17 years, since the age of 15 years. He contracted tuberculosis at the age of 25 years and showed Raynaud's phenomenon of both the hands and feet at age 32 years. Digital cyanosis and sclerosis developed at approximately age 41 years. The patient was diagnosed with systemic sclerosis at age 48 years. Case 2 is a 52-year-old man who worked in crystal processing for various jewelry-processing companies for 7 years, since the age of 23 years. He first showed signs of cyanosis in the third and fourth digits of both hands at age 32 years, was diagnosed with Raynaud's syndrome at age 37 years, and was diagnosed with systemic sclerosis at age 38 years. Crystal processing is a detailed process that involves slabbing and trimming the selected amethyst and quartz crystals, which requires close proximity of the worker's face with the target area. In the 1980s and 1990s, the working hours were 12 h per day, and the working environment involved 15 workers crowded into a small, 70-m2 space with poor ventilation. CONCLUSION: Two workers who processed crystals with a maximum crystalline silica content of 56.66% developed systemic sclerosis. Considering the epidemiological and experimental evidence, exposure to crystalline silica dust was an important risk factor for systemic sclerosis. An active intervention is necessary to reduce exposure in similar exposure groups in the field of jewelry processing.

Comparison of facet joint degeneration in firefighters and hospital office workers.

BACKGROUND: There are few published studies on the relationship between occupational lumbar load and facet joint degeneration (FJD). This cross-sectional study was conducted to evaluate the effect of physical lumbar load on FJD by comparing magnetic resonance imaging (MRI) findings of firefighters (FFs) and hospital office workers (HOWs). METHODS: We randomly sampled 341 male FFs and 80 male HOWs by age stratification. A questionnaire and clinical examination, including MRI of the lumbar spine (T12-S1), were conducted. FJD was diagnosed and graded by using the classification of Pathria et al., and reclassified into two groups as follows: no FJD (grade 0) and FJD (grades 1, 2, and 3). The prevalence of FJD was analyzed according to occupational group. RESULTS: The prevalence of FJD ranged from 31% (L1-L2) to 75% (L4-L5) in the FFs, and from 18% (L1-L2) to 69% (L4-L5) in the HOWs. After adjustment for age, body mass index, and frequency of physical exercise, the adjusted odds ratios (OR) for FJD in the FFs were significantly higher than those in the HOWs at all lumbar spinal levels, except for L3-L4 (L1-L2: OR, 2.644; 95% confidence interval [CI], 1.317-5.310; L2-L3: OR, 2.285; 95% CI, 1.304-4.006; L4-L5: OR, 1.918; 95% CI, 1.037-3.544; L5-S1: OR, 1.811; 95% CI, 1.031-3.181). CONCLUSION: This study shows that FFs exhibit a greater likelihood of having FJD than HOWs after controlling for other risk factors of FJD. This suggests that the physical occupational demands of FFs affect their risk of developing FJD.

Air pollution and urinary n-acetyl-B-glucosaminidase levels in residents living near a cement plant.

BACKGROUND: To identify adverse renal effects due to air pollution derived from a cement plant in Korea. Urinary n-acetyl-B-glucosaminidase (U-NAG) levels in residents living near a cement plant were compared to those in a group who lived farther away from the plant. METHODS: From June to August 2013 and from August to November 2014, laboratory tests for U-NAG and heavy metal were conducted on 547 study participants. Based on the level of air pollution exposure, subjects were divided into the "less exposed group," (LEG) which consisted of 66 persons who lived more than 5 km away from the cement plant, the "more exposed group from the rural area" (MEG-R), which consisted of 272 persons, and the "more exposed group from downtown area" (MEG-D), which consisted of 209 persons who lived within a 1 km radius of the cement plant. U-NAG levels >5.67 U/L were defined as "higher U-NAG" levels. We compared the prevalence of higher U-NAG levels and estimated the adjusted odds ratio (OR) by air pollution exposure using a chi-square test and multiple logistic regression analysis. Further, we estimated the interaction between air pollution exposure and heavy metal exposure in renal toxicity. RESULTS: The OR of higher U-NAG levels by MEG-D and MEG-R compared to LEG was 2.13 (95 % CI 0.86-4.96) and 4.79 (95 CI 1.65-10.01), respectively. Urinary cadmium (U-Cd), urinary mercury (U-Hg), age, occupation, hypertension, and diabetes had a significant association with higher U-NAG levels. However, blood lead (B-Pb), sex, and smoking were not associated with higher U-NAG. Especially, concurrent exposure to heavy metals (U-Hg or/and U-Cd) and air pollution had an additive adverse effect. In the group with both 4th quartile heavy metal exposure (U-Cd or/and U-Hg) and air pollution exposure, the OR in MEG-R and MEG-D was 6.49 (95 % 1.42-29.65) and 8.12 (95 % CI 1.74-37.92), respectively, after adjustment for age, occupation, hypertension, diabetes. CONCLUSIONS: U-NAG levels seem to be affected by air pollution exposure as well as age, hypertension, diabetes, and even low levels of cadmium and low levels of mercury. Moreover, concurrent exposure to heavy metals and air pollution can have additive cytotoxic renal effects.

Lumbar intervertebral disc degeneration and related factors in Korean firefighters.

OBJECTIVES: The job of firefighting can cause lumbar burden and low back pain. This study aimed to identify the association between age and lumbar intervertebral disc degeneration and whether the association differs between field and administrative (non-field) firefighters. METHODS: Subjects were selected using a stratified random sampling method. Firefighters were stratified by geographic area, gender, age and type of job. First, 25 fire stations were randomly sampled considering regional distribution. Then firefighters were stratified by gender, age and their job and randomly selected among the strata. A questionnaire survey and MRI scans were performed, and then four radiologists used Pfirrmann classification methods to determine the grade of lumbar intervertebral disc degeneration. RESULTS: Pfirrmann grade increased with lumbar intervertebral disc level. Analysis of covariance showed that age was significantly associated with lumbar intervertebral disc degeneration (p<0.05). The value of ß (parameter estimate) was positive at all lumbar intervertebral disc levels and was higher in the field group than in the administrative group at each level. In logistic regression analysis, type of job was statistically significant only with regard to the L4-5 intervertebral disc (OR 3.498, 95% CI 1.241 to 9.860). CONCLUSIONS: Lumbar intervertebral disc degeneration is associated with age, and field work such as firefighting, emergency and rescue may accelerate degeneration in the L4-5 intervertebral disc. The effects of field work on lumbar intervertebral disc degeneration were not clear in discs other than at the level L4-5.

Effect of thigh muscle fatigue on the biomechanical factors of the lower limbs when walking in a squatted position.

[Purpose] The purpose of this study was to compare and analyze the effects of thigh muscle fatigue caused by walking in a squatted position on biomechanical factors, to evaluate the risk of a job performed sitting in a squatted position for a long period of time. [Subjects and Methods] Eighteen right foot dominant women without any injuries in their joints and body in the last 6 months were selected. They walked in a squatted position, and then muscle fatigue was induced by using an isokinetic muscular function measuring device (CSMI, USA). After the CSMI measurement, the participants performed walking in a squatted position again. [Results] After inducing thigh muscle fatigue, the knee joint maximum adduction moment significantly increased and the required duration was reduced. The muscle fatigue index was positively correlated with adduction moment and negatively with the duration. It influenced the changes of maximum adduction moment; 55.0% of the adduction moment change was explained by the degree of fatigue. [Conclusion] A quantitative analysis of working in a squatted position was performed. The thigh muscle fatigue index negatively the knee joint during walking in a squatted position. Therefore, this experiment can be used as an ergonomic analysis tool of general farm work.

Emphysema prevalence related air pollution caused by a cement plant.

BACKGROUND: To identify adverse pulmonary health effects due to air pollution derived from a cement plant in Korea. The emphysema prevalence in residents around a cement plant was compared to that in the group who live far away from the plant by chest films (PA and lateral view) and high-resolution computed tomography (HRCT) lung images. METHODS: From June to August in 2013 and from August to November in 2014, chest films and HRCT scan were conducted on residents over the age of 40 who lived around a cement plant. The residents were divided into two groups; a "more exposed group (MEG)" which consisted of 1,046 people who lived within a 1 km radius and a "less exposed group (LEG)" which consisted of 317 people who lived more than 5 km away from the same plant. We compared the emphysema prevalence and estimated the OR of this between the MEG and the LEG by using a chi-square and logistic regression on chest films and HRCT. RESULTS: The emphysema prevalence was 9.1 % in the LEG, 14.3 % in the MEG on chest films and 11.4 %, 17.8 % on the HRCT, respectively. The OR of the emphysema prevalence in MEG was 2.92 (95 % CI 1.77-4.83) on the chest films, 2.56 (95 % CI 1.64-3.99) on the HRCT after sex, age, body mass index (BMI), smoking history, residency period and firewood used history were adjusted. The OR in the less than 29 pack-years smoking history was 1.66 (95 % CI 0.92-3.06) and in the more than 30 pack-years was 3.05 (95 % CI 1.68-5.52) on the chest films, and was 1.68 (95 % CI 0.98-2.90), 2.93 (95 % CI 1.72-4.98) on the HRCT, respectively. CONCLUSION: The emphysema prevalence seems to be affected by the level of exposure to air pollution derived from the cement plant as well as sex, age, BMI, and smoking history in this study. Moreover, the OR of the case of the more exposed to the air pollution was similar to that of the case in smoking.

Representative levels of blood lead, mercury, and urinary cadmium in youth: Korean Environmental Health Survey in Children and Adolescents (KorEHS-C), 2012-2014.

BACKGROUND: This study examined levels of blood lead and mercury, and urinary cadmium, and associated sociodemographic factors in 3-18 year-old Korean children and adolescents. MATERIALS AND METHODS: We used the nationally representative Korean Environmental Health Survey in Children and Adolescents data for 2012-2014 and identified 2388 children and adolescents aged 3-18 years. The median and 95th percentile exposure biomarker levels with 95% confidence intervals (CIs) were calculated. Multivariate regression analyses were performed on log transformed exposure biomarker levels adjusted for age, sex, area, household income, and father's education level. The median exposure biomarker levels were compared with data from Germany, the US, and Canada, as well as the levels of Korean children measured at different times. RESULTS: The median levels of blood lead and mercury, as well as urinary cadmium were 1.23µg/dL, 1.80µg/L, and 0.40µg/L (95% CIs, 1.21-1.25, 1.77-1.83, and 0.39-0.41, respectively). The blood lead levels were significantly higher in boys and younger children (p<0.0001) and children with less educated fathers (p=0.004) after adjusting for covariates. Urinary cadmium level increased with age (p<0.0001). The median levels of blood mercury and urinary cadmium were much higher in Korean children and adolescents than those in their peers in Germany, the US, and Canada. Blood lead levels tended to decrease with increasing age and divergence between the sexes, particularly in the early teen years. Median levels of blood lead and urinary cadmium decreased since 2010. CONCLUSION: Sociodemographic factors, including age, sex, and father's education level were associated with environmental exposure to heavy metals in Korean children and adolescents. These biomonitoring data are valuable for ongoing surveillance of environmental exposure in this vulnerable population.

Association of current phthalate exposure with neurobehavioral development in a national sample.

BACKGROUND: Previous studies have indicated that phthalate exposure may influence the development of children, but the current data are limited, and controversy remains regarding the sex-specific and age-specific effects of phthalate exposure. METHODS: We investigated the sex- and age-specific associations of current phthalate exposure with neurobehavioral development scores in a nationally representative sample of 6-18-year-olds participating in the Korean Environmental Health Survey in Children and Adolescents (KorEHS-C). Neurobehavioral development was assessed using the Korean Child Behavior Checklist (CBCL, N=1723) and the Korean Attention Deficit Hyperactivity Disorder Rating Scale (ARS, N=867). We measured the concentrations of phthalate metabolites in urine samples using high-performance liquid chromatography tandem mass spectrometry. The associations between urine phthalate metabolite concentrations and neurobehavioral development were examined by survey regression analysis for complex sampling and penalized regression splines using a generalized additive model. RESULTS: Survey regression analysis revealed that a higher mono-n-butyl phthalate (MnBP) level was associated with social (ß=0.60; 95% confidence interval=0.15-1.05), thought (0.55; 0.08-1.03), and attention (0.68; 0.21-1.14) problems on the CBCL. A significant association was found between the MnBP level and the ARS hyperactivity subscale score (0.42; 0.05-0.58). Higher levels of MnBP (0.87; 0.20-1.54), mono-2-ethyl-5-oxohexyl phthalate (MEOHP, 0.61; 0.11-1.11) and mono-2-ethyl-5-hydroxyhexyl phthalate (MEHHP, 0.51; 0.04-0.97) were associated with an increase in thought problems among the girls. Among the younger children aged 6-11 years, significant positive associations between the MnBP (0.71; 0.09-1.33), MECPP (0.74, 0.14-1.34), MEOHP (0.65; 0.10-1.20), and MEHHP (0.71; 0.21-1.21) levels and social problems and between the MnBP (1.11; 0.37-1.84), MEOHP (0.64; 0.13-1.15), and MEHHP (0.66; 0.18-1.14) levels and attention problems were observed. The penalized regression splines for the age-specific relationships between the urinary MnBP, MEOHP, and MEHHP levels and social and attention problems exhibited positive supralinear relationships with downward curvature in the 6-11 year age group. In contrast, the score for social problems exhibited nearly linear relationships with these levels in the 12-18 year age group. CONCLUSIONS: In this national sample, increased phthalate exposure exhibited supralinear associations with social, thought and attention problems in children aged 6-11 years, who showed greater vulnerability to phthalate exposure. The results highlight the need for the environmental regulation of phthalate exposure in younger children, even at low dosages.

Ventilation impairment of residents around a cement plant.

OBJECTIVES: To identify adverse health effects due to air pollution derived from a cement plant in Korea. The ventilation impairment in residents around a cement plant was compared to another group through a pulmonary function test (PFT). METHODS: From June to August of 2013, both a pre and post-bronchodilator PFT was conducted on a "more exposed group (MEG)" which consisted of 318 people who lived within a 1 km radius of a cement plant and a "less exposed group (LEG)" which consisted of 129 people who lived more than 5 km away from the same plant. The largest forced expiratory volume in a one second (FEV1) reading and a functional residual capacity (FVC) reading were recorded after examining the data from all of the usable curves that were agreed upon as valid by PFT experts of committee of National Institute of Environmental Research. The global initiative for chronic obstructive lung disease (GOLD) criteria for COPD, defined the FEV1/FVC ratio < 0.7 as the obstructive type, and the FEV1/FVC ratio ≧ 0.7 and FVC% predicted < 80% were as the restrictive type. The FVC% predicted value was estimated using Korean equation. We compared the proportion of lung function impairments between the MEG and the LEG by using a chi-square, and estimated the OR of obstructive and restrictive ventilation impairments by logistic regression. RESULTS: The obstructive type impairment proportion was 9.7% in the MEG, whereas it was 8.5% in the LEG. The restrictive type was 21.6% in the MEG which was more than the 12.4% of the LEG. The odds ratio (OR) of total ventilation impairment in the MEG was 2.63 (95% CI 1.50 ~ 4.61) compared to the LEG. The OR of obstructive type in the MEG was 1.60 (95% CI 0.70 ~ 3.65), the smoking history was 3.10 (CI 1.10 ~ 8.66) whereas OR of restrictive type in the MEG was 2.55 (95% CI 1.37 ~ 4.76), the smoking history was 0.75 (95% CI 0.35 ~ 1.60) after adjusting for sex and age. Level of exposure to particulate played a role in both types. However, it appeared to be a significant variable in restrictive type, while smoking history was also an important variable in obstructive type. CONCLUSION: Although this study is a limited cross-section study with a small number of subjects, ventilation impairment rate is higher in the MEG. There might be a possibility that it is due to long-term exposure to particulate dust generated by the cement plant.