Objective: Noise has always been an important environmental public health issue for mankind. Although reports exist on hippocampal-dependent spatial learning and memory (LM) impairment due to noise, there are only a few studies that have examined the effects of recovery from noise stress on LM impairments. Therefore, the present study investigated the effects of recovery from chronic noise exposure on LM deficits. Materials and Methods: In this study, the detrimental effects of noise stress on young male rats in the Morris water maze (MWM) were investigated at 1, 10, 20, 30, and 40 days after the discontinuation of chronic noise exposure of 80 dB or 100 dB for 4 h per day, for 30 days. The levels of monoamine neurotransmitters in the hippocampus were also evaluated by HPLC-EC at the end of each behavioral test. Results: Statistical analysis revealed that rats in the noise-treated groups failed to reach the same level of performance as the controls in the MWM. Further, the levels of dopamine (DA), norepinephrine (NE) and 5-hydroxytryptamine (5-HT) were significantly decreased in the hippocampus after noise exposure. However, the reduction in monoamine levels and impaired water maze performance recovered over time, so that by 30th day after cessation of noise exposure the 80 dB group showed no performance difference from the controls, and by 40th day, the 100 dB group also showed no performance difference from the control. Conclusion: Our findings suggest that noise impaired LM in young male rats and reduced monoamine neurotransmitters in the hippocampus. However, the noise-induced water maze deficits recovered over time, and the concurrent restoration of hippocampal monoamine neurotransmitter levels suggest that they are involved in LM impairments.

View full abstract

Objective: We investigated the association between job stress and insomnia in a large nationwide samples of Korean workers. Methods: In this cross-sectional study, a total of 8,155 workers from a nationwide sample were recruited. We surveyed the subjects' socio-demographic and work-related characteristics and seven subscales of occupational stress using the Korean Occupational Stress Scale Short Form. Each subscales of job stress was dichotomized into higher or lower group by respective median scores. Insomnia was defined as having at least one of the three sleep symptoms. we performed multivariate logistic regression analysis to identify association between job stress and insomnia. Results: We found that individuals with relatively high job stress experienced insomnia significantly more frequently, and the significance was maintained even after adjustment for confounding variables(high job demand: OR: 1.30, 95% CI: 1.14-1.47; insufficient job control: OR: 1.13, 95% CI: 0.99-1.29; inadequate social support: OR: 1.30, 95% CI: 1.14-1.47; job insecurity: OR: 1.25, 95% CI: 1.11-1.44; organizational injustice: OR: 1.27, 95% CI: 1.12-1.44; lack of reward: OR: 1.18, 95% CI: 1.04-1.34; discomfort in occupational climate: OR: 1.38, 95% CI: 1.22-1.57; total job stress: OR: 1.45, 95% CI: 1.28-1.64). Conclusion: This study suggested that job stress is possible risk factor for insomnia and that particularly discomfort in occupational climate and inadequate social support have more strong relation to insomnia in Korea.

View full abstract

Objectives: Carcinogenicity and chronic toxicity of indium-tin oxide (ITO) were examined by inhalation exposure of rats and mice to ITO aerosol. Methods: Fifty mice of both sexes were exposed to ITO at 0 (control), 0.01, 0.03 or 0.1 mg/m³ for 6 h/day, 5 day/wk for 104 wk, and 50 rats of both sexes were exposed to 0, 0.01 or 0.03 mg/m³ ITO for the same time period. The repeated exposure of 50 rats of both sexes to 0.1 mg/m³ ITO was discontinued at the 26th wk, followed by clean air exposure for the remaining 78 wk. Results: In rats, incidences of bronchiolo-alveolar adenomas and carcinomas, bronchiolo-alveolar hyperplasia, alveolar wall fibrosis and thickened pleural wall, alveolar proteinosis and infiltrations of alveolar macrophages and inflammatory cells were significantly increased. Combined incidences of malignant lung tumors in male rats and total lung tumors in male and female rats were significantly increased at exposure to 0.01 mg/m³ ITO. In mice, no carcinogenic response occurred, but thickened pleural wall, alveolar proteinosis and alveolar macrophage infiltration were induced. Mice were less susceptible to ITO than rats. The lung content of indium was the greatest, followed by the spleen, kidney and liver. Blood indium levels increased dose-dependently. Conclusions: There was clear evidence of carcinogenicity of inhaled ITO in male and female rats but not clear evidence in mice, together with occurrence of the chronic pulmonary lesions in both rats and mice.

View full abstract

Objectives: The purpose of this study was to validate a Japanese version of the organization-based self-esteem (OBSE) scale, a positive self-concept that has been proven to play an important role in predicting employees' work attitudes and behaviors primarily in a Western organizational setting. Methods: Two independent field studies, Study One and Study Two, involving 1,562 Japanese employees from a variety of organizations were conducted by employing a web-based questionnaire. Results: In Study One, initial evidence for the factorial validity of an eight-item, single factor scale, with high internal consistency (0.93 and 0.88 for Sample 1 and Sample 2, respectively) and test-retest reliability (r=0.84) was provided. In Study Two, the eight-factor structure was replicated and multiple-group confirmatory factor analysis (CFA) demonstrated measurement invariance across two samples. In addition, a series of CFA demonstrated that the Japanese OBSE is a distinct construct from global self-esteem, job complexity and work engagement. Furthermore, the nomological validity evidence was demonstrated through structural equation modeling. Conclusions: The Japanese OBSE scale is presented as a psychometrically sound measure that can contribute to furthering substantive OBSE research.

View full abstract

Objectives: To investigate the association between hours worked, symptoms experienced, and health resource utilization. Methods: Data were collected from a nationally representative sample of households in Japan. We studied full-time male workers aged 18-65 yr who worked 100 h or more per month. First, we examined the association between hours worked and symptoms experienced. Second, we examined the association between hours worked and the type of health resource utilized, such as physician visits, over-the-counter (OTC) medication use, dietary supplement use, and complementary and alternative medicine (CAM) provider visits. We used a multivariable negative binominal model in each analysis. Results: Of the 762 male workers, 598 reported experiencing symptoms at least once a month. We categorized participants based on the number of hours worked per month (h/mo): 100-200 h/mo, 201-250 h/mo, and over 250 h/mo. Compared with those working 201-250 h/mo, those working 100-200 h/mo had more frequent physician visits (rate ratio:1.67, 95% CI: 1.17 to 2.38) and those working over 250 h/mo had significantly lower rates of CAM provider visits and tended to use dietary supplements for symptoms. Participants who worked 201-250 h/mo used OTC medication most frequently. No significant association was observed between the number of hours worked and number of symptoms experienced. Conclusions: The more hours worked by full-time male workers, the more likely they were to use health resources that had a lower time requirement. Greater attention should be paid to patterns of health resource utilization among workers and their consequent influence on long-term health status.

View full abstract

Objectives: This study investigated the association between self-reported good health and self-valued good social life. An additional aim was to examine entrepreneur's strategies for maintaining good health. Methods: The study design included a two-wave questionnaire, with five years between the surveys (2001 and 2006), and qualitative interviews. The study group consisted of 246 entrepreneurs from the central region of Sweden and represented ten different trades. Entrepreneurs reporting good health in both 2001 and 2006 were compared with entrepreneurs reporting poor health on both occasions or with inconsistent answers. Six of the entrepreneurs were strategically chosen for the interview study. Results: Consistent good health was reported by 56% of the entrepreneurs. Good social life in 2001 was associated with an increased odds ratio (OR) for consistent good health when the analyses were adjusted for physical work conditions and job satisfaction (OR 2.12, 95% CI 1.07-4.17). Findings for good leisure time, weekly moderate physical exercise, and a rating of work being less or equally important as other life areas, were similar but not statistically significant when job satisfaction was considered in the analyses. Strategies for maintaining good health included good planning and control over work, flexibility at work, good social contact with family, friends and other entrepreneurs, and regular physical exercise. Conclusion: This study demonstrated an association between self-reported good health and good social life for entrepreneurs in small-scale enterprises. In addition, the entrepreneurs emphasised strategies such as planning and control over work and physical exercise are important for maintaining good health.

View full abstract

Objectives: Workplace violence is a work stressor which is presumed to lead to burnout, whereas social support is hypothesized to buffer the impact of such a stressor on health outcomes. In this study the association between burnout and workplace violence was investigated, and the role played by social support in moderating the relationship assessed. The study group consisted of workers in the road passenger transport sector in Maputo City, Mozambique. Methods: A random sample of 504 participants was selected from a register of 2,618 drivers and conductors working with road passenger transport. The study design was cross-sectional. Previously validated measures of burnout, workplace violence and social support were used. Results: The prevalence of severe burnout was 3.6% and of mild burnout 30.1%. Workplace violence was significantly associated with burnout after control for potential confounders. Burnout was more common among workers lacking social support following workplace violence than among peers who had received supported following an incident of violence. Conclusions: The study suggests that burnout is a public health problem among workers in the road passenger transport sector, and may be closely and independently linked to workplace violence. Social support appears to buffer or moderate the effect of workplace violence on burnout. This has implications for policy in the workplace. Strategies and guidelines are needed to support workers following workplace violence, since these may prove vital in reducing burnout and other psychosocial consequences.

View full abstract

Objectives: Dental caries and periodontal disease are highly prevalent in the Japanese adult population. Oral examination is an effective method to find various oral health problems in their early stages. However, workplace oral examination is not common in Japan. The purpose of this study was to examine the relationship between receiving workplace oral health examination, including oral health instruction, and oral health status in the Japanese adult population. Methods: This study was performed using data from 4,484 Japanese employees aged 35-74 yr. The proportion of teeth with a probing depth (PD) ≥4 mm and the number of decayed teeth were used for periodontal disease and dental caries parameters. The subjects were asked by questionnaire about past experiences with workplace oral health examination. Results: The subjects who received a workplace oral health examination every year had better periodontal health status than those receiving an examination for the first time. The odds ratio for having ≥10% of teeth with PD ≥4 mm in the subjects who received workplace oral health examination every year was 0.63 (p<0.05) after adjustment for age, sex, smoking habits, tooth-brushing habits, routine visits to dental clinics, number of missing teeth, and oral hygiene status, in a multivariate, multinomial logistic regression analysis. On the other hand, no significant relationship was found between workplace oral health examination and number of decayed teeth. Conclusions: These results suggest that workplace oral health examination accompanied by oral health instruction may be effective for maintenance of periodontal health.

View full abstract

Objectives: The purpose of this research was to develop a determination method for xylidines (XLDs) in workplace air for risk assessment. Methods: The characteristics of the proposed method, such as recovery, detection limit, reproducibility, and storage stability of the samples were examined. Results: An air sampler cassette containing two sulfuric acid-treated glass fiber filters was chosen as the sampler. The XLDs were extracted from the sampler filters, derivatized with heptafluorobutyric anhydride, and then analyzed by a gas chromatograph equipped with a mass spectrometer. The average recoveries of XLDs from the spiked sampler were 83-101% for personal exposure monitoring. The recovery after 5 days of storage in a refrigerator exceeded 90%. The overall limit of quantitation (LOQ) was 0.600 g/sample. The relative standard deviation, which represents the overall reproducibility defined as precision, was 0.8-10.3%. Conclusions: The proposed method enables 4-hour personal exposure monitoring of XLDs at concentrations equaling 0.001-2 times the threshold limit value-time-weighted average (TLV-TWA: 0.5 ppm) adopted by the American Conference of Governmental Industrial Hygienists, and is useful for estimating worker exposure to XLDs.

View full abstract

Objectives: Inhalation toxicities of indium-tin oxide (ITO) and indium oxide (IO) in mice were characterized in comparison with those previously reported in rats. Methods: B6C3F₁ mice of both sexes were exposed by inhalation to ITO or IO aerosol for 6 h/day, 5 day/wk for 2 wk at 0, 0.1, 1, 10 or 100 mg/m³ or 13 wk at 0, 0.1or 1 mg/m³. Results: ITO and IO particles were deposited in the lung, mediastinal lymph node (MLN) and nasal-associated lymphoid tissue. Alveolar proteinosis, infiltrations of alveolar macrophages and inflammatory cells and increased lung weight were induced by 2- and 13-week exposures to ITO and IO, while alveolar epithelial hyperplasia occurred only in the 2-week exposures. Thickened pleural wall, hyperplastic MLN, extramedullary hematopoiesis in the spleen and increased levels of erythrocyte parameters were induced by 13-week exposure to ITO. The ITO- and IO-induced pulmonary lesions were milder in mice than those previously reported in rats, and the fibrotic lesions were different between these two species. Indium levels in the lung and pooled blood were analyzed in the mice exposed to ITO and IO for 13 wk. In the 13-week inhalation exposure of mice to ITO, alveolar proteinosis and significantly increased lung weight were induced at the same exposure concentration as the current threshold limit value for indium and its compounds.

View full abstract