The effects of working hours on health were examined taking psychological job strain into account. White-collar workers employed at the main office of a Japanese manufacturing company provided data for analysis done in 1997. The eligible subjects were 286 workers aged 20-39. Causal relationships between working hours, health, and psychological job strain were examined by covariance structure analyses. The main findings were as follows: Not only working hours but also sleeping hours and vacations affected the workers’ effort to deal with work as a work-related hour factor. Decision authority and skill discretion of Karasek’s psychological job strain items significantly constituted a discretion in the work factor, and this factor moderated the effects of the work-related hour factor on health. The effects of psychological job strain, especially discretion, must always be taken into account in examinations of working hours and health.
Thirty-seven nurses with shift work, working under a rotating three-shift system, and 37 nurses without shift work, having worked during the daytime for one or more years prior to this study, were examined to assess the effects of shift work on cardiac autonomic and neuromotor functions. Their ages ranged from 25 to 58 yr. The electrocardiographic (ECG) R-R interval variability, %LF and %HF (i.e., proportions of sympathetic and parasympathetic activities, respectively), and LF/HF ratio were computed by means of autoregressive spectral and component analyses. The %LF and LF/HF ratio were significantly larger in the nurses with shift work than in those without shift work, although there was no significant difference in the heart rate-corrected QT interval on ECG between them. And, hand-ear coordination differed significantly between the nurses with shift work and those without. Despite the presence of potential selection bias, it is suggested that shift work in nurses may cause not only a long-term sympathodominant state but also some neuromotor impairment.
Protective effects of prednisolone as a synthetic adrenal cortical hormone and complex of vitamin B1, B2, B6 and B 12 on organophosphorus compound-induced delayed neurotoxicity (OPIDN) caused by leptophos and tri-o-cresyl phosphate (TOCP) as organophosphates (OPs) were examined. Nine groups of hens (six for each) were used. Eight groups received intravenous injection of 30 mg/kg of leptophos or 40 mg/kg of TOCP (four groups in each). Among them, three groups which received leptophos were given (p.o.) predonisolone (2 mg/body), vitamin B complex (25 mg/body) or both 3 h after OPs injection and then every day for 15 d (one group for each); the same treatment was performed on three groups which received TOCP. The remaining one group served as controls. It was observed that delayed neuropathy induced by OPs could not be resisted completely by the treatment with prednisolone or vitamin B complex, but clinical signs of OPIDN and pathological changes in hens that received these two protective agents after OPs were less severe than those in hens that received only OPs. Of these groups, the improvement in clinical signs was best shown in hens that received the both two protective agents. In addition, improvement in clinical signs among the hens that did not deteriorate to paralysis was observed. In particular, those which developed mild ataxia recovered well. It is indicated that combining administration of prednisolone and vitamin B complex early before clinical signs are manifest is effective in alleviating neuropathy. It is also suggested that recovery or good prognosis will be expected, as long as progression of the clinical signs is prevented before paralysis develops in delayed neuropathy.
The association between cigarette consumption and prevalence of mild proteinuria (30-99 mg/dl of albumin) was analyzed in 11,569 male and 4,715 female workers aged 18-67 yr recruited from an occupational population. Proteinuria was found in 274 (2.4%) of the total male workers and in 50 (1.1%) of the total females. Stepwise logistic regression analyses showed that sex, suspected diabetes mellitus, blood pressure (BP) and Brinkman Index (BI) levels (0, 1-199, 200-499, 500-799, 800-) were significantly related to proteinuria, and that the odds ratio of each BI level for proteinuria was 1.11 (C.I.: 1.01-1.67). In the subjects aged 50 yr or older, after excluding those suspected of having hypertension and/or diabetes mellitus, the odds ratio reached 1.37 (C.I.: 1.15-1.63), with the gender difference then no longer significant. The odds ratio for proteinuria was calculated as 5.44 (C.I.: 2.27-13.0) in male and female smokers having a BI of 500 or above and normal-high BP (130-139/85-89 mmHg) in comparison with nonsmokers having normal BP (<130/85 mmHg). These results suggest that heavy cigarette consumption represented by a BI of 500 or above is a risk factor of proteinuria even in healthy Japanese workers, particularly in those aged 50 yr or older and having normal-high BP.
This paper aims to investigate the work-related factors that affect whether Japanese male employees will seek a medical diagnosis after being screened for diabetes mellitus. Participants in this study received a questionnaire two months after receiving the results of their physical checkup. The analysis focused on 213 regular employees of small and medium-sized companies who were aged 35-64 and who had tested positive for diabetes in a screening. Only 42% of the subjects visited a doctor for medical diagnosis during an average follow-up period of 47.5 d. Cox’s proportional hazard regression was used to analyze the length of time between the employees’ receipt of the results and their first visit to a doctor’s office. The employees who could comfortably take a day off, compared to those who found it difficult to do so, were more likely to visit a doctor (hazard ratio (HR) 1.94; 95% confidence interval (CI) 0.85, 4.42; p for trend 0.05). In addition, employees with a high level of psychological job control, compared to those with low level of job control, were more likely to visit a doctor (HR 1.80; 95%CI 0.94, 3.45; p for trend 0.08). Employees who worked the longest (61 h per week or more) were less likely to visit a doctor than those working from 41 to 60 h weekly (HR 0.41; 95%CI 0.17, 0.98). The findings suggest that a flexible work schedule, autonomy at work, and no excessive working hours tend to improve the chance of visiting a doctor after screening for diabetes mellitus.
The effect of lung burden on biopersistence and histopathological changes caused by potassium octatitanate whiskers (POW) which is one of the asbestos substitutes were investigated for 1-yr and 4-wk inhalation periods. In the 1-yr inhalation experiment, male Wistar rats were exposed to POW (TW) for 6 h/d, 5 d/wk under the same conditions as a previous study of POW (PT1, JFM fiber) which is made by different manufacturer. The exposure concentration was 1.9 ± 0.7 mg/m3 and the mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) in the chamber were 1.6 μm and 2.9. Rats were sacrificed at 3 d and 1 yr after the inhalation experiment and TW deposits in the lungs were determined by ICP-AES. Lung burden at 3 d and 1 yr after the inhalation was 2.39 ± 0.50 mg and 1.37 ± 0.96 mg, respectively, the deposition fraction was 8.1% and biological half time (BHT) was 15 months. Aggregated dust cells and mild fibrotic changes around these dust cells were observed in the exposed rat lung. These results were almost the same as those obtained in the previous 1-yr PT1 study. In the 4-wk inhalation experiment, to investigate the effect of lung burden on biopersistence and histopathological change, male Wistar rats were exposed to PT1. The exposure concentration was 102 ± 21 mg/m3, MMAD (GSD), the geometiric mean length and diameter (GSD) of the PT1 in the chamber were 1.6 μm (3.0), 2.2 μm (1.8) and 0.33 μm (1.5), respectively. Rats were sacrificed at 3 d, 1 wk, and 1, 3, 6 and 12 months after the inhalation experiment. The lung burden of POW at 3 d after 4 wk inhalation was 1.49 ± 0.19 mg, which was close to the estimated amount of overload. The BHT of the total mass (4.1 months) was not prolonged, but aggregated dust cells were observed in the subpleural region and around the bronchioles and mild fibrotic changes were observed only around the dust cells at one year after the 4-wk inhalation. It is considered that the excessive exposure which impairs the function of alveolar macrophage mediated clearance may cause the aggregation of dust cells and fibrotic changes.
The number of native Dutch and Turkish workers receiving a permanent disability pension in the Netherlands is still rising. To assess ethnic differences in disability risk between Dutch and Turkish scaffolders, a retrospective study was conducted within a large scaffolding company. Medical files for the period 1981-2000 were used to gather information on ethnicity, age at entering service, age at becoming disabled, years of employment, the year to receive a disability pension, the disability diagnosis, and the percentage rating of the disability pension. In the past 20 yr, 131 Turkish and 125 Dutch scaffolders have become disabled. Musculoskeletal disorders were the primary reason for the diagnosis. No differences in diagnoses were observed, except for a small difference in cardiovascular disease. Turkish scaffolders started their work at an older age, received the disability pension at an older age, and had a longer duration of employment. Turkish scaffolders faced disability 2.48 (95% confidence interval 1.94-3.18) times more often than their Dutch colleagues, adjusted for age. Explanations for the differences in disability risk between Dutch and Turkish scaffolders are sought in the older age at start of employment, lower mobility in the labour market, and less access to medical and social care. In future, employers, general practitioners, occupational health physicians and social security workers, as stakeholders in reintegration, should sufficiently attune their activities concerning care and cure for Turkish construction workers on long-term sick leave or during reintegration into other work.
It has been speculated that dentists are at high risk for occupational exposure to bloodborne viruses such as hepatitis B and hepatitis C viruses. To assess the risk of the development of liver cancer among Japanese male dentists, we conducted a retrospective cohort study on 3,314 dentists of the Osaka Dental Association who were members between 1964 and 1985, the year before HBV immunization became available. By linking to the Osaka Cancer Registry, we found that during the period of 1964-1997, 36 of the dentists were diagnosed with liver cancer over a mean follow-up of 23.6 yr. The observed number of liver cancer cases was compared with the expected number, which was calculated by multiplying the number of person-years at risk by the corresponding age- and calendar time-specific incidence rate from the Osaka Cancer Registry data. The male dentists had a significantly lower risk of developing liver cancer than the general population of Osaka (O/E=0.71, 95% CI=0.50-0.98). On subcategorical analysis by birth year or duration of follow-up, there was no significantly increased risk of developing liver cancer among the dentists. Contrary to our expectation, our findings indicate that Japanese dentists were not at increased risk of developing liver cancer compared with the general population.
The vibration conditions to which tractor operators are subjected are complex and varied with multi axis translation and rotational vibration inputs to different parts of the body. Working under such conditions may lead to human fatigue and other driving related hazards. The present research was carried out to study the operators under varying conditions of vibration while driving a tractor with and without farm equipment on different fields. Test runs were conducted in wet and dry fields to determine the levels of vibration generated at different engine speeds. On the basis of this study three levels of vibration namely 2.5, 3.5 and 5.0 m/s2 were selected. Five subjects, all males, with no experience in the field of tractor driving participated in the study. The data were analyzed on the basis of three factor repeated measure kind of experimental design. The results showed that the main effects of farm equipment and the vibration level were statistically significant but the effect of field type was found to be statistically non-significant. The results of the study call upon the ergonomists to design and develop a tractor where the driver may be relieved of vibration induced stresses. Front loading of farm equipment is recommended for improved visibility and better working posture.
To evaluate the effects of the occupational exposure to rayon manufacturing chemicals (RMC, containing predominantly carbon disulfide (CS2) and minor sulfuric acid) in a rayon factory on the basal transepidermal water loss (TEWL), barrier integrity (BI), and sequential increasing TEWL profiles. Six Thais and five Chinese workers in the spinning department of a rayon manufacturing plant and five healthy unexposed controls were recruited as the test subjects. An area of 4.5 × 5.5 cm on the mid-side of the volar forearm on the right hand was stripped by means of moderate pressure with commercially available adhesive tape by the same technician throughout the experiment. The skin was progressively stripped until glistening. TEWL was measured at every three and five tape strips on the right hand. The corresponding site on the left hand was measured parallel as the self-control. We found significant differences in basal TEWL and in BI between Chinese workers and Chinese controls, and between Thai workers and Chinese workers, respectively. Two-stage patterns of progressive TEWL profiles were found in such a chronic and repeated occupational exposure to RMC containing CS2. The occupational exposure to RMC could result in the perturbation of the skin barrier function. Basal TEWL might be more sensitive to chronic skin irritant exposure. The TEWL profile achieved to the glistening stage might be necessary to avoid erroneous pattern estimation. Due to the lack of Thais control in this study, the racial difference in response to the RMC warrants further study.
This study presents the results of an investigation of respiratory symptoms, pulmonary function and chest X-ray examinations, and analysis of antibodies to fungi of 197 tussah silk-processing workers and 40 control workers. An industrial hygiene survey and environmental mycological studies were also conducted. The dust concentrations in tussah silk processing workshops were less than 5.1 mg/m3 on average, with a maximum of 7.8 mg/m3 below the national health limit of 10 mg/m3. Most dusts in all tussah silk processing workshops contained less than 1.2% silica. Numbers of isolated fungi in tussah silk processing workshops [755-6,544 cfu/m3 (colony forming unit/m3), were significantly higher than those in control environments (63-472 cfu/m3). The prevalences of respiratory symptoms in tussah silk processing workers were higher than those in control workers. The prevalences of respiratory symptoms in exposed male non-smoking workers were 44.4% with chronic cough, and 38.9% with chronic phlegm respectively, which were significantly higher than those (12.5%, 12.5% respectively) in male non-smoking control workers (p<0.05). The prevalences in exposed male smoking workers were 42.9% with dyspnea, and 38.1% with chest tightness respectively, which were significantly higher than those (16.7%, 8.3% respectively) in male smoking control workers (p<0.01). The prevalences of respiratory symptoms in exposed female workers were 25.3% with chronic cough, 38.0% with chronic phlegm, 31.0% with dyspnea, and 29.1% with chest tightness respectively, which were significantly higher than those (10.0%, 10.0%, 10.0%, 5.0% respectively) in female control workers (p<0.01). Fifteen exposed workers often suffered from fever. Five X-rays were abnormal and four cases had nodular or patchy shadows. The prevalences of pulmonary function abnormalities in the exposed female group were significantly higher than those in control groups (p<0.01). The OD450nm values for antibodies to fungi in tussah silk processing workers were significantly higher than those of control workers (p<0.05). The positive rates of anti-fungal antibodies in tussah silk-processing workers were also significantly higher than those of control workers (p<0.01). The results suggested that fungi might be one of the main allergens in respiratory diseases in the tussah silk processing workers.