There is growing concern over the possible increase in mental health problems among Japanese workers. This trend is generally regarded as a reflection of Japan's prolonged economic depression and changes in working environment. In fact, claims for compensation for industrial accidents related to mental health diseases have been rapidly increasing in recent years. Working hours, personal-relationships, support from supervisors/co-workers, job demand, job control, and payment are known to affect workers mental health. In 2004, the Government announced a guideline to combat overwork and mental health problems at work places. This guideline articulates that long overtime working is a major indicator, and workers who work over 100 h overtime in a month should be encouraged to see an occupational physician. This guideline takes into account the practicalities of occupational health at work places and the empiric knowledge that long working hours might associate with workers mental health status. It may be reasonable to assume that long working hours affect workers health status both psychologically and physiologically, interacting with a variety of occupational factors, particularly job stress. However, the association between working hours and workers mental health status has not been fully clarified. The present article aimed to provide a systematic review of the association between working hours and mental health problems. The authors conducted a systematic review of the published literature on the association between working hours and mental health problems using PubMed. Of 131 abstracts and citations reviewed, 17 studies met the predefined criteria. Ten of these are longitudinal studies, and the others are cross-sectional studies. Seven of the 17 studies report statistically significant associations between working hours and mental health problems, while the others report no association. In addition, comparison among these studies is difficult because a variety of measurements of working hours were used. The present review found inconsistent results in the association between working hours and mental health burden.

Environmental Health, Japan-Objectives: Measuring core body temperature is crucial for preventing heat stress disorders in workers. We developed a method for measuring auditory canal temperatures based on a thermocouple inserted into a sponge-type earplug. We verified that the tip of this thermocouple is positioned safely, allowing the wearer to engage in normal physical tasks; this position averaged 6.6 mm from the tympanic membrane. Methods: To assess this technique, we had six healthy male students repeat three cycles of exercise and rest (20 min of exercise and 15 min of rest) in a temperaturecontrolled chamber with temperatures set at 25, 30, or 35°C, while monitoring the auditory canal, esophageal, rectal, and skin temperatures. Results: We observed differences of a mere 0.30-0.45°C between rectal temperatures and auditory canal temperatures measured with the thermocouple, the smallest such difference reported to date in studies involving auditory canal temperature measurement. Conclusions: We conclude that monitoring temperatures based on a technique involving an auditory canal plug can be used to estimate rectal temperatures accurately, and thereby to avoid conditions leading to heat stress disorders. Although controlling ambient temperatures is the ideal approach to eliminating heat stress disorders, this is often not possible. This makes it especially important to optimize work schedules by reducing hours worked, providing workers with frequent breaks, or having workers work in alternating shifts. Ideal work schedules should be based on evaluations of physiological response, including perspiration rates and heat balance, as defined in the ISO7933 Predicted Heat Strain model 1) . In practice, however, measuring the parameters required for this model poses major difficulties. The indices available for workplace evaluations include various proxies for core temperature (t cr ) measurements, including measurements of skin temperature (t sk ), heart rate (HR), and body weight. Monitoring t cr in vivo is essential to preventing heat disorders.According to ISO 9886 2) , the term "core" refers to all tissue located at depths sufficient to remain unaffected by the temperature gradient existing on surface tissue. Esophageal temperature (t es ), rectal temperature (t re ), intraabdominal temperature (t ab ), oral temperature (t or ), tympanic temperature (t ty ), auditory canal temperature (t ac ) and urine temperature (t ur ) have been proposed as core temperature indices. The transducer of t es is placed in the lower part of the oesophagus, which is in contact over a length of 50 to 70 mm with the front of the left auricle and with the rear surface of the descending aorta. Consequently, t es reflects the temperature of the arterial blood with a very short reaction time. t re is independent of ambient conditions because the rectum is surrounded

The dissociation constant of the complex formed in the mixed and very dilute surfactant solution of 3-(dodecylammonio)-propionate (NDA) and sodium alkylsulfates (C10, C12, C14) (SAS) was determined by measuring surface tension and adsorbed amounts of the solution. The composition in the surface and bulk phases did not coincide at the equimolar mixture. The adsorbed monolayer on the solution consists of the coadsorption of NDA–SAS complex (1:1) and free NDA, while the adsorption of free SAS was almost zero in various concentrations studied. Under these conditions the surface activity of the complex alone was obtained. The relationship between the surface activity and bulk concentration for each mixed solution was discussed in terms of relative adsorbability. The surface activity of the complex was one order of magnitude higher than that of NDA and two orders higher than that of SAS.

No abstract

Health, Japan-Envisioning a cooling method and aiming at maximum feasibility and simplicity, we designed an experimental intervention-control study based on non-refrigerated water usage, consisting of pouring 2 l of 23.0°C water simultaneously on head and hands for one minute, after every 20 min of exertion. The subjects were 11 fit male individuals between 19 and 26 yr old. Each individual participated in one control and one intervention measurement in a climatic chamber at 35°C and 60% humidity (31.5°C WBGT) on different days. Heart rate, rectal, esophageal, skin and external ear canal temperatures were monitored constantly. Each experiment consisted of 10 min of basal recording followed by 3 intervals of 20 min of cycling and 15 min of rest. Stabilometry and visual reaction time tests were performed before and after each resting period. A questionnaire evaluating equilibrium, concentration, alertness and tiredness was administered at the beginning and at the end of every experiment. Paired t-test analysis revealed significant improvements in subjective parameters (all p<0.05), as well as skin (p<0.05), external ear canal (p<0.01) and esophageal (p<0.05) temperatures during the rest periods. Repeated measurement analysis of variance revealed significant cooling in all the aforementioned temperatures except the esophageal temperature (p=0.28). Other parameters were not significantly different. Our findings indicate that this method has subjective and physiologic positive effects, and thus can be used as a complementary low cost method to cool subjects safely. (J Occup Health 2008; 50: 251-261)