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Volume 47 (2010)
- Issue 4 Pages 139-
- Issue 2 Pages 69-
- Issue 1 Pages 3-
Volume 47, Issue 4
Displaying 1-5 of 5 articles from this issue
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Original Articles
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—Thermal physiological meaning of WBGT proposed by Yaglou et al.—Tohru Mochida, Tomonori Sakoi2010 Volume 47 Issue 4 Pages 139-148
Published: 2010
Released on J-STAGE: December 17, 2010
JOURNAL FREE ACCESSThe Wet-Bulb Globe Temperature (WBGT) is a thermal index that is widely used to prevent heat disorders. It was proposed by Yaglou et al. on the basis of experimental data obtained from members of the U.S. Army. In our previous studies, we examined the characteristics of Yaglou’s WBGT assuming that a wet-bulb thermometer was placed in a sufficiently ventilated location and the influence of long-wave radiation and solar radiation was negligible. Then, we derived new WBGT equations represented by WBGT=0.84Tw+0.30Tg−0.08Ta (applied outdoors in direct sunlight) and WBGT=0.85Tw+0.21Tg (=Ta) (applied indoors in the absence of direct sunlight).
In the present study, we adopt an assumption adopted for the measurement of Yaglou’s WBGT in that the wet-bulb thermometer is placed in a naturally ventilated location where the effects of long-wave radiation and solar radiation should be considered. Then, on the basis of transformations of heat-balance equations, we derive more precise WBGT equations, represented by WBGT=0.94Tw+0.16Tg−0.07Ta (applied outdoors in direct sunlight) and WBGT=0.94Tw+0.10Tg (=Ta) (applied indoors in the absence of direct sunlight). We confirmed that in the case in which the natural wet-bulb thermometer is used in the measurement of Tw, the coefficient of Ta practically takes a negative value. This is because the increase in Ta corresponds to the decrease in humidity. We also confirmed that when Tw refers to the naturally ventilated wet-bulb thermometer, the coefficient of Tw must be greater than that in the case in which Tw refers to the sufficiently ventilated wet-bulb thermometer.
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Ryo Ito, Naoyuki Yamasita, Masataka Nakano, Saimi Yamamoto, Takaaki Ma ...2010 Volume 47 Issue 4 Pages 149-156
Published: 2010
Released on J-STAGE: December 17, 2010
JOURNAL FREE ACCESSDecrease in body temperature and increase in energy expenditure would occur when human expose in rain and wind. We investigated that the effect of rain and wind on thermal and metabolic responses during walking. Seven men completed a 30 min walking protocol on the treadmill at a walking velocity of 1 m/s in a dry thermoneutral condition (CON), a rainy condition (RAIN) and windy condition (WIND). The environmental temperature was set at 24°C in the three conditions. Relative humidity was 50% except RAIN (80~90%RH). In this experiment, 30 mm/h of the precipitation and 3 m/sec of the wind were set under RAIN and WIND conditions, respectively, during walking. In addition, 1 m/sec of the wind that is equal to the walking speed was set under RAIN and CON conditions. During the walking, rectal temperature (Tre) gradually increased in each condition, but weighted mean skin temperature (Tsk) in RAIN and WIND drastically fell by about 4°C and were significantly lower than in CON throughout the exercise. Over the rest and exercise period, there was no significant difference in oxygen consumption, heart rate, rating of perceived exertion and blood lactate concentration among three conditions. These results indicate that thermoregulatory and metabolic responses were not affected by rain and wind during walking in the thermoneutral condition. Exercise induced heat production and peripheral vasoconstriction may be sufficient to offset heat loss due to rain and wind.
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Hideo Ohno, Naoki Nishimura, Kuniyuki Yamada, Yuuki Shimizu, Satoshi I ...2010 Volume 47 Issue 4 Pages 157-164
Published: 2010
Released on J-STAGE: December 17, 2010
JOURNAL FREE ACCESSWe tested a hypothesis that minus-ionized water vapor particles ranging 20 to 70 nm in diameter are absorbed in the stratum corneum and penetrate along pathways with a 50 nm width between corneocites, and, further, form a thin film of sebum lipids over the skin surface, thus contributing to improve the hydration state of the skin surface. Accordingly, we investigated skin conductance with SKICON-200 (IBS Co. Ltd) and transepidermal water loss (TEWL) with VapoMeter (Delfin Co. Ltd) in 19 healthy adult females. In a climate chamber controlled at 24°C and 35% relative humidity, ionized water vapor particles were generated by the instrument. Measurements were compared between the ionized water vapor conditions and the condition without water vapor (control). Skin conductance at the lateral canthus maintained virtually constant levels under the ionized water vapor conditions, while it gradually decreased under the control condition. TEWL of the cheek did not decrease under the ionized water vapor conditions, while it decreased under the control condition. These results indicate that water vapor particles of this size are easily absorbed and penetrate into the thin stratum corneum of the skin, such as the lateral canthus, to maintain the hydration state. On the other hand, ionized water vapor particles remain on the skin surface and diffuse outward over the skin with the thick stratum corneum.
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Shinichi Watanabe, Tetsumi Horikoshi, Akemi Tomita2010 Volume 47 Issue 4 Pages 165-173
Published: 2010
Released on J-STAGE: December 17, 2010
JOURNAL FREE ACCESSSolar absorptance of the clothed human body is an important factor in thermal comfort assessment of outdoor. The objective of this research is to identify solar absoprtances of clothed human body. Five male subjects were participated in the measurements. Combined short and long-wave radiometer and a pyranometer were used in the measurements. Four clothing ensembles were tested: black shirt and black trousers (B-B); black shirt and white trousers (B-W); white shirt and black trousers (W-B); white shirt and white trousers (W-W). Casual clothes were also tested. The following findings were obtained through the experiments. The measuring method in this research provides the adequate solar absorptance of clothed human body with various ensembles. The solar absorptance of the human body in a black shirt and black trousers (B-B) was 0.76, and 0.38 for a white shirt and white trousers (W-W). The solar absorptances in the ensembles of B-W, W-B, and the casual clothes were in the extent from 0.38 to 0.76.
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Akio Hoshi, Seiichi Nakai, Eiko Kaneda, Takashi Yamamoto, Yutaka Inaba2010 Volume 47 Issue 4 Pages 175-184
Published: 2010
Released on J-STAGE: December 17, 2010
JOURNAL FREE ACCESSUsing the vital statistics in Japan, we studied regional differences in mortality due to heat disorders, as well as differences between before and after 1995, the year of application of ICD (International Statistical Classification of Diseases and related Health Problems: 10th revision).
The number of deaths due to heat disorders during the 33 years from 1975 through 2007 was 5,877, or 178 per year. The mortality and age-adjusted mortality rate due to heat disorders after 1995 were significantly higher than those before 1994. In all age groups, the mortality rate was significantly higher after 1995, compared with before 1994. Concerning the place of death, the number of deaths due to heat disorders was higher after 1995 than before 1994 in all places except sports and athletics facility and other specified places.
Classified by prefectures, the highest mortality rate was shown in Akita, followed by Kagoshima and Gunma. On the other hand, it was lower in Kanagawa and Miyagi, and the lowest in Hokkaido. The age-adjusted mortality rate, eliminating the effect of the age distribution in each prefecture, was the highest in Okinawa, followed by Kagoshima and Gunma, while it was lower in Hokkaido, Kanagawa, and Nagano. The highest annual temperature, mortality rate, and age-adjusted mortality rate were significantly correlated, indicating that the highest annual temperature is one of the factors affecting regional mortality due to heat disorders.
In conclusion, the mortality and age-adjusted mortality rates due to heat disorders tended to be higher in areas along the Sea of Japan, and lower in areas along the Pacific Ocean in northern Japan, and were also higher in inland areas such as Gunma, Saitama, and Yamanashi Prefectures. On the other hand, these rates were higher in Okinawa and Kagoshima Prefectures, and lower in Hokkaido. These prefecture-specific differences in the mortality and age-adjusted mortality rates due to heat disorders are considered to be attributable to differences in the summer-time heat environment, the intensity of heat wave.
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