北海道における熱中症の発生状況と建設現場におけるファン付き作業服の有効性に関する研究動向

桒原 浩平

doi:10.20683/jniph.74.2_137

Abstract

北海道労働局の2017～2024年の熱中症事例を用いて北海道における職場の熱中症発生の状況を分析した．北海道における職場の熱中症発症者数は，屋外で約63％と屋外での発生割合が高い．屋外では11時と14～15時に二つの発生ピークがあることから，14時頃に短時間の休息を取り入れることも対策の一つになると考えられる．また外気温が26℃を超えたあたりから1日で複数名が発症する可能性を示唆した．作業中の発生状況について，屋外で最も記載頻度の高い用語は「草刈り」関係の用語で，屋内では「工場」，「ビニールハウス」があった．建設業や製造業だけでなく農林業従事者への熱中症対策の啓発も必要である．次にファン付き作業服に関する著者らの研究をレビューし，その有効性について現在の知見をまとめた．人工気候室にて統一した温熱環境下で建設作業員12名を対象とした被験者実験では，長袖Tシャツの上にファン付き作業上着（以降，VWJ）を着用した条件と長袖Tシャツのみ着用の条件で生理心理反応を比較した．34℃の環境ではVWJを着用した方が平均皮膚温や着衣残留汗量が有意に低値を示した．また東京都内の建設現場にて建設作業員7名を対象とした屋外現場実測では，同じ気温でもVWJを着用した方が長袖Tシャツのみの場合よりも平均皮膚温は有意に低下，暑さ感と快適感の関係もVWJ着用時の方が有意に快適であることを示した．人工気候室と現場実測のデータを基に飲水とVWJ着用の効果について検証した結果，建設作業員の飲水密度はスポーツ活動中の運動部員と比べると大幅に少ないこと，建設現場でのVWJ着用は脱水率の低減に有効であることが示された．VWJ着用に加え適切な飲水を行えばより有効な熱中症対策となる．最後にWBGTが23～28℃の範囲内ではVWJ着用が有効である可能性が示唆された．

Translated Abstract

We analyzed the occurrence of heat stroke in workplace in Hokkaido, using heat stroke cases from the Hokkaido Labor Bureau from 2017 to 2024. During this period, 510 cases of heat stroke occurred in workplaces in Hokkaido, 63% of which occurred outdoors. Since there are two peaks in the number of heatstroke cases outdoors, at 11:00 and between 14:00 and 15:00, taking a short rest around 14:00 is suggested as a countermeasure. When the outside temperature exceeds 26°C, several people may suffer heat stroke in a single day. The most frequently mentioned terms in the text on the occurrence of heat stroke during work were terms related to "mowing" outdoors and "factory" and "plastic greenhouse" indoors. It is necessary to raise awareness of heat stroke prevention among construction and manufacturing workers, and among those working in agriculture and forestry. We also reviewed research on fan-equipped work clothes and summarized findings to date on their efficacy. In an experiment with 12 construction workers in a standardized thermal environment in an artificial climate room, physiological and psychological responses were compared between conditions in which ventilated working-jacket (VWJ) was worn over a long-sleeved T-shirt and those in which only a long-sleeved T-shirt was worn. At 34°C, mean skin temperature and clothing sweat content were significantly lower when VWJ were worn. In an outdoor field test of seven construction workers at a construction site in Tokyo, mean skin temperature was significantly lower for workers wearing VWJ than for those who wore only long-sleeved T-shirts in the same air temperature. The relationship between thermal and comfort sensations was significantly stronger among those wearing VWJ. These studies revealed that drinking water intake among construction workers was much lower than that among athletes during sports and that wearing VWJs at construction sites effectively reduced the dehydration rate. Provision of an appropriate volume of drinking water and mandating VWJ use effectively reduces the risk of heatstroke. These results suggest that wearing VWJs may be effective in WBGTs within 23–28 °C.

References

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