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LETTERS: Robert M Wolfe Death in heat waves: Beware of fans... BMJ 2003; 327: 1228-b [Full text]

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Death in heat waves

william r keatinge   (8 December 2003)

Death in heat waves 8 December 2003
william r keatinge, professor emeritus Barts and the London School of medicine, Queen Mary College,Road, London E1 4NS Send response to journal: Re: Death in heat waves	DEATH IN HEAT WAVES Editor- Although air movement alone will not always prevent heat stroke in air close to body temperature if the air is saturated (1) or if sweating is impaired, for example by drugs with anticholinergic actions (2), air movement is an essential component in prevention of heat stroke. The advice offered recently (3) specifically related to heat stress in Britain over the next decade, and included not only a fan but moistening of clothing, open window, light clothing and avoidance of physical exertion. Moistening of clothing substitutes for sweat. In moving air this allows evaporative cooling even of people with impaired sweating and in air warmer than body core temperature. In British (and most other) heat waves, outdoor air is well short of saturation. Relative humidity was 22% near Faversham when the record temperature of 38.5C was recorded there last summer. Air conditioning can virtually eliminate heat related mortality even in a subtropical climate (4). However, its capital cost and energy consumption are high, and it is not widely installed in countries like Britain where high temperatures are infrequent. Once heat stress does occur, cool baths are effective, but repeated immersion is less likely to be acceptable to elderly and ill people than moistening of exposed skin and air movement from an open window. In case of doubt there is a simple test of whether this or any other measure is helping. If it makes people feel cooler and more comfortable, it almost certainly is. The design and management of buildings for hot weather is a different, but important, issue. As Pauleau (5) points out, buildings can warm more slowly than outdoor air during the day, and closing windows for part of the day will then help. However, solar radiation, and heat production by people and by cooking, can make buildings warm faster than outside air. Closed windows then accelerate the warming, as well as letting humidity rise. Sunlight entering through windows, high occupancy, and low thermal mass and insulation are major factors promoting rapid warming. A lounge with picture windows and full of elderly people on a sunny day is a particular risk, even if the people in it are shaded from direct sunlight. Incidentally, outdoor slatted shutters are more effective than indoor curtains against solar heating. The shutters prevent radiation entering the building to produce greenhouse warming, while indoor curtains do not. William R. Keatinge, Professor Medical Sciences Building, Bart’s and The London Medical School, Queen Mary and Westfield College, Mile End Road, London E1 2AD w.r.keatinge@qmul.ac.uk 1 Wolfe RM. Death in heat waves. BMJ 2003;327:1228.. 2. Kilbourne EM, Choi K, Jones TS, Thacker SB, and the field investigation team. Risk factors for heat stroke: a case control study. JAMA 1982;247:3332-6 3. Keatinge WR Death in heat waves. BMJ 2003;327:512-3. 4. Donaldson GC, Keatinge WR, Nayha S. Changes in summer temperature and heat related mortality since 1971 in North Carolina, South Finland and Southeast England. Environ Res 2003;91:1-7. 5. Pauleau A. Death in heat waves. BMJ 2003;327:1228-9. Competing interests: None declared