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But there are simpler solutions, too. Last week, the respected medical journal Lancet published a largely overlooked paper about humble technology that can do a lot to help solve the problems of extreme heat: the electric fan.
As everyone knows, fans have been used for centuries to move air around and help you feel cooler (in China, hand fans date back to the 8th century). But in recent years, electric fans have gotten a bad rap. The Environmental Protection Agency warns, portable electric fans are not the simple cooling solution they appear to be. From the World Health Organization: In severe heat, fans can add to the level of heat stress, in particular when ambient humidity is high. Also from the WHO: There is no scientific consensus on the efficacy of fans.
The fear is that fans create what amounts to a convection oven for people. As hot air blows across body, it can increase heat stress. The gist of most public health recommendations that are in place today is that when it gets above 95 F, fans do more harm than good.
But Nate Morris, a researcher at the University of Copenhagen and the lead author of the Lancet paper, argues in the new study that these guidelines are not based on sound science. In fact, Morris and his co-authors make the case that in most circumstances and for most people, fans are a cheap, easy, low-power relief from extreme heat.
In the study, researchers used biophysical models to create combinations of temperature and humidity to see when using a fan would worsen heat stress for three groups of people: healthy young adults (aged 18 40 years), healthy older adults (aged 65 years and older), and older adults taking anticholinergic medication, a class of drugs used to treat Parkinson s Disease and other conditions. These age groups were selected because the ability to sweat is reduced by 25 percent in older adults, and is decreased by a further 25 percent in people on anticholinergic medication. Heat stress thresholds for these three groups were then compared with hourly hot weather data for 108 cities around the world between January 1st, 2007, and December 31st, 2019.
The study found that the effectiveness of fans depends on both temperature and humidity. Basically, in hot, humid conditions, the fan helps more because the blowing air helps sweat evaporate faster, which accelerates cooling. In hot, arid climates, sweat evaporates easily, so fans are less helpful and, at extreme temperatures, can indeed increase heat stress. Nevertheless, during the 12-year period the study covered, it found that electric fan use would have provided cooling benefits for 96.6 percent of all hot weather days for young adults, and 94.9 percent of days for healthy older adults and older adults taking anticholinergic medication.
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