Air Conditioning Use and Heat-Related Deaths: How a Natural Disaster Presented a Unique Research Opportunity.

The aftermath of the Great East Japan Earthquake and resulting tsunami of 11 March 2011 provided researchers an unexpected opportunity to explore the relationship between air conditioning and risk of heat-related death.1 Many earlier studies reported associations between access to and/or use of air conditioning and lower mortality risk.23456 However, the new results, published in Environmental Health Perspectives, suggest that limiting the use of air conditioning during summer heat may not necessarily have adverse consequences for human health.1

The 2011 earthquake and tsunami severely damaged the Fukushima Daiichi Nuclear Power Plant and caused severe electrical shortages in the Tokyo metropolitan area. To conserve energy, the government strongly encouraged residents served by Tokyo Electric Power Company and Tohoku Electric Power Company to reduce electricity consumption by 15% from July to September of 2011.7

Campaigns promoting energy conservation have long been a summertime fixture in Japan.14 But the sudden loss of the Fukushima Daiichi Nuclear Power Plant in 2011 gave a new urgency to reducing energy consumption. Among other measures, many residents swapped air conditioning for fans. Image: © Associated Press.

In the new study, a team led by professor Masahiro Hashizume of Nagasaki University compared the number of heat-related deaths in Japan in 2011 and 2012 to the number reported between 2008 and 2010. In 13 of the 15 prefectures with the greatest drop in electrical consumption, the researchers estimated that heat-related deaths did not increase but instead decreased by 5–9%. The prefectures with less change in electricity consumption also saw little change in risk of heat-related death.1

In Japan, 90% of households have air conditioners.8 Before the Fukushima earthquake, an estimated 53% of the electricity consumed during the peak hours in summer went toward running air conditioners.7 The restrictions on electrical use after the disaster are estimated to have reduced overall household summer electricity consumption by up to 18%.7

A mass media and online public information campaign9 urged people to set their air conditioners to 28°C (82°F), to run them less, and to switch to electric fans. People also were advised to drink more water, dress in cool clothing, wear hats outdoors, and use blinds and curtains to block sunlight. Businesses allowed far more casual work attire than usual and shifted hours of operation to cooler times. Lights were dimmed in public areas, workplaces, and stores.10

About two-thirds of households changed their energy use habits, whereas only 4% of households bought and installed newer energy-efficient air conditioners.11 “This suggests that behavioral changes, rather than technological measures, were a primary reason for the reductions in household electricity consumption,” says Hashizume. “Public information campaigns seem quite effective to raise people’s awareness about how to prevent heat-related illness.”

By one estimate,12 air conditioning around the world consumes 1 trillion kilowatt-hours of electricity yearly, and the use of air conditioning could increase 10 times by 2050 in response to rising temperatures. This anticipated surge in power production likely will add to greenhouse gas emissions and promote global-scale climate change, while the “waste heat” put off by air conditioning units will additionally warm urban areas.13

More research is needed to determine whether the Japanese experience could help guide prevention of heat-related deaths of people living elsewhere. “It is unknown whether similar public service campaigns, without the backdrop of a natural crisis, would change behaviors and reduce energy use as effectively,”cautions Hashizume.

David Hondula, an assistant professor at Arizona State University’s Urban Climate Research Center, who was not part of the study, says the insights into human adaptive capacity and behavior are encouraging. “Understanding how people cope with the coupled hazards of extreme heat and power failure is important in an era of increasing temperatures and demands on urban infrastructure,” Hondula says. “The new finding that heat-related mortality did not increase, despite electricity limitations, suggests that we need to re-evaluate the importance of air conditioning versus other adaptive strategies as determinants of heat-related health risks.”