Extreme heat is a clear and growing health issue

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Extreme heat is an increasingly common occurrence worldwide, with heat-related deaths and illnesses also expected to rise. The authors of a new two-paper Series on Heat and Health, published in The Lancet, recommend immediate and urgent globally coordinated efforts to mitigate climate change and increase resilience to extreme heat to limit additional warming, avoid permanent and substantial extreme heat worldwide, and save lives by protecting the most vulnerable people.

In alignment with the Paris Agreement, the Series authors call for global warming to be limited to 1.5°C to avoid substantial heat-related mortality in the future. Reducing the health impacts of extreme heat is an urgent priority and should include immediate changes to infrastructure, urban environment, and individual behaviour to prevent heat-related deaths. The Series is published ahead of this year’s COP26 UN Climate Change Conference in Glasgow, UK.

Effective and environmentally sustainable cooling measures can protect from the worst health impacts of heat. These range from increasing green space in cities, wall coatings that reflect heat from buildings, and widespread use of electric fans and other widely available personal cooling techniques that have been shown by thermal physiologists to help people regulate their body temperature without exacerbating other types of physiological strain. While air conditioning is becoming more widely available around the world, it is unaffordable for many of the most vulnerable, is financially and environmentally costly, and leaves many defenceless against extreme heat during power outages.

“Two strategic approaches are needed to combat extreme heat. One is climate change mitigation to reduce carbon emissions and alter the further warming of the planet. The other is identifying timely and effective prevention and response measures, particularly for low-resource settings. With more than half of the global population projected to be exposed to weeks of dangerous heat every year by the end of this century, we need to find ways to cool people effectively and sustainably,” says Series co-lead author Professor Kristie Ebi from the University of Washington, USA.

According to a new Global Burden of Disease modelling study, also published in The Lancet, more than 356,000 deaths in 2019 were related to heat and that number is expected to grow as temperatures rise worldwide. However, Series authors note, many heat-related deaths are preventable by mitigating climate change and reducing exposure to extreme heat.

When exposed to extreme heat stress, the body’s ability to regulate its internal temperature can be overwhelmed, leading to heat stroke. In addition, physiological thermoregulatory responses that are engaged to protect body temperature induce other types of physiological strain and can lead to cardiorespiratory events. Effects from extreme heat are also associated with increased hospitalisations and emergency room visits, increased deaths from cardiorespiratory and other diseases, mental health issues, adverse pregnancy and birth outcomes, and increased healthcare costs. Older people and other vulnerable people who may be less able to take care of themselves in extreme heat (e.g., people isolated at home, people who have poor mobility) are also more likely to experience the health effects of extreme heat.

Extreme heat also lessens worker productivity, especially among the more than 1 billion workers who are exposed to high heat on a regular basis. These workers often report reduced work output due to heat stress, many of whom are manual laborers who are unable to take rest breaks or other measure to lessen the effects of heat exposure.

 Finally, warming temperatures are exacerbating other environmental challenges, including adverse ground-level ozone concentrations, wildfires, and rapid urban population growth.

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