The The Lancet recently released "Series on Heat and Health". The author suggests that global coordinated action should be taken immediately to slow down climate change and enhance the ability to resist extreme high temperature, so as to limit further temperature rise, avoid permanent and severe extreme high temperature around the world, protect the most vulnerable people and save lives. Effective and environmentally sustainable cooling measures can avoid the most serious impact on health. Many high-temperature-related deaths can be prevented by slowing climate change and reducing exposure to extreme high temperatures.
The impact of extreme high temperature on health is increasing, and the number of deaths is increasing. As the global temperature continues to rise, these effects are expected to continue to deteriorate.
Mitigating climate change is necessary to prevent the temperature from rising further.
Even if the existing climate change mitigation policies are implemented, the global temperature will continue to rise, and it is urgent to improve the environmental sustainability of personal behavior and built environment to adapt to the increasingly hot world.
Extreme high temperature is becoming more and more common all over the world, and the deaths and diseases related to high temperature are expected to increase. The The Lancet recently released a Series on Heat and Health, which includes two articles. The author suggests that global coordinated action should be taken immediately to slow down climate change and enhance the ability to resist extreme high temperature, so as to limit further temperature rise, avoid permanent and severe extreme high temperature around the world, protect the most vulnerable people and save lives.
The author of the album article calls for the global warming to be controlled within the target of 1.5℃ consistent with the Paris Agreement, so as to avoid a large number of deaths related to high temperature in the future. It is urgent to reduce the impact of extreme high temperature on health, which should include immediate changes in infrastructure, urban environment and personal behavior to avoid high temperature-related deaths. The album was released before the 26th United Nations Climate Change Conference in Glasgow, England.
Effective and environmentally sustainable cooling measures can avoid the most serious impact on health. These measures include increasing urban greening, adopting wall coatings that can reflect the heat of buildings, and widely using electric fans and other available personal cooling techniques. Thermophysiologists have proved that these techniques can help people regulate their body temperature without aggravating other types of physiological stress. Although air conditioning is becoming more and more common all over the world, many vulnerable groups can’t afford it, and its economic and environmental costs are high, and many people can’t resist the extreme high temperature during the power outage.
Professor Kristie Ebi from the University of Washington, USA, the co-author of the album, said: "We need to take two strategic approaches in fighting extreme heat. One is to slow down climate change, so as to reduce carbon emissions and reverse the further warming of the earth. The second is to determine timely and effective prevention and response measures, especially for areas with scarce resources. It is estimated that by the end of this century, more than half of the world’s population will face dangerous high temperatures for several weeks every year, and we need to find sustainable and effective ways to cool people down. " [2]
She added: "If we can’t reduce greenhouse gas emissions and formulate and deploy evidence-based heat action plans, it means that many people and communities in the world will face a completely different future. Normal summer activities, such as outdoor exercise and outdoor work, may face great challenges, because climate warming means that people will be exposed to unbearable high temperatures more frequently, and this challenge will be even greater in the tropics. " [2]
Health risks of extreme high temperature
In the same period, The The Lancet published the latest Global Burden of Disease (GBD) model simulation study, pointing out that in 2019, more than 356,000 deaths were related to high temperature, and it is predicted that this number will increase as global temperature rises. However, the author of the album article points out that many high-temperature-related deaths can be prevented by slowing down climate change and reducing exposure to extreme high temperatures.
When exposed to extreme high temperature stress, the body’s ability to regulate internal temperature may be overwhelmed, leading to heat stroke. In addition, the physiological thermoregulation reaction to maintain body temperature will trigger other types of physiological stress and may lead to cardiopulmonary function events (see Paper 1 and Figure 1). The influence of extreme high temperature is also related to the following situations, such as the increase of hospitalization and emergency treatment, the increase of deaths due to heart and lung diseases and other diseases, mental health problems, adverse pregnancy and delivery outcomes, and the increase of medical expenses. The elderly and other vulnerable groups who may find it difficult to take care of themselves in extreme heat (such as home isolators and people with mobility difficulties) are more likely to suffer from the health effects of extreme heat.
Extreme heat will also reduce the productivity of workers, especially the billions of workers who are often exposed to high temperatures. These workers often report that high temperature stress leads to reduced work output, and many of them are manual workers, who can’t rest or take other measures to reduce the impact of high temperature exposure.
Finally, rising temperatures are aggravating other environmental challenges, including ozone pollution, forest fires, and the rapid growth of urban population.
Professor Ebi said: "If the current greenhouse gas emissions continue to increase, extreme high temperature weather or high temperature heat waves that only appear once every 20 years will appear more frequently in the future; By the end of this century, it may even happen every year. Rising temperatures and an increasing number of elderly people mean that more people will face health risks related to high temperatures. " [2]
Effective cooling strategies now and in the future
In order to cope with the above health effects, the author emphasizes the effective cooling strategies that can be taken at the personal, architectural, urban and landscape levels. They also suggested taking measures according to local conditions for specific situations, including nursing homes, densely populated urban areas, workplaces, schools, mass gatherings, refugee camps and sports venues, where people may be particularly vulnerable to extreme heat.
The author emphasizes that individuals can take some measures to cool themselves and reduce other types of physiological stress caused by regulating body temperature, so as to cope with the health risks brought by extreme high temperature. These measures include using electric fans and spray fans, wetting yourself with spray or water-soaked sponges, wearing wet clothes, and soaking your feet in cold water. There are also some simple but effective and environment-friendly strategies, such as temporarily stopping physical activity, keeping enough water (drinking cold water or hot water), and changing clothes or protective equipment to improve ventilation (see infographic).
The co-author of this study, Professor Ollie Jay from the University of Sydney, Australia, said: "The effects of extreme high temperature exposure on the body are an obvious and increasingly serious global health problem. If we think more about how to use innovative methods to cool our bodies instead of trying our best to cool the surrounding air, then we will have many sustainable and accessible options to mitigate the effects of high temperature exposure. " [2]
In addition to personal methods to reduce physiological high temperature pressure, adaptive adjustment of buildings can also help cool the indoor environment. These measures include the use of external coatings that can reflect heat from buildings and environmentally friendly walls to reduce surface temperature, improved insulation materials and glass windows, and better ventilation conditions in and around buildings. The characteristics of urban environment and surrounding landscape will also affect the situation of built-up areas. Lakes, large lawns and parks, outdoor shading areas and reducing pollution in cities are all very important.
In order to protect people’s health, the high temperature action plan needs not only early warning system, strong supervision and monitoring system, but also evidence-based cooling strategy.
Professor Jay said: "It is very important that the personal cooling strategy we recommend in the high temperature health action plan must be based on scientific evidence. After all, just making a plan is not enough; The content of the plan itself must be correct. The cooling strategies recommended in some existing high-temperature health action plans seem to come from traditional views. For example, these plans usually recommend avoiding sugary drinks and high-protein foods, and do not recommend using fans; However, research shows that using fans and other strategies (for example, wetting your body with water or wearing wet clothes) at higher temperatures is an effective cooling measure. Establishing an early warning system for extreme high temperature events, including evidence-based measures to protect vulnerable groups, and raising people’s awareness of the health risks caused by high temperature are the key to reducing the deterioration of health and death caused by current and future high temperature events. " [2]
Professor Jay added: "Under the influence of human activities, most of the population on the earth will inevitably face a greater risk of extreme high temperature in the future than now. Predictive research shows that with the increasing impact of climate change, if our society wants to survive and prosper in the future world with higher temperature, it must immediately deepen the research on the risk of extreme high temperature and increase the investment in corresponding measures. " [2]
The editorial of The Lancet published in the same period wrote: "[…] Action Plan provides measures to adapt to extreme high temperature, but it does not solve the root cause of extreme high temperature-greenhouse gas emissions. Only by preventing and adapting to the changing climate can we minimize the impact of temperature on health … But we are also faced with a dangerous situation, that is, the commitment to deal with the climate crisis will not be reflected in decisive actions and effective policies. [COP26] The leaders of the conference must provide a transformative regulatory framework, policies and inputs to ensure the sustainability of climate change mitigation and adaptation measures. The article published in The Lancet provides a strong scientific argument that the impact of high temperature on health cannot be ignored. "
Extreme temperatures are rising.
As mentioned in previous research reports, both high temperature and low temperature will lead to an increase in the number of deaths and poor health. The new global burden of disease study estimates that 356,000 people died from high temperatures. In addition, researchers estimate that 1.3 million deaths in 2019 were related to cold. This study links non-optimal temperature-related deaths with 17 specific disease causes, and emphasizes its correlation with the mortality of cardiopulmonary and metabolic diseases, as well as the correlation with external causes of death, such as interpersonal violence, self-harm, drowning and injury [3].
In most places, low temperature causes more deaths than high temperature. Since 1990, the number of cold-related deaths has increased by 31%. In contrast, the deaths attributable to high temperature increased by 74% during the study period, indicating that the mortality rate of extreme high temperature is rising, especially in the hotter regions of the world. The author points out that the study only uses the mortality data of nine countries, so the global estimation results may underestimate the impact of extreme temperature on areas with high temperature sensitivity and overestimate its impact on areas with low temperature sensitivity. In addition, this study lacks data on specific cause mortality in Europe, South Asia and Southeast Asia, and only includes data from one sub-Saharan African country.
Dr Katrin Burkart, a co-author of the study from the Institute of Health Indicators and Evaluation (IHME) of the University of Washington, said: "Where people live has a great influence on their risk of being exposed to extreme high or low temperature weather respectively. In most areas, low temperature has a greater impact on health. However, our analysis found that in some very hot places, such as South Asia, the Middle East and many parts of Africa, the harmful effects of extreme high temperature may far exceed the harm caused by cold. This is very worrying because the risk of exposure to high temperatures seems to have been steadily increasing in recent decades. " [2] END
NOTES TO EDITORS
The modelling study was funded by the Bill & Melinda Gates Foundation. It was conducted by researchers from the University of Washington, USA, University of British Columbia, Canada, and the Chinese Center for Disease Control and Prevention.
The Heat and Health Series was supported by funding from the University of Sydney, National Health and Medical Research Council, and New South Wales Government Department of Planning, Industry and Environment Climate Change, Australia. It was conducted by researchers from the University of Washington and Arizona State University, USA, Monash University, University of New South Wales, University of Sydney, and The Children’s Hospital at Westmead, Australia, University of Waterloo, Canada, University of Tsukuba, Japan, Loughborough University and London School of Hygiene and Tropical Medicine, UK, Shandong University, China, University of Copenhagen, Denmark, and ETH Zurich, Switzerland.
[1] The Paris Agreement: https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement
[2] Quote direct from author and cannot be found in the text of the Article.
[3] The study uses data from 64.9 million deaths across nine countries (Brazil, Chile, China, Colombia, Guatemala, Mexico, New Zealand, South Africa, and the USA), which spans 29% of the global population as well as approximately 95% of the inhabited global temperature range, and 79% of sociodemographic conditions. It identifies 17 causes of death related to both high and low temperatures ischaemic heart disease, stroke, hypertensive heart disease, cardiomyopathy and myocarditis, diabetes, chronic kidney disease, lower respiratory infection, chronic obstructive pulmonary disease (COPD), homicide, suicide, drowning, mechanical injuries, animal-, disaster-, road- and other transport-related injuries. The second part of the study extrapolates these data to provide global estimates.
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