A two-part series on heat and health published in The Lancet warns that heat-related morbidity and mortality will likely increase without investment in evidence-based research and risk-management strategies.

The series brings together academic experts from epidemiology, physiology, medicine, climate science, built environment, and sustainable development with contributions from 15 authors from eight countries spanning four continents.

Professor George Havenith, of Loughborough University’s Environmental Ergonomics Research Centre (EERC), is one of the contributing authors and his team’s research into heat exposure has helped shape the series. 

The EERC team have examined the impact of ageing and the differences in temperature regulation in pre-pubertal children, the impact of heat on worker productivity in physical work with a focus on the impact of climate change, cooling interventions for workers in extreme conditions, and much more as part of the Heat-Shield project.

Co-led by Professor Ollie Jay from the University of Sydney (Australia) and Professor Kristie Ebi from the University of Washington (USA), the Lancet series argues prevention and planning must go together.

“This year’s hot weather in southern Europe and the US west coast has shown that climate change is not something that will happen only in the far future. The impacts are here today”, Professor Havenith explained.

“Loughborough’s research on the impact of heat and climate change on worker productivity has shown that apart from direct health effects, big economic effects can be expected with increasing heat, based on the substantial reductions in work output in the heat observed.

“That is why urgent action is needed on two fronts: one to fight further climate change occurring, and the second is to help regions and people affected by extreme weather to cope with the current and future temperature extremes.

“The paper’s overview of health impacts on one side and sustainable mitigating measures to cope with extreme heat, for different situations, like in schools, workplaces care homes, etc. will provide valuable information to those affected.”

What are the health risks of extreme heat?

Failure to reduce greenhouse gas emissions and to develop and deploy heat action plans will mean a very different future awaits many people and communities around the world.

Day-to-day summer activities may change dramatically as increasing warming means people are at greater risk of exposure to intolerable heat far more often, particularly in tropical regions.

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 catastrophic 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 due to a limited behavioural adaptive capacity (e.g., isolated at home, 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.

“Extremely hot days or heat waves that were experienced approximately every 20 years will now be seen more frequently and could even occur every year by the end of this century if current greenhouse gas emissions continue unabated. These rising temperatures combined with a larger and older population, mean that even more people will be at risk for heat-related health effects,” said Professor Ebi.

Evidence-based and sustainable cooling strategies

The authors argue that the global community and policy makers should look beyond short-term solutions that might be convenient but do not promote long term resilience. Planning must also consider those that are most economically and clinically vulnerable to extreme heat.

While air conditioning is set to become the most widely adopted heat reduction strategy worldwide, it is unaffordable for many, and is financially and environmentally costly, potentially leaving many defenceless during power outages.

They highlight accessible and effective cooling strategies at the individual, building, and urban and landscape level and recommend tailored approaches for specific settings where people may be particularly vulnerable to the effects of extreme heat including care homes, unplanned settlements, workplaces, schools, mass gatherings, refugee camps, and sports play.

In the series, the authors highlight actions individuals can take to cool themselves down and blunt other types of physiological strain that arise from regulating body temperature to combat health risks from extreme heat.

Effective and sustainable strategies include:

• electric and misting fans
• self-dousing with a water spray or sponge
• wearing wet clothing
• immersing feet in cold water
• short breaks from physical activity
• remaining well hydrated (the temperature of water consumed has little consequence)
• modifying clothing or protective equipment to improve ventilation.

Adaptations to buildings can help cool indoor environments. These include external coatings to reflect heat away from buildings and green walls to reduce surface temperatures, improved insulation and glazing, and better ventilation through and around buildings.

Features of the urban environment and surrounding landscape also influence conditions in built-up areas. Lakes, large grasslands and parks, and shaded outdoor areas, as well as reducing pollution within cities, are important.

To protect populations, heat action plans, which include early warning and response systems and robust surveillance and monitoring, must include evidence-based cooling strategies.

Professor Jay said: “We are fortunate that advances in research and technology now allow physiologists to simulate human exposure to different heatwave scenarios in climate chambers, providing us with scientific evidence that can inform low cost and effective cooling strategies for different circumstances.

“Integrating this evidence-based information into heat action plans that are robust, communicated well to the public, and informed by real-time surveillance will provide optimal health protection into the future. Currently, many heat-health action plans are not supported by evidence, and this urgently needs to change – it will save lives.”

For more information on the series, click here.

To find out more about Loughborough University’s Environmental Ergonomics Research Centre, click here.