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The Impact of Climate Change on Global Health

By Stephanie Foster, PAM Group

Published 21 December 2021

The recent UN Climate Change Conference (COP26) in Glasgow has drawn a spotlight on the impact of human activity on the climate. Within the scientific community, it is readily accepted that our reliance on fossil fuels, the loss of natural habitats and large-scale farming is causing a substantial rise in greenhouse gasses resulting in a rise in global temperature.

The start of the industrial revolution 150 years ago has been used as a benchmark, with the planet’s temperature having risen by one degree Celsius since then, with the stark prediction that the temperature will continue to escalate without intervention.1 The prediction is that we will continue to experience an increase in the frequency and severity of adverse weather conditions. 2 This includes heatwaves, colder winters, drought, increased episodes of heavy rainfall, storms, and high winds. So, from an OH perspective how might this impact our health and work here in the UK?
Heatwaves, where temperatures exceed 25 to 28oC for at least 3 consecutive days often accompanied by high humidity, will become more frequent. As cities and built environments both produce and retain heat, they are on average 5 degrees hotter than the surrounding countryside.2 As heat rises, south high-rise flats or offices, especially those with large unshaded windows can experience problems with overheating. In the UK more focus has been given to reducing heat loss from our buildings rather than considering cooling. While insulation can help reduce the amount of heat entering the building, as well as heat loss in cooler times, it can also reduce the dissipation of heat. This in conjunction with the retained heat built environments both produce and retain heat, they are on average 5 degrees hotter than the surrounding As heat rises, south-facing rise flats or offices, especially those with large unshaded windows can experience problems with overheating. In the UK more focus has been given to reducing heat loss from our buildings rather than considering cooling. While insulation can help reduce the amount of heat entering the building, as well as heat loss in cooler times, it can also reduce the dissipation of heat. This in conjunction with the retained heat released back into the environment, can result in elevated temperatures at night. This can adversely affect sleep patterns causing fatigue and associated issues such as reduced productivity and an increased level of accidents. Opening a window is often the initial method used to reduce the ambient temperature. This is a measure that is encouraged to help reduce the spread of COVID by improving ventilation. However, a cooling effect can only occur if the outside air temperature is lower than that inside. When it is not, it can have the opposite effect, increasing indoor temperatures.

Employers may need to reconsider how they achieve both good ventilation and maintain an acceptable working temperature in this scenario. Mechanical alternatives such as a fan or air conditioning, can both help and hinder. Some industries have the added complication of having heat dependent processes, exacerbating the situation even further e.g., kitchens, laundries, or foundries.

Although there is no current maximum working temperature set in legislation, Workplace, Health, Safety and Welfare Regulations state that employers must maintain “a reasonable temperature.”3, productivity within office workers has been shown to decrease above 23-24oC.4 As we experience more sunshine, outdoor workers may experience increased UV exposure and therefore be at an ever-increasing risk of developing skin cancer. They also do not necessarily have the protection of shade or easy access to fluids, while also being more likely to be carrying out physical activity. Consequently, they, like pregnant women and those with a disability or underlying health issues are more vulnerable to the impact of heat and to developing a heat-related illness.5 The HSE have a dedicated microsite to temperature, which has detailed advice on eliminating, reducing or mitigating the associated risk through a hierarchical approach to implementing appropriate control measures.6

The NHS website describes symptoms of heat exhaustion as:

• a headache
• dizziness and confusion
• loss of appetite and feeling sick
• excessive sweating and pale, clammy skin
• cramps in the arms, legs and stomach
• fast breathing or pulse
• a high temperature of 38C or above
• being very thirsty

Increased temperatures can also exacerbate existing health conditions. For example, most people with Multiple Sclerosis (MS) report experiencing increased issues with fatigue, blurred vision, balance, and cognitive issues when feeling over-warm or hot.7
Hot weather can also impact blood glucose control for people with diabetes, increasing the risk of hypoglycaemia due to a combination of better insulin absorption and dehydration. Sweating to regulate temperature and heat-related fatigue can also make it harder to recognise hypoglycaemic warning signs.8

Higher temperatures can also impact on cardiovascular, renal, and respiratory conditions. In very hot weather the heart must work harder to maintain the body’s core temperature within optimal levels. Those with pre-existing cardiovascular conditions are less able to accommodate the vasodilation required to achieve this.9 The consequence is reduced blood flow and oxygenation of the major organs, potentially resulting in failure.

Heat stress can affect kidney function and is thought to be a contributing factor in the development of chronic kidney disease. Heat stress and dehydration are also considered to be contributing factors in the formation of kidney stones. While not drinking sufficient fluids can increase the risk of urinary tract infections.10 Heatwaves are associated with an increased mortality rate. If nothing changes it is expected by 2050, we will experience a 250% increase in heat-related deaths to around 7,000 a year, predominantly affecting the elderly.11
There is also some evidence of an increased mortality rate amongst those taking medications to treat mental health issues, possibly due to side effects such as the suppression of thirst and altered levels of perspiration.12 Going forward, it may be that we need to consider the risk caused by heat exposure for a wider range of employees and work settings, not just those who are exposed to a heat-generating process.

When considering the impact on respiratory function, higher temperatures are associated with a reduction in air quality, as strong sunshine increases ozone and pollution levels. It is believed that warming will increase levels of pollen and fungal spores and that these may also trigger allergic reactions more readily. The hay fever season is predicted to become longer and to increase the frequency and severity of asthma attacks.13 Current advice is for hay fever sufferers to keep windows closed. It will be interesting to see how this competing demand to keep windows open to aid ventilation as a COVID secure measure can be managed. This may be another area where home working, where it can be accommodated, allows for personalised environment management to meet an individual’s health needs.

As the climate warms there is an increased risk of drought and consequently wildfires, the impact of the particulates produced has an impact on lung function, exacerbating chronic respiratory disease. There is also evidence of the increased frequency of strokes and heart attacks in the vicinity of these fires.14 While those who are fighting the fires will be provided with appropriate PPE and indoor workers advised to close windows and stay inside, outdoor workers in the area may be exposed to higher levels of particulates. If the air quality is sufficiently affected, employers may need to consider PPE to mitigate the risk.

Periods of drought and conversely increased risk of flooding from high levels of rainfall impact agriculture and yields.1 Poor harvests result in higher prices increasing the food insecurity already prevalent. We already have extensive evidence that this is a contributing factor in the development of health inequalities. Higher temperatures may also increase the prevalence of vector-borne diseases. For instance, increasing temperatures have increased the prevalence of ticks and mosquitoes. However, if the climate continues to warm, we may also experience an influx of more exotic species and associated pathogens. There may be COSHH (Control of Substances Hazardous to Health) implications as new chemical controls may have to be developed to manage this.

Occupational Health specialists are in the unique position of being able to consider the health impacts of climate on the working population and how an individual employment might affect their exposure and personal risk.

Due to melting glaciers and ice flows, sea levels are anticipated to rise. This may put coastal regions at risk of flooding. I was surprised to find that Cardiff is considered the 6th most at-risk city in the world of flooding, while London is 22nd.15 Increased periods of heavy rainfall are also having an impact with some areas becoming prone to repeated flooding. While we are all aware of the economic impact of this, we may not have considered the psychological impact. Research has shown this does not just occur at the time of the flood but that there is an increased prevalence of Post-Traumatic Stress Disorder and depression in those affected by flooding up to 3 years later.16 There is often limited statutory support to deal with the clean-up and restoration following such events, which can take many years. Due to increased moisture, this can lead to an increase in mould growth increasing respiratory problems. Businesses, as well as homes, can be flooded affecting the economic and mental health of communities due to long layoffs. In 2005 The McVities factory in Carlisle was flooded causing a 6-month national shortage of bourbon biscuits until the factory could be made operational again.

In this country, we are more used to considering the impact of cold rather than hot weather. The very recent storm Arwen has highlighted the adverse impact of both the cold and high winds, with 3 people, unfortunately, losing their lives when their vehicles were hit by falling trees. Parts of Scotland have been without electricity for over 7 days as power lines have been brought down by the weight of snow and ice. It is not just the amount of infrastructure damage that is causing delays to reconnection, but environmental conditions. Working in cold conditions, like extreme heat can impact health, limiting how long workers can be operational as regular rest breaks to warm-up are required. Vasoconstriction to help maintain core body temperature can impact the cardiovascular system increasing the risk of heart attacks and strokes. It can also increase the risk of cold injury to the extremities and impact manual dexterity.

A study by the TUC has highlighted that most employers have experienced increased absenteeism associated with adverse weather events, be that due to health, travel or infrastructure issues. While 70% acknowledge the health and safety implications and risks to their workforce from future climate change.17

Occupational Health specialists are in the unique position of being able to consider the health impacts of climate on the working population and how an individual’s employment might affect their exposure and personal risk. We can have a key role in helping to interpret the science, raise awareness and support individuals and businesses in their attempts to mitigate the health impacts of climate change. I hope that this article may have helped to spark discussion and reflection on how climate change is already impacting our health and may still do in the future.


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3. The Workplace (Health, Safety and Welfare) Regulations 1992.
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13. Vardoulakis, S. and Heaviside, C., 2012. Health effects of climate change in the UK 2012. London: Health Protection Agency. [online] Available at: Climate change: health effects in the UK GOV.UK ( [Accessed online 21/11/2021]
14. Anchor. 2021. OccPod: Climate Conversations – Episode 21, Wildfires and Environmental Hazards by OccPod: the official ACOEM podcast. [online] Available at: acoem/episodes/OccPod-ClimateConversations–Episode-21-Wildfires-and-Environmental- Hazards-e1a3qit [Accessed 6 December 2021].
15. 2021. 2050 Climate Change City Index | Nestpick. [online] Available at: [Accessed 6 December 2021].
16. GOV.UK. 2021. Mental health costs of flooding and erosion. [online] Available at: [Accessed 6 December 2021].
17. 2021.Changing Work in a Changing Climate [online] Available at: [Accessed 6 December 2021].

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