Updated: Sep 22
The link between climate change and human health is an issue that is only partially understood by the wider public. Climate change has many effects on human health, some are fairly obvious, while others are barely known or researched. Climate change is driving more numerous and more severe extreme weather events such as heatwaves, flooding and hurricanes. Each of these types of events result in major health problems in both the short and long term.
The scope of health threats which are being driven by climate change is incomparable to anything else. Whether acute or chronic, infectious or autoimmunity activated, affecting the young or the old, the poor or the rich, the already sick or the healthy, a staggering range and number of diseases and health concerns are climate-driven and already, humans worldwide are suffering the effects of the climate change crisis. The sheer number of people these public health issues concern makes climate change the largest influencing and potentially alterable factor impacting health in the 21st century, and indeed, perhaps ever.
Global warming has raised the temperature of the Earth by 1.1 °C since the 1800s (Allen et al., 2022). As the world is made up of integrated ecosystems, this change has had astronomical effects – the emergence of extreme droughts, raging fires, water scarcity, melting ice caps, rising sea levels and extensive flooding. This has had devastating consequences; extinction of species, lost ecosystems and biodiversity, death, illness, and the forging of a new group of vulnerable people labelled climate refugees. Even if we set aside the ethical and social issues surrounding climate change, we have vastly underestimated the scope of issues for public health.
The rising sea level and heavier rainfall has led to flash floods, which are now the most common type of climate-driven disaster. Water contamination is an enormous problem. Chemical contaminants such as pesticides and heavy metals have been found to have consequential effects on the maturation and growth of children. Damage to sewage infrastructure results in drinking water becoming contaminated with sewage – this gives rise to water-borne pathogens. In the Bangladesh flooding, diarrhoeal disease due to water contamination was the most common cause of death (Mallett and Etzel, 2018).
Heatwaves are a well-documented feature of climate change. The May 2015 heatwave in India demonstrated the detrimental effects of this, with over 2,200 fatalities attributed to heat exposure alone. They found a 16% increase in mortality when the temperature exceeded 40°C and concluded that exposure to such temperatures has not only physical, but also behavioural and psychological impacts (Rathi and Sodani, 2021). Furthermore, extreme heat events can trigger cardiac arrests and disproportionately affect those with existing heart conditions, of which there are 7.6 million people in the UK alone (British heart foundation, 2022). 85% of studies in a meta-analysis found a significant link between higher temperatures and a greater risk of being born prematurely (Chersich et al., 2020) Moreover, at higher temperatures, there was a greater incidence of stillborn babies (Chersich et al., 2020).
Hurricanes cause damage to infrastructure, resulting in interruptions in health care. This affects people in both the short term; where injuries from the hurricane itself cannot be adequately treated, but also in the long term, where routine drugs for example blood pressure and routine check-ups for pregnant women are not available. Following hurricane Katrina, shelters lacked supplies meaning roughly 50% went without their much-needed medications (Waddell et al., 2021). The direct health threats include electrocution, drowning, crush, and other traumatic injuries. Maternal health was greatly affected, with an increased likelihood of preterm delivery. This was also accompanied by a surge in postpartum mental health issues. Again, following hurricane Katrina 18% of mothers were found to be depressed and 13% were being treated for PTSD (Waddell et al., 2021). For weeks afterwards, women also experience issues getting access to contraception and STI screening. More subtle issues have been documented, such as a rise in domestic and sexual abuse.
Less well documented, is the effect climate change has on air pollution. It is well established that air pollution exacerbates respiratory conditions, increases your risk of cancer and strokes and is the cause of an estimated 36,000 deaths a year (Public Health England, 2018). Climate change is aggravating this health issue through its effect on ozone, an air pollutant. Rising temperatures increase the ground level concentration of ozone, which is directly correlated with increased deaths from respiratory causes (Jerrett et al., 2009). Studies have also identified increasing ambient ozone levels with rising incidences of COPD, respiratory tract infections and asthma exacerbations (Orru et al., 2013).
ALLERGIES & AUTOIMMUNITY
Next, the climate-compelled rise in allergies and autoimmunity. Climate change is thought to not only exacerbate those with pre-existing allergies but also trigger allergies and autoimmunity in disease-naïve individuals. Reports have found that an increase in both the intensity and duration of the pollen season is as a direct result of climate change (Ray and Ming, 2020). This will cause increased morbidity to the 400 million people in the world suffering from allergic rhinitis (Scarupa and Kaliner, 2005). Furthermore, food allergies have been similarly impacted, with a 21% increase in peanut allergies in the US between 2010 and 2017 (Ray and Ming, 2020). Climate change is also accountable for the surge in autoimmune diseases, which was ranked the 6th most common underlying cause of death in females in 2003 (Thomas et al., 2010). The upward trend in autoimmunity has been attributed to climate change’s alterations on the antibodies we are exposed to, which increases molecular mimicry, a route cause of immunologic diseases (Ray and Ming, 2020).
The referenced medical studies make it very clear that the climate crisis will affect many many more of the world's population, than is believed by most people. To quote Sir David Attenborough “ We are at a unique stage in our history. Never before have we had such an awareness of what we are doing to the planet; and never before have we had the power to do something about that. The future of humanity and indeed all life on Earth, now depends on us”.
Allen, M., Dube, O., Solecki, W., Aragon-Durand, F., Cramer, S., Humphreys, S., Kainuma, M., Kala, J., Mahowald, Y., Mulugetta, R., Perez, R., Wairiu, M., & Zickfield, K. (2022). Framing and Context. In Global Warming of 1.5°C (pp. 49–92). Cambridge University Press. https://doi.org/10.1017/9781009157940.003
British heart foundation. (2022). Facts and figures.
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Orru, H., Andersson, C., Ebi, K. L., Langner, J., Åström, C., & Forsberg, B. (2013). Impact of climate change on ozone-related mortality and morbidity in Europe. European Respiratory Journal, 41(2), 285–294. https://doi.org/10.1183/09031936.00210411
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Rathi, S., & Sodani, P. (2021). Summer temperature and all-cause mortality from 2006 to 2015 for Hyderabad, India. African Health Sciences, 21(3), 1474–1481
Ray, C., & Ming, X. (2020). Climate Change and Human Health: A Review of Allergies, Autoimmunity and the Microbiome. International Journal of Environmental Research and Public Health, 17(13), 4814. https://doi.org/10.3390/ijerph17134814
Scarupa, M., & Kaliner, M. (2005, June). In-Depth Review of Allergic Rhinits.
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