2021 has been hailed the ‘make or break’ year in the fight against climate change. While the physical effects of climate change are more actively researched, there is a huge void of evidence concerning its impacts on health.[1] The direct effects of climate change on health are easier to consider, however, health, in large part is influenced by the social determinants of health.[2],[3] We hypothesise that any climate-linked disruption to the social gradient may indirectly affect healthcare outcomes. This makes climate change a pressing issue to address. Here we will provide an overview of the potential effects of climate change on health.
Hotter summers and heat waves are commonly associated with climate change. Both have been linked to heat-related disorders, exacerbations of cardiovascular, respiratory, and chronic diseases. A disproportionate amount of morbidity and mortality is seen in elderly people, people living alone, urban populations and those without air conditioning.[4] The disproportionate effects don’t stop there. The Global South contribute only 8% of excess carbon dioxide emissions, but weather-related natural disasters are 80 times more likely compared to the Global North.[5] This includes an increased number, intensity, and duration of droughts which in turn has huge effects on poor and marginalised people. Often, they lack socioeconomic resilience to withstand natural weather disasters, access to preventative and reactive services. We hypothesise that more frequent weather disasters may lead to income shortage, food insecurity, structural conflict, lack of water and basic amenities, eventually leading to adverse health outcomes.
Over the years, pictures of smog from industrial cities in India and China have gained a lot of attention worldwide. Smog is composed of nitrogen oxides, sulphur oxides, ozone, smoke, and other particulate matter. High levels of fine particulate matter (PM2.5) in smog poses a huge health risk.[6] Increased PM2.5 levels have directly led to an increased number of lung-related diseases including asthma exacerbations and lung cancer. While the exact mechanisms of its action are not known, epigenetic and microenvironmental alterations seem to play a part in lung cancer, while PM2.5 induced cytokine release and oxidative stress may aggravate asthma.[7] In the west, geographical differences due to urban planning have meant deprived communities are more likely to be affected by air pollution-related diseases compared with more affluent communities. They often live closer to busy roads and have less access to green space thereby experiencing a higher disease burden.[8]
New emerging infections have been propelled in frequency by the effects of climate change. Vector-borne diseases (VBDs), water-borne diseases (e.g., cholera), soil-borne and food-borne pathogens have emerged as a direct consequence of climate change.[9] Regarding VBDs, vector biting rates have increased with temperature up to a certain threshold. This has caused the development and transmission of vector transmitted pathogens to increase.[10],[11] The novel SARS-CoV-2 virus has also been linked to climate change; however, this is purely speculative. The mechanism involves changes in sunlight, temperature, and carbon dioxide levels leading to changes in vegetation growth, causing the migration of new bat species from forests (natural habitat) to new areas.[12] Climate can also indirectly act through socioeconomic factors e.g., flooding can destroy disease prevention measures including vector control.[13]
Climate change is likely to discriminately impact hungry and undernourished people due to the substantial risk it poses to food security. Computer modelling has shown that a high spatial variation in crop yields could arise depending on the degree of latitude a country is situated at.[14],[15] This is most likely going to affect the Global South first, causing their crop yields to decrease, followed by the Global North last. The Global South coincidentally have higher pre-existing hunger and undernutrition rates, which makes this a key issue to consider. The risk of mortality and morbidity due to starvation and malnutrition is likely to increase.
In this article, we’ve highlighted a few examples of the deleterious effects that climate change may have on health. It is imperative that we mitigate against these effects by cutting down our carbon emissions, protecting green spaces and cutting down consumption/waste. We encourage policymakers to use social justice reasoning when considering policies that may affect the environment and for individuals to rethink their micro-decisions on a consumer level. ‘We are all in this together’ is a phrase often used to denote the shared responsibility and equal magnitude of the climate crisis worldwide. But this is simply not true. When likened to the sinking Titanic, the Global North are getting evacuated while the poorer Global South are locked in the hold. We must act now.
[1] Kwon, H.-J., 2020. Climate Change and Health: More Research Is Still Needed. Journal of Preventive Medicine & Public Health, pp. 1-2.
[2] Marmot, M. & Allen, J. J., 2014. Social Determinants of Health Equity. American Journal of Public Health, Volume 104.
[3] Word Health Organization, n.d. Social Determinants of Health. [Online]
Available at: https://www.who.int/health-topics/social-determinants-of-health#tab=tab_1
[Accessed 22 May 2021].
[4] Levy, B. S. & Patz, J. A., 2015. Climate Change, Human Rights, and Social Justice. Annals of Global Health, 81(3), pp. 310-322.
[5] EM-DAT, 2015. The International Disaster Database. [Online]
Available at: https://www.emdat.be/index.php#pager
[Accessed 22 May 2021].
[6] Mukherjee, A. & Agrawal, M., 2017. A Global Perspective of Fine Particulate Matter Pollution and Its Health Effects. Reviews of Environmental Contamination and Toxicology, Volume 244, pp. 5-51.
[7] Li, R., Zhou, R. & Zhang, J., 2018. Function of PM2.5 in the pathogenesis of lung cancer and chronic airway inflammatory diseases. Oncology Letters, 15(5), pp. 7506-7514.
Marmot, M. & Allen, J. J., 2014. Social Determinants of Health Equity. American Journal of Public Health, Volume 104.
[8] Ferguson, L. et al., 2021. Systemic inequalities in indoor air pollution exposure in London, UK. Buildings & Cities, 2(1), pp. 425-448.
[9] McIntyre, K. M. et al., 2017. Systematic Assessment of the Climate Sensitivity of Important Human and Domestic Animals Pathogens in Europe. Scientific Reports, Volume 7.
[10] Scott, T. W. et al., 2000. Longitudinal studies of Aedes aegypti (Diptera: Culicidae) in Thailand and Puerto Rico: blood feeding frequency. Journal of Medical Entomology, 37(1), pp. 89-101.
[11] Reisen, W. K., Fang, Y. & Martinez M., V., 2006. Effects of temperature on the transmission of west nile virus by Culex tarsalis (Diptera: Culicidae). Journal of Medical Entomology , 43(2), pp. 309-317.
[12] Beyer M., R., Manica, A. & Mora, C., 2021. Shifts in global bat diversity suggest a possible role of climate change in the emergence of SARS-CoV-1 and SARS-CoV-2. Science of The Total Environment, Volume 767.
[13] Boyce, R. et al., 2016. Severe Flooding and Malaria Transmission in the Western Ugandan Highlands: Implications for Disease Control in an Era of Global Climate Change. The Journal of Infectious Diseases, 214(9), pp. 1403-1410.
[14] Parrya, M. et al., 2004. Effects of climate change on global food production under SRES emissions and socio-economic scenarios. Global Environmental Change, 14(1), pp. 53-67.
[15] World Bank. 2010. World Development Report 2010: Development and Climate Change. Washington, DC. © World Bank. https://openknowledge.worldbank.org/handle/10986/4387 License: CC BY 3.0 IGO
Jatin Naidu is a medical student studying at University College London. His interests lie in fighting healthcare inequalities and designing equitable healthcare systems. He is currently working on a novel SARS-CoV-2 test and doing COVID-19 research at Great Ormond Street Hospital for Children. You can find him on ResearchGate, or more informally on Twitter.
