6.2 Health impacts of climate change

Extensive studies have been conducted to investigate the health impacts of climate change (Barratt et al., 2022; Romanello et al., 2023; WHO, 2022a, 2022b, 2022c, 2023b, 2023c, 2024). Climate change affects health at individual and population levels, both physically and mentally (Ebi & Hess, 2024). Its health impacts result from disruptions to a wide range of social norms, encompassing environmental, social, economic, health and technological domains (Jagals & Ebi, 2021).

People have already witnessed the health impacts of climate change through extreme weather events and wildfires that lead to temperature-related illnesses such as heat stress, as well as flooding, ecological disruption and precipitation-related illnesses such as vector-borne diseases (Ebi & Hess, 2024). Older people, women and children are particularly vulnerable to these climate events events (WHO, 2015a, 2019b, 2021b, 2023b). For example, the 2023 Lancet Countdown on health and climate change report revealed an 85 per cent increase in heat-related deaths among people older than 65 years compared to the levels observed between 1990 and 2000, a significantly higher rate than the estimated 38 per cent growth under no climate change conditions (Romanello et al., 2023).

What is less noticeable is the increased risk of common illnesses resulting from incremental increases in ambient temperature. For example, a one-degree Celsius increase in ambient temperature is associated with a 1.05 relative risk of preterm birth and a 1.02 relative risk of cardiovascular disease related mortality (Ebi & Hess, 2024). Additionally, a one-unit increase in ‘days with maximum temperatures in the 99th percentile relative to median temperature’ is associated with a 1.07 relative risk of schizophrenia morbidity (Ebi & Hess, 2024). Climate change has led to the expansion of territories with temperature ranges that maximise the performance of vectors (such as mosquitoes) and pathogens (such as some Vibrio pathogens), increasing the incidence of arboviral diseases such as dengue and West Nile fever (Ebi & Hess, 2024; Romanello et al., 2023). Furthermore, climate change is accompanied by increased exposure to airborne allergenic pollen, leading to an increase in the incidence and severity of respiratory symptoms (Ebi & Hess, 2024).

Climate change is associated with food insecurity, including disruptions to food supply, quality and safety, as well as population displacement due to factors such as rising sea levels and social conflict (Ebi & Hess, 2024). Extreme drought has become more common globally, affecting 47 per cent of the land area between 2013 and 2022 compared to 18 per cent between 1951 and 1960 (Romanello et al., 2023). Additionally, extreme weather events such as floods and wildfires can disrupt transportation and supply chains (Jagals & Ebi, 2021), further jeopardising food supply. Worsening living conditions and economic losses resulting from climate change force many people to flee their homelands.

Climate change is often accompanied by air pollution, which can lead to serious health consequences, including cancer, cognitive decline and suicide (Zhang et al., 2024). An increase of 10 µg/m³ of wildfire-specific fine particulate matter pollution (PM2.5) is associated with a 1.015 relative risk of same-day all-cause mortality (Ebi & Hess, 2024). The 2023 Lancet report estimated that 1.9 million deaths annually are associated with PM2.5 derived from the burning of dirty fuels, including fossil fuels and biomass, while exposure to indoor air pollution is associated with 78 deaths per 100,000 people (Romanello et al., 2023).

The changing behaviours of people because of climate change also have health implications. For example, a study conducted in China revealed that poor air quality discouraged internal migrants from visiting health facilities (Liu et al., 2022). Additionally, people may reduce outdoor physical activities in response to heatwaves (Romanello et al., 2023) and air pollution (Yu et al., 2021).

The health impacts of climate change are not equally distributed across populations. People with low socio-economic status and those living in low- and middle-income countries bear the disproportionate brunt of these impacts. Climate change detrimentally alters physical and social environments and damages health-supporting infrastructure, exacerbating poor living conditions and hindering access to healthcare in resource-poor communities (Jagals & Ebi, 2021). Globally, resource-poor countries are disproportionately impacted by climate change in terms of socio-economic development, while having the least capacity to adapt to its health effects, as their healthcare systems are already strained by the consequences of climate change (Romanello et al., 2023). In Asia and Africa, heat-related labour loss averaged 143 labour hours per worker in 2022 (Romanello et al., 2023).

In summary, climate change influences health and healthcare services through a variety of direct and indirect paths. It can lead to health losses via extreme climate events and pollution, expand the impact zones of infectious disease, exacerbate chronic physical and mental conditions, decrease quality of life, increase health and socio-economic disparities, and jeopardise the effectiveness of health efforts. Recent studies have revealed an association between climate change (increased ambient temperature) and the development of antibiotic resistance in healthcare settings (Li et al., 2023). The value of healthcare services cannot be realised without adequately addressing the challenge of climate change.