Tackling the health impacts of climate change in the twenty-first century^*

* The winner of the 2017 Holdstock-Piachaud Student Essay Prize, in memory of Douglas Holdstock and Jack Piachaud who were for many years inspirational editors of this journal, were Nicholas Heng and Anna Nakamura. This is Nicholas Heng’s essay on Tackling the health impacts of climate change in the 21st century; Anna Nakamura’s winning essay will appear in the next issue.

Abstract

The turn of the twenty-first century has borne witness to the seemingly relentless march of climate change, with global mean temperatures and sea levels projected to rise significantly in the near future. Despite considerable improvements in healthcare, mortality rates and life expectancy worldwide over the past few decades, there is increasing evidence postulating the potentially adverse impacts of environmental alterations on health in more ways than one. These not only involve direct and indirect climatic-related health impacts, but also those modulated by human aspects. Undeniably, there is a pressing need to recognize these issues and come up with appropriate solutions to address them as much as possible. Fortunately, this has led to the development of a wide range of measures encompassing both adaptation and mitigation strategies, alongside the recent Paris accords which highlight renewed global resolve in tackling these challenges in a collaborative and coordinated manner. However, progress has been relatively muted, and whether these prove to be the turning point remains very much to be seen. Nonetheless, taking the above into consideration, there is little doubt about the gravity of the situation, and that much more needs to be done to integrate and bring society forward in this new era.

Keywords:

• Climate resilience
• climatic variability
• infectious disease
• air quality
• nutrition
• psychological well-being
• adaptation
• mitigation

Introduction

The turn of the twenty-first century has brought unceasing attention to the seemingly relentless progress of climate change, which has largely been attributed to anthropogenic contributions. With global mean temperatures likely to rise more than 1.5 °C, and sea levels predicted to increase 0.26–0.98 metres by 2100 (Stocker et al. 2013), there is little doubt about the escalation and severity of these processes, thereby underscoring the need to recognize their wide-ranging impacts on health and society. Despite improvements in healthcare, mortality rates and life expectancy worldwide over the past decades (WHO 2016a), there is increasing evidence that such environmental alterations can potentially exacerbate or even reverse these gains (Smith et al. 2014). Therefore, in this regard, research on climate-related health impacts has focused on three main factors, encompassing direct impacts modulated through climatic variability, indirect impacts modulated through natural systems affecting infectious disease burden and air quality, as well as those modulated through human aspects involving nutrition and psychological well-being. While the majority of countries have begun to ratify the Paris accord with pledges to regulate carbon emissions and enhance climate-resilient development (UNFCCC 2016), whether this proves to be the turning point remains very much to be seen. Taking the above aspects into consideration, devising viable solutions to adequately tackle these uncertainties is becoming all the more pertinent and relevant.

Direct impacts of climatic variability

Weather extremes

There has been mounting evidence associating climate change with extreme weather events (Guha-Sapir, Hoyois, and Below 2016), potentially leading to greater health risks and losses (Smith et al. 2014). Such events continue to dominate global headlines, including Cyclone Nargis in 2008, Hurricane Sandy in 2012, and more recently the 2016 floods in Louisiana and Typhoon Meranti, amongst others. Notably, floods and storms make up the bulk of natural disasters globally, affecting millions of people and causing significant mortality rates (Guha-Sapir, Hoyois, and Below 2016).These not only resulted in drowning injuries and acute trauma, but also promoted spread of infectious water-borne diseases (Alderman, Turner, and Tong 2012), and adversely influenced psychosocial health of affected populations (Paranjothy et al. 2011). With rising sea levels postulated to further contribute to flooding, especially in coastal areas (Neumann et al. 2015), climate-related health impacts will only intensify in the coming decades. As such, broadening knowledge of weather extremes is pivotal in the face of a changing climate, so as to improve strategies to minimize health impacts.

Thermal extremes

Aside from that, increasing occurrences of heat waves in recent years are posing a major concern to human health, and have been linked to a rise in deaths, especially in the elderly (McMichael, Woodruff, and Hales 2006). The unprecedented European heatwave in 2003 was not only the warmest for 500 years (Luterbacher et al, 2004), but also led to more than 70,000 deaths with excess mortality rising with age (Robine et al. 2008). Subsequent devastating heatwaves include another record-breaking one affecting Eastern Europe and Russia in 2010 (Barriopedro et al. 2011), alongside similar events in the United States in the past few years too (NOAA 2011; NOAA 2016). Importantly, with the elevated risk of such weather anomalies occuring in the near future (Coumou and Rahmstorf 2012), there needs to be greater understanding of their impacts on health. With studies consistently showing elderly people to be more susceptible to heat-related mortality, particularly due to cardiovascular and respiratory dysfunction (Åström, Bertil, and Joacim 2011), coupled with current trends pointing towards an ageing population, acknowledging these risks and determining the next step becomes exceedingly essential. Furthermore, urbanization has been postulated to aggravate effects of heatwaves resulting from the ‘urban heat island’ phenomenon, where temperatures are warmer than surrounding rural areas (Zhao et al. 2014), thereby contributing to heat-related mortality and morbidity. While increasing minimum temperatures can reduce mortality linked to cold-related events, evidence points towards the influence of factors other than temperature, thus suggesting that health risks due to heat extremes might overshadow any perceived benefits from fewer cold days (Kinney et al. 2015). All these highlight the severity of thermal-related climatic events on health, and the pressing need for more robust management.

Indirect influences of natural systems

Infectious diseases

On the other hand, climate change has been shown to exert indirect effects on health through various pathways. One of the most widely-researched upon area is the transmission of infectious diseases. Dengue fever is particularly important due to its rising global incidence with almost half of the world’s population at risk (WHO 2016b), and causing 390 million infections annually (Bhatt et al. 2013). Indeed, the spread of dengue fever was found to be heavily influenced by climatic variables – rising temperatures and humidity (Naish et al. 2014). Although predominant in Asia, cases have arisen in previously unaffected geographical regions, such as Madeira, Portugal in 2012 (Sousa et al. 2012) and the United States (Bouri et al. 2012), undoubtedly presenting challenges to healthcare organisations worldwide. Climate change effects on malaria, however, remain debatable. While warmer temperatures were associated with malaria incidence (Alonso, Bouma, and Pascual 2010), supported by recent locally transmitted outbreaks in Greece (Danis et al. 2011), its endemicity and geographical extent have declined, with limited impact of temperature changes due to economic development and disease control measures (Gething et al. 2010). Additionally, even though climate change potentially affects transmission of tick-borne Lyme disease, knowledge gaps in other factors i.e. behavioural, developmental and demographic processes of ticks hinder efforts to establish the true influence of environmental variables (Ostfeld and Brunner 2015). Aside from vector-borne infections, climate change involvement has been postulated in transmission of water- and food-borne diseases too. In fact, rising temperatures have been associated with increased enteric infections (Lake et al. 2009). Research has implicated links with precipitation too, with disease outbreaks usually following extreme rainfall, such as Cryptosporidium sp. (Semenza et al. 2012).

Moreover, extreme weather events also facilitate transmission in a more straightforward fashion. These include human factors such as population displacement, and modifications in ecosystem of pathogens resulting in sanitation and hygiene issues during such events (Kouadio et al. 2012), all of which enhance transmission and infectivity (Wheeler and von Braun 2013). Taken together, non-climatic factors such as social and demographic changes, economic growth and urbanization play a role in disease transmission too (Naish et al. 2014). Therefore, these will have to be taken into consideration to fully ascertain the impacts of climate change on infectious diseases.

Air quality

With a sizeable body of literature on the effects of climate change on air pollution, understanding their health impacts has also become increasingly vital. Firstly, escalating temperatures and sunlight promote ozone formation (Jacob and Winner 2009), which contribute to pulmonary inflammation (Kinney 2008). Indeed, studies have associated ozone with respiratory and circulatory mortality (Turner et al. 2016), including more asthma-related hospital admissions and deaths (D’Amato et al. 2015). Likewise, concentrations of particulate matter is projected to rise in conjunction with climate change, though varying based on different components (Jacob and Winner 2009). This is further exacerbated by wildfire risk, which is greater in response to increased temperature, decreased soil moisture and droughts (Kinney 2008). Importantly, exposure to particulate matter translates to increased mortality and morbidity with diverse health implications, ranging from respiratory and cardiovascular diseases, to diabetes and cancer (Kim, Kabir, and Kabir 2015). Aside from these, climate change-mediated temperature and precipitation rises, as well as increased carbon dioxide concentrations, have resulted in elevated aeroallergen release and severity (Reid and Gamble 2009). This can then contribute to allergic diseases and aggravate respiratory illnesses (Kinney 2008). Indisputably, with emerging evidence linking climate change to air quality and consequent health impacts, stronger emphasis is needed on engendering research and developing efficacious solutions.

Impact of human aspects

Nutrition

As climate change gathers pace, the focus has begun to shift towards its potential to derail efforts to eradicate hunger. Despite a decline of 216 million people suffering from undernutrition worldwide since 1990–1992 on the backdrop of population increase (FAO 2015), present trends suggest progress in achieving global nutrition targets remain uncertain (IFPRI 2016). While this has been attributed to wide-ranging factors, extreme weather events are thought to play an important role in influencing nutrition (Wheeler and von Braun 2013). Extensive studies conducted have found that climate change is likely to adversely affect crop productivity in food-insecure areas, especially in South Asia and southern Africa (Knox et al. 2012; Lobell et al. 2008). Seasonal crop changes can also alter adaptability and complicate management, together with declining soil quality (Miraglia et al. 2009). Not only that, rising carbon dioxide levels have been found to lead to reduced micronutrients i.e. zinc and iron in food crops (Myers et al. 2014), which is increasingly crucial with an estimated two billion people suffering from micronutrient deficiencies today, thereby substantially worsening the burden of disease worldwide (IFPRI 2016).

However, the effects that climate change has on nutrition extends to broader aspects too. Firstly, decreasing crop yields from extreme weather, such as droughts, can drive up food prices (Brown and Funk 2008). This has been found to reduce food consumption and hence, harbour negative effects on health and nutrition (Green et al. 2013), especially in vulnerable populations living in poverty (Wheeler and von Braun 2013). Secondly, climate change can potentiate vector-, water- and food-borne diseases as discussed above, thereby impinging on nutrition in association with mortality and morbidity (Smith et al. 2014). Clearly, the complex interplay of all these aspects hampers understanding of the severity of climatic-related health impacts, which in turn hinder efforts to devise appropriate and effective management.

Psychological impacts

Besides the multitude of physical aspects above, mental health is influenced by climate change both directly and indirectly. For one, emotional distress, anxiety, depression and development towards post-traumatic stress disorder have been linked to extreme weather (Berry, Bowen, and Kjellstrom 2010; Smith et al. 2014). These events have also been associated with somatoform disorders, suicidality, drug and alcohol abuse and risk of child abuse, especially in vulnerable people with pre-existing mental health conditions (Swim et al. 2009). Furthermore, sub-acute events such as droughts have shown increased psychological distress and suicidality (Hanigan et al. 2012; OBrien et al. 2014). Interestingly, extensive research suggests rising temperatures may increase aggressive behaviours too (Hsiang, Burke, and Miguel 2013). On the other hand, such climatic extremes also have indirect effects on psychological health, stemming from subsequent socioeconomic consequences involving disruption of livelihoods, displacement, poverty, grief and bereavement amongst others (Berry, Bowen, and Kjellstrom 2010). Crucially, these effects are unequally felt, and instead, are more pronounced in less developed societies and vulnerable populations (Berry, Bowen, and Kjellstrom 2010). In this regard, with growing realization of the effects of climate change on mental health, expanding our knowledge base and developing ways to minimize its impact are paramount.

Adaptation and mitigation

Considering the far-reaching health implications arising from climate change, it is clear that extensive measures are needed to tackle and resolve these issues, comprising both adaptation and mitigation in a broad two-pronged approach. Despite the growing body of scientific literature on the subject, efforts have been sorely lacking, with less than 1.5% of international budgets allocated towards combating these difficulties (WHO 2016c). Nonetheless, this wealth of data presents valuable opportunities for us to re-evaluate present strategies, and strive to improve readiness and resilience in a rapidly changing world.

Adaptation

In this regard, robust public health preparedness is essential in managing health susceptibilities to climate change (Frumkin et al. 2008). This involves using public health surveillance in the detection of infectious diseases and identification of risk factors, so as to appropriately allocate limited resources to manage outbreaks in vulnerable regions and populations. The development of early warning systems has been proposed to reduce disease burdens, such as for dengue fever in Singapore (Hii et al. 2012), while a study on Campylobacteriosis risk in the United States showed effectiveness in predictability (Weisent et al. 2014). Additionally, climatic warning systems could hold usefulness in reducing mortality and morbidity, thereby improving decision-making and facilitating response within healthcare, for instance in relation to heat waves and floods (Lowe et al. 2016; Toloo et al. 2013). Indeed, the Climate Risks Early Warning Systems initiative was drafted and launched at the recent Paris climate summit, signifying the importance of surveillance in dealing with these health issues (UNISDR 2015). In conjunction with strengthening public education systems (Shi et al. 2016), these may prove vital in adaptation against climate-related health impacts.

Besides this, rapid advances in the understanding of infectious diseases have contributed to a myriad of disease control interventions targeting prevention and management. For vector-borne diseases such as malaria, insecticide-treated mosquito nets and indoor residual spraying alongside chemoprevention in vulnerable populations i.e. pregnant women were attributed to declining prevalence since 2000 (White et al. 2011; WHO 2016d). On the other hand, the focus on management led to development of more efficacious immunization programmes. The introduction of a new dengue vaccine, CYD-TDV or Dengvaxia®, in several countries met with promising results on efficacy and safety (WHO 2016e). The administration of oral cholera vaccines has also demonstrated usefulness, though more research is required to evaluate cost-effectiveness and target populations (Harris 2016; Lopez et al. 2014).

Notwithstanding, efforts targeting management of other health impacts have intensified in the past few decades. The occurrences of recent natural disasters have led to increased attention on the post-disaster response, involving not only resource availability and accessibility, but also close cooperation with relevant stakeholders – such as the government, construction industry and market, transportation system (Chang et al. 2010), as well as resilience and preparedness of healthcare services during emergencies (Achour and Price 2010). Food security has also become a critical concern, with measures to boost nutrition fast gaining traction. These include climate forecasting in agriculture, water and soil conservation technologies, improved pest and disease management, and diversification of resources – possibly with modified or resilient crop varieties better equipped to withstand changing environments (Vermeulen, Campbell, and Ingram 2012). In other sectors, reducing food waste and increasing production of fisheries have been proposed (Vermeulen, Campbell, and Ingram 2012). Furthermore, the inclusion of food aid in disaster relief may alleviate nutritional insults, as long as there is swift recognition of vulnerable populations, versatile financing and capacity for rapid scale-up (Alderman 2010). Nevertheless, there have been criticisms against these measures that not only pertain to food safety and environmental risks, but also socioeconomic disparities (Godfray et al. 2010). Therefore, effective implementation relies upon understanding the complex interplay of factors to better address these concerns and optimise strategies.

Mitigation

Significant headway has been made in devising mitigation strategies too. With rising temperatures alongside the urban heat island phenomenon, reflective roofs and pavements have shown increased albedo, thereby leading to decreased radiation absorption with a corresponding decrease in urban temperatures (Santamouris 2012). Evaluation of green roofs has similarly shown potential (Li, Bou-Zeid, and Oppenheimer 2014; Santamouris 2012). On a larger scale, sustainable forest and mangrove management (Donato et al. 2011; Soares-Filho et al. 2010), and viable emission targets have been advocated (Meinshausen et al. 2009) to mitigate climate change by improving air quality and dampening temperature rise amongst others, possibly attenuating its impacts on health (Nowak et al. 2014; Shindell et al. 2012). However, implementation remains complicated, where in the former, concerns have arisen relating to rights of local communities, funding uncertainties and lack of accountability (Turnhout et al. 2017). In contrast, renewable energy is beginning to play a crucial role in long-term emission reduction (Luderer et al. 2014), together with energy efficiency technologies, fossil fuel switching, nuclear energy, and carbon capture and storage (Bruckner et al. 2014). Put together, these multi-faceted options need further evaluation and integration in order to achieve progress in alleviating health impacts resulting from climate change.

Concluding remarks

Indubitably, the increasing appreciation of climate-related health impacts has spurred on research and developments in adaption and mitigation strategies. However, tackling these issues remains challenging, due to the intricate interactions of factors involving not only healthcare, but also a wide range of differing sectors (Mickwitz et al. 2009). This is further complicated by the diverse beliefs and values held by various stakeholders, such as government institutions, local authorities, communities and even individuals, which are usually conflicted based on ethical, cultural, risk and knowledge perceptions (Adger et al. 2009). Not only that, policy implementation on the global front has met with repeated obstacles, with lack of political will, divisions between developing and developed nations and influence of national interests leading to cumbersome diplomatic impasses (Falkner, Stephan, and Vogler 2010). While the Paris climate agreement cemented multilateral commitment with incorporation of both top-down and bottom-up approaches (Dimitrov 2016), whether the goals are attainable is ambiguous and requires further evaluation (Boucher et al. 2016).

Crucially, amidst the complexities involved, what remains clear is the potential for devastating health and societal consequences if inaction prevails. Therefore, there is a need for all parties not only to understand and respect different perspectives, but also strive to resolve differences as much as possible. This can then pave the way for coordinated action towards devising an effective consensus plan and implementing sustainable development goals (Griggs et al. 2013). Ultimately, with little doubt that climate change is here to stay for the long haul, the onus is on us to decide how best to integrate and bring society forward in this new era.

Disclosure statement

No potential conflict of interest was reported by the author.

Notes on contributor

Nicholas Heng is a fourth-year medical student at the University of Dundee. Aside from striving to improve his clinical knowledge and acumen, he is also very keen on understanding more about how closely intertwined medicine and health are with regard to our surrounding environment. Outside of the classroom, he is not only heavily involved in research activities as part of the Dundee Research and Academic Medicine Society, but is also an avid squash player who competes regularly in the University Mens 1st team.

Notes

* The winner of the 2017 Holdstock-Piachaud Student Essay Prize, in memory of Douglas Holdstock and Jack Piachaud who were for many years inspirational editors of this journal, were Nicholas Heng and Anna Nakamura. This is Nicholas Heng’s essay on Tackling the health impacts of climate change in the 21st century; Anna Nakamura’s winning essay will appear in the next issue.