Climate Change and Health

“I believe that climate change will ride across this landscape as the fifth horseman. It will increase the power of the four horsemen that rule over war, famine, pestilence, and death – those ancient adversaries that have affected health and human progress since the beginning of recorded history.”

- Dr Margaret Chan Director-General of the World Health Organization The 2007 David E. Barmes Global Health Lecture

Global warming and climate change are the undisputable realities of our times. These manifest in the melting of glacial ice caps, rising sea levels, extreme precipitation and desertification as examples. These exposures, both directly and indirectly, are affecting human health. Vectors, crops and water are part of the complex web of causation that ultimately impinges on our fundamental well-being. Children, young people and the elderly are amongst the most vulnerable in the population and often the most affected. Adaptation planning for the health impacts is critical as India and the world at large grapples with the increasing burden of the health impact. These include GIS enabled monitoring for disease surveillance, drought resistant crops and availability of rotavirus vaccination as examples. The health sector also has a vital role to play in co-benefits, that is interventions that have benefits for both the climate and health. These include examples such as clean cook-stoves and active transport options such as bicycles. As the pulse of the planet becomes more intricately linked with the pulse of populations, policy relevant research, inter-sectoral action for climate and health as well as effective communication will be critical to tackle the emerging conundrum.

View Infographic on Impact of Climate Change on Health

Infographic on Impact of Climate Change on Health


Health Outcomes

Water-/ Vector- Borne Diseases

Change in climate is not a mere environmental or developmental issue. It is known that environmental factors can directly or indirectly affect survival, persistence, and ability to produce disease. The major diseases that are attributed to poor environmental conditions and sanitation are water-borne diseases like cholera, shigellosis, Escherichia coli diarrhoea, poliomyelitis, typhoid fever, water-borne viral hepatitis, protozoan and helminthic diseases. Water-borne diseases alone can cause more than two million deaths annually globally and account for 4.8% of disability-adjusted life years (DALYs) of the total global burden of disease. Freshwater sources are a must for the prevention of water-borne diseases. Evidence shows that the more the temperature lower the potential of water availability and higher is the chances of infections through water.

Acute water-borne disease is one of the most important health-related impacts linked to short term and long-term changes in climate. With climatic variations, non-climatic factors also contribute to the global burden of water-borne diseases. Water shortage increases chances of infection due to perpetuation of unhygienic and poor sanitary conditions, and flooding contaminates drinking water supplies. Thus, although there is strong suspicion that global climate change influences infectious disease transmission dynamics, the extent of the influence is uncertain due to non-availability of data on these non-climatic factors that may also positively or negatively contribute to the occurrence of diarrhoeal diseases.

Due to lack of sophisticated technologies, previously, quantifying climate change and its impact on water-borne diseases like cholera was a challenge. But with the advent and use of sophisticated modern technologies like remote sensing, a new horizon has opened up. Researchers are now able to quantify the burden due to climate change as well as forecast impending epidemics.

The changes in global climate are getting reflected on the whole planet. Due to the lack of robust data, the magnitude of the effects of climate change on human health is difficult to quantify and, as a result, difficult to predict. Consequently, adaptive strategies must be reviewed and adjusted as new information and improved climate models are available. Developing effective strategies require a multi-sectoral approach, involving different government agencies, academia, and general public. The strategies are mentioned in the table.

Food Security & Malnutrition

The World Food Summit in 1996 defined food security as “Food security exists when all people, at all times, have physical, social and economic access to sufficient, safe and nutritious food which meets their dietary needs and food preferences for an active and healthy life” (FAO, 1996). Thus, there are three main dimensions to food security i.e. food availability, access to food and food absorption. Climate change affects food security in complex ways. Both biophysical and social vulnerabilities determine the net impact of climate change on food security (FAO, 2016).

Food security is high on India’s list of development priorities because the country’s relatively high rates of economic growth have not led to a reduction in hunger and undernutrition. India has failed to meet the Millennium Development Goal of halving the proportion of people who suffer from hunger (UNDP, 2015). About 12 Indian states fall under the ‘alarming’ category of the Global Hunger Index (Menon P et al., 2009). The composition of food basket is rapidly changing due to rising incomes and growing urbanization i.e. away from cereals to high value commodities like fish and meat. Thus, there is an increase in demand but production is constrained by low yield growth. Food production: Climate change causes significant increase in intra- seasonal and inter- annual variability of monsoon rainfall. According to World Bank estimates, for a global warming of 4C, there will be a 10% increase in annual mean monsoon intensity and a 15% increase in year- to- year variability in monsoon precipitation (World Bank, 2013). Therefore, the World Bank (2013) predicts that droughts will pose an increasing risk in north-western part of India while southern India will experience an increase in wetness. India is dependent on groundwater for irrigation and 54% of India faces high to extremely high water stress (Shiao T et al., 2015). With increased periods of low precipitation and dry spells due to climate change, India’s groundwater resources will become even more important leading to greater pressure on water resources. Thus, India’s food production is highly vulnerable to climate change due to high sensitivity to monsoon variability. Wheat and rice are two crops central to nutrition in India and thus sensitive to climate change (Lobell DB et al., 2012). Both acute water shortage conditions and thermal stress affect rice and wheat productivity severely.

Food access: Variation in length of the crop growing season and higher frequency of extreme events due to climate change and the consequent growth of output adversely affect the farmer’s net income. Food stocks begin to run out 3-4 months after harvest, farm jobs are unavailable and by the next monsoon, food shortages peak to hunger (Ramachandran N, 2014). Landless agricultural laborers wholly dependent on agricultural wages are at the highest risk of losing their access to food. Increased frequency of droughts and floods in regions with high food insecurity and inequality will affect children more. Studies have shown that drought- prone or exposure to floods result in a fall in income and thus huge impact on child nutrition leading to long- term malnutrition (Vedeld T et al., 2014). Since food is the single largest expenditure for poor urban households, displacement, loss of livelihood or damage to productive assets due to any such extreme weather event will have a direct impact on household food security. They are also vulnerable to increases in food prices following production shocks and declines.

Food absorption: Change in climatic conditions could lead to a reduction in nutritional quality of foods (like protein, iron, zinc) due to elevated carbon dioxide levels (FAO, 2016). This change in quality will accelerate hidden hunger or micronutrient deficiency. Also, an increase in temperature and decrease in precipitation are associated with an increase in diarrheal disease in children (Alexander KA et al., 2013). Due to the emergence of new pests and diseases with climate change, the human health will be affected and the capacity to utilize food effectively will be lowered. High incidence of under nutrition due to poverty exposes the urban poor to disease linked with climate impacts and thus aggravating undernutrition and ill- health and reducing the ability to adapt and build resilience to climate change. Children are at greater risk with restricted food supplies (Smith KR et al., 2014).

Actions/ Steps to prevent food insecurity: Action to prevent or reduce the increasing food insecurity may include adoption of sustainable agricultural practices like crop varieties which are more tolerant of temperature and precipitation fluctuations and are more water- and nutrient- efficient; water supply management including new storages and water harvesting; emphasis on public health and urban food insecurity; enhanced livelihood security, and so on (VB Athreya et al., 2010).

Floods, Droughts and Storms

Climate change leads to extreme weather events like droughts, floods and storms which have adverse impacts on water resources, agriculture, forests, coastal zones, energy and infrastructure and on human health. India, being a developing country, has limited resources and therefore would need to mobilize substantial resources to build additional capacity for addressing these adversities. The most severely affected states by droughts include Rajasthan, Gujarat and Andhra Pradesh. Andhra Pradesh has initiated some innovative management practices to tackle the recurring problem of droughts. Similarly, Uttar Pradesh is severely affected by floods and Orissa by cyclones (Bhattacharya S and Das A, 2007).

These extremes of temperature and rainfall in form of floods and droughts have direct immediate effects of physical injury and morbidity and mortality as well as long- term effects on mental health (Crabtree, 2012). The changes in temperature and rainfall may also affect the distribution of disease vectors, e.g. those of malaria and dengue, and the incidence of diarrhoeal diseases. Flooding may lead to mobilization of dangerous chemicals from storage or remobilization of chemicals already in the environment e.g. pesticides. During post- flood, there are increases in diarrhoeal and respiratory diseases in both high- and low- income countries and transmission are more where there is crowding of displaced populations. Increased vulnerability of populations in low- income countries may be related to habitation of high risk areas such as flood plains and coastal zones, the presence of a limited public health infrastructure and the substantial damage to local and national economies. Droughts may have wide- ranging effects on health including on nutrition, infectious diseases, and on forest fires causing air pollution especially in low- income countries (Haines A et al., 2006).

A severe tropical cyclone results in a storm surge i.e. an abnormal rise of sea level near the coast. This leads to inundation of low lying areas of coastal regions by sea water and thus, destruction of vegetation and reduction of soil fertility (National Cyclone Risk Mitigation Project, NDMA). The rise in sea level cause death and injury due to flooding and reduces the availability of fresh water, contamination of supply and health effects. Heavy rainfall events may transport the terrestrial agents into drinking- water sources resulting in outbreak of infectious diseases and may also lead to formation of breeding ground for mosquitoes giving rise to vector- borne diseases (Dutta P and Chorsiya V, 2013). The states vulnerable to cyclone disasters in India include four states (Andhra Pradesh, Odisha, Tamil Nadu and West Bengal) and one UT (Pondicherry) on the East Coast and one state (i.e. Gujarat) on the West coast. Cyclones in India occur in month of May- June and October- November with primary peak in November and secondary peak in May (National Cyclone Risk Mitigation Project, NDMA).

Heat Waves

Climate change is leading to an increase in average temperatures and increased possibilities of severe heat waves. A Heat Wave is a period of abnormally high temperatures, more than the normal maximum temperature that occurs during the summer season in the North-Western parts of India. Heat Waves typically occur between March and June, and in some rare cases even extend till July. The extreme temperatures and resultant atmospheric conditions adversely affect people living in these regions as they cause physiological stress, heat stroke, sometimes resulting in death.

The Indian Meteorological Department (IMD) has given the following criteria for Heat Waves:

  • Heat Wave need not be considered till maximum temperature of a station reaches at least 40°C for Plains and at least 30°C for Hilly regions

  • When normal maximum temperature of a station is less than or equal to 40°C: Heat Wave Departure from normal is 5°C to 6°C; Severe Heat Wave Departure from normal is 7°C or more

  • When normal maximum temperature of a station is more than 40°C: Heat Wave Departure from normal is 4°C to 5°C; Severe Heat Wave Departure from normal is 6°C or more

  • When actual maximum temperature remains 45°C or more irrespective of normal maximum temperature, heat waves should be declared.

Therefore, higher daily peak temperatures and longer, more intense heat waves are becomingly increasingly frequent globally due to climate change. India too is feeling the impact of climate change in terms of increased instances of heat waves which are more intense in nature with each passing year, and have a devastating impact on human health thereby increasing the number of heat wave casualties.

Health Impacts of Heat Waves:

The health impacts of Heat Waves typically involve dehydration, heat cramps, heat exhaustion and/or heat stroke. The signs and symptoms are as follows:

  • Heat Cramps: Edema (swelling) and Syncope (Fainting) generally accompanied by fever below 39°C i.e.102°F.

  • Heat Exhaustion: Fatigue, weakness, dizziness, headache, nausea, vomiting, muscle cramps and sweating.

  • Heat Stroke: Body temperatures of 40°C i.e. 104°F or more along with delirium, seizures or coma. This is a potential fatal condition.

Heat Action Plan:

The city of Ahmedabad had a major heat wave in May 2010 when the temperature reached 46.8°C, which led to 1344 additional deaths registered in the city during the month of May while heat waves in Andhra Pradesh in 2003 caused more than 3000 deaths. Thus, in order to protect and prepare people/ population from extreme heat events, the Ahmedabad Municipal Corporation with its partners prepared the first Heat Action Plan (HAP) in 2013.

The Heat Action Plan aims to provide a framework for the implementation, coordination, and evaluation of extreme heat response activities in Ahmedabad that reduce the negative health impacts of extreme heat. The Plan’s primary objective is to alert those populations most at risk (i.e. slum communities, outdoor workers, elderly and children) of heat- related illness that extreme heat conditions either exist or are imminent, and to take appropriate precautions. They have developed color signal system as an additional means of communication to issue heat alerts.

The key strategies under the Heat Action Plan are:

  • Building public awareness and community outreach

  • Initiating an Early Warning System and Inter- Agency Coordination

  • Capacity building among health care professionals

  • Reducing heat exposure and promoting adaptive measures

Individuals, community groups, and the media are also essential in fighting the effects of extreme heat. The media plays an essential awareness- building role by sharing news about health threats, and increases public protection by running ads and providing local resources information. Telangana has also prepared a State Heatwave Action Plan in 2016 under the supervision of Disaster Management Department, Government of Telangana.

Air Quality

Clean air is one of the foremost requirements to sustain support ecosystems which in turn affect human wellbeing and indeed life itself. Extensive industrial growth has led to increased release of various gaseous emissions and particulate matter. Air quality has deteriorated in most large cities in India, a situation driven by population growth, industrialization and increased vehicle use, amongst other factors. Integrated air quality management (AQM), an evaluation and monitoring tool, is a challenge to carry out in most developing countries because of lack of information on sources of air pollution and insufficient ambient air monitoring data that is available in the public domain. 
Urban air pollution is largely a result of combustion of fossil fuels that are used in transportation, power generation, industrial sector, and other economic activities. Household air pollution (HAP), also known as indoor air pollution (IAP), is a serious area of concern in rural areas and urban slums, as a majority of this population continues to depend on traditional biomass for cooking and space heating. 

Parameters of air quality

Air pollution consists of a complex mix of various substances in different physical and chemical states arising from various sources. WHO focus on four health-related air pollutants, i.e. particulate matter (PM), measured as particles with an aerodynamic diameter lesser than 10µm (PM10) and lesser than 2.5µm (PM2.5), nitrogen dioxide (NO2), sulfur dioxide (SO2) and ozone. This focus enables monitoring general state of air quality. The WHO guideline values for particulate matter are 50µg/m3 24- hour mean for PM10, 25µg/m3  24- hour mean for PM2.5, 100µg/m3  8- hour mean for ozone, 200µg/m3 1- hour mean for NO2 and 20µg/m3 24- hour mean for SO2 (WHO 2005 guidelines; 
Central Pollution Control Board (CPCB) in India implements the National Air Quality Monitoring Programme (NAMP) covering 224 cities/ towns in 26 states and 5 union territories of the country. CPCB has also developed national ambient air quality standards (NAAQS) in order to effectively manage the ambient air quality and reduce damaging effects of air pollution. Under NAMP, three major pollutants i.e. PM10, SO2 and NO2 have been identified for regular monitoring at all locations. The permissible levels of PM10, NO2 and SO2 are 100, 80 and 80µg/m3 over an averaging time of 24 hours. Other parameters like PM2.5, ozone, carbon monoxide, ammonia, lead, benzene, benzopyrene, arsenic and nickel are being added to the monitoring network under NAMP. Only 31 cities meet the standard of 60µg/m3 for PM10 out of 203 cities for which data exists. Almost all cities except one lie below the permissible limit of 50µg/m3 for SO2 (CPCB, 2014). 

Impacts of Air pollution

In 2012 alone, 7 million deaths in the world were attributable to the combined effects of ambient (3.7million) and household (4.3million) air pollution. The breakdown of attributable deaths by disease category is as shown in figure 1. 

Figure 1: Percentage of deaths attributable to outdoor and indoor air pollution by cause of death
Deaths due to air pollution
Source: World Health Organization

Cardiovascular and stroke related complications are the most important followed by respiratory impact (WHO, 2014).  Respiratory infections in children are aggravated, especially for those less than five years of age. Ambient and household air pollution begins to affect child health even before birth and continues even during the prime years of growth. 
Ambient air pollution is the fifth biggest cause of mortality in India with Indian cities figuring amongst the most polluted areas in the world (Atkinson RW et al., 2012). India registered an increase of about 12% in the number of deaths and about 3% in years of life lost attributable to outdoor air pollution between 2005 and 2010 (OECD, 2014). Both the outdoor and indoor air pollution is a serious environmental risk factor that causes or aggravates acute and chronic diseases. Indoor air quality has emerged as one of the most important issues of environment and health worldwide. Household air pollution (HAP) due to biomass cooking fuel is an important risk factor for a range of diseases especially amongst adult women in India (Sehgal M et al., 2014). HAP has been identified as one of the key indicators in its National Monitoring Framework for Prevention and Control of Non- Communicable Diseases. Eighty percent of rural and 19% of urban households use biomass fuel for cooking purposes. This leads to harmful health effects due to emission, during its incomplete combustion, of large number of air pollutants i.e. carbon monoxide, SO2, respirable particulate matter, poly- cyclic aromatic hydrocarbons, benzene and metals like lead and copper. This has resulted in increased cases of chronic bronchitis, tuberculosis, cataract among adult Indian women and stillbirths across India (Sehgal M et al 2014). Evidence has shown that indoor air pollution increases morbidity and mortality from respiratory tract symptoms in childhood (Hertz-Picciotto I et al., 2007). 
Indian metropolitan cities remain exposed to high levels of air pollutants due to high vehicular movements and poor roads. Some people by virtue of their occupation are more exposed to high levels of traffic related air pollutants. Thus, a reduction in lung function indices over years of occupational exposure has been reported in studies (Patil P et. al., 2013; Pal P et. al., 2010)


Several interventions have been adopted to improve urban and indoor air quality in India. 

  • CPCB set vehicular emission standards in India for both petrol and diesel driven vehicles. The Ministry of Petroleum and Natural Gas (MoPNG) has adopted the Auto Fuel Policy in 2002 which laid down a roadmap for introduction of cleaner fuels and vehicles in the country. Auto Fuel Vision Committee was set up in 2013 to recommend the future roadmap on advancement of fuel quality and vehicular emission standards upto 2025.

  • In order to control the indoor air pollution through provision of clean energy access, government has introduced various schemes that would facilitate clean energy access such as the Rajiv Gandhi Grameen Vidyutikaran Yojana, the Village Energy Security Programme, and the Remote Village Electrification Programme. The Ministry of New and Renewable Energy (MNRE) is promoting setting up of biogas plants in all the states and union territories of the country. Awareness generation among public and policymakers would help improve the path each community could take toward cleaner fuels. 

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