Maarg Manthan · Topic 16.2

Global Warming and Human Health: Mosquito-Borne Diseases, Ozone Depletion Effects

Environment & Ecology › Climate Change Impacts and Mitigation · Topic 16.2

Climate change affects human health directly through heat waves, floods, storms and fires, and indirectly through changes in disease patterns, food and water supply, air quality and displacement. Heat stress causes heat exhaustion, heat stroke, kidney problems and deaths, particularly among older people, outdoor workers, the poor and city dwellers; wet-bulb temperature, which combines heat and humidity, shows when the body can no longer cool itself. Warmer temperatures, changed rain and humidity extend the range and season of vectors such as Aedes aegypti and Aedes albopictus mosquitoes that spread dengue, chikungunya, Zika and yellow fever, and Anopheles mosquitoes that spread malaria. Floods and warm water favour cholera and other waterborne diseases, while crop losses raise malnutrition. Ozone depletion, which is different from global warming, lets more ultraviolet-B reach the ground, raising the risk of skin cancer, cataracts and weakened immunity and harming crops and plankton. India's National Programme on Climate Change and Human Health, launched in 2019, and the National Action Plan on Climate Change health mission address these risks.

5 min read · UPSC Prelims · Environment & Ecology · Climate Change Impacts and Mitigation

At a Glance

Direct risk Heat stroke
Mosquito diseases Malaria, dengue, chikungunya
Water risk Cholera, diarrhoea
UV effects Skin cancer, cataracts
Indian programme NPCCHH, 2019
Exam link UPSC Prelims, Environment & Ecology: Climate Change Impacts and Mitigation

Where Does It Fit?

This topic follows the physical impacts of climate change and turns to health. It also covers the human effects of ozone depletion before the topics on mitigation. Previous topic: Impacts of Climate Change: Acid Rain, El Niño, La Niña, Ozone Depletion, Ocean Acidification. Next topic: Climate Change Mitigation: Carbon Sequestration and Carbon Sinks.

How Does Climate Change Affect Health?

Pathway	Health effects
Heat waves	Heat exhaustion, heat stroke, dehydration, kidney disease, cardiovascular deaths
Vector-borne diseases	Mosquito range and breeding season expand, increasing malaria, dengue, chikungunya, Zika and others
Waterborne diseases	Floods, warm water and scarcity increase cholera, typhoid and diarrhoea
Air quality	Heat and wildfires raise ozone and particles that cause asthma and heart disease
Food and nutrition	Crop and fish losses and price rises worsen malnutrition and stunting
Extreme events	Floods, cyclones and droughts cause injury, deaths and mental stress
UV from ozone depletion	More UV-B causes skin cancer, cataracts, immune suppression and damage to crops and plankton

Why Are Mosquito-Borne Diseases Spreading and What Is Done?

Temperature: warm weather speeds mosquito growth and virus development inside mosquitoes
Rain and humidity: standing water breeds mosquitoes; humidity helps survival
Range shift: Aedes mosquitoes spread to higher altitudes and new cities
Dengue: cases have risen many-fold worldwide over decades
Malaria: risk moves to highlands and new areas
Urban factor: crowding, poor drainage and water storage add to breeding sites
Response: surveillance, vector control, early warning, vaccines and health system readiness
NPCCHH: National Programme on Climate Change and Human Health, 2019, covers heat, air pollution and vector-borne diseases

What Else Should You Remember?

Heat index: combination of heat and humidity
Wet-bulb temperature: 35 degrees C wet-bulb is considered the human survival limit
Vulnerable groups: elderly, children, pregnant women, outdoor and informal workers and the urban poor
Heat deaths in India: thousands in some bad years, with underreporting
Aedes aegypti: the main dengue mosquito, which breeds in clean stored water
Anopheles: the mosquito that spreads malaria parasites
Culex: spreads Japanese encephalitis and filariasis
Extrinsic incubation: virus takes less time to develop in warmer mosquitoes
WHO view: dengue incidence has grown dramatically in recent decades
Waterborne disease: floods contaminate drinking water
Air pollution link: hot, still weather traps pollutants and raises respiratory illness
Pollen season: warming lengthens allergy seasons
Mental health: disasters and displacement cause trauma
Ozone layer effects: UV-B damages DNA in skin and eyes
Skin cancer: risk rises with UV exposure, especially in fair skin
Cataracts: clouding of the eye lens linked to UV
Phytoplankton and crops: UV can reduce growth, affecting food webs
Montreal Protocol benefit: has avoided millions of skin cancer cases
Health adaptation: heat action plans, cooling shelters, mosquito control and clean water
National Vector Borne Disease Control Programme: India’s disease control programme
Lancet Countdown: annual report tracking health and climate
Link to previous: see Impacts of Climate Change: Acid Rain, El Nino, La Nina, Ozone Depletion, Ocean Acidification
Link to next: see Climate Change Mitigation: Carbon Sequestration and Carbon Sinks
Link to heat: see Urbanization and Climate Change: Urban Heat Island, Pollution in Metros
Caution: disease trends depend on many factors besides climate, so avoid simple claims
Exam hint: link each pathway with disease examples and the UV effects of ozone loss
Chikungunya and Zika: also spread by Aedes mosquitoes, which bite during the day
Heat illness signs: high body temperature, confusion, dry skin or heavy sweating and fainting need urgent cooling and medical help
Ayushman Bharat and primary care: strong health services at sub-centre and health and wellness centre level are key to handling climate-linked disease
Early warning: IMD heat alerts and dengue forecasts help people and hospitals prepare
Water and sanitation: safe water, toilets and drainage cut waterborne illness during floods
Occupational health: outdoor workers need rest, shade and water during heat waves

Why Does It Matter for the Exam?

Mosquito diseases: Malaria, dengue
UV effects: Skin cancer, cataracts
Programme: NPCCHH
Current affairs link: Heat waves and dengue
Common errors: treating ozone loss as the cause of global warming

As an analytical point, health is the most human face of climate change, and the poorest bear the greatest risk. Strong primary care, disease surveillance, early warning and urban planning for heat can save lives even before emissions fall.

Why Is This Topic Important?

Heat Direct harm
Vectors Range growth
UV Ozone loss

What Came Next?

The next topic covers climate change mitigation through carbon sequestration and carbon sinks. Next topic: Climate Change Mitigation: Carbon Sequestration and Carbon Sinks.

Key People and Terms

Vector Disease carrier
Wet-bulb Heat-humidity measure
UV-B Harmful ultraviolet
NPCCHH National health programme
Aedes Dengue mosquito
Anopheles Malaria mosquito

Exam Corner

Points to Remember

Dengue spread by Aedes.
Malaria spread by Anopheles.
UV-B causes skin cancer and cataracts.
NPCCHH launched 2019.
35 C wet-bulb is a survival limit.

Do Not Confuse With

Aedes and Anopheles Dengue versus malaria mosquito
Global warming and ozone depletion Heat trapping versus UV shield loss
Heat exhaustion and heat stroke Milder versus life-threatening

Memory Hook

Hotter, wetter, mosquitoes spread; heat kills first, UV burns later.

Mains Angle

Questions ask for pathways and examples. These points help.

Pathways Heat, vectors
UV Ozone
Response NPCCHH

A Question You May Face

An original practice question, not a past paper question.

“Discuss the effects of global warming on human health, with reference to mosquito-borne diseases and ozone depletion.”

How to Answer

Pathways Direct, indirect.
Vectors Mosquitoes.
UV Ozone.
Response Programme.

GS Relevance

Prelims: diseases, UV effects, programmes. GS Paper 2 and 3: climate and health.

Frequently Asked Questions

How does climate change affect human health?

Climate change affects health through heat waves that cause heat stroke and deaths, floods and storms that cause injury and disease, spread of mosquito-borne diseases, contamination of water, worsening air pollution, crop and food losses leading to malnutrition, and mental stress from disasters and displacement. The poor and vulnerable are most at risk.

Why are mosquito-borne diseases spreading with global warming?

Warmer temperatures speed up mosquito breeding and the development of viruses and parasites inside the insects, lengthen the season of transmission and let mosquitoes survive at higher altitudes and in new areas. Changes in rainfall, humidity, urban water storage and poor drainage add breeding sites, so malaria, dengue and chikungunya can spread.

How does ozone depletion affect human health?

A thinner ozone layer lets more ultraviolet-B radiation reach the Earth's surface. This increases the risk of skin cancer, cataracts and other eye damage, and weakens the immune system, and it also harms crops and marine plankton. Ozone depletion is a separate problem from global warming, though both involve atmospheric chemistry.

What is wet-bulb temperature?

Wet-bulb temperature is the lowest temperature air can reach by evaporating water into it, so it combines heat and humidity. A wet-bulb temperature of around 35 degrees Celsius is considered the limit of human survivability, because the body can no longer cool itself by sweating. Rising heat and humidity make such conditions more likely in parts of South Asia.

What is the National Programme on Climate Change and Human Health?

The National Programme on Climate Change and Human Health, launched in 2019 by India's Ministry of Health, aims to build the health system's capacity to deal with the health effects of climate change, including heat illness, air pollution and vector-borne diseases, through surveillance, training, awareness and preparedness plans.

PYQ Practice — Statement Analysis

1 Aedes mosquitoes spread dengue.

True

And chikungunya.

2 Ozone depletion reduces UV-B reaching the ground.

False

It increases it.

3 Warmer weather can expand mosquito ranges.