Climate scientists, public health specialists and economists have long been predicting that India will among the countries worst affected by climate change. It has a large population, the majority of whom are poor and vulnerable to changes in temperature, coastal disruptions like sea-level rise and shifting disease dynamics.

A worldwide report on the health effects of climate change released on Monday shows how India is already being hit hard by changing climate patterns.

The Lancet Countdown: Tracking Progress on Health and Climate Change report highlights the various ways in which climate change is hurting the health of people across the world. The report details three kinds of climate change impacts on human health. Direct effects are those that arise from changes in temperature and the frequency with which extreme weather events occur. Ecosystem-mediated impacts are changes in patterns of diseases due to changes in climate. Human institution-mediated effects are evident in undernutrition due to crop failure, population displacement due to sea-level rises and occupational health risks that arise due to climate change.

The most obvious direct impact of climate change on health is the exposure to rising temperatures, especially heat waves. The report estimates that 125 million more people were exposed to heat waves between 2000 and 2016 than in previous years. A record 175 million people around the world were exposed to heat waves in 2015 alone.

India has been disproportionately affected by heat waves, the report finds. Between 2000 and 2016, 125 million in India have been exposed to potentially fatal heat waves.

People over 65 are among the most vulnerable to heat and millions more people over 65 are being exposed to heat waves every year. Between 2000 and 2016, 31 million more people in India above the age of 65 have been exposed to heat waves than between 1986 and 2008.

The heat waves became considerably worse in 2014 when the average number of people over 65 exposed to heatwaves was 150 million more than in 1986-2008.

These trends have been evident in the rising number of heat wave deaths in recent years. In 2015, India recorded more than 2,400 heat wave deaths, with the majority of these occurring in Andhra Pradesh and Telangana. In 2016, there were more than 1,100 heat wave deaths. These recent heat waves have been accompanied by severe droughts in regions of central India like Marathwada and Bundelkhand.

Data from the National Disaster Management Authority shows the clear rise in the number of fatalities due to heat waves since 2000.

The spread of dengue

Climate change has also brought about a change in the distribution of vector-borne diseases like dengue and malaria and an increased burden of these conditions. The report estimates that between 50 million and 100 million dengue infections occur around the world every year, making it the world’s most rapidly expanding disease.

In fact, climate trends have led to an increase in the vectorial capacity – a vector’s ability to spread disease among humans – of the two dengue-carrying mosquitos. The capacity of Aedes aegypti has increased 3% since 1990 and of Aedes albopictus by nearly 6% in this period.

Along with climate change, the spread of dengue has been helped by factors like trade, urbanisation, global and local mobility, and climate variability. The authors of the Lancet report infer that while the causes for increased dengue mortality are complex, climate change will be an important contributing factor in the increased likelihood of dengue deaths.

India has seen worsening outbreaks of dengue in recent years. While some health officials attribute the greater number of cases to better reporting, other public health specialists point out that there may still be a large number of dengue cases going misdiagnosed or unreported.

For example, the National Vector Borne Disease Control Programme counts only those dengue cases that are confirmed by performing an enzyme-linked immunosorbent assay or ELISA test that detects the antibodies of produced by the body against the dengue virus. However, many patients are diagnosed using a test called the NS-1 antigen test, which is cheaper and faster. Because the National Vector Borne Disease Control Program does not consider NS-1 antigen testing as a confirmatory test, hundreds of patients who tested positive for dengue using the said test are not included in the database of cases.

Here’s a look at how the number of dengue cases and deaths that have been counted has risen in India in recent years.

The air pollution threat

Air pollution directly harms human health. Much of air pollution is due to greenhouse gas emissions that cause and exacerbate climate change. But research also shows that climate change can make the impacts of air pollution worse. For instance, climate change can change the dilution of air pollutants in the atmosphere, the rates at which pollutants are removed from the atmosphere, photochemical reaction rates, and the exchange of ozone between the upper layers of the atmosphere. Climate change may also increase wildfires and instances of lightning that produces nitrous oxides.

One of the most harmful components of pollution is fine particulate matter (smaller and 2.5 microns), known as PM2.5. Long-term exposure to PM2.5 increases risk of illness and death from cardiovascular and pulmonary disorders. The World Health Organisation estimates that there are about 3 million premature deaths every year due to ambient air pollution.

In 2015, air pollution contributed to 524,680 premature deaths in India, second only to China. The single biggest contributor was household air pollution produced mainly by solid cooking fuels , which was responsible for 124,207 premature deaths.

The Lancet report finds that PM2·5 concentrations in most cities far exceed the annual average limit set by the WHO of 10 micrograms per cubic meter. Cities in Central, South, and East Asia have the highest concentrations of ambient air pollution. India’s annual average PM2.5 concentrations is 59 micrograms per cubic meter, with a maximum measurement of 176 micrograms per cubic meter in Gwalior. Delhi also features high up on this list.

Higher temperatures in many parts of the world have also hurt occupational health and labour productivity, especially among people performing manual, outdoor labour in hot areas. Since 2000, productivity in rural labour has fallen by an average of 5.3% globally due to rising temperatures. In 2016, more than 920,000 people globally out of the workforce and 418,000 of them were in India alone.