Delhi, a sprawling city in northern India, is nestled in the country’s Indo-Gangetic Plain where summer daytime temperatures average 32°C (90°F). But a series of persistent anticyclonic wind circulation events over the northern Indian Ocean, coupled with the fading El Niño, caused clockwise wind gusts to sink over the city, creating a persistent high-pressure heat dome that pushed 2024 temperatures to relentless highs. For weeks, brutal daytime temperatures stayed above 40°C (104°F), with little respite by night. The city’s solar heat-absorbing built environment made conditions even more miserable and dangerous. For Kumar, who spends 12 to 15 hours a day on the road making deliveries, the heat was life-threatening — as it was for the rest of the city’s 33.8 million people, many of whom work outside or lack air-conditioning. In Kumar’s cramped South Delhi neighbourhood, heat radiated off the walls and street day and night in a textbook example of the urban heat island effect. He was dehydrated and irritable most days. “Everywhere you look there’s a traffic jam in this city. Stuck in jams, under the hot sun with hot air blowing on your body; it was unbearable,” Kumar remembers. Normally, air pollution is perceived as a winter problem in Delhi, when a thick blanket of low-altitude smog gets trapped by cool air hanging above the metropolis. That smog is mostly composed of toxic PM2.5 particulates — very tiny particles that lodge in the lungs and can cause cardiovascular and respiratory disease. Every winter, PM2.5 levels peak due to seasonal crop burning and the exploding of fireworks during the Diwali festival, turning Delhi into one of the world’s most polluted places.

But now, as global warming and urban development bring higher temperatures over the city in summer, the co-occurring impacts of intense heat and air pollution compound in less obvious but seriously unhealthful ways.  Epidemiologist Poornima Prabhakaran, director of the Centre for Health Analytics Research and Trends at Ashoka University, calls the increasing ground-level ozone trend worrying. India has the highest death burden of any nation from chronic obstructive pulmonary disease, attributable to ground-level ozone levels, according to the “State of Global Air” report published annually by U.S.-based Health Effects Institute in partnership with UNICEF; ozone killed 238,000 people in India in 2019. People also continue breathing other toxic contaminants released from tailpipes and smokestacks. But “The impacts of [these] secondary pollutants have not been given as much attention compared to the impacts of smog and PM2.5, probably because of lack of awareness,” Prabhakaran said. Prabhakaran is working with scientists internationally, developing databases to track the impacts of air pollution (including PM2.5 and ozone) on a variety of outcomes, such as respiratory and cognitive health functions. “We’re trying to analyse, with data, every health outcome that we can get our hands on,” Prabhakaran said, adding, “Intermediate risk factors like hypertension, high blood pressure, fasting glucose, high lipid levels — all of those cardiovascular outcomes — are known to worsen with even chronic, low-dose [air pollution] exposure.”.........read on https://india.mongabay.com/2025/01/record-heat-is-worsening-pollution-and-public-health-in-the-global-south/