Heat waves are releasing deadly but overlooked pollutants

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Lutyens Delhi is one of the most iconic districts in the Indian capital. Home to the parliament building, numerous embassies and 90 acres of lush Mughal-era parkland, it’s an architectural paradise linked by roundabouts with tree-lined streets and mini-gardens. But despite being one of the city’s most sophisticated neighbourhoods, something sinister lurks in this clean, green neighborhood. It’s a hotspot for ozone, a dangerous and overlooked air pollutant.

India is no stranger to air pollution, with many cities reporting the worst air quality in the world. Every winter New Delhi is covered in smog for several days. However, debates about air pollution and mitigation policies focus primarily on particulate matter, PM2.5 and PM10, which are tiny particles or water droplets that are only a few microns in diameter. But scientists are becoming more and more wary of surface ozone. It is a secondary pollutant that is not emitted from any source and is formed naturally when nitrogen oxides and volatile organic compounds (such as benzene in gasoline and methane) react under high heat and sunlight. increase. This makes ozone one of the ugliest threats of our time, a co-occurring problem of pollution and climate change.

“Even an hour of exposure can have very bad health consequences,” said Avikal Somvansi, a researcher at the Center for Science and the Environment in New Delhi. Ozone is beneficial in the upper atmosphere, where it absorbs ultraviolet light, but at the surface, concentrations of ozone can be deadly. Data on its effects are still mixed, but a 2022 study estimated that ozone killed more than 400,000 people worldwide in 2019, a 46 percent increase since 2000. According to the 2020 World Atmospheric State Report, India has the highest number of deaths from ozone. The largest increase in the last ten years.

Ozone wreaks havoc on the respiratory tract. The U.S. Environmental Protection Agency warns that the gas “inflames and damages the airways” and “worsens pulmonary diseases such as asthma.” It does this by affecting cilia, the microscopic, hair-like structures that line the airways to protect them, says Karaikal, India-based clinician and community health expert. explains Karthik Barajy. After exposure, he said, “you’re more susceptible to respiratory infections,” adding that inhaling ozone also affects your lung capacity. Studies show that long-term exposure is associated with an increased risk of chronic obstructive pulmonary disease (a lung disease that causes difficulty breathing), as well as an increased risk of death from other cardiovascular and respiratory diseases. Even short-term exposure can lead to emergency room visits. “One to two days after ozone levels peaked, he saw an increase in hospitalizations for respiratory illness,” says Barajee.

Delhi and other major Indian cities see ozone surges throughout the year, but heatwaves, especially during the summer, are becoming more common due to climate change. The World Health Organization states that exposure to ozone in the air should not exceed 50 ppb he in 8 hours. Indian air quality standards state that this WHO limit should not be breached for more than 8 days per year, and no more than 2 days in a row. But an analysis by Somvanshi and colleagues found that ozone concentrations in Delhi and surrounding areas were already above the threshold for 87 days from March to May this year. Similar results have been seen in the last three summers. And while fewer stations recorded breaches of the ozone threshold this year than in previous years, the duration of the breaches was longer. “We are far from being compliant,” says Somvansi.

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