A study published in the journal npj Clean Air reports that toxic ground-level (tropospheric) ozone rises during India’s pre-monsoon hot season and breaches the World Health Organization safe limit across every region. Ozone levels become especially high during heatwaves when strong solar radiation speeds the chemical reactions that produce ozone.
The researchers used surface, satellite and reanalysis data for 2004–2024 measured in March, April, May and June. Between 2004 and 2024 the seven regions in the study recorded 188 heatwave events in which surface ozone exceeded the WHO threshold of 70 micrograms per cubic metre. Northern India recorded the highest concentrations, peaking around 85–110 micrograms per cubic metre.
In 2024 the study estimated rises in deaths linked to chronic obstructive pulmonary disease and ischemic heart disease during heatwaves, a roughly 3.2 per cent increase. Authors and experts call for combined climate adaptation, heat-action plans and tighter controls on ozone precursor emissions.
Difficult words
- tropospheric — in the lowest layer of the atmosphere
- breach — to break a limit or go above itbreaches
- threshold — a set limit or level for something
- precursor — a substance that helps create another substance
- reanalysis — combined historical data and models to study weather
- heatwave — a period of very hot weather lasting daysheatwaves
- microgram — a unit of mass equal to one millionth of grammicrograms
- ischemic heart disease — a heart condition caused by reduced blood flow
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- The authors call for heat-action plans and tighter controls on precursor emissions. Which of these actions seems most important to you, and why?
- How might higher ozone levels during heatwaves affect daily life in your community?
- What practical steps could people take to reduce their exposure to ozone on very hot days?
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