During the heatwave days of 2024, it links about 26,500 deaths from ischaemic heart disease and chronic obstructive pulmonary disease (COPD) to ozone exposure. File | Photo Credit: The Hindu While surface ozone — a pollutant harmful to the heart and lungs — already exceeds safe limits across much of India in the hot pre-monsoon months, a new study finds that heatwaves push it to still higher levels, thus adding several hundred deaths to a far larger toll that the study links to ozone across the season. The peer-reviewed study, published in the Nature Portfolio journal npj Clean Air on June 12, reports that surface ozone reaches 85-110 micrograms per cubic metre (μg/m³) in northern India during heatwaves and exceeds the World Health Organization guideline of 70 μg/m³ in every region of the country. The levels fall back within three to four days of a heatwave ending. Because ozone levels stay high for much of the season, the study attributes a large number of deaths to it even outside heatwaves. During the heatwave days of …