Heatwaves, ozone raise cardiac death risk: study, Pg14

Key Highlights:

• A new study published in npj Clean Air indicates that heatwaves significantly elevate surface ozone levels across India.
• Surface ozone concentrations during heatwaves reached 85-110 micrograms per cubic metre in northern India, exceeding the World Health Organization (WHO) guideline of 70 micrograms per cubic metre.
• The study estimates approximately 830 additional deaths from ischaemic heart disease and chronic obstructive pulmonary disease (COPD) during heatwave days in 2024 due to ozone exposure.
• Overall, the research links about 26,500 deaths from these conditions to ozone exposure during the entire pre-monsoon season of 2024.
• The Western Himalayas have recorded the steepest long-term rise in ozone levels.

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Detailed Insights:

• Surface ozone is a harmful air pollutant that forms when sunlight drives chemical reactions among other pollutants like nitrogen dioxide (NO₂) and formaldehyde (HCHO).
• This formation process is accelerated by higher temperatures, establishing a direct link between heatwaves and increased ozone concentrations.
• The study represents the first comprehensive, long-term, and country-wide assessment of surface ozone levels during heatwaves in India.
• Mortality figures were derived through modelling, as continuous ground-level ozone measurements were unavailable for specific heatwave days in many cities.
• The research identified 188 heatwave events over two decades, with severe years such as 2010, 2016, 2019, and 2024 following strong El Niño episodes.
• The substantial overall death toll is attributed to applying a small increase in individual risk across India's large population and two prevalent diseases.

Key Concepts Involved:

• Surface Ozone: A secondary air pollutant formed in the lower atmosphere through photochemical reactions involving sunlight and precursor gases.
• Ischaemic Heart Disease: A condition characterized by reduced blood flow to the heart muscle, often caused by the narrowing of coronary arteries.
• Chronic Obstructive Pulmonary Disease (COPD): A progressive lung disease that obstructs airflow from the lungs, making breathing difficult.
• El Niño: A climate pattern involving the periodic warming of sea surface temperatures in the central and eastern tropical Pacific Ocean, influencing global weather.