Why do cities get polluted in summer?, Pg8

Key Highlights:

• In March 2026, the Commission for Air Quality Management (CAQM) revoked Graded Response Action Plan (GRAP) curbs, but reimposed Stage 1 in April due to rising summer pollution in Delhi.
• From April 1 to May 31, 2026, Delhi recorded 54 days exceeding the National Ambient Air Quality Standard (NAAQS) for PM10 and 40 days breaching hourly ozone standards.
• Cities like Mumbai, Chennai, Hyderabad, Bengaluru, and Kolkata also experienced summer pollution spikes, with elevated PM10 and ozone levels.
• Summer air pollution is characterized by coarser PM10 particles and ozone, influenced by dust storms, construction, and vehicular emissions.

Detailed Insights:

• Delhi and the Indo-Gangetic plain typically face winter smog due to low temperatures trapping pollutants, while summer brings stronger winds that usually disperse pollutants.
• Summer pollution is driven by local sources like vehicular emissions, road dust, construction, industrial emissions, and dust storms, exacerbated by human activities.
• Ozone forms when Nitrogen Oxides (NOx) and Volatile Organic Compounds (VOCs) react under strong sunlight, increasing during hotter months and contributing to respiratory issues.
• Hot conditions create low-pressure areas, causing dust storms like the loo, which elevate PM10 levels, worsened by construction and broken roads after winter restrictions are lifted.
• Delhi's Air Quality Early Warning System (AQEWS) forecasts pollutants, and the India Meteorological Department (IMD) issues weather bulletins to alert citizens about dust storms and poor air quality.
• Cities can combat pollution by enforcing dust management at construction sites, reducing heavy-vehicle movement, and cutting NOx and VOC emissions through cleaner transport.
• The Brihanmumbai Municipal Corporation (BMC) uses the Air Quality Decision Support System (AQDSS) to monitor construction sites, while campaigns like 'Red Light On, Gaadi Off' reduce idling emissions.

Key Concepts Involved:

• PM10: Inhalable particulate matter with a diameter of 10 micrometers or less, posing health risks.
• Ozone: A gas formed by the reaction of nitrogen oxides and volatile organic compounds in sunlight.
• GRAP (Graded Response Action Plan): A set of measures to combat air pollution based on air quality levels.