Delhi's AQI hits 500: What is smog and how it aects us
Delhi's AQI hits 500: An explainer on smog as thick haze from stubble burning, weather, and pollutants choke the city, prompting emergency measures under GRAP to combat the severe air quality crisis. Thick grey haze choked Delhi for the third consecutive day on Tuesday, with pollution levels reaching a dangerous 488 on the Air Quality Index (AQI), falling into the ‘severe plus’ category. According to the Central Pollution Control Board (CPCB), the AQI stood at 488 at 9 am. On Monday, Delhi had recorded its second-worst air quality in six years, with the AQI reaching 494. The city’s worsening air quality is attributed to a combination of factors, including adverse weather conditions, stubble burning, and smog. Residents are grappling with unbreathable air and severely reduced visibility. Smog is a mix of smoke and fog, and there are two main types: Photochemical smog and Sulfurous smog. Photochemical smog is the most common. Photochemical smog, often referred to as 'Los Angeles Smog', is mainly formed in the summer months, particularly in subtropical areas. It consists of gases like carbon oxides, nitrogen oxides, and hydrocarbons. This type of smog forms when sunlight reacts with nitrogen oxides and volatile organic compounds (VOCs) in the atmosphere. Unlike sulfurous smog, photochemical smog doesn’t require smoke or fog to form. Nitrogen oxides are emitted by vehicles, power plants, and factories, while VOCs come from sources like paints, gasoline, and cleaning products. CAUSES OF SMOG Smog is caused when air pollutants and exhaust gases from human activities mix with the atmosphere. It results from the reaction of emissions from automobiles, industrial facilities, and power plants with sunlight. Other contributing factors include coal combustion, vehicular emissions, industrial pollution, and agricultural fires. The formation of smog is also influenced by local weather conditions, temperature, and climate. Long-term exposure to smog can have severe health consequences, including respiratory and cardiovascular diseases, asthma, allergies, and a weakened immune system. Smog can also increase the risk of developing cancer and other serious conditions. The eects can extend beyond humans: smog can contaminate plants and animals, especially those exposed to polluted air In Delhi, air pollution contributes to 10,000 to 30,000 premature deaths annually, according to the Centre for Science and Environment (CSE) report in 2023. The London Smog of 1952, which saw particulate matter (PM) levels reach around 500 micrograms per cubic meter, led to over 4,000 premature deaths due to a combination of high PM and sulfur dioxide (SO2) levels.
