Delhi's air quality deteriorated to the 'poor' category on Sunday, with the Air Quality Index (AQI) rising to 261, the highest level recorded in more than 85 days, according to official data. The sharp increase marks the city's worst air quality since April 17, when the AQI stood at 263, ending a prolonged period during which pollution levels largely remained in the 'moderate' and 'satisfactory' categories.

The Commission for Air Quality Management (CAQM) attributed the deterioration to the movement of transnational dust-laden winds originating from storm activity in Afghanistan, Iran and Pakistan. According to the commission, these long-range winds transported large quantities of mineral dust towards northwestern India, including the Delhi-NCR region, significantly increasing concentrations of particulate matter, particularly PM10. Officials said the weather pattern, rather than local pollution sources alone, was primarily responsible for Sunday's sudden spike in pollution levels.

The city's AQI climbed sharply from 140 on Saturday to 261 on Sunday, pushing Delhi into the 'poor' category. In addition to the influx of mineral dust from across the border, CAQM said strong winds sweeping across the Indo-Gangetic Plain also contributed to elevated dust levels in the atmosphere, worsening air quality across the National Capital Region. The combination of transboundary dust transport and prevailing meteorological conditions led to a rapid decline in air quality over the weekend.

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The commission has forecast that Delhi's air quality is likely to remain in the 'poor' category over the next few days as the dust-laden weather system continues to influence atmospheric conditions. However, it expressed hope that pollution levels would improve once the transnational dust spell subsides and the concentration of suspended particles in the air begins to decline. Authorities continue to monitor the situation and assess changes in weather conditions that could affect pollution levels.

According to the Central Pollution Control Board (CPCB), an AQI between 201 and 300 falls under the 'poor' category, indicating that prolonged exposure may cause breathing discomfort for people with respiratory illnesses and may also affect healthy individuals after extended outdoor activity. The CPCB classifies AQI values between 0 and 50 as 'good', 51 to 100 as 'satisfactory', 101 to 200 as 'moderate', 301 to 400 as 'very poor', and 401 to 500 as 'severe'.

Delhi's air quality has historically been influenced by a combination of local emissions, seasonal weather patterns and regional factors, including dust storms and agricultural residue burning. Sunday's deterioration highlights the significant role that transboundary weather events can play in affecting pollution levels in northern India. Environmental authorities are expected to continue tracking the movement of dust and weather systems while advising residents, particularly children, senior citizens and those with respiratory conditions, to limit prolonged outdoor exposure until air quality improves.

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