A sudden change in wind direction covered the national capital in dust, which was kicked up from the deserts in Rajasthan, pushing pollution levels on Thursday to more than double of what they were the day before, according to information from weather officials. The spike was driven by an increase in PM10 particles, which come from road dust, dried soil and sand. From 148 (classified as moderate) on Wednesday, the 24-hour average Air Quality Index (AQI) was recorded at 317 (very poor) on Thursday. “Delhi has come under the influence of a dust storm that originated in Rajasthan. The change in wind direction transported high mineral dust... It will take at least two days to dissipate,” said a scientist from Safar, a pollution forecasting agency under the Union earth sciences ministry.The effect was apparent throughout the day as hot, dry winds swept the city and the haze turned the sky white. “That the pollution shot up because of change in meteorological factors was evident from the fact that only the level of PM10 shot up. Level of PM2.5 (finer pollutants that are emitted as smoke from industries and vehicles) didn’t spike in tandem,” said a senior official of the Central Pollution Control Board. The problem has been aggravated by a slowdown in monsoon activity. There has hardly been any rain since it was declared that the monsoon had arrived last week, and the lack of moisture has meant that more dust is being kicked up in the atmosphere.This is, however, not the first time that Delhi’s air quality dipped because of a dust storm in Rajasthan and regions further northwest, such as Pakistan and Iran. PM10 levels shot up in a similar manner on June 12, when a dust storm hit the national capital region. Last year, such episodes took place twice: in mid-June and August 2018 when dust storms from Rajasthan and Oman had an impact on the region’s weather. The temperature at the India Meteorological Department’s Safdarjung observatory, which is taken to be representative of Delhi’s weather, was recorded to be 37.2°C on Wednesday. This increased to 39.2°C on Thursday, while relative humidity levels dropped from 52 to 47.“Strong winds from the west and northwest will continue to blow over the region for the next two days at least. We are expecting light rain in some parts of Delhi early next week,” said Kuldeep Srivastava, a scientist with the regional weather forecasting centre in Delhi.