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A man crosses railway tracks with a bicycle over his shoulder amid low visibility on a winter day
Patna: The air quality index (AQI) in at least seven cities of Bihar slipped to the ‘poor’ category on Friday, with Arrah topping the list at 266, officials said.
According to the Central Pollution Control Board (CPCB), other cities in the poor category included Bihar Sharif and Rajgir (261 each), Samastipur (258), Buxar and Hajipur (229 each), and Patna (217).
According to experts, the air quality dipped to poor category in certain cities due to North-West movement of low wind speed and temperatures.
The AQI is an assessment of the air quality taking into account eight pollutants - PM 2.5 (particulate matter less than 2.5 microns), PM 10 (particulate matter less than 10 microns), nitrogen oxides, sulphur dioxide, ozone, carbon monoxide, ammonia and lead.
An AQI between zero and 50 is considered 'good' (minimal impact), 51 and 100 'satisfactory' (minor breathing discomfort to sensitive people), 101 and 200 'moderate' (breathing discomfort to people with lungs, asthma and heart diseases), 201 and 300 'poor' (breathing discomfort to most people on prolonged exposure), 301 and 400 'very poor' (respiratory illness on prolonged exposure), and 401 and 500 'severe' (affects healthy people and seriously impacts those with existing diseases).
Commenting on deteriorating air quality in the state, Devendra Kumar Shukla, chairman of Bihar State Pollution Control Board (BSPCB) told PTI, "Air quality has deteriorated in certain cities in the state because of northwesterly winds, coupled with calmer wind conditions coming from Uttar Pradesh, Delhi and Haryana." He said the situation will improve in a day or two.
"As the temperatures dip, cold north-westerly winds become heavier because of the increased moisture content. This also increases the capacity of the winds to capture pollutants close to the earth's surface", the chairman said.
Meanwhile, the minimum temperature dropped below 10 degrees Celsius at many places in the state on Friday.
The lowest was recorded at Pusa in Samastipur district at 7.9 degree Celsius, followed by Kishanganj (8.7), Sabour in Bhagalpur (9), Sheikhpura (9.3), Rajgir (9.4), Ziradei in Siwan and Agwanpur in Saharsa (9.5 each), and Aurangabad (9.8).