Why Mumbai continues to record unhealthy AQI even during January this year
According to the Central Pollution Control Board's (CPCB) data, Mumbai recorded moderate or unhealthy AQI on as many as 23 days during the month of January this year
The CPCB dashboard shows that during the month of January, Mumbai's AQI readings stayed between 120 and 150 which is in the moderate category and is categorised as unhealthy for sensitive groups especially the children and senior citizens. (Express Photo) Mumbai’s Air Quality Index (AQI) usually witnesses an improvement during the month of January, following its winter slump. The reason behind this has been a strong reversal of winds which are complemented by rising day temperature levels.
However, this year the city’s overall AQI continued to record unhealthy levels on most of the days. According to the Central Pollution Control Board’s (CPCB) data, Mumbai recorded moderate or unhealthy AQI on as many as 23 days during the month of January this year. With areas like Deonar recording very poor AQI for a day.
The CPCB dashboard states that AQI readings between 0 to 50 are regarded as good or safe, 51 to 100 are regarded as satisfactory, 101 to 200 are considered moderate, 201 to 300 are regarded as poor, 301 to 400 are termed very poor and above 400 are considered to be severe.
Furthermore, the CPCB data also shows that out of the 28 AQI monitoring stations that are active in Mumbai almost all of them have been recording moderate levels of AQI on most of the days in January. For example, Deonar recorded 28 days of unhealthy AQI which includes one day of very poor AQI, Ghatkopar recorded 23 days of moderate AQI, and 20 days at Chembur.
The CPCB dashboard shows that during the month of January, Mumbai’s AQI readings stayed between 120 and 150 which is in the moderate category and is categorised as unhealthy for sensitive groups especially the children and senior citizens.
Delayed monsoon withdrawal root cause
Speaking to the Indian Express, Gufran Beig, atmospheric scientist and chair professor at National Institute of Advanced Studies (NIAS) – Indian Institute of Sciences (IISC) said that Mumbai is recording a prolonged winter season due to a delayed monsoon withdrawal which took place last year.
“Last year in large parts of north India, monsoon withdrawal got delayed by a fortnight. Due to which the winter season also kicked in late. As a result, this year winter is going to stay for a prolonged period of 10-15 days. Therefore, Mumbai will continue to experience slower winds and dip in day temperature resulting in unhealthy AQI levels for at least two more weeks,” Beig told the Indian Express.
Since Mumbai is surrounded by the Arabian Sea from three sides the process of wind reversal disperses the pollutants that stay accumulated in the lower atmosphere. The reversal of the wind process takes place within a gap of 2-3 days, however, owing to the winter season when the speed of winds gets slower, the reversal of winds usually takes place after a period of 15 days.
“Due to the global climate change the process of air reversal has become very very slow and Mumbai’s proximity to the western coast also makes it vulnerable to the dust particles that are blown towards the mainland from the Thar desert and as well as the humid air coming towards the far eastern part of the globe from the middle east. These factors have made Mumbai vulnerable to air pollution as a result of which the city’s AQI continues to be on the upside post monsoon every year,” Beig added.
Vehicular emissions
Meanwhile, officials in the Brihanmumbai Municipal Corporation (BMC) and the Maharashtra Pollution Control Board (MPCB) have also attributed the pollution load to man-made factors like vehicular emission, dust displacement and construction works.
Mumbai has the highest vehicle density among metro cities. According to the state government’s data Mumbai has a vehicle density of 2,300 cars in every kilometer (KM) which is the highest among all metro cities. The government’s data also shows that the number has increased exponentially in the previous years. In 2019 the city’s vehicle density stood at 1,840 per KM while in 2014 it stood at 1,150 per KM.
“Mumbai has the highest vehicular density compared to other regions in the country and vehicular emission has been identified as the main cause behind pollution in the city. In addition to this, Mumbai is also recording a significant series of construction work for various private and public projects. These factors combined with the geographical factors like prolonged winter season have been contributing to deteriorating AQI levels in the city,” said an official.
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