GUWAHATI, April 5 - Astounding as it may sound, Guwahati�s pollution level continued to be high despite the lockdown during which industrial activity has been nil and vehicular movement negligible. Blame it on particulate matter.
In fact, Bulandshahr and Guwahati were the only two cities out of 103 in the country that recorded poor air quality during the lockdown period, according to the data from the Central Pollution Control Board.
On April 3, the Bamunimaidam station pegged the city�s AQI (air quality index) at 170. For the month of April last year, the average AQI was 101. AQI is assessment of the air quality by taking into account different factors. The lower the AQI the better the air is considered to be. An AQI between 0-50 is considered good, 51-100 satisfactory, 101-200 moderate, 201-300 poor, 301-400 very poor and 401-500 severe.
Guwahati�s average PM2.5 level was 162, PM10 was 170, nitrogen dioxide was 8, ammonia was 4, sulphur dioxide was 19, carbon monoxide was 19 and ozone 43. PM2.5 refers to atmospheric particulate matter (PM) that have a diameter of less than 2.5 micrometres, which is about three per cent of the diameter of a human hair.
The permissible level of PM2.5 is 60 micrograms per cubic metre, while for PM10 it is 100 micrograms per cubic metre, clearly indicating that the city�s particulate matter was much higher than safe limits. An AQI of 170, though said to be �moderate�, may cause breathing discomfort to people with lungs, asthma and heart diseases.
Senior environmental engineer of the Pollution Control Board Assam G Bhuyan said the data shows vehicular and industrial activities do not play a significant role in city�s environmental pollution, as is the perception. �During the last couple of days there has been widespread wind activity that led to pollutants in the air. One can easily see layers of dust on things kept outside or even inside residences,� he said.
Dust and meteorological conditions play a vital role, so pollution may not be just due to man-made emission. Northeast India generally suffers from significant pollution load because of biomass burning due to forest fires, crop residue burning and silt from the Brahmaputra river.
The pollution level in 88 cities across the country remained minimal during the lockdown. While 23 cities registered �good� air quality, 65 others recorded satisfactory air quality.