A peep into the air pllution of Guwahati

Ranjan Kumar Padmapati

(The writer can be reached at rkpadmapati@yahoo.co.in)

A report by a Swiss agency rocked and shocked the entire country, particularly the Guwahatians. It ranked Guwahati as the second most polluted city in the world on the basis of PM2.5 micron-size particulate matter concentrations. If one looks at the CPCB reports since March 16th to March 21st, 2024, it has been observed that AQI (Air Quality Index) gradually increased from a moderate value of 182 to a maximum of 311, assigned a tag of “VERY POOR” on March 20th, and then again AQI improved on March 21st to 193 due to drizzling. Amongst all relevant polluting parameters, the influencing parameters were only PM2.5 and PM10 particulate matter concentrations in the air, which were responsible for dropping air quality. It is to be noted here that amongst all types of particulate matter emissions, carbon blacks (CB) and PM2.5 are the worst; if they enter the lungs, they permanently settle in the lungs and do not come out, leading to complicated respiratory diseases.

In a set of data pertaining to Guwahati, computed in 2018 (UEinfo), sectors contributing to PM2.5 particulate matter concentration in percentage by individual sectors are shown as follows: Transport 35%, All Dusts 32%, Brick Kiln 4%, DG Sets 2%, Wood Burn 6%, Industry 14%, . In general, a chart from 2015 to date shows a gradual increase in the total combined dust burden from all sectors in the air, as well as each sector’s emissions individually. The PM2.5 dust load is increasing at a steeper rate compared to other parameters. It is observed that dust load dips during monsoon time, goes below the national average, and again increases during the winter months. The dispersion of pollutants depends on many other complex meteorological factors.

There is no denying the fact that air pollution in Guwahati is on the rise. As could be known from the data in the PCBA report, the yearly average of PM10 particulate matter concentration continuously remained at a higher level than the norm. During the recorded years 2011–2017, it varied between 88.19 and 147.19 micrograms per cubic metre against the norm of 60 micrograms per cubic metre for residential, rural, and other areas. That the AQI of Guwahati is entering a poor or very poor zone is evident from another set of data from the CPCB. In the first quarter of the year 2022, in January out of 31 days, 14 days recorded POOR, POOR,11 days as VERY POOR, 10 days worse than Delhi; in February out of 28 days, 12 days recorded POOR, 10 days as VERY POOR, 10 days worse than Delhi; and in April out of 30 days, 10 days indicated POOR, 9 days as VERY POOR. In a different report on World Air Quality pertaining to 2022, Guwahati ranks 95th based on PM 2.5 particulate matter concentrations. A study by a research team headed by Prof. Shared Gokhale of the IIT Guwahati reveals that exposure to black carbon (BC) in Guwahati is equivalent to smoking 25 cigarettes per day. The BC emission was high during the night and morning hours due to fossil fuel burning by trucks and buses. The study reveals that 70% of black carbon accumulation is due to fossil fuel burning and 30% is attributable to biomass burning due to cooking, heating, etc. 

In a different study by Dr. Kalyan Kalita and Dr. Mitali Gohain of the AEC at six different places in Guwahati in 2016, it was indicated that SPM (suspended particulate matter) and RSPM ( respirable suspended particulate matter) concentrations were highly responsible for polluting the environment, but oxides of sulphur and nitrogen were within the prescribed limits. The SPM, which varied from 282 micrograms per cubic metre to 491 micrograms per cubic metre, was above the permissible limit of 100 micrograms per cubic metre (revised NAAQS, CPCB, 2009–10) for the months of April and May. Similarly, RSPM remained high, between 153-236 micrograms per cubic metre in the month of April, against the norm of 100 micrograms per cubic meter. The AQI fluctuated between poor and moderate between 153 and 245.7. The Swiss report, though biassed, needs to be viewed from a wider perspective, on the issues. 

As per the ministry of road transport and highways, over 13 lakh vehicles are registered in the city. According to statistics from 2004, the most astonishing factor is that roughly 71,824 vehicles entered and went out of the city on a daily basis, severely polluting the city. As of now, according to a different source, there are 7 lakh vehicles touching the city on a daily basis. The number of city buses in Guwahati is nearly 650, along with a huge number of other buses. The majority of these diesel vehicles are quite old and require immediate replacement with CNG or EV-powered vehicles. All 2-stroke vehicles and heavy diesel vehicles contribute more to air pollution, particularly carbon blacks. Non-exhaust particulate matters of PM2.5 microns or less are produced from the rubbing of tyres with road surfaces, clutch plates, and brake wear; these also contribute to sufficient amounts.

The estimated emissions in 2018 from all modes of transport responsible for emissions of PM2.5 and PM10 particulate matters are 5,250 tonnes and 5,550 tonnes per year, respectively, and black carbon due to all transports is 2,150 tonnes per year, and organic carbon is 1,700 tonnes per year. Thus, in Guwahati, the transport sector is estimated to be the single largest polluter among all other sectors. The total loads of all sectors of PM2.5 and PM10 particulate matter are 14,950 tonnes and 41,550 tonnes per year, respectively. According to these statistics, all types of vehicles, particularly diesel vehicles, require urgent upgrading. The total distance covered by city buses is much greater than that of other vehicles; the fleet must be upgraded as a top priority. To reduce the traffic jams at junctions, 10 numbers of flyovers will help, but tuned computerised integration of all light signal points is necessary to reduce waiting time and reduce tail-pipe pollutants.

As combined, “all-dust” is the second-largest contributor to air pollution, of which road dust plays an important role. Vacuum sweeping is effective, but water washing of roads is considered to be more effective. Still more effective is to use dust suppressive chemicals with water; water lasts for only half an hour and evaporates quickly, while dust suppressant lasts for 6–8 hours and is cost-effective (50 paisa/square metre, IIT,K). Halting repeated earth cutting of roads and hills, full black topping up of paved and unpaved roads, quick removal of de-silting earths from roads, use of protective nets at construction sites, flyovers, increasing grass and forest covers, plantation of bamboos (mokol banh) and Jhaon trees on sandbars on both sides of the Brahmaputra will help reduce wind blowing of dust.