CHENNAI: This year's Bhogi has been relatively cleaner with 13 out of total 15 monitoring stations recording lesser pollution levels than the previous year, claims the data released by Tamil Nadu Pollution Control Board (TNPCB).
One monitoring station has been set-up in each of the 15 Chennai Corporation zones. The air quality survey was done for 24 hours on pre-Bhogi (January 10-11) and on Bhogi day (January 12-13). Based on the data, it was observed that gaseous pollutants - Sulphur Dioxide (SO2) and Nitrogen Dioxide (NO2) at all 15 stations are found to be well within the prescribed standards of 80 ug/m3 (micrograms per cubic meter), while the particulate matter (PM 2.5) level was in the range of 52-102 ug/m3 as against the prescribed standards of 60 ug/m3 and PM 10 was in the range of 103-256 ug/m3 as against the prescribed limit of 100 ug/m3.
Surprisingly, the cleanest air was recorded in Royapuram where the Air Quality Index (AQI) was 113, an improvement of 68 per cent compared to previous year when the AQI was 349 which was the highest among all the zones. The data has been disputed by environmental activists saying some of the private monitors in the area were popping up massive numbers, where PM 2.5 value went as high as 800 ug/m3, while TNPCB's PM 2.5 reading showed a meagre 64 ug/m3.
Ambattur is the most polluted with an AQI value of 241. As per National Ambient Air Quality Index, AQI between 0-50 is considered 'good', 51-100 'satisfactory', 101-200 'moderate', 201-300 'poor', 301-400 'very poor' and 401-500 'severe'. On most days, Chennai's AQI swings between satisfactory and moderate categories, thanks to Bay of Bengal which sucks in most pollutants.
But, environmentalists say Chennai by no means is breathing "clean air". "The government simply doesn't have enough data. In Delhi, there are about 40 government monitors and a large number of private low cost monitors. In all, Delhi gets data from about 400 points. The TNPCB should also recognise the problem and beef-up monitoring mechanism. We have been conducting studies from 2016. The latest study was conducted in May-July of 2019 carrying out sampling at 15 sites across Chennai using low-cost monitors. The analysis shows levels of PM 2.5 in all 15 locations were above statutory limits. It ranged from 70.46 ug/m3 to 187.36 ug/m3. The samples also showed presence of heavy metals like manganese, nickel, lead and crystalline silica."
2.6 tonnes of waste tyres seized
TNPCB Chairman AV Venkatachalam said 32-night patrolling teams were formed consisting of officials from TNPCB, Chennai Corporation and police personnel. On the day of bhogi, burning of water materials were noticed and was put off by the patrolling teams. More than 2.6 tonnes of waste tyres which were kept for firing were seized and sent to the Common Hazardous Waste Management Facility at Gummidipoondi.
Comparative analysis of AQI recorded in 15 zones of Chennai in the year 2020 and 2021 during bhogi festival:
| Zone | 2020 | 2021 | deviation% |
| Thiruvottiyur | 190 | 156 | -18 |
| Manali | 273 | 184 | -33 |
| Madhavaram | 176 | 175 | -1 |
| Tondiarpet | 322 | 240 | -25 |
| Royapuram | 349 | 113 | -68 |
| TVK Nagar | 169 | 221 | +24 |
| Ambattur | 267 | 241 | -10 |
| Anna Nagar | 267 | 119 | -55 |
| Teynampet | 230 | 183 | -20 |
| Kodambakkam | 247 | 180 | -27 |
| Alandur | 207 | 167 | -19 |
| Valasaravakkam | 305 | 170 | -44 |
| Adyar | 217 | 140 | -35 |
| Perungudi | 177 | 143 | -19 |
| Sholinganalur | 155 | 197 | +21 |