Celebrations continued for the Tamil Nadu Pollution Control Board in Chennai even after Deepavali ended on Tuesday. A day after the festival of lights, the TNPCB released a report that concluded that all pollutant levels were within permissible limits following the Supreme Court ordered time limit on firework celebrations. But environmentalists have contested the methodology of data monitoring by the state body and alleged lack of satisfactory comparison with previous levels of pollution. They have further termed the study inconclusive.
Following the Supreme Court’s order, the Tamil Nadu government had fixed two time slots to burst crackers during Deepavali - 6am to 7am and 7pm to 8pm. In a report issued by the TNPCB, it claimed to have conducted ambient air quality surveys and noise level surveys in 5 places in Chennai city - Triplicane, Besant Nagar, Nungambakkam, Sowcarpet and T Nagar, to monitor the impact of firework celebrations as mandated by Central Pollution Control Board. The survey was conducted seven days prior to the festival (October 31 – November 6), during Deepavali (November 6-November 7) and will continue for seven after celebrations end.
As per the TNPCB's report which gives an average of pollutants for 24 hours, PM 2.5 or particulate matter 2.5 was well within permissible levels both before and after Deepavali in their 5 monitoring stations. According to the United States Environmental Protection Agency, particulate matter 2.5 are “fine inhalable particles, with diameters that are generally 2.5 micrometers and smaller.” The source of PM 2.5 comes from vehicle exhausts, construction sites, anything that involves burning of fuel, wood, coal, oil etc and also from natural sources such forest fires, states the New York Department of Health.
Incidentally, as per India’s Air Quality Index, the permissible level for PM 2.5 is between 0 and 60 μg/m3. Anything above 250 μg/m3 is categorised as “severe”.
Pre-Deepaavali, the minimum was 17 μg/m3 while the maximum was 29 μg/m3 in Triplicane. On Deepavali, the PM 2.5 levels were at 25 μg/m3 in Triplicane. In Besant Nagar, meanwhile, PM 2.5 levels increased on Deepavali day to 29 μg/m3 while it was a maximum of 21 μg/m3 before the festival. In Nungambakkam, a maximum of 33 μg/m3 was seen a week before the festival but the PM 2.5 levels saw a fall on Deepavali day to 21 μg/m3. As per the TNPCB report, Sowcarpet saw the maximum levels of particulate matter in the air at 42 μg/m3 on Deepavali while the maximum in the area was 40 μg/m3 days before the festival. In T Nagar, meanwhile, a maximum of 41 μg/m3 was recorded pre-Deepeavli while on the festival day, the levels dipped to 38 μg/m3, according to TNPCB.
The TNPCB also provided PM 10 data on Deepavali.
The PM 10 levels are recorded at 70 μg/m3 in Triplicane, 75 μg/m3 in Besant Nagar, 48 μg/m3 in Nungambakkam, 114 μg/m3 in Sowcarpet and 97 in T Nagar on Deepavali.
While the World Health Organisation (WHO) has set the permissible limit for PM 10 at 50 μg/m3, the TNPCB went on to celebrate the results by quoting the PM 10 levels in their report and claiming that all levels were within the permissible range of 100 as India’s National Ambient Air Quality standard. They have even lauded themselves for the 'awareness' that they have spread.
Incidentally, PM2.5 is a more serious health concern than PM10, since smaller particles can travel more deeply into our lungs and cause more harmful effects.
The flaws in the study
Environmentalists have, however, pointed out a number of flaws in the data that is provided by the TNPCB.
The first of this, is the fact that they have not provided PM 2.5 data from these locations in 2017 to compare if there is an actual reduction in pollution.
"Also, giving an average of 24 hours does no really give the right picture. It should have at least been recorded on an hourly basis. In fact, the Central Pollution Control Board gives you data for every 15 minutes. This will help you understand the maximum and minimum pollution seen in the day," says Shwetha Narayan, a Chennai-based environmentalist. "Averages don't work for toxic chemical or emissions," she adds.
Pooja Kumar of the Coastal Resource Centre further points out that in certain areas the PM 2.5 levels even SO2 levels are seen as lower on Deepavali than the days before the festival.
"This is logically not possible. In addition to this, TNPCB has given PM 10 data for both years but this is completely irrelevant because it doesn't affect the respiratory system as severely," she says. Most European countries, in fact have reportedly taken to measuring PM 1 now.
What Central Pollution Control Board says
The Central Pollution Control Board (CPCB) monitors air quality data in Alandur bus depot, Manali and Velachery residential areas. Data collected every 15 minutes on the day of Deepavali shows that between 10 pm and 10.15 pm on November 6, the PM 2.5 levels went up to as high as 302.19 μg/m3. This is two hours after the time fixed by the state government to burst crackers.
In 2017, the Alandur station, saw PM 2.5 levels reach a maximum of 837.78 μg/m3. That’s 1296.3% over the permissible limit in India.
While the monitoring station in IIT Madras is no longer functional, the one in Velachery residential areas saw PM 2.5 increase to as much as 165.65 μg/m3 between 10.45 pm and 11.15 pm on Deepavali. In Manali, meanwhile, the PM 2.5 levels were at a maximum of 186.71 till 9.15 pm. In 2017, this industrial area in North Chennai saw a maximum PM 2.5 of 999.99 μg/m3 during Deepavali.
"The levels may have reduced from a 900 to 200 μg/m3. But this doesn't mean things are now fine," says Shwetha. "As long as PM 2.5 levels are above permissible levels, the problem sustains," she adds.
Private initiative shows high levels of PM 2.5
In fact, a joint initiative to monitor air quality in Chennai by the Urban Sciences, Healthy Energy Initiative and Huma Lung Foundation has four monitoring stations located in residential neighbourhoods like Besant Gardens in South Chennai, Anna Salai (Huma Lung Foundation) in Central Chennai and in industrial areas like North Chennai’s MKB Nagar, and Ennore.
As per their reading, the levels of PM2.5 are still above permissible limits. Between 5.55 pm and 7.55pm on Deepavali, the level at Ennore was 916 μg/m3. It was 170 μg/m3 at Kuruvimedu, 65 μg/m3 at Kodungaiyur, 282 μg/m3 at Eldams Road and 100 μg/m3 at Nandanam.
"The fact that the TNPCB data is so generic and doesn't mention exactly where the monitoring system is, is problematic. In Besant Nagar itself, if they took the data in Theosophical society, the levels are likely to be lesser because of the tree cover. A main road meanwhile would have different results," says Shwetha. "From what we can see here, it seems like the TNPCB first decided what the conclusion of the data should be and then worked its way backwards."