The good news: Pollutants, especially particulate matter — PM10 and PM2.5, dispersed fast this Diwali in Delhi, riding on favourable weather conditions. The bad news: Air quality nosedived despite the favourable conditions. Noise levels spiked too. Here is a look at the elevated pollution levels and the health risks they subject us to.
Air quality monitoring during Diwali, tasked with multiple agencies in Delhi, often throws up starkly different analogies. This year, all agencies acknowledged that high wind speeds and cooler temperature allowed pollutants, especially particulate matter, to disperse faster this year. Air quality, however, still nosedived. Scientists said the dip, acknowledged across agencies, was despite the favourable weather conditions.
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- An air of gloom
- Delhi pollution: Saturday season’s most polluted day, no respite in sight, say experts
- Weather gives Delhi better air quality than this time last year
- Delhi: Don’t step out this Diwali
According to MoEF’s Central Pollution Control Board (CPCB), particulate matter peaked on Diwali, hitting nearly 600 micrograms per cubic metre for PM10 and 420 for PM2.5. This is around six times the prescribed limits for PM10, and eight times for PM2.5.
On Diwali in 2014 (October 23), the value for PM10 was between 184 and 481 micrograms per cubic metre. The maximum value of 481 was reported at Shadipur, three days before the festival. On Diwali in 2013 (November 3), PM10 had ranged from 796 to 1,138 micrograms per cubic metre. On Diwali 2012, it had been between 748 and 951 micrograms per cubic metre.
According to the CPCB, the rise in PM10 values seen in recent years is due to meteorological conditions — factors such as lower night time temperature, low mixing height and low wind speed that lead to accumulation of particulates in the air. CPCB scientists say comparing this year’s Diwali scenario with previous years is “not very scientific”.
“This year Diwali came later than usual. Had the festival been observed in the last week of October, considering the atmospheric conditions then, the situation could have been worse. Comparing two different atmospheric situations and, hence, particulate collection, does not make sense,” said Dr Dipankar Saha, head of CPCB’s air lab.
Dr Saha said atmospheric factors in the last week approaching Diwali this year were conducive to particulate collection, but by November second week, cooler temperatures and wind directions reversed this.
Other agencies however, forecast days ahead of the festival, that this Diwali would be much worse than previous years. Ministry of Earth Sciences’ System of Air Quality Forecasting and Research (SAFAR) which predicted air quality this Diwali would dip from last year’s “very poor” to “severe”, said the weather factors in the run-up to the festival were largely responsible for this.
Dr Gufran Beig, project director of SAFAR, said, “As predicted, this Diwali turned out to be more polluted than last year. There was enough moisture in the air and atmospheric holding capacity of the emissions coming from firecrackers was at its peak from 9 pm till early morning, bringing down temperature rapidly to 13 degree Celsius, around 2 degree Celsius cooler than expected.”
SAFAR noted less firecrackers were burst as compared to last year. This brought down its forecasts, based on the assumption that the number of firecrackers would remain the same. “Although air quality deteriorated, the magnitude was relatively less… than we expected. This may be attributed to source means reduction by same magnitude in the emissions from firecrackers which is a satisfactory sign,” said Dr Beig.
The CPCB however noted that unlike previous years where vehicular pollutants contributed to the particulate load, this year firecrackers were the main source.
SAFAR put the finer PM2.5 particles as the lead pollutant in the 281-302 micrograms per cubic metre range. The real-time monitoring at CPCB’s stations also showed PM2.5 levels crossed the severe range and emerged as the lead pollutant in six monitoring stations at various points on Diwali night.
CPCB scientists, however, said, in 24-hour averages, the finer particles did not contribute significantly to the particulate load. Dr Saha said, “Since there were no dust storms, and vehicular pollution remained minimum, PM2.5 particles reached the level of PM10 particles. So fine particles were not a problem this year, primarily because of the drop in vehicular pollution.”
SAFAR had predicted Diwali to be the harbinger of at least two “very poor” to “severe” air quality days, with PM10 levels in particular crossing 700 micrograms per cubic metre. “Pollution levels peak the day after Diwali, and always continue for one day, gradually subsiding. The peak hours were 10 pm to 2 am and 7 am to 9 am on November 12,” said Dr Beig.
But Dr Saha said due to the fast dispersion of particulates, CPCB did not include post-Diwali days in its report. According to the CPCB, pollutants like SO2, associated with firecrackers, have persistently decreased since 2012. It remained “well within the safe limits” this year. In 2014, the CPCB had noted that while SO2 levels were similar to 2013 on pre-Diwali days, on the festival day, the levels were lower than the previous year. In 2013, SO2 had decreased at five locations, while the values increased at two locations as compared to 2012.
The Centre for Science and Environment, which measured human exposure levels and observed the real-time spikes in ambient air quality in the DPCC and CPCB monitoring stations, however, said the 24-hour averages were misleading. Anumita Roychowdhury, executive director of CSE, said, “SO2 has long ceased to be a problem in Delhi’s air. During pre-Diwali days on November 6 and 7, the SO2 level was as low as 23 but on Diwali, the higher range in 24 hours reached 64 micrograms per cubic metre. SO2 in combination with PM is a dangerous combination.”
NO2, a vehicular pollutant, remained within prescribed limits this year, observed the CPCB. NO2 levels peaked at 79 and 77 micrograms per cubic metre at Pragati Maidan on November 9, two days before Diwali. In 2014, the range was from 11 to 254 micrograms per cubic metre. The highest level had been recorded at Pragati Maidan on October 20, three days before Diwali.
CSE which monitored real-time exposure to pollutants from 5.30 pm on Diwali, said the 24-hour averages did not capture the magnitude of the real-time spikes. “At Anand Vihar, level of PM10 was around 2,000 micrograms per cubic metre at about midnight. This is 20 times more than the safe level of 100,” said Roychowdhury.
Delhi government maintained the 24-hour average values of SO2, NO2 and PM2.5 were lower this Diwali compared to last year and attributed this to campaigns to reduce bursting of firecrackers. “We educated children in schools… held street plays… it appears it has yielded some results. The weather has also been favourable..,” said Ashwani Kumar, environment secretary.
Expert opinion and what research says
1. Dr Randeep Guleria, head of respiratory medicine, AIIMS, says, “Particulate matter like RSPM (Respirable Suspended Particulate Matter) is inhaled so the lungs and the airway are the first organs to be affected. PM10, which includes particles less than 10 micrometre in diameter, enter alveoli or small sacks in lungs, and get accumulated here. The smaller the particles, the deeper they enter into the lungs and cause more damage. So, while PM10 affects upper respiratory tract from the nose and windpipe, the smaller PM2.5 particles affect the lower respiratory system since they enter the lungs.”
2. According to Dr Guleria, such air condition first exacerbates existing respiratory problems like asthma and bronchial diseases, and is especially harmful for children, elderly, and pregnant women. “After the respiratory tract, the particles enter the blood stream around the heart from the lungs, and cause inflammation in the walls of the heart. This leads to the formation of plaques, which obstruct blood flow leading to cardiovascular problems like reduced heart function, and cardiovascular attacks.”
3. International research has linked effects of particulate matter beyond safe limits to almost all organs including the kidney and the brain,
and established its association with lung cancer.