As per the news reports in October 2020, a new study, based on real time pollution data during Covid-19 lockdown from February 20 to April 14, carried out by scientists from the Delhi Pollution Control Committee (DPCC) and the Indian Institute of Tropical Meteorology (IITM), published in peer reviewed science journal, Current Science, has found that Delhi’s baseline pollution level for six different pollutants like PM10, PM2.5, NO2, and SO2, etc. (the minimum pollution when major polluting sources are shut) is about a tenth of the peak pollution, the capital witnesses, especially during the October-January period. They studied air quality levels at 34 locations in the capital, where real time pollution is monitored. Air quality of a place is directly related to overall pollution load from sources like industries, vehicles, and the local weather conditions, which impact dispersion of pollutants.
This study is based on average pollution levels for the city before and during the Covid-19 lockdown, which halted factories, construction sites, almost all vehicular movement, and some other local sources that pollute Delhi’s air. While emission sources dropped by 85 per cent to 90 per cent, resulting in sharp decline in pollution levels, the weather remained favourable to Delhi, pushing down the city’s pollution to rock bottom. The baseline levels of PM10 and PM2.5 were found to be 38ìg/m3 (± 8) and 22ìg/m3 (± 6) respectively. However, the baseline value of NO2 was found to be 8ppb (± 3), which is termed very high.
Even though PM10 levels remained mostly above the permissible limit (100ìg/m3) during the pre-lockdown period, it occasionally touched and crossed the 200ìg/m3 mark in the post-lockdown period, but remained much below the 100 ìg/m3 mark.
The level of PM2.5 remained mostly above the permissible limit (60ìg/m3) in the pre-lockdown period and on one occasion it shot up to nearly 140ìg/m3. In the lockdown period, it remained below the 40ìg/m3 mark on most days and even touched 20ìg/m3. (In winter, PM2.5 and PM10 shoots up to the marks of 300ug/m3 and 500ug/m3, primarily due to poor dispersion and higher pollution load because of stubble burning, especially in the farm-rich states of Punjab and Haryana. Then it starts declining from February.)
Conclusion This baseline pollution is chronically exposed and hence it is greatly relevant to epidemiological research. It is regarded to be the first baseline data. Some pollution will always be there because of kitchen pollution, emergency services like an ambulance on the road or a thermal power plant, and so on. No doubt, the lockdown has helped us prepare this first set of baseline pollution data, which should now be utilised to redefine our air quality standards as well as plan pollution mitigation strategies.
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Baseline is a comprehensive record of the existing infrastructure, modal split, congestion, air pollution levels, etc., used to inform plan preparation. A sustainable urban mobility plan (SUMP) should establish a baseline against which future progress can be measured. It should include a review of the institutional set-up, planning process, and delivery mechanisms.
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Courtesy: Hindustan Times, eltis.org