During my master’s, Doctoral and even Post-Doctoral research days, I worked actively on-air pollution topics namely sensor development, pollution monitoring, pollution characterization, pollution transport or dispersion and pollution abatement methods. During those days we always used to consider baseline levels of samples which we attribute as locations with zero anthropogenic (human induced) activities as background values. We always hoped to find a scenario where we could take locations without any traffic, industry operations or other anthropogenic sources, it was very difficult choosing a forest area or greenery locations such as parks as locations of interest and attribute as baseline values. Covid -19 brought negative impacts on economy and public health, however it does give us an opportunity to unfold long debated topics on the baseline values of the pollution, impacts of pollution, its transport, deposition, speciation and other impacts. In this blog, I would like to summarize key learnings from the incidence of Covid – 19 and its impact air pollution due to lockdowns. I would like to follow the sequence of i. sensor systems and Monitoring ii. Ambient concentrations iii. Pollution characterization iv. pollution transport, v. Health implications vi. Dispersion modeling using WRF-CAMx and vii. Abatement techniques. I have used air pollution to broadly include Sulfur dioxide, Oxides of Nitrogen, Carbon Monoxide, Particular matter2.5 and Particulate matter 10, Ozone.


We have witnessed many case studies where monitoring of air pollution is being carried out using mobile networks, portable sensor systems coupled with GPS. These systems help covering more spatial coverage compared to fixed network systems. The monitoring studies reported during covid-19, majorly used fixed monitoring systems, with few exceptions of portable sensor networks. Industry also came out with novel pollution monitoring systems to assess the air pollution using sensors, UV or micro-sensor systems. There has been heightened interest in mobile sensor systems, data transmission using GPS, data analytics.

Many studies are carried out to assess the impact of covid-19 lockdown on air quality. As evident it showed a strong negative level in the air pollution levels due to the lockdown. A reduction of 40 – 60% air pollution levels are observed in many studies. Some studies found that diurnal levels are not changed due to lockdowns. It also showed a increase in ozone levels due to decrease in oxides of nitrogen. Oxides of nitrogen works as scavenger for ozone by participating in the titration. Few studies evaluated the impact of meteorological differences on the air pollution levels but attribute to similar if not same meteorological conditions existing for the locations.

Studies are also conducted to analyze the impact of air pollution sources on air quality. For this a detailed assessment is carried out to study the source apportionment. The studies conducted for India showed regional atmospheric transfer of pollution from coal burning and stubble burning as secondary source. Main source is attributed to residential burning. Similar studies were conducted for different countries and showed more or similar conclusion highlighting the primary sources of pollution are reduced and secondary sources increased in their contribution to pollution. Those studies also highlight the increased contribution of firework, secondary inorganic aerosol, road dust.

WRF-CAMx air quality numerical modeling studies were carried out to investigate the impact of human activity pattern changes on air quality. It showed reduced human activities and lowered SO2, NOx, PM2.5 and VOCs levels by almost 25% on an average. However, ozone levels increased due to reductions in NOx levels as it reduces the Ozone cleansing reaction. Such findings suggest significant background levels.

One negative consequence of air pollution on Covid -19 transmission and incident has been a noticeable finding highlighted many authors from US and China. Studies based on Kendall & Spearmann rank correlation studies are conducted to understand the impact. The research highlights a nonlinear relationship between temperature and covid -19 incidence. Temperature has been found to be a major factor for covid. In conclusive research also suggest impact of humidity on incidence of covid as well. Air pollution positively contributed to covid cases. An increase of 5-7% covid cases with 10% increase in AQI index are reported. Asymetric link has been found between air pollution and covid with strong negative to medium in case of studies carried out in US. It further attributes air pollution to chronic diseases and might be looked into those asymmetric channels. Similar studies carried out in India for Indoor air pollution and Covid for under 5 years with pre-existing co morbid conditions. It suggests a need for more detailed indoor air pollution and covid correlation studies. Few studies conclude non linear contribution of sources to particular air pollution.

Few authors attempted to study the impact of atmospheric boundary layer impact on air pollution during the baseline scenario. They found the age-old factor of increased temperature due to onset of summary resulted in decrease in the stability and increase in mixing height. Decrease in the air pollution levels are attributed to increase in the temperature which enhances the photochemical reaction. Few studies conclude the impact of wind speed on the dispersion of air pollution and a daily decrease in air pollution levels due to increase in wind speed. Similar studies are also carried out for other meteorological factors like relative humidity, pressure etc.

Air pollution since long has been attributed to health implications and air pollution related morbidities. Few studies are carried out to assess the total health risk assessment and conclude that air pollution related deaths are avoided due to lockdowns. It also showed a decrease in air pollution related total and cause specific death rate. Some studies conclude that while ambient air pollution might be reduced, however, for indoor such levels might increase and can contribute to health implications such as cooking or consumer products.

To conclude the topic of air quality with covid-19 like scenarios gives us an opportunity to close the gaps in research on various factors related to air quality research. The topic of transboundary dispersion modeling in absence of manmade sources of pollution, speciation of pollution and contribution of natural or secondary sources to air pollution levels is of interest. Research should not only be confined to these topics but also aim to work on topics like one health models. We tend to assess the impact of infectious agent on humans or impact of pollution on humans or transport of pollution in isolation. We need to develop a modelling framework of an integrated approach of interlinking multiple sources – sinks and parasites to develop more roust solutions to solve human issues. Since we can establish the baseline studies for major research topics, we should aim to merge research findings to create computational systems and algorithms on one health models. These systems which when link all factors be it environmental, social, animal we truly develop next generation solutions to safeguard our future generations.



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