Researchers Disentangle the Key Drivers of Air Pollution
An OpenAQ Impact Story by Matt Lane
I recently watched a keynote from the WHO Second Global Conference on Air Pollution and Health which included testimony from Dr. Arvind Kumar, a practicing lung surgeon in India. Dr. Kumar presented dramatic images, which he said he witnesses daily, of diseased lungs from children and young adults. Dr. Kumar cited that now more than 50% of his patients are non-smokers, whose lungs are damaged due to living in over-polluted cities.
Dr. Kumar’s heart-wrenching experiences highlight in a dramatic fashion that air pollution is a silent killer affecting millions of vulnerable people worldwide. Thankfully, there are solutions–solutions being informed by the worldwide community of air quality researchers. These scientists are deepening our understanding of the causes and impacts of air pollution, which informs the development and implementation of solutions. I recently talked with three such researchers to learn more about the impact of their work and their utilization of OpenAQ, the world’s largest open-access, open-source air quality data platform (figure 1 below).
First, I talked to Zander Venter who in July 2020 published the first study quantifying the positive impacts of the Covid-19 epidemic on global pollution levels.[1] For example, he showed NO2 (nitrogen dioxide, one of the five major air pollutants) declined by up to 60% during Covid due to reduced human activity (figure 2 below). Further, Zander was able to specifically attribute the declines to less human movement day to day (e.g. less automobile traffic, etc.) by correlating with Google and Apple mobile data.
Zander did a follow-on paper that estimated 49,900 deaths were avoided during the first few months of lockdowns from reduced air pollution.[2] His work highlights that cities can dramatically reduce air pollution in relatively short order with new policies and investments that lower fossil fuel emissions.
I then talked to Prerita Agarwal and Caterina Mogno who both completed research on India, one of the world’s most polluted regions. Prerita analyzed “The Great Smog of Delhi,” a November 2016 severe air pollution episode.[3] “I partially chose this event because it was personal. I was born in Delhi and I was there in 2016. I remember the itchy and burning sensations,” Prerita explained. During the event, PM2.5 levels in Delhi exceeded 500 μg m-3, more than 30 times recommended levels.
Prerita modeled how much the occurrence was driven by natural conditions versus anthropogenic factors (i.e. fossil fuel emissions) versus biomass burning (i.e. agricultural clearing with fire). She discovered the dominant driver of PM2.5 in the middle and upper Indo-Gangetic Plain (IGP) was seasonal biomass burning (50–80% of the 24 hour mean PM2.5 levels, figure 3 below). Additionally, Prerita highlighted that a positive feedback loop amplified by high black carbon aerosols was a key factor in building up the episode. Elevated black carbon levels absorbed more sunlight which warmed the atmosphere in upper layers, which, in turn, stagnated and trapped the polluted air near the ground.
Much like Zander’s paper on the Covid-19 lockdowns, her research has practical implications. In her paper, she states: “Our work emphasises the need for rigorous policy interventions during post-monsoon to reduce agricultural crop burning, together with targeted anthropogenic emissions control across the IGP, to minimise such extreme episodes in the future.”
Lastly, I talked to Caterina Mogno who also researched Indo-Gangetic Plain air pollution drivers during her PhD at the University of Edinburgh, UK, but she focused on a comprehensive seasonal view.[4] Her model incorporated emissions, atmospheric chemistry, and weather transport across the four seasons (see figure 4 below). She found that pyrogenic factors (i.e. biomass burning) spike in the fall post-monsoon season (box h) whereas biogenic factors (i.e. natural conditions) elevate in the summer monsoon season (box f). Finally, anthropogenic factors (i.e. fossil fuel emissions) are relatively constant across the four seasons. One could see how this granular, seasonal view of the air pollution drivers could also help policymakers more intelligently target correction actions (e.g. biomass burning regulations in the post-monsoon season).
We then turned our conversations to the role open data played in these scientists’ research. Simply put, none of their important work would even be possible without access to key data sets (emission sources, air pollution levels, meteorological/atmospheric conditions, etc). As part of this, each of them explained how OpenAQ was foundational for accessing surface pollution data and was used to evaluate and verify their models. “I was heavily reliant on OpenAQ, I used it extensively,” said Prerita. Zander described, “OpenAQ was extremely important for me. I would have never been able to publish so quickly without it and it allowed me to quickly iterate. It played a huge role in my research.”
Zander, Prerita, and Caterina also valued how OpenAQ improved their efficiency through a single global data platform all accessible from common, machine-readable APIs. “I was so excited as a new PhD student because it made things so much easier. OpenAQ saved me a significant amount of time as I didn’t have to waste my efforts on data collection and management,” Caterina explained. Finally, they appreciated the quality and scope of OpenAQ. They were able to access data from all over the world including the Global South, from multiple sources, and OpenAQ has a rich set of archived data. “I did my study in 2021 and I was able to still access data from the 2016 pollution event,” highlighted Prerita.
As I wrapped up my discussions with Zander, Prerita, and Caterina, I felt appreciative that OpenAQ is so valued by each of them. I recalled the tragic incidences of lung cancer that Dr. Kumar sees daily and felt thankful that there is a community of scientists like these three doing vital work in response.
References
[1] COVID-19 lockdowns cause global air pollution declines, Zander S. Venter, Kristin Aunan, Sourangsu Chowdhury, and Jos Lelieveld, https://doi.org/10.1073/pnas.2006853117
[2] Air pollution declines during COVID-19 lockdowns mitigate the global health burden, Zander S. Venter, Kristin Aunan, Sourangsu Chowdhury, Jos Lelieveld, https://www.sciencedirect.com/science/article/pii/S0013935120313001
[3] Quantifying the dominant sources influencing the 2016 particulate matter pollution episode over northern India, Prerita Agarwal, David S. Stevenson, and Mathew R. Heal, https://pubs.rsc.org/en/content/articlelanding/2024/ea/d3ea00174a
[4] Seasonal distribution and drivers of surface fine particulate matter and organic aerosol over the Indo-Gangetic Plain, Caterina Mogno, Paul I. Palmer, Christoph Knote, Fei Yao, and Timothy J. Wallington, https://acp.copernicus.org/articles/21/10881/2021/
