Air Pollution Mapping in Delhi

Air pollution is the third leading cause of death worldwide, and most large cities, Delhi included, have fine particulate matter (PM2.5) levels above WHO health guidelines. Here, we take a look air pollution mapping in the Delhi metropolis to better understand the current situation, and where things may be heading. 

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Air pollution’s origins are tightly linked to the history of industrialization, so I’ll start this article off by giving you a brief review of India’s. It began back in 1854 when the first cotton mill venture was launched, followed shortly after by the first jute mill in Calcutta. Large-scale industry accounted for 7% of national income along with mining, employing only 3.5 million (or 2.5% of the total workforce), while agriculture employed over 70%. Development was slow, and cotton and jute remained the two main industries for decades, overshadowing the infant-industries of paper, sugar, cement and steel. How these industries performed was entirely dependent on the state of the global economy; in the early 20th century, economic boom conditions increased domestic income, public revenue and public spending. Conversely, the first world war, its ensuing agricultural crisis and the Great Depression caused a crisis in India. 

After a few more ups and downs, decisive action was taken to expand industry during the post-second world war years. This resulted in a 7% annual growth rate between 1951 and 1965, a rate higher than anything recorded over such a period of time.

Naturally, with industry comes pollution, and India began to noticeably degrade its air quality around this time. But India as we know it today is one of the most polluted countries on earth, with 5 of the 10 most polluted cities in the world; so how did it get this bad? It seems to be correlated to population size and urban population growth rates. 

Oftentimes, excessive air pollution speaks of governance failures, unable to enforce legislation for pollutant control and public transportation alternatives. Delhi, however, boasts an excellent train system and fuel standards to rival those of the EU. Unfortunately, as the population continues to explode (from ~16.7 million in 2011 to 20 million in 2019), so does the car fleet, now standing at 10 million registered vehicles. The resulting traffic congestion is atrocious, despite odd-even regulation, where certain days in the week are reserved for odd license plates and vice-versa.

Delhi is experiencing a boom in construction, which benefits from little dust and emissions control, to which episodic landfill fires add their emissions, despite their official shutdown in 2009. Yet authorities place the blame on something else entirely: crop burning (below, Delhi Chief Minister tweeting about the issue).

Delhi has turned into a gas chamber due to smoke from crop burning in neighbouring states

It is very imp that we protect ourselves from this toxic air. Through pvt & govt schools, we have started distributing 50 lakh masks today

I urge all Delhiites to use them whenever needed pic.twitter.com/MYwRz9euaq

— Arvind Kejriwal (@ArvindKejriwal) November 1, 2019

Indeed, farmers of the nearby Punjab and Haryana region need to burn crop stubble after harvest, rapidly freeing up their land for sowing their winter crops before it is too late. The fumes are carried over Delhi where the air often stagnates due to geographical and meteorological factors, forming a blanket of heavily polluted air. When we say heavily, we mean polluted beyond the highest categorized levels of pollution. 

Pm2.5 air pollution daily averages from May 2016 to Early 2021. Source: Berkeley Earth.

Stubble burning usually occurs in November which coincides with the wild peaks you see in the graph above. Of course, these are short-lived while transportation, industry, open waste burning and road dust keep the levels within the unhealthy (red) to hazardous (purple) range most of the time. 

What does this translate to in health terms? As you can see above, Berkeley Earth uses an interesting analogy for air pollution, converting fine particulate matter’s (PM2.5) effect into cigarettes smoked. We used this data to make a map of Delhi’s density and PM2.5 exposure in 2016 (latest available PM2.5 data), which remains relevant because not much has changed in the last 4 years. 

Air pollution mapping in Delhi. PM2.5 data from NASA-SEDAC (2016).

At best, people in Delhi breathe enough air pollution to cause the same detrimental effects as 31 cigarettes per week, when averaged over a year. Further, the worst of the pollution occurs in the most densely populated areas. The situation is unacceptably dangerous and it is incumbent on authorities to take the necessary measures and fix it; but what would those be? 

It wasn’t long ago that the region lacked sustenance to the point it relied on food aid from neighboring regions. Green revolution methods allowed farmers to achieve food surplus in the 1970s, but this came with excessive groundwater drainage which had to be regulated. Laws forcing farmers to wait until monsoon rains to plant certain crops left them with little time to go from summer to winter crops as mentioned earlier, hence the necessary crop burning. 

On the other hand, India’s development, while fast, is far from ready to solve its traffic crisis. The public transportation network is flourishing, but lacks the capacity needed to accommodate 20 million people. To illustrate, Delhi is 14 times the size of Paris, yet has only twice its metro length.

Much can still be done, and many blame officials for their lack of urgency. Energy comes mainly from coal, and the region has made little headway on the conversion to renewables. Air quality monitoring is poor, and a dearth of information encourages apathetic responses. The situation is clearly bad enough to warrant stronger incentives or regulations for reduced vehicle usage, yet nothing of the sort has come up. It will take a concerted effort by the local government to redirect time and resources toward solving the pollution problem at the cost of short-term productivity and profit. In the long run however, the improved quality of life will pay this back two-fold, as reduced disease burden, better circulation and sustainable energy options will ensure a bright future for the city. 

This article was written by Owen Mulhern. 

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