The University of Chicago launched a new tool called Air Quality Life Index (AQLI) which quantifies air quality data as the number of years lost to air pollution. According to this data, Indians will lose an average of 4.3 years of their life due to air pollution. Residents of Lucknow will lose 9.4 years, 7.7 years for Patna, 9.3 for Mathura, 8.7 for Gurgaon, 5.9 for Ludhiana and 6.1 years for Gwalior. The data is more hopeful for southern cities. Mumbai is at 2.9, Bengaluru at 1.7, and Chennai residents stand at losing 1.9 years.

Unsurprisingly, this list is led by Delhi. The perpetual chokeslam of dirty air will cost the residents of Delhi 10.2 years of their life. Bringing the air quality under WHO’s limits will save an entire decade of life for Delhiites, which otherwise would be inconspicuously taxed by dirty air for living in the capital.

The AQLI world map has a blood-like stain on Northern India.

The science behind the number

AQLI is particularly insightful because it depicts air quality as its impact on life expectancy. The earlier researches that estimated the loss to life expectancy were either observational or were obtained by extrapolating data from research done on cigarette consumption. These associational studies were usually carried out in the US and were not representative of the air in Asian countries that have multiple times more particulate matter. The research that this new AQLI is based on was done with these shortcomings in mind.

Conducted in China, this peer-reviewed research was published in PNAS, a renowned scientific journal. The researchers built on the existing policy of the region which provided free coal to Northern China but restricted the access of coal in the southern part. The burning of fossil fuel is one of the leading causes of particulate matter pollution. This helped the researchers measure the air quality and health impact on the residents of both the region for a very long time. They found that an additional 10 μg per cubic meter increase in particulate matter leads to 0.6 years of decrease in lifespan. Along with being extremely robust and large-scale, the design of this quasi-experiment also helped them understand the impact of bad air on the human body in isolation with the usual confounding effect. The findings of this study were used to build AQLI.

But where are the 10 years?

For Delhiwalas, it is important to understand this number—10.2 years. Where will this 10-year period really go? You can’t just subtract 10 years from your future old age; it’s a lot harder to get rid of it. This 10-year period will translate into worsened respiratory and cardiac health amongst other ailments. This decrease in lifespan will either be directly due to particulate pollution or by exacerbation of unrelated existing conditions that will eventually lead to unexpected death or disability. Multiple studies, including some large-scale ones with over 66,000 patients, have had found this strong co-relation between air pollution and heart health. Bad air contributes to early deaths due to cardiovascular diseases like heart failure, stroke and arrhythmia (irregular beating of the heart). An example of exacerbation of a pre-existing condition was found in this 2002 paper that concluded that exercising or working in a polluted atmosphere significantly increases the odds of a heart attack in patients with a history of cardiac ailments.

WHO has classified air pollution as a group 1 carcinogen (cancer-causing agent) in humans due to an overwhelming evidence that links it to cases of lung and bladder cancer. Long-term exposure to fine particulate matter has been known to cause premature death by lung cancer (has one of the lowest survival rates) Other non-fatal conditions due to exposure are irritation, chronic inflammation of airways, cyst formation in the lung, COPD, asthma, bronchiectasis and many other respiratory ailments.

Chronic air pollution has been increasingly linked to cerebrovascular and neurodegenerative diseases like Alzheimer’s. It has also known to worsen dermatological conditions. Unrelated diseases like diabetes have shown a strong association with particulate pollution. Long-term exposure to the same is also linked with a decrease in renal function and many other kidney diseases. It is also known to decrease intelligence and cognition along other metabolic functions.

All these damages are cumulative in nature—they keep compounding for every year that you have lived in Delhi. It is hard to undo all these years of damage done by dirty air. Yet it is shocking how a prescription as simple as clean air can do so much for your body.

Delhi and Diwali

If you can’t remember the exact dates of Diwali, here is the graph of PM 2.5 levels from Berkeley Earth. The peaks might help you guess the date. Diwali significantly worsens Delhi’s air. A trend that CPCB and other research reports agree with.

PM 2.5 levels from Berkeley Air’s real-time air monitoring.

PM 2.5, is the level of particles in the air that are of the size less than 0.00025 cm, around 3 per cent the width of human hair. This type of particulate matter is one of the most dangerous pollutants as it can travel from lungs into the bloodstream. Air Quality Index or AQI is defined as an overall scheme that transforms weighted values of individual air pollution related parameters (PM 2.5, PM 10, SO2, CO, visibility, etc.) into a single number.

Why is Delhi in this distress?

Who is really responsible for this gas chamber? Like most simple questions, this has an incredibly complex answer. It is really hard to study something as global as air pollution in isolation. One of the ways to study the causes of air pollution is the capture these PM 2.5 and PM 10 particles and study their molecular characteristics and use those chemical signatures to unearth the source. A 660-page long study by NEERI estimates that of all half particulate matter pollution to origin from road dust. Other studies by IIT Kanpur and TERI found similar results. While air pollution is primarily driven by particulate emission, other factors like SO2, CO, NOx, HC emission too play an important role. Their sources are linked to industries and vehicles. Subtle burning, garbage burning, residential bio-fuel and indoor emission are other major sources. The contribution of these sources vary widely from time to time and report to report.

To complicate this further, there exists a different ball game of geographical phenomenon, weather and wind patterns that can significantly impact air quality. For example, a 2015 paper found that emission from China was travelling all the way to the US and decreasing the air quality there. This unpredictability makes air pollution mitigation more frustrating.

What next?

Last week, most schools and colleges in California were closed down in light of hazardous air quality caused by the surrounding wildfire. This decision was taken because the reading on the Air Quality Index (AQI) had surpassed the 200 mark, making it unfit for humans. It was sort of disturbing because a 200 score in Delhi means a relatively good day. The worst day for the rest of the world is still better than Delhi’s best days.

The director general of WHO said air pollution is the new tobacco. It indeed is the new tobacco, but one you can’t quit even if you want to. In the discourse, we often forget that the most disadvantaged population is the most vulnerable to this “airpocalypse”. With no air filtered rooms and masks to hide behind, they are the ones who often bear the burden of 10.2 years. About 170 kids under the age of five die each day because of air pollution. They are mostly from households that are deprived of early diagnosis and good medical care. Despite being a bipartisan subject, air pollution and climate change barely get the attention it deserves.

Even from a strictly economic perspective, bad air and climate change have the ability to cripple our economy. According to a World Bank report, air pollution will cost India $560 billion in damages. This will collectively be as welfare cost an forgone labour input. India will lose 5.4 billion years of life directly due to air pollution. It will directly kill one million Indians each year. Average life expectancy lost due to dirty air is 77 times more than that of conflict and terrorism. If only air pollution has as much theatrics as terrorism does.

Fighting this filthy air will require a robust policy from the centre that focuses on long-term relief and proper implementation. This sadly is not new. 20 years ago, Delhi was at the same crossroad. Plans and rules were designed, but they made little difference. The consequences of the last 20 years cannot be changed, but the fate of the next 20 can. The current graded response action plan is a tiny band-aid for a profusely bleeding “air-mageddon”. Unless we get serious about this dirty air, the future of Delhi will end up being as hazy as its smog.