德里的空气质量

How polluted is the air in Delhi?

As the capital city of India, Delhi is subject to a high level of pollution year-round. The levels of fine and coarse particulate matter, known respectively as PM2.5 and PM10 are often prevalent in the air, as well as other forms of pollutants and toxic chemicals finding their way into the atmosphere, each with their own detrimental effects on human health. There are an estimated 30.2 million people registered living in Delhi as of 2020, all squeezed into a relatively small area of 1,484km², giving it an extremely high population density.

In 2019 it ranked in with a PM2.5 reading of 98.6 µg/m³, putting it in the ‘unhealthy’ bracket of the US Air Quality Index, which requires a PM2.5 reading anywhere between 55.5 to 150.4 µg/m³. For a city to be in the unhealthy bracket as a year-round average, it is an indicator that there are significant health hazards from the air quality. Pollution levels on the ground must be extremely high to maintain such an average, and it is well known that Delhi struggles with its population growth, with many ‘urban diseases’ becoming more and more apparent as the city struggles to keep up with the ever-expanding population. This would put the city under immense pressure to improve its both its residential and commercial infrastructure. As such, a result of this would be an increase in nearly all industries and a related increase in pollution directly correlating with the industrial and economic growth.

More citizens mean more cars on the road as well as more buses and trucks to transport goods and people. The vehicular emissions given off by these would be of an extremely high volume, with an estimated 11.2 million registered motor vehicles on the roads as of 2018, an increase of around 27 percent since 2015. This considerable increase plays a very important part in establishing Delhi as a city with some of the worst air quality in the world. This term as one of the most polluted cities in the world holds true when you observe the PM2.5 data readings taken over 2019 on the IQAir website. It ranked in as the 2nd most polluted city in the whole of India, coming in just behind the number one most polluted city of Ghaziabad, displaying numbers that give it an extremely high rating of 110.2 µg/m³.

Furthermore, Delhi managed to take 5th place out of every city worldwide. This placing, along with its 2019 rating falling into the unhealthy bracket, as well as three months out of the year going up a notch into the ‘very unhealthy’ bracket would indicate that Delhi is suffering from extremely high levels of pollution, being one of the world's leaders in poor air quality with extremely high amounts of PM2.5, PM10 and other noxious chemicals and smoke permeating the atmosphere.

When is the air quality and pollution in Delhi at its worst?

The US AQI rating as well as readings of PM10 and PM2.5 are at their worst in the later months of the year as well as January, due to changes in weather and the burning of crops and forestland. These practices, known as slash and burn farming, have been around traditionally for quite some time, but have recently come under more intense scrutiny and both local and international pressure to have them stopped, as the effects of these practices on a large scale, coupled with a population and industry boom, all combine to create the disastrous levels of pollution that are being currently observed.

Slash and burn farming methods are a practice that is becoming more and more of a problem in certain parts of the world, with vast sections of Asia as well as South East Asian countries suffering from its pollutive fallout. In regards to Delhi, it can be observed on the 2019 PM2.5 rating that the worst months were January, November and December respectively, with numbers beating out the other months by quite an extensive amount. January came in with a reading of 191.7 µg/m³, after which it dropped by half down to 84.8 µg/m³ in February, and continued to decline for the rest of the year until it observed a subtle rise in September, and then a sudden massive spike in PM2.5 readings in October of 116.7 µg/m³, an increase of 79.5 µg/m³ between the month of September and October, showing just how significant the change in pollution levels towards the end of year really are, and what appropriate actions can be taken against them, which will be discussed in further detail later on. To end, November and December average PM2.5 readings of 220.7 µg/m³ and 194.8 µg/m³, both in the ‘very unhealthy’ bracket, a level of air quality so bad that it would have a number of both disastrous long- and short-term effects, regardless of whether people are healthy or have preexisting respiratory conditions. So, whilst three months of the year held the worst US AQI and PM2.5 levels, it was November that came in as the worst offender.

What are the main causes of the high levels of pollution in Delhi?

The main causes of pollution in Delhi are numerous, with each aspect able to warrant a sizeable essay in of itself. To start by naming a few, one of the main culprits is of course vehicular emissions. With such a huge number of cars present in the city, many of which have engines of questionable quality (particularly in regards to the old trucks, lorries and buses) they would put out extremely high volumes of smoke and haze, coating the city in soot and black carbon (BC), a form of carbon that is very harmful to all living creatures, caused by the improper combustion of fossil fuels and various forms of organic matter, such as food waste and forest/farm land being set ablaze.

As mentioned before, a change in seasons has also contributed to the worsened air quality, with winter air pollution being particularly severe in nature because farmers in surrounding regions burn leftover plant matter or stubble, to clear land after the September harvest. This coincides with weather changes such as wind speeds dropping as well as a reduction in rain that should ideally be there to help clear the pollution, but with its absence the smog remains in the atmosphere with nothing to assist in cleaning it out.

In terms of topography, Delhi is at a distinct disadvantage because of its location and how the wind and its direction directly affect pollution accumulation in the air. It is known that the winds blowing into Delhi can bring with them large amounts of smoke and haze from other parts of the region, and when winter comes around these winds often die out, leaving the accumulated pollution trapped in Delhi’s atmosphere with nowhere to go. Furthermore, as the air temperature drops during the winter months, the pollutants in the air find themselves lowered in elevation, leading to a cocktail of pollutants mixing together, forming the previously mentioned haze that blankets the city. This plays a larger role in the levels of pollution than one might imagine, with an estimation in 2019 stating the dust blown in by the winds accounted for approximately 21.5 percent of all pollution in Delhi.

Revisiting the issue of pollution caused by cars, with its excess of 11 million vehicles on the road, the sheer volume of smoke and PM2.5 put out by these various cars, buses and trucks, would be enough to warrant it as being the largest cause of high levels of pollution in Delhi, with vehicles accounting for an estimated 41 percent of overall pollution in the capital.

Whilst there are many more causes of pollution and smog to be pinpointed, the last main one to be discussed is the industrial sector, with a large number of factories and production plants of varying sorts dotted all over the city, they would also play a considerable role in regards to the release of smoke into the atmosphere. In fact, during periods of pollution-based emergencies, it has been known for fuel and coal-based factories to be ordered closed as a drastic measure to halt the catastrophic rise of pollution levels. An estimated 18.6 percent of total air pollution in Delhi comes from the industrial sector, with somewhere in the order of several hundred to over a thousand tons of pollutants released into the atmosphere over the course of the year from factories alone. It is with little surprise that readings of PM2.5 have been recorded soaring up to 829.2 µg/m³, more than 80 times the WHO’s (World Health Organization) recommended annual level.

What are the health effects of air pollution in Delhi?

In 2017 alone, India's air pollution was linked to the deaths of 1.24 million people, with 54 percent of the deaths caused by ambient air pollution and 46 percent of the deaths caused by household pollution such as solid cooking fuels. It is estimated that air pollution deaths accounted for 12.5 percent of all total deaths recorded that year.

Focusing in on Delhi in more recent years, and the health effects that breathing such highly polluted air could bring about, one can examine the effects of PM10 and PM2.5 on a person’s health, due to both long- and short-term effects being well documented. Particulate matter of 10 or less micrometers across (PM10) can find its ways into people’s respiratory tracts, causing irritation and infections to occur in the eyes, nose and throat, as well as the lungs if the particulate matter is inhaled deeply enough over longer periods of time. PM2.5 is far more lethal in nature, with its particularly fine size giving It the ability to penetrate into the deep tissues of the lungs, and then further on into the bloodstream. This can cause a variety of issues to both the respiratory and circulatory system. Chronic obstructive pulmonary disease (COPD) is a very real possibility when breathing air of such low quality, with ailments such as emphysema and chronic bronchitis falling under the COPD term, due to it being used to describe a wide variety of lung and respiratory related illnesses.

Cardiac events and various heart diseases are also possible when exposed to Delhi’s air, with the young and elderly as well as those with compromised immune systems being at particular risk, although it is important to note that that when levels of PM2.5 in the air reach into the unhealthy bracket (as is the case several times over the year in Delhi), the risk starts to apply to everyone, and even those without any preexisting conditions or a predisposition towards catching illnesses may find themselves with new conditions if heavy exposure is continued over a long enough period of time. Cancer of the lungs is also another possibility.

With such a myriad of ailments and health conditions available from breathing overly polluted air, individuals living or finding themselves travelling through such locations can take preventative measures by referring to air quality maps, such as the ones found on the IQAir website, or having real time updates available on the go via the AirVisual app, as well as taking the extra step in the line of defense by having access to higher quality masks to filter out the PM2.5 particles, as available on site.

What are some examples of other issues caused by air pollution in Delhi?

Delhi's polluted air has not only resulted in health problems for the people living there, but has disrupted the lives of some 20 million residents. In November 2019, the government declared a public health emergency, temporarily ordering schools to close and nighttime construction activities to be stopped. At other times, heavy smog has affected both air and road transport. On Nov. 3, 2019, dozens of flights were cancelled due to poor visibility. During the elevated pollution levels, hospitals in Delhi reported higher numbers of patients with respiratory problems, causing congestion in yet another sector, showing the far-reaching effects that high levels of pollution can have.

What was the most polluted day recorded in Delhi?

The most polluted day ever recorded in Delhi took place on November the 6th, 2016. It was actually during this year that public records of the level of pollution started to take place, beginning in the month of January. The U.S. Embassy in Delhi recorded a PM2.5 concentration level of 933µg/m³, a number which when compared to averages witnessed in cities around the world, borders on the extreme. The PM2.5 rating required to warrant a ‘hazardous’ rating is 250.4µg/m³ and above, and as such a reading of 933µg/m³ would have exceptionally negative consequences for anyone unfortunate enough to breath in such toxic air.

What can Delhi do to reduce its pollution levels and improve air quality?

The logical first step to move in the right direction in regards to solving Delhi’s air crisis would be by making a lot more real-time air quality data available to the general public and increasing air quality data transparency, as well as initiatives to educating people on the far-reaching consequences of breathing in low quality air. By knowing the severity of the pollution they are breathing, people can take a large number of preventative measures to protect themselves and those around them.

The key to improving air pollution is by reducing overall emissions across all offending sources, such as those occurring from the transport sector as well as the industrial sector, a task easier said than done. Indian authorities have already launched the National Clean Air Program (NCAP) which aims to cut pollution in 102 of the most polluted cities by 20-30% by 2024. Under the NCAP, the government plans to cut industrial and transport emissions, reduce dust pollution, and impose stricter rules on biomass burning. There are also plans to upgrade and increase air monitoring systems.

In regards to the burning of biomass, more stringent rules could be placed on those responsible for the mass burning of farmland and forested areas for agricultural use. Not only must these rules come into action, but they will need to be enforced as well, similar to the situation in Thailand, in regards to how farmland burning is considered highly illegal, yet continues to take place because of a lack of enforcement.

Individuals can take steps in their daily life to reduce personal emissions by having less reliance on their personal cars, or by taking public transport, as well as switching to greener fuel alternatives, with an educated consciousness on what they are burning, whether it be a pile of plastic refuse, dead organic matter or even certain food materials, all of these smaller steps can help Delhi reduce the level of pollution and slowly start moving towards improving its air quality.