Why New Delhi remains the world's most polluted capital

Smog and murky skies in northern India from smoke and air pollution have been a constant source of poor health for many years. During the crop burning season, smoke from neighboring Pakistan and rural northwestern Indian states creates hazardous air pollution, limiting visibility and exposing residents to a range of smoke-related symptoms and illnesses, including acute respiratory infection, asthma, and pulmonary disease.

Air quality in India is a major health concern, especially pervasive in the nation’s largest metropolis, Delhi, where multiple urban sources of air pollution mingle with crop fire smoke. The combination is deadly and can cause some of the worst air quality on Earth.

In 2021, four of the five most polluted cities in the world were in India.

PM2.5, or particulate matter measuring 2.5 microns or less, is the most common and dangerous airborne pollutant. Exposure to PM2.5 is linked to many diseases, including heart and lung illness.

In 2021, four of the five most polluted cities in the world were located in India. These cities on the list included Jaunpur, Delhi, Ghaziabad, and the most polluted of them all Bhiwadi with an average annual PM2.5 concentration of 106 micrograms per cubic meter of air (μg/m3).

The poor air quality in the city of 20 million remains a growing issue today. Delhi’s average annual PM2.5 concentration was 96 μg/m3. India was the fifth most polluted country in the world, with an average annual PM2.5 concentration of 58 μg/m3.

Delhi’s average annual air pollution is 19 times greater than the WHO guideline.

In 2021, the World Health Organization (WHO) revised its annual average PM2.5 concentration exposure guideline to less than 5 μg/m3 or less. The revision was made in the face of overwhelming scientific evidence that even a small amount of exposure to PM2.5 within a short time can harm human health. Delhi’s average annual air pollution is 19 times greater than the WHO guideline.

Unhealthy air quality measured by air quality monitors in Delhi

Unhealthy air quality measured by air quality monitors in Delhi on September 9, 2022. Air quality frequently ranges from unhealthy to hazardous in the National Capital Region. Source: IQAir.

"Delhi has been the most polluted capital of the world for the last many years. The pollution levels in Delhi are consistently above the national ambient air quality standards throughout the year,” states Greenpeace India. “The air pollution crisis became a key concern for the people in the city. They are witnessing its impact in their everyday lives. Therefore, it is imperative to adopt a holistic and long-term solution to improve the air quality in the city.”

Indian officials are aware of the problem and have enacted short-term emergency measures during extremely poor air quality periods. But emergency policies reduced smog and or helped improve health (1)(2).

Administrators are adopting more robust, longer-term policies to improve air quality. By tackling sources on a broader front, there is hope for a cleaner future.

Delhi tackles vehicle emissions

As in many cities, vehicle emissions are a key source of air pollution in Delhi. In recent years, Delhi’s government has expanded rules to significantly reduce vehicle emissions by limiting road access to dirtier diesel fuel vehicles and incentivizing electric vehicle purchases.

According to Greenpeace India, “vehicular emission is one of the major contributors to Delhi’s air pollution crisis and there is an urgent need to go beyond the outdated fossil fuel-based transportation system.”

To tackle such efforts, Greenpeace India advises the city to, “adapt these three key strategies; Avoid, Shift and Improve.”

“This means avoiding and reducing the need for number and length of travel, promoting the shift from private vehicles to more environmentally friendly modes, i.e., public transport and non-motorized transport to reduce energy demand and air pollution, and improving the energy efficiency of transport modes. The government should catalyze sustainable transport by setting a comprehensive mobility plan (CMP) and creating a separate urban transport fund to ensure an efficient transportation system that prioritizes people, not private vehicles.”

In June 2022, the Commission for Air Quality Management in National Capital Region and Adjoining Areas (CAQM) announced a policy to restrict road access and phase out BS3 and BS4 diesel vehicles (3)(4)(5). The policy will be phased throughout the National Capital Region and Delhi.

Delhi has also aggressively bolstered its electric vehicle policy, with positive results. The Delhi Electric Vehicle (EV) Policy, begun in August 2020, provided purchase incentives for electric vehicle buyers. In January 2022, electric vehicle sales rose 136 percent yearly in Delhi (6).

In April 2022, Delhi's government expanded the policy to include e-cycles with a speed of fewer than 15 miles per hour (7).

“Let’s not make clean air a luxury. It’s a basic human right,” stated Greenpeace India.

Coal ban in Delhi begins

India’s government encouraged states to increase coal imports to build up reserves for the next three years due to the Russian invasion of Ukraine (8). India is already the second-largest coal importer in the world.

Coal combustion results in emissions of pollutants, including sulfur dioxide, nitrogen dioxide, particulate pollution, carbon dioxide, mercury, and other heavy metals (9).

On June 3, 2022, the CAQM required Delhi and the National Capital Region (NCR) to stop burning coal by 2023 (10).

The National Capital Region uses about 1.7 million tons of coal per year.

The rule went into effect on October 1, 2022, in places with piped natural gas (PNG) infrastructure. For those without, the ban on coal burning starts January 1, 2023. The NCR uses about 1.7 million tons of coal per year (11).

Poor air quality in the city prompted the CAQM to shutter any business not using PNG temporarily. Heavy operating restrictions like closure and restricted operations have prompted industrial operations in NCR to shift to PNG for energy use.

India’s long-standing energy policy is to reduce coal imports. However, coal-fired plants aren’t likely to be phased out soon because of coal’s relatively low cost. Even in the Delhi-NCR region, low-sulfur coal burning won’t be banned (12).

Landfills in Delhi: overfull and burning

While transportation and industrial sources of pollution are two of the most pressing sources, there are other sources and policies to address.

Delhi’s landfills pollute the air through both the odor and smoke from landfills fires.

There are three landfills ringing Delhi – Bhalswa, Ghazipur, and Okhla. A study submitted to the National Green Tribunal found that the three landfills had cost the city nearly $57 million in environmental damage. (13) The landfills pollute the air through both the odor and smoke from landfill fires.

The National Green Tribunal mandated biomining in the landfills in 2019, an effort to segregate the trash, reclaim usable resources, and help reduce the burden of a full landfill.

Okhla is scheduled to complete reclamation by March 2023, and Ghazipur and Bhalswa will follow in December 2024 – and those plans are unlikely to be met. Even though the landfills exceed their capacity, they still receive daily waste drop-offs. The competing cycle of biomining and daily trash deliveries is pushing those remediation dates decades out from their intended completion dates (14)(15).

The takeaway

Improving Delhi's air quality is an uphill struggle. It's a big undertaking. The rapidly growing city is trying to mitigate multiple sources of severe air pollution from inside and outside the city.

The most apparent pathway to reducing extremely poor air quality is to set long-term policies that significantly address the sources of air pollution. While Delhi has a lot of work ahead to improve its air quality, lives can be saved by making steady air quality improvements through smart policymaking and dedicated clean air standard enforcement.

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