Why is everyone talking about Delhi pollution? How is it measured?

Delhi, known for consistently breaking its own air pollution records, faces an unprecedented crisis this year. The Delhi Directorate of Education has taken the drastic step of urging all schools in the city to postpone their winter vacations due to the alarming levels of pollution. According to the Central Pollution Control Board (CPCB), the Air Quality Index (AQI) on Thursday was a staggering 454.

The AQI, a standard unit to measure air quality, categorises levels as good, moderate, unhealthy for sensitive groups, unhealthy, very unhealthy, and hazardous, ranging from 0 to 500. Delhi’s AQI has consistently fallen into the hazardous category in recent years, signaling a troubling trend.

Swiss tech company IQ Air reports that among 109 cities with air pollution issues, Delhi ranks as the most polluted, followed by Lahore in Pakistan and Kolkata. Notably, another Indian city, Mumbai, holds the tenth position on this list with a high AQI.

What are PM2.5 and PM10? Why are these levels worrisome in Delhi?

The escalating issue of pollution is a global concern, exacerbated by rapid industrialisation worldwide intersecting with climate change. According to World Health Organization (WHO) guidelines, outdoor pollution encompasses six types: PM2.5, PM10, O3, NO2, SO2, and CO, with the first two identified as the most dangerous pollutants.

PM2.5 and PM10, both Particulate Matters comprising various chemical species, pose significant threats to air quality. PM2.5 consists of particles with diameters of 2.5 or smaller, originating from sources like gasoline combustion, diesel fuel, and wood oil. In contrast, PM10 includes particles with a 10-diameter size, often associated with dust particles, industrial waste, and landfills. These particles are either directly emitted from sources or formed in the atmosphere through chemical reactions.

The health effects linked to this type of air quality are diverse and severe, contributing to asthma attacks, premature mortality, and bronchitis. Vulnerable populations, including older individuals with preexisting health issues, as well as children and infants, are particularly at risk. Delhi’s recurring issues with PM2.5 levels underscore the gravity of the situation.

According to a 2022 US-based report, ‘Air Quality and Health in Cities,’ which analyses pollution and global health effects based on data from 2010 to 2019, Delhi ranks at the top among 7,000 cities worldwide. The city exhibits an annual average exposure of 110 µg/m3, highlighting a worrisome trend that demands urgent attention.

Is the pollution due to stubble burning in Punjab and Haryana?

In a recent meeting convened by the Union Government, senior officers from Punjab, Haryana, Uttar Pradesh, Rajasthan, and Delhi concluded that stubble burning constitutes a significant contributor, accounting for 38 per cent of the escalating air pollution crisis. The situation is worsened by the rice-wheat rotation system which generates substantial amounts of stubble. The burning period in October-November coincides with stubble burning, causing the NCR to bear the brunt, resulting in a surge in the AQI.

The October 2021 report from the CPCB underscores crop residue burning as a substantial contributor to the deteriorating AQI in the NCR region during the winter season. This poses significant risks to public health, affecting lung function and creating challenges in waste disposal. The economic cost of pollution due to crop residue burning is staggering, amounting to a loss of nearly ₹2.35-lakh crore annually in States such as Delhi, Punjab, and Haryana.

What are the other long-term causes for Delhi pollution?

While stubble burning remains a significant contributor to the escalating pollution levels in Delhi, transportation poses another substantial challenge. According to the Indian Institute of Tropical Meteorology’s DSS data, Delhi’s transportation system alone accounts for 11 per cent of the pollution in the NCR. The pollution landscape in Delhi is complex and extends beyond stubble burning. Major issues such as waste burning, industrial pollution, and road construction activities also contribute significantly to the pollution in the city.

Why is the pollution in Delhi high in November?

Over the years, Delhi has consistently grappled with a pervasive smog phenomenon. Historically, the Indo-Gangetic region experienced a cooling trend in December-January, fostering foggy conditions since 1997. However, in the last decade, November has emerged as the focal month for heightened air pollution in Delhi, primarily attributed to the practice of paddy burning.

The Punjab Preservation of Subsoil Water Act of 2009 restricted farmers from sowing paddy before May 15 and transplanting before June 15. This delay in agricultural activities has subsequently pushed the harvesting season from mid-October to November, characterised by low wind speeds and higher moisture content. These conditions trap pollutants, culminating in a denser smog, thus contributing significantly to the escalated pollution levels in November.

What is the Delhi government doing to fight pollution?

On September 28, the Arvind Kejriwal government unveiled the Winter Action Plan to combat air pollution in Delhi. The plan encompasses 15 key measures targeting stubble burning, vehicular emissions, open burning, and other contributors to pollution. Identifying 13 hotspots as major pollution sources, the government’s strategy aims to address each of these areas.

The Kejriwal government has reintroduced the odd-even rationing scheme from post-Diwali. Under this scheme, vehicles with odd and even numbers will be permitted on alternate days.

In parallel, the Delhi Development Committee (DDC) has proposed ten recommendations to the government for controlling air pollution in the city. These suggestions include a ban on crackers during Diwali, promotion of air pollution masks, and regulation of garbage burning, among others.