What is AQI — and how is the air quality in Delhi after Diwali this year?

Sub: Env

Sec: Pollution

Context:

The Air Quality Index (AQI) in New Delhi was around 351 on November 1, the day after Diwali. Despite the ban on firecrackers in the national capital, various parts of the city saw violations.
However, after Diwali, the pollution levels did not aggravate to the levels generally observed in recent years due to increased wind speeds post Diwali, which helped disperse pollutants.

Factors contributing to Poor Air Quality in Delhi:

Meteorological Conditions: The onset of winter brings cool, dense air that traps pollutants close to the ground.
Stubble Burning: Agricultural practices in neighbouring states, particularly Punjab and Haryana, where farmers burn stubble, add to the pollution levels.
Firecrackers: Despite the ban on firecrackers, violations are common during Diwali.
Road Dust and Vehicular Emissions: Increased Road dust and pollution from vehicles contribute significantly to the poor air quality.

Air Quality Index:

Launched in 2014 with One Number – One Colour -One Description for the common man to judge the air quality within his vicinity.
The measurement of air quality is based on eight pollutants, namely: Particulate Matter (PM10), Particulate Matter (PM2.5), Nitrogen Dioxide (NO2), Sulphur Dioxide (SO2), Carbon Monoxide (CO), Ozone (O3), Ammonia (NH3), and Lead (Pb).
Each of these pollutants is given a weight based on a formula. That weight depends on the kind of impact it has on human health.
AQI has six categories of air quality. These are: Good, Satisfactory, Moderately Polluted, Poor, Very Poor and Severe.
It has been developed by the CPCB in consultation with IIT-Kanpur and an expert group comprising medical and air-quality professionals.

How does the AQI influence government policy:

The AQI influences government policies and emergency measures to combat air pollution, particularly in Delhi. The Graded Response Action Plan (GRAP) has been implemented to address air quality deterioration. Previous actions under this plan have included:
Bans on coal and firewood use, including in restaurants and tandoors.
Restrictions on diesel generator sets, except for emergencies.
Increased parking charges to discourage the use of private vehicles.

Impact of PM 2.5:

Particulate matter (PM) 2.5 is particularly dangerous due to its small size, measuring less than 2.5 micrometres.
These particles can penetrate deep into the lungs and enter the bloodstream, leading to serious health issues such as respiratory diseases, asthma, heart attacks, and bronchitis.