As per Swiss organisation IQAir, Air pollution contributes to as many as 7 million premature deaths globally per year and costs more than $5 trillion in welfare losses. According to IQAir's world air quality report 2020, air quality in every Indian city improved compared to 2018 while 63 per cent saw direct improvements against 2019. However, India is still home to 22 of the 30 most polluted cities in the world. In 2019, India launched the 'National Clean Air Programme' proposing a “tentative national target” of 20 to 30 per cent reduction in PM 2.5 and PM 10 concentrations by 2024, with 2017 as the base year for comparison.
AQI is a yardstick to measure the quality of air in a given area. It is measured from 0 to 500. A higher value of AQI denotes a greater level of pollutants in the air and hence a more severe impact on health. The AQI index is divided into six categories, each corresponding to a different level of health concern.
- Green (0-50) - Good
- Yellow (51-100) - Moderate
- Orange (1001-150) - Unhealthy for sensitive groups
- Red (151-200) - Unhealthy
- Purple (201-300) - Very unhealthy
- Maroon (301 and higher) - Hazardous
Several factors are responsible for poor air quality in a region. These include the level of various pollutant gases and suspended particulate matter (PM10 and PM2.5). Particulate Matter (PM) is made up of particles (tiny pieces) of solids or liquids that are in the air. Breathing in Particulate Matter can be harmful to health. Coarse (bigger) particles, called PM10, cause irritation in the eyes, nose, and throat. Dust from roads, farms, dry riverbeds, construction sites, and mines are types of PM10. Fine (smaller) particles, called PM2.5, are more dangerous because they can get into the deep parts of your lungs — or even into your blood.
A major reason behind the poor air quality in Northern India is stubble burning by farmers in Punjab and Haryana. The smoke from these farm fires is trapped in a windless atmosphere over much of the north making the air unbreathable. A study estimated that crop residue burning releases 149.24 million tonnes of carbon dioxide (CO2), over 9 million tonnes of carbon monoxide (CO), 0.25 million tonnes of oxides of sulfur (SOX), 1.28 million tonnes of particulate matter, and 0.07 million tonnes of black carbon.