This scary time of the year may have arrived in the Delhi-NCR region as Chief Minister Arvind Kejriwal announced that the air quality in the capital had fallen to a “very poor” category on Sunday morning, due to burning rubble in neighboring states.
At 2 pm on Sunday, Delhi’s air quality index was 339, which is in the “extremely poor” category but what is the air quality index and why do governments use the number to assess pollution? News 18 Explain:
How is AQI measured?
The Air Quality Index is a number used by government agencies to assess and report levels of air pollution to the public. A high AQI indicates unfavorable health effects for a large proportion of the population.
It is measured using an air sensor and the concentration of air pollutants over a predetermined average period. The results are categorized into bands, with each band receiving a descriptor, color code, and a standardized public health consultation.
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Historically, all continents have used the U.S. Environmental Protection Agency (EPA) AQI. When several pollutants are measured at a monitoring site, the highest value of the AQI is given in the 1 hour average for that site. However, each country’s air pollution is very distinct to the type of pollution in the country, according to reports.
What pollutants does the air quality index measure?
The AQI is calculated by the Environmental Protection Agency (EPA) for five primary air pollutants for which national air quality limits have been set to protect public health.
1. Ground level ozone
2. Particulate matter/particle pollution (PM2.5/pm 10)
3. Carbon Monoxide
4. sulfur dioxide
5. nitrogen dioxide
AQI Point Scale for India
Different countries report air quality using different point scales. In the United States, for example, a rating between 0 and 50 is considered good on a 500-point scale. A rating from 301 to 500 is considered dangerous. India also uses a 500-point scale. Every day, significant pollution concentrations are recorded by the monitors. Using standard equations developed by the Environmental Protection Agency, these raw values are converted to a single AQI value for each pollutant (ground level ozone, particulate pollution, carbon monoxide, and sulfur dioxide). These highest AQI values are reported as the AQI for the day, according to this business standard Report.
The following are the quality classes for AQI:
• 0-50: good – little effect
• 51-100: satisfactory Some people with predisposed health conditions may have mild breathing difficulties.
• 101-200: moderately polluted It may cause breathing difficulties in people with lung diseases such as asthma, as well as discomfort in people with heart diseases, children and the elderly.
• 201 – 300: bad It may cause breathing problems in people exposed for a long period of time, as well as discomfort in people with heart disease.
• 301 – 400: very poor Prolonged exposure to this AQI level may lead to respiratory disease. People with lung and heart disorders may be particularly affected.
• 401-500: severe – May cause respiratory problems in healthy people, as well as major health problems for people with lung/heart disease. Difficulties can occur even during light physical exertion.
History of AQI
The US National Air Pollution Control Administration launched an attempt in 1968 to build an air quality index and apply the concept to urban statistical areas, which led to the creation of the AQI. The motive was to draw public attention to the issue of air pollution and, in turn, to compel responsible local government officials indirectly to take action to reduce pollution sources and improve air quality within their jurisdictions, reports say.
The head of the National Air Pollution Emissions and Monitoring Inventory Branch, Jack Finsterstock, is tasked with leading the development of the technology and the compilation of air quality and emissions data required to test and calibrate the resulting indicators.
The first generation of the Air Quality Index produced individual pollutant indices based on standardized concentrations of ambient pollutants. These indicators were then weighted and added together to create a single overall air quality index.
Where to check AQI in India?
AQI terms for different states and cities can be checked on the Central Pollution Control Agency’s website or Twitter handle.