History of Air quality index in Timeline

The Air Quality Index (AQI) is a tool used by governmental bodies to inform the public about current and forecast air pollution levels and associated health risks. A higher AQI signifies greater pollution and increased risk, particularly for vulnerable populations like children, the elderly, and those with respiratory or cardiovascular conditions. During periods of high AQI, especially due to events like wildfires, authorities typically advise reducing outdoor activity, using masks outdoors, and employing air purifiers indoors.

1968: Debut of the Air Quality Index

The Air Quality Index made its debut in 1968, when the National Air Pollution Control Administration undertook an initiative to develop an air quality index and to apply the methodology to Metropolitan Statistical Areas.

1990: Clean Air Act (USA) requires EPA to review air quality standards

In 1990, the Clean Air Act (USA) requires the EPA to review its National Ambient Air Quality Standards (NAAQS) every five years to reflect evolving health effects information. The Air Quality Index is adjusted periodically to reflect these changes.

2006: Introduction of the Common Air Quality Index (CAQI) in Europe

In 2006, the Common Air Quality Index (CAQI) was introduced for use in Europe.

2011: N Seoul Tower illuminated in blue for good air quality

During the spring of 2011, the N Seoul Tower on Namsan Mountain in central Seoul, South Korea, was illuminated in blue for 48 days when the air quality in Seoul was 45 or less.

2012: Definition and components of the Common Air Quality Index (CAQI) as of 2012

As of 2012, the CAQI is a number on a scale from 0 to 100, where a low value means good air quality and a high value means poor air quality. The index is defined in both hourly and daily versions, and separately near roads or away from roads. The CAQI had two mandatory components for the roadside index, NO2 and PM10, and three mandatory components for the background index, NO2, PM10 and O3. It also included optional pollutants PM2.5, CO and SO2.

2012: N Seoul Tower illuminated in blue for good air quality

During the spring of 2012, the N Seoul Tower on Namsan Mountain in central Seoul, South Korea, was illuminated in blue for 52 days when the air quality in Seoul was 45 or less.

2012: CiteairII argued the CAQI had been evaluated on a "large set" of data

In 2012, the EU-supported project CiteairII argued that the CAQI had been evaluated on a "large set" of data. CiteairII stated that having an air quality index that would be easy to present to the general public was a major motivation, leaving aside the more complex question of a health-based index. The main aim of the CAQI was to encourage wide comparison across the EU, without replacing local indices, and to attract attention to urban air pollution and its main source (traffic).

January 1, 2013: China's Ministry of Environmental Protection monitors daily pollution levels

As of January 1, 2013, China's Ministry of Environmental Protection (MEP) began monitoring daily pollution levels in 163 major cities. The AQI level is based on six atmospheric pollutants: sulfur dioxide (SO2), nitrogen dioxide (NO2), PM10, PM2.5, carbon monoxide (CO), and ozone (O3), measured at monitoring stations in each city.

December 30, 2013: Hong Kong replaced the Air Pollution Index with a new index called the Air Quality Health Index

On December 30, 2013, Hong Kong replaced the Air Pollution Index with the Air Quality Health Index (AQHI). The Environmental Protection Department reports this index on a scale of 1 to 10+, considering ozone, nitrogen dioxide, sulfur dioxide, and particulate matter (PM10 and PM2.5). The AQHI calculates the sum of the percentage excess risk of daily hospital admissions attributable to the 3-hour moving average concentrations of these four pollutants and groups the AQHIs into five health risk categories.

September 17, 2014: Launch of the National Air Quality Index (NAQI) in New Delhi

On September 17, 2014, the National Air Quality Index (NAQI) was launched in New Delhi under the Swachh Bharat Abhiyan.

2014: IIT Kanpur and the Expert Group recommended an AQI scheme in 2014

In 2014, IIT Kanpur and the Expert Group recommended an AQI scheme to the Central Pollution Control Board along with State Pollution Control Boards. The new index measures eight parameters. The continuous monitoring systems that provide data on near real-time basis are installed in New Delhi, Mumbai, Pune, Kolkata and Ahmedabad.

November 2017: European Environment Agency announced the European Air Quality Index (EAQI)

In November 2017, the European Environment Agency announced the European Air Quality Index (EAQI) and started encouraging its use on websites and for other ways of informing the public about air quality.

November 12, 2019: Vietnam Environment Administration issued Decision on Technical Guidelines for VN_AQI

On November 12, 2019, Vietnam Environment Administration issued Decision No. 1459/QD-TCMT on promulgating Technical Guidelines for calculation and publication of Vietnam Air Quality Index (VN_AQI).

November 2024: Highest AQI recorded in New Delhi

In November 2024, the highest AQI in India was recorded in New Delhi on 18th with a value of 1,081. This high AQI was accompanied by a high concentration of PM2.5, which is particulate matter measuring 2.5 microns or less in diameter that can be carried into the lungs and cause deadly diseases and cardiac issues.