History of Air quality index in Timeline

The Air Quality Index (AQI) is a tool used by governments to inform the public about current and forecast air pollution levels and associated health risks. A higher AQI indicates greater pollution and increased risk, especially for vulnerable groups like children, the elderly, and those with respiratory or cardiovascular issues. High AQI days may prompt recommendations to reduce outdoor activities or, during wildfires, to use masks outdoors and air purifiers indoors, as protective measures.

1968: Debut of 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 every five years to reflect evolving health effects information.

2006: Common Air Quality Index used in Europe

In 2006, the Common Air Quality Index (CAQI) was first used as an air quality index in Europe.

2011: N Seoul Tower lit up for 48 days

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

2012: CAQI scale defined in hourly and daily versions

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 extremely poor air quality. The index is defined in both hourly and daily versions, and separately near roads or away from roads.

2012: N Seoul Tower lit up for 52 days

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

2012: CiteairII argued 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 and that it was mainly designed to attract attention to urban air pollution and its main source (traffic) and help people decrease their exposure.

January 1, 2013: China's MEP monitors daily pollution level in 163 major cities

On January 1, 2013, China's Ministry of Environmental Protection (MEP) started 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).

December 30, 2013: Hong Kong replaced Air Pollution Index with Air Quality Health Index

On December 30, 2013, Hong Kong replaced the Air Pollution Index with the Air Quality Health Index (AQHI). The index, reported by the Environmental Protection Department, is measured on a scale of 1 to 10+ and considers ozone, nitrogen dioxide, sulfur dioxide and particulate matter (PM10 and PM2.5).

September 17, 2014: National Air Quality Index launched 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 recommended an AQI scheme

In 2014, IIT Kanpur and an Expert Group recommended an AQI scheme. The new index measures eight parameters, while the earlier measuring index was limited to three indicators.

November 2017: European Environment Agency announced the European Air Quality Index

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

November 2024: Highest AQI recorded in New Delhi

In November 2024, the highest AQI in India was recorded in New Delhi with a value of 1,081, due to high levels of PM2.5 - particulate matter measuring 2.5 microns or less in diameter that can be carried into lungs, causing deadly diseases and cardiac issues.