History of Air quality index in Timeline

The Air Quality Index (AQI) is a tool used by government agencies to inform the public about current and forecasted 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 issues. Public health recommendations during high AQI events often include reducing outdoor physical activity or avoiding going outside altogether. In cases of wildfire-related pollution, mask usage outdoors and air purifier use indoors are also advised.

1968: AQI made its debut

In 1968, the AQI made its debut. The National Air Pollution Control Administration developed an air quality index and to apply the methodology to Metropolitan Statistical Areas.

1990: Clean Air Act (USA) requires EPA to review NAAQS

The Clean Air Act (USA) of 1990 requires the EPA to review its National Ambient Air Quality Standards every five years.

2006: Common Air Quality Index (CAQI) used in Europe

In 2006, the Common Air Quality Index (CAQI) started to be used in Europe.

2011: N Seoul Tower illuminated

In 2011, the N Seoul Tower was illuminated on days where the air quality in Seoul is 45 or less.

2012: CAQI components defined

As of 2012, 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.

2012: N Seoul Tower illuminated for 52 days

During the spring of 2012, the N Seoul Tower in South Korea was lit up for 52 days, which is four days more than in 2011, on days where the air quality in Seoul is 45 or less.

2012: CiteairII evaluation of the CAQI

In 2012, the EU-supported project CiteairII argued that the CAQI had been evaluated on a "large set" of data, and described the CAQI's motivation and definition.

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

As of January 1, 2013, China's Ministry of Environmental Protection (MEP) began monitoring daily pollution levels in 163 of its major cities, basing the AQI level on six atmospheric pollutants.

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 AQHI is measured on a scale of 1 to 10+ and considers ozone, nitrogen dioxide, sulfur dioxide, and particulate matter.