Air Quality Index: Understanding The Norms And Standards

The Air Quality Index (AQI) is a tool for reporting daily air quality. It provides a simple way to communicate how clean or polluted the air is, and what associated health effects might be a concern. The AQI is a scale that runs from 0 to 500, with higher values indicating greater levels of air pollution and health concerns. For example, an AQI value of 50 represents good air quality with little potential impact on public health, while an AQI value over 300 indicates hazardous air quality. The AQI is based on federal air quality standards and includes measurements of six major air pollutants: ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, and two sizes of particulate matter.

How is the Air Quality Index calculated?

The Air Quality Index (AQI) is a uniform way to report daily air quality conditions. It is a yardstick that runs from 0 to 500, with higher values indicating greater air pollution and health concerns. An AQI value of 50 or below represents good air quality, while a value over 300 indicates hazardous air quality. The AQI is divided into six colour-coded categories, each indicating a different level of health concern: Good, Moderate, Poor, Very Poor, Severe, and Hazardous.

The AQI is calculated by converting measured pollutant concentrations into a uniform index based on the health effects associated with each pollutant. The pollutants considered for the AQI include ozone, nitrogen dioxide, sulfur dioxide, carbon monoxide, fine-particle pollution, and particulate matter (including PM10 and PM2.5). The AQI forecasts are heavily influenced by weather conditions, such as temperature, precipitation, wind, and cloud cover, as these factors affect the creation and transport of pollution.

The calculation of the AQI involves determining the concentration of each pollutant and then using specific equations to convert these concentrations into an index value. The final AQI value is calculated either per hour or per 24 hours, with the maximum value among the pollutants being the overall AQI. It is important to note that the relationship between the AQI value and the level of pollution is not linear; an AQI of 300 does not indicate twice the pollution of an AQI of 150.

The AQI is established by the Environmental Protection Agency (EPA) in the United States and is based on the National Ambient Air Quality Standards set by the Clean Air Act. The EPA reviews these standards every five years to ensure they effectively protect public health. The AQI is a valuable tool for communicating about outdoor air quality and health, helping residents make informed decisions to protect their health when air pollution levels are high.

What is considered good air quality?

The Air Quality Index (AQI) is a tool for reporting and tracking daily air quality. It is a yardstick that runs from 0 to 500—the higher the AQI value, the greater the level of air pollution and the more serious the health concern. An AQI value of 50 or below represents good air quality with little potential to affect public health. Values between 51 and 100 are generally thought of as satisfactory, but they may be unhealthy for certain sensitive groups of people. Values above 100 indicate that air quality is unhealthy for everyone. Values over 300 indicate hazardous air quality.

The AQI is divided into six colour-coded categories, each corresponding to a range of index values. These colours make it easy for people to quickly determine whether the air quality is healthy or not. For example, "code orange" days are unhealthy, and people are advised to avoid long periods of activity outdoors and to stay away from high-traffic areas. On worse "code purple" or "code maroon" days, everyone should try to stay indoors as much as possible.

The AQI is calculated based on the presence of several pollutants, including ozone (smog) and particle pollution (tiny particles from smoke, power plants and factories, vehicle exhaust, and other sources). The AQI is reported year-round through newspapers, radio, television, and websites. The public can also access maps and data visualisations that provide real-time information on current outdoor air quality.

The AQI is used by the US Environmental Protection Agency (EPA) to communicate about outdoor air quality and health. The EPA establishes an AQI for five major air pollutants regulated by the Clean Air Act. Each of these pollutants has a national air quality standard set to protect public health.

How is the AQI reported?

The Air Quality Index (AQI) is a tool used by the United States Environmental Protection Agency (EPA) to report air quality. The AQI is calculated using a piecewise linear function of the pollutant concentration. It is based on the measurement of particulate matter (PM2.5 and PM10), ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO) emissions. The AQI is measured on a scale from 0 to 500, with higher values indicating greater levels of air pollution and health concerns.

The AQI is divided into six color-coded categories, each representing a different level of health concern. These categories include:

• Code Green and Yellow: Air is generally safe for everyone.
• Code Orange: Unhealthy for sensitive groups, including children, senior citizens, and people with heart and lung diseases.
• Code Red and Purple: Air is unhealthy for everyone.
• Code Maroon: A health warning of emergency conditions.
• Hazardous air quality: Represents the highest level of health concern.

The AQI is reported in several ways, including through websites, local news media, and telephone hotlines. Real-time monitoring data and forecasts of air quality that are color-coded according to the AQI are available from the EPA's AirNow website. This website provides a map showing the real-time air quality for over 10,000 stations worldwide. Additionally, the GAIA air quality monitor uses laser particle sensors to measure PM2.5 and PM10 particle pollution and provides real-time data on air pollution levels.

Metro areas with a population of more than 350,000 are required to report the daily AQI. However, many other areas also report it as a public service. State and local agencies provide AQI forecasts, which are typically issued in the afternoon for the next day. These forecasts focus on the pollutants with the highest concentrations expected during that period.

What are the health risks of poor air quality?

The Air Quality Index (AQI) is a tool for reporting daily air quality. It runs on a scale from 0 to 500, with higher values indicating greater air pollution and health concerns. An AQI value of 50 or below represents good air quality with little potential impact on public health, while a value over 300 indicates hazardous air quality. Values near or just above 100 are considered unhealthy for sensitive groups, and values above 100 are considered unhealthy for everyone.

Air pollution is the presence of contaminants in the atmosphere, such as dust, fumes, gases, mist, odours, smoke, or vapours, which can be harmful to human health. These pollutants are primarily inhaled through the respiratory tract, leading to inflammation, oxidative stress, immunosuppression, and mutagenicity in cells throughout the body, impacting the lungs, heart, and brain, among other organs. Some air pollutants are small enough to penetrate the bloodstream through the lungs and circulate throughout the body, causing systemic inflammation and increasing the risk of cancer.

Short-term and long-term exposure to air pollution can lead to a range of health issues. Short-term exposure to high levels of particulate matter can cause reduced lung function, respiratory infections, and aggravated asthma. Long-term exposure to fine particulate matter increases the risk of stroke, heart disease, chronic obstructive pulmonary disease, and cancer. Additionally, air pollution has been linked to adverse pregnancy outcomes, including low birth weight and infant mortality, as well as diabetes, cognitive impairment, and neurological diseases.

Certain groups are more susceptible to the health risks of poor air quality, including children, pregnant women, older adults, and individuals with pre-existing heart and lung disease. People in low socioeconomic neighbourhoods may also be more vulnerable due to proximity to industrial pollution sources, underlying health issues, poor nutrition, and stress. It is important to note that the health impacts of air pollution can vary depending on the types and concentrations of pollutants, and the duration of exposure.

What is the AQI in my location?

The Air Quality Index (AQI) is a tool for reporting daily air quality. It tells you how clean or polluted the air is in your location and what associated health effects might be a concern. The AQI is measured on a scale from 0 to 500. The higher the AQI value, the greater the level of air pollution and the more serious the health concern. For example, an AQI value of 50 represents good air quality with little potential to affect public health, whereas an AQI value over 300 indicates hazardous air quality.

There are several ways to find the AQI in your location. One way is to use Google Maps. You can do this by searching for a location and then selecting a 'map layer' option, which will bring up a colour-coded map with an air quality index guide. You can then zoom in for more specific locations and exact readings.

Another way to find your local AQI is to use the AirData website, which gives you access to air quality data collected at outdoor monitors across the United States, Puerto Rico, and the U.S. Virgin Islands. The data comes primarily from the AQS (Air Quality System) database. You can download data into a file or view it on the screen, output the data into one of AirData’s standard reports, create graphical displays using one of the visualization tools, or investigate monitor locations using an interactive map.

Additionally, you can use the EPA's AIRNow website to find more information about the AQI in your location.

Frequently asked questions