Air Quality Index: Six Levels Of Breathing

Air quality is a critical determinant of human health and well-being. As cities and industries expand, so does their waste, which can leak into the air as pollutants. To monitor this, scientists and environmentalists have categorized air quality into six levels, each indicating a range of the Air Quality Index (AQI). The AQI is a yardstick that runs from 0 to 500, with higher values denoting greater pollution and health risks. These levels help communicate variations in air quality due to differences in pollution sources, atmospheric conditions, weather, and human activity. While countries may have distinct ways of measuring pollutants, the goal remains the same: to ensure clean and safe air for all living beings.

Air Quality Index (AQI)

The Air Quality Index (AQI) is a system used to warn the public when air pollution is dangerous. It is a yardstick that runs from 0 to 500, with the higher the AQI value, the greater the level of air pollution and the greater the health concern. The AQI tracks ground-level ozone (smog) and particle pollution (tiny particles from smoke, power plants, factories, vehicle exhaust, and other sources), as well as four other widespread air pollutants.

The AQI is based on the five "criteria" pollutants regulated under the Clean Air Act: ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide. The United States Environmental Protection Agency (EPA) has developed an AQI that is divided into six categories indicating increasing levels of health concern. Each category accounts for a level of concern in air quality and has assigned values that range between 0 and 500, with the latter being the highest and most dangerous. The six quality indicators are sorted as follows:

• Green (Good): AQI value is 0-50. Pollution is low and poses little or no risk.
• Yellow (Moderate): AQI value is 51-100. Air quality is acceptable. Some may be affected, particularly those with pre-existing lung diseases.
• Orange (Unhealthy for sensitive groups): AQI value is 101-150. Sensitive groups (such as the elderly, children, or people with lung conditions) may experience some health issues, and the general public is less likely to be affected.
• Red (Unhealthy): AQI value is 151-200. Everyone may start to experience health effects; those in sensitive groups may experience more serious health effects.
• Purple (Very Unhealthy): AQI value is 201-300. Health warnings of emergency conditions are possible. The entire population is more likely to be affected.
• Maroon (Hazardous): AQI value is 301+. Health emergency level. Everyone is likely to experience health issues.

Air pollution

The AQI is calculated based on the concentrations of these pollutants, with the overall index defined as the maximum value. The higher the AQI value, the greater the level of air pollution and the more serious the health concerns. The AQI typically ranges from 0 to 500 and is divided into six colour-coded groups, although some countries have their own set of AQI standards. The six quality indicators are:

• Good (Green): AQI value of 0-50. Pollution is low and poses little to no risk.
• Moderate (Yellow): AQI value of 51-100. Air quality is acceptable, but some unusually sensitive individuals may be affected.
• Unhealthy for Sensitive Groups (Orange): AQI value of 101-150. Sensitive groups such as the elderly, children, or those with respiratory or cardiac problems may experience health issues, but the general public is unlikely to be affected.
• Poor: AQI value of 151-200.
• Very Poor: AQI value of 201-300.
• Hazardous (Maroon): AQI value of 301+. A health emergency where everyone is likely to experience health issues.

It is important to keep track of the current air quality information in your area to take the necessary precautions to protect yourself and your loved ones from the harmful effects of air pollution.

Health concerns

The Air Quality Index (AQI) 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 100 generally corresponds to the National Ambient Air Quality Standards (NAAQS) for the pollutant. This level is short-term exposure for the public for each pollutant. Each level of air quality represents a range on the AQI and is associated with a different set of potential health impacts.

An AQI value of 50 or below represents good air quality, with little to no risk to health. At this level, individuals can freely engage in outdoor activities without concern for air quality. However, as the AQI value increases, so does the risk to health. An AQI between 51 and 100 is deemed moderate. While the air quality at this level is generally acceptable, certain pollutants may present a moderate health concern for a small number of people who are unusually sensitive to air pollution, such as those with respiratory conditions. They may experience symptoms such as coughing or shortness of breath.

When the AQI value ascends to between 101 and 150, it becomes unhealthy for sensitive groups. Sensitive individuals, including children, the elderly, and those with underlying health conditions, may start to experience health issues. As the AQI continues to rise above 150, the air quality becomes unhealthy for the general public, and the risk of health harm increases. At this level, everyone may start to experience adverse health effects, ranging from eye irritation and coughing to more serious concerns such as aggravated heart and lung diseases.

At an AQI level of 201-300, the air quality is considered very unhealthy, and health warnings of emergency conditions come into effect. Everyone is at risk of experiencing health effects, and sensitive groups are advised to limit prolonged outdoor exertion. The final level, hazardous, is indicated by an AQI value of 300 or higher. At this level, health emergency conditions are in effect, and everyone is likely to experience health issues.

Poor air quality can cause a range of health problems, from minor irritations to serious conditions. Fine particulate matter (PM2.5) can penetrate the lungs and enter the bloodstream, affecting all major organs. Exposure to PM2.5 can lead to diseases of the cardiovascular and respiratory systems, including stroke, lung cancer, and chronic obstructive pulmonary disease (COPD). Additionally, research has linked prenatal exposure to high levels of air pollution to developmental delays and psychological and behavioural problems in children. According to the World Health Organization (WHO), air pollution is the greatest environmental threat to health, causing 7 million premature deaths annually due to outdoor and household air pollution.

Colour-coded groups

The Air Quality Index (AQI) is a system used to warn the public about dangerous levels of air pollution. The AQI tracks six major air pollutants: ground-level ozone (smog), particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide. These pollutants are known to cause a range of health issues, from minor irritations such as coughing and eye irritation to more serious conditions, including heart disease and lung cancer.

The AQI is divided into six colour-coded groups, each indicating a level of concern and assigned a value ranging from 0 to 500, with higher values indicating greater pollution and health risks. The six colour-coded groups are as follows:

Green (Good): AQI value of 0-50. Pollution levels are low and pose little to no risk to the public. At this level, the air is clean and fresh, and individuals can safely participate in outdoor activities without worrying about adverse health effects.

Yellow (Moderate): AQI value of 51-100. Air quality is generally acceptable, but certain pollutants may present a moderate health concern for those with pre-existing respiratory conditions or unusual sensitivity to air pollution. This level typically signifies normal urban air quality, where common pollutants are present but not at harmful concentrations.

Orange (Unhealthy for Sensitive Groups): AQI value of 101-150. At this level, sensitive individuals, including children, the elderly, and those with underlying health conditions, may experience health issues. The general public is less likely to be affected.

Red (Unhealthy): AQI value of 151-200. This level is likely to be unhealthy for all members of the public, with potential short-term health effects for sensitive groups and irritation for the general population.

Purple (Very Unhealthy): AQI value of 201-300. At this level, health alerts are triggered, and everyone may experience more severe health effects. It is recommended to avoid outdoor activities and stay indoors as much as possible.

Maroon (Hazardous): AQI value of 301 and above. This level is considered a health emergency, with a high likelihood of widespread health issues. Everyone is at risk of experiencing serious health consequences.

It is important to note that these colour-coded groups may vary slightly depending on the specific standards and pollutants monitored in different countries or regions.

National Ambient Air Quality Standards (NAAQS)

The National Ambient Air Quality Standards (NAAQS) are air quality standards set by the US Environmental Protection Agency (EPA). The Clean Air Act Amendments of 1970 mandate the EPA to establish these standards to protect public health and the environment. The NAAQS define the maximum amount of a pollutant averaged over a specified period that can be present in outdoor air without harming public health.

The NAAQS are set for six principal pollutants or "criteria pollutants" that are common in outdoor air and considered harmful to public health and the environment. These six pollutants are particulate matter, ozone, nitrogen oxides, sulfur oxides, carbon monoxide, and lead. The Clean Air Act identifies two types of NAAQS: primary and secondary standards.

Primary standards are national ambient air quality standards designed to protect public health, including sensitive populations such as asthmatics, children, and the elderly. These standards aim to ensure an adequate margin of safety for individuals who may be more susceptible to the harmful effects of air pollution. Secondary standards, on the other hand, focus on protecting public welfare. They aim to safeguard against adverse effects on soils, water, crops, vegetation, man-made materials, animals, wildlife, weather, visibility, and climate. Additionally, secondary standards address damage to property, transportation hazards, economic values, and personal comfort and well-being.

The NAAQS are selected by the U.S. EPA Administrator through a comprehensive process that takes about five years. It involves reviewing relevant scientific literature, performing risk and exposure assessments, and integrating findings into a policy context. The EPA also provides year-round NAAQS forecasts, including maps that show how pollution levels change and move throughout the day. This real-time information helps individuals take necessary precautions to protect their health and plan their activities accordingly.

Frequently asked questions