To determine the quality of the air we breathe, there are a number of indicators that display specific numbers. We know these as the Air Quality Index (AQI). Unfortunately, not everyone understands the meaning of the numbers displayed there. These numbers are very important because they provide information related to health, daily activities, and vulnerable age groups. By understanding the air quality index meaning, we can know the right time to do activities outside and when we should reduce our exposure to outdoor air.
Contents
Understanding the AQI
The AQI is an index system to describe the level of air pollution in an area. The index numbers reflect daily air conditions based on the concentration of several major pollutants. A high AQI value indicates poor air quality, which has a greater impact on health.
The AQI index system aims to simplify complex scientific data so that everyone can easily understand it. By understanding the AQI, everyone can be more aware of things that have a negative impact on health. Many countries use the AQI to assess air pollution levels and their health risks. However, it is important to note that AQI calculation methods may vary slightly between countries. The US AQI, developed by the U.S. Environmental Protection Agency (EPA), is the most commonly referenced system and is widely used by global air quality platforms.
Key AQI Parameters
The AQI index is derived from a number of pollutants. It is calculated based on several key parameters that have the greatest impact on human health. One of the most important parameters is PM2.5. These particles are so small that they can enter the lungs and, in some cases, the bloodstream. Next is PM10. These particles are larger than PM2.5 and originate from road dust, construction activities, and industrial processes.
Another important parameter is O₃ (ground-level ozone). Ozone is produced by chemical reactions between other pollutants under sunlight. At high concentrations, ground-level ozone can irritate the respiratory system and reduce lung function, especially during outdoor activities.
Nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and carbon monoxide (CO) are also parameters in the AQI. These gases originate from exhaust fumes, power plants, and the burning of fossil fuels.
Each type of pollutant has a certain threshold limit, which is represented on the AQI scale. The daily AQI value comes from the pollutant with the highest concentration on that day. Even though it is only one type of pollutant, it is accurate enough to determine the overall air quality.
AQI Color Scale
The AQI uses a color scale. Green indicates high-quality air that is reasonably safe for people of all ages. This implies that there are no particular limitations on our ability to participate in outdoor activities. In numerical terms, green represents an AQI range of 0–50 and is classified as “Good.”
The color yellow denotes moderate air quality. These circumstances may have minor effects on some sensitive people. It is generally safe because most people don’t have any side effects. Yellow corresponds to an AQI range of 51–100 and is categorized as “Moderate.”
Orange indicates unhealthy air quality for vulnerable groups such as children, the elderly, and people with respiratory diseases. These groups should limit their outdoor activities. Orange represents an AQI range of 101–150 and is officially classified as “Unhealthy for Sensitive Groups.”
Red indicates unhealthy air quality for everyone and is very risky to health. This category covers an AQI range of 151–200 and is classified as “Unhealthy.”
The colors purple and maroon denote extremely hazardous and poor air quality. In these circumstances, we should limit our exposure to outdoor air and exclusively participate in inside activities. Purple represents an AQI range of 201–300 and is classified as “Very Unhealthy,” while maroon indicates AQI values above 300 and is classified as “Hazardous,” signaling emergency health conditions.
This color scale makes it simple for individuals to assess the quality of the air they breathe outside and reduce any harmful effects on their health.
| AQI Range | Color | Category | Health Meaning |
|---|---|---|---|
| 0–50 | Green | Good | Minimal or no health risk |
| 51–100 | Yellow | Moderate | Acceptable air quality; some risk for very sensitive individuals |
| 101–150 | Orange | Unhealthy for Sensitive Groups | Children, elderly, and people with respiratory or heart conditions should limit outdoor activity |
| 151–200 | Red | Unhealthy | Everyone may experience health effects |
| 201–300 | Purple | Very Unhealthy | Serious health effects; outdoor activities should be avoided |
| 301+ | Maroon | Hazardous | Emergency conditions; high risk for the entire population |
What Should You Do at Each AQI Level?
Understanding the Air Quality Index is truly beneficial when it helps guide your daily decisions. Check the table below for the recommended actions based on the index level.
| AQI Level | Recommended Actions |
|---|---|
| Good (0–50) | Safe for outdoor activities |
| Moderate (51–100) | Sensitive individuals should monitor symptoms |
| Unhealthy for Sensitive Groups (101–150) | Reduce prolonged outdoor exertion |
| Unhealthy (151–200) | Limit outdoor activities; wear masks if necessary |
| Very Unhealthy (201–300) | Avoid outdoor activities; stay indoors |
| Hazardous (301+) | Remain indoors with air filtration if possible |
“If the AQI is already moderate and especially when it turns unhealthy, I usually stay indoors more and run an air purifier. It’s a simple way to reduce PM2.5 exposure, particularly for kids, older adults, and anyone with breathing issues.”
— Maggie Shen, Founder of Legom
The Impact of Poor AQI on Health
Poor air quality is very dangerous to health. Short-term exposure can potentially cause irritation to the nose, eyes, and throat. In some people, it can cause coughing, shortness of breath, and headaches after they have been outdoors.
For long-term exposure, very small particles such as PM2.5 can enter the lungs and bloodstream. This can potentially increase the risk of heart disease, chronic lung disorders, and stroke. Long-term exposure to polluted air has also been linked to reduced lung function and increased hospital admissions, according to environmental health studies. In children, continuous exposure to air pollution can potentially cause lung development disorders.
For vulnerable groups such as people with asthma, heart disease, and the elderly, even a slight increase in the AQI can trigger serious symptoms. Understanding the AQI well can help us determine the steps we need to take to minimize risk.
How to Check the AQI
To check the AQI, we can use the weather app on our cell phones. We can also utilize the official government website or environmental agencies. They usually display the daily AQI. In fact, some platforms provide automatic notifications when the AQI reaches a certain level. Many of these platforms follow guidelines and standards from environmental authorities such as the EPA or the World Health Organization (WHO).
Currently, several major cities have installed air quality information boards. This is very helpful in raising public awareness so that they can plan their daily activities safely.
The Importance of Understanding AQI
In this era of industrialization and urbanization, air quality has become a challenge for a number of cities. AQI plays an important role in helping the public make daily decisions. Without a proper understanding, the AQI index only displays meaningless statistical numbers.
Public awareness of the meaning of the air quality index will help them adjust their lifestyles. When is the best time to exercise outdoors, when to wear a mask, or when to limit outdoor activities. Understanding AQI levels also helps individuals make decisions during pollution events such as wildfires, traffic congestion, or industrial emissions.
For policy makers, the AQI is a tool for evaluating and designing air pollution control plans. As a result, the AQI is not just a number on a cell phone screen, but an indicator of the quality of the air we breathe every day.
Understanding the AQI is crucial because it can illustrate the correlation between environmental conditions and health. Thus, we can minimize risks and improve our quality of life. Checking the AQI regularly should become a daily habit, especially for those of us who live in urban and industrial areas, or who have vulnerable family members.
So, it’s time to monitor air quality regularly before engaging in outdoor activities. Don’t forget to share this information with your loved ones to foster their awareness and concern. A good understanding of the air quality index meaning is the foundation for living healthier lives amid the growing challenge of air pollution.