Understanding the AQI

The purpose of the AQI is to help you understand what local air quality means to your health. To make it easier to understand, the AQI is divided into six categories:

Air Quality Index
(AQI) Values
Levels of Health Concern Colors
When the AQI is in this range: ..air quality conditions are: ...as symbolized by this color:
0 to 50 Good Green
51 to 100 Moderate Yellow
101 to 150 Unhealthy for Sensitive Groups Orange
151 to 200 Unhealthy Red
201 to 300 Very Unhealthy Purple
301 to 500 Hazardous Maroon

Note: Values above 500 are considered Beyond the AQI. Follow recommendations for the Hazardous category. Additional information on reducing exposure to extremely high levels of particle pollution is available here.

Each category corresponds to a different level of health concern. The six levels of health concern and what they mean are:

  • "Good" AQI is 0 to 50. Air quality is considered satisfactory, and air pollution poses little or no risk.

  • "Moderate" AQI is 51 to 100. Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people. For example, people who are unusually sensitive to ozone may experience respiratory symptoms.

  • "Unhealthy for Sensitive Groups" AQI is 101 to 150. Although general public is not likely to be affected at this AQI range, people with lung disease, older adults and children are at a greater risk from exposure to ozone, whereas persons with heart and lung disease, older adults and children are at greater risk from the presence of particles in the air.

  • "Unhealthy" AQI is 151 to 200. Everyone may begin to experience some adverse health effects, and members of the sensitive groups may experience more serious effects.

  • "Very Unhealthy" AQI is 201 to 300. This would trigger a health alert signifying that everyone may experience more serious health effects.

  • "Hazardous" AQI greater than 300. This would trigger a health warnings of emergency conditions. The entire population is more likely to be affected.

AQI colors

EPA has assigned a specific color to each AQI category to make it easier for people to understand quickly whether air pollution is reaching unhealthy levels in their communities. For example, the color orange means that conditions are "unhealthy for sensitive groups," while red means that conditions may be "unhealthy for everyone," and so on.

Air Quality Index Levels of Health Concern Numerical
Value
Meaning
Good 0 to 50 Air quality is considered satisfactory, and air pollution poses little or no risk.
Moderate 51 to 100 Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.
Unhealthy for Sensitive Groups 101 to 150 Members of sensitive groups may experience health effects. The general public is not likely to be affected.
Unhealthy 151 to 200 Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects.
Very Unhealthy 201 to 300 Health alert: everyone may experience more serious health effects.
Hazardous 301 to 500 Health warnings of emergency conditions. The entire population is more likely to be affected.
 

Myths

Let's clear a few things up

Myth:

Cyclists and pedestrians are exposed to more air pollution than drivers

Fact:

Wrong. As well as being better for your health and fitness, evidence shows that cyclists and pedestrians are also less exposed to air pollution than people in vehicles. This is because your air filter probably doesn’t remove pollution from the air it circulates and being on the road itself means that your vehicles is surrounded by exhaust fumes. Pedestrians and cyclists are also less exposed because even 1 metre away from traffic, there is considerably less pollution than on the road itself.

Myth:

Turning your engine on and off again whilst sat in traffic releases more emissions than leaving it running.

Fact:

Whether you’re stuck in traffic or just waiting to pick someone up, if you think that your car might be stationary for more than 2 minutes it’s better to turn your engine off than leave it running. Doing so will reduce the amount of gases harmful to our health and the environment that your car emits. It’s an easy way to reduce your own contribution to air pollution!

News

All the latest from Clean Air Leeds

We know we need to improve air quality in the city and are committed to doing our bit to make a difference.

What we are doing