South Coast AQMD Develops Modified Air Quality Index, Improving Accessibility for People with Color Vision Deficiencies

South Coast AQMD’s Air Quality Sensor Performance Evaluation Center (AQ-SPEC) and Air Quality Assessment Group have led the development of a modified version of the Air Quality Index (AQI) that will provide better accessibility for those with color vision deficiencies. The changes were primarily made to the hues, keeping the essential colors associated with each AQI category and health impacts (green, yellow, orange, red, purple, maroon). The original color scale can be difficult to discern for those individuals who have challenges distinguishing certain colors, especially red and green colors.

Colors on the AQI should be as accessible as possible because they are associated with important recommendations to help the public minimize their exposure to poor air quality. The modified color scale will accommodate individuals with some form of color impairment while still being similar enough to the traditional AQI color scale that has been used for decades and is familiar to the public. The modified scale was tested against eight common types of color impairment using a simulator to ensure the categories would be distinguishable. Another key feature is that the new scale moves from the lightest color (green) to the darkest color (maroon) so that it can be interpreted when converted to grayscale.

The new color scale also works as a continuous gradient, which will improve AQI animations and visualizations from air pollution events such as smoke from a wildfire. Currently the modified AQI is being piloted on several applications including the U.S. Environmental Protection Agency’s (U.S. EPA) Fire and Smoke map at as well as South Coast AQMD’s real-time air quality map available on our mobile app and at

This work was conducted in collaboration with the Desert Research Institute, and in coordination with the U.S. Forest Service, and the U.S. EPA. 
AQI Color Table

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