Air quality index – an indispensable tool

Air quality index – an indispensable tool


By Edward Brotsky/Mesa County Health Department

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Air pollution comes in many forms, and keeping track of all of them can be a confusing task. Different types of pollution come from different sources, have different health effects, and each has its own thresholds for when health warnings are triggered. To sort through this mess, the Environmental Protection Agency (EPA) has developed an easy-to-use tool called the Air Quality Index.


The Air Quality Index, or AQI, is a multi-pollutant, round-number, color-coded scale. That’s a mouthful, so let’s explore each of those attributes in detail.

Multi-Pollutant: Five different types of air pollution are represented on the scale: ozone, particulates (including both fine and coarse), carbon monoxide, nitrogen dioxide and sulfur dioxide. Gaseous types of pollution, such as ozone and carbon monoxide are often measured in parts per million (or billion). Particulate pollution is reported as micrograms per cubic meter. Here’s the good news – if you want to know at a glance how good (or bad) the air quality is on any given day, none of that matters! For the index, all types of pollution are placed on the same measuring stick.

Round Numbers: Round numbers are easy to remember and interpret. For fine particulate pollution, the transition from good to moderate air quality occurs at 12 micrograms per cubic meter. For larger particulates, that mark is at 54 micrograms. When using the index, the good/moderate threshold is 50 for all types of pollution all the time. Each subsequent step up the index ladder is the same, with the transition from the moderate category to unhealthy for sensitive groups occurring at 100, the next category at 150, and so on.

Color Coded: Each of the health levels also has its own color. This allows the index to truly be a tool that can be used in a hurry. If the color is green, you’re good to go.

Next week, we’ll explore some resources that can help you to stay informed of current air quality conditions by using the Air Quality Index.

Ed Brotsky is the Air Quality Specialist for the Mesa County Health Department. Read him weekly on

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