SIOUX CITY, Iowa (KCAU) — For several days now, we’ve been talking about air qualities and something called an Air Quality Index, as Canadian wildfire smoke continues to create impacts across Siouxland. But what exactly is air quality and why is it so important?

Essentially, air quality is exactly what it sounds like, the quality of the air. And that’s where the Air Quality Index (AQI) comes in.

The Environmental Protection Agency (EPA), uses five major air pollutants, on a daily basis, to calculate the AQI. These pollutants: ground-level ozone; particle pollution; carbon monoxide; sulfur dioxide; and nitrogen dioxide, are all regulated by the Clean Air Act, which regulates sources of air emissions in an effort to both control and reduce US air pollution.

Most of the time, these pollutants are well managed and don’t cause much of an issue to the air quality. However, at certain times, one, or many of these pollutants, can increase in the atmosphere enough to reduce air quality.

However, each pollutant is created differently and increases for different reasons.

Ground-level Ozone is created when pollutants from a variety of sources, including cars, power plants, factories, and refineries are emitted into the air and have a chemical reaction with sunlight. As a result, ground-level ozone is most likely to reach unhealthy levels in urban areas on hot, sunny days.

Particle pollution is a mixture of solid particulate matter and and water droplets in the air. This type of pollution can be the result of direct emission from sources like construction sites, smokestacks, and fires. However, most particles form in the atmosphere from chemical reactions from factory, automobile, and other industrial emissions. Much like the past several days, this pollutant can reach unhealthy levels when fires are present or with wildfire smoke being advected into the area.

Carbon Monoxide, a colorless, odorless gas, which most, if not everyone, has heard of is released when something is burned. The largest source of carbon monoxide in the air is cars, trucks, and other vehicles/heavy machinery that burn fossil fuel such as gasoline or diesel. High levels of atmospheric carbon monoxide is, however, uncommon, but elevated levels can cause issues.

Sulfur dioxide is the fourth pollutant that the EPA takes into account when calculating Air Quality Index. Sulfur dioxide is largely produced and emitted into the atmosphere by the burning of fossil fuels, like industrial factories and power plants. It can also be produced by trains, ships, vehicles and other heavy equipment, or natural sources such as volcanoes. Sulfur dioxide can interact with other compounds within the atmosphere and contribute to particle pollution. This can cause issues with acid rain and haze in the atmosphere.

The fifth and final pollutant the EPA factors into the Air Quality Index is nitrogen dioxide, or NO2. This gaseous pollutant primarily finds its way into the atmosphere via emissions from automobiles like cars and buses, power plants, and off-road equipment. In high concentrations, NO2 can cause respiratory issues issues and/or irritate existing respiratory issues like asthma.

By combining the levels of these five pollutants in the air, the EPA assigns a value, ranging from 0 to 500, split into six different categories: 0-50; 51-100; 101-150; 151-200; 201-300; and 301 or higher. The higher the AQI, the greater the level of air pollution there is and the higher the health risk is as well.

These ranges then correspond to colors: green, yellow, orange, red, purple, and maroon, levels of concern, and descriptions of air quality and potential impacts a certain level may have.

This scale is then used to issue Air Quality alerts as needed. It is also used to inform the public of possible impacts to them.

An AQI below 100 is considered acceptable, however, in the moderate range, there may be issues for those who are unusually sensitive to pollution. Once AQI gets above 100 and into the slightly unhealthy to unhealthy range, that’s when we start to see more impacts. In the orange, slightly unhealthy category, the AQI may be unhealthy for sensitive groups such as those with respiratory issues like asthma, COPD, and other health issues.

Getting into the red/unhealthy level, some of the general public may experience some effects to health, like difficulty breathing with extended exposure/time outside. Those with more sensitivities (asthma, underlying health problems, etc.) are more likely to experience serious health issues in these air qualities. This is also the point when those within the sensitive category should avoid long or intense outdoor activity.

Once we get into the purple (201-300) range, it becomes very unhealthy to be outside for extended periods of time or to do an intense outdoor activities for everyone. This is when those within sensitive groups should avoid all outdoor activities and remain inside if possible.

Finally, on the fairly rare occasion when the AQI is 301 or higher, in the maroon (hazardous) range, this is when it becomes hazardous for everyone. It is recommended that everyone remains inside and avoids outdoor activities. And those in sensitive groups should limit their activity levels altogether.

For more information on AQI and air pollutants, visit: