The EPA defines Indoor Air Quality (IAQ) as "the air quality within and around buildings and structures, especially as it relates to the health and comfort of building occupants. Understanding and controlling common pollutants indoors can help reduce your risk of indoor health concerns."
IAQ can easily be confused with air pollution; both refer to something similar.
Air pollution is defined by the WHO as "contamination of the indoor or outdoor environment by any chemical, physical or biological agent that modifies the natural characteristics of the atmosphere."
In the context of biosecurity, indoor air quality often refers more specifically to airborne pathogens in indoor environments. Therefore, it can be useful to use the term IAQ when discussing disease transmission risk and air pollution when talking about, e.g., outdoor smog.