Which pollutants are typically included in calculating the Air Quality Index (AQI) in the United States?

• A. CO and SO2.
• B. PM2.5 and O3.
• C. Lead and ammonia.
• D. PM10 and NO2.

Answer: (B)

The AQI is built from separate sub-indices for several pollutants, and the overall number printed for a given day is the highest of those sub-indices. In the United States, the pollutants that are tracked for this index include ground-level ozone (O3) and fine particulate matter (PM2.5) because they frequently reach concentrations that pose the greatest health risks and vary a lot from place to place and day to day. While other pollutants like PM10, carbon monoxide, sulfur dioxide, and nitrogen dioxide also have their own sub-indices, the two that most commonly dominate the daily AQI are PM2.5 and O3. Lead and ammonia are not part of the standard US AQI. So PM2.5 and O3 are the pair most representative of what drives the AQI calculations.