Complex sentence: The PSI is reported as a number on a scale of 0 to 500 and is the air quality indicator and these index figures enable the public to determine whether air pollution levels in a particular location are good, moderate, unhealthful, or worse.
Split into simpler sentences: The PSI is reported as a number on a scale of 0 to 500 and is the air quality indicator. These index figures enable the public to determine whether the air pollution levels in a particular location are good, unhealthy, hazardous or worse.