AQI (Authority) | FACTORS | APPROACH |
Coeff. of Haze (US) | SO2 and PM (smoke shade) | Weighted sum of two pollutants |
Oak Ridge AQI | SO2, NO2, PM, CO, photochemical oxidants | Weighted (ratio of observed pollutant to standard) combination of 5 pollutants |
Taiwan AQI | Statistical factor analysis approach for AQI. Authors compared the air quality index based on factor analysis method and Pindex method. The ratings (or trends) obtained by both these methods are exactly same, but the AQI based on factor analysis shows a wider range—indicates it’s the superior approach | |
USEPA’S Pollution Standard Index (1999) | SO2, NO2, PM, CO, O3 | Highest concentration of any ONE pollutant from group compared to its standard. Doesn’t consider synergistic effects of pollutants. Reported as separate indices specific to each pollutant |
API, Canada (pre-2007) |
| Range from very good (0) to very poor (100), with 50 as the threshold |
Air Quality Health Index (AQHI), Canada | O3, NO2, PM2.5 | Sum of excess mortality risk from pollutants. Calculated hourly based on 3-hr rolling average |
Ministry of Environment, Forestry & Climate Change, India | CO, NO2, PM10, PM2.5, SO2, O3, NH3 | Revamped AQI to incorporate pollutants monitoring in real time. The proposed API to adopt the HIGHEST sub-index (specific pollutant concentration is related to “breakout values” obtained by comparison of pollutant concentration and revised AQ regulatory standards and/or any corroborated dose-response relationship reported in the literature) |
API in China | SO2, NO2, PM10 | Uses HIGEST pollutant sub-index with “breakout” values. 3 tiers of regulatory AQ standards |
| SO2, NO2, PM10 | Compilation of equally weighted variables normalised to target values (from EU guidelines for compliance in 2022) |