At a glance
What matters most
- 01
US AQI and India’s National AQI both use a 0–500 format but apply different categories and pollutant breakpoints.
- 02
The European Air Quality Index reports six named bands rather than a US-style 0–500 headline number.
- 03
All three systems use the poorest or highest qualifying pollutant result to represent overall conditions.
- 04
A valid comparison starts with pollutant concentration, unit, averaging period, location and timestamp—not color alone.
The three systems at a glance
| Feature | US AQI | India National AQI | European index |
|---|---|---|---|
| Headline format | 0–500 index | 0–500 index | Six named bands |
| Categories | Good to Hazardous | Good to Severe | Good to Extremely Poor |
| Pollutant coverage | Ozone, PM2.5, PM10, CO, SO2 and NO2 calculations | PM10, PM2.5, NO2, SO2, CO, ozone, ammonia and lead | PM2.5, PM10, ozone, NO2 and SO2 |
| Overall result | Highest qualifying pollutant sub-index | Worst qualifying pollutant sub-index | Poorest available pollutant band |
| Primary purpose | Daily and current health communication | Daily public health communication | Hourly recent conditions and forecasts |
Why equal numbers do not mean equal pollution
US and Indian indexes may display the same number while representing different pollutant concentrations because their breakpoint tables and category boundaries differ. The European system does not use a directly comparable 0–500 headline value at all.
Even within one system, the pollutant driving the result matters. An AQI caused by ozone is calculated from a different concentration unit and averaging period than an AQI caused by PM2.5.
A safe comparison checklist
- Confirm the named index system before interpreting the number or color.
- Identify the pollutant driving the overall result.
- Compare underlying concentrations only when units and averaging periods match.
- Check whether the value is observed, forecast, modelled or provisional.
- Use the official national method for regulatory or public-authority reporting.
Which system AQI.news displays
AQI.news labels its headline city readings as US AQI and presents pollutant concentrations separately. This makes the scale explicit, but it does not turn the value into India’s National AQI or the European index.
When comparing AQI.news with CPCB, AirNow or the EEA, align the location and timestamp first, then compare pollutant concentrations and finally interpret each service’s own index.
Frequently asked questions
Can US AQI be converted directly to India AQI?
Not from the headline number alone. A defensible recalculation requires the underlying pollutant concentration, unit, averaging period and the target system’s breakpoint rules.
Is European AQI lower because it has no 0–500 number?
No. The presentation format is different. Its named bands are based on pollutant concentration thresholds and should be interpreted using the European methodology.
Do all systems use the same dominant pollutant?
Not always. Their pollutant lists, availability requirements and calculation rules differ, so the pollutant setting the overall result can vary.
Which AQI system is correct?
Each is correct within its defined purpose and methodology. The important step is to name the system and avoid comparing unlike numbers as if they were universal.
Primary sources
This reference was prepared from the following primary public-health and regulatory sources:
- 01Air Quality Index (AQI) BasicsUnited States Environmental Protection Agency
- 02Technical Assistance Document for the Reporting of Daily Air QualityUnited States Environmental Protection Agency
- 03National Air Quality IndexCentral Pollution Control Board, India
- 04European Air Quality IndexEuropean Environment Agency