The European Air Quality Index (EAQI) Explained
Across the European Union, the European Environment Agency publishes a common index so that air quality in Lisbon, Warsaw, and Helsinki can be read on the same scale. It isn't a number from 0 to 500 — it's a six-step category ladder, from Good to Extremely poor. After a 2023 revision the bands were tightened to line up with the World Health Organization's 2021 guidelines, making the EAQI one of the stricter consumer indices in the world. This guide explains how it works.
What the European AQI is
The EAQI rates air quality using hourly data for five pollutants: PM2.5, PM10, nitrogen dioxide (NO₂), ozone (O₃), and sulphur dioxide (SO₂). Each pollutant is placed in a category from its own concentration band, and the overall index for a location is the worst of the five — the same dominant-pollutant logic the US AQI uses. Where data is missing, the EEA fills gaps with modelled estimates downscaled from the Copernicus Atmosphere Monitoring Service (CAMS).
The six categories
| Category | Colour | In plain English |
|---|---|---|
| Good | Cyan | Air quality is good. Enjoy your usual outdoor activities. |
| Fair | Green | Acceptable. Unusually sensitive people should consider limiting prolonged heavy exertion outdoors. |
| Moderate | Yellow | Sensitive groups may experience symptoms; consider reducing strenuous outdoor activity. |
| Poor | Red | Sensitive groups should reduce outdoor exertion; the general public may begin to notice effects. |
| Very poor | Dark red | Health risk for everyone. Reduce outdoor physical activity. |
| Extremely poor | Purple | Serious health risk. Avoid outdoor physical activity. |
The per-pollutant breakpoints
These are the concentration bands (µg/m³) introduced in the EEA's WHO-aligned revision. The first two bands (Good and Fair) are anchored to the WHO 2021 long- and short-term guideline values; the higher bands were derived to give roughly equivalent health risk across pollutants.
| Category | PM2.5 | PM10 | NO₂ | O₃ | SO₂ |
|---|---|---|---|---|---|
| Good | 0–5 | 0–15 | 0–10 | 0–60 | 0–20 |
| Fair | 6–15 | 16–45 | 11–25 | 61–100 | 21–40 |
| Moderate | 16–50 | 46–120 | 26–60 | 101–120 | 41–125 |
| Poor | 51–90 | 121–195 | 61–100 | 121–160 | 126–190 |
| Very poor | 91–140 | 196–270 | 101–150 | 161–180 | 191–275 |
| Extremely poor | 141+ | 271+ | 151+ | 181+ | 276+ |
How the European AQI compares to the US AQI
The EAQI's "Good" band is notably stricter than the US "Good" — its PM2.5 ceiling is 5 µg/m³, matching the WHO annual guideline, while the US "Good" range runs to 9 µg/m³. As a rough categorical map:
- Good / Fair ≈ US AQI 0–50 (Good), with "Fair" reaching into the low Moderate range
- Moderate ≈ US AQI 51–100 (Moderate)
- Poor ≈ US AQI 101–150 (Unhealthy for Sensitive Groups)
- Very poor ≈ US AQI 151–200 (Unhealthy)
- Extremely poor ≈ US AQI 201+ (Very Unhealthy and worse)
Because the EAQI splits the lowest end into two bands and anchors them to WHO values, a reading that the US would call "Good" can show up as "Fair" or even "Moderate" in Europe. That isn't the air being worse — it's a stricter yardstick.
Index versus limit values
It's worth separating two things Europe publishes. The EAQI is a communication tool — a daily snapshot for the public. Separately, the EU sets legally binding limit values (the regulatory standards). In 2024 the EU adopted a revised Ambient Air Quality Directive that tightens those 2030 limit values toward WHO levels. The index and the limit values move in the same direction but are not the same thing.
Air quality on your home screen
Smog Report shows real-time air quality with widgets and Live Activities, and lets you switch between regional scales including the European AQI. Free on iOS.
Download for iOSPrimary sources: EEA — European Air Quality Index · EEA live index · WHO 2021 Air Quality Guidelines