Air quality in Leiden, South Holland, Netherlands today
Mr. Duck’s Air Quality Score
Unhealthy for sensitive groups for Leiden, South Holland, Netherlands
This friendly indicator summarizes the latest city readings. For health guidance, please see: EPA AirNow or WHO.
Air quality today
The air quality in Leiden today falls into the USG category. The primary pollutant identified is PM2.5, with a measured concentration of 39.72 µg/m³ based on five valid observations reported through OpenAQ.
No other pollutants are highlighted for this assessment, and the data reflect the current monitoring snapshot. This page is informational; for health guidance, use official sources such as EPA AirNow or WHO.
Latest sensor values
PM categories follow US EPA AQI breakpoints, shown here as an estimate derived from the latest valid measurements (this project does not compute EPA NowCast/24-hour AQI yet).
What the data includes
The dataset for Leiden pulls information from a single monitoring location – the Stevenshof site – and contains six separate records, one for each pollutant measured there. The pollutants available are PM1, PM10, PM2.5, relative humidity, temperature and particle count (UM003). For the three particulate matter metrics the values are all identical across the record set: PM1 registers at 22.93 µg/m³, PM10 at 69.20 µg/m³ and PM2.5 at 39.72 µg/m³. Relative humidity is reported as 68.05 %, temperature as 12.15 °C and the particle concentration (UM003) as 4 462.52 particles per cm³.
Freshness of the data varies by pollutant. The most recent updates for PM1, PM2.5, relative humidity, temperature and UM003 were recorded on 2026‑02‑10 at 22:00 UTC, meaning those measurements are less than a week old. In contrast, the PM10 reading is older, last updated on 2025‑01‑13 at 23:00 UTC, which places it over a year behind the other parameters. Because all six records come from the same station, there is no spatial spread across Leiden; conditions can differ in other neighbourhoods or micro‑environments that this single point does not capture.
Overall the data set offers a complete snapshot of several key air quality variables at one location, with most values being current while the PM10 figure remains dated. Users should keep in mind that the limited station coverage means the figures represent conditions at Stevenshof specifically and may not reflect city‑wide variations at any given moment.
Learn more about sources and filtering: About the data.
Trusted references: WHO (Air pollution) · US EPA AirNow · European Environment Agency (Air)
Latest sensor values (bars)
PM categories follow US EPA AQI breakpoints, shown here as an estimate derived from the latest valid measurements (this project does not compute EPA NowCast/24-hour AQI yet).
Data notes
The data shown are based on five valid measurements and were refreshed recently, with the latest update recorded on 2026‑02‑10 at 22:00 UTC; the dataset is considered “Updated within 3 days.” This snapshot reflects conditions measured at specific monitoring points and times, so air quality can differ across neighborhoods and moments throughout Leiden.
OpenAQ station rows
| Station | Parameter | Value | Unit | Last updated |
|---|---|---|---|---|
| Leiden - Stevenshof | pm1 | 22.930059523809522 | µg/m³ | 2026-02-10 22:00 UTC |
| Leiden - Stevenshof | pm10 | 69.19642861684163 | µg/m³ | 2025-01-13 23:00 UTC |
| Leiden - Stevenshof | pm25 | 39.720238095238095 | µg/m³ | 2026-02-10 22:00 UTC |
| Leiden - Stevenshof | relativehumidity | 68.05470236142476 | % | 2026-02-10 22:00 UTC |
| Leiden - Stevenshof | temperature | 12.147440390927452 | c | 2026-02-10 22:00 UTC |
| Leiden - Stevenshof | um003 | 4462.516369047619 | particles/cm³ | 2026-02-10 22:00 UTC |