Saint-Louis vs Thiès: PM2.5 compared

Over the last year, Saint-Louis's air was about 1.8× as polluted as Thiès's: PM2.5 averaged 15.4 µg/m³ against 8.6, on the 176 days both cities were measured. Saint-Louis had the dirtier air on 113 of those days, Thiès on 62. Saint-Louis was over the WHO's daily guideline of 15 µg/m³ on 41 of them, Thiès on 21.

Right now

Saint-Louis#651on the 24-hour board of 2,753, at 54 US AQI (10.5 µg/m³)

Thiès#375on the 24-hour board of 2,753, at 60 US AQI (13.8 µg/m³)

The last year, day by day

Saint-Louis

Thiès

Each city's daily mean from 9 Oct 2025 to 8 Oct 2026, one stripe a day, coloured by band. A blank stripe is a day without a daily mean.

Month by month

Monthly means in µg/m³ over the days both cities were measured. Solid: Saint-Louis. Faded: Thiès. A month shows once both share 10 such days. Dashed line: the WHO daily guideline, 15 µg/m³.

Each city's worst days

Saint-Louis

21 Sept 2026469309.7 µg/m³
17 Sept 2026314231.9 µg/m³
1 Oct 2026226151.2 µg/m³

Thiès

2 Apr 20269030.1 µg/m³
1 Apr 20268728.5 µg/m³
17 Sept 20268427.0 µg/m³

Daily means in US AQI, with µg/m³ beside them, since the index stops at its top value, over the days both cities were measured in the last year. Each date opens that day's world board.

Compare either city with another

Saint-Louis

Side by side with Ziguinchor (Senegal's worst on 30 days), Gujranwala (the world's worst on 30 days).

Thiès

Side by side with Dakar (the nearest), Ziguinchor (Senegal's worst on 30 days), Gujranwala (the world's worst on 30 days).

Use this page

SmogRank, PM2.5 daily means compared, Saint-Louis and Thiès, 9 Oct 2025 – 8 Oct 2026, smogrank.com/compare/sn-saint-louis/sn-thies (accessed 9 Oct 2026).

You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.

The same rules as every SmogRank figure: reference monitors first, and a day counts with 18 measured hours. How we measure.

Updated 2026-10-09 12:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index. Some readings: Uzhydromet (Uzbekistan's Hydrometeorological Service); Department of Environment, Nepal; Vietnam's government monitors; Aurassure; Umhverfisstofnun (Environment Agency of Iceland); Love My Air (City and County of Denver), no reuse terms published (why we use them).