Modelled fine-particle pollution (PM2.5) over central Santiago averaged 68.7 µg/m³ for 26 September 2026 — 4.6 times the World Health Organization's 24-hour guideline of 15 µg/m³. Every one of the previous 7 full days was also above that line, averaging 45.9 µg/m³ with a worst day of 80.7 µg/m³. A later check on 27 September still showed 39.2 µg/m³, so this is a sustained episode rather than a one-day spike. Particles this small travel deep into the lungs.
What this is not: these figures come from the Copernicus CAMS global model at roughly 40 km resolution, not from a street-level monitor. The model smooths city hotspots and can misplace smoke or dust plumes, so the exact value over any neighbourhood may differ. Only PM2.5 is judged here — ozone, nitrogen dioxide and indoor air are not. The WHO figure is a health guideline, not a legal limit, and this record says a change was seen, not what caused it. Spring in the Santiago basin, under El Niño conditions, often traps air.
Ground monitor data from the city network, a CAMS revision, or daily means falling back below 15 µg/m³ would change the picture.
Written by AI, then checked by a separate reviewer before publication. Every claim points at the evidence below.