Air quality in Santiago do Cacém

MODELLED — averaged over the 1,065 one-kilometre cells inside Santiago do Cacém for 2024, weighted by the 27,888 people who live in them, so a large empty concelho is scored by its town rather than by its moorland. Weighted by land area instead it would be 33/100. An address inside it can still sit well above or below this figure, which is what the address lookup is for.

Modelled annual values, 2024

MODELLED — EEA / ETC-HE 1 km European air quality maps. The first column is the population-weighted mean, what a resident typically breathes. The range shows the cleanest and dirtiest cell anywhere inside the boundary, which is usually the more useful number: it is the spread a buyer is choosing between. Ozone is the 93.2nd percentile of the daily maximum 8-hour mean, not an annual mean.

Fine particles under 2.5 micrometres (PM2.5), modelled, four years

Nitrogen dioxide (NO₂), modelled, four years

MODELLED — the area mean in each year's map. Four years is not a trend. Weather moves these numbers between years by more than most policy does, and the 2021 and 2022 maps were produced with a different input mix from the 2023 and 2024 ones.

What the monitors near Santiago do Cacém have measured

These are real measurements from the nearest official monitoring stations. A station a few kilometres away can differ a lot from a specific street, especially for nitrogen dioxide, which falls off sharply away from traffic.

Fine particles under 2.5 micrometres (PM2.5)

Not plotted: Monte Chãos 2026 — the year is not over — 23% of its hours so far, not yet a comparable annual mean; Santiago do Cacém 2026 — the year is not over — 65% of its hours so far, not yet a comparable annual mean; Sonega 2026 — the year is not over — 68% of its hours so far, not yet a comparable annual mean; Monte Chãos 2025 — only 71% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown; Santiago do Cacém 2024 — only 73% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown; Sonega 2024 — only 42% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown; and 5 more.

Coarse particles under 10 micrometres (PM10)

Not plotted: Monte Chãos 2026 — the year is not over — 11% of its hours so far, not yet a comparable annual mean; Santiago do Cacém 2026 — the year is not over — 59% of its hours so far, not yet a comparable annual mean; Sonega 2026 — the year is not over — 66% of its hours so far, not yet a comparable annual mean; Santiago do Cacém 2025 — only 59% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown; Monte Chãos 2023 — only 53% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown; Santiago do Cacém 2023 — only 47% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown; and 4 more.

Nitrogen dioxide (NO₂)

Not plotted: Monte Chãos 2026 — the year is not over — 60% of its hours so far, not yet a comparable annual mean; Santiago do Cacém 2026 — the year is not over — 28% of its hours so far, not yet a comparable annual mean; Sonega 2026 — the year is not over — 51% of its hours so far, not yet a comparable annual mean; Monte Chãos 2016 — only 74% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown; Santiago do Cacém 2016 — only 21% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown.

Ozone (O₃)

Not plotted: Monte Chãos 2026 — the year is not over — 55% of its hours so far, not yet a comparable annual mean; Santiago do Cacém 2026 — the year is not over — 21% of its hours so far, not yet a comparable annual mean; Sonega 2026 — the year is not over — 43% of its hours so far, not yet a comparable annual mean; Monte Chãos 2025 — only 67% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown; Sonega 2024 — only 55% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown; Santiago do Cacém 2018 — only 46% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown.

This is the annual mean of the hourly ozone measurements. The EU target value of 120 µg/m³ is written against a different statistic — the daily maximum 8-hour mean — so it is not drawn here. Ozone behaves unlike the others: it is destroyed by fresh traffic exhaust, so a busy street often reads lower than the countryside around it.

The stations these come from

A traffic station sits beside a busy road and reads the worst case; a background station reads what the area as a whole breathes; an industrial one sits near a plant. Which kind you are looking at matters more than the distance.

MEASURED — hourly observations reported by Portugal to the European Environment Agency, aggregated here into annual means. A year is charted only if at least 75% of its hours are valid, the threshold the EU sets for an annual mean, and only if the value is physically plausible; anything excluded is listed under its chart with the reason rather than dropped. Station names and locations come from APA's QualAr register; station type and setting from the EEA's station metadata. Verified data through 2025; the most recent year is provisional and not yet verified.

How it changes through the year

PM2.5 peaks in March at 5.9 µg/m³ and bottoms out in November at 3.4, a factor of 1.7. PM10 peaks in March at 26.0 µg/m³ and bottoms out in January at 11.9, a factor of 2.2. NO₂ peaks in September at 2.4 µg/m³ and bottoms out in March at 1.6, a factor of 1.4. O₃ peaks in May at 84.1 µg/m³ and bottoms out in December at 64.3.

MEASURED — Santiago do Cacém (industrial, 13 km away), each calendar month averaged over 2022 onwards, µg/m³. A month is used only if at least 400 of its hours are valid.

Particles run highest in the cold months, when domestic wood burning coincides with still air that does not disperse it. An annual mean hides that entirely. Ozone runs highest in summer, because sunlight is what makes it. It is also the one pollutant a busy street has less of than the countryside around it, since fresh traffic exhaust destroys it.

What is near this address

Traffic

• We could not find a motorway, trunk road or primary road near enough to measure.

Distance measured from this location to the nearest road tagged as a motorway, trunk or primary road in OpenStreetMap. © OpenStreetMap contributors, ODbL. Nitrogen dioxide from traffic falls off within a few hundred metres of a busy road.

Industry within 10 km

• Azinheirinha (CI)
  Intensive livestock production and aquaculture · Santiago do Cacém
  NH3 42 t/yr

  5.7 km
  north
• Almagêde (CI)
  Intensive livestock production and aquaculture · Santiago do Cacém
  NH3 24 t/yr

  10.0 km
  north-east

REPORTED BY THE OPERATOR — European Industrial Emissions Portal (European Environment Agency), reporting year 2024, air releases in tonnes per year as the operator declared them. Ranked by the total of the pollutants that affect local air; carbon dioxide is deliberately excluded because it is a climate pollutant and would otherwise dominate the ranking. A facility being listed is not a statement that it affects this address.

Known projects nearby

This is a hand-curated list with sources, not a forecast and not a model. We have not estimated how much any of these would change the air. The list is small and certainly incomplete: it holds 15 entries for the whole country. Anything genuinely local — a quarry, a new estate road, a planning application — will not be here, and a buyer should still ask the council.

• Central Termoelétrica de Sines (carvão) — encerrada
  power · closed · likely effect on air: better

  18 km
  west

  The coal-fired power station at Sines stopped burning coal in January 2021, removing what had been one of the country's largest single sources of combustion emissions from this stretch of the Alentejo coast.

  ECO — «35 anos depois, EDP abandona carvão em Sines» (14 de janeiro de 2021) · checked 2026-09-21

Nearby councils in Alentejo Litoral

MODELLED — same 1 km maps, same year, area means.

Sources and what they cannot tell you

• Measured history — European Environment Agency Air Quality Download Service: 19,038,066 validated hourly observations from Portugal's 71 stations, 2013–2026. Station names from APA QualAr. A station is not your street. Nitrogen dioxide in particular varies by hundreds of per cent over a few hundred metres.
• Modelled values at the address — the EEA / ETC-HE 1 km European air quality maps, 2024 and the three years before it. A 1 km cell is an average over a square kilometre. It cannot see one side of a street being busier than the other, and it will understate a very local source and overstate a very local clean spot.
• Industry — European Industrial Emissions Portal, reporting year 2024, as declared by operators. Only installations above the European reporting thresholds appear. Emissions reported are annual totals: they say nothing about when, or which way the wind was blowing.
• Roads — OpenStreetMap, © OpenStreetMap contributors (ODbL). Distance to a road class, not to traffic. A quiet primary road and a jammed one look identical here.
• Boundaries — CAOP (Carta Administrativa Oficial de Portugal, DGT), all 308 concelhos and the freguesias of the Lisbon and Porto metropolitan areas.
• Known projects — curated by hand, each with a citation. Not a forecast. Incomplete by construction.
• Address lookup — OpenStreetMap Nominatim. A geocoder returns the coordinate it thinks you meant. Check the place name we echo back before trusting the figures.
• Not used — CAMS reanalysis, which would give hourly modelled history, needs a Copernicus Atmosphere Data Store key that this build does not have. Madeira and the Azores fall outside the 1 km European map domain, so those 30 municipalities have measured station data but no modelled values and no rating.

Data built 2026-09-21. airhome is free and has no commercial relationship with anyone selling property.