Air quality in Castêlo da Maia, Maia

MODELLED — averaged over the 21 one-kilometre cells inside Castêlo da Maia for 2024, weighted by the 21,248 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 3/100. 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 Castêlo da Maia 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.

Coarse particles under 10 micrometres (PM10)

Not plotted: D.Manuel II-Vermoim 2026 — the year is not over — 66% of its hours so far, not yet a comparable annual mean; Leça do Balio-Matosinhos 2026 — the year is not over — 22% of its hours so far, not yet a comparable annual mean; VNTelha-Maia 2026 — the year is not over — 24% of its hours so far, not yet a comparable annual mean; Leça do Balio-Matosinhos 2025 — only 56% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown; VNTelha-Maia 2024 — only 75% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown; Leça do Balio-Matosinhos 2023 — only 51% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown; and 10 more.

Nitrogen dioxide (NO₂)

Not plotted: D.Manuel II-Vermoim 2026 — the year is not over — 71% of its hours so far, not yet a comparable annual mean; VNTelha-Maia 2026 — the year is not over — 72% of its hours so far, not yet a comparable annual mean; VNTelha-Maia 2023 — only 52% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown; D.Manuel II-Vermoim 2022 — only 72% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown; VNTelha-Maia 2020 — only 61% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown; D.Manuel II-Vermoim 2017 — only 44% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown; and 1 more.

Ozone (O₃)

Not plotted: Leça do Balio-Matosinhos 2026 — the year is not over — 64% of its hours so far, not yet a comparable annual mean; VNTelha-Maia 2026 — the year is not over — 67% of its hours so far, not yet a comparable annual mean; VNTelha-Maia 2021 — only 43% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown; Leça do Balio-Matosinhos 2020 — only 32% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown; VNTelha-Maia 2019 — only 61% of the year's hours were valid, under the 75% the EU requires for an annual mean; treated as unknown; Custóias-Matosinhos 2016 — only 27% 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 January at 11.8 µg/m³ and bottoms out in August at 4.2, a factor of 2.8. PM10 peaks in February at 27.4 µg/m³ and bottoms out in September at 19.6, a factor of 1.4. NO₂ peaks in December at 20.3 µg/m³ and bottoms out in June at 9.5, a factor of 2.1. O₃ peaks in April at 64.9 µg/m³ and bottoms out in October at 39.3, a factor of 1.7.

MEASURED — Sobreiras-Lordelo do Ouro (background, 14 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

• Central de Valorização Energética e Confinamento Técnico (CI)
  Waste and waste water management · Maia
  NOX 289 t/yr · NH3 13 t/yr

  5.2 km
  south-west
• Monteiro Ribas - Embalagens Flexíveis, S.A. (CI)
  Other activities · Porto
  NMVOC 181 t/yr

  9.5 km
  south
• SPA - Sociedade de Produtos Avícolas, S.A. (CI)
  Intensive livestock production and aquaculture · Trofa
  NH3 51 t/yr

  5.7 km
  north-east

2 further facilities within 10 km are on the European register but declared no release of the pollutants that affect local air — only greenhouse gases, or nothing above the threshold.

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.

• Refinaria de Matosinhos / Leça da Palmeira (Galp) — encerrada
  industry · closed · likely effect on air: better

  9.8 km
  south-west

  Refining at Leça da Palmeira was discontinued in 2021 and the site is now a brownfield, removing a large permanent industrial emission source from the Matosinhos and Leça da Palmeira waterfront.

  Governo de Portugal — comunicado «Refinaria de Leça da Palmeira» · checked 2026-09-21

• Metro do Porto — Linha Rosa (São Bento–Casa da Música)
  rail · under construction · likely effect on air: better

  14 km
  south

  A new underground line through central Porto adds four stations and is expected to move trips off the road, which should ease traffic emissions in the city centre.

  Metro do Porto — Linha Rosa (página oficial do projeto) · checked 2026-09-21

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.