How bad is London's air quality?

London's air quality has improved significantly in recent years. The city now meets legal limits for NO2 (40 µg/m³ annual mean) for the first time since monitoring began. However, London still exceeds the stricter World Health Organisation guidelines for both NO2 (WHO guideline: 10 µg/m³) and PM2.5 (WHO guideline: 5 µg/m³). Air quality varies considerably by location — busy roads, construction sites, and areas near industrial activity remain more polluted than parks and residential streets away from major traffic corridors.

What was the Great Smog of London?

The Great Smog was a severe air pollution event that engulfed London from 5 to 9 December 1952. A combination of cold weather — which drove up domestic coal burning — and a temperature inversion that trapped pollutants at ground level created a dense, toxic smog that persisted for five days. Visibility fell to a few metres. An estimated 4,000 people died in the immediate aftermath, with later research suggesting the true death toll was closer to 12,000 when delayed deaths from respiratory and cardiovascular complications are included. The disaster was the direct catalyst for the Clean Air Act 1956, the UK's first comprehensive legislation to tackle air pollution.

Has ULEZ improved air quality?

Yes. Data published by the Mayor of London's office shows that NO2 concentrations fell by 27% across London compared to what they would have been without ULEZ and its expansions — with reductions of up to 54% in central London. The proportion of vehicles meeting emissions standards rose from 39% in 2017 to 96.7% by late 2024. London met legal NO2 limits in 2024 for the first time, and ULEZ is widely credited as the single most impactful policy in achieving that milestone. However, ULEZ primarily targets exhaust emissions and has less effect on PM2.5 from non-exhaust sources such as tyre and brake wear.

What is the London AQI (Air Quality Index)?

London uses the Daily Air Quality Index (DAQI) — known as the London AQI — a scale from 1 to 10 that communicates current air pollution levels to the public. The index is based on concentrations of five pollutants: nitrogen dioxide (NO2), fine particulate matter (PM2.5), coarse particulate matter (PM10), ozone (O3), and sulphur dioxide (SO2). Levels 1–3 are classified as Low, 4–6 as Moderate, 7–9 as High, and 10 as Very High. Each band carries health advice, particularly for people with pre-existing respiratory or cardiovascular conditions. Real-time DAQI readings are available through the London Air Quality Network and the Defra UK Air website.

Is London air quality getting better?

Yes, significantly. NO2 concentrations have fallen substantially since 2016, driven by ULEZ, fleet electrification, and supporting transport policies. PM2.5 has also improved, though progress is slower because fine particulate pollution comes from a wider range of sources — including tyre and brake wear, domestic burning, cooking, and transboundary pollution — that vehicle emissions standards alone cannot address. Meeting the WHO's recommended PM2.5 guideline of 5 µg/m³ remains a major challenge for London and will require action across multiple sectors beyond transport.

Londons luftkvalitetshistoria

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Londons luftkvalitetshistoria | Sensorbee

Londons relation med luftföroreningar sträcker sig över århundraden. Från koleldade dimsor till den dieseldominerade NO2-krisen på 2010-talet — London möter nu lagliga NO2-gränser för första gången på decennier, men uppfyller fortfarande inte WHO:s riktlinjer för varken NO2 eller PM2.5.

Den stora smogen 1952

I december 1952 skapade en köldvåg och temperaturinversion en dödlig smog över London som varade i fem dagar. Uppskattningsvis 12 000 dog. Det var katalysatorn för Clean Air Act 1956.

Clean Air Acts (1956 och 1968)

Clean Air Act 1956 införde rökfria zoner. Rökkoncentrationerna i London sjönk cirka 80% mellan 1950- och 1980-talen.

Fordonsföroreningarnas framväxt (1970-2000-talen)

Fordonsbeståndet växte till över 2,6 miljoner år 2000. EU:s dieselpolitik gynnade fordon med lägre CO2 men högre NO2/PM2.5. London bröt konsekvent mot EU:s NO2-gränser (40 µg/m³). De hälsoeffekter av luftföroreningar är nu väletablerade.

ULEZ och ren luft

2019: ULEZ centrala London. 2021: Utvidgad till inre London. 2023: Alla stadsdelar. Resultat: 27% minskning av NO2, 96,7% fordon uppfyller standarder. London uppfyllde NO2-gränser 2024, nio år före prognoser.

Var London står idag

| Förorening | Laglig gräns UK | WHO-riktlinje | |-----------|-------|-------| | NO2 | 40 µg/m³ | 10 µg/m³ | | PM2.5 | 20 µg/m³ | 5 µg/m³ | | PM10 | 40 µg/m³ | 15 µg/m³ |

PM2.5 i London: 9-14 µg/m³ — långt över WHO:s 5 µg/m³. Källor: däck- och bromsslitage, vedeldning, matlagning, byggnation, gränsöverskridande föroreningar.

Londons AQI

DAQI-skalan 1-10: Låg (1-3), Måttlig (4-6), Hög (7-9), Mycket hög (10).

Övervaka Londons luft

Sensorbee Air Pro 2 kompletterar befintlig infrastruktur med PM2.5, NO2 och O3 i realtid. Med MCERTS-certifiering uppfyller data kvalitetskraven för regulatorisk rapportering.

Vanliga frågor

Hur dålig är Londons luftkvalitet?

Uppfyller nu lagliga NO2-gränser men överskrider WHO:s strängare riktlinjer.

Vad var den stora smogen?

5-9 december 1952, cirka 12 000 döda, katalysator för Clean Air Act 1956.

Har ULEZ förbättrat luftkvaliteten?

Ja. 27% minskning av NO2, upp till 54% i centrala London.

Förbättras luftkvaliteten?

Ja, betydligt för NO2. PM2.5 framsteg långsammare — bredare källspektrum.

Luftkvaliteten i London: en tidslinje från den stora smogen till idag