What's the air quality in Welwyn Hatfield? NO₂ 12.2 µg/m³
In 2025 the average resident of Welwyn Hatfield lived with background NO₂ of 12.2 µg/m³, Very High for England and Wales and 1.2 times the WHO guideline of 10. PM2.5 was 8.7 µg/m³, Very High for England and Wales and 1.7 times the WHO guideline of 5. The typical area in England and Wales has NO₂ of 7.2 and PM2.5 of 7.4 µg/m³.
- PM2.5
- 8.7 µg/m³
- NO₂ for England and Wales
- Very High
- Figures for
- 2025 annual average
Modelled background levels averaged over where residents live (Census 2021), not roadside levels. Contains public sector information licensed under the Open Government Licence v3.0. Source: Defra modelled background pollution, 2025. How we calculate this
All house prices in Welwyn HatfieldIs the air quality good in Welwyn Hatfield?
Background NO₂ in Welwyn Hatfield is 12.2 µg/m³, 1.2 times the WHO guideline of 10, and higher than the typical area (7.2). That puts it in the Very High band. Background PM2.5 in Welwyn Hatfield is 8.7 µg/m³, 1.7 times the WHO guideline of 5, and higher than the typical area (7.4). That puts it in the Very High band. Most of England and Wales is above the WHO guideline for PM2.5, so the bands compare places with each other rather than giving a pass or fail.
Nitrogen dioxide (NO₂): 12.2 µg/m³
NO₂ level is Very High, on a scale from Very Low to Very High.
Very High means the highest fifth of areas in England and Wales for NO₂.
| Very Low | up to 4.7 |
|---|---|
| Low | 4.7 to 6.5 |
| Typical | 6.5 to 7.7 |
| High | 7.7 to 9.2 |
| Very High | over 9.2 |
WHO guideline: 10 µg/m³ (in the Very High band). UK legal limit: 40 µg/m³.
Fine particles (PM2.5): 8.7 µg/m³
PM2.5 level is Very High, on a scale from Very Low to Very High.
Very High means the highest fifth of areas in England and Wales for PM2.5.
| Very Low | up to 6.0 |
|---|---|
| Low | 6.0 to 7.2 |
| Typical | 7.2 to 7.7 |
| High | 7.7 to 8.2 |
| Very High | over 8.2 |
WHO guideline: 5 µg/m³ (in the Very Low band). UK legal limit: 20 µg/m³, with a target of 10 µg/m³ in England by 2040.
The bands split every area we cover into fifths by its level, from Very Low to Very High. The map uses the same colours.
Which part of Welwyn Hatfield has the cleanest air?
Ayot St Lawrence has the lowest background NO₂ of the 8 areas of Welwyn Hatfield, at 9.8 µg/m³. Hatfield has the highest, at 13.0 µg/m³. Average house prices are shown alongside, so you can weigh air quality against cost.
| Area | NO₂ | PM2.5 | NO₂ band | Average price |
|---|---|---|---|---|
| Ayot St LawrenceVery High | 9.8 | 8.3 | Very High | — |
| Woolmer GreenVery High | 9.9 | 8.4 | Very High | £425,055 |
| EssendonVery High | 10.4 | 8.5 | Very High | £536,000 |
| Northaw and CuffleyVery High | 10.9 | 8.6 | Very High | £740,206 |
| WelwynVery High | 11.2 | 8.4 | Very High | £719,099 |
| Ayot St PeterVery High | 11.2 | 8.4 | Very High | — |
| North MymmsVery High | 11.4 | 8.6 | Very High | £747,660 |
| HatfieldVery High | 13.0 | 8.8 | Very High | £433,560 |
Levels in µg/m³, 2025 annual average.
How does air quality in Welwyn Hatfield compare with nearby areas?
Background NO₂ in Welwyn Hatfield compared with the 6 nearest other areas in Hertfordshire.
Welwyn Hatfield vs Broxbourne
- Welwyn Hatfield
- NO₂ 12.2 µg/m³
- Broxbourne
- NO₂ 13.0 µg/m³
Open comparison
Welwyn Hatfield vs St Albans
- Welwyn Hatfield
- NO₂ 12.2 µg/m³
- St Albans
- NO₂ 12.4 µg/m³
Open comparison
Welwyn Hatfield vs Hertsmere
- Welwyn Hatfield
- NO₂ 12.2 µg/m³
- Hertsmere
- NO₂ 12.6 µg/m³
Open comparison
Welwyn Hatfield vs Stevenage
- Welwyn Hatfield
- NO₂ 12.2 µg/m³
- Stevenage
- NO₂ 11.0 µg/m³
Open comparison
Welwyn Hatfield vs East Hertfordshire
- Welwyn Hatfield
- NO₂ 12.2 µg/m³
- East Hertfordshire
- NO₂ 10.9 µg/m³
Open comparison
Welwyn Hatfield vs Watford
- Welwyn Hatfield
- NO₂ 12.2 µg/m³
- Watford
- NO₂ 14.1 µg/m³
Open comparison
Does this include busy roads?
No. These are background levels: yearly averages over 1 km squares, away from the immediate influence of roads. Right beside a busy road in Welwyn Hatfield, NO₂ can be much higher. Councils publish roadside monitoring in their annual air quality reports.
What else do people ask about Welwyn Hatfield?
More quick answers on house prices, sales, areas, green space, crime, air quality and listed buildings in Welwyn Hatfield.
- What is the average house price in Welwyn Hatfield?
- When did average house prices in Welwyn Hatfield reach their peak?
- How many properties are being sold in Welwyn Hatfield?
- What type of properties are sold in Welwyn Hatfield?
- What price range do most homes sell for in Welwyn Hatfield?
- What is the most expensive (and cheapest) area of Welwyn Hatfield?
- How many parks and green spaces are in Welwyn Hatfield?
- What is the crime rate in Welwyn Hatfield?
- How many listed buildings are in Welwyn Hatfield?
- How do Welwyn Hatfield house prices compare with another area?
Where does this data come from?
Price information is from HM Land Registry, location boundaries are from OpenStreetMap, and households and population are from Nomis Census 2021 postcode estimates (21 March 2021). Parks and green space are from OS Open Greenspace. Contains OS data © Crown copyright and database right 2026. Crime is from police.uk street-level data. Contains public sector information licensed under the Open Government Licence v3.0. Source: police.uk. Listed buildings and scheduled monuments are from Historic England and Cadw, and conservation areas from planning.data.gov.uk. © Historic England 2026. Contains Ordnance Survey data © Crown copyright and database right 2026. Source: planning.data.gov.uk, Open Government Licence v3.0. Air quality is from Defra modelled background pollution maps. Contains public sector information licensed under the Open Government Licence v3.0. Source: Defra modelled background pollution, 2025.
Last updated 11 November 2026 at 01:27 with the latest Land Registry data (September 2026). The Welwyn Hatfield dataset covers 4,742 postcodes.
Contains HM Land Registry data © Crown copyright and database right 2026. This data is licensed under the Open Government Licence v3.0.
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