Environmental risk — methodology

1. Data sources, licence & cadence

The environmental risk section is a composite view. It pulls together headline indicators from four independent data sources, each of which has its own dedicated module elsewhere in the report.

1.1 Environment Agency — flood data

Data provided: Statutory flood zones (Zone 2 / Zone 3), live flood warnings and alerts, recorded historical flood outlines. Detailed methodology: flood risk methodology.
Licence: Open Government Licence v3.0.
Refresh cadence: Live API; flood warnings update every 15 minutes.

1.2 Open-Meteo Air Quality / CAMS — air quality

Data provided: Pollutant readings (NO₂, PM_2.5, PM₁₀, O₃, SO₂, CO) from the European Copernicus Atmosphere Monitoring Service (CAMS) ensemble forecast on a ~11 km grid, served via the Open-Meteo Air Quality API. CAMS itself assimilates UK reference-network data (DEFRA UK-AIR / AURN) among other inputs. Detailed methodology: air quality methodology.
Licence: Open-Meteo terms of use; CAMS source data under the Copernicus licence.
Refresh cadence: Live API; readings reflect the latest hourly CAMS forecast value, typically less than three hours behind real time.

1.3 BGS / UKHSA — Indicative Atlas of Radon

Data provided: Radon risk band (Low / Medium / High / Very High) and the estimated percentage of homes within the 1 km grid square that exceed the UKHSA Action Level of 200 Bq/m³.
Licence: Open Government Licence v3.0. Contains British Geological Survey materials © UKRI 2026. Radon Potential classification UK Health Security Agency © Crown copyright 2026.
Source: ukradon.org and the BGS GeoIndex.
Refresh cadence: The BGS/UKHSA Indicative Atlas is republished on ~5-year cycles; the current edition is the 3rd edition (2022). We re-load within two weeks of each new edition.

1.4 Natural England — designated & protected sites

Data provided: Whether the property sits inside a Site of Special Scientific Interest (SSSI), National Nature Reserve (NNR), Special Area of Conservation (SAC), Special Protection Area (SPA), Ramsar site, Area of Outstanding Natural Beauty (AONB), or National Park.
Licence: Open Government Licence v3.0. Contains Natural England data © Crown copyright and database right 2026.
Refresh cadence: Natural England publishes per-dataset updates quarterly; we refresh in line with each release.

2. What we do

For designated sites we run a PostGIS point-in-polygon query: the property's coordinates are tested against the loaded boundaries for each statutory designation, and we report any designation whose polygon contains the point. This is a binary fact, not a probabilistic estimate — a property is either inside an SSSI or it is not.

For radon we look up the property's coordinates against the BGS/UKHSA 1 km grid, retrieve the percentage of homes in that grid square estimated to exceed the 200 Bq/m³ UKHSA Action Level, and translate that percentage into one of four risk bands (Low / Medium / High / Very High) using the official UKHSA 1% / 3% / 10% thresholds. The report includes a textual description of the band's meaning and a link to ukradon.org for further information.

The flood and air-quality components are sourced live from their respective APIs and surfaced through their dedicated modules; the environmental risk section summarises the headline findings and points back to the detailed sections.

3. What we do not do

• We do not run a Phase 1 desk study. A Phase 1 environmental desk study (as defined by BS 10175 and BS 5930) is a chartered-environmentalist-authored review of historical maps, mining records, licensed industrial activities, and bore-hole data. Our report is not a Phase 1 study.
• We do not check ground stability or mining records. Coal Authority mining-area searches, non-coal mining searches, gypsum, brine, and limestone karst checks are all outside our V1 scope.
• We do not check radon at the property level. The BGS/UKHSA Indicative Atlas is a 1 km grid; it is the right input for screening, not for measurement. The only way to know your home's actual radon concentration is a 3 month UKHSA validated detector measurement.
• We do not check Part 2A contaminated-land registers — see the dedicated section below.
• We do not perform a soil contamination assessment. Identifying and characterising soil contamination requires intrusive site investigation by a qualified geo-environmental consultant.

4. Contaminated land — by-design scope statement

Contaminated land in England is regulated under Part 2A of the Environmental Protection Act 1990. Each local authority is the “enforcing authority” for its area and is required to maintain a register of land it has formally determined as contaminated under that regime. There are 296 such authorities in England — 296 separate registers, kept in 296 different formats, with no national API or unified dataset.

We have looked at this carefully and made a deliberate call: we will not ship a national contaminated-land overlay for V1. Our reasoning:

• There is no public API. Building a national dataset would require manually scraping or FOI-requesting 296 individual registers, normalising their formats, and rebuilding that pipeline every time a council changed how they publish. The cost-to-completeness ratio is poor for a generalist consumer report.
• The professional product is excellent and cheap. The regulated environmental search your conveyancer commissions already does this job — it cross-references the local authority register, historical OS maps, current and historical industrial use, landfill databases, mining, and radon — and is included in nearly every conveyancing search pack. At £30–£50, it is the right tool, used at the right point in the buying process.
• A worse half-version would mislead. Shipping a partial contaminated-land flag based on, say, the 30 largest authorities' registers would create a silent false-negative for everyone outside those 30 areas. We would rather be explicit that we do not cover this and direct buyers to the professional search than ship a flag that looks complete but is not.

If you want a contaminated-land check now, two options:

• Ask your local council. Find the right authority at gov.uk/find-local-council and ask the Environmental Health team to check the Part 2A register. This is free but the response time varies (1–6 weeks).
• Commission an Environmental Search at conveyancing. Your conveyancer or solicitor will arrange this as part of the standard search pack. It is fast (24–48 hours), comprehensive, and definitive.

We may revisit this scope decision after launch (H2+) if a high-quality national dataset becomes available. Until then, this is the best available steer for consumers.

5. Known limitations

• Composite headline only. The environmental risk section is a cross-module summary; the underlying detail lives in the flood, air quality, and radon modules. If you want the full picture for a single risk, follow the module-specific link.
• Designated sites are point-in-polygon, not within-distance. A property 50 m outside an SSSI boundary will report “no designation” even though development on that property would in practice need to consider the SSSI's impact-risk zones. For development-stage analysis, use the DEFRA MAGIC map.
• Radon is grid-level, not address-level. Two homes 200 m apart can have very different actual radon readings depending on building construction and ground beneath the slab. The atlas is a screening tool; only a measurement tells you your home's value.
• No mining, no ground stability, no historical land use. See section 3.
• No contaminated-land register coverage. See section 4 above — this is by design, not a bug.

6. What this is not a substitute for

7. Disclaimer

The environmental risk section is general information only, compiled from third-party public data under the licences listed above. It is not an environmental assessment, does not satisfy any statutory or contractual requirement, and is not insured. For the full liability framework that governs every Home-Checker report, please read the Report Disclaimer. For attribution and licensing of every dataset we use, see Data sources & attribution.

Other module methodology pages: methodology index.