> ## Documentation Index
> Fetch the complete documentation index at: https://docs.areahub.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Topics Reference

> All 37 topics and exactly what each returns.

There are 37 topics. They fall into three groups, and **each group returns a different shape in `value`**. Read this before you write parsing code.

<CardGroup cols={3}>
  <Card title="Natural" icon="tornado">
    **18 topics**

    <br />

    `value` is an object with an NRI rating
  </Card>

  <Card title="Proximity" icon="location-crosshairs">
    **14 topics**

    <br />

    `value` is a number
  </Card>

  <Card title="Measurements" icon="gauge">
    **5 topics**

    <br />

    `value` is a measurement object
  </Card>
</CardGroup>

***

## Natural (18)

Backed by the **FEMA National Risk Index (NRI)**, which scores hazard risk by US census tract.

`value` is an object:

```json theme={null}
{
  "title": "Wildfires",
  "rating": "Relatively High",
  "score": 62.4,
  "frequency": 0.83
}
```

| Field       | Type   | Meaning                                  |
| ----------- | ------ | ---------------------------------------- |
| `title`     | string | Human-readable topic name                |
| `rating`    | string | NRI risk category (see below)            |
| `score`     | number | NRI numeric risk score                   |
| `frequency` | number | Annualized event frequency for the tract |

**`rating` is one of:**

`Very Low` · `Relatively Low` · `Relatively Moderate` · `Relatively High` · `Very High` · `No Rating` · `Insufficient Data` · `Not Applicable`

<Note>
  `Not Applicable` is common and expected — e.g. `avalanche` in Manhattan. It
  means the hazard doesn't meaningfully apply to that tract, not that the lookup
  failed.
</Note>

**Topics:**

| Slug            | Topic             | `details`                              |
| --------------- | ----------------- | -------------------------------------- |
| `avalanche`     | Avalanche         | `null`                                 |
| `coastalFlood`  | Coastal Flood     | `null`                                 |
| `coldWave`      | Cold Wave         | `null`                                 |
| `drought`       | Drought           | `null`                                 |
| `earthquake`    | Earthquake        | Object — nearby seismic records        |
| `hail`          | Hail              | Array — historical hail reports        |
| `heatWave`      | Heat Wave         | `null`                                 |
| `hurricane`     | Hurricane         | Array — historical storm tracks        |
| `iceStorm`      | Ice Storm         | `null`                                 |
| `landslide`     | Landslide         | `null`                                 |
| `lightning`     | Lightning         | `null`                                 |
| `riverineFlood` | Riverine Flood    | `null`                                 |
| `strongWind`    | Strong Wind       | `null`                                 |
| `tornado`       | Tornado           | Array — historical tornado reports     |
| `tsunami`       | Tsunami           | `null`                                 |
| `volcano`       | Volcanic Activity | `null`                                 |
| `wildfire`      | Wildfire          | Object — fire perimeters and incidents |
| `winterWeather` | Winter Weather    | `null`                                 |

Five of these (`earthquake`, `hail`, `hurricane`, `tornado`, `wildfire`) pair the NRI rating with a live detail feed. The other 13 return the NRI rating only.

***

## Proximity (14)

Counts of features near the location. `value` is a **plain number**.

```json theme={null}
{
  "value": 60,
  "details": [
    {
      /* GeoJSON features */
    }
  ]
}
```

`details` is a GeoJSON `FeatureCollection` of the individual records that were counted — useful if you need the specific sites, not just how many.

| Slug                    | Topic                     | Counts                              |
| ----------------------- | ------------------------- | ----------------------------------- |
| `brownfield`            | Brownfields               | EPA-tracked brownfield sites        |
| `superfund`             | Superfund Sites           | Superfund / NPL sites               |
| `toxicReleaseInventory` | Toxic Release Inventory   | TRI-reporting facilities            |
| `solidWasteLandfill`    | Landfills                 | Solid waste landfill facilities     |
| `ustFacility`           | UST Facilities            | Underground storage tank facilities |
| `ustRelease`            | UST Releases              | Recorded UST leak/release events    |
| `oilGasWell`            | Oil, Gas & Fracking Wells | Wells                               |
| `naturalGasPipeline`    | Natural Gas Pipelines     | Pipeline segments                   |
| `powerPlant`            | Power Plants              | Generating facilities               |
| `nuclearReactors`       | Nuclear Reactors          | Reactor sites                       |
| `highVoltageLine`       | High Voltage Lines        | Transmission line segments          |
| `cellTower`             | Registered Cell Towers    | Registered towers                   |
| `alternativeFuels`      | EV Charging Stations      | Alternative fuel / EV stations      |
| `park`                  | Parks                     | Parks                               |

<Warning>
  A count of `0` is a valid answer — it means no features were found near that
  location. It is not an error.
</Warning>

***

## Measurements (5)

Each returns a domain-specific object. **These do not share a common shape** — handle each individually.

### `airQuality`

Annual air quality summary for the county.

```json theme={null}
{
  "metric": "Unhealthy for Sensitive Groups",
  "progressValue": 101,
  "additionalInfo": {
    "daysWithAqi": 366,
    "goodDays": 107,
    "moderateDays": 221,
    "unhealthyForSensitiveGroupsDays": 31,
    "unhealthyDays": 6,
    "veryUnhealthyDays": 1,
    "hazardousDays": 0,
    "maxAqi": 208,
    "medianAqi": 59
  }
}
```

`details` is `null`.

### `ozone` · `pm25` · `pm10`

Current pollutant concentration at the coordinates.

```json theme={null}
{
  "measurement": { "value": 116.83, "unit": "µg/m³" },
  "rating": "Good",
  "timestamp": "2026-07-14T16:31:55.009Z"
}
```

| Field               | Meaning                            |
| ------------------- | ---------------------------------- |
| `measurement.value` | Concentration                      |
| `measurement.unit`  | Always `µg/m³`                     |
| `rating`            | AreaHub air quality classification |
| `timestamp`         | When the measurement was taken     |

`details` is `null`.

<Note>
  **`rating` is an AreaHub risk rating or an official EPA AQI Category where
  applicable.** For EPA-compliant AQI, compute the AQI from `measurement.value`
  — that raw concentration is the authoritative field.
</Note>

### `radon`

EPA average radon zone designation for the county.

```json theme={null}
{
  "title": "Radon Zones",
  "value": "Low",
  "caption": "Low potential",
  "description": "Radon Zones helps national, state, and local organizations implement radon-resistant building codes..."
}
```

`details` is `null`.

<Note>
  The `description` field is EPA's standard advisory text. It is identical on
  every response and does not vary by location.
</Note>

***

## Which topics are in which bundle?

| Bundle         | Topics            | Credits |
| -------------- | ----------------- | ------- |
| **Standard**   | 18 natural topics | 15      |
| **Enterprise** | All 37            | 35      |

Any topic can also be requested individually via `GET /v1/{slug}/risk` for 1 credit.

***

## Update frequency

| Topic                                              | Cadence                                     |
| -------------------------------------------------- | ------------------------------------------- |
| `alternativeFuels`                                 | Daily                                       |
| `ozone`, `pm25`, `pm10`                            | Near real-time                              |
| `brownfield`, `superfund`, `toxicReleaseInventory` | Rolling — records update as agencies report |
| All NRI hazard ratings                             | Per FEMA NRI release cycle                  |
| `nuclearReactors`                                  | Static snapshot                             |