The discipline
Methodology and sources
Every figure on this site is a count or value from a federal dataset row. Nothing is modeled, estimated or written from memory, and no page exists that does not correspond to real records. All datasets were last retrieved on 2026-09-03 and are refreshed quarterly.
Umwelt keeps a mirrored copy of every raw file it builds from. If a federal source is taken offline, as several public screening tools were in 2025 and 2026, the site continues to rebuild and report from its mirrors, and says so where it matters.
Reading discipline: this site reports detections as detections, exceedances only against limits that are final law, and cleanup statuses in EPA's own vocabulary with a plain-language translation. It never renders a "safe" or "dangerous" verdict about any place, because records cannot support one.
The datasets
| Dataset | Source | Coverage |
|---|---|---|
| Superfund NPL | EPA GeoPlatform: Superfund National Priorities List (NPL) Sites with Status Information | 1,840 sites |
| Federal cleanup inventory | EPA GeoPlatform: FRS_INTERESTS_SEMS | 14,980 sites |
| Underground storage tanks | EPA UST Finder, county aggregation layers | 3,134 county rollups |
| PFAS occurrence | EPA UCMR5 occurrence data (bulk download) | 10,313 systems |
| Water system service areas | EPA Envirofacts SDWIS GEOGRAPHIC_AREA | PWSID to county |
| Toxic releases | EPA Toxics Release Inventory, 2024 basic file | 21,482 facilities |
| County spine and radon | US Census via lung.com pipeline; EPA radon zones | 3,143 counties |
Known limits, stated plainly
- UCMR5 sampled all systems serving over 3,300 people and a partial sample of smaller ones, so a small system absent from the PFAS tables may simply not have been tested.
- Site coordinates carry EPA's own stated accuracy limits; a distance of 0.2 miles is a map fact, not a survey.
- TRI is self-reported by facilities, reports lawful releases, and covers listed chemicals above thresholds only.
- A county rollup attributes a multi-county site to its first listed county; the site page names every county.
- Territories appear in site registers but have no county pages, because the county spine covers the 50 states and DC.