The Embr Exposure Ledger
One open table that joins four public exposure datasets, chemical by chemical: whether a compound is detected in US tap water, whether it turns up in human blood or urine, whether California law flags it, and whether anything is known to reduce it. The facts are all public. The join is not: no one else lines these four questions up against one compound record and reads a verdict across them. It is free to download and cite, with attribution.
Of 124 chemicals joined across four public exposure datasets, only two — PFOA and PFOS — appear in all four: detected in US tap water, measurable in human blood, listed under California Proposition 65, and with a documented way to reduce exposure.
Source: Embr Exposure Ledger v1.1, 2026-07-14.What the ledger is, and why the join matters
Take a chemical you might worry about at home. Four separate public datasets each answer one question about it. The EPA's drinking-water monitoring says whether it shows up in tap water. The CDC's biomonitoring program says whether it shows up in people. California's Proposition 65 list says whether the law has flagged it. And the evidence on interventions says whether anything actually lowers your exposure. Each dataset lives on its own, in its own format, keyed its own way.
The Embr Exposure Ledger joins all four onto a single compound record, matched CAS number first and name second against the Embr Bedroom Chemistry Atlas. A chemical that appears in three of the datasets becomes a three-spoke record; one that appears in all four is a complete record. Where a dataset has nothing for a compound, that spoke is marked "no data" rather than dropped or guessed.
Why is a join worth more than the four datasets it draws from? Because the raw facts are already everywhere, and a large language model has most of them. A join is unique if any single input is unique. Two of these inputs are Embr's own: the curated Atlas that the datasets are matched against, and the Verdict Layer that reads a plain, evidence-tiered verdict across the spokes. That is the part that exists nowhere else, and it is what turns four commodity datasets into one asset.
The four spokes
Each spoke answers one exposure question and carries its source with it, so any figure can be traced back to the agency that published it.
| Spoke | Question | Dataset | Source |
|---|---|---|---|
| Environment | Is it around me? | EPA UCMR 5 — Unregulated Contaminant Monitoring Rule, 5th cycle (drinking water) | EPA |
| Body | Is it in me? | CDC National Report on Human Exposure to Environmental Chemicals (NHANES biomonitoring) | CDC |
| Regulatory | Does the law flag it? | California OEHHA Proposition 65 List | OEHHA |
| Remediation | What reduces it? | Embr curated, evidence-tiered intervention data | Embr Atlas |
The most-joined compounds
Of the 124 compounds in the ledger, most appear in a single dataset. The ones below are the exceptions — the compounds that surface in three or four of the exposure questions at once. These are where the join earns its keep. Each links to its full, cited page in the Atlas.
| Compound | CAS | Environment | Body | Regulatory | Remediation | Spokes |
|---|---|---|---|---|---|---|
| Perfluorooctanoic acid (PFOA) | 335-67-1 | Yes | Yes | Yes | Yes | 4 |
| Perfluorooctane sulfonate (PFOS) | 1763-23-1 | Yes | Yes | Yes | Yes | 4 |
| Arsenic | 7440-38-2 | — | Yes | Yes | Yes | 3 |
| Benzyl butyl phthalate (BBP) | 85-68-7 | — | Yes | Yes | Yes | 3 |
| Dibutyl phthalate (DBP) | 84-74-2 | — | Yes | Yes | Yes | 3 |
| Di(2-ethylhexyl) phthalate (DEHP) | 117-81-7 | — | Yes | Yes | Yes | 3 |
| Lead | 7439-92-1 | — | Yes | Yes | Yes | 3 |
| Perfluorohexane sulfonate (PFHxS) | 355-46-4 | Yes | Yes | — | Yes | 3 |
| Perfluorononanoic acid (PFNA) | 375-95-1 | Yes | Yes | — | Yes | 3 |
Coverage as of v1.1: 124 compounds joined — 2 four-spoke records, 7 three-spoke, 16 two-spoke, and 99 that currently appear in a single dataset. A new spoke does not add pages; it adds a column, so a two-spoke compound can become three-spoke as the datasets grow.
Download and reuse
The full ledger is published as machine-readable JSON and as a flat CSV. Both are free to reuse with attribution. Every value is copied from its public source; the join, the tiers, and the verdicts are Embr's.
Cite it as:
Method, and what the ledger does not claim
The datasets are copied verbatim from their public sources and joined by record linkage: CAS number first, chemical name second. A match that fails returns nothing and is surfaced honestly; it is never patched with a guess. Nothing in the ledger is invented — not a value, not a CAS, not a verdict, not a listing.
Read these caveats before you quote a figure
- Occurrence is not risk. A chemical being detected in water, or measurable in blood, says it is present. It does not by itself say it is harming anyone at that level. Dose, duration, and who is exposed all matter.
- A null spoke means "no data," not "safe." When a dataset has nothing for a compound, that spoke is blank. That is a gap in what has been measured, not a clean bill of health.
- A Proposition 65 listing is a legal fact, not a risk verdict. It records that California has listed the chemical for cancer or reproductive harm under state law. It is not a statement about the exposure you personally face.
- The evidence tiers travel with each claim. An intervention marked Peer-reviewed rests on published journal literature; one marked Regulatory rests on an agency or standards body. The tier is part of the data, so you can weigh it. The full definitions live on the methodology page.
Want the datasets in plain language? What's in your tap water reads the water spoke compound by compound, the PFAS national picture covers the forever-chemical findings, and the Atlas is the compound library the whole ledger is built on.