u/FeynmanDemon

I pulled EPA's federal PFAS drinking water testing data for Georgia and mapped it by county. Full maps and county-by-county tables are attached. Here's the metro Atlanta part.

What the data is:

EPA's Fifth Unregulated Contaminant Monitoring Rule (UCMR5), January 2023 through December 2025. 48,110 test results from 255 Georgia public water systems, covering 128 of 159 counties. This is EPA's published data, not my sampling.

Metro Atlanta counties with PFAS detected

(ppt = parts per trillion; the federal limit for PFOA and PFOS is 4 ppt each):

| County | PFOA | PFOS |

| Fulton | 9.3 | 6.4 |

| Clayton | 8.4 | 8.5 |

| Cherokee | 6.8 | 5.3 |

| Coweta | 6.7 | 4.5 |

| Henry | 4.1 | 5.6 |

| Barrow | 4.5 | 4.3 |

| Jackson | 4.2 | 4.6 |

| Paulding | 4.5 | — |

| Fayette | — | 4.4 |

Cobb, Rockdale, and Walton had other PFAS compounds detected but not PFOA or PFOS. Gwinnett, DeKalb, Forsyth, Newton, and Oconee were sampled and had no PFAS detected at all.

Outside the metro but worth knowing about:

Spalding County (Griffin) came in at 14.0 ppt PFOS with a Hazard Index of 2.0 — double the federal limit on the mixture standard. Richmond County (Augusta) is the worst in the state on that measure at 5.12. The highest single reading anywhere in Georgia was Walker County at 56 ppt PFOS, fourteen times the limit.

Three things you should know before reading the maps:

1. A blank county doesn't mean clean water — it means nobody tested.

31 Georgia counties had no water system in this program at all. UCMR5 tested every system serving 3,300+ people and only a sample of smaller ones. I shaded untested counties differently on purpose, because merging them with "tested, found nothing" would imply a safety finding that was never made.

2. The lab's detection floor is exactly the legal limit.

EPA's minimum reporting limit for PFOA and PFOS is 4 ppt. The federal MCL is also 4 ppt. So anything between 0 and 4 ppt is invisible in this data, and every number you see is at or above the legal limit by definition. When a county shows "4.5," that's not "barely detectable" — it's above the standard.

3. This is finished drinking water at the treatment plant entry point

Not your tap, and not the river. Counties are assigned by the water system's registered county, which isn't always where the intake is.

One more thing that surprised me.

Georgia EPD runs a large ambient water monitoring program — 251,493 test results across 643 stations statewide between January 2024 and March 2026. Zero of those results are PFAS. Not "tested and came back clean": PFAS isn't on the list of 159 things they test for, so no sample was ever analyzed for it. Meanwhile 66 Georgia counties have PFAS in their finished drinking water and 33 are at or above a federal limit. The most-measured parameters are temperature, dissolved oxygen, conductivity, and pH.

Disclosure
I'm not neutral here. I'm a Floyd County water customer and I have an ongoing dispute with EPA Region 4 about how they've handled PFAS oversight in Georgia. That's why I built this. But the data is EPA's own published dataset, the county tables are attached so you can check every shaded county against its numbers, and anyone can reproduce it from the same download. Nothing here is my measurement or my estimate.

If you want to check your own system:

Search your water utility's name in EPA's UCMR5 data, or look at your annual Consumer Confidence Report, which your utility is required to publish by July 1 each year. Worth noting that CCRs don't always report UCMR5 results the way you'd expect, particularly if your system buys water from another system.

Happy to answer questions about the data or the methodology.

I mapped EPA's federal PFAS testing data for every county in Georgia.

The numbers: 48,110 test results from 255 public water systems, 2023–2025. PFAS was detected in 66 counties. The highest readings were PFOS at 56 ppt in Walker County, PFOA at 33.9 ppt in Muscogee, and a Hazard Index of 5.1 in Richmond — the federal limit is 4 ppt for PFOA and PFOS, and 1.0 for the Hazard Index.

Two things to keep in mind when you look at these:

1. A blank county does NOT mean clean water. It means nobody tested there. Thirty-one Georgia counties had no water system in this program at all. I shaded those differently on purpose.
2. The lab's minimum reporting limit for PFOA and PFOS is 4 ppt — exactly the same as the legal limit. So any amount between zero and 4 ppt is simply invisible in this data. Every detection you see is at or above the limit by definition.

ABOUT THE "KAPLAN–MEIER" BOX ON EACH MAP

Here's the problem it solves. In 97.6% of these tests, the lab reported "< MRL" — meaning PFAS was below what the instrument could measure. That is not the same as zero. It means somewhere between nothing and 4 ppt, and we can't tell where.

If you treat all of those as zero, you understate the real average. If you treat them as 4 ppt, you overstate it. Kaplan–Meier is an ADJUSTED CONCENTRATION ESTIMATE — a standard statistical method (the same math used in medical survival studies) that uses the pattern of the results you CAN measure to estimate the true average without guessing at the ones you can't.

What each line means:

• Results statewide — how many individual tests for that chemical were run in Georgia.

• Left-censored — how many of those came back "below the reporting limit." "Left" just means below the measurable range.

• KM mean — the adjusted statewide average, accounting for those below-limit results properly.

• KM 95th percentile — the level that only 5% of samples exceeded. The high end, not the typical case.

• ROS mean and MLE mean — two alternative methods for the same adjustment, shown side by side. When three different methods land in the same range, you can trust the estimate. When they disagree, that itself tells you something.

These are statewide figures. The colors on the map are actual maximum readings from individual counties, not estimates.

This is EPA's own public UCMR5 dataset — not my measurements.

I mapped EPA's federal PFAS testing data for every county in Georgia.

The numbers: 48,110 test results from 255 public water systems, 2023–2025. PFAS was detected in 66 counties. The highest readings were PFOS at 56 ppt in Walker County, PFOA at 33.9 ppt in Muscogee, and a Hazard Index of 5.1 in Richmond — the federal limit is 4 ppt for PFOA and PFOS, and 1.0 for the Hazard Index.

Two things to keep in mind when you look at these:

1. A blank county does NOT mean clean water. It means nobody tested there. Thirty-one Georgia counties had no water system in this program at all. I shaded those differently on purpose.
2. The lab's minimum reporting limit for PFOA and PFOS is 4 ppt — exactly the same as the legal limit. So any amount between zero and 4 ppt is simply invisible in this data. Every detection you see is at or above the limit by definition.

ABOUT THE "KAPLAN–MEIER" BOX ON EACH MAP

Here's the problem it solves. In 97.6% of these tests, the lab reported "< MRL" — meaning PFAS was below what the instrument could measure. That is not the same as zero. It means somewhere between nothing and 4 ppt, and we can't tell where.

If you treat all of those as zero, you understate the real average. If you treat them as 4 ppt, you overstate it. Kaplan–Meier is an ADJUSTED CONCENTRATION ESTIMATE — a standard statistical method (the same math used in medical survival studies) that uses the pattern of the results you CAN measure to estimate the true average without guessing at the ones you can't.

What each line means:

• Results statewide — how many individual tests for that chemical were run in Georgia.

• Left-censored — how many of those came back "below the reporting limit." "Left" just means below the measurable range.

• KM mean — the adjusted statewide average, accounting for those below-limit results properly.

• KM 95th percentile — the level that only 5% of samples exceeded. The high end, not the typical case.

• ROS mean and MLE mean — two alternative methods for the same adjustment, shown side by side. When three different methods land in the same range, you can trust the estimate. When they disagree, that itself tells you something.

These are statewide figures. The colors on the map are actual maximum readings from individual counties, not estimates.

This is EPA's own public UCMR5 dataset — not my measurements.