Full contaminant data, sample history, and sourcing for Jefferson County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
486 well testing events on record, covering
20 analytes.
Data spans 1907 to 2023.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. TX Avg
Manganese
62
1959–2021
90%
111% of limit
↑ 72% above
Chloride
276
1907–2005
100%
90% of limit
↑ 150% above
Iron
109
1945–2021
94%
60% of limit
↓ 61% below
Nitrate
88
1941–2005
40%
10% of limit
↓ 55% below
Arsenic
60
1987–2021
25%
25% of limit
↓ 34% below
Sulfate
226
1907–2005
100%
1% of limit
↓ 96% below
Fluoride
255
1941–2021
98%
10% of limit
↓ 58% below
HFPO-DA (GenX)
municipal
31
2023–2025
0%
—
—
Lead
59
1988–2021
14%
1% of limit
↓ 95% below
Nitrite
5
2005
0%
—
—
PFHxS
municipal
30
2023–2025
0%
—
—
PFNA
municipal
30
2023–2025
0%
—
—
PFOA
municipal
30
2023–2025
0%
—
—
PFOS
municipal
30
2023–2025
0%
—
—
Radon
4
2005
100%
6% of limit
↓ 83% below
Uranium
19
2005–2021
0%
—
—
Sodium
110
1907–2005
100%
—
↑ 88% above
pH
76
1945–2005
100%
—
~ typical
PFBS
municipal
30
2023–2025
0%
—
—
Hardness
241
1907–2005
100%
—
~ typical
Distribution shows the share of samples in each concentration band relative to the EPA Maximum Contaminant Level (MCL): Low = below half the MCL, Moderate = between half and the MCL, High = above the MCL. Analytes without an MCL (e.g. sodium, pH) show — in the limit columns. State average is based on county median values across TX.
Compare your result with Jefferson County
Of the 60 arsenic tests on record for Jefferson County (1987–2021),
75% found none.
Of the 276 chloride tests on record for Jefferson County (1907–2005),
0% found none, and half were below 224 mg/L.
Of the 255 fluoride tests on record for Jefferson County (1941–2021),
2% found none, and half were below 400 µg/L.
Of the 109 iron tests on record for Jefferson County (1945–2021),
6% found none, and half were below 161 µg/L.
Of the 59 lead tests on record for Jefferson County (1988–2021),
86% found none.
Of the 62 manganese tests on record for Jefferson County (1959–2021),
10% found none, and half were below 43.7 µg/L.
Of the 88 nitrate tests on record for Jefferson County (1941–2005),
60% found none.
Of the 226 sulfate tests on record for Jefferson County (1907–2005),
0% found none, and half were below 3 mg/L.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Manganese 62 samples
Chloride 276 samples
Iron 109 samples
Nitrate 88 samples
Arsenic 60 samples
Sulfate 226 samples
Fluoride 255 samples
Lead 59 samples
Uranium 19 samples
Sodium 110 samples
pH 76 samples
Hardness 241 samples
Limited data (<15 samples) — interpret with caution
Nitrite 5 samples
Radon 4 samples
No private-well PFAS data for Jefferson County
We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Jefferson County.
PFAS testing for private wells requires a dedicated lab panel (~$300–$500). If you are near a military base, airport, or industrial site, consider testing proactively. Learn more about PFAS →
Public vs. Private Water in Jefferson County
25Active public water systems
253,440Residents on public water
2%Households on private wells
Public water systems in Jefferson County are regulated by the EPA and must test and report contaminant levels. Private well owners are responsible for their own testing — there is no routine monitoring of private wells by any government agency.
CDC Health Outcome Correlations
Where contaminants detected in Jefferson County have established associations with specific health outcomes, we cross-reference CDC PLACES county-level prevalence data. This is a contextual signal, not a causal claim.
This report aggregates data from the following public databases:
Water Quality Portal (WQP) — groundwater sample results for Jefferson County from EPA, USGS, and state agencies. Browse WQP data →
EPA Safe Drinking Water Information System (SDWIS) — public water system inventory used to estimate the share of residents on private wells. Browse SDWIS →
Census ACS 5-Year Estimates — well and cistern household counts (variable DP04_0074E) used to calculate the private-well percentage for Jefferson County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Jefferson County, which informs which contaminants are geologically likely. USGS Aquifer Atlas →
EPA UCMR 5 (2023–2025) — PFAS occurrence data from public water systems, used as a proxy indicator for aquifer PFAS exposure. Rows marked "municipal" in the table above come from this source. About UCMR 5 →
EPA Toxics Release Inventory (TRI) — industrial facility chemical releases near Jefferson County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Jefferson County, used in contamination risk scoring. Superfund site search →
CDC PLACES — county-level health outcome prevalence (kidney disease, cancer, heart disease) correlated with detected contaminants. About CDC PLACES →
Methodology
Raw records are downloaded from the Water Quality Portal and normalized to µg/L (ppb). Records are deduplicated by sample ID and date, and certified outliers are excluded. Analyte names are mapped to EPA canonical forms. Detection rates, distribution bands, and MCL comparisons are computed from the normalized dataset.
Distribution bands use the EPA Maximum Contaminant Level as the threshold: concentrations below 50% of the MCL are classed as Low, between 50% and 100% as Moderate, and above 100% as High. For analytes without an MCL (sodium, hardness, pH), distribution is not computed.
State comparison uses the median of county median values across all counties in TX with at least one sample for that analyte.