Full contaminant data, sample history, and sourcing for Bexar County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
7495 well testing events on record, covering
22 analytes.
Data spans 1908 to 2023.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. TX Avg
Sulfate
3487
1908–2023
100%
14% of limit
↓ 50% below
Chloride
3582
1908–2023
100%
10% of limit
↓ 72% below
Iron
3269
1911–2022
46%
12% of limit
↓ 92% below
Radon
39
1990–2017
100%
13% of limit
↓ 65% below
Manganese
3090
1946–2022
20%
20% of limit
↓ 69% below
Fluoride
5791
1939–2023
98%
8% of limit
↓ 69% below
Nitrate
1575
1939–2023
96%
16% of limit
↓ 28% below
Lead
2132
1968–2022
29%
7% of limit
↓ 60% below
Arsenic
2601
1969–2022
34%
10% of limit
↓ 74% below
HFPO-DA (GenX)
municipal
225
2023–2025
0%
—
—
Nitrite
1116
1975–2023
22%
1% of limit
~ typical
PFHxS
municipal
225
2023–2025
0%
—
—
PFNA
municipal
225
2023–2025
0%
—
—
PFOA
municipal
225
2023–2025
0%
—
—
PFOS
municipal
225
2023–2025
0%
100% of limit
↓ 23% below
Uranium
685
1996–2022
52%
3% of limit
↓ 83% below
Hardness
3428
1908–2023
100%
—
↑ 32% above
E. coli
40
2004–2018
28%
—
~ typical
Total Coliform
37
1968–2018
70%
—
~ typical
Sodium
2462
1941–2023
100%
—
↓ 89% below
pH
3587
1941–2024
100%
—
~ typical
PFBS
municipal
225
2023–2025
2%
—
~ 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 Bexar County
Of the 2601 arsenic tests on record for Bexar County (1969–2022),
66% found none.
Of the 3582 chloride tests on record for Bexar County (1908–2023),
0% found none, and half were below 25.3 mg/L.
Of the 5791 fluoride tests on record for Bexar County (1939–2023),
2% found none, and half were below 300 µg/L.
Of the 3269 iron tests on record for Bexar County (1911–2022),
54% found none.
Of the 2132 lead tests on record for Bexar County (1968–2022),
71% found none.
Of the 3090 manganese tests on record for Bexar County (1946–2022),
80% found none.
Of the 1575 nitrate tests on record for Bexar County (1939–2023),
4% found none, and half were below 1.57 mg/L.
Of the 3487 sulfate tests on record for Bexar County (1908–2023),
0% found none, and half were below 36 mg/L.
Of the 685 uranium tests on record for Bexar County (1996–2022),
48% found none, and half were below 0.134 µg/L.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Sulfate 3487 samples
Chloride 3582 samples
Iron 3269 samples
Radon 39 samples
Manganese 3090 samples
Fluoride 5791 samples
Nitrate 1575 samples
Lead 2132 samples
Arsenic 2601 samples
Nitrite 1116 samples
Uranium 685 samples
Hardness 3428 samples
E. coli 40 samples
Total Coliform 37 samples
Sodium 2462 samples
pH 3587 samples
No private-well PFAS data for Bexar County
We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Bexar 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 →
CDC Health Outcome Correlations
Where contaminants detected in Bexar 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 Bexar 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 Bexar County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Bexar 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 Bexar County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Bexar 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.