Full contaminant data, sample history, and sourcing for Medina County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
1380 well testing events on record, covering
22 analytes.
Data spans 1930 to 2022.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. TX Avg
Iron
928
1930–2022
40%
14% of limit
↓ 91% below
Sulfate
473
1930–2023
100%
7% of limit
↓ 75% below
Fluoride
1126
1930–2023
96%
5% of limit
↓ 79% below
Nitrate
473
1930–2023
90%
11% of limit
↓ 49% below
Manganese
859
1939–2022
18%
19% of limit
↓ 71% below
Chloride
478
1930–2023
100%
6% of limit
↓ 84% below
Lead
751
1972–2022
28%
9% of limit
↓ 44% below
Arsenic
853
1972–2022
23%
10% of limit
↓ 74% below
HFPO-DA (GenX)
municipal
30
2023–2025
0%
—
—
Nitrite
300
1975–2023
26%
1% of limit
~ typical
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
32
1996–2017
100%
6% of limit
↓ 82% below
Uranium
241
1996–2022
31%
2% of limit
↓ 84% below
Total Coliform
14
1970–2018
55%
—
~ typical
Sodium
371
1955–2023
100%
—
↓ 93% below
pH
472
1944–2024
100%
—
~ typical
PFBS
municipal
30
2023–2025
0%
—
—
Hardness
459
1930–2023
100%
—
~ typical
E. coli
14
2005–2018
50%
—
~ 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 Medina County
Of the 853 arsenic tests on record for Medina County (1972–2022),
77% found none.
Of the 478 chloride tests on record for Medina County (1930–2023),
0% found none, and half were below 13.9 mg/L.
Of the 1126 fluoride tests on record for Medina County (1930–2023),
4% found none, and half were below 200 µg/L.
Of the 928 iron tests on record for Medina County (1930–2022),
60% found none.
Of the 751 lead tests on record for Medina County (1972–2022),
72% found none.
Of the 859 manganese tests on record for Medina County (1939–2022),
82% found none.
Of the 473 nitrate tests on record for Medina County (1930–2023),
10% found none, and half were below 1.1 mg/L.
Of the 473 sulfate tests on record for Medina County (1930–2023),
0% found none, and half were below 17.7 mg/L.
Of the 241 uranium tests on record for Medina County (1996–2022),
69% found none.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Iron 928 samples
Sulfate 473 samples
Fluoride 1126 samples
Nitrate 473 samples
Manganese 859 samples
Chloride 478 samples
Lead 751 samples
Arsenic 853 samples
Nitrite 300 samples
Radon 32 samples
Uranium 241 samples
Sodium 371 samples
pH 472 samples
Hardness 459 samples
Limited data (<15 samples) — interpret with caution
Total Coliform 14 samples
E. coli 14 samples
No private-well PFAS data for Medina County
We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Medina 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 Medina County
33Active public water systems
77,970Residents on public water
10%Households on private wells
Public water systems in Medina 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 Medina 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 Medina 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 Medina County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Medina 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 Medina County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Medina 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.