Full contaminant data, sample history, and sourcing for Atascosa County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
1003 well testing events on record, covering
20 analytes.
Data spans 1928 to 2023.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. TX Avg
Iron
607
1928–2018
94%
167% of limit
~ typical
Manganese
315
1953–2018
84%
86% of limit
↑ 34% above
Chloride
241
1928–2017
99%
19% of limit
↓ 47% below
Sulfate
240
1928–2017
100%
17% of limit
↓ 40% below
Arsenic
259
1981–2018
12%
2% of limit
↓ 95% below
Fluoride
824
1936–2018
96%
10% of limit
↓ 58% below
HFPO-DA (GenX)
municipal
34
2024–2025
0%
—
—
Lead
258
1981–2018
7%
1% of limit
↓ 96% below
Nitrate
189
1928–2015
80%
3% of limit
↓ 87% below
Nitrite
17
1981–2015
6%
2% of limit
↑ 94% above
PFHxS
municipal
34
2024–2025
0%
—
—
PFNA
municipal
34
2024–2025
0%
—
—
PFOA
municipal
34
2024–2025
0%
—
—
PFOS
municipal
34
2024–2025
0%
—
—
Radon
4
2008–2015
100%
12% of limit
↓ 68% below
Uranium
97
2004–2018
5%
0% of limit
↓ 98% below
Sodium
186
1928–2017
100%
—
↓ 68% below
pH
171
1938–2017
100%
—
~ typical
PFBS
municipal
34
2024–2025
0%
—
—
Hardness
178
1928–2017
100%
—
↓ 28% below
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 Atascosa County
Of the 259 arsenic tests on record for Atascosa County (1981–2018),
88% found none.
Of the 241 chloride tests on record for Atascosa County (1928–2017),
1% found none, and half were below 47 mg/L.
Of the 824 fluoride tests on record for Atascosa County (1936–2018),
4% found none, and half were below 400 µg/L.
Of the 607 iron tests on record for Atascosa County (1928–2018),
6% found none, and half were below 425 µg/L.
Of the 258 lead tests on record for Atascosa County (1981–2018),
93% found none.
Of the 315 manganese tests on record for Atascosa County (1953–2018),
16% found none, and half were below 26.5 µg/L.
Of the 189 nitrate tests on record for Atascosa County (1928–2015),
20% found none, and half were below 30 µg/L.
Of the 240 sulfate tests on record for Atascosa County (1928–2017),
0% found none, and half were below 42.9 mg/L.
Of the 97 uranium tests on record for Atascosa County (2004–2018),
95% found none.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Iron 607 samples
Manganese 315 samples
Chloride 241 samples
Sulfate 240 samples
Arsenic 259 samples
Fluoride 824 samples
Lead 258 samples
Nitrate 189 samples
Nitrite 17 samples
Uranium 97 samples
Sodium 186 samples
pH 171 samples
Hardness 178 samples
Limited data (<15 samples) — interpret with caution
Radon 4 samples
No private-well PFAS data for Atascosa County
We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Atascosa 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 Atascosa 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 Atascosa 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 Atascosa County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Atascosa 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 Atascosa County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Atascosa 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.