Full contaminant data, sample history, and sourcing for Brewster County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
382 well testing events on record, covering
19 analytes.
Data spans 1953 to 2024.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. TX Avg
Iron
198
1949–2020
45%
27% of limit
↓ 82% below
Fluoride
365
1949–2020
99%
40% of limit
↑ 67% above
Manganese
189
1949–2020
41%
12% of limit
↓ 81% below
Arsenic
152
1972–2020
24%
33% of limit
~ typical
Lead
149
1972–2020
15%
13% of limit
↓ 25% below
Chloride
29
1953–2010
100%
3% of limit
↓ 93% below
HFPO-DA (GenX)
municipal
4
2025
0%
—
—
Nitrate
41
1986–2010
85%
12% of limit
↓ 48% below
Nitrite
10
1986–2010
10%
15% of limit
↑ 1356% above
PFHxS
municipal
4
2025
0%
—
—
PFNA
municipal
4
2025
0%
—
—
PFOA
municipal
4
2025
0%
—
—
PFOS
municipal
4
2025
0%
—
—
Sulfate
27
1953–2010
100%
16% of limit
↓ 43% below
Uranium
54
1978–2020
91%
13% of limit
~ typical
Sodium
25
1953–2010
100%
—
↓ 75% below
pH
32
1953–2010
100%
—
~ typical
PFBS
municipal
4
2025
0%
—
—
Hardness
29
1953–2010
100%
—
↓ 58% 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 Brewster County
Of the 152 arsenic tests on record for Brewster County (1972–2020),
76% found none.
Of the 29 chloride tests on record for Brewster County (1953–2010),
0% found none, and half were below 6.5 mg/L.
Of the 365 fluoride tests on record for Brewster County (1949–2020),
1% found none, and half were below 1.56 mg/L.
Of the 198 iron tests on record for Brewster County (1949–2020),
55% found none.
Of the 149 lead tests on record for Brewster County (1972–2020),
85% found none.
Of the 189 manganese tests on record for Brewster County (1949–2020),
59% found none.
Of the 41 nitrate tests on record for Brewster County (1986–2010),
15% found none, and half were below 800 µg/L.
Of the 27 sulfate tests on record for Brewster County (1953–2010),
0% found none, and half were below 41 mg/L.
Of the 54 uranium tests on record for Brewster County (1978–2020),
9% found none, and half were below 3.35 µg/L.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Iron 198 samples
Fluoride 365 samples
Manganese 189 samples
Arsenic 152 samples
Lead 149 samples
Chloride 29 samples
Nitrate 41 samples
Sulfate 27 samples
Uranium 54 samples
Sodium 25 samples
pH 32 samples
Hardness 29 samples
Limited data (<15 samples) — interpret with caution
Nitrite 10 samples
No private-well PFAS data for Brewster County
We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Brewster 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 Brewster 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 Brewster 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 Brewster County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Brewster 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 Brewster County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Brewster 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.