Full contaminant data, sample history, and sourcing for Brazoria County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
895 well testing events on record, covering
18 analytes.
Data spans 1931 to 2025.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. TX Avg
Manganese
247
1957–2021
90%
103% of limit
↑ 60% above
Chloride
457
1931–2015
100%
79% of limit
↑ 121% above
Iron
311
1951–2021
88%
72% of limit
↓ 53% below
Arsenic
180
1991–2021
38%
49% of limit
↑ 29% above
PFOS
municipal
136
2023–2025
1%
108% of limit
~ typical
Lead
177
1991–2021
7%
10% of limit
↓ 38% below
Sulfate
386
1931–2012
84%
4% of limit
↓ 86% below
Fluoride
467
1939–2021
100%
15% of limit
↓ 37% below
HFPO-DA (GenX)
municipal
136
2023–2025
0%
—
—
Nitrate
100
1933–2007
66%
1% of limit
↓ 95% below
PFHxS
municipal
136
2023–2025
4%
36% of limit
~ typical
PFNA
municipal
136
2023–2025
0%
—
—
PFOA
municipal
136
2023–2025
0%
—
—
Uranium
43
2010–2021
16%
16% of limit
~ typical
Sodium
229
1932–2012
100%
—
↑ 89% above
pH
213
1945–2015
100%
—
~ typical
PFBS
municipal
136
2023–2025
11%
—
~ typical
Hardness
328
1931–2012
100%
—
↓ 24% 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 Brazoria County
Of the 180 arsenic tests on record for Brazoria County (1991–2021),
62% found none.
Of the 457 chloride tests on record for Brazoria County (1931–2015),
0% found none, and half were below 198 mg/L.
Of the 467 fluoride tests on record for Brazoria County (1939–2021),
0% found none, and half were below 600 µg/L.
Of the 311 iron tests on record for Brazoria County (1951–2021),
12% found none, and half were below 187 µg/L.
Of the 177 lead tests on record for Brazoria County (1991–2021),
93% found none.
Of the 247 manganese tests on record for Brazoria County (1957–2021),
10% found none, and half were below 50 µg/L.
Of the 100 nitrate tests on record for Brazoria County (1933–2007),
34% found none, and half were below 45 µg/L.
Of the 386 sulfate tests on record for Brazoria County (1931–2012),
16% found none, and half were below 5 mg/L.
Of the 43 uranium tests on record for Brazoria County (2010–2021),
84% found none.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Manganese 247 samples
Chloride 457 samples
Iron 311 samples
Arsenic 180 samples
Lead 177 samples
Sulfate 386 samples
Fluoride 467 samples
Nitrate 100 samples
Uranium 43 samples
Sodium 229 samples
pH 213 samples
Hardness 328 samples
No private-well PFAS data for Brazoria County
We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Brazoria 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 Brazoria 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 Brazoria 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 Brazoria County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Brazoria 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 Brazoria County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Brazoria 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.