Full contaminant data, sample history, and sourcing for Webb County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
325 well testing events on record, covering
20 analytes.
Data spans 1965 to 2023.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. TX Avg
Radon
1
2013
100%
283% of limit
↑ 687% above
Chloride
37
1997–2013
100%
176% of limit
↑ 393% above
Sulfate
37
1997–2013
100%
140% of limit
↑ 389% above
Arsenic
203
1986–2017
22%
285% of limit
↑ 647% above
Iron
181
1944–2017
64%
43% of limit
↓ 72% below
Manganese
173
1966–2017
74%
13% of limit
↓ 79% below
Uranium
71
1988–2017
30%
73% of limit
↑ 373% above
Fluoride
271
1944–2017
98%
21% of limit
~ typical
Lead
164
1987–2017
4%
15% of limit
~ typical
HFPO-DA (GenX)
municipal
12
2023–2025
0%
—
—
Nitrate
72
1990–2013
39%
1% of limit
↓ 96% below
Nitrite
36
1997–2013
11%
1% of limit
~ typical
PFHxS
municipal
12
2023–2025
0%
—
—
PFNA
municipal
12
2023–2025
0%
—
—
PFOA
municipal
12
2023–2025
0%
—
—
PFOS
municipal
12
2023–2025
0%
—
—
Sodium
37
1997–2013
100%
—
↑ 364% above
pH
37
1997–2013
100%
—
~ typical
PFBS
municipal
12
2023–2025
0%
—
—
Hardness
37
1997–2013
100%
—
↓ 94% 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 Webb County
Of the 203 arsenic tests on record for Webb County (1986–2017),
78% found none.
Of the 37 chloride tests on record for Webb County (1997–2013),
0% found none, and half were below 441 mg/L.
Of the 271 fluoride tests on record for Webb County (1944–2017),
2% found none, and half were below 830 µg/L.
Of the 181 iron tests on record for Webb County (1944–2017),
36% found none, and half were below 40 µg/L.
Of the 164 lead tests on record for Webb County (1987–2017),
96% found none.
Of the 173 manganese tests on record for Webb County (1966–2017),
26% found none, and half were below 3.7 µg/L.
Of the 72 nitrate tests on record for Webb County (1990–2013),
61% found none.
Of the 37 sulfate tests on record for Webb County (1997–2013),
0% found none, and half were below 349 mg/L.
Of the 71 uranium tests on record for Webb County (1988–2017),
70% found none.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Chloride 37 samples
Sulfate 37 samples
Arsenic 203 samples
Iron 181 samples
Manganese 173 samples
Uranium 71 samples
Fluoride 271 samples
Lead 164 samples
Nitrate 72 samples
Nitrite 36 samples
Sodium 37 samples
pH 37 samples
Hardness 37 samples
Limited data (<15 samples) — interpret with caution
Radon 1 sample
No private-well PFAS data for Webb County
We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Webb 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 Webb County
15Active public water systems
273,876Residents on public water
0%Households on private wells
Public water systems in Webb 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 Webb 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 Webb 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 Webb County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Webb 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 Webb County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Webb 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.