Full contaminant data, sample history, and sourcing for La Salle County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
388 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
Radon
2
2015
100%
81% of limit
↑ 124% above
Sulfate
124
1928–2016
100%
39% of limit
↑ 37% above
Chloride
126
1928–2016
100%
62% of limit
↑ 74% above
Iron
210
1913–2018
87%
33% of limit
↓ 78% below
Manganese
125
1938–2018
78%
21% of limit
↓ 67% below
Arsenic
108
1990–2018
10%
35% of limit
~ typical
Fluoride
340
1938–2018
99%
15% of limit
↓ 37% below
HFPO-DA (GenX)
municipal
7
2023
0%
—
—
Lead
110
1990–2018
5%
8% of limit
↓ 51% below
Nitrate
140
1928–2016
86%
4% of limit
↓ 82% below
Nitrite
6
2015–2016
0%
—
—
PFHxS
municipal
7
2023
0%
—
—
PFNA
municipal
7
2023
0%
—
—
PFOA
municipal
7
2023
0%
—
—
PFOS
municipal
7
2023
0%
—
—
Uranium
28
2010–2018
7%
1% of limit
↓ 95% below
Sodium
124
1928–2016
100%
—
↑ 164% above
pH
116
1938–2016
100%
—
~ typical
PFBS
municipal
7
2023
0%
—
—
Hardness
116
1928–2016
100%
—
↓ 92% 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 La Salle County
Of the 108 arsenic tests on record for La Salle County (1990–2018),
90% found none.
Of the 126 chloride tests on record for La Salle County (1928–2016),
0% found none, and half were below 156 mg/L.
Of the 340 fluoride tests on record for La Salle County (1938–2018),
1% found none, and half were below 600 µg/L.
Of the 210 iron tests on record for La Salle County (1913–2018),
13% found none, and half were below 80.3 µg/L.
Of the 110 lead tests on record for La Salle County (1990–2018),
95% found none.
Of the 125 manganese tests on record for La Salle County (1938–2018),
22% found none, and half were below 7.99 µg/L.
Of the 140 nitrate tests on record for La Salle County (1928–2016),
14% found none, and half were below 350 µg/L.
Of the 124 sulfate tests on record for La Salle County (1928–2016),
0% found none, and half were below 98 mg/L.
Of the 28 uranium tests on record for La Salle County (2010–2018),
93% found none.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Sulfate 124 samples
Chloride 126 samples
Iron 210 samples
Manganese 125 samples
Arsenic 108 samples
Fluoride 340 samples
Lead 110 samples
Nitrate 140 samples
Uranium 28 samples
Sodium 124 samples
pH 116 samples
Hardness 116 samples
Limited data (<15 samples) — interpret with caution
Radon 2 samples
Nitrite 6 samples
No private-well PFAS data for La Salle County
We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in La Salle 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 La Salle County
7Active public water systems
8,118Residents on public water
22%Households on private wells
Public water systems in La Salle 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 La Salle 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 La Salle 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 La Salle County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying La Salle 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 La Salle County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near La Salle 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.