Full contaminant data, sample history, and sourcing for Montgomery County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
615 well testing events on record, covering
20 analytes.
Data spans 1931 to 2019.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. TX Avg
Radon
15
2007–2014
100%
113% of limit
↑ 215% above
Manganese
263
1966–2021
79%
39% of limit
↓ 40% below
Iron
281
1943–2021
78%
35% of limit
↓ 77% below
Chloride
155
1931–2017
100%
15% of limit
↓ 59% below
Nitrate
69
1985–2017
41%
2% of limit
↓ 93% below
Arsenic
214
1983–2021
27%
21% of limit
↓ 45% below
PFOA
municipal
233
2023–2025
0%
120% of limit
~ typical
Fluoride
412
1941–2021
97%
5% of limit
↓ 79% below
HFPO-DA (GenX)
municipal
233
2023–2025
0%
—
—
Lead
211
1983–2021
19%
8% of limit
↓ 53% below
Nitrite
30
1985–2017
3%
0% of limit
↓ 71% below
PFHxS
municipal
233
2023–2025
0%
—
—
PFNA
municipal
233
2023–2025
0%
—
—
PFOS
municipal
233
2023–2025
0%
—
—
Sulfate
149
1931–2017
98%
3% of limit
↓ 90% below
Uranium
79
2003–2021
34%
0% of limit
↓ 99% below
Sodium
95
1944–2017
100%
—
↓ 66% below
pH
148
1944–2017
100%
—
~ typical
PFBS
municipal
233
2023–2025
0%
—
~ typical
Hardness
143
1931–2017
100%
—
↓ 53% 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 Montgomery County
Of the 214 arsenic tests on record for Montgomery County (1983–2021),
73% found none.
Of the 155 chloride tests on record for Montgomery County (1931–2017),
0% found none, and half were below 37 mg/L.
Of the 412 fluoride tests on record for Montgomery County (1941–2021),
3% found none, and half were below 200 µg/L.
Of the 281 iron tests on record for Montgomery County (1943–2021),
22% found none, and half were below 84 µg/L.
Of the 211 lead tests on record for Montgomery County (1983–2021),
81% found none.
Of the 263 manganese tests on record for Montgomery County (1966–2021),
21% found none, and half were below 11.3 µg/L.
Of the 69 nitrate tests on record for Montgomery County (1985–2017),
59% found none.
Of the 149 sulfate tests on record for Montgomery County (1931–2017),
2% found none, and half were below 7.2 mg/L.
Of the 79 uranium tests on record for Montgomery County (2003–2021),
66% found none.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Radon 15 samples
Manganese 263 samples
Iron 281 samples
Chloride 155 samples
Nitrate 69 samples
Arsenic 214 samples
Fluoride 412 samples
Lead 211 samples
Nitrite 30 samples
Sulfate 149 samples
Uranium 79 samples
Sodium 95 samples
pH 148 samples
Hardness 143 samples
No private-well PFAS data for Montgomery County
We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Montgomery County.
PFAS has been detected in local public water systems (UCMR 5 data) — indicated by the "municipal" badge in the table above — but this does not directly indicate private well contamination.
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 Montgomery County
465Active public water systems
775,036Residents on public water
8%Households on private wells
Public water systems in Montgomery 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 Montgomery 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 Montgomery 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 Montgomery County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Montgomery 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 Montgomery County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Montgomery 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.