Full contaminant data, sample history, and sourcing for Monmouth County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
2129 well testing events on record, covering
20 analytes.
Data spans 1912 to 2025.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. NJ Avg
Manganese
288
1957–2023
97%
220% of limit
↓ 54% below
Iron
293
1926–2023
92%
1767% of limit
↑ 272% above
PFOA
municipal
188
2021–2025
43%
144% of limit
↓ 28% below
Lead
184
1977–2021
40%
3% of limit
↓ 88% below
PFOS
municipal
186
2021–2025
4%
115% of limit
↓ 32% below
Chloride
1991
1924–2023
100%
1% of limit
↓ 97% below
Sulfate
327
1926–2023
100%
4% of limit
↓ 74% below
Arsenic
138
1977–2023
51%
3% of limit
↓ 83% below
Nitrate
265
1953–2021
49%
1% of limit
↓ 95% below
Fluoride
272
1953–2023
63%
3% of limit
↓ 43% below
HFPO-DA (GenX)
municipal
188
2021–2025
0%
—
—
Nitrite
206
1973–2021
15%
0% of limit
↓ 76% below
PFHxS
municipal
187
2021–2025
2%
26% of limit
↓ 41% below
PFNA
municipal
188
2021–2025
1%
22% of limit
↓ 51% below
Radon
6
2001–2012
100%
15% of limit
↓ 65% below
Uranium
12
2008–2012
67%
0% of limit
↓ 99% below
Hardness
306
1926–2023
100%
—
↓ 66% below
PFBS
municipal
185
2021–2025
3%
—
~ typical
pH
854
1953–2023
100%
—
~ typical
Sodium
384
1926–2023
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 NJ.
Compare your result with Monmouth County
Of the 138 arsenic tests on record for Monmouth County (1977–2023),
49% found none, and half were below 40 ng/L.
Of the 1991 chloride tests on record for Monmouth County (1924–2023),
0% found none, and half were below 2.4 mg/L.
Of the 272 fluoride tests on record for Monmouth County (1953–2023),
37% found none, and half were below 70 µg/L.
Of the 293 iron tests on record for Monmouth County (1926–2023),
8% found none, and half were below 4.1 mg/L.
Of the 184 lead tests on record for Monmouth County (1977–2021),
60% found none.
Of the 288 manganese tests on record for Monmouth County (1957–2023),
3% found none, and half were below 110 µg/L.
Of the 265 nitrate tests on record for Monmouth County (1953–2021),
51% found none.
Of the 327 sulfate tests on record for Monmouth County (1926–2023),
0% found none, and half were below 11 mg/L.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Manganese 288 samples
Iron 293 samples
PFOA 188 samples
Lead 184 samples
PFOS 186 samples
Chloride 1991 samples
Sulfate 327 samples
Arsenic 138 samples
Nitrate 265 samples
Fluoride 272 samples
HFPO-DA (GenX) 188 samples
Nitrite 206 samples
PFHxS 187 samples
PFNA 188 samples
Hardness 306 samples
PFBS 185 samples
pH 854 samples
Sodium 384 samples
Limited data (<15 samples) — interpret with caution
Radon 6 samples
Uranium 12 samples
Public vs. Private Water in Monmouth County
283Active public water systems
328,567Residents on public water
8%Households on private wells
Public water systems in Monmouth 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 Monmouth 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 Monmouth 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 Monmouth County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Monmouth 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 Monmouth County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Monmouth 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 NJ with at least one sample for that analyte.