Full contaminant data, sample history, and sourcing for Cobb County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
180 well testing events on record, covering
24 analytes.
Data spans 1958 to 2025.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. GA Avg
Manganese
69
1994–2006
96%
213% of limit
↑ 255% above
Iron
110
1994–2008
90%
87% of limit
↑ 111% above
Sulfate
122
1958–2008
96%
68% of limit
↑ 3233% above
Radon
12
1994–1995
100%
10% of limit
↓ 42% below
Lead
83
1994–2006
22%
17% of limit
↑ 1011% above
Arsenic
83
1994–2006
16%
5% of limit
~ typical
Fluoride
114
1958–2008
76%
8% of limit
↑ 50% above
PFNA
municipal
16
2023–2025
0%
—
—
PFOA
municipal
16
2023–2025
0%
—
—
Chloride
128
1958–2008
92%
1% of limit
↓ 45% below
Nitrite
97
1994–2008
18%
7% of limit
↑ 590% above
Uranium
12
1994–1995
0%
—
—
PFOS
municipal
16
2023–2025
0%
—
—
PFOA
municipal
16
2023–2025
0%
—
—
PFNA
municipal
16
2023–2025
0%
—
—
PFHxS
municipal
16
2023–2025
0%
—
—
Nitrite
97
1994–2008
18%
7% of limit
↑ 590% above
Nitrate
106
1958–2008
70%
8% of limit
↑ 21% above
HFPO-DA (GenX)
municipal
16
2023–2025
0%
—
—
Chloride
128
1958–2008
92%
1% of limit
↓ 45% below
Sodium
126
1958–2008
97%
—
↑ 117% above
pH
136
1958–2008
100%
—
~ typical
PFBS
municipal
16
2023–2025
50%
—
~ typical
Hardness
46
1958–2007
96%
—
~ typical
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 GA.
Compare your result with Cobb County
Of the 83 arsenic tests on record for Cobb County (1994–2006),
84% found none.
Of the 128 chloride tests on record for Cobb County (1958–2008),
8% found none, and half were below 2.4 mg/L.
Of the 114 fluoride tests on record for Cobb County (1958–2008),
24% found none, and half were below 200 µg/L.
Of the 110 iron tests on record for Cobb County (1994–2008),
10% found none, and half were below 220 µg/L.
Of the 83 lead tests on record for Cobb County (1994–2006),
78% found none.
Of the 69 manganese tests on record for Cobb County (1994–2006),
4% found none, and half were below 101 µg/L.
Of the 106 nitrate tests on record for Cobb County (1958–2008),
30% found none, and half were below 280 µg/L.
Of the 122 sulfate tests on record for Cobb County (1958–2008),
4% found none, and half were below 95 mg/L.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Manganese 69 samples
Iron 110 samples
Sulfate 122 samples
Lead 83 samples
Arsenic 83 samples
Fluoride 114 samples
Chloride 128 samples
Nitrite 97 samples
Nitrite 97 samples
Nitrate 106 samples
Chloride 128 samples
Sodium 126 samples
pH 136 samples
Hardness 46 samples
Limited data (<15 samples) — interpret with caution
Radon 12 samples
Uranium 12 samples
No private-well PFAS data for Cobb County
We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Cobb 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 Cobb County
5Active public water systems
803,382Residents on public water
12%Households on private wells
Public water systems in Cobb 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 Cobb 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 Cobb 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 Cobb County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Cobb 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 Cobb County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Cobb 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 GA with at least one sample for that analyte.