Data & Methodology — Kern County

Full contaminant data, sample history, and sourcing for Kern County. For readers who want to go beyond the summary.

Contaminant Data — All Analytes

3408 well testing events on record, covering 27 analytes. Data spans 1917 to 2022.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. CA Avg
Arsenic 810 1964–2023 92%
60% of limit ↑ 54% above
Radon 96 1995–2018 100%
10% of limit ↓ 89% below
1,2,3-Trichloropropane 42 2006–2022 33%
220% of limit ↓ 85% below
Manganese 1296 1945–2023 70%
34% of limit ↓ 89% below
Sulfate 2940 1909–2023 100%
33% of limit ↑ 62% above
Uranium 376 1989–2023 94%
20% of limit ↑ 262% above
Chloride 3125 1909–2023 100%
24% of limit ~ typical
Iron 1942 1917–2023 78%
13% of limit ↓ 89% below
Boron 37 2006–2022 100%
16% of limit ~ typical
PFOS municipal 462 2022–2025 6%
130% of limit ↓ 38% below
Nitrate 2181 1917–2023 92%
11% of limit ↓ 53% below
Fluoride 2560 1946–2023 98%
18% of limit ↑ 152% above
PFOA municipal 462 2022–2025 2%
164% of limit ~ typical
Nitrite 670 1951–2023 30%
1% of limit ~ typical
Lead 449 1968–2023 21%
2% of limit ↓ 79% below
PFNA municipal 462 2022–2025 0%
47% of limit ~ typical
PFHxS municipal 462 2022–2025 3%
51% of limit ~ typical
Chromium (total) 39 2006–2022 59%
3% of limit ~ typical
HFPO-DA (GenX) municipal 461 2022–2025 0%
— —
Perchlorate 41 2006–2022 49%
6% of limit ~ typical
Tds 37 2006–2022 100%
— ~ typical
E. coli 29 2002–2022 2%
— ~ typical
PFBS municipal 462 2022–2025 1%
— ~ typical
Total Coliform 29 2002–2022 10%
— ~ typical
pH 3036 1941–2023 100%
— ~ typical
Hardness 3072 1909–2023 100%
— ↓ 37% below
Sodium 2931 1909–2023 100%
— ↑ 21% above

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 CA.

Compare your result with Kern County

Of the 810 arsenic tests on record for Kern County (1964–2023), 8% found none, and half were below 5 µg/L.

Of the 3125 chloride tests on record for Kern County (1909–2023), 0% found none, and half were below 60 mg/L.

Of the 39 chromium (total) tests on record for Kern County (2006–2022), 41% found none, and half were below 0.8 µg/L.

Of the 2560 fluoride tests on record for Kern County (1946–2023), 2% found none, and half were below 700 µg/L.

Of the 1942 iron tests on record for Kern County (1917–2023), 22% found none, and half were below 20 µg/L.

Of the 449 lead tests on record for Kern County (1968–2023), 79% found none.

Of the 1296 manganese tests on record for Kern County (1945–2023), 30% found none, and half were below 2 µg/L.

Of the 2181 nitrate tests on record for Kern County (1917–2023), 8% found none, and half were below 904 µg/L.

Of the 32 pfoa tests on record for Kern County (2022), 97% found none.

Of the 32 pfos tests on record for Kern County (2022), 94% found none.

Of the 2940 sulfate tests on record for Kern County (1909–2023), 0% found none, and half were below 82 mg/L.

Of the 37 tds tests on record for Kern County (2006–2022), 0% found none, and half were below 405 mg/L.

Of the 376 uranium tests on record for Kern County (1989–2023), 6% found none, and half were below 4.93 µg/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Arsenic 810 samples
  • Radon 96 samples
  • 1,2,3-Trichloropropane 42 samples
  • Manganese 1296 samples
  • Sulfate 2940 samples
  • Uranium 376 samples
  • Chloride 3125 samples
  • Iron 1942 samples
  • Boron 37 samples
  • PFOS 462 samples
  • Nitrate 2181 samples
  • Fluoride 2560 samples
  • PFOA 462 samples
  • Nitrite 670 samples
  • Lead 449 samples
  • PFNA 462 samples
  • PFHxS 462 samples
  • Chromium (total) 39 samples
  • HFPO-DA (GenX) 461 samples
  • Perchlorate 41 samples
  • Tds 37 samples
  • E. coli 29 samples
  • PFBS 462 samples
  • Total Coliform 29 samples
  • pH 3036 samples
  • Hardness 3072 samples
  • Sodium 2931 samples

Public vs. Private Water in Kern County

338 Active public water systems
1,031,744 Residents on public water
3% Households on private wells

Public water systems in Kern 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 Kern 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.

Contaminant Associated Condition Kern County Prevalence CA Average Source Year
Arsenic Cancer prevalence 5.1% 6.2% 2020
Arsenic Kidney disease rate 3.2% 3.0% 2020
Lead Heart disease rate 6.6% 6.3% 2020

Source: CDC PLACES county-level estimates. Raw data: Download Kern County CDC PLACES data →

Data Sources

This report aggregates data from the following public databases:

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 CA with at least one sample for that analyte.

Last updated: 2026-09-10

Full methodology →