Data & Methodology — Tulare County

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

Contaminant Data — All Analytes

785 well testing events on record, covering 27 analytes. Data spans 1949 to 2021.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. CA Avg
Nitrate 651 1949–2023 95%
46% of limit ↑ 95% above
Radon 31 1995–2014 100%
10% of limit ↓ 89% below
Uranium 244 1989–2023 99%
16% of limit ↑ 198% above
Arsenic 454 1986–2023 84%
18% of limit ↓ 55% below
PFOS municipal 284 2019–2025 7%
155% of limit ↓ 26% below
Manganese 472 1979–2023 64%
4% of limit ↓ 99% below
Chloride 675 1949–2023 100%
9% of limit ↓ 71% below
Perchlorate 124 2005–2020 70%
15% of limit ↑ 112% above
Sulfate 672 1949–2023 100%
10% of limit ↓ 53% below
1,2,3-Trichloropropane 277 2005–2023 3%
1000% of limit ↓ 30% below
Iron 493 1950–2023 42%
8% of limit ↓ 94% below
PFOA municipal 284 2019–2025 2%
208% of limit ↑ 25% above
Nitrite 457 1986–2023 25%
17% of limit ↑ 1280% above
Boron 276 2006–2023 93%
4% of limit ↓ 73% below
Fluoride 590 1956–2023 77%
5% of limit ↓ 28% below
HFPO-DA (GenX) municipal 282 2019–2025 0%
— —
Radium 226 13 2006 46%
15% of limit ↓ 21% below
PFNA municipal 284 2019–2025 0%
— —
Chromium (total) 276 2006–2023 39%
2% of limit ~ typical
Radium 228 13 2006 54%
38% of limit ~ typical
Lead 356 1986–2023 38%
4% of limit ↓ 56% below
PFHxS municipal 284 2019–2025 1%
34% of limit ↓ 40% below
Tds 276 2006–2023 100%
— ~ typical
Sodium 674 1949–2023 100%
— ↓ 44% below
Hardness 671 1949–2023 100%
— ↓ 43% below
PFBS municipal 284 2019–2025 3%
— ~ typical
pH 631 1950–2023 100%
— ~ 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 CA.

Compare your result with Tulare County

Of the 454 arsenic tests on record for Tulare County (1986–2023), 16% found none, and half were below 1.2 µg/L.

Of the 675 chloride tests on record for Tulare County (1949–2023), 0% found none, and half were below 22 mg/L.

Of the 276 chromium (total) tests on record for Tulare County (2006–2023), 61% found none.

Of the 590 fluoride tests on record for Tulare County (1956–2023), 23% found none, and half were below 130 µg/L.

Of the 493 iron tests on record for Tulare County (1950–2023), 58% found none.

Of the 356 lead tests on record for Tulare County (1986–2023), 62% found none.

Of the 472 manganese tests on record for Tulare County (1979–2023), 36% found none, and half were below 0.715 µg/L.

Of the 651 nitrate tests on record for Tulare County (1949–2023), 5% found none, and half were below 4.07 mg/L.

Of the 672 sulfate tests on record for Tulare County (1949–2023), 0% found none, and half were below 24 mg/L.

Of the 276 tds tests on record for Tulare County (2006–2023), 0% found none, and half were below 355 mg/L.

Of the 244 uranium tests on record for Tulare County (1989–2023), 1% found none, and half were below 4.69 µg/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Nitrate 651 samples
  • Radon 31 samples
  • Uranium 244 samples
  • Arsenic 454 samples
  • PFOS 284 samples
  • Manganese 472 samples
  • Chloride 675 samples
  • Perchlorate 124 samples
  • Sulfate 672 samples
  • 1,2,3-Trichloropropane 277 samples
  • Iron 493 samples
  • PFOA 284 samples
  • Nitrite 457 samples
  • Boron 276 samples
  • Fluoride 590 samples
  • HFPO-DA (GenX) 282 samples
  • PFNA 284 samples
  • Chromium (total) 276 samples
  • Lead 356 samples
  • PFHxS 284 samples
  • Tds 276 samples
  • Sodium 674 samples
  • Hardness 671 samples
  • PFBS 284 samples
  • pH 631 samples

Limited data (<15 samples) — interpret with caution

  • Radium 226 13 samples
  • Radium 228 13 samples

Public vs. Private Water in Tulare County

292 Active public water systems
467,882 Residents on public water
14% Households on private wells

Public water systems in Tulare 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 Tulare 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 Tulare County Prevalence CA Average Source Year
Arsenic Cancer prevalence 5.1% 6.2% 2020
Arsenic Kidney disease rate 3.4% 3.0% 2020

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