Data & Methodology — Miami-Dade County

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

Contaminant Data — All Analytes

23960 well testing events on record, covering 23 analytes. Data spans 1910 to 2021.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. FL Avg
PFOS municipal 56 2023–2025 91%
490% of limit ↑ 132% above
Iron 1799 1920–2024 97%
294% of limit ↑ 46% above
PFOA municipal 56 2023–2025 57%
189% of limit ↑ 32% above
Chloride 23260 1907–2025 100%
41% of limit ~ typical
Radon 20 1998–2016 100%
65% of limit ↑ 122% above
Arsenic 1113 1971–2024 83%
20% of limit ↑ 53% above
Sulfate 2094 1907–2025 98%
9% of limit ↓ 67% below
Manganese 1368 1948–2024 74%
40% of limit ↑ 51% above
Lead 1227 1971–2024 19%
1% of limit ↓ 58% below
Fluoride 1698 1923–2025 99%
5% of limit ↓ 30% below
Nitrate 2159 1907–2016 85%
0% of limit ↓ 100% below
Nitrite 1925 1969–2016 51%
1% of limit ~ typical
HFPO-DA (GenX) municipal 56 2023–2025 0%
— —
PFNA municipal 56 2023–2025 7%
52% of limit ~ typical
Uranium 200 1973–2016 97%
2% of limit ↑ 122% above
PFHxS municipal 56 2023–2025 34%
43% of limit ~ typical
E. coli 64 2016–2025 75%
— ~ typical
Fecal Coliform 47 1971–2021 52%
— ~ typical
PFBS municipal 56 2023–2025 86%
— ~ typical
Sodium 1830 1907–2025 100%
— ↓ 62% below
pH 2453 1940–2025 100%
— ~ typical
Hardness 1947 1907–2023 100%
— ~ typical
Total Coliform 111 1971–2025 67%
— ~ 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 FL.

Compare your result with Miami-Dade County

Of the 1113 arsenic tests on record for Miami-Dade County (1971–2024), 17% found none, and half were below 1 µg/L.

Of the 23260 chloride tests on record for Miami-Dade County (1907–2025), 0% found none, and half were below 103 mg/L.

Of the 1698 fluoride tests on record for Miami-Dade County (1923–2025), 1% found none, and half were below 200 µg/L.

Of the 1799 iron tests on record for Miami-Dade County (1920–2024), 3% found none, and half were below 820 µg/L.

Of the 1227 lead tests on record for Miami-Dade County (1971–2024), 81% found none.

Of the 1368 manganese tests on record for Miami-Dade County (1948–2024), 26% found none, and half were below 10 µg/L.

Of the 2159 nitrate tests on record for Miami-Dade County (1907–2016), 15% found none.

Of the 2094 sulfate tests on record for Miami-Dade County (1907–2025), 2% found none, and half were below 22 mg/L.

Of the 200 uranium tests on record for Miami-Dade County (1973–2016), 3% found none, and half were below 0.605 µg/L.

Have a number from your lab? Enter it to see where it falls. Nothing is sent anywhere.

Want the full picture for your well? Check all your results.

Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Iron 1799 samples
  • Chloride 23260 samples
  • Radon 20 samples
  • Arsenic 1113 samples
  • Sulfate 2094 samples
  • Manganese 1368 samples
  • Lead 1227 samples
  • Fluoride 1698 samples
  • Nitrate 2159 samples
  • Nitrite 1925 samples
  • Uranium 200 samples
  • E. coli 64 samples
  • Fecal Coliform 47 samples
  • Sodium 1830 samples
  • pH 2453 samples
  • Hardness 1947 samples
  • Total Coliform 111 samples

No private-well PFAS data for Miami-Dade County

We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Miami-Dade 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 Miami-Dade County

172 Active public water systems
3,326,006 Residents on public water
2% Households on private wells

Public water systems in Miami-Dade 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 Miami-Dade 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 Miami-Dade County Prevalence FL Average Source Year
Arsenic Cancer prevalence 5.5% 6.8% 2020
Arsenic Kidney disease rate 3.2% 3.4% 2020
Lead Heart disease rate 5.8% 7.7% 2020

Source: CDC PLACES county-level estimates. Raw data: Download Miami-Dade 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 FL with at least one sample for that analyte.

Last updated: 2026-08-12

Full methodology →