Well water in Louisiana

In Louisiana, 22% of 1,119 tested well samples exceeded the EPA limit for arsenic (10 ug/L), based on public data from USGS Water Quality Portal and Louisiana LDEQ ambient ground water results (LDH Private Well Initiative).

1,119 individual samples from 718 wells, 1910 to 2021. Data refreshed September 9, 2026.

These are LDEQ monitoring wells sampled by aquifer on a rotation, so the shares describe the aquifer, not a survey of homeowners' wells. In that targeted sampling, 4% of 52 PFOS results in Louisiana were above the EPA limit of 4 ng/L. In that targeted sampling, 0% of 52 PFOA results in Louisiana were above the EPA limit of 4 ng/L.

What individual samples found

Each row summarizes every public sample for that contaminant inside Louisiana. Above limit means above the EPA maximum contaminant level; where EPA has no enforceable limit, the row shows a health guideline or nuisance level instead.

Contaminant	Samples	Detected	Above limit	Median	Highest	Limit
Arsenic 1972 to 2021	1,119	68%	22%	1	4,380	10 ug/L EPA limit
Lead 1972 to 2021	1,071	63%	19%	0	1,090	15 ug/L EPA limit
PFOS 2020 to 2021	52	13%	4%	0	41	4 ng/L EPA limit
Copper 1952 to 2020	341	90%	3%	0.162	6.31	1.3 mg/L EPA limit
Nitrate 1939 to 2021	198	53%	2%	0	31	10 mg/L EPA limit
Radium (226 + 228) 1977 to 2020	282	90%	1%	0.22	120	5 pCi/L EPA limit
Uranium 1977 to 2021	527	57%	0%	0.011	15.8	30 ug/L EPA limit
Fluoride 1939 to 2015	97	92%	0%	0.2	2	4 mg/L EPA limit
PFOA 2020 to 2021	52	6%	0%	0	3.7	4 ng/L EPA limit
Iron 1938 to 2020	934	100%	no limit	4,250	348,000	300 ug/L nuisance level
Manganese 1950 to 2021	745	99%	no limit	641	37,300	300 ug/L health guideline
Radon 1996 to 2014	189	99%	no limit	260	2,220	2,000 pCi/L health guideline
Sodium 1942 to 2018	99	100%	no limit	65	2,900	20 mg/L health guideline
Chloride 1910 to 2018	99	100%	no limit	45	3,800	250 mg/L nuisance level

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What this means

The contaminants most often above their limit here are arsenic (22% of 1,119 samples), lead (19% of 1,071 samples), and pfos (4% of 52 samples). A well next door can differ sharply from yours because bedrock fractures, well depth and plumbing all matter, so these rates describe the area, not your tap.

Iron, Manganese, and Chloride are widespread in local groundwater. They are mainly a staining and taste problem, but high manganese also carries a health advisory for infants.

What to test for in Louisiana

Arsenic22% of 1,119 local samples were above the limit.
Lead19% of 1,071 local samples were above the limit.
PFOS4% of 52 local samples were above the limit.
Copper3% of 341 local samples were above the limit.
Nitrate2% of 198 local samples were above the limit.
Radium (226 + 228)1% of 282 local samples were above the limit.
Coliform bacteriaRecommended for every private well, every year.

Treatment that fits the local profile

Arsenic: Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
Lead: Point-of-use reverse osmosis; Certified lead-removal carbon filter; Neutralizing filter to raise pH and stop leaching
PFOS: Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange
Copper: Neutralizing filter to raise pH; Point-of-use reverse osmosis
Nitrate: Point-of-use reverse osmosis; Anion exchange; Distillation

Common questions

Is there arsenic in well water in Louisiana?

Arsenic was detected in 68% of 1,119 public well samples in Louisiana, and 22% were above the EPA limit of 10 ug/L. Arsenic has no taste or smell; a lab test is the only way to know your level.

How high is radon in well water in Louisiana?

The median radon level across 189 public samples in Louisiana was 260 pCi/L, with a high of 2,220 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.

How often should I test a private well in Louisiana?

Test for bacteria and nitrate every year. Test once for arsenic, uranium, radon, fluoride, manganese and PFAS, then again every three to five years or after any change in taste, color, or plumbing.

Counties in Louisiana

Acadia3% lead
Allen42% arsenic
Ascension49 samples
Avoyelles32 samples
Beauregard33% arsenic
Bienville3% lead
Caddo21% arsenic
Calcasieu16% arsenic
East Baton Rouge9% arsenic
Lafayette4% arsenic
Morehouse33 samples
Rapides16% lead
Tangipahoa8% lead
Vernon33% lead

50 counties have fewer than 30 public samples and are included in the Louisiana totals above rather than shown separately: Assumption, Bossier, Caldwell, Cameron, Catahoula, Claiborne, Concordia, De Soto, East Carroll, East Feliciana, Evangeline, Franklin, Grant, Iberia, Iberville, Jackson, Jefferson, Jefferson Davis, Lafourche, LaSalle, Lincoln, Livingston, Madison, Natchitoches, Orleans, Ouachita, Plaquemines, Pointe Coupee, Red River, Richland, Sabine, St. Bernard, St. Charles, St. Helena, St. James, St. John the Baptist, St. Landry, St. Martin, St. Mary, St. Tammany, Tensas, Terrebonne, Union, Vermilion, Washington, Webster, West Baton Rouge, West Carroll, West Feliciana, Winn.

Sources

USGS Water Quality Portal: 3,619 samples in Louisiana. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
Louisiana LDEQ ambient ground water results (LDH Private Well Initiative): 2,186 samples in Louisiana. Ground water sample results from the LDEQ Ambient Ground Water Monitoring Program, published by the Louisiana Department of Health Private Well Initiative. Retrieved September 9, 2026.

Non-detects count as samples and are treated as zero when computing medians. Exactly at the limit counts as not above it. A sample belongs to the town containing the well's reported coordinates.