Arsenic in Central Florida Private Wells: Testing, Health Data, and Treatment

The U.S. Environmental Protection Agency sets a maximum contaminant level of 10 micrograms per liter (10 parts per billion) for arsenic in public drinking water systems under the Arsenic Rule, which took effect in January 2006 (epa.gov/dwreginfo/drinking-water-arsenic-rule-history). That standard does not apply to private well owners. The U.S. Geological Survey found that approximately 7 percent of domestic wells sampled nationally exceeded the 10 ppb threshold, and a 2017 USGS study estimated roughly 2.1 million people in the United States were using private well water with arsenic above the EPA limit. Florida sits in the Southeast region, where public data identifies moderate natural arsenic risk driven by phosphate-bearing geology and legacy agricultural pesticide use. No Florida law mandates ongoing arsenic testing for existing private well owners. This guide covers how arsenic gets into Central Florida well water, what the national and state data show, and which treatment technologies are certified effective for arsenic removal.

Why the EPA arsenic standard does not protect private well owners

The Safe Drinking Water Act and the EPA Arsenic Rule apply to community water systems and non-transient non-community systems that serve at least 25 people. Private residential wells fall entirely outside this regulatory scope. A private well owner whose water tests at 25 ppb arsenic faces no federal enforcement action, no mandatory notification, and no required treatment obligation under current law.

The 10 ppb standard itself reflects a regulatory compromise between health protection and treatment cost feasibility for public systems, not a no-risk threshold. The International Agency for Research on Cancer (IARC) classifies inorganic arsenic as a Group 1 carcinogen, meaning sufficient evidence of carcinogenicity in humans, as documented at iarc.who.int. The EPA's risk assessment found the 10 ppb MCL corresponds to an estimated cancer risk of roughly 1 in 1,000 at lifetime exposure. Arsenic has no taste, no odor, and no color at any concentration relevant to health. You cannot detect it without a laboratory test.

How arsenic gets into Central Florida well water

Arsenic enters groundwater through natural geological dissolution and through contamination from human activities.

Natural geological sources: Arsenic is bound in mineral compounds including arsenopyrite and arsenic-bearing iron oxides throughout Florida's geology. The state's phosphate deposits, concentrated in the Polk-Hillsborough-Manatee-Hardee corridor west and south of Orlando, contain naturally occurring arsenic associated with the phosphate mineral matrix. Groundwater moving through or adjacent to these formations can carry dissolved arsenic. The Florida Geological Survey documents arsenic enrichment in Florida soils at floridadep.gov/fgs.

Agricultural pesticide legacy: Florida used lead arsenate as a pesticide on citrus groves from roughly the 1890s through the 1950s, leaving residual arsenic in soils across large areas of Central Florida. The conversion of former citrus land to residential development in Orange, Lake, Polk, and Osceola counties has brought homes and private wells into contact with these legacy deposits. Arsenic from soil can leach into shallow groundwater under specific pH and oxidation conditions.

Depth does not equal safety: Under the low-oxygen conditions that often prevail in deeper confined aquifers, arsenic is more soluble and can occur at higher concentrations than in shallower oxygenated zones. Two wells on adjacent properties that penetrate different rock units can produce very different arsenic results. A neighbor's passing test tells you nothing about your own well.

What national and Florida data show about arsenic in domestic wells

What Florida law requires for arsenic testing of private wells

Florida's private well regulation under Chapter 62-532 FAC establishes permitting, construction, and initial completion testing requirements. New wells require a water quality sample before being placed in service, but arsenic is not uniformly required in the standard completion test battery for all private wells. The Florida Department of Health provides private well guidance at floridahealth.gov/environmental-health/drinking-water/private-wells/. The DOH recommends arsenic testing when buying a home with a private well, but this is advisory, not a legal mandate.

The Florida Department of Environmental Protection regulates arsenic in groundwater at the public system and remediation site level. FDEP's documentation of groundwater quality standards is at floridadep.gov/water/source-drinking-water/content/inorganic-contaminants. These standards apply to regulated sites and public supplies, not to private residential wells.

The practical result for Central Florida homeowners is the same as for bacteria, nitrate, and PFAS: private well owners bear sole responsibility for their water quality. No agency will test your water, report results to you, or require action if arsenic exceeds health thresholds.

How to test your Central Florida well for arsenic

Testing for arsenic requires a certified laboratory. Arsenic at health-relevant concentrations, in the single-digit parts-per-billion range, requires laboratory instrumentation. Home test strips typically have detection limits of 10 to 50 ppb and can give a passing result for water that contains arsenic at a health-relevant but below-strip-limit concentration.

The Florida Department of Health maintains a certified lab directory under the Environmental Laboratory Certification Program at floridahealth.gov/environmental-health/drinking-water/lab-certification/. A certified lab will provide sampling containers and instructions. Ask for their arsenic detection method and reporting limit. EPA Method 200.8 (ICP-MS) reliably detects arsenic below 1 ppb, well below the 10 ppb action level.

Consider ordering a broader inorganic chemistry panel rather than an arsenic-only test. The geological and hydrological conditions that produce elevated arsenic in Central Florida often correlate with elevated iron, manganese, fluoride, and barium. Testing multiple parameters at once gives a more complete picture at lower per-parameter cost than a series of single-parameter tests over time.

Treatment options that remove arsenic from well water

Three established treatment technologies address arsenic in residential wells:

Reverse osmosis (under-sink, point-of-use): RO systems certified under NSF/ANSI Standard 58 remove 95 to 99 percent of arsenic at the point of use. One important technical distinction applies: Arsenic V (Arsenate) is removed efficiently by RO membranes. Arsenic III (Arsenite), which is electrically neutral and more common in deep low-oxygen groundwater, passes more easily through membranes without a pre-oxidation step to convert it to Arsenic V first. If your well draws from a deep Floridan Aquifer zone, request arsenic speciation analysis from your lab before selecting a treatment system.

Activated alumina (whole-house or point-of-use): Activated alumina is a granular media certified under NSF/ANSI Standard 58 for arsenic reduction. It works by adsorption: arsenic binds to the media surface as water passes through. The media requires periodic replacement as capacity is exhausted. Activated alumina is effective for both Arsenic V and Arsenic III and is a practical option for whole-house arsenic reduction.

Ion exchange (point-of-use or whole-house): Strong-base anion exchange resins remove Arsenic V by exchanging it for chloride ions. Ion exchange has higher flow capacity than activated alumina but is less effective for Arsenic III without pre-oxidation. It is typically used in commercial or whole-house configurations where water demand is high.

Note that standard carbon filters, sediment filters, and water softeners do not remove arsenic. For Central Florida wells where iron and arsenic are both present, as is common in Marion, Alachua, and adjacent counties, iron treatment must typically come before an arsenic media system to prevent iron fouling of the arsenic-adsorbing media. See our iron and sulfur well water treatment guide for more on treatment sequencing.

What to do if your arsenic test comes back above 10 ppb

A result above 10 ppb requires action for drinking and cooking water specifically. Arsenic health risk is cumulative and dose-dependent; brief additional exposure while arranging treatment is less significant than years of untreated exposure. However, do not continue using the water for drinking or cooking without a treatment solution in place, particularly for children and pregnant women.

Use certified bottled water for drinking and cooking until a treatment system is installed. Boiling does not remove arsenic and concentrates it as water evaporates.

Get a follow-up test from the same certified lab to confirm the initial result. A confirmed result above 10 ppb establishes the baseline for treatment sizing. Request arsenic speciation analysis to determine whether Arsenic III or Arsenic V predominates, which affects treatment selection.

A point-of-use RO system certified under NSF/ANSI Standard 58 is typically the fastest and most cost-effective immediate solution for drinking and cooking water. Consult a water treatment professional about whole-house options based on your full water analysis and usage patterns.

For a complete water quality testing program for Central Florida wells, see our Florida well water testing guide. For data on other contaminants in the same series, see our guides on nitrate in Central Florida private wells, PFAS in Central Florida private wells, and coliform bacteria in Central Florida private wells. For whole-house treatment design, see whole-house well water filtration for Central Florida.