Ohio Private Well Water Quality 2026

Ohio’s PFAS Problem: The DuPont Legacy and Beyond

Ohio’s PFAS contamination story is one of the most significant in US history. Little Hocking, a small community in Washington County, sits directly across the Ohio River from the Chemours Washington Works plant — formerly owned by DuPont — which discharged PFOA into the river for decades starting in 1951. Testing by Ohio EPA found an untreated groundwater sample from the Little Hocking Water Association containing 2,500 parts per trillion (ppt) of PFOA — 625 times the current federal limit of 4 ppt. Internal DuPont records later revealed the company had known about contamination of local wells since at least 1984 and had not disclosed it.

The situation became the subject of the 2019 film Dark Waters, and led to a landmark class-action lawsuit settlement of $671 million covering some 3,500 individual cases. Under EPA Safe Drinking Water Act orders, Chemours and DuPont sampled 835 residential drinking water wells in the affected area by September 2023, finding 350 wells with concentrations above 70 ppt — all of which were offered alternate drinking water or treatment. The remaining 485 wells had PFOA below 70 ppt, though all now exceed the 2024 federal limit of 4 ppt.

The Chemours plant continues to operate, and PFAS discharges into the Ohio River are ongoing. The Little Hocking Water Association’s well field has seen a fivefold increase in GenX (a next-generation PFAS compound) concentrations in recent years. As of 2024–2025, the plant’s discharges were still being detected at water intakes as far downstream as Cincinnati and Louisville.

Beyond Little Hocking, Ohio’s PFAS contamination picture includes:

• Butler Township, Montgomery County (Dayton area) — after PFAS was detected at Aullwood Farm near Dayton International Airport at some of the highest levels recorded in the state, Butler Township and Montgomery County partnered to test 155 private wells in the area. PFAS was detected in 68 of those wells. Approximately 18,000 licensed private wells exist in Montgomery County, many pre-dating the 1980s licensing requirement. No broader county-wide testing programme is currently in place.
• Wright-Patterson Air Force Base (Greene County) — the third-highest recorded PFAS levels in Ohio per state EPA records, from decades of AFFF firefighting foam use. The base is in Bath Township, Greene County. As of 2024, the base has spent over $61 million on PFAS response and installed 291 monitoring wells, but no private well testing programme for surrounding residents is currently in place.
• Industrial Ohio River corridor — paper mills, metal plating operations, textile manufacturers, and chrome plating facilities along the Ohio River have been identified by the EWG as PFAS sources affecting groundwater across multiple counties.
• Statewide — 106 public water systems — Ohio EPA testing found detectable PFAS levels in 106 public water systems across the state. Private wells in the same areas face the same groundwater, with zero monitoring required.

Ohio has no state-level PFAS limits for private wells. The federal 4 ppt limit for PFOA and PFOS applies only to public water systems, with a compliance deadline of 2031. Private well owners receive no notification, no monitoring, and no enforcement protection.

Arsenic in Ohio Well Water

Arsenic contamination in Ohio private wells is a serious and well-documented problem, particularly in the southwestern part of the state. A USGS study of domestic wells in southwestern Ohio found that 37% of tested wells exceeded the federal MCL of 10 micrograms per litre (10 ppb). The Ohio Water Resources Center at Ohio State University is currently running research specifically addressing arsenic contamination in Ohio private wells, noting it as a significant health risk for the state’s well users.

Arsenic risk is highest in southwestern Ohio and in areas underlain by Paleozoic bedrock east of Columbus. The Ohio Department of Health recommends that all private well owners test for arsenic as part of routine water quality monitoring. As with PFAS, arsenic is colourless and tasteless — it cannot be detected without laboratory testing. Long-term exposure is associated with kidney cancer, bladder cancer, skin cancer, and cardiovascular disease.

Nitrate and Bacteria Risks

In Ohio’s agricultural counties — particularly in the northwest and central regions — nitrate contamination from fertiliser runoff is a documented risk in shallow wells. Ohio is one of the most agriculturally intensive states in the Midwest, and nitrate levels can spike seasonally following heavy rainfall and crop application cycles. High nitrate levels pose a particular danger to infants under six months of age, causing potentially fatal methemoglobinaemia (blue baby syndrome).

Coliform bacteria and E. coli contamination occur when wellheads are improperly sealed, flood water infiltrates, or septic systems are located too close to well casings. Ohio law mandates testing for total coliform, E. coli, and nitrates for all newly drilled wells at the time of installation — but there is no requirement for ongoing routine testing after that initial inspection. Ohio’s only enforceable health standard for private wells is for bacteria: there is no legal MCL for arsenic, PFAS, nitrate, or any other chemical contaminant in private well water under state law.

Regulatory Situation for Ohio Well Owners

Private residential wells in Ohio are regulated by the Ohio Department of Health (ODH) under Ohio Revised Code 3701.344–3701.347 and Ohio Administrative Code Chapter 3701-28. However, this regulation covers siting, construction permitting, and new well installation only. ODH has no authority to mandate water quality testing of existing wells, no system for notifying well owners when nearby contamination is identified, and no enforcement mechanism for chemical contaminants in private well water.

The Ohio EPA regulates public water systems only. For PFAS specifically, Ohio has not set its own state MCLs — it relies entirely on the federal limits of 4 ppt for PFOA and PFOS, which apply to public systems only. The original compliance deadline was 2029; in May 2025 the EPA announced its intent to extend this to 2031, with a proposed rule expected to be finalised in spring 2026. Either way, those limits apply to public water systems only, not private wells. Ohio well owners are entirely responsible for testing and treating their own water, with no state financial assistance programme currently available specifically for PFAS testing.

For context on Ohio’s municipal water quality, see our Ohio tap water quality page, our Columbus water quality page, or our Cleveland water quality page. You can also use our live boil water notice tracker for active advisories across Ohio.

Known High-Risk Areas in Ohio

If you live near any of the following locations, well water testing is urgent — not precautionary.

How to Test Your Ohio Well Water — and What to Do Next

Ohio’s contamination profile means every private well owner in the state should test their water — not just those near known sites. PFAS is colourless, odourless and tasteless. Arsenic is indistinguishable from clean water. The only way to know whether your well is safe is to test it.

Contact your local county health department to find an Ohio EPA-certified laboratory, or use the ODH Private Water Systems helpline at (614) 644-7558. For properties near the Ohio River, Wright-Patterson Air Force Base, or any of the high-risk areas listed above, PFAS testing should be treated as urgent. PFAS testing typically costs $400–$700 for a comprehensive panel — a cost worth paying given the health implications of long-term exposure.

For filter options, our well water filter guide covers reverse osmosis systems for PFAS and arsenic, UV disinfection for bacteria, and whole-house well systems for comprehensive treatment. You can also browse our full water filter solutions page or check your ZIP code for local water quality context.

For other Midwest well water risks, see our pages on Michigan wells and the private well water directory to find your state.