Nitrate In Drinking Water In Ohio
What residents of Ohio need to know about nitrate in drinking water — including how it enters water, which utilities have documented violations, and what steps to take.
Source: EPA SDWIS, Ohio Environmental Protection Agency (Ohio EPA), CDC · Last reviewed: 2025-01-01
Quick Answer
Is nitrate in drinking water a real concern in Ohio?
Yes — Ohio's Maumee River watershed delivers nutrient-rich agricultural runoff to Lake Erie, and Toledo's water supply — serving more than 500,000 people — draws from western Lake Erie.
Is this mostly a public-water issue, a private-well issue, or both?
Both — Toledo's public supply from Lake Erie has documented seasonal nutrient concerns; private well users in Ohio's agricultural counties are also at risk.
What is the main reason residents should care?
Ohio's agricultural heartland drains into the Maumee River and ultimately western Lake Erie. Toledo (Lake Erie Water Treatment Plant) serves over 500,000 people and monitors nitrate. Harmful algal blooms in western Lake Erie, driven partly by agricultural nutrient pollution, are a documented seasonal concern.
Key Facts
| EPA Nitrate MCL | 10 mg/L as N |
| Maumee watershed | Largest watershed draining to Great Lakes; delivers agricultural nitrate to Lake Erie |
| Toledo water supply | Draws from western Lake Erie; monitors nitrate and algal toxins |
| Private well risk | Agricultural northwest Ohio counties — test annually for nitrate |
| State oversight | Ohio Environmental Protection Agency (Ohio EPA) |
Why This Matters in Ohio
Ohio is a major agricultural state with significant corn, soybean, and dairy production. The Maumee River watershed — the largest watershed draining into the Great Lakes — delivers nutrient-rich water from Ohio farmland to western Lake Erie. Toledo draws drinking water from the lake and monitors nitrate and other nutrients. Harmful algal blooms (HABs) in western Lake Erie, driven partly by phosphorus and nitrogen from agricultural sources, have caused water quality alerts — including the 2014 Toledo water advisory (related to HAB toxins, not nitrate directly, but demonstrating the nutrient pollution issue). Ohio EPA monitors public water systems for nitrate compliance.
Historical Context
In August 2014, Toledo issued a 'do not use' advisory for its water supply after a harmful algal bloom on Lake Erie produced microcystin toxins (not nitrate, but illustrating the nutrient pollution challenge). Ohio's agricultural nutrient loading into Lake Erie remains an active environmental and public health concern.
Critical — Infants Under 6 Months
Do not use tap water that exceeds 10 mg/L nitrate-nitrogen to prepare infant formula or feed infants under six months. Boiling will concentrate nitrate — do not boil. Use bottled water or a certified reverse osmosis system (NSF/ANSI 58) until the issue is resolved.
Ohio Utilities With Nitrate Violation Records
The utilities listed below have at least one nitrate violation on record in EPA's SDWIS database. Violations may be open or resolved — see individual utility pages for current status and risk level.
City of Toledo
Toledo · 360,000 served
Dayton Public Water System
Dayton · 141,407 served
Clermont Public Water System
Ohio · 133,059 served
Youngstown City Pws
Youngstown · 130,530 served
Butler Co. Water District 2 Pws
Ohio · 116,572 served
Canton Public Water System
Canton · 107,113 served
Aqua Ohio - Massillon Pws
Ohio · 95,636 served
Warren County
Ohio · 81,975 served
Lake County West Water Subdistrict
Ohio · 78,379 served
Lorain City Pws
Lorain · 64,152 served
How Nitrate Gets Into Drinking Water
Agricultural fertilizer and manure runoff
Nitrogen-based fertilizers and animal waste applied to Ohio cropland can leach into groundwater or run off into surface water supplies. This is the dominant nitrate pathway in most agricultural regions.
Septic system effluent
Failing or poorly sited septic systems release nitrogen-rich wastewater near drinking water wells. Rural areas with high well density and aging septic infrastructure face elevated risk.
Concentrated animal feeding operations (CAFOs)
Large livestock facilities generate significant waste. Lagoon leaks and overapplication of manure to nearby fields can create localized nitrate hotspots in groundwater.
Natural geological deposits
In some regions, naturally occurring nitrogen compounds in soil and bedrock contribute background nitrate levels to groundwater independent of agricultural activity.
Who Should Pay Closest Attention
Private well users in northwest Ohio's agricultural counties (Defiance, Henry, Putnam, Fulton) should test annually for nitrate. Families with formula-fed infants using well water in agricultural areas face the highest health risk.
Households with infants under six months
Pregnant residents
Private well owners in agricultural areas
Households near livestock operations or CAFOs
Rural residents on shallow groundwater wells
Households with older or failing septic systems nearby
How to Check Your Situation in Ohio
- 1
Identify your water utility. Use the ZIP lookup below or browse the Ohio utility directory on this site.
- 2
Read your utility's page on this site to see its current risk level and any open nitrate violations.
- 3
Review your utility's most recent Consumer Confidence Report (CCR) — mailed annually or available on the utility's website. It must disclose any MCL exceedances.
- 4
If you are on a private well, arrange testing at a Ohio Environmental Protection Agency (Ohio EPA)-certified lab. Your state health department maintains a list of certified labs. Annual testing is recommended in agricultural areas.
- 5
If you have an infant under six months, use bottled water or a certified RO system (NSF/ANSI 58) immediately as a precautionary measure — do not wait for test results if you are in a high-risk area.
- 6
If your utility issues a nitrate exceedance notice, follow their guidance and do not use tap water for infants until the issue is resolved.
Treatment Options
Carbon filters and boiling do not remove nitrate. Only the options below are effective.
NSF/ANSI Standard 58 — Reverse Osmosis
RO systems certified to NSF/ANSI 58 reduce nitrate by 85–95% at the point of use. Under-sink installation required. The most practical residential option for nitrate concerns.
Distillation
Distillation units effectively remove nitrate along with most other dissolved contaminants. Suitable for drinking and cooking water — not whole-house use.
Anion Exchange
Ion exchange systems designed for nitrate removal exchange nitrate ions for chloride on a resin bed. Effective as a point-of-entry system; requires periodic regeneration and monitoring.
Carbon filters do NOT remove nitrate
Standard pitcher filters, faucet filters, and under-sink carbon units — including those certified NSF/ANSI 42 or 53 — do not remove nitrate. Do not use these for nitrate reduction.
Frequently Asked Questions
Related Pages
Nitrate — National Overview
All U.S. utilities with nitrate records
Ohio State Overview
All utilities and water quality data
Lead in Drinking Water
A separate but common concern
Reverse Osmosis Guide
Removes 85–95% of nitrate
Well Water Guide
Private well testing and safety
All Contaminants
Complete reference library
Data Sources & Provenance
All data on this page is sourced from official U.S. government or public datasets.
Find Your Utility
State Regulator
Ohio Environmental Protection Agency (Ohio EPA) ↗