Ohio Data Center Health Risks: diesel generators, fuel cells, and what residents are documenting

The Hilliard fuel-cell case: 1.45 million pounds of CO2 per day

The most documented health-impact case in Ohio is the proposed 73-megawatt Bloom Energy fuel-cell array for Amazon's Cosgray Road data-center campus in Hilliard, Franklin County. The Ohio EPA's air permit allows the array to emit up to 1.45 million pounds of carbon dioxide per day. The City of Hilliard's administrative-court appeal — using the city's own filings — equates that to the daily emissions of approximately 66,000 cars.

The fuel-cell array would be the largest of its kind in North America. It is sited adjacent to a residential subdivision and a Hilliard elementary school. Bloom Energy has filed an emissions report stating the project's CO2 concentrations “do not represent a cause for concern” and are “a fraction of typical ambient air concentrations.” The City of Hilliard has formally rejected that framing and requested an independent air-quality study, which Ohio EPA has not required as of April 2026.

Resident Annie Cannelongo's formal comments to the Ohio Power Siting Board capture the legal-procedural concern: “There is no real research about the safety of this kind of power plant, and it's sitting adjacent to a neighborhood and elementary school in Hilliard.”

The diesel generator math

Separately from the fuel cells, Amazon's Hilliard project also proposes 158 Tier 2 diesel backup generators. Per the air-permit application, these generators would emit carbon monoxide, nitrogen oxides (NOx), particulate matter (PM2.5), and sulfur dioxide (SO2) when running. Ohio EPA confirmed in February 2026 it would hold a public hearing on the diesel-generator permit after Hilliard residents submitted 160+ signed petition letters. As of April 2026, a hearing date has not been set.

Lima, Ohio, in Allen County, faces a parallel proposal: 115 diesel generators and 36 cooling towers sited between North Cole Street and West Bluelick Road. Ohio EPA hosted a public meeting in March 2026 where residents asked specifically how far emissions would carry from the diesel generators to nearby homes and schools. Ohio EPA's response: the company “was required to do NOx modeling for the emissions from the engines, and they did pass our lower standard.”

Why diesel generators matter even when they're “backup”

The standard industry response to generator-emissions concerns is that backup units run only during emergencies and brief monthly testing. The data does not support that as a clean signal. According to the World Resources Institute and 2025 EPA data:

• Diesel backup generators emit 200 to 600 times more nitrogen oxides per unit of electricity than natural-gas plants.
• Routine monthly testing for a 2-megawatt diesel generator releases 30–60 minutes of full-load emissions, equivalent to a small power plant operating in a residential neighborhood for an hour.
• Some Ohio data centers test in unison or in close succession, multiplying short-term peak emissions.
• Diesel particulate matter (PM2.5) penetrates deep into lung tissue and is linked to asthma, heart disease, and lung cancer with sustained exposure.

The Ohio EPA's air-permit framework for backup generators allows up to 100 hours of operation per year per generator without triggering “major source” classification. Across 158 Hilliard generators, that's a theoretical 15,800 hours of annual diesel operation — though actual operation is normally far below that ceiling.

The CEDS report: lung issues and premature death

In February 2026, the Community & Environmental Defense Services (CEDS) released a report concluding that data-center emissions could cause breathing issues and premature deaths for residents living nearby. The report recommends that states require health impact assessments before data centers are built — a requirement Ohio does not currently impose.

Researchers affiliated with the California Institute of Technology have separately modeled that data-center-associated air pollution could contribute to approximately 1,300 premature deaths annually nationwide by 2030, concentrated in communities adjacent to large facilities. Ohio's central and northeast clusters — Franklin, Licking, Trumbull, Mahoning, and Union County — are among the densest in the U.S. east of Virginia and so will absorb a disproportionate share of any health impact projected from this growth.

The PM2.5 problem specifically

Fine particulate matter at 2.5 microns (PM2.5) is the air pollutant most strongly associated with cardiovascular and respiratory disease, even at concentrations below current EPA standards. Diesel exhaust is a primary source. PM2.5 from monthly generator testing creates short-term spikes in residential air quality that may not register on long-term averages but can trigger asthma attacks, heart attacks in vulnerable populations, and acute respiratory distress.

The Ohio EPA's air permit process does not require operators to model short-term PM2.5 spikes during simultaneous generator testing. It models annual averages against the National Ambient Air Quality Standards (NAAQS). This is a regulatory gap that residents in Hilliard, Lima, and other affected communities have repeatedly flagged in formal comments.

The fuel-cell question: cleaner than diesel, but not clean

Bloom Energy's fuel cells produce far less PM2.5 and NOx per kilowatt-hour than diesel generators — about 90% less, by Bloom's own figures. They run continuously rather than only during testing, however, so the cumulative emissions are different in shape. For Hilliard's 73-megawatt array operating roughly 24 hours a day, the year-round CO2 ceiling of 1.45M lbs/day translates to approximately 265,000 metric tons per year — comparable to a small natural-gas peaker plant.

Fuel cells also produce nitrogen oxides at lower rates than turbines, but at meaningfully higher rates than zero-emission alternatives like grid-supplied renewable power. The choice between fuel cells and diesel generators is not the only option; the choice between behind-the-meter generation and grid-supplied power is the underlying question. HB 15's authorization of behind-the-meter generation is what made the Hilliard fuel-cell plan possible without going through the Ohio Power Siting Board's full review.

What Ohio EPA permits actually require

Ohio's air-permit framework for data centers covers:

• National Ambient Air Quality Standards (NAAQS) compliance modeling — modeling that emissions will not cause exceedances of federal pollutant limits at the property line over annual averages.
• Maximum hours of operation per generator per year — typically 100 hours.
• Tier 2 / Tier 4 diesel engine standards — engines must meet specific particulate and NOx emissions per kilowatt-hour at the engine.
• Public notice and comment — for major air permits, Ohio EPA must publish notice and accept comments. For minor permits, no public notice is required.

What the framework does not require:

• Health impact assessment on nearby populations, schools, hospitals.
• Cumulative impact modeling when multiple data centers cluster in the same airshed.
• Short-term peak modeling for simultaneous generator testing.
• Mandatory community-engagement process outside of formal comment.
• Independent monitoring by anyone other than the operator.

What residents can do

The single most important action: file formal written comments during the air permit public notice period. Comments become part of the permit record and are used by Ohio EPA staff in reviewing the permit. Residents have successfully forced Ohio EPA to hold public hearings (Hilliard, Lima) by submitting comment volume above 100 letters per project.

Beyond that:

• Document baseline air-quality conditions: PurpleAir or AirNow sensor data near the home, indoor PM2.5 baseline if you have respiratory concerns.
• Consult with an environmental medicine physician if you live within 1/2 mile of a proposed facility, particularly if there are existing asthma or cardiovascular concerns in the household.
• Connect with state representatives advocating health impact assessment requirements: Christine Cockley (Ohio House) and the sponsors of HB 710 (Demetriou, Workman) which proposes broader data-center incentive reforms.
• Sign the Ohio Constitutional Amendment to ban data centers above 25 megawatts — the cleanest available policy lever to prevent future Hilliard- and Lima-class facilities.

• NBC4 WCMH — Hilliard residents concerned by data center backup generator emissions (February 2026)
• Hometown Stations — Lima residents voice health concerns over proposed data center generators (March 2026)
• NBC4 WCMH — Report: Data centers' air pollution associated with lung issues, death (February 2026)
• Community & Environmental Defense Services (CEDS) — Data center health impact report (February 2026)
• World Resources Institute — From Energy Use to Air Quality: How Data Centers Affect US Communities
• Inside Climate News — Data Centers' Use of Diesel Generators (November 2025)
• Ohio EPA — Air permit application records (Cosgray Road, Lima)
• City of Hilliard — Administrative court appeal of Bloom Energy fuel cell air permit

• Data center water usage in Ohio — aquifer impact, OEPA NPDES rules, Marysville case
• Data centers and your Ohio electric bill — AEP’s 85% tariff, PJM capacity, BTCR riders
• Data center noise in Ohio — cooling-tower hum, generator testing, decibel limits
• Data centers and your property value — what GMU’s study found, what Mansfield residents say
• Is there a data center near my home? — how to check your Ohio county