Toledo chemical release continues as evacuation zone shrinks
AccuWeather meteorologists explain how a temperature inversion may have trapped hazardous chemicals near the ground as dense fog reduced visibility across northern Ohio. Officials lifted the broader shelter-in-place order as conditions improved following a chemical release and dense fog.
Video captures a driver’s view of fog and particles in the air in Toledo, Ohio, where a hazardous chemical release forced some residents to evacuate and others to shelter in place.
Dense fog blanketed Toledo, Ohio, overnight Tuesday into Wednesday as a hazardous chemical release forced evacuations and shelter-in-place orders.
The Toledo Fire & Rescue Department ordered residents within a 1-mile radius of a hazardous materials release near Progress Avenue to evacuate around 10:48 p.m. Tuesday, Oct. 20. Toledo Mayor Wade Kapszukiewicz said at a news conference Wednesday morning a sheriff's deputy was injured when he responded to the chemical release.
Early Wednesday, officials expanded precautions, ordering people within a 3-mile radius to shelter in place. Toledo Fire & Rescue reduced the evacuation area at 5 p.m. Wednesday, Oct. 21, and lifted evacuation and shelter-in-place orders beyond that boundary. Residents within the half-mile zone must remain evacuated.
The release involved equipment belonging to MC Tank Transport, which identified the chemical as glycidyl methacrylate, an industrial substance used in manufacturing plastics, paints and coatings.
Kapszukiewicz said efforts to stop the release had been unsuccessful, but the tank remained intact and its temperature was decreasing, with the release diminishing significantly.
Based on guidance from the Ohio and U.S. Environmental Protection Agencies and public safety officials, authorities determined that allowing the chemical to vent and the reaction to run its course was the safest approach. Further intervention could worsen the situation, the mayor said.
Dense fog blankets Toledo, Ohio within a mile radius of a chemical leak on Tuesday, Oct. 20, 2026. (Image: Justin Wagner)
Overnight Tuesday and Wednesday, dense fog and haze complicated the situation, making it difficult to distinguish naturally occurring fog from the chemical plume. Video showed visibility near zero within a mile of the hazmat situation.
How did the weather affect the chemical spill in Toledo?
The weather conditions to create a temperature inversion.
AccuWeather meteorologists say the same atmospheric conditions that allowed dense fog to develop may have prevented chemicals released into the air from dispersing.
"Fog was already forming across northern Ohio before the chemical spill occurred around 10:45 p.m. Tuesday. Winds were largely calm, and a temperature inversion likely helped trap moisture and pollutants near the ground," AccuWeather Senior Meteorologist Alex Sosnowski said.
A temperature inversion occurs when a layer of warmer air sits above cooler air near the surface, acting like a lid on the atmosphere.
This limits the vertical mixing of air, allowing fog to develop while potentially trapping airborne chemicals closer to the ground.
Instead of being carried away by stronger winds or dispersed through a well-mixed atmosphere, some of the chemical cloud may have remained concentrated in the lower atmosphere and spread across a broader area.
Could the chemical spill create a super fog?
"Airborne chemical particles can also act as condensation nuclei, providing surfaces for water vapor to condense into tiny fog droplets. Since fog was already developing across northern Ohio, particles released during the spill could have accelerated fog formation or made existing fog denser," AccuWeather Senior Meteorologist Adam Douty said.
However, meteorologists caution that the fog was not caused by the chemical release.
"However, widespread fog was expected to form even without the chemical spill, making it difficult to determine exactly how much the release contributed to the reduced visibility," Douty continued.
At Toledo Suburban Airport, just across the state line in Michigan, fog was reported as early as 9:35 p.m. Tuesday, more than an hour before the chemical release.
Visibility dropped to near zero by 11 p.m. and remained between zero and a quarter-mile overnight.
The chemical plume was also reported to have contributed to reduced visibility along Interstate 75 in northern Toledo.
The City of Toledo warned residents that the appearance of the air was not a reliable way to determine whether they were being exposed to hazardous chemicals.
What should Toledo residents do during the chemical release?
Residents within the half-mile evacuation zone must stay out of the area and follow emergency personnel’s instructions. Anyone outside the evacuation zone who notices an unusual odor should stay indoors, close windows and doors, and turn off ventilation that draws in outside air, according to city guidance.
Shoreland Elementary School remains open as a temporary shelter.
Exposure to the released chemical may cause irritation of the eyes, nose, mouth and skin, along with symptoms including headaches, dizziness and nausea, according to emergency officials.
Residents should follow the latest instructions from Toledo Fire & Rescue and Lucas County emergency management officials rather than relying on whether fog or haze is visible outside.
The latest evacuation information is available through the City of Toledo's official emergency updates.
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