Is the air in East Palestine safe to breathe? Here's what experts and officials say.

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In the week since officials conducted what they called a "controlled release" of vinyl chloride from five derailed train cars in East Palestine near the Ohio-Pennsylvania border, concern has grown among some over the quality of the air in and around the village of nearly 5,000 people.

The decision to conduct the release of the carcinogen was made after officials said they noticed a drastic temperature change inside the cars. Fearing an explosion with potential shrapnel, the vinyl chloride was released in liquid form into an area surrounded by a barrier and ignited, sending a giant column of flames and black smoke into the winter sky.

Here's what we know about the air quality in East Palestine and the surrounding area:

Is the air in East Palestine safe to breathe?

Some East Palestine residents who have since returned to their homes after being evacuated have reported experiencing headaches and nausea. Others say the air has a foul odor to it.

Bruce Vanderhoff, director of Ohio's health department, said during a news conference Tuesday that most of the chemicals on the Norfolk Southern train that derailed Feb. 3 are volatile organic compounds (VOCs).

VOCs are emitted during everyday activities like pumping gas, burning wood or natural gas, he said.

More:Ohio train derailment: What's still unknown after chemical disaster forced evacuations?

Low levels of VOCs can be smelled and sometimes cause headaches and irritation, said Vanderhoff, who noted that most people can be around VOCs at low levels without feeling ill. High levels can result in longer-term health effects, he said.

Vanderhoff said recent testing shows the air in East Palestine was just like it was prior to the train derailment.

"We have taken every step possible to ensure people's safety was first and foremost," Vanderhoff said.

What does the EPA say?

When burned, vinyl chloride gives off hydrogen chloride and the toxic gas phosgene.

The Environmental Protection Agency said Tuesday that it had stopped monitoring the air in East Palestine for phosgene and hydrogen chloride the day before.

"Since the fire went out on Feb. 8, EPA air monitoring has not detected any levels of health concern in the community that are attributed to the train derailment," EPA Region 5 Administrator Debra Shore said in a statement on the agency's website. "Air monitoring data was provided to state health agencies on Feb. 8 for review prior to the state's decision to lift the evacuation.

Shore also said in her statement that vinyl chloride has not been detected in any of the nearly 400 homes that the EPA had screened under a voluntary program as of Tuesday morning. Sixty-five additional homes were scheduled to be screened that afternoon, she said.

What is acid rain?

Acid rain, as defined by the EPA, is a broad term that includes any form of precipitation with acidic components, such as sulfuric or nitric acid that fall to the ground from the atmosphere in wet or dry forms.  This can include rain, snow, fog, hail or even dust that is acidic.

Acid rain results when sulfur dioxide (SO₂) and nitrogen oxides (NO_X) are emitted into the atmosphere and transported by wind and air currents, the EPA says on its website. The SO₂ and NO_X react with water, oxygen and other chemicals to form sulfuric and nitric acids. These then mix with water and other materials before falling to the ground.

Coal-burning power plants are responsible for most of the nation’s sulfur dioxide pollution and a significant portion of nitrogen oxide emissions. Sulfur dioxide emissions have decreased substantially over the years.

Coal has historically been the largest electricity source in the Ohio. However, in 2019, it was overtaken by natural gas.

Could acid rain have formed after controlled release?

Acid rain could have formed after the controlled release and burn of chemicals on Feb. 6, Kevin Crist, professor of chemical and biomolecular engineering and the director of the Air Quality Center at Ohio University, said. If it did form and fall, it would have most likely occurred downwind of East Palestine.

When burned, vinyl chloride gives off hydrogen chloride and the toxic gas phosphene, which was used as a weapon during World War I. Vinyl chloride in the atmosphere breaks down into hydrochloric acid, a component of acid rain.

"There would maybe be localized problems, but once that plume is gone, it's gone. Unless it's sticking to a residue," Crist said.

East Palestine residents may want to wipe down surfaces in homes for possible residual material, he added.

"We'll just have to listen to what Ohio EPA has to say about what their estimates about how much chemicals were spilled and how they are planning to monitor its movement," Crist said. "And everybody should pay attention to where they're getting their own water. If they have municipal supply, what they say about the level of risk."

Monroe Trombly covers the workplace and environmental issues for The Dispatch.

mtrombly@dispatch.com

@monroetrombly

This article originally appeared on The Columbus Dispatch: Concern over air quality rises after East Palestine train derailment