(NewsNation) — Safety concerns are still on the minds of many a couple of weeks after 50 train cars, 10 of them carrying hazardous materials, derailed in the Ohio village of East Palestine.

No one was injured in the derailment, but three days after it happened, authorities burned vinyl chloride found inside five tanker cars. Officials said they needed to burn the vinyl chloride because of the threat of a larger explosion if nothing was done.

Vinyl chloride, according to the Centers for Disease Control, is a colorless gas with a temperature of below 7 F. While it does burn easy, the substance, which has a “mild, sweet” odor is not stable at high temperatures. Per the CDC, vinyl chloride does not occur naturally, and can be formed when trichloroethane, trichloroethylene and tetrachloroethylene are broken down.

Vinyl chloride is also called chloroethene, chloroethylene, and ethylene monochloride.

What is vinyl chloride used for?

Vinyl chloride is primarily used to make polyvinyl chloride, which Cancer.gov says is a hard resin used to make plastic products like pipes, packaging materials, wire and cable coatings. It is produced as a combustion product in tobacco smoke as well, the website said.

Sil Caggiano, a hazardous materials specialist, told NewsNation local affiliate WKBN vinyl chloride can be used to make the casings that go on the outside of electrical wires.

“It has a wide variety of usages,” he said to the news outlet.

Is it dangerous?

The U.S. Department of Health and Human Services, International Agency for Research on Cancer and Environmental Protection Agency all classified or determined that vinyl chloride is a human carcinogen. In addition, the CDC said, animal studies have shown that exposure to the substance during pregnancy can affect a fetus’ development.

Chemical engineering professor Dr. Eric Beckman previously told NewsNation said the risks posed by chemicals are very serious.

“It’s a suspected carcinogen. Long-term exposure is associated with cancers, particularly of the liver,” he said. “Short-term exposures, if they’re high enough, it’s just toxic — it can harm you and kill you.”

Environmental regulators and local officials have insisted the air and water in communities nearby the train derailment are safe.

“Since the initial derailment, EPA has led robust air-quality testing (including with the state-of-the-art ASPECT plane) in and around East Palestine. At this time, our air monitoring has not detected any levels of health concern that can be attributed to the incident,” EPA Great Lakes said on Twitter. The agency also mentioned it has screened 396 homes as of Tuesday morning, with no detections of vinyl chloride or hydrogen chloride being identified.

However, local residents are still worried. The Associated Press reports that some have said they got headaches, and are feeling sick since the derailment.

Also concerning residents is seeing fish in local bodies of water dying. NewsNation obtained video of dead fish in the Ohio River, near East Palestine, while WKBN got footage in local streams.

It’s possible the pollution lowered dissolved oxygen levels in the water, basically suffocating the fish, but that hasn’t been confirmed, according to Wildlife Officer Supervisor Scott Angelo, though he said “given the circumstances of where the kill originated, it would seem highly likely that it is associated with the incident.” Insider reports that chickens have also been found dead in their coop in East Palestine, while Newsweek spokes to a resident whose foxes suffered from chemical exposure. One of them died.

How do you know if you’ve been exposed to it?

Vinyl chloride can make people feel dizzy or sleepy. In severe cases, breathing high levels can make you pass out, or even lead to death.

Those with several years of exposure have seen changes in their liver structure, according to the CDC, while some who work with the chemical report nerve damage and “develop alterations in immunity.” Others who worked with and were exposed to very high levels of the substance have problems with the blood flow in their hands — their fingers turn white and hurt when they are in the cold.

Spilling it on skin can cause numbness, redness and blisters.

There are tests that can measure vinyl chloride in people’s blood, breath, and urine, as well as skin ad organ tissue, although the Ohio Department of Health notes these are not available at most doctor’s offices, and some aren’t useful for measuring low levels.

“These tests may show if you have been exposed to vinyl chloride, but they cannot tell you if you will be sick or where the vinyl chloride came from,” the department said.

What happens when it burns?

Officials said the controlled burn of vinyl chloride could send phosgene, a highly toxic gas that can cause vomiting and breathing trouble, and hydrogen chloride, which can irritate humans’ skin, eyes, nose and throat, into the air.

Neil Donahue, a professor of chemistry at Carnegie Mellon University in nearby Pittsburgh, said to the Associated Press that he’s worried burning the chemical could have formed dioxins. Dioxins are created by burning chlorinated carbon materials. Dr. Lynn Goldman, the dean of George Washington University’s School of Public Health, also said to the AP that this is a possible risk — but she’s more concerned about “uncombusted vinyl chloride vapors that could be lurking in the immediate vicinity.”

Are there other chemicals people are concerned about?

The Columbus Dispatch reports that vinyl chloride and butyl acrylate were the first two chemicals officials disclosed were released after the derailment.

A letter to Norfolk Southern from the U.S. Environmental Protection Agency later stated that ethylene glycol monobutyl ether, ethylhexyl acrylate and isobutylene were also in the rail cars, WKBN said.

Butyl acrylate is a clear, colorless liquid with a sharp odor, according to the National Library of Medicine. It is soluble in water, and used to make paint, coatings, caulks, sealings and adhesives. According to the Dispatch, this chemical found on the train car was completely lost due to the spill and fire.

Ethylhexyl acrylate is a clear colorless liquid that the National Library of Medicine says has a pleasant odor. It’s used for making paints and plastics. Caggiano said ethylhexyl acrylate is a carcinogen that can cause the skin and eyes to burn and get irritated.

Isobutylene, like the other two gases, is colorless with a “faint petroleum-like odor,” the National Library of Medicine said. Contact with it in liquid form can cause frostbite, and is easily ignited. Used in the production of isooctane, a high-octane aviation gasoline, it is also known to cause dizziness and drowsiness.

Glycol monobutyl ether appears as a colorless liquid, with a “mild, pleasant” odor. It is used as a solvent, as well as to make paints and varnish. If ingested, it may be toxic, and can also irritate people’s skin and eyes.

The Associated Press contributed to this report.