Ohio Train Derailment: Which Toxic Chemicals Were Released and How Dangerous Are They?

On Friday 3rd February, a 150-car freight train operated by Norfolk Southern was derailed outside of East Palestine, Ohio, a small village town of just 5,000 residents. It’s been reported that about 38 cars were thrown off the track by a broken axle, around 20 of which were listed as containers of hazardous materials. Evacuation orders were issued to all households within a two-mile radius – some 2,000 residents – and remained in effect until the following Wednesday. During the evacuation, emergency services are said to have breached five of the derailed cars in order to conduct a controlled combustion of around 250,000 gallons of liquid vinyl chloride, a hazardous material. Most readers will be familiar with the shocking images of this explosion and the resulting column of smoke. 

A comprehensive picture of the accident is yet to emerge, but various aspects of the story have been reported in local and national outlets, with considerable public speculation accompanying their circulation on online forums and social media platforms. Of particular concern are the chemicals released, either as a result of the derailment or the mitigation strategies pursued by emergency services. Again, much remains unclear, but there is a distinctive lack of accessible scientific reporting on those details that are known. What follows is a brief look at the list of identified chemicals, the toxicology and what might be on the horizon for East Palestine, Ohio. 

Vinyl Chloride 

Much of the reporting has focussed on vinyl chloride (or vinyl chloride monomer, VCM) as the primary chemical of concern. The precursor to polyvinyl chloride (PVC), one of the most ubiquitous plastics, vinyl chloride has been an exceedingly important material throughout modern industrial history, one of the many world-shaping petrochemicals unleashed in the second half of the 20th century. Unlike many of its cousins, though, its raw form no longer has a commercial application, it is only used in the production of PVC. As a polymer – as PVC, that is – vinyl chloride is stable, storable and safe. But as a monomer, it’s extremely toxic, one of the class of industrial hazards known as VOCs.

The International Agency for Research on Cancer classifies vinyl chloride as a Group 1 carcinogen, their highest ranking, on account of its connection with various cancers, including lymphomas and brain tumours. Exposure can induce chronic respiratory failure and is particularly toxic to the liver. Birth defects, miscarriage, chronic narcosis, cardiac irregularities, acute eye damage, even localised frostbite. In other words, vinyl chloride is broadly toxic to most parts of the human body. 

As is the case with most hazardous synthetic chemicals, our toxicological knowledge is derived mainly from long-term studies of exposed workers. As this knowledge developed, statutory exposure limits were set and safety protocols implemented, steadily reducing the rates of illness and death. Typically, then, exposure to vinyl chloride occurs at microscopic levels in tightly controlled environments with tried-and-tested protections in place. But, of course, that’s not what happened in East Palestine. 

One of the quirks of vinyl chloride is that it begins to boil at –13°C, a temperature well below global averages. Because increasing pressure raises boiling points, vinyl chloride is transported and stored as a liquid in pressurised containers. If these containers are ruptured, you risk what’s called a ‘boiling liquid expanding vapour explosion.’ As the rupture depressurises the container, a decrease in boiling point causes the vinyl chloride to evaporate, filling the space with highly combustible (and toxic) gas. Of the five cars transporting vinyl chloride, just one was ruptured in this way during the derailment, but the resulting fire risked the explosion of the other cars. Small holes were made into the train cars, whose chemicals were released into pits that were lit on fire.   

When it combusts, vinyl chloride produces two non-toxins, carbon dioxide and water, alongside two toxins, hydrogen chloride and trace phosgene, both of which are less toxic than vinyl chloride. There is one further complication, though, which is that both hydrogen chloride and phosgene react really easily with water. With hydrogen chloride and water, you get hydrochloric acid. At lower levels, this is an irritant to skin, eyes, and lungs, but greater quantities can cause severe burns. Residents and visitors to East Palestine have reported signs of contact with hydrochloric acid vapour, like uncharacteristic eye irritation, on social media. 

In the end, then, it appears that the residents of East Palestine will be confronting the combustion products of vinyl chloride in place of vinyl chloride itself. But we lack the full picture, at the moment. Questions have been raised about the contamination of the soil used to construct the evacuation trench into which the vinyl chloride was siphoned from the uncompromised cars before being burned off. There are similar concerns about the contamination of proximate groundwater.  

At time of writing, the Environmental Protection Agency and regional utilities claims not to have detected any vinyl or hydrogen chloride in the water supply or in the air, having conducted at time of writing assessments on 400 of the roughly 470 previously evacuated homes near the site of the derailment. Some residents of East Palestine, though, have reported symptoms linked to vinyl chloride exposure, including prolonged nausea and headaches. However, such symptoms are consistent with low levels of exposure and are not necessarily indicative of quantities with long-term, life-threatening consequences. Nevertheless, medical professionals have advised that any residents experiencing unusual symptoms of any kind notify their healthcare provider. 

Other hazardous materials involved in the derailment have been detected, though. 

Butyl acrylate 

One of them is butyl acrylate, a key component in the production of automotive coatings, paints, plastics and resins. A car filled with liquid butyl acrylate either spilled or caught fire as a result of the derailment, according to the EPA. It is an irritant to the nose, throat and lungs, and people exposed to it can get headaches, dizziness, nausea or vomiting, according to the New Jersey Department of Health. Such a symptomatology makes it possible that this chemical is the source of the ailments reported by residents. It is, on the whole, far less toxic than vinyl chloride, but repeated exposure can cause lung damage.  

On February 10th, exactly one week after the derailment, the Ohio Environmental Protection Agency has detected low levels of butyl acrylate and ethylhexyl acrylate in waterways near the site.  

Ethylhexyl acrylate 

Another hazardous substance involved in the derailment that the local EPA has detected in the Ohio Basin is ethylhexyl acrylate, also an ingredient in modern paints and plastics. One of the breached cars contained this combustible liquid. Ethylhexyl acrylate is a skin, eye, and lung irritant for humans, but a safety report from a chemical manufacturer, Arkhema, describes the substance as “acutely toxic” to fish in large quantities. In the days immediately following the derailment, an estimated 3,500 fish of 12 different species have been found floating dead across some 7.5 miles of stream. 

Ethylene glycol monobutyl ether 

At time of writing, the status of one car of ethylene glycol monobutyl ether is currently “unknown” to the U.S. EPA. A clear liquid used, again, in products like paint and varnish, ethylene glycol monobutyl ether is highly combustible. The chemical may have a deleterious effect on the central nervous system, blood, and liver, according to the National Institutes of Health.