If you haven’t heard, 60,000 gallons of liquid asphalt spilled into the Yellowstone River in Montana late last month after a train derailed while crossing a bridge.

Yep, another derailment.

That’s about 500,000 pounds of a thick, tarry substance primarily made from petroleum and other chemicals.

Locals are concerned about environmental damage and threats to wildlife but have been met with a unified response from the Environmental Protection Agency, Montana Rail Link, and the Montana Department of Environmental Quality that there won’t be any damage.

The last few weeks have involved a frenzied cleanup of the river and the surrounding environment, which is expected to stretch 100 miles downstream.

So far, the combined operation by the three organizations has collected 80,000 pounds of loose asphalt, just under a fifth of what is believed to have spilled in the river.

The cleanup process is pretty simple. Crews scoop it up and roll it into balls, like Play-Doh.

During public hearings, Paul Peronard, an EPA employee leading clean-up efforts, said the asphalt would not mix with the water and said there would be no environmental threat. He added that tests of the water showed that it was clean.

“If I have to talk about and compare this to other responses, this is going to have a fairly minimal long-term impact because of the lack of water solubility,” he said at the public hearing earlier this month. “It’s not a particularly toxic material.”

However, locals, industry experts, and various studies paint a more complicated picture of how dangerous an asphalt spill can be, ranging from relatively harmless to environmentally dangerous.

“It feels to me that they’re trying to minimize it, as if it’s not a big deal and that there won’t be environmental impacts,” said Alexis Bonogofsky, a local photographer, sheep rancher, and community organizer who lives close to the spill. “Asphalt actually can be soluble in water, and they’re acting like that’s impossible. We’ve already seen the environmental impacts.”

She told Reckon that she and other locals had seen a thin layer of oil in the back channels of the Yellowstone River. A small number of birds have been found dead and stuck to the asphalt, which becomes sticky in heat and solidifies in cooler temperatures. Eventually, it can crack under repeated exposure to both temperature extremes.

What’s the real deal with asphalt?

While some studies note that an asphalt spill can be dangerous to the environment, industry experts have a slightly more moderate opinion of what the damage could be.

“It depends because there are many different types of asphalt,” said Dr. Mervin Fingas, an oil and chemical spill research expert and former chief of the Emergencies Science Division of Environment Canada. “Some have a little bit of oil in them [that] could lead to some effects and other types do not.”

While asphalt is almost completely made of crude oil, also known as petroleum, Dr. Fingas is describing the small amounts of loose oil on the surface of the asphalt that can easily be washed off. That oil is usually residue that collects on the asphalt during the transportation process.

He added that asphalt is rarely toxic in water and won’t get caught in the water system but also said that if it were to coat a rock, tree, or piece of land, “it would likely stay there forever.”

Dr. Michael Boufadel, director of the center of natural resources at the New Jersey Institute of Technology, told Reckon that the speed of the Yellowstone River would likely mitigate some of the pollution but did point to some examples of environmental danger.

“The smothering of flora with asphalt should also be considered,” he said. “[And] sometimes taking action to mitigate the damage can disrupt the environment more, and maybe this explains the lack of action in some cases, and the reliance on a process called natural attenuation.”

Natural attenuation is when pollution is cleaned through a natural process free of human intervention. For example, bugs and microbes can eat some chemical pollution; the pollution can mix with water to become diluted enough that it is no longer dangerous, and also through a more complicated evaporation process.

But it can also happen when the asphalt sticks to river sediment like soil and sand, which holds it in place. It doesn’t leave the polluted site, but it is prevented from being absorbed into groundwater.

But that particular process also has downsides.

“During the spill, [the asphalt] probably interacted with the fine sediments suspended in the river water,” added Boufadel. “Then, they form oil particle aggregates (OPA) that would eventually sink to the bottom.”

Oil particle aggregates are basically what happens when oil-based substances mix with soil and sand. Studies have specifically noted that these particles can do “great harm” to creatures that help keep river sediment and water clean, like snails, worms, muscles, and insects. Larger water-based animals can also eat those contaminated creatures and the oily particles.

Several studies have noted that the nature of asphalt in water is not well known, and how it behaves depends on the chemical composition of the asphalt, which can vary.

But all were firm on one thing: asphalt can cause environmental harm.

“After the spilled asphalt hardens, it begins to weather and break into smaller pieces that can be ingested,” noted a 2009 University of New Hampshire study, one of the few studies about how asphalt interacts with water. “Fish and turtles are some of the species at risk of ingesting asphalt. There could potentially be chronic effects and little is known about bioaccumulation of asphalt constituents in the food web.”

The study also noted that toxicity levels vary from batch to batch and that while the asphalt is sticky, there can be some leaching – when oils can escape the asphalt and create an almost transparent rainbow sheen on the water. That is less likely once the asphalt hardens, noted the study. But it’s at that point when it can break apart and be ingested by animals.

The study was co-authored by the then-co-director of environmental science at the National Oceanic and Atmospheric Administration, a federal agency.

Interestingly, using asphalt to stabilize riverbanks from the threat of erosion is prohibited under the Clean Water Act because of the potential for pollution. When asphalt breaks into smaller particles, it can contaminate stormwater, downstream rivers, lakes, and streams, according to the Metropolitan North Georgia Water Planning District, an Atlanta-based water management organization established by the Georgia State legislature in 2001.

The group also notes that hardened asphalt can clog and damage stormwater drains and pipes, which can result in localized flooding.

“So the government says it can’t be used to reinforce riverbanks, but 500,000 pounds floating around is okay?” queried Bonogofsky.

The EPA has played down the environmental consequences of spills in the past.

After the train derailment and subsequent explosion in East Palestine in early February, the nation’s top environmental regulator said the air and drinking water quality was normal, and the site was safe. Environmental experts later said the EPA shouldn’t make those promises, and locals must monitor their health for years.

The Yellowstone River is no stranger to oil-based spills, with two others occurring over the last 12 years. In 2011, an Exxon pipeline spilled 63,000 gallons into the river. Four years later, the U.S. Department of Transportation forced the company to pay a $1 million fine and rejected its appeals. In 2015, another pipeline burst, releasing around 40,000 gallons into the river.

In January 2022, a company in Tacoma, Wash., was fined $650,000 after 60,000 gallons of liquid asphalt spilled at its facility in 2015.

Peronard said during the public hearings that cleanup crews only expect to collect about 30% of the asphalt and that it has probably already reached the Mississippi River, the largest delta system in North America that also happens to be one of the country’s richest and most vibrant ecosystems.

The rest of the asphalt – tens of thousands of pounds – will either sink, stick to rocks and riverbanks and spend years being slowly eroded or float out to the Gulf of Mexico, added Bonogofsky

Although not a major concern to the environment, in his estimation, Dr. Fingas said there were other lessons for the companies that transport dangerous substances, such as asphalt, oils, and other chemicals.

“This spill could have been something far more dangerous, and they need to acknowledge that by strengthening infrastructure and increasing safety measures,” he said. “Caution is the better part of wisdom.”