Many residents of East Palestine, Ohio, have warily returned to their homes after a Norfolk Southern train derailed and spilled more than 100,000 gallons of dangerous chemicals into the air and water earlier this month.

The towering smoke cloud from the burning vinyl chloride has drifted away, and the track has been cleared. Trains are now running again through the town. But the 4,700 residents of East Palestine say they still smell chemical residue in the air, see an oily sheen in the water, and are suffering from headaches and nausea. Concern is mounting about the long-term effects of the disaster.

It’s also become a political football. Transportation Secretary Pete Buttigieg visited East Palestine this week and apologized for not speaking about the derailment sooner. Former President Donald Trump also visited the town and criticized President Joe Biden for going to Ukraine this week instead of Ohio. (Trump himself has faced criticism for rolling back train safety rules.)

Other government officials are trying to assure residents that much of the risk has faded. This week, Ohio Gov. Mike DeWine and Environmental Protection Agency Administrator Michael Regan both visited East Palestine and drank tap water in a resident’s home.

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“You don’t know who to trust. That’s a big part of it — the uncertainty. You don’t know if you’re going to have to move,” one resident, Carolyn Brown, told ABC News. “We need to feel that we’re safe.”

But “safe” may be more than anyone can promise.

“‘Safe’ is one of those four-letter words in a [disaster] response you just don’t use,” said Stan Meiburg, executive director of the Center for Energy, Environment, and Sustainability at Wake Forest University and a former career EPA official who worked on toxic waste cleanup. “What people consider ‘safe’ is highly variable … plus, EPA just can’t answer that question.”

Instead, agencies like the EPA try to measure what they can and extrapolate from past research. They compare the concentrations of pollutants they measure to limits established by health departments, which don’t always reflect the dangers an individual will face. Children, for example, breathe in more air proportionate to their body size and thus are more vulnerable to airborne toxic chemicals. And scientists aren’t clear how the health effects of the specific toxic chemical brew that shrouded East Palestine will play out over time.

Authorities nevertheless told residents they could return home. In doing so, the people of East Palestine may face low levels of exposure to some of the dangerous chemicals from the derailment, with uncertain health effects.

So now begins a years-long effort to track the effects of the leaked chemicals, to mitigate their harms, to analyze why the train derailed, and to prevent the next spill. While this is uncharted territory for health and environment agencies, experts say there are some best practices to better understand the disaster and to protect residents. But they require continued attention and resources long after media coverage fades and political wrangling stops.

The next steps in the response to the East Palestine chemical spill

Of the 38 cars that derailed on February 3, 11 were known to hold hazardous chemicals, according to the National Transportation Safety Board. These included chemicals like vinyl chloride, a flammable carcinogenic gas, and butyl acrylate, a toxic flammable liquid. Some leaked, some were vented, and some burned, further complicating the picture.

“Each of the chemicals that leaked are respiratory irritants, and some of their breakdown products are also irritants,” said Marilyn Howarth, an environmental toxicologist at the Perelman School of Medicine at the University of Pennsylvania, in an email. “This is part of what is unclear: How much of each was experienced by each person and for how long?”

Occupational health researchers have found that workers who are regularly exposed to chemicals like vinyl chloride have higher rates of liver cancer. It’s a signal that can take 20 years or more to emerge, Howarth said. However, these workers were exposed to higher doses and in enclosed spaces, unlike the residents of East Palestine. It’s not clear how exposures from the train derailment will play out, but the long latency of vinyl chloride’s worst effects means that it’s critical to track its concentrations in the community for years to come.

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Meanwhile, residues from burning vinyl chloride, like dioxin, and other leaked chemicals, like butyl acrylate, can haunt water supplies for years and spread through watersheds and underground aquifers that provide drinking water.

“The aquifer may remain contaminated for years, even a decade, despite best clean-up efforts in the short and long term,” Abinash Agrawal, a professor of earth and environmental sciences at Wright State University, said in an email. “This may not be a threat to breathable air quality, but definitely toxic in drinking water as it can migrate and move/travel in a groundwater plume of contamination to the pumping wells nearby up to several thousand feet.”

So state and federal environmental agencies will also need to check water and soil samples regularly for contamination for years.

Parts of East Palestine and the surrounding region will also have to be decontaminated, cleaned up, and remediated. The water used to extinguish the train fire is now toxic, and 2 million gallons of it are being sent to Texas, where it will be injected underground for disposal. The contaminated soil around the train tracks is being excavated and sent to a toxic waste disposal site in Michigan. The community may also have to look for a new drinking water source, Agrawal said.

The National Transportation Safety Board is conducting an investigation of the root causes of the train wreck. Federal regulators will have to consider whether to impose new safety regulations on the rail industry.

The residents of East Palestine will also have to keep tabs on their health. Philip Landrigan, director of the public health program at Boston College, studied 20,000 first responders and rescue workers in New York City after the 9/11 attacks in 2001. He said one of the key lessons learned from that study was that in addition to figuring out exactly what was in the dust that people were breathing in, it was also important to conduct regular health assessments to catch problems that emerged over time.

“A program has to be put in place to get baseline health evaluations of people in the town, even people that appear to be okay, and follow them up periodically over the next decade or more,” Landrigan said.

Norfolk Southern will have to pay

All these measures, however, will cost a lot of money. “You can’t expect the people who were the victims of this catastrophe to pay for that themselves,” Landrigan said.

To that end, the EPA has ordered Norfolk Southern to pay for the cleanup of the train derailment and the response. If they fall short, the rail operator could face a fine of $70,000 per day according to EPA administrator Regan. “Norfolk Southern will pay for the mess that they created and the trauma that they inflicted on this community,” he said during a press conference this week.

But that doesn’t account for the ongoing health needs of East Palestine, and the total medical bill could be massive. A number of residents are now looking to sue the railroad company. Norfolk Southern has also committed $5.6 million in financial assistance and support to the town.

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One of the biggest challenges, however, will be rebuilding trust between the community and the government. A half-dozen federal offices along with local authorities are playing roles in the disaster response, which is making it difficult for some residents to figure out who should be held accountable.

And agencies like the EPA are struggling to communicate how to interpret their measurements of chemical exposures and how residents should respond to their findings. Things like quantifying the toxic chemicals in the air, soil, and water and determining that they’re below reference levels don’t address the anxiety that the people of East Palestine may feel.

“One thing that I hope we will see the agency doing is recognizing that assurances to people are not just giving them numbers but rather helping them have access to resources that will help them discuss their feeling about the matter,” said Meiburg.

“This has been a traumatizing event for the community,” he added. “To think about this as a ‘one and done’ experience is probably a mistake.”