The pollution, some of which came from the burning of vinyl chloride, a carcinogen, spread over 540,000 square miles, showing clearly that "the impacts of the fire were larger in scale and scope than the initial predictions," the authors of the study, published in Environmental Research Letters, found.

Lead author David Gay, coordinator of the National Atmospheric Deposition Program, said that he was very surprised by the way the chemicals had spread. "I didn't expect to see an impact this far out," he told The Washington Post.

Gay said the results did not mean "death and destruction," as concentrations were low on an absolute scale—"not melting steel or eating paint off buildings"—but that they were still "very extreme" compared to normal, with measurements higher than recorded in the previous ten years.

"I think we should be concerned," Juliane Beier, an expert on vinyl chloride effects who didn't take part in the study, told the Post, citing the possibility of long-term environmental impacts on communities.

A Norfolk Southern train crashed in East Palestine, Ohio, a village near the Pennsylvania border and the Appalachian foothills, on February 3, 2023. Dozens of train cars derailed, at least 11 of which were carrying hazardous materials, some of which caught fire after the accident and burned for days. Fearing a large-scale explosion, authorities drained the vinyl chloride from five cars into a trench and set it alight in a controlled burn.