U.S. House Republicans have accused Transportation Secretary Pete Buttigieg of being too slow to get involved in this month's toxic train derailment, CBS News reported on Friday.

On February 3, 38 cars of a Southern freight train derailed in East Palestine, Ohio, including 11 tanker cars carrying hazardous chemicals including vinyl chloride. The derailment has spurred serious health and safety concerns over air quality and drinking water.

House Republicans are launching a probe into the Department of Transportation's (DOT) response to the derailment in the town of 4,700 people.

Buttigieg, who took 10 days to publicly address the crisis, told CBS News on Tuesday that he should have publicly addressed the crisis sooner, and that it was a "lesson learned" for him, but said he was focused on making sure his Transportation Department employees had what they needed.

Republicans, led by House Oversight and Accountability Committee Chairman James Comer of Kentucky, are asking Buttigieg for all documents and communications about his public response to the derailment; all records showing when he learned about the derailment; any change to DOT train maintenance and procedures since January 2021; and all documents and communications regarding the National Transportation Safety Board's progress on the cause of the derailment.

"This incident is an environmental and public health emergency that now threatens Americans across state lines," the Republicans wrote to Buttigieg. "Despite the U.S. Department of Transportation's responsibility to ensure safe and reliable transport in the United States, you ignored the catastrophe for over a week. The American people deserve answers as to what caused the derailment, and DOT needs to provide an explanation for its leadership's apathy in the face of this emergency." 

Overheated axle

The initial investigation results by the National Transportation Safety Board (NTBS) released on Thursday found the train was alerted three times by three hot bearing detectors (HBD), which provide audible, real-time warnings to train crews, on its trip before the derailment on the night of February 3.

At first, the axle was 38 degrees Fahrenheit above ambient temperature. By the second alert, the axle was 103 degrees above ambient temperature. When the third alert went off, it was 253 degrees above ambient. 

NTBS said a recorded temperature 200 degrees above ambient is considered "critical" and the train must stop, adding the crew "took immediate action" after hearing the third alarm and stopped the train. While increasing the brake application to stop the train, a wheel bearing failed. 

Threats of dioxins long-lasting 

Last week, Sherrod Brown and J.D. Vance, the U.S. senators from Ohio, sent a letter to the state's environmental protection agency expressing concern that dioxins may have been released when some of the chemicals in the damaged railcars were deliberately burned for safety reasons. 

Linda Birnbaum, a leading dioxins researcher, toxicologist and former director of the National Institute for Environmental Health Sciences, said that burning vinyl chloride does create dioxins. Other experts agreed the accident could have created them.

Dioxins refer to a group of toxic chemical compounds that can persist in the environment for long periods of time, according to the World Health Organization. They are created through combustion and attach to dust particles, which is how they begin to circulate through an ecosystem.

Residents near the burn could have been exposed to dioxins in the air that landed on their skin or were breathed into their lungs, said Frederick Guengerich, a toxicologist at Vanderbilt University.

But the main pathway that dioxin gets into human bodies is not directly through something burning like the contents of the East Palestine tanker cars. It's through the consumption of meat, dairy, fish, and shellfish that have become contaminated. That contamination takes time.

"That's why it's important for the authorities to investigate this site now," said Ted Schettler, a physician with a public health degree who directs the Science and Environmental Health Network, a coalition of environmental organizations.

There is already some level of dioxins in the environment – they can be created by certain industrial processes, or even by people burning trash in their backyards, said Murray McBride, a Cornell University soil and crop scientist.

Once they are released, dioxins can stick around in the soil for decades. They can contaminate plants including crops. They accumulate up the food chain in oils and other fats.

In East Palestine, it's possible that soot particles from the plume carried dioxins onto nearby farms, where they could stick to the soil, McBride said.

"If you have grazing animals out there in the field, they will pick up some of the dioxins from soil particles," he said. "And so some of that gets into their bodies, and then that accumulates in fat tissue."

It takes between 7 and 11 years for the chemical to start to break down in the body of a person or animal. And dioxins have been linked with cancer, developmental problems in children, and reproductive issues and infertility in adults, according to the National Institute for Environmental Health Sciences.

(Cover: Transportation Secretary Pete Buttigieg tours the site of the Norfolk Southern train derailment in East Palestine, Ohio, U.S., February, 23, 2023. /CFP)

(With input from agencies)