What we know about the Ohio train derailment

A black plume rises over East Palestine, Ohio, on Feb. 6 after the controlled detonation of derailed train cars. Photo: Gene J. Puskar/AP

Residents of an Ohio town who had been evacuated after a toxic freight train derailment earlier this month are demanding answers from the railway company involved as well as elected officials over health concerns.

The big picture: As emergency crews continue to clean up the site of the Norfolk Southern train derailment in East Palestine, Ohio, lawmakers have drawn attention to the government's oversight of the freight train system. Meanwhile, the Biden administration has promised to hold the rail operator accountable for the wreck and its aftermath.

Catch up quick: Norfolk Southern officials said some of the cars carrying the vinyl chloride were not breached during the crash but were at risk of exploding, so crews released and burned their contents on Feb. 6, creating a massive smoke plume above the town for several hours.

A mechanical issue with an axle of one of the 150 cars is believed to be the cause of the derailment of at least 50 of the cars, though the National Transportation Safety Board has not yet made an official determination of the cause.

Acute exposure to high levels of vinyl chloride, a classified human carcinogen, in the air has been linked to central nervous system effects, while chronic exposure has been shown to cause liver damage, including a rare form of liver cancer, according to the EPA.

The Environmental Protection Agency has said it has not detected any "levels of concern" of hazardous substances released during or after the crash, though the agency is continuing to monitor the air throughout East Palestine, including inside at least 210 homes.

The Ohio Department of Natural Resources estimates that 3,500 fish of 12 different species, none of which are endangered, died after the crash across approximately 7.5 miles of streams south of the town, ODNR director Mary Mertz said on Tuesday.

On Feb. 17, Ohio Gov. Mike DeWine (R) said the Department of Health and Human Services will help state health authorities set up a clinic in East Palestine so that any resident, including those without insurance, may visit a doctor over any health concerns.

Context: The day before, DeWine said that despite being in "daily contact" with FEMA, the agency said "Ohio is not eligible for assistance at this time." The agency typically responds to disasters that involve extensive property damage.

The EPA sent Norfolk Southern a "General Notice of Potential Liability" letter on Feb. 10, in which it said it had determined that the company "may be responsible under [Comprehensive Environmental Response, Compensation and Liability Act] for cleanup of the Site or costs EPA has incurred in cleaning up the Site."

In a press release on Feb. 14, the company said it has donated $1.2 million to around 1,000 families to cover expenses they incurred from their evacuations and was in the process of providing aid to local businesses.

Go deeper: Ohio derailment prompts calls to investigate federal oversight of trains

Editor's note: This story has been updated with additional details throughout.