High levels of a hazardous chemical polluted the air weeks after the Ohio train derailment, an analysis shows

Soon after the derailment of a Norfolk Southern train in East Palestine, Ohio, a team of researchers began roving the small town in a Nissan van.

It was February, less than three weeks after the disaster, and the van was outfitted with an instrument called a mass spectrometer, which can measure hundreds to thousands of compounds in the air every second.

The team was searching for harmful levels of air pollution. At the time, a primary concern was a flammable substance called vinyl chloride, because Norfolk Southern intentionally burned off the chemical in an attempt to avoid the chance of an explosion. Some environmental health experts thought the chemical may have contributed to the rashes, vomiting, bloody noses and bronchitis some residents reported.