(NewsNation) — A month after the Norfolk Southern train derailment in East Palestine, Ohio, residents Thursday are still questioning the health impacts of pollution that spilled into their community.

In a letter sent Wednesday to Transportation Secretary Pete Buttigieg and Ohio Gov. Mike DeWine, railroad union leaders claim that rail workers are reporting illnesses after working at the site of the derailment.

“Many other employees reported that they continue to experience migraines and nausea, days after the derailment,” the letter states. “And they all suspect that they were willingly exposed to these chemicals at the direction of NS.”

The letter criticizes Norfolk Southern for putting workers at risk and not providing them with the proper personal protective equipment.

Amid criticism from Republicans over the decision so far not to visit the community, President Joe Biden said Thursday he will visit East Palestine, Ohio, “at some point,” according to The Hill.

“We will be implementing an awful lot through the legislation here, and I will be out there at some point,” Biden said.

When asked about Biden’s comments, however, White House press secretary Karine Jean-Pierre said that she had no new travel plans to announce for the president.

Environmental activist Erin Brockovich, however, returned to East Palestine for another town hall meeting less than one week after her initial visit.

According to a Facebook post by East Palestine Justice, Brockovich discussed how community members can take legal action against Norfolk Southern for the train derailment toxic chemical spill.

New findings show the fire that erupted after the derailment melted a key part of the tank cars filled with toxic chemicals, so federal officials warned railcar owners Thursday to check their fleets for similar flaws.

National Transportation Safety Board investigators determined the aluminum covers over the pressure relief valves on three of the five tank cars carrying vinyl chloride melted, and that some of the metal was found around the valves.

The NTSB said melted aluminum may have degraded the performance of the valves and kept them from releasing some of the flammable gas to relieve pressure inside the tank cars. Norfolk Southern CEO Alan Shaw has said the failure of the valves was part of the reason why officials decided to breach the cars and burn off the vinyl chloride. 

A Norfolk Southern representative is expected to attend a public meeting Thursday evening, according to an order from the Environmental Protection Agency (EPA). Residents will get to address the representative directly according to multiple reports.

Last month, Norfolk Southern backed out of a local town hall, according to CNN, citing threats against its employees.

The Associated Press contributed to this report.