A health and safety investigation of car parts manufacturer Renosol will begin next week after employees expressed discontent with working conditions. 

Renosol employees delivered a letter to management Thursday addressing health and safety concerns in the company’s Dallas County plant. Among other things, the letter asked for free health screenings for employees in connection with a chemical called TDI, used to make foam in the company’s car seats.

Dallas County’s Renosol plant forwarded the letter to the Lear Corporation — a Fortune 500 company that owns the plant.

On friday, Lear representatives said a health and safety team would be at the plant this week to begin an investigation.

“What’s concerning is were our employees put at risk,” Lear spokesman Mel Stephens said. “Wherever there is an incident, we send a team in to investigate and intend on doing that in this case. We will conduct our investigation and deal with whatever the findings are.”

The investigation team is an independent entity, Stephens said.

Lear was unaware of any prior incidents prior to Thursday’s letter, according to Stephens.

The employee’s letter addresses one, specific incident on May 1, when TDI reportedly began to leak into the air. The letter states management put a diaper — a combination of fabric and plastic — on the leak following the incident. After the leak was temporarily repaired with the diaper, employees continued to work, Renosol employee Kimberly King said. A few days later, management made a more permanent fix, King said.

TDI, officially named Toluene disocyanate, is toxic for both short- and long-term exposure, according to the Environmental Protection Agency. The EPA’s website said chronic inhalation of TDI can result in significant decreases in lung function and asthma-like reactions.

TDI is monitored in Renosol’s plant, but monitoring instruments have sounded frequently recently, signaling high concentrations of the chemical, according to King.

King currently takes several different medicines to deal with asthma-like symptoms and attributes her illness to repeated TDI exposure.

“When I started working at the plant, I never had asthma or bronchitis,” she said. “After working there for nine years, I’ve had to start using inhalers and other medications. I can’t even lay flat at night when I go to sleep.”

A news release from a public relations firm representing the employees stated 75 percent of the roughly 90 workers at the plant suffer from some type of respiratory illness associated with TDI. King says she is among a group of dozens, many are afraid to speak out.

Stephens said some of the employee’s allegations don’t match up with what Lear knows.

“We have an outstanding record of compliance,” Stephens said. “We don’t take anything like [the allegations] lightly.”

The letter contains references to long hours and low pay. Renosol employees are also working with the United Automobile Workers union to help form a Renosol workers union in Dallas County. The employees met with union representatives after delivering the letter Thursday. Stephens said he considers union formation a separate issue.