Crews from Northwest Fire District responded to a hazardous materials call shortly before 6:30 a.m. on Monday at Staker Parson Cement Plant on the 5400 block of West Massingale Road after a silo valve malfunctioned, according to district spokesperson Adam Goldberg.
The hazardous material released from the leak was initially thought to be lye, though crews later determined that to be incorrect.
“The material that is considered caustic and harmful was crushed and powered limestone, which is part of the mixture used in the production of cement,” said Goldberg. “The limestone is still caustic and can cause irritation and caustic burns.”
The cement dust traveled north from the plant, Goldberg said.
Two employees were covered in chemical dust when the valve broke, and two others were later covered when attempting to fix it.
All four were taken to a local hospital for treatment, and released hours later.