Per the article, the workers didn’t know. The employers didn’t tell them of the dangers or provide the necessary safety training/equipment. From the article:
“Dust was everywhere, he said, and he was given only a dust mask — one he said was inadequate for the job — to protect himself. Sometimes he brought a hose and tried to attach it to the machine to reduce dust, but there were no machines dispensing water as they were cutting, he said.”
“Segura Meza had never heard of silicosis before he was diagnosed.”