The article mentions the causation problem but doesn't follow it up. I can't find where or if they have a control case, e.g., measure some other external common

The article mentions the causation problem but doesn't follow it up. I can't find where or if they have a control case, e.g., measure some other external common substance, like wood or rock dust, in the body and see if it also correlates with lesions. I expect it would too.