I'm on my phone in a Dr. Office waiting on someone then heading to my kids graduation so a faster follow up as I won't be home til late is Google " coal slag health issues ". Lots of discussion on the topic. Hope it will be informative.
I wouldn't say Cory barbel is debunked as a cause hasn't even been found. For me its simple logic. Drag a body part of yours over substrate 24/7 and see if any of your skin is missing lol I'm sure there will be some.
I'm not into the image, but into the hobby...