Have forgotten much I once knew about it, but silicosis is a close relative of both asbestosis, and black lung disease. The problem is that when certain elements/substances are enabled to reach the fine powder state, that those little particles hit your lungs at top speed when you inhale. They stick there like tiny little spears. Eventually, they simply destroy your lungs, if enough is breathed. Some people are much more sensitive than others. Asbestos has the unique ability to cause mesothelioma, a specific cancer. It is always fatal. Don't know that coal or silica do that number, but as Chiro75 said, they can cause cancers.
I'd strongly suggest using respirators. A lot of pipefitters who worked outdoors all the time, like at refineries, have suffered from all the possible diseases that asbestos can cause.
I'd also suggest that you all demand MSDS sheets on all substances that you intend to grind. Am not certain of the laws governing natural substances, but they sure as hell are required if selling manufactured substances. I'd hate to see anyone get the sort of problems that typically result in lawsuits, filed by survivors usually.
(The following was told to me by a number of people when I was working as a workers compensation investigator. I have no objective proof.) It might interest you to know that back in the days before the Gulf War, when Reagan was still Prez, he deemed it politically necessary to get the USS Missouri battle ready ASAP. Had to have another battle wagon on the seas. The shipyard in Bremerton, WA, refused to relax their asbestosis rules. So, the boat was taken to Long Beach. Some people from Bremerton went down there to work. People I've talked to said that asbestos particles were like "snow" during the retrofit/upgrade, or whatever, that the dangers of the substance were largely ignored.
It'll take another 15-20 years, but if this is true, the victims of politics will start filing workers comp claims. There was no justifiable excuse this time. We knew how dangerous asbestos was. Didn't have much use for Reagan before I learned that. Have had none since.
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Asi es la vida
Bugs
[This message has been edited by Bugs3x (edited 06-21-2001).]