first let me say I read every post in this thread before replying...
Ace - I am sorry to hear about your friends stricken with such problems.
Two years ago my father jogged a marathon. Two weeks yesterday ago he went to walk the dog in the morning and never made it back to the house. Dad was dealing with a rapidly onsetting Parkinson's. He had tremors in his hand and arms. He couldn't play cards any more, which he loved. A lifelong accountant, he was the student accounts manager at a nearby liberal arts college. The weekend before he and mom had made the decision that instead of waiting to the end of the school year he was going to give two weeks notice for his retirement that day. Sometimes he could walk right - he would just shuffle.
Turns out that inspite of a decade worth of clean cardio-vascular records dad hed big blood clots around his lungs. One of them broke away and sent my father's heart into some wild arithmea that took from us faster than you can blink.
God I miss my Dad.............
Any way who knows what brings some of these things on. My Dad was 67. My Grandfather lived to 98 and that included working in aircraft factories during WWII.
I do industrial work. I used to run a steam loco in tourist service. Last time I had to list on the chemicals I been exposed to I needed another piece of paper. Supposedly my health is fine.
As to the large amounts of metal dust.. any inhalition of solid particles is bad for you, some worse than others. Metal from grinding can be particularly bad because the odd shape solid particles get lodged inthe lungs and there is no way for the body to reject them. However there is also no known mechanism for the body to break done these solid particules that would allow an elements contained in them to get into the blood stream. My dad was an office guy. He was exposed to primarly to flourescent lights and bad coffee. Yet Parkinsons was forcing him to retire before something else took him away.
I haven't observed the big clouds of dust your talking about but I have seen rails worn to the web. Also I know several tourist railroads still use cast shoes because composite ones have their one emissions - they stink.
Oh heck I forget the question. I just miss my Dad.