I was a miner for two years, starting as a boy of 16 in 1957. There were no ponies in my colliery, but there was one in the training colliery that new miners had to attend. It was a mischievous devil, and loved to rip the buttons off your clothes with its teeth. It was a glutton for work, for sandwiches, and for company. It had no problem seeing, and we were told it enjoyed its time on the 'bank,' as the surface is called, but was always ready to come back below because it missed the company.

Robomatic: Later on I was an insurance agent in the same town. Coaldust affects the lungs by 'setting' in them and reducing their function. This was called Pneumoconiosis, and it leads to death in the same way that Emphysema does, by not allowing the sufferer to breathe and making them vulnerable to other infections.

I've never heard of coaldust affecting the eyes or mucous membranes in humans, but I'm not a doctor. It possibly could affect horses, in that they haven't hands to remove FBs in the eye, and are more philosophical about them than humans.

On the health issue, at that time, to reduce the risk of explosion from the coaldust (and it does!) stonedust had for years been spread in the mines. This led to a condition called Silicosis, where particles lodged in the lungs in quantity, and abraded the lungs internally. An unpleasant thing to die from, as is Pneumoconiosis.
Ever miner's Death Certificate I handled, about 35 of them, listed lung problems as a contributing factor.

Miners did spend twice as long in the mines as ponies, as they live thrice as long. Ponies were stabled on the intake side of the ventilation system.
What was done about it? Don't know about now, but precious little then. Smoking was strictly forbidden, in those days when everyone smoked, miners used snuff and chewed tobacco. They would cause to be sacked anyone who smoked down the pit. Miners going on shift would be patted down in a formal search for smoking equipment, which was mainly a reminder, because if you smoked down there, your mates would have you OUT. Industrial diseases were then regarded as occupational hazards.
I enjoyed mining as much as I've enjoyed any job I've had. As a boy, I didn't get into the serious stuff, Stripping and Ripping. I was a Jig Runner and a Ring Dragger.
I'm not kidding. I'll leave you to guess what those occupations were.