Courtesy of Daily Timewaster, here's a fascinating video clip showing passing steam trains setting fire to coal dust in the air as they pass a coal mine in China. The last couple of trains, in the deepest darkness, produce the most spectacular effects. I highly recommend watching it in full-screen mode.
It's unnerving to think that anywhere from hundreds to thousands of people - workers at the coal mine, those passing on the railway line, and families living in the area - actually breathe that dust every day, just by being nearby. I wonder what their lungs look like?
(On the other hand, perhaps it's best not to know!)