The footage has a lot of NSFW language, so just watch out for that. Within that thread there's some good discussion about some of the compounds that are being released into the air, and it is indeed very grim.
Interestingly here in Australia, I've heard about it a lot more in traditional media than my American friends seem to be hearing.
https://www.reddit.com/r/interestingasfuck/comments/110nlai/...
The derailment is, no doubt, a serious public health crisis. However, it helps no-one to spread misleading videos and commentary.
The wave of panic in the thread you posted is a stark example of "fake news" in action. A sign of the times, I suppose.
https://www.wfmj.com/story/48362031/fifth-negligence-suit-wo...
https://twitter.com/Justice314Lady/status/162347826755341107...
All companies will do that. The reason rail companies can do this so ruthlessly and recklessly is complete lack of competition and exceedingly generous industry deregulation.