system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 What makes asbestos so toxic to humans and why was it commonly used in the past?
gpt
It was commonly used because we did not realize how toxic it is. And it won't burn.

The asbestos fibers are extremely fine and they have sharp edges that will micro cut the lungs. The small size allows them to get deep into the lungs. and the multiple cuts lead to scar tissue etc. that eventually prevents the lungs from working.

We just did not know any better.