Astronomy

No, actually. Metal doesn't burn up, it melts to slag and disintegrates, but the metal particles don't become gas the way carbon does. Then you just have a bunch of a space debris and reactive, aerosolized metal particles knocking around the upper atmostphere. Aluminum Oxide ash can float to the ground, or it can cause ozone decomposition. We're not entirely sure which is worse based on the amount coming back from satellites, but the number of satellites we're sending up is increasing rapidly. So it wouldn't hurt if they were a little less toxic.

For the most part, yes. The problem is pollution, like aluminum oxide.

Here is an article that explains better than I ever could: https://www.space.com/air-pollution-reentering-space-junk-detected