system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why are so many flame retardants toxic?

Asbestos, PCBs, Fiberglass. All of these flame retardants are dangerous and were widely used in their time. Why are so many common flame retardants dangerous?
gpt
Because the structures that give you resistance to flame are microscopic needles that can get caught in your eyes, mouth, lungs, and other important body parts.

The reason microscopic needles are flame retardant is that you're trying to maximize the amount of air in between any individual piece of material. The best would be to have an aerogel, but those are expensive, so you use the fluffiest piece of glass you can, and those often have tiny needles.