There's a really interesting 99% Invisible episode about this very topic. https://99percentinvisible.org/article/beyond-biohazard-danger-symbols-cant-last-fore

There's a really interesting 99% Invisible episode about this very topic. https://99percentinvisible.org/article/beyond-biohazard-danger-symbols-cant-last-forever/ https://99percentinvisible.org/article/beyond-biohazard-dang...