Hydrofluoric Acid Link
Eight tons of HF were released in South Korea. HF can be absorbed into the blood stream and catalytically dissolve bones. It’s treatable but very painful.
As an undergrad, I worked in a lab that had a 20L rusted and decaying canister of HF gas. Taped next to that canister was a page ripped from a physician’s reference. The page indicated that the recommended treatment for a patient that had more than 70% dermal exposure was a steady stream of morphine until the patient succumbed to the exposure. I was 19. I worked alone at night four feet from that canister. Good times.