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.