I always thought it was the yellow smoke was the worst. Yellow smoke was Chlorine gas which is super toxic nerve agent. There was a power plant on a lake not too far away and they used chlorine gas to treat the boiler feed water before introduction to the boiler feed water. They had a fitting break while changing a cylinder and the yellow vapor drifted across the lake and fish were going belly up in the intake for condenser feed water. The guys changing the cylinders were wearing "Space Suits" and were not harmed. The landscape around the area looked like it had been sprayed with Round-up. It smelled like a pool that had been shock treated.