Is this an anthrax attack??
Wouldn’t affect someone that fast... Perhaps the respiratory distress is from being freaked out about being exposed to a white, powdery substance?
Sounds like cyanide exposure to me. The blue skin comes from the inability of the blood to carry oxygen. Both sodium cyanide and potassium cyanide are common industrial chemicals and are white (I’m sure about NaCN being white). That said, there are a lot of other chemicals with similar effects.