OK, here's a link to the MSDS:
http://avogadro.chem.iastate.edu/MSDS/KNO3.htmHere are some of the potential health effects:
Eye: May cause eye irritation.
Skin: Dust causes mechanical irritation. Low hazard for usual industrial handling.
Ingestion: Causes gastrointestinal irritation with nausea, vomiting and diarrhea.
Inhalation: May cause respiratory tract irritation. May cause methemoglobinemia, cyanosis, convulsions, tachycardia, dyspnea (labored breathing), and death.
Chronic: Prolonged exposure may cause anemia and methemoglobinemia, characterized by dizziness, drowsiness, headache, breath shortness, cyanosis (bluish skin due to deficient oxygenation of the blood), rapid heart rate and chocolate-brown colored blood. May cause kidney injury. May cause methemoglobinemia, which is characterized by chocolate-brown colored blood, headache, weakness, dizziness, breath shortness, cyanosis (bluish skin due to deficient oxygenation of blood), rapid heart rate, unconsciousness and possible death.
Hey, that ain't bad. Death is only mentioned a couple of times. In the meanwhile you get to cough, puke, crap, have convulsions and a heart attack, fall asleep and turn blue.