Some substances are more toxic than others. The toxicity of a substance is described by the types of effects it causes and its potency. 1  Types of Effects: Different chemicals cause different effects.
I think I remember reading that injured means bruises and lascerations, seriously injured meant hospital but not life threatening, critically injured meant hospital ICU time and fatally injured meant injuries leading to dying sometime later.
1 An accident, especially one involving serious injury or loss of life. 2  One who is injured or killed in an accident: a train wreck with many casualties.  One who is injured, killed, captured, or missing in action through engagement with an enemy: Battlefield casualties were high.