Claims of injuries are usually based on exposure through  breathing in, or skin contact with, the airborne contaminants emitted by toxic mold.

Molds that produce toxins and allergens naturally occur in the environment-- both outside and inside buildings. Evaluating toxigenic or allergenic mold in a building is based on comparing the inside environment with both the outdoors and other interior areas. The comparison is of both the amount of organic materials in the air and their composition.