The FDA’s mold guide talks about mold basics, cleanup and provides guidelines for how to clean up mold once you’ve been infested. The guide is available as a .pdf file English and Spanish Although the document presents recommendations, it also comes with a warning that the EPA does not regulate standards regarding the concentration of mold or mold spores in indoor air. This is probably because there is significant litigation involved as well as controversy as to how the degree of effect mold has on individuals.
Part of the problem might be traced to the terminology. Mold itself is not necessarily toxic, though there is a black mold which is “named” toxic. The real toxin in mold is a product called mycotoxin, a substance produced by many molds. Mycotoxins cause allergic reactions to many if not most people when they are exposed to them; but mycotoxins are most severely toxic to infants, the elderly or infirm and individuals with breathing problems such as pneumonia. However, most people exposed to high levels of mold develop sensitivity (allergies) so the controversy should really be a moot point. No one is immune.