Toxic molds are a major source of concern among many people in North America today.
One of the very few really "toxic" molds can be easily recognized as that "black stuff" that grows on constantly-wet areas inside a building. However, it does require a constant drip to keep it alive, and fortunately, its spores are so heavy that they don't blow too far. This type of thing is easily spotted and remedied. There are, of course, hundreds of other types of molds, most of which aren't toxic - the type that grows on bread, cheese, etc., and various types of penicillin. Of course, many people are allergic to otherwise harmless molds, and for some these can be toxic.