What this video covers
The clip covers mycotoxins, which are chemicals certain molds produce rather than the spores themselves.
Compounds from species including Stachybotrys and Aspergillus have been associated with neurological symptoms in the literature. The mechanism discussed is that some of these molecules are small enough to cross the blood brain barrier.
The takeaway
Spore counts and mycotoxin exposure are different questions. A building can test acceptably for airborne spores while the occupants are reacting to something the standard test does not measure.
Read the full written guide: Mycotoxins and Brain Health.