Mycotoxins (fungal or mold toxins)

From the World Health Organization in its report WHO Guidelines for Indoor Air Quality: Dampness and Mould, published July 16, 2009

2.3.5 Mycotoxins

Mycotoxins, or fungal toxins, are low-relative-molecular-mass biomolecules produced by fungi, some of which are toxic to animals and human beings. Mycotoxins are known to interfere with RNA synthesis and may cause DNA damage. Some fungal species may produce various mycotoxins, depending on the substrate. In the case of Penicillium, one such compound is penicillin, a strong antibiotic.

Several mycotoxins, e.g. aflatoxin from Aspergillus flavus and Aspergillus parasiticus, are potent carcinogens. Many mycotoxins are immunotoxic, but the trichothecene mycotoxins are immunostimulating at low doses (Eduard, 2006).

Numerous mycotoxins have been classified by their distinct chemical structures and reactive functional groups, including primary and secondary amines, hydroxyl or phenolic groups, lactams, carboxylic acids, and amides.

The mycotoxins that have perhaps received most attention are the trichothecenes, produced by Stachybotrys chartarum. Bloom et al. (2007) showed that several mycotoxins produced by S. chartarum and Aspergillus versicolor (i.e. macrocyclic trichothecenes, trichodermin, sterigmatocystin and satratoxin G) could be present in most samples of materials and settled dust from buildings with current or past damage from damp or water. Charpin-Kadouch et al. (2006) compared the levels of macrocyclic trichothecenes in samples from 15 flooded dwellings known to be contaminated with S. chartarum or Chaetomium, and a group of nine dwellings without visible mould. The level of macrocyclic trichothecenes was significantly higher in floor dust from the mouldy houses than from the reference dwellings; the levels in wall samples from mouldy houses were also higher (of borderline statistical significance), but no statistically significant difference in air concentrations was observed. In a study by Brasel et al. (2005a) in seven buildings known to be contaminated with S. chartarum, the airborne level of macrocyclic trichothecenes was significantly higher than that in four control buildings (i.e. with no detectable S. chartarum or history of water damage).

The same authors also showed that S. chartarum trichothecene mycotoxins can become airborne in association with both intact conidia and smaller fungal fragments (Brasel et al., 2005a,b). Sterigmatocystin was shown to aerosolize from a finishing material (Moularat, Robine, 2008), at an airflow rate of 100 cm/s and a relative humidity of 30%. These studies demonstrate that mycotoxins are present in the indoor environment and that the levels may be higher in buildings affected by mould or damp. It is still not clear, however, whether the levels of airborne mycotoxins in damp buildings are sufficiently high to cause adverse health effects (see section 4.2.2).