Detection of Airborne Stachybotrys chartarum Macrocyclic Trichothecene Mycotoxins on Particulates Smaller than Conidia

Highly respirable particles (diameter, <1 m) constitute the majority of particulate matter found in indoor air. It is hypothesized that these particles serve as carriers for toxic compounds, specifically the compounds produced by molds in water-damaged buildings. The presence of airborne Stachybotrys chartarum trichothecene mycotoxins on particles smaller than conidia (e.g., fungal fragments) was therefore investigated. Cellulose ceiling tiles with confluent Stachybotrys growth were placed in gas-drying containers through which filtered air was passed. Exiting particulates were collected by using a series of polycarbonate membrane filters with decreasing pore sizes. Scanning electron microscopy was employed to determine the presence of conidia on the filters. A competitive enzyme-linked immunosorbent assay (ELISA) specific for macrocyclic trichothecenes was used to analyze filter extracts. Cross-reactivity to various mycotoxins was examined to confirm the specificity. Statistically significant (P < 0.05) ELISA binding was observed primarily for macrocyclic trichothecenes at concentrations of 50 and 5 ng/ml and 500 pg/ml (58.4 to 83.5% inhibition). Of the remaining toxins tested, only verrucarol and diacetylverrucarol (nonmacrocyclic trichothecenes) demonstrated significant binding (18.2 and 51.7% inhibition, respectively) and then only at high concentrations. The results showed that extracts from conidium-free filters demonstrated statistically significant (P < 0.05) antibody binding that increased with sampling time (38.4 to 71.9% inhibition, representing a range of 0.5 to 4.0 ng/ml). High-performance liquid chromatography analysis suggested the presence of satratoxin H in conidium-free filter extracts. These data show that S. chartarum trichothecene mycotoxins can become airborne in association with intact conidia or smaller particles. These findings may have important implications for indoor air quality assessment. The World Health Organization made the first attempt to define sick building syndrome (SBS) in 1982. SBS has proven to be difficult to define, and no single cause has ever been identified (2, 34). The complaints associated with poor indoor air quality (IAQ) range in severity and include difficulty in breathing, headaches, watering of the eyes, and flu-like symptoms, but they are not limited to these complaints (35). Numerous research groups have tried to determine the underlying cause(s) of SBS and poor IAQ. Fungi and their secondary metabolites, such as mycotoxins, are hypothesized contributors that have been closely examined (3, 5, 6, 9, 18, 21). The fungi isolated from buildings with poor IAQ include a wide variety of genera and species. Recent research has shown that, along with airborne conidia, highly respirable fungal fragments can lead to human exposure because the fragments can be aerosolized simultaneously with conidia. The amounts of these fragments could be as large as 320 times the amounts of conidia (16). Kildeso et al. (29) claimed that for a typical spore size (diameter, 3 m; density, 1 g/cm 3 ) the average exposure to spores may be approximately 0.14 g/m 3 . Expanding on previous studies which concluded that the average concentration of respirable particles in a typical Danish office building was approximately 50 g/m 3 of air (28), conidia could be only a small fraction of the potential particulates (possibly less than 1%) in contaminated buildings. This suggests that fungal fragments