Exposure to Mold and Mycotoxins

The medical literature is sparse in regard to mold exposures and respiratory illness in agricultural workers. Sources of mold dust exposure in agricultural areas include hay, grain, silage, and bedding. Baled hay and straw have been found to contain and liberate the largest amounts of microbes such as mesophilic bacteria, xerophilic fungi, mesophilic fungi, thermotolerant fungi, and thermophilic actinomycetes. Hay, except when dried in storage, liberates great numbers of fungal spores (139).

Seasonal variability is an important factor in characterizing the amount and type of microbes in specific farm areas. A study showed a decreased amount of microbial contaminants during summer seasons in swine confinement areas. Another study in a turkey confinement house in Minnesota found the highest concentration of aspergillus (a fungal respiratory disease agent), dust, and ammonia in the winter months (140,141).

Inhalation of dust from complex organic materials may result in acute respiratory tract illness. Possible mechanisms include toxic and cellular reactions to microbial and other organic products or immunological responses after prior sensitization to an antigen. Mold exposure results in production of specific IgE and IgG in the lung. However, aside from the specific IgE and IgG responses, the in-vivo reactions to mold inhalation are poorly understood. Furthermore, it has been difficult to distinguish the health effects of mold and mycotoxins from those of endotoxins and other components of complex organic dust exposures. In immunocompromised individuals, such as post-organ transplant or HIV-infected patients, the potential for invasive systemic disease with fungi such as aspergillus is possible (142,143).

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