Facts about Fungal Fragments

Editor’s Note: Mold spores are not the only concern, scientists say. Tinier pieces of mold called “fungal fragments” may be deeply inhaled and cause problems. The content below is from the CDC:


Exposure to fungi, particularly in water damaged indoor environments has been thought to exacerbate a number of adverse health effects including subjective symptoms such as fatigue, cognitive difficulties and problems with memory, to more definable diseases such as allergy, asthma and hypersensitivity pneumonitis. Understanding the role of fungal exposure in these environments has been limited by methodological difficulties in enumerating and identifying fungi in environmental air samples. Consequently, data on personal exposure and sensitization to fungal allergens has been restricted to the spores of a few select and easily identifiable species.


Fungal fragments

  • Derived from fragmented conidia or hyphae
  • Fungal fragments are categorized into two groups depending on the analysis used:

1. Submicron fungal fragments <1 micron

2. Larger fungal fragments >1 micron

  • Identification in environmental samples is complex and subjective.

The contribution of airborne spores, hyphae and fungal fragments of other genera to exposure and allergic sensitization are poorly characterized. There is increased interest in the role of aerosolized fungal fragments following reports that the combination of hyphal fragments and spore counts improved the association with asthma severity. Such fragments are categorized as either sub-micronic (less than one micron) particles or larger fungal fragments. In vitro studies have shown that sub-micronic particles of several fungal species are aerosolized in much higher concentrations (300-500 times) compared to spores, and that respiratory deposition models suggest that particles of Stachybotrys chartarum may be deposited 230-250 fold higher than spores.


The practical implications of these models are yet to be determined for actual human exposures … These findings highlight the contribution of larger fungal fragments as aeroallergen sources and present a new paradigm of fungal exposure.


Direct evidence of the associations between fungal fragments and building-related disease is lacking and in order to gain a better understanding, it will be necessary to develop diagnostic reagents and detection methods, particularly for sub-micronic particles. Monoclonal antibody-based assays enable the measurement of individual antigens but interpretation can be confounded by cross-reactivity between fungal species. The recent development of species-specific monoclonal antibodies, used in combination with a fluorescent-confocal HIA technique should, for the first time, enable the speciation of morphologically indiscernible fungal fragments. The application of this method will help to characterize the contribution of fungal fragments to adverse health effects due to fungi.


Fungi Are a Diverse Kingdom

  • 80,000 species known
  • More than 112 fungal genera identified as allergenic
  • Relationship between fungal exposure and clinical outcomes remains unclear
  • Measurement of exposure to fungal allergens has been restricted to the spores of a select number of fungi
  • The potential of different fungi or fragments to cause or aggravate adverse health effects remains unclear
  • No consensus on thresholds for specific risks.


  • Numbers of fungal fragments are in most cases more common than airborne spores.
  • Larger fungal fragments are a significant aeroallergen source, presenting a new paradigm of natural fungal exposure.
  • Currently, the airborne distribution and immunoreactivity of smaller submicron fungal fragments remains unknown.
  • The development of innovative immunodetection methods will help to elucidate adverse health effects due to smaller fungal fragments in the environment.

Source: Airborne Fungal Fragments and Allergenicity; Brett J. Green, PhD;
National Institute for Occupational Safety and Health; Centers for Disease Control and Prevention; Morgantown, WV.

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