Mycotoxins, Endotoxins & Bioaerosols

Exponent’s takes a multidisciplinary approach to investigate suspected sources of bioaerosol exposure. Our Certified Industrial Hygienists sample bulk materials, surfaces, water, or air for evidence of problematic agents, and to evaluate operating practices that may give rise to unusual exposures. Our process engineers and air dispersion modelers evaluate the pathways and potential magnitude of bioaerosol exposures. Exponent also has toxicologists and physicians to interpret the findings with respect to human health hazards and to evaluate evidence of disease causation from bioaerosol exposures.

Bioaerosols and Their Importance in the Environment

‘Bioaerosol’ is a term used to describe airborne particles that are living or originate from living organisms, such as plant pollens, fungal spores, microorganisms and associated fragments, chemicals, or waste products. Bioaerosols are ubiquitous in many human environments and may contain a diverse array of allergenic, toxigenic, or infectious agents ranging in size from submicroscopic (< 0.01 microns) to visible (e.g., 100 microns or 1 millimeter).

Indoor and outdoor environments can foster the growth and emission of bioaerosols capable of causing allergic responses in sensitized individuals. These bioaerosols also may be associated with unpleasant odors, mucous membrane irritation responses, and a risk of serious infections or other adverse health outcomes in certain exposed individuals. Examples of more serious outcomes that may result from bioaerosols include Legionnaire’s Disease from Legionella infection, Broncho-Pulmonary Aspergillosis from Aspergillus infection, Valley Fever from a soil fungus, and Hypersensitivity Pneumonitis from exposure to bird guano dusts. Source environments for potentially harmful bioaerosols may result from poor management of water intrusion, floods, or damp environments, sewage spills, poor sanitation, consumption of contaminated foods, contamination of surfaces or water sources, the disruption of soil containing the Valley Fever fungi (Coccididioidies immitis), and inadequate safeguards taken in managing domestic and agricultural wastes.

Bioaerosols may also contain mycotoxins and endotoxins. Mycotoxins are fungal byproducts comparable to antibiotics like penicillin, but many have potential toxicity to humans with no beneficial properties. Endotoxins are bacterial membrane fragments recognized as infectious agents by the human immune system and can lead to severe inflammatory responses. For example, bioaerosols generated from managing livestock wastes or grain dusts may contain elevated concentrations of mycotoxins and/or endotoxins that, under unusual circumstances, can cause obstructive lung disease after sufficiently high chronic exposures.

The following are example publications by Exponent staff relating to investigation of bioaerosols and associated diseases:


Hicks, JB, Lu, ET, DeGuzman, R, and Weingart, M. 2005. Fungal types and concentrations from settled dust in normal residences. J. Occup. Environ. Hyg 2: 481-492.


Fedoruk J, Miller JD. Health effects of bioaerosols. In: Field Guide for the Determination of Biological Contaminants in Environmental Samples, 2nd edition. Hung LL, Miller JD, Dillon HK (eds), American Industrial Hygiene Association, Fairfax, VA, 2005.

Fedoruk M, Uhlman S, Baker D, Yang H. Analysis of microbial contamination of a ventilation system detected by measurement of microbial volatile organic compounds. pp. 386–395. In: Bioaerosols, Fungi, and Mycotoxins: Health Effects, Assessment, Prevention and Control. Johanning E (ed), Boyd Printing Company, Inc., New York, NY, 1999.

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