IAQ and Human Toxicosis: Empirical Evidence and Theory

Harriet M. Ammann, Ph.D., D.A.B.T.

Washington State Department of Health, e-mail: HMA0303@doh.wa.gov

Studies of injury, illness and death occurring in mold-exposed animals and people in the field, observe that the illness called mycotoxicosis results from more complex exposures than can be observed in laboratory experiments with pure mold toxins. Response in field exposures occurs at lower exposure concentrations than those from controlled experiments. Occurrence of signs and symptoms at low exposure levels may result from a number of factors, including a greater spectrum of susceptibility in heterogeneous populations, additive or synergistic actions of multiple toxins, actions of other toxic microbial compounds, allergic and irritant response, as well as concomitant exposure to other contaminants. Changes in the immune system, often reflected as increased susceptibility to infectious illness, are a common finding of low level exposure to toxigenic molds that inhibit protein synthesis. Changes in the immune system are extremely complex, but changes in the endocrine and nervous system accompany them, and may reflect changes in the central neuroendocrine-immune control system. Evaluation of illness of individuals exposed to a combination of irritant, allergenic and toxigenic biological contaminants in wet buildings requires more information about basic effects of individual agents as well as interactive effects of the complex mixtures. In the meantime, case definition for such illness needs to include exposure parameters that actually reflect the nature of the agents capable of effecting illness, rather than some isolated component such as a single mycotoxin. A definition of mycotoxicosis borrowed from agricultural animal and worker exposures, "illness resulting from exposure to one or more toxic molds and their products," could serve. A case definition should also include location of individuals relative to the location of suspect contaminants, time of contact with or exposure to molds and their products, and a list of signs and symptoms gleaned from investigations of known animal or human toxic exposures. Commonality of signs and symptoms in those who show similar time and place exposure parameters could be used to further focus definition of a case. Prudent public health practice recognizes the potency of the toxic agents produced by toxigenic molds, and seeks to protect occupants of buildings once moisture incursion with resultant microbial growth has been discovered.