Adverse Human Health Effects Associated with Molds in the Indoor Environment

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  • 4 February 2015 Create Date
  • 25 September 2019 Last Updated

In recent years, the growth of molds in home, school, and office environments has been cited as the cause of a wide variety of human ailments and disabilities. This evidence0based statement from the American College of Occupational and Environmental Medicine (ACOEM) discusses the current state of scientific knowledge as to the nature of fungal0 (mold0) related illnesses while emphasizing the possible relationships to indoor environments. Food0borne exposures, methods of exposure assessment, and mold remediation procedures are beyond the scope of this paper.
"Mold" is the common term for multicellular fungi that grow as a mat of intertwined microscopic filaments (hyphae). Many species of fungi live as commensal organisms in or on the surface of the human body. Exposure to molds and other fungi and their spores is unavoidable except when the most stringent of air filtration, isolation, and environmental sanitation measures are observed, e.g., in organ transplant isolation units.
Molds and other fungi may adversely affect human health through three processes: 1) allergy; 2) infection; or 3) toxicity. It is estimated that about 10% of the population has allergic antibodies to fungal antigens. Only half of these, or 5%, would be expected to show clinical illness. Furthermore, outdoor molds are generally more abundant and important in airway allergic disease than indoor molds — leaving the latter with an important, but minor overall role in allergic airway disease. Allergic responses are most commonly experienced as allergic asthma or allergic rhinitis ("hay fever";). A rare, but much more serious immune0related condition, hypersensitivity pneumonitis (HP), may follow exposure (usually occupational) to very high concentrations of fungal (and other microbial) proteins.
Most fungi generally are not pathogenic to healthy humans. A number of fungi commonly cause superficial infections involving the feet (tinea pedis), groin (tinea cruris), dry body skin (tinea corporis), or nails (tinea onychomycosis). A very limited number of pathogenic fungi — such as Blastomyces, Coccidioides, Cryptococcus, and Histoplasma — infect non0immunocompromised individuals. In contrast, persons with severely impaired immune function, e.g., cancer patients receiving chemotherapy, organ transplant patients receiving immunosuppressive drugs, AIDS patients, and patients with uncontrolled diabetes, are at significant risk for more severe opportunistic fungal infection.
Some species of fungi, including some molds, are known to be capable of producing secondary metabolites, or mycotoxins, some of which find a valuable clinical use, e.g., penicillin and cyclosporine. Serious veterinary and human mycotoxicoses have been documented following ingestion of foods heavily over0grown with molds. In agricultural settings, inhalation exposure to high concentrations of mixed organic dusts — which include bacteria, fungi, endotoxins, glucans, and mycotoxins — is associated with organic dust toxic syndrome, an acute febrile illness. Present concern over human exposure to molds in the indoor environment appears to derive from a belief that inhalation exposures to mycotoxins cause numerous and varied, but generally nonspecific, symptoms.
There is scientific evidence that in certain cases, molds and other fungi may adversely affect human health, and mold has been associated with health issues ranging from coughs to asthma to allergic rhinitis. However, current scientific evidence does not support the existence of a causal relationship between inhaled mycotoxins in the home, school, or office environment and adverse human health effects. An evaluation of the relevant literature follows.

Adverse Human Health Effects Associated with Molds in the Indoor Environment