engleski

Adverse effects of exposure to airborne fungi in indoor environments

Airborne fungi have been incriminated to cause several respiratory disorders based on different immunological and toxic pathways including hypersensitivity pneumonitis, asthma, rhinitis, chronic bronchitis and organic dust toxic syndrome. Mycotoxins in fungal spores have been proposed to cause adverse health effects particularly after chronic exposure to high levels of airborne fungi in indoor environments. Recent study (January 2012-November 2012) taken in grain mill (GM), apartments, and basements (Zagreb, Croatia) showed that average concentration of airborne fungi in GM was about 30 times higher (up to 40000 cfu/m3) than in other locations (up to 1244 cfu/m3). At GM species of Aspergillus, Penicillium and Eurotium dominated over other detected airborne fungi. Among Aspergilli and Eurotia, A. ochraceus and E. herbariorum were constantly present in the samples taken at GM. Aspergillus ochraceus (AO) is well-known producer of ochratoxin A (OTA) and Eurotium herbariorum (EH) produces a wide range of metabolites with poorly investigated toxicity. In the current investigation OTA was detected (HPLC, immunoaffinity columns) in spore extracts (0.3-28 µg/mL) of 5/6 AO strains isolated in November 2012, while none of tested EH strains were able to produce OTA. Taking into account maximum detected concentration of OTA in the spores, daily intakes of OTA by inhalation were calculated to be 0.08 and 3 ng/kg b.w., which is below the tolerable daily intake of OTA (17 ng/kg b.w.). Cytotoxicity of pure OTA, OTA-positive (AO-OTA+) and OTA- negative (AO-OTA-) spore extracts, as well as spore extract of EH, was tested on human lung adenocarcinoma cells A549, individually and in combination, using colorimetric MTT test (570 nm). Concentrations that decreased the cell viability by 50% (IC50) were as it follows: pure OTA (53 μg/mL) ; AO-OTA+ (mass concentration 934 μg/mL corresponds to 10.5 μg/mL of OTA in spore extract) ; and 2126 μg/mL for EH. Highest applied concentration of AO-OTA- spore extract (4940 g/mL) decreased cell viability by 30% and IC50 for the extract could not be determined. Combinations EH + AO-OTA+ and EH + AO-OTA- applied in subtoxic concentrations showed dominant additive interactions. Also, synergistic effect was obtained for one combination of EH and AO- OTA+. Despite the low calculated daily intake of OTA by inhalation, chronic exposure to high levels of OTA-producing airborne fungi in combination with other more or less toxic moulds pose significant threat to human health due to their possible additive and/or synergistic interactions.

Ochartoxin A; A. ocharceus; Eurotium; cytotoxic synergism

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