Inhibition of hyphal growth of the fungus Alternaria alternata by chlorine dioxide gas at very low concentrations

Abstract

The efficacy of chlorine dioxide (ClO2) gas at very low concentrations for hyphal growth of Alternaria alternata related to fungal allergy was evaluated using a fungus detector. The fungus detector is a plastic sheet with a drop of spore-suspending medium, and it makes possible clear observations of hyphal growth with a light microscope. ClO2 gas (average 0.075 ppm, 0.21 μg/l) inhibited hyphal growth of the fungus, but not germination of fungal spores. The hyphal length was more than 1780 μm under air conditions (control) and 49±17 μm under ClO2 gas conditions for 72 h. According to the international chemical safety card, threshold limit values for ClO2 gas are 0.1 ppm as an 8-h timeweight average and 0.3 ppm as a 15 min short-term exposure limit. From these data, we propose that treatment with ClO2 gas at very low concentrations in space is a useful tool for the growth inhibition of fungi in the fields of food, medicine, etc. without adverse effects. © 2007 The Pharmaceutical Society of Japan.