Academic journal article Central European Journal of Public Health

Effect of Water Activity and Titania P25 Photocatalyst on Inactivation of Pathogenic Fungi - Contribution to the Protection of Public Health

Academic journal article Central European Journal of Public Health

Effect of Water Activity and Titania P25 Photocatalyst on Inactivation of Pathogenic Fungi - Contribution to the Protection of Public Health

Article excerpt

INTRODUCTION

Microscopic mould fungi are ubiquitous in both indoors and outdoors environments. Approximately 500 fungal species have been described as human pathogens (1). For the recent twenty years an extensive attention has been paid to the potentially pathogenic fungi, which may occur in the indoor environment of flats, offices, schools, kindergartens, etc. It has been noticed that the influence of systematic human exposure to their spores results in increase of allergies, asthma, respiratory problems as well as mycoses in the lungs or on the skin. The infants, children, persons with suppressed immune systems, patients under steroid or chemotherapy treatment are the main groups at risk (2-4). The composition of fungi in the indoor environment depends on various factors, such as temperature, relative humidity, physical and chemical properties of the technical materials, and dust contaminants (3). Because mould grows best in damp and environments damaged by water, e.g. flooded buildings, the water activity of materials may be the most important factor in controlling mildew. The water activity is defined as the ratio of the vapour pressure of water in a material (p) to the vapour pressure of pure water (po) at the same temperature. Pure distilled water has a water activity of exactly one (5).

People may be exposed to mould either through inhalation or by skin contact with contaminated dust, and thus a certain level of exposure is inevitable. Controlling the level of moisture of technical materials and drying of their surfaces by mechanical, physical and chemical methods can limit microbial growth. Thought, the chemical compounds used for mould inhibition are quite effective for short-term antimicrobial purposes, their application is risky since they are often toxic. In recent years, numerous ecological and environmentally friendly methods have been extensively studied for the removal of various biological pollutants from air, water, wastewater and surfaces of technical materials. Among them photocatalytic oxidation on titanium dioxide is one of the best known. TiO2 has been widely used for water disinfection, wastewater treatment, air deodorization, self-cleaning and self-sterilizing surfaces (6, 7). However, the majority of studies on the antimicrobial activity of titanium dioxide were performed for bacteria and yeast (8-10). There are only a few studies focusing on the photocatalytic removal of potentially pathogenic fungi since they are much more persistent than simple bacteria organisms (11-13).

The aim of the study was to examine the influence of titania (titanium dioxide, TiO2) activated by indoor light and water activity on few species of potentially pathogenic fungi. Aspergillus sp. is genus consisting of several hundred species found in various climate zones. A. versicolor, A. flavus and A. fumigatus are frequently found in the food products such as stored cereals, hay, cheese, meat etc. A. fumigatus has secreted secondary metabolites (mycotoxins) such as 6-methoxysterigmatocystine and aversine, and has been also reported as a causative agent of cutaneous disease, bilateral toenail onychomycosis, osteomyelitis and many others (14). Black mould Stachybotrys chartarum is primarily isolated from cellulose-rich building materials (such as wallpaper, wood etc.) in damp and water-damaged buildings. Stachybotrys chartarum secrets neurotoxin, i.e., stachratoxin H, and is often connected with the Sick Building Syndrome (SBS) defined as the combination of symptoms associated with an individual's place of work or residence (15). Pseudallescheria boydii is a complex of species, e.g., Ascomycetes and also their products, such as asexual anamorphs, mainly Scedosporium. Species of Pseudallescheria sp. and Scedosporium sp. cause human scedosporiosis, a fungal disease difficult to treat with a high mortality rate (16, 17).

MATERIALS AND METHODS

The antifungal activity of TiO2 and water was investigated on standard Czapek Yeast Agar (CYA, BTL) using agar plate method. …

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