A Study of Aflatoxin Production by Aspergillus Flavus Growing on Wallboard

Abstract

The potential for exposure to mycotoxins in indoor environments is of increasing concern. In order to evaluate the potential for mycotoxin production by toxigenic fungi growing on waterdamaged building materials, two aflatoxin producing strains of Aspergillus f1avus (American Type Culture Collection 16875 and 15547) were inoculated onto culture media, plain wallboard, and vinyl wallpapered wallboard (cellulose-based and wheatbased wallpaper paste) and incubated at high relative humidity and room temperature for up to 16 weeks. Each sample was extracted with 60% methanol and aflatoxins in the crude extract were collected by immunoaffinity chromatography and quantified by fluorometry. Analysis by high performance liquid chromatography was performed for confirmation. Varying degrees of fungal growth were evident on all tested substrate types. Up to 4800 ppb of aflatoxin was detected when strain ATCC 16875 was grown on potato dextrose agar. However, when inoculation was standardized to minimize initial aflatoxin concentration in the inoculum, aflatoxin production was not detected on any wallboard sample under any of the incubation conditions provided. The presence of a toxigenic fungal strain on an indoor substrate does not necessarily indicate that the fungus is producing mycotoxins and our data provide evidence that wet wallboard is unlikely to provide appropriate conditions for aflatoxin production.

Antifungal action of Pichia anomala against aflatoxigenic Aspergillus flavus and its application as a feed supplement

“…The production of aflatoxin by A. flavus is conditional and depends on many genetic and physiological factors . Only some A. flavus strains have the genetic capability to produce aflatoxin (designated as toxigenic).…”

A Study of the Toxicity of Moulds Isolated from Dwellings

“…Aspergillus flavus proved to be a highly toxin-producing strain, producing as many as nine toxic compounds on MEA, while on both building materials, it retained the capacity to produce aflatoxin B1, G1 and 3-nitropropionic acid on gypsum board. There had been previous indications of the possibility of growth of A. flavus on building materials, but its capacity to produce aflatoxins on such materials had been ruled out [12,31,32]. The high cytotoxicity of A. flavus extract on mouse fibroblasts confirmed the toxic properties of the strain.…”

Aflatoxin production and in vitro toxicity of Aspergilli section Flavi isolated from air samples collected from different environments

“…In the same study, the presence of aflatoxigenic strains was only confirmed in an outdoor air sample from one of the poultry units but direct evidence of the poultry workers' professional exposure to AFB 1 was found in 58% of positive serum samples (mean 2 ng/ml) in contrast to the AFB 1 -negative serum sampled from control individuals. On the other hand, in living environments, AFB 1 does not seem to be relevant since its formation on building materials during fungal growth has not been detected (Rao 2016;Ren 1999). Our results suggest that a serious threat to human health due to exposure to airborne A. flavus could come only in occupational environments, such as grain mill facilities, but not from exposure in urban apartments and basements.…”