Evaluation of Aflatoxin-Producing Fungi in Indoor Air of Warehouses and Houses of Farmers in Giwa, Kaduna State Nigeria

The health risks associated with ingesting food contaminated with mycotoxins, particularly aflatoxin-contaminated staple foods like maize and other cereals, have been widely studied. However, there is little knowledge about the role of inhalation of pathogenic fungi as bioaerosols in contaminated air from handling crops as an occupational health risk. This paper presents a study aimed at determining the level of airborne aflatoxin-producing fungi in the indoor air of grain stores in the Giwa community of Kaduna State. Indoor air was sampled using the settling plate technique from grain stores, warehouses and living rooms. Metrological data of the studied area were collected from the Institute of Agricultural Research, ABU, Zaria. Airborne mycofloral concentrations were determined, and colonies of Aspergillus flavus were identified. The isolates were screened for aflatoxin production on Neutral Red Desiccated Coconut Agar (NRDCA). Selected aflatoxin-producing fungal isolates were screened for the presence of aflD (nor-1), aflM (ver-1) and AflR genes by PCR. Sampling was done once every month from October to December 2020. Mycofloral concentrations were in the range of 2.77x103−4.05x103 and 1.55x103−2.17x103CFUm-3for grain stores and living rooms respectively. A total of twelve (12) strains of A. flavus were isolated from the indoor air of the grain stores and warehouses while none was obtained from the living room. Eleven (11) isolates were confirmed to be aflatoxigenic on NRDCA, presenting 30 CFUm-3 of the indoor air mycofloral composition. The aflD, aflM and aflR were amplified with aflD being the most detected gene from all the aflatoxin-producing mould isolates of Aspergillus species. The mycofloral concentrations in the grain stores were higher than those in the living room and, in all the sampling sites, exceeded the limit of the total mycofloral concentration of 500 CFUm-3 for agricultural and industrial environments. There were significant differences (p<0.05) in the indoor mycofloral concentrations between the grain stores/warehouses and the living room. The presence of aflatoxigenic strains of A. flavus in the stores indicates that grain handlers and traders are at risk of occupational exposure to aflatoxigenic fungi and aflatoxins. Hence, they should wear protective materials for their safety while working in such stores.