Aflatoxins in the soil ecosystem: an overview of its occurrence, fate, effects and future perspectives

Aflatoxins are secondary metabolites produced by specific strains of fungi, especially Aspergillus spp. These natural toxins are mainly found in soil, decaying vegetation and food storage systems and are particularly abundant during drought stress. Aflatoxin contamination is one of the most important threats to food safety and human health due to its toxic, mutagenic and carcinogenic properties. Therefore, most research focuses on post-harvest contamination of aflatoxins in feed and food commodities but very limited information is available about aflatoxin contamination and its toxicological consequences in the soil ecosystem. Current regulations provide minimal options for the disposal of aflatoxin-contaminated crops, amongst which is the incorporation of residues into the soil for natural degradation. This form of mycotoxin loading into the soil could potentially change its physicochemical characteristics and biotic parameters. Recent studies suggest that as climate conditions change, the occurrence and geographical distribution of aflatoxins might increase, posing significant health risks to the soil ecosystem, food crop production and human health. This review will focus on studies that look at the environmental and toxicological consequences of aflatoxin contamination with the aim of clarifying the risk that aflatoxin contamination poses to soil ecosystems. Many aspects of aflatoxin occurrence, degradation and the effects of its transformation products in the soil environment are still unknown and remain an important area of research for soil health and productivity. A climatic approach, in terms of changes in soil moisture and air temperature, is important for future risk assessments of aflatoxin contamination.