Katherine A. Muñoz Sepúlveda

• Mycotoxins are secondary toxic metabolites synthesized by several species of filamentous fungi. Occurrence of hazardous mycotoxins has been studied along the whole food production chain, i.e. in crops and in foods for consumption. In order to protect consumers against an exposure, strategies aimed to reduce and mitigate the occurrence of mycotoxins at pre- and post-harvest stages have been implemented. Furthermore, maximum limits for mycotoxins in major food/feed commodities are set in legislation, and health-based guidance values are derived by scientific advisory committees as basis for assessing risks. Although these strategies and regular monitoring allow for a significant reduction of risks from exposure to mycotoxins, humans continue to be exposed to mycotoxins, in some circumstances at levels exceeding the current health-based guidance values. Therefore, it can be hypothesized that stages in the production of crops and consumer choices of foods are contributors to mycotoxin exposure, but presently not considered. The work presented in this habilitation developed and evaluated new monitoring strategies to investigate this hypothesis. Soil is the basis for the cultivation and production of crops, but has not been evaluated as source of mycotoxins until now. This is relevant, considering that the soil is the habitat for the inoculum of several mycotoxigenic fungal species and that mycotoxins are ubiquitous in the environment including soil. Next, mycotoxins can be mobilized from soil to plant, which may increase the risk for a contamination of harvested commodities. Evaluation of the soil as a source of mycotoxins should also consider the role of managements and treatments in modern agriculture and how these affect soil physicochemical or biological properties as well as the occurrence and fate of mycotoxins in soils. In addition, some mycotoxins have antimicrobial properties and may thus influence the soil microbiome with the consequence of changes in soil biogeochemical processes and functions. Current strategies for mycotoxin exposure prevention are restricted to the food production chain, namely from cropping/harvest until retail level. But, food commodities are stored in the households with the possibility that mycotoxins can form by late fungal infection, with a risk for exposure. In this regard, human exposure to mycotoxins is determined by the individual food habits, preferences and lifestyle. Therefore, it is important to identify major sources of mycotoxin exposure in different population groups, and also how the exposure is driven by food preferences and lifestyle, in particular at the household level. The overall aim of this habilitation is to extend the knowledge on mycotoxins as environmental pollutants by evaluating steps beyond the food production chain that may contribute to mycotoxin-related risks for humans and for the environment. Concretely, this means to conduct monitoring of soils as a source of mycotoxins, and to assess also how alimentary habits and lifestyle may impact on exposure at the consumer level. This entails the design of an integrated monitoring strategy concept which includes unexplored sources and risks for mycotoxin exposure. This habilitation covers 23 published papers and is divided into three main chapters: (i) Plastic mulching and soil quality indices (chapter 2): In this chapter the impact of mulching systems, namely straw and plastic, on soil physical, chemical and biological properties as well as biogeochemical processes were analysed using the example of asparagus and strawberry crops. The starting point was a literature review on the benefits and potential risks related to the use of plastic mulching in agriculture [chapter 2.1]. This was followed up by field monitoring experiments with a focus on the effects of plastic mulching on soil (micro)organisms [chapter 2.2 and 2.3] and on modifications of soil biogeochemical processes in short- and long-term application [chapter 2.4 and 2.5]. Due to the increasing awareness of the use of plastics in the environment, plastic mulching was also investigated for its contribution to soil plastic pollution [chapter 2.6 - 2.8]. (ii) Occurrence and fate of mycotoxins in agricultural soils (chapter 3): Mycotoxins do occur in soil, but their biosynthesis in situ as well as their persistence are influenced by soil biogeochemical processes related to the structure and function of the soil microbiome. The occurrence and fate of mycotoxins was investigated starting with the development of sensitive methods for the analysis of mycotoxins in soils [chapter 3.1], considering that levels in soils may be of factor hundred lower than concentrations observed in food commodities. Then, suitable sampling strategies were developed to account for the heterogeneous distribution of mycotoxins in soils [chapter 3.2]. Sampling and analytical methods were applied to investigate the occurrence of mycotoxins in soils, exemplified by studies on the use of plastic mulching in agriculture [chapter 3.3 and 3.4]. Since mycotoxin levels in soils reflect only concentrations measured at the time of sampling, without considering spatio-temporal dynamics, a further focus of our studies was to evaluate the biosynthesis and stability (fate) of the mycotoxins in the soil matrix depending on the integrity of the soil microbiome [chapter 3.5 - 3.8]. (iii) Human exposure and biomonitoring (chapter 4): Here, it was evaluated how alimentary habits and lifestyle may contribute to the risk of mycotoxin exposure. Firstly, (bio-) monitoring strategies which include the identification and characterization of suitable biomarkers in biological matrices that are representative of exposure were investigated [chapter 4.1 - 4.4], considering also food intake differences between infants and adults. In the context of sensitive population-groups also an in silico approach was used to model their mycotoxin exposure [chapter 4.5]. Finally, the risk of mycotoxin exposure was evaluated based on alimentary habits and contaminant levels in food commodities, and for lifestyle aspects and awareness on risks from mouldy food [chapter 4.6 and 4.7]. The results of this habilitation provide new insights on so far unexplored sources for mycotoxins with relevance for humans and for the environment. This includes the development and application of suitable sampling and (bio-)monitoring strategies to assess (i) mycotoxin occurrence in agricultural soils and (ii) exposure at the consumer level. This work shows that soil is a source of mycotoxins and that agricultural practices influence the integrity of the soil and consequently in situ mycotoxin concentrations. Then alimentary habits, lifestyle and knowledge on mycotoxins are decisive factors for exposure at the household level. Both aspects are not yet considered in current risk assessment strategies. Therefore, an integrated interdisciplinary model for mycotoxin prevention strategies starting in soil and including also the consumer level is suggested.