Routes of human exposure to Micro- and Nanoplastics through the food chain: what do literature reviews say?

The scientific literature on microplastics in food has increased exponentially in the last years leading to a huge amount of published reviews on this topic. Following an approach inspired by the umbrella-review methodology, the present review aimed at systematically gathering information regarding the routes of exposure of microplastics through the food chain, starting from information collected by literature reviews. A literature-based search of published reviews was carried out in three scientific databases. Eligible reviews had to be written in English and had to deal with microplastics (MPs) or nanoplastics (NPs) in food or food chains. At the end of the screening process, 59 reviews were included of which four were systematic. Microplastics were found in a broad range of food originating from marine, freshwater and terrestrial environments. The size range of detected MPs/NPs varied greatly (0.02 – 16,400 μm). Among the analysed review, three food matrices (milk, beer and sugar) were considered for the cross-citation analysis. The choice was based on the fact that these matrices are unusually associated with MPs/NPs pollution and the high redundancy of information observed during data extraction. Results surprisingly showed that the number of published reviews was higher than the number of primary studies, suggesting the need for applying a systematic review methodology to comprehensively synthesize data on microplastics in food and to harmonize definitions. In addition, especially for European countries, future research on MPs/NPs distribution should be performed on food such as milk, wine and meat since they are poorly investigated in this area.