Study on plastic pollution in some Bulgarian agricultural soils

Microplastics are widely abundant in terrestrial ecosystems, thus accumulating in food chains, threatening food security, food safety, and human health. Addressing this problem has not only fundamental scientific importance, but also a real practical-applied aspect, concerning both the safety of plant produce obtained from plastic-contaminated agricultural land, the safety of animal produce obtained from animals fed with contaminated feed, and the potential risk to human health and food security. The aim of the present study was to assess the degree of microplastic (MPs) contamination in some agricultural soils, collected from various regions of Bulgaria. Representative soil samples were taken from the selected agricultural lands at a depth of 0-40 cm and the content of plastics in soils was analyzed using Py-GC-MS. Characterization of the plastics contained in the studied agricultural soils included type, composition, fractions, quantity and potential origin/source of pollution. Data obtained revealed a clear relationship between agricultural practices and MPs pollution, as well as between soil type and MPs pollution. Most of the natural polymers found were cellulose and lignin (originated from crops), while the plastic polymers were presented by rubber (from tires), polypropylene (PP), polycaprolactone (PCL), nylon/polyamide 12 (PA12) and styrene-ethylene-butylene-styrene (SEBS). Such microplastics in an animal or human organism pose risks of a physical, chemical and microbiological nature. Physical risks are due to the small size of the particles, which can pass through biological barriers of intestines, blood-brain barrier, testes, etc., even placental tissues and cause direct damage. The presence of persistent, potentially dangerous contaminants is a cause of chemical risk, while microbiological risks are related to microorganisms attached to the surface of the plastic particles. This is why farmers and consumers are increasingly concerned about the dangers of plastic in food which in turns highlights the urgent need for more detailed scientific research in this area.