Microplastics in Farmed Animals—A Review

Environmental pollution from plastics has become one of the biggest concerns globally. Microplastics (MPs) are plastic materials less than 5 mm in size. They remain in the environment for hundreds to thousands of years without degrading, only breaking down further to nanoplastics (NPs). Micro- and nanoplastics can be the origin of many diseases and can carry various pathogenic substances on their surface and spread them throughout the biosphere, starting with contained additives and ending with adsorbed toxins from the environment and potentially pathogenic microorganisms. Exposure routes for humans and animals are through air, water and food/feed. Due to the placement of livestock—including ruminants, fish and poultry—and humans at the top of the food web, any pollution in water, air or soil can eventually be transferred to livestock and from livestock to humans. The presence of microplastics in the intestines of aquaculture species, ruminants and poultry, for instance, was found to cause a change in the intestinal microbial population and, as a result, the occurrence of diseases. These particles have also been observed in other organs such as liver, kidneys, lung, spleen, heart, ovaries, and testicles of animals, which causes biochemical changes, structural destruction, and malfunction. While the complete extent of the negative health impacts of microplastics remains still largely unknown, their ubiquitous presence and the transmission of chemicals from microplastics to organisms is a notable issue, underscoring the importance of gaining a more comprehensive understanding of the potential threats posed by microplastics to animal and ultimately human health, coupled with a need for drastic reduction of the plastic freight into the environment. This review article summarizes recent findings on the effect of micro- and nanoplastics on farmed animals and, ultimately, on humans. Action is needed to reduce the number of microplastics to which farmed animals, and thereby humans, are exposed.