Microplastics in Terrestrial Domestic Animals and Human Health: Implications for Food Security and Food Safety and Their Role as Sentinels

SIMPLE SUMMARY: Microplastics are widespread environmental contaminants comprised of plastic pieces <5 mm. Human exposure to microplastics has been confirmed by their presence in multiple tissues. Terrestrial domestic animals may be relevant to human exposure, as they are also subjected to the same environmental contaminants, possibly acting as sentinels (i.e., help estimate exposure and risk to humans) or by being an integral part of the human food chain, as in the case of livestock. This work addresses how microplastics may impact terrestrial domestic animals, leading to consequences for food security (i.e., the availability of food) and food safety (i.e., the prevention of foodborne illnesses) and how companion animals may help estimate environmental human exposure. ABSTRACT: Terrestrial domestic animals are exposed to microplastics, therefore, contaminating the food chain, in the case of livestock, or acting as sentinels for human exposure, in the case of companion animals. The aim of this review was to address the importance of terrestrial domestic animals on human exposure to microplastics. Animal products may already show some microplastics contamination, which may occur during their lifetime, possibly also compromising productivity, and during processing, originating from equipment and packaging. Moreover, release of microplastics in animal feces (or manure) leads to the contamination of agricultural fields, with possible impacts and internalization in plants. Therefore, microplastics pose a threat to food security, compromising food productivity, and food safety, by being a foreign material found in animal products. Conversely, in urban environments, companion animals (cats and dogs) may be relevant sentinels for human exposure. While oral exposure may vary in pets compared to humans, due to indiscriminate ingestion and chewing or licking behaviors, airborne exposure is likely to be a good indicator for human exposure. Therefore, future studies should address the importance of terrestrial domestic animals for human exposure of microplastics, both in the food chain and as sentinels for environmental exposure.