Microplastics on the Sheep's Menu

A new study examined plastic contamination in agricultural soils in Spain and sought to estimate the amount ingested by sheep during grazing. The results show that sheep herds could be a source of the spread of these microparticles, which are harmful to both health and the environment.   Microplastics have invaded nearly every ecosystem, from the oceans to the most remote mountains, affecting both pristine environments and the organisms that live there. Also present in food, animals ingest them and can act as both carriers and vectors of these harmful microparticles, just as water and wind break them down and disperse them. However, only a few studies have examined the transfer of microplastics via terrestrial organisms. Regarding their ingestion, earthworms were the first to be studied. Microplastics can indeed pass from the soil to earthworms and then to chickens that eat them. Similarly, they pass from the soil to bean leaves and snails before being swallowed by their predators. While plastic is widely used in many sectors, including agriculture, no study had previously assessed the ingestion of microparticles in pastures used for livestock grazing. Plastic is, however, ubiquitous on farms, both through its primary use in fields and via soil amendments containing contaminated products, such as biofertilizers. Plastic-covered mulch, in particular, is used to raise soil temperature, control weeds, and improve water use efficiency. Similarly, plastic nets are used to protect crops, and plastic pipes provide irrigation. Unfortunately, all of these plastics undergo degradation in the field, and fragments accumulate in the soil. In the Murcia region of Spain, plastic mulch is widely used for intensive vegetable farming, and after harvest, sheep are released into the fields to graze on residues. Researchers have shown that all soil samples from farms in the region using this mulch contained microplastics, and consequently, 92% of the fecal samples from the sheep grazing there also contained microplastics. After ingesting the plastic present in a field, sheep can then themselves become a source of contamination when they move onto fallow land or a natural area. Contaminated plant material can remain in a sheep’s digestive system for up to 35 hours. The potential transport of microplastics by a flock of 1,000 sheep has been estimated at approximately 106 particles per hectare per year. These results clearly highlight the need to standardize and normalize the measurement of microplastics on farms to better assess their impact, while also exploring their effects on and via Livestock. Plastic contamination, stemming in part from increasingly intensive agricultural practices, poses a growing threat to human and animal health, as well as to ecosystems. A paradigm shift in current agricultural production appears necessary if we are to reverse this trend.