Microplastics In Humans And Other Animals

Tiny pieces of plastic called microplastics are everywhere: food, air, drinking water, alcoholic drinks, and even salt. Animals, including humans, breathe in and eat these particles, but the effects are unknown. This article explores how farmed animals and companion animals are exposed to microplastics, and what this means for humans.

Microplastics can get into animals or animal products used for human food in many ways. They’re in the food that farmed animals eat, like soybeans. Honeybees can pick up microplastics on their bodies when they visit flowers. Animals that graze or eat from the ground can get microplastics from the plants or insects that they eat. Starving animals may intentionally eat plastic.

Studies have shown that land animals used for food have microplastics in their bodies — mostly their digestive tracts. Although the subject is understudied, preliminary evidence suggests that meat isn’t contaminated with microplastics because the microplastics are too large to make it to the muscle tissue. However, eggs and milk do have microplastics, and meat may be contaminated with microplastics too small for scientists to detect with current methods.

Microplastics can get into meat when it’s processed. Animal products can pick up microplastics from plastic cutting boards, packaging, or synthetic sausage casings. Milk that is highly processed contains more microplastics than less processed milk, with powdered milk containing the most. 

While scientists haven’t found any evidence that microplastics in the doses most people are exposed to are harmful to human health, they know that high levels of exposure are dangerous. They’ve also discovered plausible pathways through which microplastics could cause harm. Scientists know that microplastics are harmful to animals’ health. For example, chickens who ate a high-microplastic diet gained less weight, had reduced antioxidant capacity, and showed signs of having diseased cells. 

Organic fertilizers made from manure contaminated with microplastics can be another threat to food security through poorer soil quality and reduced plant growth. Soil contaminated with microplastics cannot hold water as well as uncontaminated soil, and shows different microbial activity. Plants grown in these soils grow smaller than plants grown in uncontaminated soil. Further, microplastics in fertilizer accumulate in plants, which can pass on to humans and animals who eat them.

The authors also suggest that companion animals can be seen as living signals for human exposure to microplastics. Companion animals usually share the same environment, water, and sometimes food as humans. The effects of microplastic exposure in companion animals are easier to study because they have shorter lifespans than humans, are more sensitive to environmental contaminants, and don’t have confounding negative health behaviors such as smoking. Samples of companion animal tissue are more readily available than samples of human tissue. By studying companion animals, scientists could better understand the microplastics humans eat and breathe in. 

Microplastics have been found in cats, dogs, and domestic pigs, although so far, studies have not shown a relationship between the exposure of companion animals and their human families. Further, companion animals might have different microplastic exposure patterns than their guardians. For example, companion animals might be exposed to microplastics by playing with plastic toys. They might breathe in more microplastics because they breathe in air closer to the ground, where microplastics tend to accumulate. Nevertheless, studying companion animals may help researchers shed light on the poorly understood issue of microplastic contamination.

Microplastics aren’t going away anytime soon. As this study suggests, consuming farmed animals is one pathway (among many) that can expose humans to such harmful substances. When conducting dietary advocacy, it’s important to remind the public that microplastics are among the many health risks of a diet heavy in animal products. And as we encourage people to reduce their environmental footprint, we should point out that plastic use is bad for humans and other species.