Microplastics are widespread, accumulating in the remotest parts of our planet. There is evidence of their toxic effects at every level of biological organization, from tiny insects at the bottom of the food chain to apex predators.
Microplastics are pervasive in food and drink and have been detected throughout the human body. Evidence of their harmful effects is emerging.
Microplastics are generally accepted as plastic particles 5mm or less in one dimension. Some microplastics are intentionally added to products, such as microbeads in facial soaps. Others are produced unintentionally when bigger plastic items break down—for example, fibers released when you wash a polyester fleece jacket.
Studies have identified some of the main sources of microplastics as:
- cosmetic cleansers
- synthetic textiles
- vehicle tires
- plastic-coated fertilizers
- plastic film used as mulch in agriculture
- fishing rope and netting
- “crumb rubber infill” used in artificial turf
- plastics recycling.
It’s difficult to assess the volume of microplastics in the air, soil and water. But researchers have attempted it. For example, a 2020 study estimated between 0.8 and 3 million tons of microplastics enter Earth’s oceans in a year. And a recent report suggests leakage into the environment on land could be three to 10 times greater than that to oceans. If correct, it means between 10 and 40 million tons in total.
The news gets worse. By 2040, microplastic releases to the environment could more than double. Even if humans stopped the flow of microplastics into the environment, the breakdown of bigger plastics would continue.
Microplastics have been detected in more than 1,300 animal species, including fish, mammals, birds and insects.
Some animals mistake the particles for food and ingest it, leading to harm such as blocked intestines. Animals are also harmed when the plastics inside them release the chemicals they contain—or those hitch-hiking on them.
Microplastics have been identified in the water we drink, the air we breathe and the food we eat.
As equipment has advanced, scientists have identified smaller particles. They’ve found microplastics in our lungs, livers, kidneys, blood and reproductive organs. Microplastics have crossed protective barriers into our brains and hearts. While we eliminate some microplastics through urine, feces and our lungs, many persist in our bodies for a long time.
So what effect does this have on the health of humans and other organisms? Over the years, scientists have changed the way they measure this. They initially used high doses of microplastics in laboratory tests. Now they use a more realistic dose that better represents what we and other creatures are actually exposed to.
And the nature of microplastics differ. For example, they contain different chemicals and interact differently with liquids or sunlight. And species of organisms, including humans, themselves vary between individuals.
This complicates scientists’ ability to conclusively link microplastics exposure with effects.
In regards to humans, progress is being made. In coming years, expect greater clarity about effects on our bodies such as:
- inflammation
- oxidative stress (an imbalance of free radicals and antioxidants that damages cells)
- immune responses
- genotoxicity—damage to the genetic information in a cell that causes mutations, which can lead to cancer.