The mysterious danger of microplastics

It’s enough to make you sick.

Plastic waste is everywhere, littering our streets, waterways and beaches. Now it’s showing up in our bloodstream, in the form of microplastics — plastic particles that range in size from 0.1 to 5,000 micrometres. Researchers are still getting the full picture of just how harmful microplastic consumption is for humans, but the early indications are a cause for concern.

Microplastics most commonly enter the body through the gastrointestinal tract, starting from the mouth. But they’ve shown up all over the upper body in organs such as the intestine, lungs, kidneys, liver, and spleen. Microplastics have also appeared in faeces and the placenta.

In one analysis, infants had a concentration of poly(ethylene terephthalate), a polyester resin found in plastics, in their faeces ten times higher than in the adults' samples. Microplastics were even detected in the earliest stool of newborns, meaning humans are being exposed to plastic before birth.

Cells subjected to microplastics pollution die three times faster than they do when exposed to other, cleaner foreign bodies. This happens because “oxidative stress” is induced: the immune system detects microplastics, regards it as an enemy, and reacts violently to protect the body against it. In doing so, the immune system is weakened and vulnerable to declining health. Beyond that, microplastics carry toxins, leading to potential health risks.

Research on mice shows that microplastics may cross the brain-blood barrier, and accumulate in microglial cells accompanying neurons. Microplastics have been found in human blood — meaning people are likely as vulnerable to the blood-brain barrier crossover as mice.

Research is still digging into the mystery around what such findings mean for wider human health, but the known details are alarming. There’s a lot that researchers are still in the early stages of figuring out, such as how prevalent microplastics are in food and drinks.

Results are often inconclusive due to the complexity of plastic composition, size and shape of particles, and the presence of additional components. Information about microplastics is scattered. Analytical methodologies for detecting and identifying microplastics are still developing. Research is spread across different types of particles, making it difficult to compare data.

Data from toxicity studies is limited and often inconsistent. The complexity of microplastics, composition, size, and shape, and their interactions with other components make it difficult to obtain reliable data.

While researchers are still determining the degree of harm, just the thought of unknowingly swallowing microplastics is enough to make many people queasy — especially if there’s a risk of traces crossing the blood-brain barrier. In the meantime, it’s another compelling reason to commit to a reduction of plastic waste in the environment.