Researchers at the University of Vienna have discovered particles of plastic in mice’s brains just two hours after the mice ingested drinking water containing plastic.

Once in the brain, “Plastic particles could increase the risk of inflammation, neurological disorders or even neurodegenerative diseases such as Alzheimer’s or Parkinson’s,” Lukas Kenner, one of the researchers, said in a statement, although more research is needed to determine the relationship between plastics and these brain disorders. In addition to potentially severe degenerative consequences, the researchers also believe that microplastic contamination in our brains can cause short-term health effects such as cognitive impairment, neurotoxicity and altered neurotransmitter levels, which can contribute to behavioral changes.

In the course of their research, the team gave mice water laced with particles of polystyrene – a type of plastic that’s common in food packaging such as yoghurt cups and Styrofoam takeout containers.

Using computer models to track the dispersion of the plastics, researchers found that nanoplastic particles – which are under 0.001 millimeters and invisible to the naked eye – were able to travel into the mice’s brains via a previously unknown biological “transport mechanism”. Essentially, these tiny plastics are absorbed into cholesterol molecules on the brain membrane surface. Thus stowed away in their little lipid packages, they cross the blood-brain barrier – a wall of blood vessels and tissue that functions to protect the brain from toxins and other harmful substances.

While the Vienna study focused on the effects of plastics consumed in drinking water, that’s not the only way humans ingest plastic. A 2022 Chinese study concentrated on how nasally inhaled plastics affect the brain, with researchers reporting “an obvious neurotoxicity of the nanoplastics could be observed”. In basic terms, the inhaled plastics lead to reduced functioning of certain brain enzymes that also malfunction in the brains of patients with Parkinson’s disease and Alzheimer’s.

Of course, we eat plastic, too, and new research on plastics and brain health is emerging alongside breaking studies on how the contaminants affect our gastrointestinal health. Much like the blood-brain barrier, the gastrointestinal barrier is also vulnerable to interference by nanoplastics – which can cause inflammatory and immune reactions in the gut, as well as cell death.

At this point, it’s clear that plastics have infiltrated most parts of the human body, including our blood, organs, placentas, breast milk and gastrointestinal systems. While we don’t yet fully understand how plastics affect different parts of our bodies, many chemicals found in various types of plastic are known carcinogens and hormone-disruptors, linked to negative health outcomes including obesity, diabetes, reproductive disorders and neurological impairments in foetuses and children.

This spring, the Boston College Global Observatory on Planetary Health led the first-ever analysis of the health hazards of plastics across their life cycle and found that “Current patterns of plastic production, use, and disposal are not sustainable and are responsible for significant harms to human health … as well as for deep societal injustices.”

None of this is encouraging news – especially in light of the fact that plastic production is still accelerating. Yet, improving our understanding of plastic’s implications for human health is a crucial step towards banning plastic – a move 75% of people globally support. Encouragingly, more than 100 countries have a full or partial ban on single-use plastic bags, and policymakers in some countries are thinking about plastics more in terms of their costly externalities, including pollution and effects on health. Yet global plastics regulation is still vastly out of step with both scientific and public opinion.

In 2021, the Canadian government formally classified plastics as toxic under the Canadian Environmental Protection Act. The move means that the government has more control over the manufacture and use of plastics, limiting the kinds of exposure that threaten health. In response, plastic producers including Imperial Oil, Dow Chemical and Nova Chemicals formed a coalition to try to crush these regulations.

More countries must designate plastics as toxic and increase its regulation, doubling down on the message that when plastic affects our health – even going so far as to alter our brain function – it infringes on our human rights.