Microplastics have been detected in human blood, placentas, lungs, and even the brain, with one study estimating that our cerebral organs may contain up to 5g of plastic—roughly a teaspoon. Researchers are increasingly concerned about the potential health impacts of these tiny particles, which are shed from packaging, clothing, paints, cosmetics, and car tyres.
A new study presented at the United European Gastroenterology conference in Berlin found that when gut bacteria from healthy volunteers were exposed to common microplastics, the bacterial populations shifted, along with the chemicals they produced. Some of these changes mirrored patterns linked to depression and colorectal cancer. Lead researcher Christian Pacher-Deutsch of the Medical University of Graz said: 'While it’s too early to make definitive health claims, the microbiome plays a central role in many aspects of wellbeing, from digestion to mental health. Reducing microplastic exposure where possible is therefore a wise and important precaution.'
Animal studies have also raised alarms. Mice given microplastic-laden water began behaving differently—venturing into open spaces rather than hugging walls—a behaviour more often seen with ageing and neurological disease. Dissection revealed plastic in every organ, including the brain, where a key protein linked to brain health was depleted, mirroring patterns seen in depression and dementia.
Human studies have added to the unease. Microplastics have been found in the brains of dementia patients and in arterial plaques from people with heart disease. Those with plastic-laden plaques were almost five times more likely to suffer a stroke, heart attack, or die within three years.
Dr Jaime Ross, a neuroscientist at the University of Rhode Island, noted: 'We know microplastics are in almost every tissue that has been looked at, and recent studies suggest we’re accumulating far more plastic now than 20 years ago.' She added that designing definitive experiments is challenging because humans are constantly exposed to these particles.
Despite the growing evidence, experts caution that it is still unclear what constitutes a 'safe' level of microplastic exposure. A commercial blood test offered by Plastictox can estimate individual levels, but its utility remains debated. The test detected four microscopic particles in one journalist’s blood sample, equating to about 200,000 particles in the bloodstream—though the average person has over a million, according to the test's manufacturer.
