Macro effect of micro plastics – concerns over health as rising levels of microplastics found in humans

Microplastics are exactly what they say they are on the tin – very tiny particles of plastic, clocking in at five millimetres or smaller. Some are the result of the gradual breakdown of larger plastics, while others were always designed to be miniscule, such as microbeads found in cosmetics and microfibres found in clothes. The smallest type of microplastics are nanoplastics, measuring less than one micrometer (one thousandth of a millimetre) in size. These are most worrying to researchers due their ability to infiltrate cells and potentially cause more damage than good. 

Over the past 50 years, as plastic has become a widespread feature of everyday life, global levels of plastic pollution have skyrocketed. Consequently, microplastics are omnipresent; in the air you breathe, the water you drink, and the food you eat. A 2022 study estimated the average person consumes between 78,000 and 211,000 particles of microplastic every year – and this is widely considered to be a conservative calculation! Now, scientists have found evidence of the bioaccumulation of microplastics – meaning increasing concentrations of microplastics in the body –  and are questioning what this means for human health. 

A study published this February in Nature Medicine revealed an increasing trend in microplastics in postmortems between 1997 and 2024. The team of US-based researchers identified microplastics in brain, kidney, and liver tissues of deceased humans using a range of methods (including gas chromatography, mass spectrometry, electron microscopy and a variety of spectroscopy techniques). Alarmingly, they showed that microplastic levels in the brain have increased by 50% in the past eight years alone! Plastic doesn’t discriminate either; microplastic concentrations were not influenced by age, ethnicity, sex, or cause of death, and were detected in every single sample studied. The most common microplastic across all tissues was polyethylene – the plastic in food and drink packaging – in the form of shards and flakes. 

What effect does all this plastic have on the function of our bodies? The study found that brain samples from dementia patients contained more microplastics than healthy brains, suggesting a possible connection between microplastics and neurological disease. Other recent studies discovered evidence of microplastics in the blood, lungs, placenta, semen, bone marrow and even breast milk. Such accumulation of microplastics has been linked to increased likelihood of strokes, heart attacks, inflammatory diseases, cancers, and deaths. One study further discovered that placentas from premature births contained significantly more microplastics than healthy births.

At the moment, all data linking microplastics to disease is purely associative. Scientists are careful not to conflate correlation and causation or jump to conclusions. There is still much we do not know about the impact of microplastics on our health. The ubiquitous nature of microplastics makes them particularly challenging to study, as they are so universal, there can be no human control group. To determine causal impacts further research is required – involving refined analytical techniques, more complex study designs and larger cohorts – all of which are too expensive to entertain at the moment. 

Words by Ruby Smith