A growing body of scientific evidence shows that microplastics accumulate in critical human organs, including the brain, leading researchers to call for more urgent action to curb plastic pollution.
Studies have detected small shards and specks of plastic in humans lungsplacentas, reproductive organs, livers, kidneys, knee and elbow joints, blood vessels and bone marrow.
Given the research findings, “it is now imperative to declare a global emergency” to deal with plastic pollution, said Sedat Gündoğduwho studies microplastics at Cukurova University in Turkey.
Humans are exposed to microplastics – defined as fragments smaller than 5mm in diameter – and the chemicals used to make plastic from widespread plastic pollution in air, water and even food.
The health hazards of microplastics inside the human body are not yet known. Recent studies are just beginning to suggest that they may increase the risk of several conditions, such as oxidative stresswhich can lead to cell damage and inflammation, as well cardiovascular disease.
Animal studies have also linked microplastics fertility issuesvarious cancers, a disrupted endocrine and immune system, and impaired learning and memory.
There are currently no government standards for plastic particles in food or water in the United States. The Environmental Protection Agency is work on crafting guidelines for measuring it, and since 2018 has been issuing grants to develop new ways to rapidly detect and quantify it.
Finding microplastics in more and more human organs “raises a lot of concern” given what we know about health effects in animals, studies of human cells in the laboratory and emerging epidemiological studies, said Bethanie Carney Almrothan ecotoxicologist at the University of Gothenburg in Sweden. “It’s scary, I’d say.”
‘Very worrying’
In one of the latest studies to emerge – a preprinted paper still undergoing peer review, that is posted online by the National Institutes of Health – researchers found in particular about accumulation of microplastics in brain samples.
An examination of the livers, kidneys and brains of autopsied corpses found that all contained microplastics, but the 91 brain samples contained on average about 10 to 20 times more than the other organs. The results came as a shock, according to study lead author Matthew Campena toxicologist and professor of pharmaceutical sciences at the University of New Mexico.
The researchers found that 24 of the brain samples, collected in early 2024, measured an average of about 0.5% plastic by weight.
“It’s quite concerning,” Campen said. “There is a lot more plastic in our brains than I could have ever imagined or was comfortable with.”
The study describes the brain as “one of the most plastic-contaminated tissues ever sampled”.
The preprint brain study led by Campen also indicated a troubling link. In the study, researchers looked at 12 brain samples from people who had died of dementia, including Alzheimer’s disease. These brains contained up to 10 times more plastic by weight than healthy samples.
“I don’t know how much more plastic we can cram into our brains without causing problems,” Campen said.
The paper also found that the amount of microplastics in brain samples from 2024 was about 50% higher than the total in samples dating to 2016, suggesting that the concentration of microplastics found in human brains is increasing at a similar rate as in the environment is found. Most of the organs came from the Office of the Medical Examiner in Albuquerque, New Mexico, which investigates untimely or violent deaths.
“You can draw a line – it increases over time. It matches what you see in the area,” said Campen.
Many other papers have found microplastics in the brains of other animal species, so it’s not entirely surprising that the same could be true for humans, said Almroth of the University of Gothenburg, who was not involved in the paper.
When it comes to these insidious particles, “the blood-brain barrier is not as protective as we like to think,” Almroth said, referring to the series of membranes that keep many chemicals and pathogens from reaching the central nervous system.
Explosion of research
The Journal of Hazardous Materials adds to the concern about accumulation in the human body published a study last month that found microplastics in all 16 bone marrow samples examined, the first paper of its kind. All of the samples contained polystyrene, which is used to make peanuts and electronics, and almost all contained polyethylene, which is used in transparent food paper, detergent bottles and other common household products.
One more recent newspaper looked at 45 patients undergoing hip or knee surgery in Beijing, China, found microplastics in the membrane lining of every single hip or knee joint examined.
A study published on May 15 in the journal Toxicological Sciences found microplastics in all 23 human and 47 dog testicles studied, and found that samples from humans had a concentration nearly three times greater than that from dogs. A higher amount of certain types of plastic particles – including polyethylene, the main component of plastic water bottles – correlated with lower testicular weights in dogs.
One more paper, which appeared on June 19 in the International Journal of Impotence Research, found plastic particles in the penises of four out of five men who received penile implants to treat erectile dysfunction.
“The potential health effects are concerning, especially considering the unknown long-term consequences of microplastics that accumulate in sensitive tissues such as the reproductive organs,” said Ranjith Ramasamy, the study’s lead author and a medical researcher and urologist at the University of Miami.
Meanwhile a Chinese group published a study in May showing small amounts of microplastics in the semen of all 40 participants. An Italian paper from a few months earlier reported similar results.
A handful of studies have also now found contamination in human placentas. A study that appeared in the May issue of Toxicological Sciences reported that micro- and nanoplastics were found in all 62 placental samples, although the concentration varied widely.
In Italy, researchers followed 312 patients who had fatty deposits or plaques, removed from their carotid artery. Nearly six in 10 had microplastics, and these people fared worse than those who didn’t: Over the next 34 months, they were 2.1 times more likely to experience a heart attack or stroke, or die.
‘Nowhere left untouched’
The Food and Drug Administration says in a statement on its website that “current scientific evidence does not demonstrate that levels of microplastics or nanoplastics detected in food pose a risk to human health.”
Still, researchers say that individuals should try to reduce their exposure by avoiding the use of plastic in food preparation, especially when microwaving; drink tap water instead of bottled water; and try to prevent the accumulation of dust, which is contaminated with plastic. Some researchers recommend eating less meat, especially processed products.
Leonardo Trasande, a medical researcher at New York University, said much remains unknown about the impact of microplastic accumulation in humans. However, the negative health impacts of chemicals used in plastics, such as phthalates, are better established, he said. A study he co-authored found exposure to phthalates have increased the risk of cardiovascular disease and death in the United States, causing $39bn or more in lost productivity per year.
Microplastic particles can be contaminated with and carry such chemicals into the body. “The micro- and nanoplastics can be effective delivery systems for toxic chemicals,” said Trasande.
The American Chemistry Council, which represents plastics and chemical manufacturers, did not respond directly to questions about the recent studies that found microplastics in human organs. Kimberly Wise White, a vice president of the group, noted that “the global plastics industry is committed to advancing the scientific understanding of microplastics”.
The United Nations Environment Assembly agreed two years ago to begin work on a global treaty to end plastic pollution, a process that is in progress.
Various news reports in the past week suggests that the Biden administration has signaled that the US delegation involved in the discussions will support measures to reduce global production of plastic, which researchers say is critical to getting a handle on the problem.
“There is nowhere left untouched from the deep sea to the atmosphere to the human brain,” Almroth said.
This story is shared with the New Membersa journalistic project of the Environmental Working Group
