The Macro Impacts of Microplastics

ATLANTA—Some of the most frightening pronouncements made at the Consortium of Universities for Global Health last week emerged from the Atlanta Hilton’s Room 205-207 during a Feb. 21 session:

• “We’re literally becoming part plastic,” said Amelia Meyer, a Stanford University research program manager.
• “Plastic chemicals cause disease at every stage of the human life cycle,” said Philip Landrigan, director of Boston College’s Global Observatory on Planetary Health.   
• “There are at least 16,000 chemicals in plastics. Nobody really knows,” Landrigan said. “And the real kicker is that more than 80% of the chemicals in plastic have never been tested for toxicity.”

The inexpensive and convenient nature of plastics has made them near-essential building blocks of modern life, used in everything from toys to clothing, cups to furniture, and electronics to disposable diapers. Their simple construction—a polymer matrix into which are inserted thousands of possible chemicals—make them endlessly adaptable. Different chemicals inserted into the polymer give plastics different properties such as color, flexibility, stability, water repellency, and so on, said Landrigan.

From the early days of industrial production of plastics in the mid-20th century to today, humans have produced between 8 and 10 billion tons of plastics, he said, adding that about 75% of all plastic ever made is still circulating the environment.

Microplastics—tiny plastic bits from larger pieces of plastic—have rapidly dispersed across the globe from the snows of the Himalayas to arctic sea sediment. Less than 5 millimeters long, microplastics can also collect new chemicals, making them potentially more dangerous as they penetrate human tissues and organs such as testicles, breasts, hearts, and colons. 

And, of course, all manner of larger plastics—bottles and containers—have fouled seas, beaches, and lands worldwide as well.

Impact on Human Health

Microplastics can potentially cause disease in at least two ways. “One is by releasing toxic chemicals,” Landrigan said. “Another is simply by their sheer physical presence. The fact that these particles are sitting inside cells means that they have the potential to disrupt cellular function.”

In fact, a March 2024 New England Journal of Medicine article based on a study of 304 heart disease patients found that those who had microplastics in their carotid plaque had a 450% increased risk of heart attack, stroke, or death over a three-year period. “It’s only one study—it certainly does not prove causation,” cautioned Landrigan. “But it is a finding that is needs to be taken seriously. You know most elevated risks in epidemiologic studies are in the 10 to 20% range—not the 450% range.”

Other effects of microplastics, such as their connection to lung and colon cancers and their impacts on human reproductive, digestive, and respiratory health, are still being determined, according to a Dec. 2024 article in Environmental Science & Technology.

“We’re only just discovering what could happen to people who have been exposed to plastics their whole lives, right?” Meyer said in an interview with GHN. “It’s just there … from their birth throughout their life.”

Solutions Needed

While many people recognize the need for solutions to Earth’s plastic problem, few comprehend the urgency. In the coming decades, the plastics industry is expected to massively expand its current production of 500 million tons per year. Production will double by 2040 and triple by 2060, Landrigan said. 

“Certainly, within the lifetimes of those folks in the room here, there’s going to be a great deal more plastic in the world than there is today,” he said.   

Worse still, recycling isn’t a viable solution for the plastics problem. Just 10% of plastics get recycled. “There are so many different polymers. There are so many toxic chemicals in the plastic. The different polymers cannot be comingled—it’ll just make sludge,” Landrigan said. “And the toxic chemicals, which include carcinogens, neurotoxicants, [and] endocrine disruptors, are just not suitable for inclusion in a whole range of consumer products. 

“Hence, 90% of plastic either gets landfilled or burned or put on ships and sent to developing countries,” he said. “And that’s the reality, and it’s very much contrary to what the plastic industry would like you to link.”

Despite the threats to the environment and human health, Landrigan doesn’t advocate for a complete ban on plastics. “First of all, it’s completely unrealistic. And secondly, too many of the plastics that are in the world today are really essential,” he said in an interview. “I’m a pediatrician, and I couldn’t imagine practicing medicine without plastics. There’s instruments and tools and things like intravenous [lines]—there’s really no good substitute for plastic.”

From the macro solutions perspective, a UN global plastics treaty is being negotiated. It was scheduled to be completed last November in Busan, Korea, Landrigan said. More than 100 countries are part of the “high ambition coalition” that wants a cap on plastic production and to control the toxic chemicals in plastics, he said. But Russia, Saudi Arabia, and other petrostates are fighting the production cap because “increasing production of plastics is their business bottom line as the market for fossil fuels declines,” Landrigan said. 

“Trash to Treasure”

Early in her time working in Guatemala, Lisa Thompson, now a professor at Emory University’s Rollins School of Public Health, noticed how frequently people used plastic bottles as kindling to start fires. But burning plastic “produces all kinds of terrible stuff, including benzene, dioxin, [and] heavy metals,” Thompson said. 

Working with 16 villages, Thompson and her team have offered classes in making soap (so participants can replace the plastic packages of cleaning powder that were frequently tossed in the river), led a community clean-up, and connected women with recyclers who pay them for plastic and metal products. After eight weeks, participants drafted a plan for interventions they wanted to carry out. The researchers are collecting urinary biomarkers and data from personal monitors to gauge whether participant exposure to emissions from plastic burning have been reduced. The trial isn’t yet complete, so results are not yet available, she said. 

But she did note that the community clean-ups have instilled a new spirit in the communities, which now display signs warning people not to litter. 

In Kenya, plastic trash impacts human health by providing ideal breeding sites for Aedes aegypti mosquitoes, which transmit viruses that cause dengue, yellow fever, chikungunya, Zika, and other diseases, said Desiree LaBeaud, a professor of pediatrics and a senior fellow at the Woods Institute for the Environment at Stanford University. “I think we can recognize that the low cost and convenience of plastics are deceptive and actually mask significant harms, including environmental and health risks,” said LaBeaud. 

Collaborating with partners in coastal Kenya, LaBeaud and colleagues worked with 250 local students from five primary schools to collect over 17,000 mosquito breeding containers. Some of the containers were used to grow more than 4,000 native seedlings, while the remainder were buried because of a lack of recycling options. Her team then worked with local informal plastic recyclers on a “trash for treasure” project that increased the amount of plastic waste traded and led to reductions in A. aegypti breeding sites and a decrease in vector-borne diseases. 

LaBeaud is also bringing her perspective on plastics to their use in U.S. health care. “We need to implement necessary changes in practice, and this includes everything we do in medicine, from ORs and everything that we use in our clinics and our laboratories to minimize our reliance on plastic and the environmental impact, and advocate for stronger policies that promote sustainable health care practices,” LaBeaud said.

Join the 50,000+ subscribers in 170+ countries who rely on Global Health NOW summaries and exclusive articles for the latest public health news. Sign up for our free newsletter, and please share the link with friends and colleagues.