Bottlenose dolphins leapt and torpedoed through the shallow turquoise waters off Florida’s Sarasota Bay. Then, a research team moved in, quickly corralling the small pod in a large net.
With the speed of a race car pit crew, veterinarians, biologists and their assistants examined the animals, checking vital signs while taking skin, blood and other samples. They held a petri dish over each dolphin’s blowhole until it exhaled, with an intensity similar to a human cough. Then, they rolled up the net and the dolphins swam off unharmed. A pod in Louisiana’s Barataria Bay was similarly tested.
Generations of dolphins have been part of this ongoing dolphin health study, which has been run by the Sarasota Dolphin Research Program since 1970. It tracks populations and individuals and also looks for health issues related to pollutants in the marine environment.
In the lab, scientists discovered that all 11 of the dolphins had breathed out microplastic fibers, shed from synthetic clothing, says Leslie B. Hart, associate professor at the College of Charleston and an author on this research. The fibers resembled those found in human lungs in previous studies, proving that dolphins, like us, are breathing plastic. In people, microplastic has been linked to poor lung function and possible lung disease.
An earlier collaboration linked phthalates circulating in the dolphins’ blood to alterations in their thyroid hormone levels — an effect also found in humans that can impact nearly every organ in the body. Phthalates, toxic chemicals found in flexible plastics, readily leach into the environment. The full effects on marine mammals remain unknown.
The dolphin studies are part of a larger quest to understand how plastic pollution is impacting the world’s wildlife. While thousands of human studies have demonstrated damage from tiny plastic particles entering both cells and organs throughout the body, little is known about animal impacts because long-term field studies are difficult and costly. “We’re really just starting to skim the surface,” Hart says.
Beyond the threat plastics pose to individual animals and species, other researchers have detected broader, global harm, a new report warns. Plastic pollution is transforming Earth systems needed to support life, worsening climate change, increasing biodiversity loss, making oceans more acidic and more.
The plastics crisis is escalating rapidly: Each year, petrochemical manufacturers make more than 500 million tons of plastics –– but the world recycles just 9%. The rest is burned, landfilled or ends up in rivers, rainwater, the air, soil or the sea. Today, the planet is awash in plastic. “It’s everywhere. It’s pervasive and it’s persistent,” says Andrew Wargo, who focuses on ecosystem health at the Virginia Institute of Marine Science.
Since the 1930s the polymers industry has completely altered daily life: Plastics are in our homes, cars, clothes, furniture, electronics, as well as our single-use throwaway water bottles, food packaging and takeout containers.
In 2022, the U.N. Environment Assembly voted to address the plastic crisis by creating a legally binding international plastics treaty in hope of curbing and regulating production. But plastics-producing nations, including China, Russia, Saudi Arabia, Iran and the U.S. resisted progress, influenced by a $712 billion plastics and petrochemicals industry and its lobbyists.
A critically important fifth round of negotiations begins Nov. 25 when delegates hope to hammer out final treaty language for ratification by U.N. member states.
Meanwhile, the natural world is in great danger, threatened by a biodiversity crisis, a climate crisis and serious degradations of planetary systems. Researchers are now scrambling to understand the growing threat plastics pose to the health of all living organisms.
Plastics conquer the world
Bakelite, the first synthetic plastic product ever made, came on the market in 1907. By the 1950s, production ramped, changing the course of history and revolutionizing modern life. Plastics facilitated innumerable human innovations — and spawned a throwaway culture. Add in poorly regulated petrochemical manufacturing processes and industrial fishing’s plastic gear, and global plastic pollution stats soared.
People have now produced some 11 billion metric tons of plastic. Globally, we discard 400 million tons of plastic waste every year; without controls imposed over production, that may reach 1.1 billion tons within the next 25 years.
It can take 500-1,000 years for plastic to break down, and scientists are beginning to question whether it ever fully degrades. Today, 50-75 trillion microplastic particles litter the seas, according to a United Nations estimate, 500 times more than all the stars in our Milky Way galaxy. Microscopic life in the ocean has been dubbed “the Plastisphere,” with early research finding that even phytoplankton, the food-web base vital to marine ecosystems, is under threat.
Plastic debris was first noticed in the oceans in the early 1960s. For a long time, ecologists’ main wildlife concerns focused on the threat to sea turtles and other marine creatures that ate plastic bags or became tangled in plastic fishing nets. Now, everything from zooplankton to sharks and seabirds eat it and are exposed to it.
Hart emphasizes the problem’s global scope: “Plastic pollution has been found on every continent and in every ocean, in people, terrestrial wildlife and marine wildlife.” It contaminates creatures across the tree of life and concentrates up the food chain, threatening every living thing, from insects, rodents, rhinos and frogs to clams, whales, snakes, wildcats and a host of migratory animals. Carried to the poles on wind and tide, even Arctic foxes and penguins carry microplastics.
Insidious plastic harm to health
It’s well known that animals regularly mistake plastic debris for food. Shearwaters and other seabirds, for example, can choke and starve when plastic pieces block their digestive tracts or pierce internal organs. At least 1,565 species are known to ingest plastic. For decades, scientists have noted dead animals ensnared in plastic nets, fishing gear or six-pack rings.
But those big pieces of petrochemical plastic (along with their chemical additives) don’t decompose; they degrade into ever-smaller pieces, getting smaller and smaller. Eventually they break down into microplastics, tiny particles no bigger than a grain of sand, or become nanoparticles, visible only under a high-powered microscope. These microplastics can leach toxic chemicals. Of the more than 13,000 chemicals currently used in plastics, at least 3,200 have one or more “hazardous properties of concern,” according to a U.N. report.
Most of what we know today about the health impacts of plastics and their chemical additives is based on human medical research, which may offer clues to what happens to animals; that’s unlike most health research, which is done on animals and extrapolated to people.
We know from human medical research that microplastics can damage cells and organs and alter hormones that influence their function. Plastic particles have crossed the blood-brain barrier. They have lodged in human bone marrow, testicles, the liver, kidneys and essentially every other part of the body. They enter the placenta, blood and breast milk. Exposure may affect behavior and lower immunity.
And what plastics do to us, they likely do to animals. The phthalates found in Florida dolphins, for example, along with phenols, parabens and per- and polyfluoroalkyls, are just a fraction of the many endocrine disruptors released by plastics and their chemical additives that can alter hormone levels and derail body functions. Exposure may affect behavior and lower immunity.
Doctors have confirmed links between plastic and human disease and disability. “They cause premature birth, low birth weight, and stillbirth as well as leukemia, lymphoma, brain cancer, liver cancer, heart disease and stroke,” Phil Landrigan, a pediatrician and environmental health expert stated in a press conference earlier this year.
Endocrine-disrupting chemicals can also interfere with reproduction in humans: They’re partially responsible for sperm counts that dropped to one-seventh of 1940s levels. These chemicals can also damage the placenta and ovaries. Experts think this is likely happening in animals, too, raising serious concern for endangered species already in decline.
In the wild, animals are now exposed daily to microplastics, eating and breathing them, while many freshwater and marine species swim in a plastic soup. But little is known about the long-term impacts of chronic exposure or what microplastics do within animal tissues, with even less understood about what happens when microplastics shrink to nano size and easily enter cells.
There are some data: Oysters produce fewer eggs. Pregnant zebrafish can pass nano-polystyrene to their embryos, while other research showed plastic exposure slowed fish larvae growth rates. Seabirds, including shearwaters, develop “plasticosis,” a newly declared disease characterized by thick scarring in the stomach due to plastic ingestion, which inhibits digestion. Microplastics also damage the heart structure of birds and permeate the liver, muscle and intestines in cod.
In lab experiments, microplastics in the lungs of pregnant rats easily passed to their fetuses’ brains, hearts and other organs. In adult mice, plastic nanoparticles crossed the blood-brain barrier, triggering swift changes that resembled dementia. In a wild animal, cognitive decline can quickly prove fatal, making it difficult to find food, avoid predators, mate or raise young.
In the lab, fish were more susceptible to a common virus after a one-month exposure to microplastic. They then shed more virus (a fish public health problem) and died in high numbers. Surprisingly, “there’s a lot of similarities between fish and humans, so that we have a lot of the same immune pathways,” explains Wargo, an author on this study. However, the reaction depended on the type of plastic. Nylon fibers had the biggest effect; most nylon sheds from synthetic clothing.
One challenge to researching health impacts, Wargo explains, is that “plastics oftentimes are lumped into one category, but they’re [all] very different: their structure, chemical composition, their shape and size,” creating thousands of variations. These factors influence how toxic they are, he says, which likely varies between individual animals and different species. Investigation is further complicated and obstructed by petrochemical companies that zealously guard their proprietary polymer product formulas.
The ubiquity of plastics and their global presence means that polymers likely have many undetected and unstudied wildlife health impacts. Some impacts could be masked by other environmental stressors, and untangling and analyzing the particulars will likely take decades.
What we do know is that the poor health, decline or disappearance of a single species within a natural community ripples outward, affecting others, damaging interconnected ecological systems that have evolved in synchrony over millennia. Here’s just one speculative concern: We know microplastics can bioaccumulate, so apex predators, which balance ecosystems by keeping prey species in check, may be at high risk because they consume and build up large concentrations of microplastics and additive chemicals in their organs.
Plastics harm wildlife –– and humans –– in additional ways: by polluting the air and contributing to climate extremes. Currently, about 19% of plastic waste is incinerated, releasing potentially harmful chemical aerosols into the air. In addition, plastic production sends 232 million metric tons of greenhouse gases into the atmosphere yearly. Then there’s the pollution and carbon released from fracking and drilling operations to source the oil and gas to make these products.
Lastly, the microplastics animals and humans ingest are “Trojan horses.” These tiny particles absorb and carry a wide range of pollutants and bacteria, which then can enter and lodge within our bodies.
Stanching ‘a global-scale deluge of plastic waste’
Climate change and the plastics crisis spring from the same source: The world’s seven largest plastic manufacturers are fossil fuel companies. The U.S. produces the most plastic waste of any country, more than the entire EU combined: 42 million metric tons annually, or 287 pounds per person, according to a 2022 congressional report. It noted that “The success of the 20th century miracle invention of plastics has also produced a global-scale deluge of plastic waste seemingly everywhere we look.”
Consumers can take small actions to protect themselves and limit plastic pollution by avoiding single-use plastics and carrying reusable bags and stainless-steel water bottles. Disposable fast-food packaging makes up almost half of plastic garbage in the ocean, so cutting back on takeout and bottled water could help.
But realistically addressing the planet’s plastics emergency requires a global paradigm shift that reframes the discussion. Many nations still think of plastics as a waste management issue, but responsibility needs to fall on the shoulders of regulators — and the producers, specifically fossil fuel companies and petrochemical manufacturers.
An international consortium of scientists has stressed the need for “urgent action” in the run up to this month’s United Nations plastics treaty negotiations, the fifth and hopefully final summit intended to establish international regulations.
The U.S. had been among the largest, most influential dissenters in efforts to limit global plastics production and identify hazardous chemicals used in plastics. But in August 2024, prior to the U.S. presidential election, the Biden administration publicly announced it had toughened its position, supporting production limits, but submitted no position paper. Then, this week it returned to its earlier stance that would protect the plastics industry from production caps.
The plastics treaty summit in Busan, South Korea, beginning Nov. 25 and ending Dec. 1, aims to finalize treaty language that will then need to be ratified by the world’s nations. Regardless of the summit’s outcome, scientists continue to uncover new evidence of plastic’s dangers to humans, animals and the planet, raising the alarm and need for action.
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This article by Sharon Guynup was first published by Mongabay.com on 21 November 2024. Lead Image: Research in Florida found that bottlenose dolphins are breathing and ingesting microplastic. Image by Victoria E. via Flickr (CC BY-NC 2.0).
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