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What Is Pollution Doing to Our Brains? 'Exposomics' Reveals Links to Many Diseases

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Friday, April 12, 2024

B1992, burgeoning population, choking traffic, and explosive industrial growth in Mexico City had caused the United Nations to label it the most polluted urban area in the world. The problem was intensified because the high-altitude metropolis sat in a valley trapping that atmospheric filth in a perpetual toxic haze. Over the next few years, the impact could be seen not just in the blanket of smog overhead but in the city’s dogs, who had become so disoriented that some of them could no longer recognize their human families. In a series of elegant studies, the neuropathologist Lilian Calderón-Garcidueñas compared the brains of canines and children from “Makesicko City,” as the capital had been dubbed, to those from less polluted areas. What she found was terrifying: Exposure to air pollution in childhood decreases brain volume and heightens risk of several dreaded brain diseases, including Parkinson’s and Alzheimer’s, as an adult.Calderón-Garcidueñas, today head of the Environmental Neuroprevention Laboratory at the University of Montana, points out that the damaged brains she documented through neuroimaging in young dogs and humans aren’t just significant in later years; they play out in impaired memory and lower intelligence scores throughout life. Other studies have found that air pollution exposure later in childhood alters neural circuitry throughout the brain, potentially affecting executive function, including abilities like decision-making and focus, and raising the risk of psychiatric disorders.The stakes for all of us are enormous. In places like China, India, and the rest of the global south, air pollution, both indoor and outdoor, has steadily soared over the course of decades. According to the United Nations Foundation, “nearly half of the world’s population breathes toxic air each day, including more than 90 percent of children.” Some 2.3 billion people worldwide rely on solid fuels and open fires for cooking, the Foundation adds, making the problem far worse. The World Health Organization calculates about 3 million premature deaths, mostly in women and children, result from air pollution created by such cooking each year.On supporting science journalismIf you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.In the United States, meanwhile, average air pollution levels have decreased significantly since the passage of the Clean Air Act in 1970. But the key word is average. Millions of Americans are still breathing outdoor air loaded with inflammation-triggering ozone and fine particulate matter. These particles, known as PM2.5 (particles less than 2.5 micrometers in diameter), can affect the lungs and heart and are strongly associated with brain damage. Wildfires—like the ones that raged across Canada this past summer—are a major contributor of PM2.5. A recent study showed that pesticides, paints, cleaners, and other personal care products are another major—and under-recognized—source of PM2.5 and can raise the risk for numerous health problems, including brain-damaging strokes.Untangling the relationship between air pollution and the brain is complex. In the modern industrial world, we are all exposed to literally thousands of contaminants. And not every person exposed to a given pollutant will develop the same set of symptoms, impairments, or diseases—in part because of their genes, and in part because each exposure may occur at a different point in development or impact a different area of the body or brain. What’s more, social disparities are at play: Poorer populations almost always live closer to factories, toxins, and pollutants.The effort to figure it out and intervene has sparked a new field of study: exposomics, the science of environmental exposures and their effects on health, disease, and development. Exposomics draws on enormous datasets about the distribution of environmental toxins, genetic and cellular responses, and human behavioral patterns. There is a huge amount of information to parse, so researchers in the field are turning to another emerging science, artificial intelligence, to make sense of it all.“Anything from our external environment—the air we breathe, food we eat, the water we drink, the emotional stress that we face every day—all of that gets translated into our biology,” says Rosalind Wright, professor of pediatrics and co-director of the Institute for Exposomic Research at the Icahn School of Medicine at Mount Sinai in New York. “All these things plus genes themselves explain the patterns of risk we see.” When an exposure is constant and cumulative, or when it overwhelms our ability to adapt, or “when you’re a fetus in utero, when you’re an infant or in early childhood or in a critical period of growth,” it can have a particularly powerful effect on lifelong cognitive clarity and brain health.Neuroscientist Megan Herting at the University of Southern California (USC) has been studying the impact of air pollution on the developing brain. “Over the past few years, we have found that higher levels of PM2.5 exposure are linked to a number of differences in the shape, neural architecture, and functional organization of the developing brain, including altered patterns of cortical thickness and differences in the microstructure of gray and white matter,” she says. On the basis of neuroimaging of exposed youngsters, Herting and fellow researchers suspect the widespread differences in brain structure and function linked with air pollution may be early biomarkers for cognitive and emotional problems emerging later in life.That suspicion gains support from an international meta-analysis (a study of other studies) published in 2023 that correlated exposure to air pollution during critical periods of brain development in childhood and adolescence to risk of depression and suicidal behavior. The imaging parts of the studies showed changes in brain structure, including neurocircuitry potentially involved in movement disorders like Parkinson’s, and white matter of the prefrontal lobes, responsible for executive decision-making, attention, and self-control.In a 2023 study, Herting and colleagues tracked children transitioning into adolescence, when brains are in a sensitive period of development and thus especially vulnerable to long-term damage from toxins. Among brain regions developing during this period is the prefrontal cortex, which helps with cognitive control, self-regulation, decision-making, attention, and problem-solving, Herting says. “Your emotional reward systems are also still being refined,” she adds.Looking at scan data from more than 9,000 youngsters exposed to air pollution between ages 9 and 10 and following them over the next couple of years, the researchers found changes in connectivity between brain regions, with some regions having fewer connections and others having more connections than normal. Herting explains that these structural and functional connections allow us to function in our daily lives, but how or even whether the changes in circuitry have an impact, researchers do not yet know.The specific pollutants involved in the atypical brain circuits appear to be nitrogen dioxide, ozone, and PM2.5—the small particles that worry many researchers the most. Herting explains: Limits set on fine particulate matter are stricter in the United States than in most other countries but still inadequate. The U.S. Environmental Protection Agency currently limits annual average levels of the pollutant to 12 micrograms per cubic meter and permits daily spikes of up to 35 micrograms per cubic meter. Health organizations, on the other hand, have called for the agency to lower levels to 8 micrograms and 25 micrograms per cubic meter, respectively. Thus, even though it may be “safe” by EPA standards, “air quality across America is contributing to changes in brain networks during critical periods of childhood,” Herting says. And that may augur “increased risk for cognitive and emotional problems later in life.” She plans to follow her group of young people into adulthood, when advances in science and the passage of time should reveal more about the effect of air pollution exposure during adolescence.Other research shows that air pollution increases risk of psychiatric disorder as years go by. In work based on large datasets in the United States and Denmark, University of Chicago computational biologist Andrey Rzhetsky and colleagues found that bad air quality was associated with increased rates of bipolar disorder and depression in both countries, especially when exposure occurs early in life. Rzhetsky and his team used two major sources: in Denmark, the National Health Registry, which contains health data on every citizen from cradle to grave; and in the United States, insurance claims with medical history plus details such as county of residence, age, sex, and importantly, linkages to family—specifics that helped reveal genetic predisposition to develop a psychiatric condition during the first 10 years of life.“It's possible that the same environment will cause disease in one person but not in another because of predisposing genetic variants that are different in different people,” Rzhetsky says. “The different genetic predisposition, that’s one part of the puzzle. Another part is varying environment.”Indeed, these complex diseases are spreading much faster than genetics alone seems to explain. “We definitely don’t know for sure which pollutant is causal. We can’t really pinpoint a smoking gun,” Rzhetsky says. But one pesky culprit continues to prove statistically significant: “It looks like PM2.5 is one of those strong signals.” To figure it out specifically, we’ll need much more data, and exposomics will play a vital role."This is a wake-up call,” Frances Jensen told her fellow physicians at the American Neurological Society’s symposium on Neurologic Dark Matter in October 2022. The meeting was an exploration of the exposome –the sum of external factors that a person is exposed to during a lifetime— driving neurodegenerative disease. It was focused in no small part on air pollution. Jensen, a University of Pennsylvania neurologist and president of the American Neurological Association, argued that researchers need to pay more attention to contaminants because the sharp rise in the number of Parkinson’s diagnoses cannot be explained by the aging population alone. “Environmental exposures are lurking in the background, and they’re rising,” she said.Parkinson’s disease is already the second-most common neurodegenerative disease after Alzheimer’s. Symptoms, which can include uncontrolled movements, difficulty with balance, and memory problems, generally develop in people age 60 and older, but they can occur, though rarely, in people as young as 20. Could something in the air explain the increasing worldwide prevalence of Parkinson’s? Researchers have not identified one specific cause, but they know Parkinson’s symptoms result from degeneration of nerve cells in the substantia nigra, the part of the brain that produces dopamine and other signal-transmitting chemicals necessary for movement and coordination.A host of air pollution suspects are now thought to play a role in the loss of dopamine-producing cells, according to Emory University environmental health scientist W. Michael Caudle, who uses mass spectrometry to identify chemicals in our bodies. One suspect he’s looking at are lipopolysaccharides, compounds often found in air pollution and bacterial toxins. Although lipopolysaccharides cannot directly enter the brain, they inflame the liver. The liver then releases inflammatory molecules into the bloodstream, which interact with blood vessels in the blood-barrier. “Then the inflammatory response in the brain leads to loss of dopamine neurons, like that seen in Parkinson’s disease,” Caudle says.More evidence comes from neuroepidemiologist Brittany Krzyzanowski, based at the Barrow Neurological Institute in Phoenix. Krzyzanowski had an “aha!” moment when she saw a map highlighting the high risk of Parkinson’s disease in the Mississippi–Ohio River Valley, including areas of Tennessee and Kentucky. At first she wondered whether the Parkinson’s hotspot was due to pesticide use in the region. But then it hit her: The area also had a network of high-density roads, suggesting that air pollution could be involved. “The pollution in these areas may contain more combustion particles from traffic and heavy metals from manufacturing, which have been linked to cell death in the part of the brain involved in Parkinson’s disease,” she said.In a study published in Neurology in October 2023, Krzyzanowski and colleagues, using sophisticated geospatial analytic techniques, went on to show that those with median levels of air pollution have a 56 percent greater risk of developing Parkinson’s disease compared to those living in regions with the lowest level of air pollution. Along with the Mississippi-Ohio River Valley, other hotspots included central North Dakota, parts of Texas, Kansas, eastern Michigan, and the tip of Florida. People living in the western half of the U.S. are at a reduced risk of developing Parkinson’s disease compared with the rest of the nation.As to the hotspot in the Mississippi-Ohio River Valley, Parkinson’s there is 25% higher than in areas with the lowest air particulate matter. Aside from that, Krzyzanowski and her research team noted something especially odd: Frequency of the disease rose with the level of pollution, but then it plateaued even as air pollution continued to soar. One reason could be that other air pollution-linked diseases, including Alzheimer’s, are masking the emergence of Parkinson’s; another reason could be an unusual form of PM2.5. “Regional differences in Parkinson’s disease might reflect regional differences in the composition of the particulate matter, and some areas may have particulate matter containing more toxic components compared to other areas,” Krzyzanowsk says. Tapping the tenets of exposomics, she expects to explore these issues in the months and years ahead.The hunt is on for the connections between environmental factors and Alzheimer’s as well. USC neurogerontologist Caleb Finch has spent years studying dementia, especially Alzheimer’s disease, which affects more than six million Americans. As with Parkinson’s, Alzheimer’s numbers are rising in the United State and much of the world. Degenerative changes in neurons become increasingly frequent after the age of 60, yet half of the people who make it to 100 will not get dementia. Many factors could explain those discrepancies. Air pollution may be an important one, Finch says.Researchers like Finch and his USC colleague Jiu-Chiuan Chen are joining forces to explore the connections between environmental neurotoxins and decline in brain health. It’s a challenging project, since air pollution levels and specific pollutants vary on fine scales and can change from hour to hour in many areas of the globe. On the basis of brain scans of hundreds of people over a range of geographic areas, this much we know: “People living in areas of high levels of air pollution and who have been studied on three continents showed accelerated arterial disease, heart attacks, and strokes, and faster cognitive decline,” Finch says.Not everyone reacts the same way when exposed to pollutants, of course. Greatest risk for Alzheimer’s seems to hit people who have a genetic variant known as apolipoprotein E (APOE4), which is involved in making proteins that help carry cholesterol and other types of fat in the bloodstream. About 25 percent of people have one copy of that gene, and 2 to 3 percent carry two copies. But inheriting the gene alone doesn’t determine a person’s Alzheimer’s risk. Environmental exposures count too.A recent study by Chen, Finch, and colleagues published in the Journal of Alzheimer’s Disease looked at associations between air pollution exposure and early signs of Alzheimer’s in 1,100 men, all around age 56 when the study began. By age 68, test subjects with high PM2.5 exposures had the worst scores in verbal fluency. People exposed to high levels of nitrogen dioxide (NO2) air pollution were also linked to worsened episodic memory. The men who had APOE4 genes had the worst scores in executive function. The evidence indicates that the process by which air pollution interacts with genetic risk to cause Alzheimer’s in later life may begin in the middle years, at least for men.A separate USC study of more than 2,000 women found that when air quality improved, cognitive decline in older women slowed. When exposure to pollutants like PM2.5 and NO2 dropped by a few micrograms per cubic foot a year over the course of six years, the women in the study tested as being a year or so younger than their real age. This suggests that when exposure air pollution is lowered, dementia risk can go down.In parallel, an international study by the Lancet Commission concluded that the risk of dementia, including Alzheimer’s, can be lowered by modifying or avoiding 12 risk factors: hypertension, hearing impairment, smoking, obesity, depression, low social contact, low level of education, physical inactivity, diabetes, excessive alcohol consumption, traumatic brain injury—and air pollution. Together, the 12 modifiable risk factors account for around 40 percent of worldwide dementias, which theoretically could be prevented or delayed.In light of all this, Finch and Duke University social scientist Alexander Kulminski have proposed the “Alzheimer’s disease exposome” to assess environmental factors that interact with genes to cause dementia. Where medicines have failed, exposomics just might help. Studies of Swedish twins show that half of individual differences in Alzheimer’s risk may be environmental, and thus modifiable; and while vast sums of research funding have been poured into the genetic roots of the disease, it could be that altering the exposome would provide a better preventive than all the ongoing drug trials to date. Environmental toxins broadly disrupt cell repair and protective mechanisms in the brain, the researchers point out. And factors like obesity and stress contribute to chronic inflammation, which likely damages neurons’ ability to function and communicate. The research framework of the Alzheimer's disease exposome offers a comprehensive, systematic approach to the environmental underpinnings of Alzheimer's risk over individuals’ lifespans—from the time they are pre-fertilized gametes to life as a fetus in the womb to childhood and beyond.For three decades, Rosalind Wright at Mount Sinai has wanted to trace critical problems in neurodevelopment and neurodegeneration to pollutants—from highway emissions to heavy metals to specific household chemicals and a host of other factors—but the mass of data has been overwhelming. With the advent of artificial intelligence (AI) and sophisticated neuroimaging technology, high-precision research using vast genomic databanks is finally possible. “I knew we needed to ask these kinds of questions, but I didn't have the tools to do it. Now we do and it’s very exciting,” Wright says.Using machine learning—an AI approach to data analysis—Wright looks at giant datasets that include the precise location of an individual’s residence as well as the myriad of pollutants he or she encounters. “It's no different fundamentally from other statistical models we use,” she says. “It’s just that this one has been developed to be able to take in bigger and bigger data, more and more types of exposures.” The resulting data breakdown should tell us which factors drive which types of risk for which people. That information will help people know where they should target their efforts to reduce exposures to risky pollutants, and ultimately how to lower risk of impairment and disease, brain or otherwise.The tools used by Wright and her colleagues are being trained on diseases like Alzheimer’s. If you put genes and the environment together, “you start to see who might be at higher risk and also what underlying mechanisms might be driving it in different ways in different populations,” Wright says. The exposome could also explains more subtle cognitive effects of pollution that may emerge over long periods, such as harms to attention, intelligence, and performance.To address environmental brain risks, it’s important to know which pollutants are present—another target of exposomic research. In the United States, the EPA has placed stationary environmental monitors all over our major cities, conducting daily measurements of small particulates from traffic and industry, along with secondary chemicals that emerge as a result. There are also thousands of satellites all over the globe calibrating heat waves that can alter how the pollutants react with each other.Pioneers like Wright are just starting to chart the terrain of environmental exposures that affect the brain. “As we measure more and more of the exposome, we may be able to tailor prevention and intervention strategies. New weapons include a silicone bracelet that we have in the laboratory. You wear it and it will tell us what pollutants you are exposed to,” Wright says. She also is exploring more ways to collect data on the toxins people have already encountered: “With a single strand of hair, we can tell you what you’ve been exposed to. Hair grows about a centimeter a month, so if we get a hair from a pregnant woman and she has nine centimeters of hair, we can go back a full nine months, over the entire life of the fetus. Or we can create a life-long exposome history when a child loses a tooth at age six.”“We're designed to be pretty resilient,” Wright adds. The problem comes when the exposures are chronic and accumulative and overwhelm our ability to adapt. We’re not going to fix everything, “but if I know more about myself than before, that empowers me to think, ‘I’m optimizing the balance, and I’m intervening as best I can.’ ”Additional reporting and editing was done by Margaret Hetherman.This story is part of a series of OpenMind essays, podcasts, and videos supported by a generous grant from the Pulitzer Center's Truth Decay initiative.This story originally appeared on OpenMind, a digital magazine tackling science controversies and deceptions.

The new science of "exposomics" shows how air pollution contributes to Alzheimer’s, Parkinson’s, bipolar disorder and other brain diseases

B1992, burgeoning population, choking traffic, and explosive industrial growth in Mexico City had caused the United Nations to label it the most polluted urban area in the world. The problem was intensified because the high-altitude metropolis sat in a valley trapping that atmospheric filth in a perpetual toxic haze. Over the next few years, the impact could be seen not just in the blanket of smog overhead but in the city’s dogs, who had become so disoriented that some of them could no longer recognize their human families. In a series of elegant studies, the neuropathologist Lilian Calderón-Garcidueñas compared the brains of canines and children from “Makesicko City,” as the capital had been dubbed, to those from less polluted areas. What she found was terrifying: Exposure to air pollution in childhood decreases brain volume and heightens risk of several dreaded brain diseases, including Parkinson’s and Alzheimer’s, as an adult.

Calderón-Garcidueñas, today head of the Environmental Neuroprevention Laboratory at the University of Montana, points out that the damaged brains she documented through neuroimaging in young dogs and humans aren’t just significant in later years; they play out in impaired memory and lower intelligence scores throughout life. Other studies have found that air pollution exposure later in childhood alters neural circuitry throughout the brain, potentially affecting executive function, including abilities like decision-making and focus, and raising the risk of psychiatric disorders.

The stakes for all of us are enormous. In places like China, India, and the rest of the global south, air pollution, both indoor and outdoor, has steadily soared over the course of decades. According to the United Nations Foundation, “nearly half of the world’s population breathes toxic air each day, including more than 90 percent of children.” Some 2.3 billion people worldwide rely on solid fuels and open fires for cooking, the Foundation adds, making the problem far worse. The World Health Organization calculates about 3 million premature deaths, mostly in women and children, result from air pollution created by such cooking each year.


On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.


In the United States, meanwhile, average air pollution levels have decreased significantly since the passage of the Clean Air Act in 1970. But the key word is average. Millions of Americans are still breathing outdoor air loaded with inflammation-triggering ozone and fine particulate matter. These particles, known as PM2.5 (particles less than 2.5 micrometers in diameter), can affect the lungs and heart and are strongly associated with brain damage. Wildfires—like the ones that raged across Canada this past summer—are a major contributor of PM2.5. A recent study showed that pesticides, paints, cleaners, and other personal care products are another major—and under-recognized—source of PM2.5 and can raise the risk for numerous health problems, including brain-damaging strokes.

Untangling the relationship between air pollution and the brain is complex. In the modern industrial world, we are all exposed to literally thousands of contaminants. And not every person exposed to a given pollutant will develop the same set of symptoms, impairments, or diseases—in part because of their genes, and in part because each exposure may occur at a different point in development or impact a different area of the body or brain. What’s more, social disparities are at play: Poorer populations almost always live closer to factories, toxins, and pollutants.

The effort to figure it out and intervene has sparked a new field of study: exposomics, the science of environmental exposures and their effects on health, disease, and development. Exposomics draws on enormous datasets about the distribution of environmental toxins, genetic and cellular responses, and human behavioral patterns. There is a huge amount of information to parse, so researchers in the field are turning to another emerging science, artificial intelligence, to make sense of it all.

“Anything from our external environment—the air we breathe, food we eat, the water we drink, the emotional stress that we face every day—all of that gets translated into our biology,” says Rosalind Wright, professor of pediatrics and co-director of the Institute for Exposomic Research at the Icahn School of Medicine at Mount Sinai in New York. “All these things plus genes themselves explain the patterns of risk we see.” When an exposure is constant and cumulative, or when it overwhelms our ability to adapt, or “when you’re a fetus in utero, when you’re an infant or in early childhood or in a critical period of growth,” it can have a particularly powerful effect on lifelong cognitive clarity and brain health.

Neuroscientist Megan Herting at the University of Southern California (USC) has been studying the impact of air pollution on the developing brain. “Over the past few years, we have found that higher levels of PM2.5 exposure are linked to a number of differences in the shape, neural architecture, and functional organization of the developing brain, including altered patterns of cortical thickness and differences in the microstructure of gray and white matter,” she says. On the basis of neuroimaging of exposed youngsters, Herting and fellow researchers suspect the widespread differences in brain structure and function linked with air pollution may be early biomarkers for cognitive and emotional problems emerging later in life.

That suspicion gains support from an international meta-analysis (a study of other studies) published in 2023 that correlated exposure to air pollution during critical periods of brain development in childhood and adolescence to risk of depression and suicidal behavior. The imaging parts of the studies showed changes in brain structure, including neurocircuitry potentially involved in movement disorders like Parkinson’s, and white matter of the prefrontal lobes, responsible for executive decision-making, attention, and self-control.

In a 2023 study, Herting and colleagues tracked children transitioning into adolescence, when brains are in a sensitive period of development and thus especially vulnerable to long-term damage from toxins. Among brain regions developing during this period is the prefrontal cortex, which helps with cognitive control, self-regulation, decision-making, attention, and problem-solving, Herting says. “Your emotional reward systems are also still being refined,” she adds.

Looking at scan data from more than 9,000 youngsters exposed to air pollution between ages 9 and 10 and following them over the next couple of years, the researchers found changes in connectivity between brain regions, with some regions having fewer connections and others having more connections than normal. Herting explains that these structural and functional connections allow us to function in our daily lives, but how or even whether the changes in circuitry have an impact, researchers do not yet know.

The specific pollutants involved in the atypical brain circuits appear to be nitrogen dioxide, ozone, and PM2.5—the small particles that worry many researchers the most. Herting explains: Limits set on fine particulate matter are stricter in the United States than in most other countries but still inadequate. The U.S. Environmental Protection Agency currently limits annual average levels of the pollutant to 12 micrograms per cubic meter and permits daily spikes of up to 35 micrograms per cubic meter. Health organizations, on the other hand, have called for the agency to lower levels to 8 micrograms and 25 micrograms per cubic meter, respectively. Thus, even though it may be “safe” by EPA standards, “air quality across America is contributing to changes in brain networks during critical periods of childhood,” Herting says. And that may augur “increased risk for cognitive and emotional problems later in life.” She plans to follow her group of young people into adulthood, when advances in science and the passage of time should reveal more about the effect of air pollution exposure during adolescence.

Other research shows that air pollution increases risk of psychiatric disorder as years go by. In work based on large datasets in the United States and Denmark, University of Chicago computational biologist Andrey Rzhetsky and colleagues found that bad air quality was associated with increased rates of bipolar disorder and depression in both countries, especially when exposure occurs early in life. Rzhetsky and his team used two major sources: in Denmark, the National Health Registry, which contains health data on every citizen from cradle to grave; and in the United States, insurance claims with medical history plus details such as county of residence, age, sex, and importantly, linkages to family—specifics that helped reveal genetic predisposition to develop a psychiatric condition during the first 10 years of life.

“It's possible that the same environment will cause disease in one person but not in another because of predisposing genetic variants that are different in different people,” Rzhetsky says. “The different genetic predisposition, that’s one part of the puzzle. Another part is varying environment.”

Indeed, these complex diseases are spreading much faster than genetics alone seems to explain. “We definitely don’t know for sure which pollutant is causal. We can’t really pinpoint a smoking gun,” Rzhetsky says. But one pesky culprit continues to prove statistically significant: “It looks like PM2.5 is one of those strong signals.” To figure it out specifically, we’ll need much more data, and exposomics will play a vital role.

"This is a wake-up call,” Frances Jensen told her fellow physicians at the American Neurological Society’s symposium on Neurologic Dark Matter in October 2022. The meeting was an exploration of the exposome –the sum of external factors that a person is exposed to during a lifetime— driving neurodegenerative disease. It was focused in no small part on air pollution. Jensen, a University of Pennsylvania neurologist and president of the American Neurological Association, argued that researchers need to pay more attention to contaminants because the sharp rise in the number of Parkinson’s diagnoses cannot be explained by the aging population alone. “Environmental exposures are lurking in the background, and they’re rising,” she said.

Parkinson’s disease is already the second-most common neurodegenerative disease after Alzheimer’s. Symptoms, which can include uncontrolled movements, difficulty with balance, and memory problems, generally develop in people age 60 and older, but they can occur, though rarely, in people as young as 20. Could something in the air explain the increasing worldwide prevalence of Parkinson’s? Researchers have not identified one specific cause, but they know Parkinson’s symptoms result from degeneration of nerve cells in the substantia nigra, the part of the brain that produces dopamine and other signal-transmitting chemicals necessary for movement and coordination.

A host of air pollution suspects are now thought to play a role in the loss of dopamine-producing cells, according to Emory University environmental health scientist W. Michael Caudle, who uses mass spectrometry to identify chemicals in our bodies. One suspect he’s looking at are lipopolysaccharides, compounds often found in air pollution and bacterial toxins. Although lipopolysaccharides cannot directly enter the brain, they inflame the liver. The liver then releases inflammatory molecules into the bloodstream, which interact with blood vessels in the blood-barrier. “Then the inflammatory response in the brain leads to loss of dopamine neurons, like that seen in Parkinson’s disease,” Caudle says.

More evidence comes from neuroepidemiologist Brittany Krzyzanowski, based at the Barrow Neurological Institute in Phoenix. Krzyzanowski had an “aha!” moment when she saw a map highlighting the high risk of Parkinson’s disease in the Mississippi–Ohio River Valley, including areas of Tennessee and Kentucky. At first she wondered whether the Parkinson’s hotspot was due to pesticide use in the region. But then it hit her: The area also had a network of high-density roads, suggesting that air pollution could be involved. “The pollution in these areas may contain more combustion particles from traffic and heavy metals from manufacturing, which have been linked to cell death in the part of the brain involved in Parkinson’s disease,” she said.

In a study published in Neurology in October 2023, Krzyzanowski and colleagues, using sophisticated geospatial analytic techniques, went on to show that those with median levels of air pollution have a 56 percent greater risk of developing Parkinson’s disease compared to those living in regions with the lowest level of air pollution. Along with the Mississippi-Ohio River Valley, other hotspots included central North Dakota, parts of Texas, Kansas, eastern Michigan, and the tip of Florida. People living in the western half of the U.S. are at a reduced risk of developing Parkinson’s disease compared with the rest of the nation.

As to the hotspot in the Mississippi-Ohio River Valley, Parkinson’s there is 25% higher than in areas with the lowest air particulate matter. Aside from that, Krzyzanowski and her research team noted something especially odd: Frequency of the disease rose with the level of pollution, but then it plateaued even as air pollution continued to soar. One reason could be that other air pollution-linked diseases, including Alzheimer’s, are masking the emergence of Parkinson’s; another reason could be an unusual form of PM2.5. “Regional differences in Parkinson’s disease might reflect regional differences in the composition of the particulate matter, and some areas may have particulate matter containing more toxic components compared to other areas,” Krzyzanowsk says. Tapping the tenets of exposomics, she expects to explore these issues in the months and years ahead.

The hunt is on for the connections between environmental factors and Alzheimer’s as well. USC neurogerontologist Caleb Finch has spent years studying dementia, especially Alzheimer’s disease, which affects more than six million Americans. As with Parkinson’s, Alzheimer’s numbers are rising in the United State and much of the world. Degenerative changes in neurons become increasingly frequent after the age of 60, yet half of the people who make it to 100 will not get dementia. Many factors could explain those discrepancies. Air pollution may be an important one, Finch says.

Researchers like Finch and his USC colleague Jiu-Chiuan Chen are joining forces to explore the connections between environmental neurotoxins and decline in brain health. It’s a challenging project, since air pollution levels and specific pollutants vary on fine scales and can change from hour to hour in many areas of the globe. On the basis of brain scans of hundreds of people over a range of geographic areas, this much we know: “People living in areas of high levels of air pollution and who have been studied on three continents showed accelerated arterial disease, heart attacks, and strokes, and faster cognitive decline,” Finch says.

Not everyone reacts the same way when exposed to pollutants, of course. Greatest risk for Alzheimer’s seems to hit people who have a genetic variant known as apolipoprotein E (APOE4), which is involved in making proteins that help carry cholesterol and other types of fat in the bloodstream. About 25 percent of people have one copy of that gene, and 2 to 3 percent carry two copies. But inheriting the gene alone doesn’t determine a person’s Alzheimer’s risk. Environmental exposures count too.

A recent study by Chen, Finch, and colleagues published in the Journal of Alzheimer’s Disease looked at associations between air pollution exposure and early signs of Alzheimer’s in 1,100 men, all around age 56 when the study began. By age 68, test subjects with high PM2.5 exposures had the worst scores in verbal fluency. People exposed to high levels of nitrogen dioxide (NO2) air pollution were also linked to worsened episodic memory. The men who had APOE4 genes had the worst scores in executive function. The evidence indicates that the process by which air pollution interacts with genetic risk to cause Alzheimer’s in later life may begin in the middle years, at least for men.

A separate USC study of more than 2,000 women found that when air quality improved, cognitive decline in older women slowed. When exposure to pollutants like PM2.5 and NO2 dropped by a few micrograms per cubic foot a year over the course of six years, the women in the study tested as being a year or so younger than their real age. This suggests that when exposure air pollution is lowered, dementia risk can go down.

In parallel, an international study by the Lancet Commission concluded that the risk of dementia, including Alzheimer’s, can be lowered by modifying or avoiding 12 risk factors: hypertension, hearing impairment, smoking, obesity, depression, low social contact, low level of education, physical inactivity, diabetes, excessive alcohol consumption, traumatic brain injury—and air pollution. Together, the 12 modifiable risk factors account for around 40 percent of worldwide dementias, which theoretically could be prevented or delayed.

In light of all this, Finch and Duke University social scientist Alexander Kulminski have proposed the “Alzheimer’s disease exposome” to assess environmental factors that interact with genes to cause dementia. Where medicines have failed, exposomics just might help. Studies of Swedish twins show that half of individual differences in Alzheimer’s risk may be environmental, and thus modifiable; and while vast sums of research funding have been poured into the genetic roots of the disease, it could be that altering the exposome would provide a better preventive than all the ongoing drug trials to date. Environmental toxins broadly disrupt cell repair and protective mechanisms in the brain, the researchers point out. And factors like obesity and stress contribute to chronic inflammation, which likely damages neurons’ ability to function and communicate. The research framework of the Alzheimer's disease exposome offers a comprehensive, systematic approach to the environmental underpinnings of Alzheimer's risk over individuals’ lifespans—from the time they are pre-fertilized gametes to life as a fetus in the womb to childhood and beyond.

For three decades, Rosalind Wright at Mount Sinai has wanted to trace critical problems in neurodevelopment and neurodegeneration to pollutants—from highway emissions to heavy metals to specific household chemicals and a host of other factors—but the mass of data has been overwhelming. With the advent of artificial intelligence (AI) and sophisticated neuroimaging technology, high-precision research using vast genomic databanks is finally possible. “I knew we needed to ask these kinds of questions, but I didn't have the tools to do it. Now we do and it’s very exciting,” Wright says.

Using machine learning—an AI approach to data analysis—Wright looks at giant datasets that include the precise location of an individual’s residence as well as the myriad of pollutants he or she encounters. “It's no different fundamentally from other statistical models we use,” she says. “It’s just that this one has been developed to be able to take in bigger and bigger data, more and more types of exposures.” The resulting data breakdown should tell us which factors drive which types of risk for which people. That information will help people know where they should target their efforts to reduce exposures to risky pollutants, and ultimately how to lower risk of impairment and disease, brain or otherwise.

The tools used by Wright and her colleagues are being trained on diseases like Alzheimer’s. If you put genes and the environment together, “you start to see who might be at higher risk and also what underlying mechanisms might be driving it in different ways in different populations,” Wright says. The exposome could also explains more subtle cognitive effects of pollution that may emerge over long periods, such as harms to attention, intelligence, and performance.

To address environmental brain risks, it’s important to know which pollutants are present—another target of exposomic research. In the United States, the EPA has placed stationary environmental monitors all over our major cities, conducting daily measurements of small particulates from traffic and industry, along with secondary chemicals that emerge as a result. There are also thousands of satellites all over the globe calibrating heat waves that can alter how the pollutants react with each other.

Pioneers like Wright are just starting to chart the terrain of environmental exposures that affect the brain. “As we measure more and more of the exposome, we may be able to tailor prevention and intervention strategies. New weapons include a silicone bracelet that we have in the laboratory. You wear it and it will tell us what pollutants you are exposed to,” Wright says. She also is exploring more ways to collect data on the toxins people have already encountered: “With a single strand of hair, we can tell you what you’ve been exposed to. Hair grows about a centimeter a month, so if we get a hair from a pregnant woman and she has nine centimeters of hair, we can go back a full nine months, over the entire life of the fetus. Or we can create a life-long exposome history when a child loses a tooth at age six.”

“We're designed to be pretty resilient,” Wright adds. The problem comes when the exposures are chronic and accumulative and overwhelm our ability to adapt. We’re not going to fix everything, “but if I know more about myself than before, that empowers me to think, ‘I’m optimizing the balance, and I’m intervening as best I can.’ ”

Additional reporting and editing was done by Margaret Hetherman.

This story is part of a series of OpenMind essays, podcasts, and videos supported by a generous grant from the Pulitzer Center's Truth Decay initiative.

This story originally appeared on OpenMind, a digital magazine tackling science controversies and deceptions.

Read the full story here.
Photos courtesy of

Mercury contamination in Grassy Narrows worsens due to ongoing pollution

A recent study highlights that industrial pollution is increasing methylmercury levels in the Grassy Narrows region, exacerbating a decades-old environmental health crisis.Sarah Law reports for CBC News.In short:New research indicates that wastewater discharge from the Dryden Paper Mill has intensified mercury contamination in northwestern Ontario’s English-Wabigoon River.The methylmercury, more toxic than other forms, accumulates in fish and affects the health of Grassy Narrows residents who rely on fish as a dietary staple.The federal government has committed $77M to build a Mercury Care Home, with construction starting this summer, to support affected individuals.Key quote: "We continue to be poisoned." — Rudy Turtle, Chief of Grassy Narrows First NationWhy this matters: Mercury poisoning poses severe health risks, including neuromuscular problems and cognitive dysfunction. Addressing this ongoing pollution is crucial for the well-being of the Grassy Narrows community and reflects broader environmental justice issues. Read more: Whose job is it to reduce toxic mercury in the Ohio River?

A recent study highlights that industrial pollution is increasing methylmercury levels in the Grassy Narrows region, exacerbating a decades-old environmental health crisis.Sarah Law reports for CBC News.In short:New research indicates that wastewater discharge from the Dryden Paper Mill has intensified mercury contamination in northwestern Ontario’s English-Wabigoon River.The methylmercury, more toxic than other forms, accumulates in fish and affects the health of Grassy Narrows residents who rely on fish as a dietary staple.The federal government has committed $77M to build a Mercury Care Home, with construction starting this summer, to support affected individuals.Key quote: "We continue to be poisoned." — Rudy Turtle, Chief of Grassy Narrows First NationWhy this matters: Mercury poisoning poses severe health risks, including neuromuscular problems and cognitive dysfunction. Addressing this ongoing pollution is crucial for the well-being of the Grassy Narrows community and reflects broader environmental justice issues. Read more: Whose job is it to reduce toxic mercury in the Ohio River?

Congestion Pricing Could Bring Cleaner Air. But Maybe Not for Everyone.

Officials expect New York City’s new tolling system to reduce air pollution, as well as carbon emissions. The impact may be uneven.

When congestion pricing takes effect in New York City next month, officials say it will create an array of benefits: The system’s tolls will generate revenue for improving mass transit while prompting some drivers to avoid Manhattan, potentially reducing traffic and air pollution, as well as carbon emissions that contribute to climate change.Some of those goals are already within sight: Devices that will monitor cars and send bills to drivers are in place, and the Metropolitan Transportation Authority, which will operate the system, has begun to detail the transit repairs and upgrades it plans to spend its windfall on.For now, though, it is unclear how much the program will contribute to New York State’s ambitious goal of reducing greenhouse emissions 85 percent by 2050. And some people worry that less air pollution in some areas will be offset by more in others, despite efforts to keep that from happening.According to an environmental assessment by the authority, congestion pricing could decrease air pollution overall in three boroughs: Manhattan, Brooklyn and Queens. The concern is that rerouted traffic could increase it in the Bronx and on Staten Island.“It’s safe to say the direct air-quality benefits would be modest but measurable overall,” said Eric A. Goldstein, a senior attorney and New York City environment director at the Natural Resources Defense Council. The plan, he added, is worthwhile because of its benefits for public transit, whose health is crucial for luring people away from private vehicles.“If you look at London and Stockholm, they had improved traffic, modest air quality, and jolts of adrenaline to their transportation systems,” he said, referring to similar programs in those cities.Subscribe to The Times to read as many articles as you like.

Cape Cod Weighs Big-Ticket Pollution Solutions

Toxic algal blooms are forcing Cape Cod communities to consider expensive sewer and septic system projects.

This story was co-published with WBUR in Boston and produced with assistance from the Pulitzer Center. Read WBUR’s coverage of efforts to improve Cape Cod’s water pollution, including a “pee-cycling” project being considered by one innovative town. And check out a documentary short exploring these issues that was co-produced by WBUR and Scientific American.[CLIP: Theme music]Rachel Feltman: Cape Cod’s ponds and bays have suffered from decades of pollution. But scientific detective work has finally pinpointed the worst culprit: human urine. When household septic systems flush nitrogen and other nutrients into the water, they provide an all-you-can-eat buffet for algae blooms. More algae means less sunlight and oxygen for other marine life, which means trouble for the people of Cape Cod.On supporting science journalismIf you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.For Science Quickly, I’m Rachel Feltman. Today we’re bringing you the second installment in our three-part Fascination series on Cape Cod’s yellow tide. In this episode WBUR environmental correspondent Barbara Moran looks at some of the big-ticket pollution solutions up for consideration—and unpacks why they’re so controversial.So without further ado, here’s part two: “Sticker Shock.”[CLIP: Gerard Martin speaks at a Massachusetts Department of Environmental Protection (MassDEP) hearing: “All right, excuse me, everybody, I think we’re gonna get going.”]Barbara Moran: Starting in late 2022 and continuing into the next year, concerned residents gathered for a series of public meetings with representatives from the Massachusetts Department of Environmental Protection. The residents were there to share their thoughts.[CLIP: Martin continues to speak at the hearing: “The hearing is being recorded and conducted in a hybrid format.”]Moran: The state was proposing new rules that would require communities to reduce their nitrogen pollution. In some places that meant people would potentially have to install new $35,000 septic systems. Here’s what Frank King of Brewster, Massachusetts, had to say about that.[CLIP: Frank King speaks at the MassDEP hearing: “If that is correct, you are looking at a massive protest on the scale of another Boston Tea Party.”][CLIP: Chris Shanahan speaks at the MassDEP hearing: “Thirty or thirty-five thousand dollars a year? That’s a complete misrepresentation.”]Moran: That’s Chris Shanahan of Falmouth, Massachusetts.[CLIP: Shanahan continues to speak at the hearing: “You can buy a system for that. You gotta maintain it. You gotta fix parts. It just never ends. So lifetime expense is more like eighty or a hundred thousand over 30 years.”][CLIP: Joan Hutchings speaks at the MassDEP hearing: “I’m not somebody that has a McMansion. I’ve got a three-bedroom home that’s been in my family for a bazillion years.”]Moran: Joan Hutchings of North Truro, Massachusetts. She said her town already made her upgrade her septic system.[CLIP: Hutchings continues to speak at the hearing: “Now the state’s gonna have me do something else? I don’t know, I might put an outhouse out back—seriously.”]Moran: People are concerned about the cost, as you heard. But they’re also concerned about whether these new systems even work. Can they actually prevent water pollution? I wondered the same thing. So I went to see an expert.Brian Baumgaertel: My name is Brian Baumgaertel. I’m the director of the Massachusetts Alternative Septic System Test Center.Moran: You met Brian briefly in Episode One. Now we’re on his home turf: a two-and-a-half acre outdoor laboratory on Cape Cod known as MASSTC.Brian’s team is on a mission to find the best septic systems in the world—and it’s not a job for the squeamish.[CLIP: Sound of wastewater channel]Moran (tape): All right, so I’m looking into this hole, and there’s, like, water pouring in and some scummy stuff floating around there.Baumgaertel: Yeah, that’s the raw wastewater coming in from Joint Base Cape Cod. And it doesn’t look like what most people would think of when—you know, when you’re thinking of wastewater, you think it’s pretty disgusting. I—you know, maybe I’ve just gotten so used to it. I don’t know.Moran (tape): It is a little disgusting. [Laughs]Baumgaertel: It’s got kind of a smell. You know, it’s one of the less glorious parts of MASSTC, but it’s a necessity. [Laughs] It’s brown gold, brown gold for us.Moran: MASSTC uses that brown gold to test prototype septic systems from all over the world. I ask Brian to show me one—although it’s hard to see much at the facility.Baumgaertel: A lot of what we do here is underground because of course, for the most part, septic systems in homes would be underground.Moran: Brian walks over to a grassy mound that looks weirdly like a burial site—which it is, actually. He says that buried underneath our feet is a new kind of septic system that removes nitrogen from wastewater.Here’s how it works: Wastewater flows into a tank, and all the solid stuff sinks to the bottom. The liquid left floating on top includes our pee, which is rich in nitrogen, phosphorus and other nutrients. This liquid flows out of the tank …Baumgaertel: And then flows into the actual unit itself …Moran (tape): Another tank that’s under our feet.Baumgaertel: Yep, yep. There’s another tank that’s about 12 feet long right here.Moran (tape): Okay.Baumgaertel: And inside that tank are a number of compartments.Moran: The compartments contain limestone rocks and wood chips. These ingredients create a breeding ground for bacteria that eat nitrogen. They convert it into harmless nitrogen gas before it gets into the groundwater.Other systems remove nitrogen in different ways. Brian and his team test the water coming out of each system to see how well it works. And he says this one has been working pretty well.Baumgaertel: So far the data look very encouraging. Every day we get a little bit more data, we get a little bit more confidence that the technology can work.[CLIP: “We Are Giants,” by Silver Maple]Moran: Others are also heartened by the data, including Zenas Crocker, who goes by Zee. He’s executive director of the nonprofit Barnstable Clean Water Coalition.Zenas Crocker: And this system is so successful that in the data that we’re seeing now, it will remove between 95 and 97 percent of nitrogen going into the groundwater.Moran: Zee’s group was so impressed with how well these systems remove nitrogen that it launched a pilot project. The group is installing more than a dozen in a neighborhood by Shubael Pond in Barnstable, Massachusetts—including one when I visited last September.[CLIP: Sound of chains being attached to a tank, followed by it being lifted]Moran: As we watch, a crane operator uses chains to lift a concrete tank and lower it into a hole in the ground.[CLIP: Sound of the tank being lowered and men talking]Moran: Zee’s group is working with the Environmental Protection Agency and the U.S. Geological Survey to monitor how well the new systems keep nitrogen out of the groundwater.Crocker: We chose this location in particular because these are all small lots. We’re also in a working-class community. Generally we’re looking at full-time residents here and people who really can’t afford, necessarily, to upgrade their septic systems.Moran: The Barnstable Clean Water Coalition paid to install the systems in this neighborhood; the homeowners paid nothing—which won’t be an option for the whole cape.But there is another approach to stopping wastewater pollution: switching from septic tanks to sewage pipes, which would bring the waste to a treatment plant. And that’s what Barnstable is doing in other parts of the town.I went to Barnstable’s town hall to meet the guy in charge.Moran (tape): Hi, how’re you doing? I have a nine o’clock interview with Mark Ells.Receptionist: Okay, sure, he’ll be right with you.Moran: Mark Ells is Barnstable’s town manager.Mark Ells: We’ve seen a significant deterioration of our bays to the point where we don’t have shellfish, we don’t have finfish. So we want to make sure that we put in place solutions that help us to address not only what we know today but what we’re anticipating tomorrow.Moran: Barnstable is the largest town on the cape, and parts are pretty urban, with houses and commercial buildings relatively close together. In places like this, sewer systems are a practical and cost-effective choice.So the town has begun a massive expansion of its sewer system, planning to extend service to almost 12,000 properties.[CLIP: “Let There Be Rain,” by Silver Maple]It’ll take 30 years and cost more than $1 billion. The town got local, state and federal funding to help cover the expansion costs. But homeowners will still have to pay.First there’s a town assessment of up to $10,000. Then homeowners have to pay to get their house hooked up to the sewer line and pay for someone to deal with their old septic tank. And then they’ll have a monthly sewer bill. The final cost, spread over decades, is probably in the range of $20,000 to $30,000—or more—per house.[CLIP: Construction sounds]Moran: And there’s another cost to installing sewer lines: seemingly constant roadwork and traffic jams.One day last fall cars crawled along as superintendent Mike Donovan’s crew dug up the main road into Barnstable.Moran (tape): Is this going to be, like, what your company does for, like, the next three decades?Mike Donovan: We—well, hopefully, yeah. That’s what we do for a living. We’re installing sewer all over the cape right now.Moran: But even this ambitious, expensive sewer expansion will take decades to reach some neighborhoods in Barnstable.Pat Uhlman lives across the street from Shubael Pond. And she’s seen it turn green with toxic algae. She says a few decades is too long to keep polluting the water.Pat Uhlman: If we don’t start cleaning it up now, you know, you might not even want to walk down by that pond by then.Moran: Luckily Pat is part of the neighborhood pilot project that got new septic systems installed for free. She says she understands that other homeowners are feeling sticker shock, but the pollution has to stop.Uhlman: The cape economy is still people coming here in the summer. So if they can’t swim in our ponds, they can’t swim in our ocean, they can’t boat, there’s not gonna be any reason for them to come here.[CLIP: Theme music]Moran: There may be another solution, a cheaper one. It won’t solve all the cape’s water problems, but it could help—a lot. We’ll talk about that next week in the final part of this Scientific American–WBUR Fascination miniseries.Feltman: Thanks for listening. Tune in next Friday for the final installment in this miniseries—which, spoiler alert, involves a little something called “pee-cycling.” You don’t want to miss it.Can’t wait for next Friday to get here? Don’t worry. We are taking Monday off for Memorial Day, but we’ll be back in your feed on Wednesday with some tips for protecting wildlife from the comfort of your own backyard.This series is a co-production of WBUR and Scientific American. It’s reported and hosted by WBUR’s Barbara Moran.Science Quickly is produced by Jeff DelViscio, Kelso Harper, Madison Goldberg and Rachel Feltman. Our theme music was composed by Dominic Smith. Shayna Posses and Aaron Shattuck fact-checked this series, and Duy Linh Tu and Sebastian Tuinder contributed reporting and sound. WBUR’s Kathleen Masterson edited this series. Additional funding was provided by the Pulitzer Center.For Scientific American’s Science Quickly, I’m Rachel Feltman.

New Plant-Based Plastic Releases 9 Times Less Microplastics

Recent research shows that plant-based plastics release far fewer microplastics than traditional plastics in marine environments, suggesting they could be a more environmentally friendly option....

A study by the University of Portsmouth and the Flanders Marine Institute has found that a plant-based plastic material emits significantly fewer microplastics than traditional plastic when subjected to sunlight and seawater. The research highlights the resilience of bio-based plastics and emphasizes the need for further investigation into their environmental impact, particularly in marine settings. Despite the promising results, the release of any microplastics remains concerning, pointing to a continued need for innovation and stricter environmental policies.Recent research shows that plant-based plastics release far fewer microplastics than traditional plastics in marine environments, suggesting they could be a more environmentally friendly option. However, continued research is crucial to fully assess their impact.A recent study has discovered that a new plant-based plastic material releases nine times fewer microplastics compared to traditional plastic when subjected to sunlight and seawater. Conducted by researchers from the University of Portsmouth and the Flanders Marine Institute (VLIZ) in Belgium, the study examined the degradation of two different types of plastic under harsh conditions.A bio-based plastic material made from natural feedstocks held up better when exposed to intense UV light and seawater for 76 days – the equivalent of 24 months of sun exposure in central Europe – than a conventional plastic made from petroleum derivatives. Environmental Impacts of Bio-Based PlasticsProfessor of Mechanical Engineering, Hom Dhakal, from the University’s School of Mechanical and Design Engineering, and a member of Revolution Plastics said: “Bio-based plastics are gaining interest as alternatives to conventional plastics, but little is known about their potential source of microplastics pollution in the marine environment.Professor Hom Dhakal. Credit: University of Portsmouth“It’s important to understand how these materials behave when they’re exposed to extreme environments, so we can predict how they’ll work when they’re used in marine applications, like building a boat hull, and what impact they might have on ocean life.“By knowing the effect of different types of plastics on the environment, we can make better choices to protect our oceans.”According to the Plastic Oceans International Organization, the equivalent of a truckload of plastic is poured into the oceans every minute of the day. When this plastic waste is exposed to the environment, it breaks down into smaller particles that are less than 5mm in size.These particles are known as ‘microplastics’ and have been observed in most marine ecosystems, posing a serious threat to aquatic life.“We wanted to look at a conventional industrial polymer, polypropylene, which is non-biodegradable and difficult to recycle, against polylactic acid (PLA), a biodegradable polymer,” Professor Dhakal explained.“Although our findings show that the PLA released fewer microplastics, which means using plant-based plastics instead of oil-based ones might seem like a good idea to reduce plastic pollution in the ocean, we need to be careful as microplastics are still clearly being released and that remains a concern.”Research Findings and Future DirectionsThe research also found that the size and shape of the tiny plastic pieces released depended on the type of plastic. The conventional plastic released smaller pieces and had fewer fiber-like shapes compared to the plant-based plastic.Professor Dhakal added: “Overall our research provides valuable insights into the behavior of different plastic types under environmental stressors, which is important for our future work to tackle plastic pollution. There is a clear need for continued research and proactive measures to mitigate the impact of microplastics on marine ecosystems.”Reference: “Accelerated fragmentation of two thermoplastics (polylactic acid and polypropylene) into microplastics after UV radiation and seawater immersion” by Zhiyue Niu, Marco Curto, Maelenn Le Gall, Elke Demeyer, Jana Asselman, Colin R Janssen, Hom Nath Dhakal, Peter Davies, Ana Isabel Catarino and Gert Everaert, 19 January 2024, Ecotoxicology and Environmental Safety.DOI: 10.1016/j.ecoenv.2024.115981Professor Dhakal is a member of the Revolution Plastics initiative that has been instrumental in informing national and global policies on plastics, pioneering advanced enzyme recycling techniques, and contributing to critical discussions on the UN treaty to end plastic pollution.The study was led by experts from the Flanders Marine Institute (VLIZ), in Belgium, under collaborative international work within the SeaBioComp project, which received funding from the Interreg 2 Seas Programme co-funded by the European Regional Development Fund.

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