Every breath you take: Study models the journey of inhaled plastic particle pollution

With recent studies having established the presence of nano and microplastic particles in the respiratory systems of both human and bird populations, a new University of Technology Sydney (UTS) study has modelled what happens when people breathe in different kinds of plastic particles and where they end up.

Led by Senior Lecturer of Mechanical Engineering Dr Suvash Saha, the UTS research team has used computational fluid-particle dynamics (CFPD) to study the transfer and deposition of particles of different sizes and shapes depending on the rate of breathing.

The results of the modelling, published in the journal Environmental Advances, have pinpointed hotspots in the human respiratory system where plastic particles can accumulate, from the nasal cavity and larynx and into the lungs.

Dr Saha said evidence was mounting on the significant impact of nano and microplastics on respiratory health and the UTS study would provide essential insights for the development of targeted strategies to mitigate potential risks and ensure effective health interventions.

"Experimental evidence has strongly suggested that these plastic particles amplify human susceptibility to a spectrum of lung disorders, including chronic obstructive pulmonary disease, fibrosis, dyspnea (shortness of breath), asthma, and the formation of what are called frosted glass nodules," Dr Saha said.

"Plastic particle air pollution is now pervasive and inhalation ranks as the second most likely pathway for human exposure.

"The primary types are intentionally manufactured, including a wide array of cosmetics and personal care products such as toothpaste.

"The secondary ones are fragments derived from the degradation of larger plastic products, such as water bottles, food containers and clothes.

"Extensive investigations have identified synthetic textiles as a principal source of indoor airborne plastic particles, while the outdoor environment presents a multitude of sources encompassing contaminated aerosols from the ocean to particles originating from wastewater treatment."

Dr Saha said the UTS team's modelling found that breathing rate along with particle size and shape determined where in the respiratory system plastic particles would be deposited.

"Faster breathing rates led to heightened deposition in the upper respiratory tract, particularly for larger microplastics, whereas slower breathing facilitated deeper penetration and deposition of smaller nanoplastic particles," he said.

"Particle shape was another factor, with non-spherical microplastic particles showing a propensity for deeper lung penetration compared to spherical microplastics and nanoplastics, potentially leading to different health outcomes.

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Ocean floor a 'reservoir' of plastic pollution

New research from CSIRO, Australia's national science agency, and the University of Toronto in Canada, estimates up to 11 million tonnes of plastic pollution is sitting on the ocean floor.

Every minute, a garbage truck's worth of plastic enters the ocean.

With plastic use expected to double by 2040, understanding how and where it travels is crucial to protecting marine ecosystems and wildlife.

Dr Denise Hardesty, Senior Research Scientist with CSIRO, said this is the first estimate of how much plastic waste ends up on the ocean floor, where it accumulates before being broken down into smaller pieces and mixed into ocean sediment.

"We know that millions of tonnes of plastic waste enter our oceans every year but what we didn't know is how much of this pollution ends up on our ocean floor," Dr Hardesty said.

"We discovered that the ocean floor has become a resting place, or reservoir, for most plastic pollution, with between 3 to 11 million tonnes of plastic estimated to be sinking to the ocean floor.

"While there has been a previous estimate of microplastics on the seafloor, this research looks at larger items, from nets and cups to plastic bags and everything in between."

Ms Alice Zhu, a PhD Candidate from the University of Toronto who led the study, said the estimate of plastic pollution on the ocean floor could be up to 100 times more than the amount of plastic floating on the ocean's surface based on recent estimates.

"The ocean surface is a temporary resting place of plastic so it is expected that if we can stop plastic entering our oceans, the amount would be reduced," Ms Zhu said.

"However, our research found that plastic will continue to end up in the deep ocean, which becomes a permanent resting place or sink for marine plastic pollution,"

Scientific data was used to build two predictive models to estimate the amount and distribution of plastic on the ocean floor -- one based on data from remote operated vehicles (ROVs) and the other from bottom trawls.

Using ROV data, 3 to 11 million metric tonnes of plastic pollution is estimated to reside on the ocean floor.

The ROV results also reveal that plastic mass clusters around continents -- approximately half (46 per cent) of the predicted plastic mass on the global ocean floor resides above 200 m depth.

The ocean depths, from 200 m to as deep as 11,000 m contains the remainder of predicted plastic mass (54 per cent).

Although inland and coastal seas cover much less surface area than oceans (11 per cent vs 56 per cent out of the entire Earth's area), these areas are predicted to hold as much plastic mass as does the rest of the ocean floor.

"These findings help to fill a longstanding knowledge gap on the behaviour of plastic in the marine environment," Ms Zhu said.

"Understanding the driving forces behind the transport and accumulation of plastic in the deep ocean will help to inform source reduction and environmental remediation efforts, thereby reducing the risks that plastic pollution may pose to marine life."

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Scientists develop artificial 'worm gut' to break down plastics

A team of scientists from Nanyang Technological University, Singapore (NTU Singapore) has developed an artificial 'worm gut' to break down plastics, offering hope for a nature-inspired method to tackle the global plastic pollution problem.

By feeding worms with plastics and cultivating microbes found in their guts, researchers from NTU's School of Civil and Environmental Engineering (CEE) and Singapore Centre for Environmental Life Sciences Engineering (SCELSE) have demonstrated a new method to accelerate plastic biodegradation.

Previous studies have shown that Zophobas atratus worms -- the larvae of the darkling beetle commonly sold as pet food and known as 'superworms' for their nutritional value -- can survive on a diet of plastic because its gut contains bacteria capable of breaking down common types of plastic.

However, their use in plastics processing has been impractical due to the slow rate of feeding and worm maintenance.

NTU scientists have now demonstrated a way to overcome these challenges by isolating the worm's gut bacteria and using them to do the job without the need for large scale worm breeding.

NTU Associate Professor Cao Bin at the School of CEE and Principal Investigator at SCELSE said, "A single worm can only consume about a couple of milligrams of plastic in its lifetime, so imagine the number of worms that would be needed if we were to rely on them to process our plastic waste. Our method eliminates this need by removing the worm from the equation. We focus on boosting the useful microbes in the worm gut and building an artificial 'worm gut' that can efficiently break down plastics."

The study, published in Environment International in January, is aligned with the University's commitment to fostering innovation and translating research into practical solutions that benefit society under its NTU2025 five-year strategic plan.

Developing an artificial worm gut

To develop their method, the NTU scientists fed three groups of superworms different plastic diets -- High-density polyethylene (HDPE), Polypropylene (PP) and Polystyrene (PS) -- over 30 days.

The control group was fed a diet of oatmeal.

The NTU scientists selected the plastics as they are among the most common plastics in the world, used in everyday items like food boxes and detergent bottles.

HDPE is a type of plastic known for its high-impact resistance, making it difficult to break down.

After feeding the worms plastic, scientists extracted the microbiomes from their gut and incubated them in flasks containing synthetic nutrients and different types of plastics, forming an artificial 'worm gut'. Over six weeks, the microbiomes were left to grow in the flasks at room temperature.

Increase in plastic-degrading bacteria

The scientists found that compared to the control group, the flasks which contained the gut microbiomes from the plastic-fed worms showed a significant increase in plastic-degrading bacteria.

Furthermore, the microbial communities colonising the plastics in the flasks were simpler and more tailored to the specific type of plastic than the microbes found on plastics that had been fed directly to the worms . When the microbial communities are simpler and targeted to a specific type of plastic, this translates to potential for more efficient plastic degradation when used in real-life applications.

First author of the study Dr Liu Yinan, Research Fellow at the School of CEE and SCELSE, said, "Our study represents the first reported successful attempt to develop plastic-associated bacterial communities from gut microbiomes of plastic-fed worms. Through exposing the gut microbiomes to specific conditions, we were able to boost the abundance of plastic-degrading bacteria present in our artificial 'worm gut,' suggesting that our method is stable and replicable at scale."

The researchers say their proof-of-concept lays the foundation for developing biotechnological approaches that use worms' gut microbiomes to process plastic waste.

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A sea change for plastic pollution: New material biodegrades in ocean water

Plastics, now ubiquitous in the modern world, have become a rising threat to human and environmental health. Around the planet, evidence of plastic pollution stretches from grocery bags in the deep sea to microplastics in our food supplies and even in our blood.

Seeking solutions to counteract the rise in plastic trash, scientists at the University of California San Diego have developed new biodegradable materials that are designed to replace conventionally used plastic. After proving their polyurethane foams biodegrade in land-based composts, an interdisciplinary team of scientists including UC San Diego biologist Stephen Mayfield and chemists Michael Burkart and Robert "Skip" Pomeroy have now shown that the material biodegrades in seawater. The results are published in the journalScience of the Total Environment.

The researchers are working to address a plastic pollution problem now described as a global environmental crisis. In 2010, researchers estimated that 8 billion kilograms of plastic enter the ocean in a single year, with a steep escalation predicted by 2025. Upon entering the ocean, plastic waste disrupts marine ecosystems, migrates to central locations and forms trash gyres such as the Great Pacific Garbage Patch, which covers an area more than 1.6 million square kilometers. These plastics never degrade, but rather break up into ever-smaller particles, eventually becoming microplastics that persist in the environment for centuries.

Working with study coauthor Samantha Clements, a marine biologist and scientific diver at Scripps Institution of Oceanography, the UC San Diego researchers conducted a series of tests of their biodegradable polyurethane materials -- currently used as foams in the first commercially available biodegradable shoes (sold by a spinoff company called Blueview) -- at Scripps' Ellen Browning Scripps Memorial Pier and Experimental Aquarium. The pier's location provided scientists the access and a unique opportunity to test materials in the natural nearshore ecosystem, which is the exact environment where rogue plastics are most likely to end up.

The team found that an assortment of marine organisms colonizes on the polyurethane foam and biodegrades the material back to their starting chemicals, which are consumed as nutrients by these microorganisms, in the ocean environment. Data from the study suggest that the microorganisms, a mix of bacteria and fungi, live throughout the natural marine environment.

"Improper disposal of plastic in the ocean breaks down into microplastics and has become an enormous environmental problem," said Mayfield, a professor in the School of Biological Sciences and director of the California Center for Algae Biotechnology. "We've shown that it's absolutely possible to make high performance plastic products that also can degrade in the ocean. Plastics should not be going into the ocean in the first place, but if they do, this material becomes food for microorganisms and not plastic trash and microplastics that harm aquatic life."

Shoes, including flip-flops, the world's most popular shoe, make up a large percentage of plastic waste that ends up in the world's oceans and landfills. To fully test and analyze their polyurethane materials, developed at UC San Diego over the last eight years, the study joined experts in biology, polymer and synthetic chemistry and marine science. Foam samples were exposed to tidal and wave dynamics and tracked for molecular and physical changes using Fourier-transform infrared spectroscopy and scanning electron microscopy. The results showed that the material started to degraded in as little as four weeks. The researchers then identified microorganisms from six marine sites around San Diego that are capable of breaking down and consuming the polyurethane material.

"No single discipline can address these universal environmental problems but we've developed an integrated solution that works on land -- and now we know also biodegrades in the ocean," said Mayfield. "I was surprised to see just how many organisms colonize on these foams in the ocean. It becomes something like a microbial reef."

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