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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Tiny plastic particles are found everywhere

It's not the first study on microplastics in Antarctica that researchers from the University of Basel and the Alfred-Wegener Institute (AWI) have conducted. But analysis of the data from an expedition in spring 2021 shows that environmental pollution from these tiny plastic particles is a bigger problem in the remote Weddell Sea than was previously known.

The total of 17 seawater samples all indicated higher concentrations of microplastics than in previous studies. "The reason for this is the type of sampling we conducted," says Clara Leistenschneider, doctoral candidate in the Department of Environmental Sciences at the University of Basel and lead author of the study.

The current study focused on particles measuring between 11 and 500 micrometers in size. The researchers collected them by pumping water into tanks, filtering it, and then analyzing it using infrared spectroscopy. Previous studies in the region had mostly collected microplastic particles out of the ocean using fine nets with a mesh size of around 300 micrometers. Smaller particles would simply pass through these plankton nets.

The results of the new study indicate that 98.3 percent of the plastic particles present in the water were smaller than 300 micrometers, meaning that they were not collected in previous samples. "Pollution in the Antarctic Ocean goes far beyond what was reported in past studies," Leistenschneider notes. The study appears in the journal Science of the Total Environment.

What role do ocean currents play?

The individual samples were polluted to different extents. The offshore samples, which were collected north of the continental slope and the Antarctic Slope Current, contained the highest concentrations of microplastics. The reasons for this are not conclusively known. It may be that the ice that tends to form near the coast retains the tiny plastic particles, and they are only released back into the water when the ice melts. It could also be the case that ocean currents play a role. "They might work like a barrier, reducing water exchange between the north and south," suggests Gunnar Gerdts from the AWI in Heligoland, Germany.

What is certainly true is that ocean currents are an important factor and the subject of many open questions in the field. So far the researchers have only examined water samples from the ocean surface, but not from lower depths. This is primarily due to limited time on the ship expeditions for taking samples and to equipment with insufficient pumping capacity. "It would nonetheless be revealing to analyze such data, since the deep currents differ greatly from the surface currents and thermohaline circulation leads to exchange with water masses from northern regions," Leistenschneider says.

It is also still unclear how the microplastics make their way to the Weddell Sea in the first place and whether they ever leave the region. The strong Antarctic Circumpolar Current, which flows all the way around the Antarctic Ocean at a latitude of about 60° south, might prevent their departure. The researchers are also not yet able to say conclusively where the microplastics originate. Possible sources include regional ship traffic from the tourism, fishing and research industries, as well as research stations on land. However, the microplastics might also make their way to Antarctica from other regions via ocean currents or atmospheric transport.

Research leads to awareness

Clara Leistenschneider plans to focus next on analyzing the sediment samples she collected during the same expedition. This should provide information about how microplastics are accumulating on the sea floor, which is home to unique and sensitive organisms and is a breeding ground for Antarctic icefish (Bovichtidae).

With the increase in tourism in the Antarctic Ocean, pollution may increase even more in the future, further impacting the environment and the food chain.

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Scientists uncover evidence that microplastics are contaminating archaeological remains

Researchers have for the first time discovered evidence of microplastic contamination in archaeological soil samples.

The team discovered tiny microplastic particles in deposits located more than seven metres deep, in samples dating back to the first or early second century and excavated in the late 1980s.

Preserving archaeology in situ has been the preferred approach to managing historical sites for a generation.

However, the research team say the findings could prompt a rethink, with the tiny particles potentially compromising the preserved remains.

Microplastics are small plastic particles, ranging from 1μm (one thousandth of a millimetre) to 5mm.

They come from a wide range of sources, from larger plastic pieces that have broken apart, or resin pellets used in plastic manufacturing which were frequently used in beauty products up until around 2020.

The study, published in the journal Science of the Total Environment, was carried out by the universities of York and Hull and supported by the educational charity York Archaeology.

Professor John Schofield from the University of York's Department of Archaeology, said: "This feels like an important moment, confirming what we should have expected: that what were previously thought to be pristine archaeological deposits, ripe for investigation, are in fact contaminated with plastics, and that this includes deposits sampled and stored in the late 1980s.

"We are familiar with plastics in the oceans and in rivers. But here we see our historic heritage incorporating toxic elements. To what extent this contamination compromises the evidential value of these deposits, and their national importance is what we'll try to find out next."

David Jennings, chief executive of York Archaeology, added: "We think of microplastics as a very modern phenomenon, as we have only really been hearing about them for the last 20 years, when Professor Richard Thompson revealed in 2004 that they have been prevalent in our seas since the 1960s with the post-war boom in plastic production,"

"This new study shows that the particles have infiltrated archaeological deposits, and like the oceans, this is likely to have been happening for a similar period, with particles found in soil samples taken and archived in 1988 at Wellington Row in York."

The study identified 16 different microplastic polymer types across both contemporary and archived samples.

"Where this becomes a concern for archaeology is how microplastics may compromise the scientific value of archaeological deposits. Our best-preserved remains -- for example, the Viking finds at Coppergate -- were in a consistent anaerobic waterlogged environment for over 1000 years, which preserved organic materials incredibly well. The presence of microplastics can and will change the chemistry of the soil, potentially introducing elements which will cause the organic remains to decay. If that is the case, preserving archaeology in situ may no longer be appropriate," added David Jennings.

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