There’s Even Plastic in Clouds
A universal poison, universally present, about which we are doing nothing.
There’s Even Plastic in Clouds
Five new places scientists have uncovered plastics.
By Katherine Gammon
January 12, 2024
On the top of Mount Everest, in the Mariana Trench, in the human placenta, and babies’ feces: Plastics are everywhere. They are built to last, and last they do: A plastic bag can endure for 20 years in the environment, and a disposable diaper, soiled or not, up to 200. When they do finally break down into microplastics—smaller than 1 micrometer, or about 1/70th the diameter of a human hair—they can become difficult to detect. These microplastics are so ubiquitous in the environment that some scientists think we should track how they cycle through the global oceans, atmosphere, and soil much in the same way we track carbon and phosphorus.
Through soil, wind, and water, they even get into our food: Scientists have found microplastics in beer, honey, salt and most of the proteins we consume—everything from seafood to sirloin steak and even plant-based meat alternatives. We keep looking for plastics, and we keep finding them in new and surprising places. Below, five recent discoveries that expand our knowledge of our plastic footprint.
A liter of bottled water contains around 240,000 detectable plastic fragments.
Clouds: Researchers recently collected 28 samples of liquid from clouds at the top of Mount Tai in eastern China. They found microplastic fibers—from clothing, packaging, or tires—in their samples. Lower altitude clouds contained more particles. The older plastic particles, some of which attract elements like lead, oxygen, and mercury, could lead to more cloud development, according to a paper published in the journal Environmental Science & Technology Letters.
Rocks: Have you heard of plastistones? That’s the name scientists have given to a new type of sedimentary rock formed when molten plastic from burning trash cools down and fuses with minerals from the environment. These plastitones have now been found in 11 countries on five continents. They can wreak havoc on microbial communities, especially in the ocean, where the rocks may be mistaken for algae. They could also reshape the geological record of our planet.
Sedimentary rocks are the dominant rock type found on the Earth's surface, and they are highly susceptible to influence by human activities. In recent years, a number of plastic-rock complexes have been reported across the globe, such as plastiglomerate, plastitar, plasticrust, and anthropoquinas. Despite these findings, a holistic comprehension regarding the diagenesis and ultimate fate of these innovative plastic forms within the framework of sedimentary geology is lacking. Here we contend that these novel plastic forms meet the criteria of a sedimentary rock. Consequently, they merit recognition as a distinctive type of sedimentary rock. In this context, we propose the adoption of an existing term “plastistone” with a revised definition to collectively describe these novel plastic forms. This term aligns with the nomenclature convention for other sedimentary rocks, such as limestone, dolostone, sandstone, and mudstone. Plastistone is formed when plastic and clast from pre-existing rock are lithified together. Plastistones have been found on a global scale, both in coastal and inland regions. The polymer types most frequently found in plastic debris trapped in plastistones is polyethylene (PE), polyethylene terephthalate (PET), and polypropylene (PP), and their origins are mainly from domestic waste, such as packaging and containers, or as a result of maritime activities. Plastistones can form through a variety of means, including campfire or plastic waste burning, wave action, evaporation, or chemical bonding. Plastistones have been shown to alter the microbial communities of the surrounding environment and can generate significant amounts of microplastics and nanoplastics. This new type of sedimentary rock provides compelling evidence of how human activities can act as a powerful exogenic geological process that reshapes the geological record of our planet.
Bottled water: Scientists recently found that on average, a liter of bottled water contains around 240,000 detectable plastic fragments—10 to 100 times greater than previous estimates. Their research, published in the journal PNAS, focused on the tiniest plastic particles—nanoplastics. These particles can cross into the brain, gut, heart, and through the placenta to babies in utero.
Farm fertilizers: We’re making progress on the circular waste economy by using treated sewage sludge as fertilizer. But that sludge has now been found to be packed with microplastics. A study in the journal Environmental Pollution estimates that the “practice of spreading sludge on agricultural land could potentially make them one of the largest global reservoirs of microplastic pollution.”
Glaciers: You might think of the glaciers of Antarctica as some of the last wild and pristine places on Earth. But scientists recently found plastics there for the first time in the remote Collins glacier on King George Island—probably brought in by gusty winds. Plastics in glaciers and sea ice could increase the rate at which they melt, because plastic absorbs more heat than ice does. “Our results also show that plastic pollution, even if only in small quantities, reaches remote areas with few human settlements,” they write.
Airborne microplastics (MPs) have the potential to travel a long distance and undergo several cloud processes through atmospheric transport. However, little is known about the interactions between MPs and clouds. Here, we present field evidence for the presence of abundant and various MPs in cloudwater samples collected at Mt. Tai (1545 m asl.) in eastern China, with an average concentration of 463 MP L–1 in cloudwater, i.e., 0.21 MP m–3 in air. The cloud MPs had a broad size range of 8–1542 μm with 60% being smaller than 100 μm and dominant shapes of fragments with diverse polymers and darker colors. The concentrations of MPs were influenced by cloud liquid water content, source regions, and trajectory height, while the shapes and sizes appeared to be associated with long-range transport or localized sources. The roughened surface of cloud MPs indicated photochemical aging, which likely increased their adsorption capability for toxic metals (e.g., Pb, Hg) as confirmed by laboratory photoaging and adsorption simulations in ambient air, ultrapure water, and cloudwater. More research is needed to understand microplastic–cloud interactions and the potential impacts on atmospheric metal cycles and cloud formation.
Microplastics in Auckland's air revealed
Microplastic pollution swirling in Auckland's air is equivalent to millions of plastic bottles per year.
12 December 2022
Faculty of Science, Science and technology, Sustainable impact, Environment
Researchers from the University of Auckland calculated that 74 metric tons of microplastics are dropping out of the atmosphere onto the city annually, the equivalent of more than 3 million plastic bottles falling from the sky.
The study, published in Environmental Science & Technology, indicated that large numbers of microplastics in Auckland’s air are of extremely small sizes, raising concerns about the potential for particles to be inhaled and accumulate in the human body. Researchers around the world are likely to have dramatically undercounted airborne microplastics, says lead author Dr Joel Rindelaub, of the School of Chemical Sciences at Waipapa Taumata Rau, University of Auckland.
The levels found in Auckland’s air were many times higher than recorded in London, Hamburg and Paris in recent years because scientists in the new study used sophisticated chemical methods to find and analyse particles as small as 0.01 of a millimetre. The mean (average) number of airborne microplastics detected in a square metre in a day was 4,885. That compares with 771 in London (reported in a study published in 2020), 275 in Hamburg (2019) and 110 in Paris (2016).
“Future work needs to quantify exactly how much plastic we are breathing in,” says Dr Rindelaub. “It’s becoming more and more clear that this is an important route of exposure.” The study is the first to calculate the total mass of microplastics in a city’s air. Waves breaking in the Hauraki Gulf may play a key role in Auckland’s problem by transmitting water-borne microplastics into the air.
That effect seemed to be at work when Rindelaub and his colleagues, including PhD student Wenxia Fan and Professor Jennifer Salmond, recorded increased numbers after winds from the gulf picked up speed, likely leading to bigger waves and more transmission. “The production of airborne microplastics from breaking waves could be a key part of the global transport of microplastics,” says Rindelaub. “And it could help explain how some microplastics get into the atmosphere and are carried to remote places, like here in New Zealand.” Particle sizes changed with wind direction. When winds passed over the Auckland city centre, the microplastics downwind were larger, indicating the plastics had gone through less environmental aging and came from a closer source.
Microplastics enter the environment from sources including synthetic clothes and car tyres, breaking down into ever smaller particles. Polyethylene (PE) was the major substance detected, followed by polycarbonate (PC) and polyethylene terephthalate (PET). Polyethylene and PET are packaging materials while PC is used in electrical and electronic applications. All three are also used in the construction industry.
In the research, microplastics falling from the air were captured by a funnel and jar in a wooden box on a rooftop at the central city University campus. The same set-up was in a residential garden in Remuera. Almost all of the microplastics were too small to be seen by the naked eye. Scientists identified the smallest particles by applying a coloured dye that emitted light under certain conditions. A heat treatment was used to analyse mass.
“The smaller the size ranges we looked at, the more microplastics we saw,” Rindelaub says. “This is notable because the smallest sizes are the most toxicologically relevant.” Nanoplastics, the smallest particles, can potentially enter cells, cross the blood-brain barrier, and may build up in organs such as the testicles, liver and brain.
“Microplastics have also been detected in human lungs and in the lung tissue of cancer patients, indicating that the inhalation of atmospheric microplastics is an exposure risk to humans,” the paper says. Plastics have also been detected in the placenta. The paper, co-authored by Professor Kim Dirks, Dr Patricia Cabedo Sanz and Associate Professor Gordon Miskelly, called for standardisation of reporting metrics so studies of airborne microplastics could be better compared.
The paper’s introduction says: “Over the last 70 years, 8.3 billion metric tons of plastic have been produced globally. Only nine percent have been recycled, with the rest either incinerated or released into the environment.” Fibres dispersed by washing synthetic clothes, fragments shed by car tyres and washed by rain into the ocean, and bottles floating down rivers are just some of the ways plastic is added to the environment. Weathering and aging breaks plastic down into ever smaller particles.
The experiment was carried out over nine weeks during September, October and November in 2020.
Toxicity of Microplastics and Nanoplastics in Mammalian Systems
Cheryl Qian Ying Yong, et.al., 26 February, 2020
Abstract:
Fragmented or otherwise miniaturized plastic materials in the form of micro- or nanoplastics have been of nagging environmental concern. Perturbation of organismal physiology and behavior by micro- and nanoplastics have been widely documented for marine invertebrates. Some of these effects are also manifested by larger marine vertebrates such as fishes. More recently, possible effects of micro- and nanoplastics on mammalian gut microbiota as well as host cellular and metabolic toxicity have been reported in mouse models. Human exposure to micro- and nanoplastics occurs largely through ingestion, as these are found in food or derived from food packaging, but also in a less well-defined manner though inhalation. The pathophysiological consequences of acute and chronic micro- and nanoplastics exposure in the mammalian system, particularly humans, are yet unclear. In this review, we focus on the recent findings related to the potential toxicity and detrimental effects of micro- and nanoplastics as demonstrated in mouse models as well as human cell lines. The prevailing data suggest that micro- and nanoplastics accumulation in mammalian and human tissues would likely have negative, yet unclear long-term consequences. There is a need for cellular and systemic toxicity due to micro- and nanoplastics to be better illuminated, and the underlying mechanisms defined by further work.
BigMouth note: The paper available at the link above contains extensive lists of the harmful effects of plastics in mamalian systems as of 2020.