by A team of UCLA researchers has put a new spin on the 1970s classic “Dust in the Wind” – only this one is brighter and brighter than the original Kansas hit.
They found that the wind collects microplastics from human sewage fertilizers at higher concentrations than previously known, and that it could be an “unpredictable” source of airborne plastic bits, flakes and threads .
“If you blow wind on soil with microplastics, you would expect the dust to contain the same amount of soil and microplastics,” said Sanjay Mohanty, a UCLA professor of civil and environmental engineering. “But here we found less soil in the dust and much more microplastics. That means every time the wind blows, the particles leave the soil as an option.”
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That’s a problem, he said, because it means people could inhale these particles, which measure between 1 and 5,000 micrometers, or 5 millimeters, in size. Most of these particles are likely to be coated with harmful chemicals such as plastic additives, heavy metals, pesticides and other chemicals that have been poured down the drain or into storm drains from the streets.
These “passenger” chemicals are the biggest health concern, Mohanty said, citing a growing body of research on known and potential harms.
“The more plastics we put out there, the more they end up in soil, water and food and people’s bodies,” said Avi Kar, senior attorney and director of Health and Food for the Natural Resources Defense Council. . & Community Program. “And they will bring with them the many harmful chemicals used to make plastic.”
In many large cities around the world, including Los Angeles, municipal sewage systems process human waste by separating wastewater from biosolids. The wastewater is filtered and often injected into the soil, where it is filtered to be used for irrigation and in some cases, drinking water. The biosolids – the residue left behind – can be dried, repackaged and sold as fertiliser.
Worldwide, annual production of biosolids is estimated to be 100 million tons, according to Mohanty and his colleagues. That is projected to increase to 175 million tons per year by 2050. According to estimates from the US Environmental Protection Agency, more than 2 million dry metric tons of biosolids are applied to land each year in the United States.
In 2011, 51% of the nation’s biosolids were applied to agricultural land and fields; 22% was disposed of in landfill; incineration 16%; and 11% were subject to other management practices.
Sludge-based fertilizers are attractive for environmental and economic reasons. They provide farmers and gardeners with a natural and sustainable way to reintroduce nutrients into the soil and extend the life of municipal landfills.
Los Angeles County Sanitation Districts, for example, treat sewage from 5.6 million people. In 2022, they produced approximately 110,000 tons of compost, 20,000 of which were processed at the Tulare Lake Compost site, southeast of Kettleman City.
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In 2021, Mohanty and his colleagues discovered that sludge-based fertilizers contained far more plastic particles than previously suspected.
Later, however, the team tried to find out what happened to the particles in the compost. To do this, they spread fertilizer on fields in Lind, Wash., about 75 miles southwest of Spokane. Then they put portable wind tunnels over the plots, and turned on the fans. They found that microplastics were about 2.5 times more likely to be airborne than other soil particles.
The reason for this, said Mohanty, is that microplastics are not “sticky” like the other elements. He said California farmers and gardeners often use water on their fields and lawns in the summer months not only to irrigate crops but to reduce dust. Because plastic does not absorb water, it does not adhere like the minerals and organic matter in the soil.
“The findings are not surprising given the ubiquitous nature of plastics in agriculture and the low density and weight of microplastics,” said Mark Gold, director of the Natural Resources Defense Council’s Water Scarcity Solutions Program, who was not involved in the research. .
Shelly Walther, an environmental scientist with the Los Angeles County Sanitation District, said she was a little wary of how the researchers went about identifying and counting microplastics in their samples.
She said that although microplastics research is increasing, the scientific community is concerned about the methods and technologies used, as well as the reliability and reproducibility of some of the research.
But, she said, biosolids clearly contain microplastics, and she’s not surprised that some of them could end up in the air. However, she questioned whether all the plastics can be blown away, saying that some are denser and less likely to blow away in the wind.
However, she said, plastic is an ever-increasing problem for the waste stream.
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Local Authority sanitary districts have supported laws that would help reduce the amount of plastic entering our waste at source, including those that would require filters in washing machines and dryers.
Mohanty said one of the biggest sources of microplastics in wastewater is washing machines.
“Every time we wash our clothes, we’re producing millions and millions of fibers” that drain directly into our wastewater, he said.
Bryan Langpap, the sanitation district’s spokesman, said “Hallelujah” when asked about laws designed to cut plastic – and other contaminants – at their source.
“We have to stop producing so much of this stuff. Because it’s in our consumer products, and it’s in our homes, you can’t stop it from getting into the air and moving around,” he said. , noting research that has found plastic particles in the Arctic, in the deepest trenches in the ocean, and in almost every single place scientists have looked.
He said the problem may be even bigger than we know, citing recent research that found hundreds of thousands of nanoplastic particles in single-use water bottles – an issue Mohanty also considered in relation to plastic in fertilizer .
He said that unlike microplastics, his models show that nanoplastics – which range in size from 1 nanometer to 1 micrometer – are more likely to stick to the soil, due to a greater attractive force on the surfaces. And while that may keep them from blowing into the air and into our lungs, chances are they’re also picking up crops and plants.
This story originally appeared in the Los Angeles Times.
