Researchers say that more microplastics pollution is getting into farm soil than oceans—and these tiny bits are showing up in our fruits, veggies, and bodies.
Mary Beth Kirkham hadn’t studied microplastics when she was invited to co-edit a new book about microplastics in the environment—but something stood out to her about the existing research.
“I had read in the literature that…cadmium and other toxic trace elements [are] increased when we have these particulate plastics in the soil. So, that was of concern to me,” Kirkham, a plant physiologist and distinguished professor of agronomy at Kansas State University, told EHN.
Kirkham’s expertise is in water and plant relations and heavy metal uptake, so she decided to conduct her own research in which she cultivated wheat plants exposed to microplastics, cadmium, and both microplastics and cadmium. Then she compared these plants to those grown without either additive. She chose cadmium because it’s poisonous, carcinogenic, and ubiquitous in the environment due to human activity—it’s shed from batteries and car tires, and is naturally found in the phosphate rock used to make agricultural fertilizers.
“Cadmium is everywhere,” said Kirkham.
At the end of the experiment she sent her wheat plants off for analysis, and, validating previous reports, the plants grown with microplastics were more cadmium-contaminated. “The plastics really were acting as the vector for uptake of the cadmium,” she said.
Her experiment became a chapter in the new book, Particulate Plastics in Terrestrial and Aquatic Environments.
“I think people just haven’t felt that microplastic uptake by plants is an issue,” said Kirkham. “It just hasn’t been in the public eye.”
Microplastics, loosely defined as plastic pieces smaller than 5 millimeters across, or roughly the size of a small grain of rice, have made their mark on both the global ecosystem and the popular consciousness, famously killing seabirds and raining down on wilderness areas. And while the impacts of ocean microplastics have been the subject of significant media and scientific attention, researchers say that most microplastics are actually accumulating on land, including agricultural areas. One estimate suggested that 107,000 to 730,000 tons of microplastics could be dumped onto agricultural soils in the U.S. and Europe every year, compared to the 93,000 to 236,000 tons that enter the oceans.
Microplastics arrive on farms through processed sewage sludge used for fertilizer, plastic mulches, and are even intentionally added as slow-release fertilizers and protective seed coatings. In just the last few years, an uptick in research has uncovered alarming potential impacts of this contamination on all aspects of agricultural systems from soil quality to human health.EHN