The images of swaths of garbage floating on the oceans’ surface have become a rallying call to address plastic pollution, but there is more to this challenge than meets the eye. While plastics and microplastics – items smaller than 5 mm – accumulate and impact marine environments, much of the problem is rooted in land contamination. Land-based plastic pollution, which often feeds into the oceans, is estimated to be at least four times higher than what is in the oceans, according to a study published in Global Change Biology.
“Soil is the main source of microplastics reaching oceans through soil erosion and surface runoff,” Plastics settle in soil through disposal in landfills, as well as through the use of plastic-sheets in agriculture or application of microplastic contaminated compost. “Direct disposal of plastics to ocean is relatively less pronounced compared to the transfer of microplastics from land. Microplastics, lighter than soil particles, such as sand, silt and clay, are easily lost to waterways,”…
“We contribute to plastic pollution through indiscriminate disposal of plastics in landfills and use of microbeads in cosmetics and microfibers in textiles. There are efforts to produce biodegradable plastics, which may provide some solution to plastic pollution, but bioplastic may not be the silver bullet to manage plastic pollution.” Commonly used biodegradable bioplastics “retain their mechanical integrity under natural conditions, potentially causing physical harm if they are ingested by marine or terrestrial animals.” “The fate of biodegradable bioplastics in natural and engineered environments could be potentially problematic. Methane is a product of biodegradation in anaerobic environments in landfills.” These bioplastics, furthermore, require high temperatures, controlled aeration and humidity to degrade completely.
Due to their small size, microplastics, especially nanoplastics resulting from the degradation of microplastic, can enter organisms’ internal organs, where they could potentially transfer contaminants attached to them. These can include persistent organic pollutants, like polychlorinated biphenyls (PCBs), as well as trace metals like mercury and lead. The plastics and pollutants that accumulate on or in them enter the food chain and can eventually be transferred to humans, causing growing food safety concerns.
The Joint FAO/IAEA Centre’s laboratories are equipped to research the presence of microplastics in food. “Techniques such as energy dispersive X-ray spectroscopy and infrared and Raman spectroscopy can be applied to screen for plastics in foods, enabling risk assessment and management,” said Andrew Cannavan, Head of the Joint Centre’s Food and Environmental Protection Section.
Excerpt from Joanne Liou Out of Sight but not out of Mind: IAEA and FAO Launch R&D to Identify Sources, Impacts of Microplastic Pollution in Soil, IAEA Press Release, July 2, 2021