Plastic winds up everywhere—from the top of Mount Everest to remote corners of Antarctica. Every year, millions of tons of discarded plastic also wash into the ocean. Some of it floats in giant garbage patches, whereas other bits drop to the sea floor, even turning up in the hindguts of crustaceans in deep ocean trenches.
Research about ocean plastic is swelling, too, from just 46 papers in 2011 to 853 in 2019, according to a U.N. report published today on the state of global science. This year’s edition of the report, which UNESCO publishes every 5 years, found that the growth in ocean plastic research outstripped that of the other 55 development-related topics it tracked (see chart, below). “It has really skyrocketed in recent years,” says Erik Van Sebille, an oceanographer and climate scientist at Utrecht University who uses plastic particles as tracers to study the ocean’s dynamics.
Carmen Morales, an ecotoxicologist at the University of Cádiz’s Marine Litter Lab, says plastic is more conspicuous than contaminants such as metals or organic compounds, and it draws more attention from the public and policymakers. “It’s an eyesore to have all this plastic on beaches,” adds Bart Koelmans, an aquatic ecologist at Wageningen University. “For many people, that is enough to be concerned.” Scientists are delving into where the plastic comes from, where it goes, and how it affects the environment and human health.
But gaps remain in the research. Journals “still get many papers dealing with exactly the same topics: the presence of plastic on beaches, on the seabed, or in animals, but not [many] about sources or solutions,” says Ángel Borja, a marine ecologist at the AZTI research centre in Pasaia, Spain.
In a study published today, Morales pinned down sources by combining data from scattered studies into an inventory of 12 million litter items larger than 2 centimeters. Her team found that takeout food and drink packaging was the most pervasive: Single-use bags, bottles, containers, and wrappers accounted for 44% of all waste across environments.
Researchers are also trying to understand the ecological effects of plastic pollution. Plastic itself is inert, but often contains toxic additives such as flame retardants, pigments, or chemicals to make plastic more flexible and durable. “These additives are what we’re worried about,” Morales says. Other harmful substances, such as polycyclic aromatic hydrocarbons, can enter ecosystems by sticking to drifting plastic.
Microplastic particles eroded from larger objects can end up the same size as plankton, so marine animals eat them without deriving any nutrition. Smaller, nanoplastic particles may be the most harmful: They can be tiny enough to penetrate tissues, where their shape may make a difference, Koelmans says: Fibrous particles seem to cause more inflammation than spherical ones. Yet the overall ecotoxicological effects of plastic are poorly understood; it’s difficult for labs to reproduce the cocktail of particles that organisms are exposed to in the environment.
To stem the buildup of debris, many countries have moved to phase out single-use plastics; as of 2018, 127 had passed legislation to regulate plastic bags, UNESCO says. But given low recycling rates, the report says, bans will not be enough: Biodegradable alternatives will be needed.
Research into such materials, derived from plant-based hydrocarbons, is also growing fast, if slower than studies describing the problem. Publications on eco alternatives to plastics almost tripled from 404 in 2011 to 1111 in 2019, the U.N. report found. “I’m happy [to see the figures] because it means I made the right decision to change my research focus,” says Carla La Fuente, a postdoc chemical engineer at the University of São Paulo, Piracicaba, who is developing green methods to make biodegradable plastic from cassava starch.
Oceanographer Tiffany Straza, the report’s deputy editor at UNESCO, sees parallels between plastic pollution and the problem of nuclear waste. “There was this idea that our scientific knowledge and solutions for waste disposal would catch up while we chased after this advanced technology,” she says. Yet practices for disposing of nuclear waste lagged while nuclear power burgeoned. “I’m not convinced that we’ve fully learned that lesson,” she says. “Are we going to do the same with plastics?”
sciencemag.org, 10 June 2021