Reducing Plastic Pollution in the Oceans and Beyond


Feature Story | March 13, 2020

Revelle Lecture Explores the Problem and Proposes Solutions

By Sara Frueh

In 1996 Captain Charles Moore, a citizen scientist and founder of the Algalita Marine Research and Education Foundation, stumbled upon what came to be known as the Great Pacific Garbage Patch -- a vast area littered with plastic waste in the North Pacific Ocean – while sailing from Hawaii to California. 

The Garbage Patch – brought to wide public attention in a Los Angeles Times article written several years later -- captured the interest of Chelsea Rochman, now an assistant professor of ecology at the University of Toronto, and it helped shape her career, inspiring her to study the impact of plastic pollution on ecosystems.  Rochman told the story of plastic pollution, along with her own story, during the 21st Annual Roger Revelle Commemorative Lecture last week at the National Academy of Sciences.

While she was a graduate student, Rochman joined the first scientific expedition to investigate the Great Pacific Garbage Patch, run by students at Scripps Institution of Oceanography.  After traveling 1,000 miles west from San Diego, the students discovered that -- contrary to common descriptions -- the Garbage Patch was not an island of trash, but rather a large area dotted with plastic debris smaller than a pencil eraser.  The experience sparked many questions for Rochman, who realized that the plastics’ small size could potentially enable it to affect wildlife by infiltrating every level of the food chain.

“We now know that plastic accumulates not just in the Garbage Patch,” said Rochman.  “It accumulates in all major oceanic gyres where currents tend to come together.” Plastics, whether big or small, are found from the top to the bottom of the ocean and in ecosystems ranging from coral reefs to sea grass habitats to the Great Lakes.

Chelsea Rochman, assistant professor of ecology at the University of Toronto
Chelsea Rochman, assistant professor of ecology at the University of Toronto

The ubiquity of plastics means that they cross paths with a multitude of wildlife species.  “When you have widespread contamination, you also have widespread exposure,” said Rochman.  More than 800 species have been reported or documented to interact with plastic in the environment — for example, ingesting it or becoming entangled in it.

Rochman’s work focuses on microplastics, which are found not only in waters but also in terrestrial soils and the atmosphere.  They enter the environment through wastewater and stormwater, and they come from the breakdown of many different products, from cigarette butts to single-use plastic items.  Microplastics are also shed from clothing when it’s washed, and sloughed off car tires. 

Field studies show that larger plastics have impacts ranging from individual animals to populations and ecosystems.  For microplastics, studies have revealed mixed results, Rochman explained; many laboratory studies show evidence of an effect on wildlife, but there are just as many studies that showed no effect.  “This is the question that keeps me up at night: Why do some microplastics cause an impact and others do not?”

Rochman has studied the question further, finding that the dose makes the difference, with higher doses of microplastics having an impact.  Dosing animals with very tiny plastics — at the nanoscale — also tends to produce an effect.  And the shape matters, as well: Microfibers, such as the fibers shed from clothing during washing, are more likely to affect organisms than other microplastics at the same concentration.  One study that found that a high concentration of microfibers caused lake flies to transition more slowly from larvae to adult flies — a population-level effect that may change timing of the flies’ emergence in a system.

There’s much more we need to learn about microplastics, said Rochman.  She and her colleagues will soon use an experimental area in Ontario, Canada — a group of lakes zoned off for research on how substances impact ecosystems — to study how microplastics move through an ecosystem and affect the entire food web.

Pictured:  Maris Polanco, ETERNAL, 2019, approximately 1,200 plastic bags, 60 feet long, commissioned by the Science Gallery Detroit for their 2019 exhibition, Depth, on loan from the artist.
Pictured: Maris Polanco, ETERNAL, 2019, approximately 1,200 plastic bags, 60 feet long, commissioned by the Science Gallery Detroit for their 2019 exhibition, Depth, on loan from the artist.

Policies to Combat Plastic Pollution

Today we produce about 380 million metric tons or more of plastic per year, about 40 percent of which are single-use plastics that we throw away, said Rochman.  This is a valuable material, made out of oil, that doesn’t have a sustainable life cycle.  “If we really valued the plastic material along its entire life cycle, we would recycle more,” she said.

If we continue business as usual, one researcher has estimated that by 2060, we will double the amount of plastic waste produced that has the ability to leak into the environment, said Rochman.  We must do something about this, but there is no silver bullet, she said; many different solutions — cleanup, reduced use of plastics, improved waste and materials management — will be needed.

Rochman and her colleagues recently proposed that the world needs an international agreement for plastic pollution — perhaps following the example of the Paris Agreement on climate change, which sets a target level for lowering carbon emissions.  Right now, said Rochman, we are emitting 8 million metric tons of plastic to the ocean each year, and so perhaps our target should be to reduce it to 2 million metric tons.  With a numerical target established, countries could sign on to the agreement, and there could be a global fund that allows countries that lack resources to be able to take action.

Within each country, supportive policies are needed at every level of government, Rochman said.  Cities, for example, have imposed bans on single-use plastics and put in green stormwater infrastructure, and at the federal level a ban on microbeads might be enacted.  We need all stakeholders – industry, scientists, the public, media, and municipalities -- working together, she said, because government can’t do it alone.  

Watch a webcast of the lecture

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