What is the Science Behind Plastic Pollution?

Policy momentum is building, with an increasing number of studies investigating the efficacy of actions addressing not just waste management but also upstream production and consumption.

SEATTLE (Scrap Monster): Over the past year-plus, scientists have made significant strides in understanding the scope, impact and potential solutions to the global plastic pollution crisis, and we’ve gathered them here by theme. Let’s dive in!

Where it comes from and where it’s going

Increasingly, scientists recognize plastics as a planetary-scale pollutant, disrupting key Earth systems including biodiversity, terrestrial, freshwater and marine health. Researchers are now identifying specific areas where plastic accumulation—and therefore, risk—may be greatest. A long-term study published last year showed that more than 70% of macroplastics released into rivers remain near their source, often trapped by floating vegetation which can hold plastic concentrations nearly 200 times higher than surrounding waters. These accumulations have led to the formation of so-called “river garbage patches,” some with plastic levels exceeding those found in the North Pacific Gyre.

Meanwhile, modelling efforts have expanded to estimate plastic concentrations in ecosystems beyond the ocean surface, including in the atmosphere, below the ocean surface, in inland waterways and in marine animals. Estimates published last year suggest that 3 to 11 million metric tons of plastic now reside on the ocean floor—up to 100 times more than at the surface—threatening deep-sea ecosystems vital to climate regulation. Coastal convergence zones—coastal waters wherecurrents and wind cause water from different areas to meet—were also recently found to be microplastic hotspots. These hotspots included more than 1,800 marine protected areas identified as under significant stress from microplastic pollution.

Human health and micro/nanoplastics

Recent research has further informed estimates of human exposure to micro- and nano- plastics through both diet and inhalation. One study co-authored by Ocean Conservancy found microplastics in nearly 90% of protein products tested—including beef, chicken, pork and plant-based samples. From this, we estimated that the average adult in the United States could ingest up to 3.8 million plastic particles annually from proteins alone. Drinks, dairy products and other non-protein food sources also serve as ingestion pathways.

But we don’t just eat plastics. A new study estimated that globally, adults breathe in an average of 1,355 plastic particles daily, or roughly 500,000 particles a year. From 1990 to 2018, researchers estimate human dietary and airborne microplastic exposure increased more than sixfold in some parts of the world, underscoring growing global concern.

Plastic particles have now been found throughout the human body in arteries, stomach tissue, brains and reproductive systems, raising serious health concerns. One study published this year found that roughly 25% of the 16,325 chemicals associated with plastics are considered hazardous.” More worrisome is that the vast majority chemicals used in plastics remain unregulated and understudied. The health consequences are not only physiological but economic: In 2018 alone, plastic-related diseases cost the United States an estimated $249 billion, largely from exposure to plastic-associated chemicals as polybrominated diphenyl ethers (PBDEs).

What we can do about it

As our knowledge about the extent and impacts of plastic pollution grows, so does public concern. An Ocean Conservancy-led study published last year found that in the United States, plastic pollution is seen as the greatest threat to the ocean, and there is strong public support for policies to solve this problem by holding plastic producers accountable.

Experts agree that solving the plastic crisis requires a full lifecycle approach and multinational collaboration, with one study showing that implementing four global interventions—a 40% recycled content mandate; a 2020 virgin production cap; a $50 billion investment in waste management infrastructure; and a plastic packaging tax—could reduce mismanaged plastic waste by 91% and plastic-related GHG emissions by one-third by 2050.

Policy momentum is building, with an increasing number of studies investigating the efficacy of actions addressing not just waste management but also upstream production and consumption. One 2025 study looking at data from Ocean Conservancy’s International Coastal Cleanup found that plastic bag bans and fees meaningfully reduce the relative amount of bags in beach litter by 25% to 47% in the United States, while a 2024 study estimated that a U.S. national deposit return scheme could significantly boost recycling rates for PET bottles from 24% to 82%. To support better decision-making and community action, science-backed tools such as the Circularity Assessment Protocol (CAP) have been developed to map waste flows and identify points for intervention.

Courtesy: www.oceanconservancy.org

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