Limited waste collection services in rural communities leading to high microplastics levels in Cambodia’s Mekong River

Reno, Nev. (Oct. 19, 2026) – Plastics are accumulating in ecosystems around the world, and their tiny fragments can collect and carry chemical pollutants and pathogens into plants, animals, and people. When fishermen in Cambodia’s Mekong River became alarmed about the amounts of plastic they were hauling up with each catch, they reached out to scientists for help. To investigate and measure the problem, DRI researchers joined a river expedition with Wonders of the Mekong— a project focused on applied research, capacity building, and outreach to solve conservation and development challenges along Southeast Asia’s longest river. Now, their results are available in a new study that demonstrates the role of waste collection services in rural communities along the river. The research can help inform improvements in waste management on a river that is critical to livelihoods in China, Myanmar, Thailand, Lao PDR, Cambodia, and Vietnam.  

The research, published Oct. 1st in the journal npj Emerging Contaminants, was led by Rachel Kozloski and her colleagues with DRI’s Microplastics and Environmental Chemistry Lab and the University of Nevada Reno. They sampled plastics and microplastics along the Cambodian stretch of the Mekong River during the wet and dry seasons in 2022. Their findings showed that where communities lacked waste collection services, microplastics concentrations immediately downstream were much higher. By modeling the observed relationship, they showed that improving waste collection services in rural riverside communities could result in a substantial reduction in downstream microplastic concentrations. The research is critical for improving water quality in a river that 66% of Cambodians rely on for subsistence fishing or employment.  

“Our research shows that there's a pretty strong link between what you do with your trash in those riparian areas and the microplastic concentration in the river just downstream of that,” Kozloski said. “Of course, our data is from 2022, and we know that the Cambodian government has been working to improve waste collection services in the years since. Our hope is that our data can highlight strategic locations where waste collection would make the biggest impact and help limited resources go further.”  

The research team also examined more than 3,000 plastic particles collected from the surface of the Mekong River and identified their chemical compositions. They found a notable shift in the types and sizes of plastics collected in the dry season compared to the wet season, when high monsoonal flows flush larger plastics from the river bottom and the surrounding landscape. A wide variety of polymers was identified during the dry season, with the single largest category identified as an assortment of uncommon plastics. During the wet season, the dominant plastics were polypropylene, polyterephthalates (PET), and polyethylene. Although the concentration of microplastics was about the same (between 3 and 4 microplastics per liter of water), the average daily load increased by an order of magnitude in the wet season because the higher flows mobilized more trash. 

The researchers sampled smaller microplastic particles than previous studies, and therefore identified higher concentrations than previously found in the Mekong River. The research is consistent with microplastics levels found in both China’s Yangtze and Yellow Rivers and India’s Godavari River.  

Data shows that only 19% of Cambodian municipalities had contracted waste collection services in 2018, with nearly all rural communities discarding their waste in open spaces, unregulated landfills, burn pits, or on streambanks. 

"I’d love to return to the Mekong River in future years to re-sample for plastics and compare it to what we found in 2022,” Kozloski said. “Having this data gives us a great baseline for understanding how expanding waste collection services is improving water quality in the region.”  

“The University of Nevada’s Wonders of the Mekong was delighted to support our U.S. and Cambodian colleagues in this first-of-its-kind effort along the Cambodian Mekong basin, which connects land waste to the plastics in the river,” said Sudeep Chandra, coauthor of the study and Director of the Tahoe Institute for Global Sustainability. “Having traveled along the river many times, I have seen thousands of people relying on the river for water and food through fish collections. Of course, no one really wants to drink or eat plastic that is polluting the river. I hope this study will help enlighten policy makers that an integrated approach in development which includes programs for waste management and reducing plastic use can protect rivers and the people who rely on them.” 

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More information: The full study, Solid waste management practices in riparian communities are a key driver of microplastic concentrations in the Mekong River, Cambodia is available from npj Emerging Contaminants at DOI: 10.1038/s44454-026-00062-0 

Study authors include: Rachel Kozloski (DRI), Monica M. Arienzo (DRI), Seila Chea (Wonders of the Mekong), Daniel Saftner (DRI), Kerri Minatre (DRI), Sudeep Chandra (Tahoe Institute for Global Sustainability, UNR), & Zeb Hogan (Tahoe Institute for Global Sustainability, UNR) 

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Elyse DeFranco 

Lead Science Writer & Public Information Officer 
elyse.defranco@dri.edu