THE Philippines’ Pasig River ranks 8th as the worst source of plastic pollution in the oceans of the world, especially during monsoon season.
This was the conclusion of a study by Dutch and American researchers that was published by the research journal Nature Communications.
According to the said research, Pasig River annually dumps an average of 63,700 tons of plastic into the ocean. However, if the size of Pasig relative to the size of its drainage area is to be considered, it would make Pasig River the second worst contributor of plastic waste to the world’s oceans next only to China’s Yangtze River.
The Nature Communications report further said plastic trash in the ocean is a worldwide issue. It affects not just the marine environment itself but also the people who depend on the oceans for food and livelihood.
Animals such as fish, birds, and sea turtles are known to mistake plastic for food and to eat them, resulting in starvation and death. The animals that survive long enough to get eaten themselves, then their predators—including humans—are in danger of likewise ingesting the chemicals from the plastic.
Plastics reach the ocean through a number of ways, whether directly via aquaculture, shipping, and fishing activities, or indirectly via beach littering, discharged by rivers, or blown by the wind. However, land-based sources are considered to be the main contributors of plastics to the oceans.
The Dutch and American researchers looked at the plastic load inputs from 40,760 watersheds around the world and used geospatial data on population density, Mismanaged Plastic Waste (MPW) production per inhabitant and per day in 182 countries, monthly catchment runoff, and the presence of artificial barriers such as dams in their global model.
Plastic waste was considered “mismanaged” if it was littered or improperly disposed. Catchment area” refers to the area of land where water collects and flows into a river, stream, or other body of water.
The model results show that 1.15 to 2.41 million tons of plastic currently into the world’s oceans every year, with 67% of it coming from only 20 river systems. These rivers cover only 2.2% of continental surface area, but house 21% of the global population. Most of these top contributing rivers are in Asia.
Overall, Asian rivers were estimated to contribute 86% of the global plastic input to oceans. This is due to the perfect storm of high population density, large Mismanaged Plastic Waste production rates, and heavy rainfall during the monsoon season.
In terms of total contribution, the Yangtze River in China is the largest contributing catchment with 310,000 to 480,000 tons of plastic per year, followed by the Ganges River catchment at 105,000 to 172,000 tons per year.
The Pasig River is the eighth-largest contributor, with 32,100 to 63,700 tons of plastic per year. However, the Yangtze and Ganges River have the 2nd and 3rd largest catchment surface areas, respectively, with the Amazon being the largest.
The researchers cautioned that these input estimates are actually conservative, as the published studies they calibrated their model against only considered plastics on the surface that are 0.3 mm to 0.5 meters in size. Plastics smaller or larger than this size range, or found suspended in the water column, were not included due to limitations of the sampling equipment used.
The study is the first global assessment of how much inland populations contribute to ocean plastic through river systems.
Meanwhile, the EcoWaste Coalition, citing the paper “Plastic Debris Is a Human Health Issue” by Dutch researchers A. Dick Vethaak and Heather A. Leslie, said “the global threat of highly persistent plastic waste accumulating and fragmenting in the world’s oceans, inland waters and terrestrial environments is becoming increasingly evident.”
“Humans are being exposed to both plastic particles and chemical additives being released from the plastic debris of consumer society. This material is fragmenting, leaching and spreading throughout the biosphere, including indoor and outdoor air, soil, and water systems,” the two researchers said.
In another report, “Contaminants in Marine Plastic Pollution: The New Toxic Time-Bomb” by Dr Mariann Lloyd-Smith and Joanna Immig, it is said that “marine plastic is not only entangling and drowning wildlife, it is being mistaken for food and ingested along with its toxic contaminants.”
“Marine plastics and in particular microplastics, provide a global transport medium for the most toxic chemicals into the marine food chain and ultimately, to humans,” the Australian environmental advocates said.