Macroplastic survey of Tullahan River in Metro Manila Philippines

The Tullahan River in Metro Manila was once listed among the top five most plastic-emitting rivers in the world, based on model estimates. Yet until recently, very little field data existed to confirm what was actually floating through or sitting along its banks. A 2024 study published in Frontiers in Environmental Science set out to close that gap by physically counting and categorising the macroplastic litter moving through a 5.17-kilometre stretch of the river in Quezon City and Valenzuela City. The results confirm that the river is indeed carrying a heavy plastic load — and they also reveal which specific types of plastic are responsible, and why current waste management practices are failing to stop them at the source.

To put those numbers in context: the study found that wrappers and thin polyethylene (PE) plastics — the kind used for sachets, snack bags, and grocery bags — were the top contributors to macroplastic pollution in the river. These items are lightweight, easily carried by wind and water, and rarely collected by informal waste pickers because they have little to no scrap value. The implications for anyone living near the Tullahan or similar urban waterways are direct: the plastic that leaves your household bin or neighbourhood street often ends up in the river, and from there, it travels to Manila Bay and the open ocean. This is not a distant environmental problem — it is a local one with measurable consequences for public health and ecosystem integrity.

What the Tullahan River survey actually measured

The researchers selected five sampling stations along a 5.17 km stretch of the Tullahan River. Three stations were used for floating litter observation — North Wind Avenue Bridge, San Bartolome Delta Bridge, and Maceda Bridge — while riverbank litter was manually collected at Gozum Street Bridge and San Bartolome Delta Bridge. The team measured flow velocity using a simple float method (timing a floating object between two fixed points) and counted visible macroplastics — items larger than 5 mm — passing beneath the bridges. On the riverbanks, they picked up and sorted every piece of litter they found, categorising it by product type (e.g., wrappers, bottles, bags) and polymer type (e.g., polyethylene, polypropylene).

One finding stood out immediately: the macroplastic flux was lowest at the site where residential houses were farthest from the stream. That may seem obvious, but it points to a critical mechanism. Where homes are built close to the riverbank, waste — whether from improper disposal, overflow from collection points, or littering — has a shorter path into the water. The study’s semi-structured interviews with local government units also suggested that weak enforcement of existing solid waste management (SWM) policies, combined with certain land-use activities, directly contributes to the amount of plastic entering the river. This is consistent with broader patterns observed across Metro Manila, where industrial and residential runoff both play a role in waterway pollution.

Why wrappers and thin plastics are so hard to manage

The study’s waste characterisation data is revealing. Riverbank litter was primarily plastic, with 30 to 41 percent classified as residuals — items that have no recycling value and are typically sent to landfill or incinerated — and only 5 to 21 percent classified as recyclables. The dominant polymer was low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE), the materials used for most flexible packaging. These plastics are lightweight, degrade into smaller fragments relatively quickly under sunlight, and are difficult to collect because they blow away easily and clog sorting equipment.

There is also a behavioural dimension. The Philippines has a deeply entrenched sachet economy, where low-income households buy single-use portions of shampoo, detergent, coffee, and cooking oil because they cannot afford the larger, more cost-effective containers. Each sachet is a tiny piece of multi-layered plastic that is nearly impossible to recycle. The study found that these wrappers were the single most common item in both floating and riverbank samples. This is not a problem that can be solved by better recycling alone — it requires upstream changes in packaging design, product pricing, and consumer access to affordable bulk goods.

What gets missed in the plastic pollution conversation

Most public discussion about plastic pollution focuses on the volume of waste. But the Tullahan survey highlights several nuances that complicate the picture.

The gap between model estimates and field data

The Tullahan River was ranked among the top five most plastic-emitting rivers globally by a widely cited 2017 model. But that model relied on assumptions about waste generation, population density, and hydrology — not actual measurements. The 2024 study is one of the first to provide ground-truth data for the Tullahan, and its findings suggest that while the river is indeed heavily polluted, the exact flux rates may differ from earlier estimates. This matters because policy decisions — such as where to deploy cleanup operations or invest in waste infrastructure — are often based on those models. Without more field studies, resources may be misallocated.

Land use as a driver, not just a background factor

The study explicitly investigated how land use affects plastic accumulation. Stations near densely built residential areas with narrow river buffers had higher plastic loads than stations where houses were set farther back. This is not simply a matter of population density — it is about the physical proximity of waste sources to the water. In many Metro Manila barangays, houses are built right up to the river’s edge, and there is no designated waste collection point between the home and the stream. The implication is that zoning regulations and building setbacks could be as important as waste collection frequency in reducing riverine plastic pollution.

The role of enforcement — or its absence

Semi-structured interviews with local government officials revealed that existing SWM policies, such as the Ecological Solid Waste Management Act (RA 9003), are often weakly enforced. Barangay-level ordinances against littering and illegal dumping exist on paper but are rarely acted upon. The study does not name specific failures, but the pattern is consistent with what other researchers have documented across the Philippines: laws exist, but the institutional capacity to monitor, fine, and penalise violations is limited. This is not a technical problem — it is an administrative and political one.

Microplastics as a downstream consequence

While the study focused on macroplastics, it notes that the mean abundance of microplastics in the Tullahan’s surface waters was previously measured at 11,475 particles per cubic metre, and 848 particles per kilogram of dry sediment. Those microplastics do not appear out of nowhere — they are the result of macroplastics breaking down over time. Every wrapper and thin bag that enters the river is a future source of microplastic pollution, which is far harder to remove and poses direct risks to aquatic life and, through the food chain, to humans. The macroplastic problem today is tomorrow’s microplastic crisis.

What can be done — and who needs to act

The study does not prescribe a single solution, but its findings point to several practical actions that different stakeholders can take. These are not hypothetical — they are grounded in what the data shows about the types of plastic entering the river and the conditions that allow it to happen.

Strengthen barangay-level waste collection for residuals

Since 30 to 41 percent of riverbank litter is residual waste with no recycling value, the current system’s emphasis on recyclables misses a large portion of the problem. Barangays need dedicated collection streams for residuals — not just recyclables — and these collections must happen frequently enough that waste does not accumulate near waterways. Residents should know exactly when and where residual waste is collected, and the collection points should be located away from riverbanks and drainage channels.

Target flexible plastics at the production stage

Wrappers and thin PE plastics are the top contributors. No amount of downstream cleanup will keep up with the volume entering the river if production continues at current levels. The Extended Producer Responsibility (EPR) Act of 2022, which requires large companies to recover a percentage of their plastic packaging, is a step in this direction. But compliance is still low, and the law currently covers only large enterprises. Smaller manufacturers and importers of sachet products remain largely unregulated. Consumers can support brands that use mono-material packaging (easier to recycle) or offer refill options, but the real leverage is at the policy and corporate level.

Enforce building setbacks and river buffer zones

The study found that macroplastic flux was lowest where residential houses were farthest from the stream. Local government units can enforce existing easement laws — the Water Code of the Philippines mandates a 3-metre easement along rivers — and prevent new construction within that zone. In areas where houses already exist close to the river, installing physical barriers such as mesh screens or vegetative buffers could reduce direct waste entry. These are low-cost interventions that do not require new legislation, only consistent enforcement.

Invest in regular riverbank cleanups with waste sorting

The manual collection method used in the study is labour-intensive but effective. Organised community cleanups that include waste characterisation — sorting collected litter by type and recording the data — can serve both as a cleanup and as a monitoring tool. The data generated can help barangays identify which products are most problematic and target their interventions accordingly. Several environmental NGOs already run such programs; scaling them up with local government support would provide both immediate removal of litter and long-term data for policy.

Frequently asked questions about the Tullahan River plastic survey

Closing thoughts

The Tullahan River survey confirms what many residents of Metro Manila already suspect: the plastic waste that leaves homes and businesses does not disappear — it travels. The data is specific enough to guide action, from enforcing river buffer zones to redesigning the packaging that dominates the waste stream. The next step is not more studies, but the consistent application of policies that already exist and the political will to hold both producers and local governments accountable. If this was useful, you might also want to read how deforestation and pollution intersect in the Philippines.

Sources

Pollution’s toll: health impact in the Philippines — Explores the direct health consequences of environmental pollution, including plastic-related toxins.

Factory waste hurts Filipino water — Examines how industrial discharge compounds the pollution burden on Metro Manila’s waterways.

Macroplastic survey of Tullahan River in Metro Manila, Philippines. Frontiers in Environmental Science, 2024.

Macroplastic survey of Tullahan River in Metro Manila, Philippines (J-GLOBAL abstract). Japan Science and Technology Agency, 2024.