Plastic contamination found in Jakarta's harvested rainwater
Rainwater harvesting has become a genuine lifeline for many communities across Greater Jakarta's coastal plain, where piped water is often unreliable, saline, or simply absent. But a study published in the journal Microplastics and Nanoplastics in September 2026 introduces a complication: the water collected by those systems may carry plastic additives and, in some cases, microplastic polymer particles.
The research was led by Annisa Fitri Mustafa of the School of Environmental Sciences at Universitas Indonesia, working with colleagues including corresponding author Hayati Sari Hasibuan and collaborators at Cheng Shiu University in Taiwan. Their team sampled both open rainwater and water stored in rooftop harvesting systems at two coastal sites within the Greater Jakarta metropolitan area, home to more than thirty million people.
What the researchers detected
Rather than relying on visual microscopy, the team used two high-sensitivity analytical methods. Pyrolysis gas chromatography-tandem mass spectrometry identified plastic polymers, and ultra-high performance liquid chromatography-tandem mass spectrometry measured dissolved chemical additives at trace concentrations.
In the harvesting system samples, three polymers turned up: polyvinyl chloride (PVC), polyethylene terephthalate (PET), and polymethyl methacrylate (PMMA). PVC is common in pipes and gutters; PET is the material of plastic bottles; PMMA, or acrylic, appears widely in construction. Concentrations and polymer types varied between the two sampling locations, pointing to site-specific contamination rather than a single uniform source.
The chemical additive results were equally notable. After blank correction, the researchers detected compounds including bisphenol A and phthalate plasticizers such as DEHP, DBP, and DEP in both rainwater and harvesting system samples. These additives are not chemically locked into the plastic matrix; they migrate out over time. Several are recognized endocrine disruptors, meaning they can interfere with hormone systems even at low concentrations.
One nuance worth noting: no microplastic polymers were detected above detection limits in the open rainwater sample itself, even though chemical additives were present there. The authors suggest dissolved additives may travel through the atmosphere differently from intact polymer particles, but they are careful to frame the entire study as preliminary baseline evidence, not a definitive exposure assessment.
Context: why Jakarta is especially exposed
Large sections of Greater Jakarta's coastal plain are sinking by several centimeters annually due to groundwater extraction and urban loading. Saltwater intrusion has compromised shallow wells across many neighborhoods, and Indonesia's ongoing capital relocation project has drawn attention to the city's water infrastructure challenges. Against that backdrop, rooftop rainwater harvesting has been promoted as a decentralized, resilient solution. This study does not argue against that approach, but it does suggest that the materials used in collection infrastructure, and how those systems are maintained, can influence water quality.
The researchers point to first-flush diversion devices, filtration stages, and the selection of storage materials with lower additive content as practical areas for follow-up. They also call for expanded sampling across more sites and seasons, particularly given Jakarta's monsoon dynamics, which could affect how plastic particles and additives are deposited from the atmosphere.
Why it matters for hosts
Independent guesthouses, homestays, and small hotels in coastal Jakarta neighborhoods that supplement their water supply with rooftop harvesting should review the materials in their collection and storage systems. PVC guttering, plastic tanks, and unfiltered storage are the components most likely implicated by this research. Installing a first-flush diverter, which discards the initial runoff before it enters storage, and adding a basic filtration stage are low-cost steps that align with the study's recommendations. Communicating transparently with guests about water sourcing and treatment is increasingly valued by independent travelers, and this research gives operators a concrete reason to revisit their setup.
The findings summarized here were first reported by Bioengineer.org, citing the study published in Microplastics and Nanoplastics (DOI: 10.1186/s43591-026-00228-y). This post appears on the Qontaktly travel blog.
First reported by bioengineer.org.