Microplastics in Jakarta's Rain Reveal Pollution Across Air, Rivers and Groundwater

Plastic pollution reaches the rain above Jakarta

Microplastics are falling with the rain in Jakarta, where researchers from Indonesia's National Research and Innovation Agency, known as BRIN, measured between 3 and 40 plastic particles landing on each square meter of ground per day. The average was about 15 particles in the coastal urban area, and deposition during months with frequent rain was roughly four times higher than during dry months.

The government backed research adds another dimension to the capital's pollution problem. Plastic fragments and fibers can travel through outdoor air, settle with rainfall, and move into soil, drains, rivers and groundwater. Scientists warn that people can encounter these particles through breathing and drinking, while contamination can remain in waterways and soils long after a storm ends.

As of November 2, 2025, Jakarta officials were responding with plans to expand monitoring, improve waste collection and reduce disposable plastics. National officials were calling for an end to open dumping, including the practice of leaving mixed waste exposed to sunlight and rain at large disposal facilities.

BRIN researchers observed plastic fibers and fragments in outdoor air before rainfall. At a coastal sampling site in Ancol, North Jakarta, rainwater contained particles about 0.3 to 0.5 millimeters long, roughly the size of a grain of salt. The materials found reflected familiar urban sources, including clothing, tires, packaging and construction materials.

The study's lead researcher warned that the problem was likely to worsen as plastic use increased. Rain removes some particles from the air, so the dry season brings a different concern: with less rainfall to wash them down, dust and plastic fibers can accumulate in the air people breathe.

What a year of sampling found

The Jakarta study tracked atmospheric microplastics for a full year, using devices that collected rainfall and laboratory analysis to identify particle shapes, sizes and polymer types. Polymers are the materials that make up plastics, and identifying them helps researchers understand where particles may have originated.

Fibers accounted for roughly 86 percent of the particles collected. Most pieces measured between 300 and 500 micrometers, equivalent to 0.3 to 0.5 millimeters. The main materials included polyester, polybutadiene, polyethylene and polystyrene, a combination consistent with textile shedding, traffic activity and ordinary plastic litter.

The researchers concluded that most particles probably came from activities within Jakarta rather than from distant places through long journeys in the atmosphere. Their findings were documented in a paper reviewed by other scientists, available through ScienceDirect as the atmospheric microplastics deposition study.

The instruments were sensitive to particles larger than about 300 micrometers. Smaller microplastics and nanoplastics, which are much tinier plastic particles, were outside that counting range. Specialized instruments are needed to detect nanoplastics.

For comparison, people can inhale dust particles around 10 micrometers in size, much smaller than the study's detection limit. The measurements therefore provide a conservative picture of the plastic falling from Jakarta's atmosphere, with the count covering the particles the equipment could detect.

The seasonal figures describe deposition, meaning the number of particles reaching a surface over a given area and time. During wet months, that rate was about four times the dry season rate. Rainfall moves suspended material out of the air and onto the city below, connecting atmospheric pollution with contamination on the ground.

How plastic moves between sky and surface

Microplastics form when larger plastic products break into small pieces. Some are also made intentionally at small sizes, including industrial pellets and cosmetic microbeads. In Jakarta's urban environment, everyday wear and waste provide several routes into the air.

Synthetic clothing sheds fibers during use and washing. Tires and road surfaces release particles through abrasion, while discarded plastic breaks down under sunlight and heat. Open burning of rubbish adds another source of tiny particles. Wind and turbulence from traffic can lift this material and keep it suspended, especially in dry conditions.

Raindrops act as scrubbers as they fall through polluted air. They collide with particles and carry them onto roofs, streets, parks and water surfaces. Runoff can then wash the particles into drains, rivers and Jakarta Bay. Material left on the ground can dry out and become airborne again.

BRIN researcher Muhammad Reza Cordova, who has studied microplastics in Jakarta's air and rain, described how this movement continues between the atmosphere and the surface:

The plastic cycle does not stop at the sea; it is carried by the wind into the sky and descends again with the rain.

Particles carried by rivers into Jakarta Bay can return to the atmosphere through wind and sea spray, then travel inland through the lower atmosphere. Researchers describe this circulation as a plastic cycle that interacts with the water cycle.

Jakarta's wet and dry seasons affect different parts of that movement. Heavy rainfall brings more particles down onto surfaces. During dry periods, fewer rain events remove suspended material, increasing concern about inhalation as dust and fibers gather in outdoor air and indoor environments.

Rivers carry another part of the pollution

A separate investigation during the pandemic examined nine rivers flowing into Jakarta Bay and detected microplastics at every sampling point. Concentrations ranged from about 4 to 23 particles per cubic meter of water.

The rivers contained more particles during the rainy season. Stormwater can wash plastic fragments and fibers off roads, open spaces and other surfaces, carrying them through drainage networks into waterways. The river findings fit the broader pattern of rainfall moving contamination through the city.

Over time, researchers found an increase in fibers made of polypropylene, a material widely used in masks and other protective equipment during the pandemic. That finding pointed to a waste stream reaching the water system when disposal was unmanaged.

Jakarta's river pollution and atmospheric deposition share a practical connection: particles settling on streets can enter waterways during the next downpour. Plastic already present in rivers can continue toward the bay, where wind and sea spray offer another route back into the air.

Groundwater findings bring the problem closer to homes

Researchers also detected microplastics in urban groundwater in West and South Jakarta, where concentrations ranged from 28 to 236 particles per liter. The finding matters in a city where many households and small businesses depend on wells.

Fragments were the most common form, followed by fibers, films and small beads. Materials identified included polyethylene, along with cellulose based fibers such as tencel and cellophane. The samples therefore contained a mixture of plastic and semi synthetic fibers.

Sampling sites closer to temporary waste disposal locations tended to have higher particle counts than sites farther away. Waste exposed at the surface can break apart through sunlight, heat and water, creating smaller pieces that move with rainfall.

Rain and leachate, the liquid that drains through waste, can carry particles downward. Contamination can also move sideways through drains and canals before entering shallow aquifers, the underground layers that hold groundwater.

The river study reported particles per cubic meter, while the groundwater study reported particles per liter. Each cubic meter contains 1,000 liters, so readers need to keep those units in mind when considering the measurements. The studies also examined different parts of Jakarta's water system.

Open dumps, landfills without full coverage, streets and vacant lots can all supply particles that move through air, surface water and groundwater. Researchers have called for monitoring across all three rather than examining each pathway in isolation.

Health concerns depend partly on particle size

Microplastics can enter the body through ingestion and inhalation. People may swallow them in food or water, or breathe them in with airborne dust and fibers. Particle size affects where material can travel inside the body.

Larger swallowed fragments pass through the gut, while some smaller particles can cross into the blood and reach organs. In the lungs, the smallest particles can settle deep in the airways. Jakarta's rain study counted pieces at or above about 300 micrometers, while many airborne particles are much smaller.

Laboratory studies involving cells and animals have shown that microplastics can cause inflammation, tissue irritation and oxidative stress. Oxidative stress occurs when reactive substances put pressure on cells and can damage them.

Plastic products also contain additives, including plasticizers, flame retardants and dyes. Some can disrupt hormones when they accumulate in the body. Microplastics can pick up heavy metals and organic chemicals while moving through air and water, carrying other pollutants with them.

A 2024 analysis by academic researchers estimated that Indonesians may ingest around 15 grams of microplastics each month, placing the country among those with the highest estimated intake. The figure depends on diets, water sources and environmental concentrations, and exposure can vary widely within Jakarta.

Scientists still need more research to connect particular exposure levels with specific clinical outcomes. Health agencies have advised practical steps to reduce contact with particles while infrastructure and regulations develop.

Indonesia's Health Minister, Budi Gunadi Sadikin, urged residents to reduce exposure and address pollution at its source:

Wear a mask when outdoors, especially during and after rainfall events. The best prevention starts at the source by reducing microplastic pollution before it spreads.

Jakarta plans more monitoring and better collection

Jakarta's environment authority responded to BRIN's findings by pledging to cut disposable plastics, improve waste collection and extend monitoring into air and rainwater. Officials were preparing a wider network of sampling points to follow seasonal changes and identify places needing cleanup or enforcement.

The monitoring program aims to establish a baseline, a starting measurement against which later results can be compared. Tracking that baseline would help officials follow changes in airborne plastics and support policies on packaging and waste handling across the capital.

Asep Kuswanto, head of the Jakarta Environment Agency, described the finding as a warning requiring a coordinated response:

We consider the finding as an environmental warning that requires swift and collaborative responses. Plastic pollution is no longer isolated in seas or rivers. It has now reached the skies above Jakarta.

BRIN researchers have encouraged the government to set a reference level for airborne microplastics. Such a level would give air quality programs a benchmark for tracking this pollutant alongside fine particulate matter and ozone.

Open dumping becomes a national target

Environment Minister Hanif Faisol Nurofiq called for an end to open dumping at final disposal sites and stricter supervision of waste operations. He linked microplastics in rainwater to the continued exposure of large volumes of mixed waste to sun and rain at facilities such as Bantargebang, outside Jakarta.

Hanif said the discovery made changes to disposal practices urgent:

This finding highlights the urgent need to end open dumping at waste disposal sites across the country.

Officials said they were moving toward sanitary landfill systems that cover waste to reduce weathering and install gas capture to lower fire risks and emissions. Covering discarded material reduces its exposure to the conditions that help larger plastic items break into smaller pieces.

Regulators were also considering thresholds for microplastics in air and water, more testing of industrial emissions and possible changes to waste import rules. The import changes under consideration would limit plastic entering the country that could not be safely handled.

Jakarta officials had also highlighted plans for facilities that turn waste into energy to reduce the volume of unmanaged rubbish. Environmental experts stressed waste reduction and safe containment as priorities to prevent new pollution.

Cutting particles before they spread

Scientists and policymakers broadly agree that the most effective response starts before plastic reaches the sky. Reducing plastic use means fewer products are available to shed fibers and fragments into air, soil and water.

Retail measures can target common disposable items such as bags, straws and cutlery, alongside better access to reusable alternatives. Producer responsibility would place collection and recycling duties on the companies selling packaging, including obligations to help finance those activities.

Deposit return systems for bottles and cans are another option. Standardizing materials and simplifying packaging can make products easier to recover and recycle without creating additional waste streams.

Textiles and tires are two major sources of fibers and particles in urban air. Proposed responses include washing machine filters that capture fibers before they enter drains and building rules requiring laundry filters in new apartments and dormitories.

Road dust management could focus on tire wear through better street sweeping along major corridors and systems that capture sediment in storm drains. These measures target particles close to where they are generated, before traffic, wind or runoff spreads them.

Open burning of household rubbish remains another source of airborne particles. Reliable collection and safe disposal are needed to replace that practice. Reducing waste, collecting it consistently and containing it safely address different stages of the same pollution cycle.

Steps residents can take at home and outdoors

Health officials advise a mask that fits well when outdoors on days with visible dust or after rainfall, when settled particles can become suspended again. Household measures can also reduce the dust and fibers people encounter indoors.

Vacuuming with a machine equipped with a high efficiency filter, damp mopping floors and washing bedding and curtains regularly can reduce fibers in the home. Ventilation is helpful when outdoor air quality is good.

Laundry practices can reduce the fibers released into wastewater. Washing full loads, using lower spin speeds and cold water cycles, and fitting a lint filter or external washing machine microfilter are practical options described by researchers.

Choosing durable goods and clothing that shed less, repairing items rather than replacing them, and avoiding rubbish burning can reduce the material entering air and water. For drinking water, many consumers use filters at the point of use that are certified for particle removal.

Residents can also support neighborhood efforts to separate organic waste from recyclables and keep plastic out of drains and canals. No single household action can eliminate exposure, but these measures can reduce contact with particles and ease pressure on shared waste and drainage infrastructure.

Jakarta's findings connect the plastic discarded on the ground with particles found above the city and beneath it. Household precautions are part of the response, alongside citywide monitoring, reliable collection and changes to how waste is handled.

Key Points

• BRIN researchers measured 3 to 40 microplastic particles deposited per square meter per day in Jakarta, averaging about 15.
• Deposition during wet months was roughly four times higher than during dry months.
• Fibers made up about 86 percent of collected particles, most measuring 300 to 500 micrometers.
• The rain study's equipment did not count particles smaller than about 300 micrometers.
• Nine rivers flowing into Jakarta Bay contained microplastics at every sampling point, with concentrations of about 4 to 23 particles per cubic meter.
• Groundwater in West and South Jakarta contained 28 to 236 particles per liter, with higher counts tending to occur near temporary waste disposal locations.
• A 2024 analysis estimated ingestion of around 15 grams per month in Indonesia; exposure varies with diet, water sources and local contamination.
• Jakarta officials planned wider monitoring and better waste collection, while national officials called for an end to open dumping.
• Reducing plastic use, controlling fibers and road dust, and preventing rubbish burning can limit particles before they spread.