The study, which began collecting samples in 2022, found microplastics in every rainwater sample taken across the capital. Contamination levels averaged around 15 particles per square metre per day in coastal areas, showing that the problem is widespread.

BRIN researcher Muhammad Reza Cordova said the most common materials found were polyester from synthetic textiles, nylon, polyethene from plastic bags, polypropylene from packaging, and polybutadiene from vehicle tyres. 

These appeared mainly as fine fibres and small fragments. “If we can reduce excessive plastic use, it would already be a big step - though this requires effort from each of us personally,” said Cordova.

Scientists explained that the process occurs through atmospheric deposition, where lightweight plastic particles are lifted by wind and industrial emissions before being washed down by rain. 

“After the rain stops, the air is practically clean of microplastics. That is the safest time to go outside for activities like walking or exercising because you are breathing cleaner air. However, this effect doesn’t last very long - once surfaces dry, the microplastics will become airborne again, carried by the wind,” Cordova added.

The main contributors to Jakarta’s airborne microplastics include synthetic fabrics, vehicle emissions, degrading plastics in open spaces, and the open burning of plastic waste. 

Cordova said tackling the issue requires both systemic reform and public participation through better waste management and reduced plastic use. 

“What we can do now is mitigation - through campaigns promoting wiser plastic use and healthier lifestyles. Fifty years ago, we lived just fine without relying so heavily on plastic. So why can't we do it now?” he said.

The spill has spread across approximately eight kilometres of the river, affecting surrounding communities, including El Caballal in the Alamotemapache municipality. Already hit by severe flooding, residents now face a growing water crisis.

“We need water, and with the contamination, we know it’s going to take time. I don’t know how long, and it’s going to be even harder for us,” said Mario Garcia Osorio, a local resident. 

In response, the Mexican Navy has activated a Regional Contingency Plan with the support of the National Agency for Industrial Safety and Environmental Protection (ASEA). Around 300 personnel, aircraft, drones , and oil containment equipment have been deployed to the area to mitigate the damage.