Hot tea and coffee contain highest microplastic levels, study finds

Microplastics have become impossible to ignore. They drift through ocean currents and settle in soil. They've been found in human blood. Now researchers have traced a significant pathway straight into our bodies: the drinks we consume every day, particularly the hot ones we reach for without thinking.

Scientists at the University of Birmingham set out to measure microplastic exposure through everyday beverages. They tested 31 common soft drinks available in UK shops—hot and cold varieties from popular brands—to establish what an average person actually ingests. What they found was stark: hot tea and hot coffee contained far more microplastics than anything else on the shelf. Hot tea ranged from 49 to 81 microplastic particles per liter. Hot coffee held between 29 and 57 particles per liter. By contrast, iced tea measured 24 to 38 particles per liter, and iced coffee came in at 31 to 43. Fruit juice, energy drinks, and soft drinks all registered lower still, ranging from 19 down to 13 particles per liter.

The temperature difference was the first clue. Heat itself appears to accelerate the breakdown of plastic polymers, causing fragments to break free. But the researchers identified something more specific: the cup itself. When a disposable lid rubs against the rim of a plastic cup, it sheds microplastic particles directly into the liquid. The act of stirring and sipping through a lid compounds the problem. The brewing method matters too. Longer steeping times, hotter water temperatures, and vigorous swirling all push the microplastic count higher. The same tea leaves brewed in a durable ceramic mug showed significantly fewer particles, suggesting the container—not the beverage itself—was the primary source of contamination.

This finding created a puzzle with earlier research. Chinese scientists from Guangzhou Medical University had previously shown that boiling water could reduce microplastic concentration. Their theory held that calcium carbonate in hard water traps plastic particles in the limescale that forms when water heats up. But commercially prepared hot tea and coffee don't seem to benefit from this protective mechanism. The industrial brewing process, the disposable packaging, and the handling all work against it.

The researchers point to several factors working in concert. Heat accelerates polymer degradation. Single-use plastic cups and lids are engineered for convenience, not durability. The friction between lid and rim creates a constant source of particles. The brewing itself—the temperature, the time, the agitation—all contribute to the final count. What began as a simple question about what we drink has revealed a system designed to shed plastic into our bodies with every sip.

The path forward remains uncertain. Researchers emphasize that more study is needed to understand the long-term health implications of regular microplastic ingestion. Government action could help: legislation restricting or eliminating single-use plastic cups and lids would remove the primary source of contamination. At the individual level, the answer is straightforward but requires deliberate choice—switching to reusable mugs and cups made from ceramic, glass, or metal. It's a small change that compounds across millions of daily decisions, but it's one of the few interventions available right now.