Brewing Plastics: Scientists Detect Tiny Plastics in Tea Using Advanced Imaging
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A groundbreaking study published in Environmental Science: Processes & Impacts, a renowned journal published by the prestigious Royal Society of Chemistry, has revealed that premium nylon tea bags release a staggering number of microplastics (MPs)and small microplastics (SMPs) into a single cup of tea.
This research was led by Ms. Pramoda Jayasekara, Mr. Bimsara Kahandawala, Prof. Nathali Silva from the Centre for Excellence in Informatics, Electronics and Transmission.(CIET), Sri Lanka Institute of Information Technology (SLIIT);Prof. Shiromi Karunaratne from the Department of Civil Engineering, SLIIT; Dr. Udaya Wijenayake from the department of computer engineering, University of Sri Jayewardenepura and Advanced Imaging and Artificial Intelligence Research Centre (AIAIRC), University of Sri Jayewardenepura; Mr. Praveen Abhishek and Prof. Anushka Rajapaksha from the Ecosphere Resilience Research Centre (ERRC), University of Sri Jayewardenepura; Prof. Meththika Vithanage from ERRC and the Geological Survey of Denmark and Greenland; and Prof. Eranga Wijesinghe from the Department of Electrical and Electronic Engineering, SLIIT.
Although nylon tea bags are not widely used in Sri Lanka, they are increasingly found in premium and herbal tea products in global markets. Previous studies have reported their potential to release MPs at high temperatures; however, limitations in existing analytical techniques and the need for methodological validation underscore the importance of further investigation.
The team discovered that just one nylon tea bag steeped at around 100°C for 5 minutes can release between 16,000 and 24,000 SMPs & MPs to one cup of tea.As a result, a single cup of tea could contain asurprisingly large quantity of plastic fragments.Since cold and ambient brewing are common in herbal tea preparation, these conditions were also examined. The results showed that even tea prepared under these conditions released thousands of MPs, indicating that contamination is not limited to hot brewing.More than 90% of these particles are extremely small, ranging from 12 to 30 µm, making them difficult to detect with conventional laboratory techniques.
To overcome this, the researchers developed a novel method combining Optical Coherence Tomography (OCT) with a customised image processing algorithm to detect MPs directly in liquid. This approach enables real-time, non-destructive visualisation and quantification of MPs without filtration or chemical treatment.To verifythe findings, the team employed the widely used Nile Red staining method, confirming the accuracy and reliability of their OCT-based detection.
This study also assessed human exposure using Estimated Daily Intake (EDI) calculations. The findings suggest that children may be at greater risk, potentially ingesting up to four to five times more MPs than adults due to their lower body weight.
Beyond its findings on tea, the study introduces OCT as a promising new tool for detecting microplastics in food and environmental samples. The technique offers real-time, non-destructive analysis and can identify particles as small as 12 µm, potentially transforming how scientists monitor MP contamination in the future.
For consumers, the findings may prompt simple but meaningful changes. Experts suggest that those concerned about MP exposure could consider switching to loose-leaf tea or paper-based tea bags, which are very common in Sri Lanka,to reduce the likelihood of MP contamination.
As concerns over MP exposure continue to grow, this research sheds light on a common daily habit that may contribute more to plastic intake than previously understood.
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