Microplastics are now impossible to avoid. They have made their way into everything from agricultural soils to freshwater systems. So, it is unsurprising that they end up in most foods and drinks. However, some methods of packaging or serving these items can increase microplastic exposure even more. One such example is the plastic tea bag. While many tea bags are still made of a cellulose material, some brands use a plastic mesh, despite the well-established fact that plastics can break down in hot water.
What’s in your tea?
Studies have reported particle release from tea bags, along with the migration of other plastic-related chemicals, such as phthalate esters (PAEs) and bisphenol A (BPA), which are added during production for increased flexibility, durability and thermal resistance. One study even reported that a single plastic tea bag releases billions of microplastic pieces at normal brewing temperatures.
Now, a new study, published in npj Science of Food, has analyzed plastic tea bags from four different brands to break down their average microplastic release, the types of microplastics they contain and the PAE and BPA content in the average cup. The study compares tea brewed with plastic tea bags to bagless bulk tea.
Plastic tea bag versus bulk tea contamination
Researchers involved in the new study screened four bagged-tea brands with plastic tea bags purchased in Turkey. They compared these to 14 bulk-tea brands. The plastic bags were brewed for three minutes at approximately 95°C (203 degrees Fahrenheit). Bulk leaves underwent direct chemical digestion rather than an equivalent brewing experiment. The researchers used microscopy to count suspected particles, infrared spectroscopy to identify a subset and chromatography to measure chemicals in bagged-tea infusions. Health risks were then modeled.
The plastic-bag brands produced averages of between 555 and 2,498 microplastic particles per cup under the tested brewing conditions, with some brands producing significantly more than others. The methods used only identified particles greater than 100 micrometers, so these concentrations don’t include smaller particles that may be present. The particles from these bags were all identified as polyamide fibers, consistent with the bag material.
BPA and plasticizer compounds were also found in all four bagged-tea infusions. The team says that the modeled BPA intake from the bags reached between 4.55% and 21.70% of the European Food Safety Authority (EFSA) daily intake benchmark for BPA.
The bulk tea leaves contained between 146 and 1,178 particles per kilogram. This converts to approximately 0.3–2.4 particles per 2-gram (0.07-ounce) serving of tea leaves. The comparison is not direct, since the bulk tea was not brewed, but the results still point to a far lower concentration of microplastics in the bulk tea. In contrast to the tea bags, the polymer distribution of bulk tea consisted of a mixture of polymer types.
The study authors write, “The primary drivers for this mixed polymer profile are the use of plastic sacks and bundles (PE/PP) in agricultural activities, combined with the deposition of atmospheric dust, which typically contains PET and PA fibers. Furthermore, during industrial processing, tea leaves maintain intensive contact with plastic-laden equipment, including loading machinery, conveyor belts and rolling (twisting) stations. This mechanical interaction facilitates MP transfer or plasticizers from the machinery to the leaf surface.
“During the withering stage, leaves are exposed to ambient air for extended periods, making the gravitational settling of airborne MPs (microplastics) a significant contributory factor to the overall pollutant load.”
Potential health risks
While health impacts are not directly measured in this study, the researchers conducted a health risk assessment based on toxicological parameters. In general, the expected intake of microplastics and plasticizers based on average daily tea consumption is negligible. However, the study authors do exhibit some concern about the concentration of BPA found in the tea brewed with plastic bags.
Some studies suggest BPA disrupts hormone levels, but it is somewhat unclear what levels may be safe and suggested limits vary. While the amount of BPA was only 4.55%–21.70% of the EFSA daily intake benchmark, the team notes that this accounts for only a part of the total daily intake and the benchmark may be exceeded with higher tea intake or with BPA from other sources.
The study authors write, “Our study found that BPA intake could reach 21.7% of the EFSA TDI value, a finding that serves as a critical warning, particularly for vulnerable groups such as pregnant women and children.”
Limiting exposure
Regardless of whether official suggested limits are surpassed, the team suggests limiting consumption of microplastics, BPA and other plastic-related chemicals when possible. Avoiding plastic tea bags is a relatively simple way to do this. The team suggests sticking to loose tea brewed in ceramic or metal infusers. They also suggest cold-water washing bulk tea leaves before brewing to reduce environmental contamination.
More research is needed to fully examine risks and which precautions may be truly necessary. Broader sampling and improved particle characterization would address some of the limitations of the study, along with assessing direct chemical measurements in brewed loose-leaf tea.
source: MedicalXpress
Image Credit: Pixabay/CC0 Public Domain
