First of all, what's with the focus on tea bags? How does that compare with microplastics entering our food and drink from the plastic-lined paper cups we drink hot tea and coffee out of, from the cling wrap that covers our food as we heat it in the microwave, from the Tupperware and other plastic containers we heat our food up in, from the bottled water that sits inside plastic for months, from all of the plastic bowls and utensils we use in our kitchens, from the disposable serrated plastic knife we might use at an event to cut our chicken, and so forth? Why tea bags?
Second, how do "microplastics" compare to micro-everything else? Surely if you brew tea in a wooden container, "microwood" particles are entering the drink. Surely when you scrape your stainless steel spatula against your stainless steel skillet making scrambled eggs, "microsteel" particles are embedded in your eggs. How does the body deal with micro-everything? Is there any reason to think plastic is more harmful? Is there any specific supposed health consequence, like a specific type of cancer or increased aging or something?