A mechatronics engineer works to automate the transfer of materials and goods, and the manufacturing process. Their tasks involve identifying areas for task automation, designing, developing and testing potential mechatronic devices, and implementing design solutions.
A typical tea bag has somewhere between a gram and two grams of stuff in it. If the entire contents were nothing but fructose, and that fructose completely dissolved when you made your tea, you'd consume between 4 and 8 calories (carbohydrates contain 4 calories per gram) per cup of tea -- so that's the ceiling.
The only danger I can think of would be mold growing on the damp bag, which is not really a concern over a period of five hours. Really, though, (most) tea isn't all that expensive and it will taste better if you use a new bag.