The product works wonderfully, everything is OK. But I had to completely disassemble the appliance before using it so that I could wash all the plastic parts. There was slightly greyish dirt everywhere (even inside the appliance), which can be removed with a damp cloth and standard detergent. With a recently purchased hand blender from Galaxus, the same phenomenon was evident on the white plastic surfaces. What is the reason for this and is the dirt harmful to health?