There isn't a specific standard for paper dust; however, you may consider submitting a claim if you are experiencing frequent stops to clean the plate and blanket. As evidence, you would need to take pictures of the blankets and note how many impressions it took to build up the dust and its location on the blanket (edge, middle, etc.). The supplier would probably ask for tape pulls of the debris on the blanket that can be sent to the mill for analysis. Providing unprinted paper samples as well as print samples that show the contamination would also be helpful.