This study investigates differential expression in human blood leukocytes, from subjects who work in print shops, exposed to particles over time. The time points range over 2 weeks: 1-Monday, 2-Friday, 3-following Monday (rested), and 4-Friday Overall design: 40 RNA samples were extracted from human blood. Some did not pass quality control. We are left with 33 samples, from 9 individuals, most with all 4 time points (TP), and three with one TP missing.