MAPK8 and inflammatory bowel disease: Epidemiologic studies support the association between PM exposure and increased risk of appendicitis and hospitalization in patients with inflammatory bowel disease (IBD).4, 5 Ananthakrishnan et al. reviewed the environmental triggers of IBD, suggesting that PM or its components may alter the mucosal defense of the host and trigger immune responses.6 In addition, activation of key inflammatory pathways in multiple organs, such as NF‐κB, JNK, MAPK,7 Nrf28 and STAT3,9 have been associated with PM exposure.