PM2.5 exposure resulted in significant increases the expression of cardiac hypertrophy markers (ANP, BNP, β‐MHC, α‐MHC, SERCA‐2a) and myocardial fibrosis indicators (Collagen I and Collagen III), whereas melatonin treatment reversed these effects. The gene discussed is NPPB; the disease is Myocardial fibrosis.