Air pollution caused by airborne fine particulate matter (PM2.5) has been one of the most important environmental risks of public health in Chinese cities. However, to date, there are still rare researches focusing on the male reproductive toxicity induced by PM2.5 exposure, and the underlying molecular mechanism is far from being completely understood. This proposal aims to study the effects of PM2.5 exposure on histone (H3/H4) methylation and acetylation, as well as on the modification level in promoters of steroidogenesis- and spermatogenesis-related genes in mouse Leydig cells (MLTC-1). By doing these, we hope to reveal that PM2.5 affects the expression of steroidogenesis- and spermatogenesis-related genes via altering histone modification status, and the epigenetic mechanism by which PM2.5 induces male reproductive toxicity could be elucidated.