Tobacco has a complex composition with many reproductive toxicants, the composition of which is not well understood, and may affect spermatogenesis through sperm genetic material, mitochondria and motile organisms, and cause cellular aberrations in sperm. A number of studies have found that the quality of semen can be significantly reduced in people who smoke heavily over a long period of time, including reduced motility, increased sperm malformation, damage to the sperm DNA integrity index, and possible damage to sperm mitochondrial DNA, all of which may directly or indirectly lead to a reduction in reproductive function.