Does alcohol or smoking reduce male fertility ?

Yes: While the data are difficult to break down fully, it should make intuitive sense. Tobacco (and for that matter marijuana) contains hundreds of toxicants which can interfere with sperm dna. Alcohol use should be limited to a few drinks per week.

Yes: Both can have direct toxic effects at level of testicles. Smoking can create "oxygen radicals" that can directly effect sperm membranes and function of sperm. Both can have indirect effect at level of hypothalmus and pituitary, particularly alcohol, and effect stimulation properties on testicular production of sperm. Lastly, from testicles to ejaculation is 90d, thus effect can be long lasting!

Decreases chances!: Studies have shown fertility treatments, particularly ivf are 50% less successful when one or both members of a couple smoke. In addition to decreasing the chance of conceiving, children that grow up in homes of smokers have higher incidences of asthma, respiratory problems, and require more frequent visits to pediatricians for illnesses.

Yes: Studies have shown a 23% v in concentration, 13% v in sperm motility & ^ in abnormal sperm morphology in male smokers.