Smoking can happen either first hand i.e when you smoke, or second hand i.e when you inhale the smoke from a smoker near you. However it occurs, it is very harmful to the health. Smoking is a major risk factor for many medical conditions such as heart disease, respiratory problems, cancer and infertility in men.
Smoking causes damage to sperms, making them unable to fertilize the eggs (female sex cell). Sperm cells contain Protamine 1 and Protamine 2, which are small but very powerful proteins. Normally, both protamine 1 and 2 should occur in a ratio of 1:1, but smokers have less protamine 2, which is the major cause of DNA damage in sperm cells. This imbalance in protamine is also the reason why smoking has been linked with low sperm movement.
Smoking also increases the concentration of free radicals in seminal fluid. These free radicals cause DNA damage in sperm, thereby causing low sperm count. Furthermore, reduced blood flow due to smoking can also affect male erection, causing erectile dysfunction.