A man’s fertility rate generally relies on the quantity and quality of his sperm. If the amount of sperm a man ejaculates is low or if the sperm is of poor quality, it will be difficult and sometimes impossible for him to impregnate a female.
According to Prof. Oladapo Ashiru, a male infertility is usually caused by problems that affect either sperm production in the testes or sperm transport.
Extended exposure to benzenes, toluene, xylene, herbicides, pesticides, organic solvents, painting materials and lead might contribute to low sperm counts. Exposure to lead or other heavy metals also can cause infertility.