Children whose fathers smoked around the time of their conception have at least a 15% higher risk of developing acute lymphoblastic leukemia (ALL).

They found that the mothers smoking behavior had no impact on the children’s risk of developing the cancer, but children whose fathers smoked at the time of their conception were 15% more likely to develop leukemia. Kids whose fathers smoked at least 20 cigarettes per day were 44% more likely to be diagnosed with the disease.
Lead author of the study Elizabeth Milne said, "Study results suggest that heavier paternal smoking around the time of conception is a risk factor for childhood ALL. Tobacco is full of toxins, including carcinogens, it was not unlikely that there could be damage in the cells that produce sperm. Sperm containing DNA (damage) can still reach and fertilize an ovum, which may lead to disease in the offspring. However, the study did not prove that DNA damage in the sperm caused ALL in the children, since the disease was likely to be caused by a number of factors. The study is published in the American Journal of Epidemiology.
Source-Medindia