How can I prevent lukemia?

Avoid chemicals. I wish we could prevent leukemia. We can't. But there are some chemical exposures that increase your risk of developing leukemia. These include benzene, paint thinners, laquers, varnishes, glues, paint strippers, and solvents. Wear gloves when working with any chemicals and work in well-ventilated areas. Eat well, exercise, and live each day to the fullest...And hope for the best!
You can't. Leukemia occurs sporadically and is not a common cancer. There are risk factors for example: exposure to radiation, some chemotherapy drugs and genetic conditions. The best thing you can do is live a healthy lifestyle.