Lead poisoning is a very serious problem. In houses built prior to the 70s, you might find that there are building materials that contain lead, most commonly pipes and paint. How can you make sure? If you have a metal pipe that you suspect might be made from lead, take a sharp object and see if you can make a scratch. Since lead is a soft metal, you should be able to do so without problem. For paint, you might be able to notice it peeling in a pattern that looks like lizard skin.
What should you do if you find out that you do indeed have lead in your home? If it is your pipes, you should have them replaced as soon as possible, since you will be taking in lead with your drinking water. If it is paint, you should be careful in replacing it, since sanding paint containing lead will release lead particles in the air. If you decide to remove it yourself, make sure you research proper techniques before starting, since you could spread lead dust throughout the home if not careful.