Lead paint wasn’t banned in the US until 1978 and before that it was used all over the place. Chances are if your home was built before the early 80s there’s lead paint on your walls. It’s probably lurking underneath more than a few layers of non-lead paint – which is good – but that means peeling paint and paint dust from renovations make lead exposure a real possibility – which is bad. Even a little lead paint dust can be harmful, especially to small children.
Once you know or even suspect that there’s lead paint in your home, it’s time to consider encapsulation or abatement. Most people opt for encapsulation, which involves prepping walls to remove all loose paint and then applying a special liquid coating sufficient to encapsulate (or seal in) the lead paint underneath. Sometimes sheetrock or tile is installed over lead paint to keep dust from entering the air. Note that regular paint is NOT an encapsulant.
The alternative is abatement (sometimes ordered by a state or local government), which is the total removal of lead paint performed by an abatement company licensed to safely strip a house of all lead paint. In this case, the hazard posed by lead paint is removed permanently but for many people the cost of removal is prohibitive because the abatement process itself is expensive and afterwards a house or apartment will still need prepping, priming, and painting.
In either case, remodeling work in homes with suspected lead paint should always be done by an EPA Lead-Safe Certified Renovator who will know how to safely work around lead paint and keep it from spreading during renovations. Find an EPA Lead-Safe Certified Renovator at http://www.leadfreekids.org.