You need to know where lead dust comes from to successfully clean it up.
Old doors and windows frames painted before 1980 usually have lead-based paint. When the door rubs against the frame this will create dust. This area is called a friction point. Opening and closing and closing old wood window frame can create dust on the window sill and the floor below. Be sure to clean two feet past the door frame or window sill. Lead dust is dangerous to children under 7, and not good for the rest of us, either.
You can safely and easily clean up lead paint dust for children with a daily Swiffer-type mop under all old doors and windows. If you like you may use a damp paper towel. For safety, be sure to dry the area completely.
Lead in Children EPA info.
San Francisco has many old buildings. It’s critical that if you think you may have lead dust and your children, especially under 7, that you use the Swiffer mop method to clean daily where the dust from the friction points on doors and windows with wooden frames falls.
Also, lead-based paint can be found outside on porches and decks.
Painting over lead-based paint with paint made today, will not completely fix the problem. You should consult/hire an RRP certified painting contractor to stabilize the area. Be sure to use that word: “stabilize”.
There are other types of paints, usually referred to as encapsulants, that will eventually flake or rub off at friction points, and then you have the same problem; though maybe a bit less. EPA wants 0% lead-based paint dust in homes with children. Realistically, let’s all work together to do what is possible and clean up the rest.
You may also be interested in this: Lead-based Paint and Children