You need to know where lead dust comes from to successfully clean it up.
Lead dust from from the door or window parts that rub against each other. For example where the door rubs the frame. In older homes and child care facilities these areas probably have layers of lead-based paint. As the doors and windows rub against their frames, dust is created. This dust contains microscopic lead.
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. Do this daily.
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.