From years in the real estate business, I can tell you that the "threat" of lead in paint looms larger than the fact. Lead collects in the system, so it has a cumulative effect... the more you ingest, the more it becomes a problem.
But it's the ingesting that is crucial: you have to eat enough paint or it's dust to make it matter.

Lead is a very useful element and has been with us throughout history. It was/is added to paint as a pigment and to increase its corrosion resisting qualities, its durability and its appearance. White and yellow paints are mainly where it was used, although it wasn't in all paints. I've seen lead putty, too, for sealing windows cracks and so on - all the places we would use caulking today.
Back when pewter (tin, alloyed with copper and lead) was a common material for household items like DISHES, it WAS a problem. Food and drink, especially alcohol, leach the lead from the pewter where it can be ingested.

The law as we know it today was primarily aimed at children under 6. This is due to their distasteful habit of sticking everything into their mouths. The popular image was of a toddler gnawing on his crib - painted with leaded paint.
In truth, they can ingest it from deteriorated paint, minute chips or dust from paint removal. Therefore, it was banned in this country in 1977.

But the threat is something of an urban legend. It isn't that it wont hurt you. Rather, it *may* under the right conditions, so we become fearful across the board. Similar fears arise with cycling helmets.
Actually, leaded paint is still in use for some applications (military, parking lot markings) and not all countries have discontinued it. In THIS country, though, it cannot be added to any paint intended for the consumer market. Its removal in real estate scenarios is mandated to chemical or mechanical means, like scraping. You have to be certified to remove it if you are a licensed contractor and sanding is verboten for these guys.

So follow the practice of painters everywhere -
1. Wear a mask, goggles, long clothing and gloves when sanding any paint.
2. Work in a booth. Erect one from plastic sheet and filter the air as mentioned above.
3. More good advice: "To minimize the spreading of dust, wet the floor while
sanding. A 20" box fan with a 20X20" home heating type filter with trap
most of the air borne dust. Keep all children away from the work area.
Sweep up all dust or vacuum with a unit that has a bag and make sure
you don't throw it in the regular trash, take it to a disposal site." Dispose of the clothes worn during the removal the same way.
4. Shower soon thereafter.
3. Don't rub your eyes while working, nor eat anything near the sanding area.

Common sense, really. No more fear, eh?