science

And the paint, don't forget the leaded paint. And the ceramic tile. And cosmetics. And costume jewelry. And pipes/plumbing. And pottery. And older vinyl, like blinds. And almost all older strained glass uses lead to hold the panels together. And even older plastics often contained lead to soften the material, and we all know how badly old plastic often deteriorates.

There's a shit ton of lead in products made before the turn of the century.