[whiw]

I am not a chemist, so take this with a pinch of salt: wouldn't lead chromate + sodium bicarbonate make lead carbonate, a white precipitate? Sodium bicarbonate is likely in your kitchen cupboard already.

[adrianN]

Pretty hard to see precipitated dust at concentrations in the ppm range.

[BenjiWiebe]

Not a chemist either but lead oxide is actually more soluble in water than lead chromate, so a double replacement reaction won't favor lead chromate -> lead oxide.

[kragen]

WP tells me lead chromate's solubility in water is 0.00001720 g/100 mL, so, no, it won't.

[whiw]

I meant lead carbonate, not lead oxide.