And specifically, Brassica oleracea shows up against lead, though no amount is given in that table. The referenced webpage [1] mentions 0.1% to 3% (!) of dry weight, though that's in relation to hyperaccumulators generally.
This article [2] gives an indication of what high concentrations may look like in Brassica oleracea, though I still don't have much idea of what those numbers mean to a human being eating the plant. Considerably less than the 10,000+ mg/kg seen in other plants, thankfully.
Turns out 29 of the top 30 are "oops, all Brassica" :-)