Well just wash all veg thoroughly before cooking or eating raw. That will get rid of almost all residues. My point was that brassica water makes for not nice gravy, and I can't think of a good use anyway for water that spuds have been boiled in, except for when you make those lovely thick winter stews that you boil up for two hours with shin of beef, potatoes, carrots, swedes and onions. I'm making a vast crock of that this weekend, to go with Atora suet dumplings, what else. Just the thing for eating off your knee out of a big bowl in front of Strictly on Saturday and the results show on Sunday. I think she doth worry too much. Eating lots of veg will far outweigh in benefits the risks of ingesting what are probably tiny amounts of toxins.