Scary vegetable cooking water. The longer you boil it, the more concentrated the pesticide residues.

A school of thought below.
https://www.thehealthyhomeeconomist.com/should-vegetable-cooking-water-be-saved/

and a recent report:

[PDF]The 2016 European Union report on pesticide

https://www.actu-environnement.com/media/.../news-31777-efsa-pesticides-aliments.pdf
(I do not have much luck linking to a pdf so the link needs copying and pasting)