@jalan As far as I know, foods marketed as "organic" are legally required to be produced in certain ways. But I honestly don't know how closely those required practices are followed. Urea is a source of nitrogen for crops, true- and I think plants only take it up from the soil. (I don't know for certain if they can absorb such things through their leaves... Google time again!) Even if it is sprayed onto a crop, I'm assuming it will wash off into the soil when it rains- so I won't personally worry about it... too much... unless I'm eating potatoes or carrots... Eewww.

I got the following from Google and the CK-12 Foundation, using the query: "can plants absorb nitrogen through their leaves":
Yes, plants can absorb nitrogen through their leaves via foliar feeding, allowing them to take up nutrients directly from liquid fertilizer sprayed on their foliage. However, this is supplementary; plants cannot directly absorb atmospheric nitrogen gas (N₂) through their leaves and rely on roots to absorb dissolved nitrogen from the soil.
So, by the time we eat something, the fertilizer ingredients will long since have been broken down, and reformed into plant tissue: leaves, roots... whatever part of the plant we're eating. I love potatoes, and rinse/scrub them a bit with water before I cook them. Potatoes aren't safe to eat raw (except maybe in small amounts) for various reasons, and by the time we eat them, they've been sterilized by the heat of cooking.