Hi, I'm not the expert you are asking but I do have a technical, chemical background.

None of the fertilizers I am aware of in hydroponics is a nitrite salt. We don't use nitrites. We do however, use nitrates as a principal ingredient of our fertilizer mixes.

Nitrites and nitrates both contain nitrogen and oxygen, but they are like comparing carbon monoxide to carbon dioxide. Carbon dioxide is a natural gas we all produce and exhale. On the other hand carbon monoxide will chemically kick oxygen out of your lungs and smother you.

I bet whoever is starting that rumor doesn't know the difference.

But, it is possible that there are some nitrites in our fertilizers as contaminants. Hydroponics however is no different than Farmer John's using the same basic fertilizer compounds that have been used since people started selling commercially formulated fertilizers that everyone uses. When nitrates are in water, some are converted into nitrites by bacteria. This is a problem and agricultural run- off leaches nitrites into the aquafers.

You can't get way from this by going organic and growing in soil. There are more soil-born bacteria by far than in hydroponics where systems are kept especially bacteria free if we expect to grow anything. Organic farming practices stimulate the production of even more nitrites to leach out. This is because the ubiquitous soil-borne bacteria thrive on manure and turn the naturally ocurring nitrates in manure which makes it a good fertilizer into nitrites!

Edit: I tried to answer your question as it was presented, but sometimes answering questions the way they are asked diverts attention from the underlying concern. That is the case with nitrites. Although peer review in science has not shown a link to cancer in human from nitrites (medicine has shown they are nutritious), personal choice of many people is to avoid nitrites, because they are used as preservatives and if fried in high temperature oils to decomposition who knows what much result in the sludge at the bottom of the pan. The person wishing to avoid nitrites would look at their exposures and determine the major contributors of them. Processed and cured meats, like that slice of pepperoni pizza, BLT or ham sandwich completely swamp all vegetable sources. To eat these yet be concerned about veggies, hydroponic or not ... would be illogical. But if you really push the exposure here is what you will likely discover (my speculation): Hydroponically grown veggies are usually fresher and more bacteria free and that will correlate with the lowest nitrite veggies of all. Older, mishandled, and veggies you leave in your fridge a long time as they age increase dramatically in nitrite composition because part of the aging is bacterial decomposition with nitrite byproduct. On the other hand, the roots of hydroponic veggies will likely have a somewhat elevated nitrAte level, simply because they are well nourished, but not dramatically high.

Probably for the aquaponic people who have to deal with more bacteria due to less sterile conditions and a system vulnerable to bacteria growing in rich fish poop when out of control. It would be a problem there, but probably for the fish, and I bet the plants wouldn't mind and it would be metabolized healthily as a nutrient before it made it out of the root. You asked about hydroponics, though, not composting and fish tanks ;-)

This post was edited by PupillaCharites on Sun, Jul 7, 13 at 21:34