In the past, I ignored such label ingredients as sodium nitrites/nitrates as merely a preservative and nothing to worry about. It was the advertising of a local grass-fed beef producer of having no nitrates or nitrites in their meat that made me do some research as to why that would be of concern to some.
Sodium nitrate is a chemical compound used for fertilizers, glass, solid rocket propellant, food preservative, pottery enamel or more. The health concern is that sodium nitrates form nitrosamines -- a human carcinogen known to cause DNA damage. Nitrates convert to nitrosamines when exposed to heat and/or acid (stomach acid). Since most people I know cook their meat and place it in their stomach, this may be of concern. Exposure to nitrosamines seems to promote certain cancers.
Ascorbic acid seems to greatly reduce the formation of nitrosamines, so you will often find these listed together on an ingredient list (and is required by law).
Sodium nitrites help prevent botulism and alters the color of preserved fish and meat (often a more appealing color to the buyer). Similar to sodium nitrates, the nitrites can break down under certain conditions and form nitrosamines. In large quantities, sodium nitrites are toxic to animals and humans. Because of its toxicity, nitrites are dyed bright pink so it is not mistaken for sugar or salt.
Both sodium nitrates and nitrites are approved for use in the EU, USA, and Australia with approved quantities deemed to be safe for consumption by the approving governments.
But, none of this is necessary and there are options to avoid it all together. We sometimes buy meat products from a local/organic farmer and avoid any kind of additive, but at a traditional grocery store, we look for brands like Coleman Natural, Sausages by Amylu or Jones Dairy Farm for items like bacon, sausage, chicken or hot dogs that have NO preservatives.
We choose to not take risks with added food chemicals. One meal probably won't harm anyone, but prolonged exposure to poor quality meats can.
As a rule, the cheaper the meat you buy, the more likely it is to have the preservatives and fillers that cause us harm. Aren't some things worth a couple extra bucks? Read the labels.
P.S. The food our school systems feed our kids (if you can call it food) is atrocious and one of the greatest concerns for me and my kids. There are options. Coleman Natural is able to supply schools with real, preservative-free meats. Check here to see if your school is on the list! If your district isn't on the list, request better food from Coleman here.