It is all a matter of the risks you prefer and the risks worth worrying about. Every time you cough or spit out an orange seed, you spray the world with germs, whether you are ill or not. Any one of those germs could mutate into a deadly plague that would wipe out humanity, including you; aren't you ashamed!?! Aren't you terrified?!? How dare you!!!

And don't you dare commit suicide out of well-deserved guilt; any of the germs feeding on your corpse could mutate... etc!  

Nitrite is a dangerous poison. Never mind the cancer, inorganic nitrites are not many times safer to eat than cyanide.

Now why on Earth should we even think of putting stuff like that onto our food? Could it be because we need to preserve that food so that we can have it available when fresh food is unavailable? But there are other ways of preserving food without nitrites aren't there? Sure, if you don't mind living on biltong! Nice for a while, but it palls. Also, some of the bits that we preserve with nitrite are not tasty by themselves, but with a bit of smoke and seasoning and admixture of other ingredients they aren't half bad (except for the British banger, which is... well...) 

 But those bits, if not treated suitably are prone to kill. They tend to support the growth of of Clostridium botulinum and similar anaerobic bacteria, and in our history thousands of people have died from botulism; in fact, the very term botulism comes from the Latin for a sausage. Eating a sausage was a calculated risk, or at least amounted to weighing up the relative advantages of starvation and food poisoning!

  But the most important food poisoning bacteria of those types were anaerobic, and someone discovered that if you added a bit of saltpetre to the food to help conserve it, botulism suddenly receded as a problem -- the bacteria couldn't grow in the presence of such an oxidising agent. Later on we found that nitrites were in some ways superior to nitrates, and I am not sure that nitrates are used commercially for meat preservation any more.  

It is very possible that if we had never used nitrites as a preservative, and someone had recently sought permission to use them nowadays, permission would have been refused, but what we would have used in their place, I have no idea. Canning, and salt, I suppose. Lots of salt!  

Anyway, as far as I know, the nitrites are not especially carcinogenic as such; they just are prone to form nitrosamines under some circumstances. Nitrosamines definitely are carcinogenic.   So it is a good idea to beware of forming nitrosamines, such as by scorching meat too badly.  

But I am not going to give up my polonies and hams for a scare that to my knowledge has never figured in any epidemiological study. If you can buy good quality food and eat your vegs in a healthy balance with your meat, then my advice is to go ahead and do so without worrying.