Many (most? all?) hotdog packagings nowadays have the words "No nitrites or nitrates added".
What they use is celery juice, a 100% natural ingredient which does have nitrites. Nitrites exist in many common vegetables. Nitrites are not bad unless they react with protein to form nitrosamines, and the latter are carcinogenic.
This brings up a question: if nitrites are bad in meat, is it harmful to eat celery or other vegetables with meat together in a meal as they get mixed inside the stomach?
It was found that nitrosamines are formed under high heat (grilled hot dogs, anyone?). But then, it was also found that the presence of ascorbic acid (vitamin C) inhibits the formation of nitrosamines.
And all cured meats now have ascorbic acid added along with celery juice.