I had the chance to try samples of Oscar Mayer "Selects" hot dogs, whose selling points, in addition to a couple of specially seasoned varieties, are that they have no artificial flavors or colors, or artificial preservatives -- notably, no nitrates or nitrites added.

It turns out they use natural sources of nitrates such as cultured celery juice.

What's wrong with that?

Applegate Farms, another producer of organic and "natural", "real food" meats, has a web page about nitrates and nitrites that gives more information about cultured celery juice, and actually undercuts their own health and safety marketing:

The nitrites in our products occur when the nitrates in the celery powder and sea salt react with lactic acid starter culture and convert into nitrites. Without these natural nitrites our uncured products would be gray. [And they would be much likelier to kill you from botulism.]
...

The USDA defines an uncured product as one that has been preserved without the use of synthetic sodium nitrite.

...

What are the health issues associated with nitrates and nitrites?

During the cooking process, especially under high heat, nitrites can combine with amines, naturally present in meat, to form N-nitroso compounds or Nitrosamines. These compounds are considered carcinogens.

From FriendsEat: Oscar Mayer "It's Yes Food", But Is It Really? Why all natural does not mean healthy:

All Processed Meat is UN-Natural and Carcinogenic

Susan Levin, a dietitian and director of nutrition education for the Physicians Committee for Responsible Medicine, told Ad Age the new Oscar Mayer packaged-meat brands are still processed meats, and the risk associated with consuming processed meats are not mitigated by excluding artificial preservatives.

In other words, Kraft’s slick and hugely expensive Madison Avenue “It’s Yes Food” ad campaign is a complete and total sham.

...

Meat companies that label their products natural or organic may use natural sources of preservatives like celery powder or celery juice, but they are still high in nitrates.

And processed meat products labeled “natural” or “organic” contain just as much or more of the cancer-linked nitrates as that of conventional processed meats. The nitrates found in processed meats are converted into nitrosamines which are associated with cancer.

(emphases added)

(Pictures: Kraft Brands; Donna Turner Ruhlman; Nephron at Wikimedia Commons)