According to the American Cancer Society, the nitrates used to treat hot dogs have been linked to cancer in animal studies.
Nitrates are used to treat meats to prevent botulism and greying. They also occur naturally in leafy vegetables. However, the naturally occurring version doesn't convert to nitrites, like the kind added to meats. In general, you should read your labels and try to limit the number of chemicals you consume. Also, get screened for colorectal cancer beginning at age 50.