Ummmmm, do you know what nitrates are?
Do you read food labels? Processed meats in particular are very high in nitrates which are legal as preservatives which suppress harmful bacteria primarily in bacon, ham, salami and some cheeses. You eat cold meats? How about grilled meat? Because for example, nitrites in processed meats (hot dogs, sausages, burger patties) are in close proximity to proteins (specifically amino acids) so when cooked at high temperatures this allows them to more easily form nitrosamines, which are proven cancer-causing compounds.
Don’t eat much meat, ok, but they’re pretty common in veggies too. Things like spinach, lettuce, beets, celery and carrots are high in nitrates too.