How Nitrite Affects Food

Nitrites are salts used as preservatives, usually within a brine during the meat curing process. The harmful aspect of meat when it spoils is the bacteria causing the spoilage -- for example, the botulinum toxin, which causes botulism. Nitrites prevent such bacteria from proliferating either directly or indirectly by reducing the oxygen and moisture content of the meat. The FDA has set standards for how much nitrites you can safely consume.

Sodium Nitrite Toxicity

There are different types of nitrites, and sodium nitrite is one example. It is more effective than sodium nitrate, but cured meat producers sometimes use the latter, because it contributes to a longer aging process. According to the FDA, a fatal dose of sodium nitrite is 22 to 23 g per kilogram of body weight. Safe levels of this preservative are much lower, though, as proportions slightly lower than indicated can still cause methemoglobinemia, which is a hemoglobin impairment in carrying oxygen, particularly in infants. There is no evidence that there are carcinogenic qualities of these types of nitrites, according to the University of Minnesota.

Potassium Nitrite Toxicity

Potassium nitrite differs significantly in toxicity than sodium nitrite, although it functions identically as a preservative. Specifically, a lethal dose of potassium nitrite is 30 to 35 g in a single dose -- which is much more lethal as a relatively small base amount rather than a proportion that depends on the specific body mass of the person ingesting it. In other words, a 160 lb. man is approximately 72.5 kg, making a lethal dose of sodium nitrite for that man between 1595 g and 1667.5 g. However, a lethal dose of potassium nitrite for that man -- and every man of any weight -- remains 30 to 35 g.

Acceptable Levels of Nitrites in Meat

According to 2011 information from the University of Minnesota, Title 9, Chapter 111, Subchapter A of the Code of Federal Regulations dated 1974 is currently used by the Meat Inspection Service and limits nitrites in foods to 2 lbs. of nitrite per 100 gallons of pickle brine, 1 oz. per 100 lbs. of meat and a 1/4 lb. per 100 lbs. of chopped meat or meat by-product. On the other hand, the USDA limits nitrites and nitrates in meat products to 200 ppm, or parts per million. The USDA figures parts per million as the grams of nitrite or nitrate times 1 million divided by the grams of cured meat that the nitrite or nitrate treats. In other words, 200 ppm of nitrite for 50 g of cured meat is equivalent to 0.01 g of nitrite, as 0.01 times 1 million, then divided by 50, equals 200.

Considerations

Vegetables yield significantly more nitrites then cured meats in most normal diets. Specific examples of vegetables with high levels of nitrites include beets, celery, spinach, radishes and cabbage. The University of Minnesota estimates that up to 90 percent of nitrites Americans normally consume derive from vegetables, while the rest originate in other sources. To place the toxicity of nitrites in cured meats in further perspective, an adult weighing 154 lbs. would have to consume almost 20 lbs. of meat cured with a brine that contains 200 ppm nitrite to reach dangerous levels of consumption, as long as the meat was prepared according to regulations. Under certain conditions not yet fully understood, amines that derive from proteins can combine with nitrites to produce nitrosamines, which may be carcinogenic. Characteristics that might influence nitrosamine levels include meat amine concentration, length of storage, amount of nitrite added during processing, storage temperatures, processing conditions, degree of doneness after cooking and cooking methods.