Preservatives are a type of additive used to help stop food from spoiling.
Nitrates and nitrites are used to preserve meats such as ham and bacon, but are known to cause asthma, nausea, vomiting, and headaches in some people. In addition to allergic reactions, the same is true for sulfites (sulfur dioxide, metabisulfites, and others), which are commonly used to prevent fungal spoilage, as well as the browning of peeled fruits and vegetables.
Sodium nitrite in some foods is capable of being converted to nitrous acid when ingested by humans. While animal testing showed that nitrous acid caused high rates of cancer, it is still in use.
Benzoic acid aka sodium benzoate is added to margarine, fruit juices, and carbonated beverages. It can produce severe allergic reaction and even death in some people.
Sulfur dioxide is a toxin used in dried fruits and molasses as well as to prevent brown spots on peeled fresh foods such as potatoes and apples. Sulfur dioxide bleaches out rot, hiding inferior fruits and vegetables. In the process, it destroys the vitamin B contained in produce.
While antioxidants such as alpha-carotene are recommended by health specialists to prevent premature aging, some of the antioxidants used as food preservatives may be unhealthy. Contained in nearly every processed food on the market, antioxidants prevent fatty foods from spoiling when exposed to oxygen.
BHT (butylated hydroxytoluene) and BHA (butylated hydroxyanisole) are two of the most widely used, yet controversial of all antioxidants. So alarming were the results of BHT and BHA in animal testing, that a number of countries have severely restricted their use.
Some people have difficulty metabolizing these chemicals, which is thought to result in health and behavioral problems, and hyperactivity. They cause allergic reactions, may also contribute to the development of tumors and cancer, as well as be toxic to the nervous system and liver.
In spite of these findings, the use of BHT and BHA has increased, rather than decreased, in the U.S.A.
Each year, the American food industry uses three thousand tons of food color. Many coloring agents are derived from coal tar, and nearly all coloring is synthetic. Norway has a total ban on all products containing coal tar.
Though some artificial food dyes have been banned because they are believed to cause cancer, most dyes used today are of the artificial variety. They are also linked to allergies, asthmas, and hyperactivity.
The long list of foods and beverages in which color is altered includes butter, margarine, the skins of oranges and potatoes, popcorn, maraschino cherries, hot dogs, jellies, jellybeans, carbonated beverages, and canned strawberries and peas.
Even the chicken feed on large-scale egg farms is colored so that chickens will lay golden-yolked eggs similar to those laid by free-range chickens. Talk about the goose that laid the golden egg!
my info came from here there is alot more to read