Meat and poultry processors could lessen everyone's chances of contracting cancer by reducing or eliminating the nitrite and nitrate preservatives they place in 10 percent of our food, a National Research Council panel said yesterday.

The nation should also try to cut nitrite-nitrate consumption in other ways, such as reducing nitrate fertilizer runoff into lakes and rivers, the group said. This is increasingly contaminating Americans' drinking water.

Still, nitrite, nitrate and related compounds are by no means a huge cause of cancer such as cigarettes, the group added.

A person who smokes a pack of filter cigarettes a day gets 17 times more such compounds than in an average daily diet.

These chemicals are causing no provable human cancer epidemic, but they are highly suspect because of their effects on animals.

Nitrite and nitrate form harmful nitrosamines, which are powerful cancer-causing agents.

It is the formation of nitrosamines and related compounds in the body and in cooking that is the main fear, rather than nitrite-nitrate consumption itself.

Almost all vegetables and fruits contain nitrite. They contribute nearly 60 times more nitrite than preserved meats to the average American diet.

Most persons need not make any major changes in what they eat and certainly should not stop eating healthful fruits and vegetables, committee members stated.

But "I've started drinking orange juice," which is rich in vitamin C, said Columbia University biostatistician John Van Ryzin.

Vitamin C and Vitamin E may inhibit the formation of nitrosamines and may counteract the nitrite in meats, vegetables and fruits.

For centuries, nitrite and nitrate have been used to preserve meat. They now are found particularly in bacon, ham, hot dogs, sausages and preserved meats of all kinds.

Nitrite protects against deadly botulism, and no chemical substitute for it has yet been discovered although meats also can be protected by freezing, canning, pickling or drying.

It also gives meats a pink color and sharp taste consumers have come to regard as natural, though often it is not. Nitrate, which is converted to nitrite by chemical action, is usually added to meats to augment nitrite protection.

Nitrite in bacon has been reduced sharply in recent years by order of the Agriculture Department.

Uncertain as to what to do next about these chemicals and facing food industry opposition to more restrictions, the USDA and Food and Drug Administration last year asked the National Research Council, a research arm of the National Academy of Sciences, to study the matter.

The NRC committee headed by Dr. Maclyn McCarty of Rockefeller University reported that:

* Nitrite should be reduced in all products "to the extent protection against botulism is not compromised," an extent still unsure, though nitrite has been reduced in bacon and there are nitrite-free products on sale, especially in Sweden and Canada.

* Nitrate should be eliminated from most products, since there is no evidence that it has any direct preservative effects. But it still "may be necessary" in fermented and dry-cured meats, by no means a tiny category because it includes salami, pepperoni, summer sausage, "country-cured" ham and beef jerky.

* The country should also try to eliminate nitrite, nitrate or "nitroso-compounds" in many other sources: beer, drugs, cosmetics, agricultural chemicals, the chemical aroma in new car interiors, workers' exposure in rubber, leather and rocket-fuel manufacture and all tobacco smoke, as well as in snuff and chewing tobacco.