IT'S DIFFICULT to imagine what malt vinegar has in common with beer and Scotch. But the Food and Drug Administration is planning to find out if the malt used in the vinegar contains the same nitrosamines found in the two alcoholic beverages.

The same malt is used in beer, vinegar, bred, cereal, candy or syrup. The few experts who have studied the levels of nitrosamines in the non-alcoholic products say they are "minute." But FDA wants to find out for itself.

While nitrosamines seem to be ubiquitous, there are no known levels at which it is safe to consume them. As a group they are among the most potent carcinogens known to man. They cause cancer in every species of test animal in every organ. They form both in the stomach and in foods (especially in bacon after it is fried. when nitrites combine with amines. In processed meats, sodium nitrite is used to flavor, color and preserve the meats. Amines, found in other foods, tobacco smoke and drugs, combine with the sodium nitrite. USDA has made efforts to reduce the level of nitrosamines in bacon.

In August 1978, The United States Brewers Association learned that most beers produced in Europe contain nitrosamines, which is why FDA wants to look at malts.

The brewers did not know the source of the nitrosamines in their products and authorized studies. In the meantime, the Association issued a statement downplaying the potential hazards: "We have been informed that, to date, there is no medical evidence that at these levels these compounds are harmful to man. Moreover, these compounds are so widely present in the environment and in a wide variety of common foods, in ambient air, cosmetics and pharmaceuticals, the complete avoidance may be a practical impossibility. The human body itself produces nitrosamines, and they are found in the bloodstream in the parts per billion (ppb) range."

By March of this year the U.S. Brewers Association had learned that it was the malt drying process that created the nitrosamines. The Association told FDA: "it might be feasible for U.S. maltsters to introduce techniques before summer's end to reduce the nitrosamine levels in malted barley."

By August, almost a year after the first announcement, FDA issued the following statement: "The malt beverage industry has been working on ways to reduce or eliminate nitrosamines. The industry had told FDA it expects positive results within a matter of months. FDA is monitoring the industry's actions to make sure the nitrosamines are reduced to the extent possible, and is considering what regulatory options are available if industry cannot reduce these levels."

The same month FDA released the results of a National Science Foundation study of nitrosamines in 18 beers as well as some Scotches.

On Sept. 18, Chicago televesion consumer reporter Roberta Baskin released test results which showed that some beers contained far more than the 2 or 3 parts per billion the brewers said were in them.

The following day the Center for Science in the Public Interest (cspi) petitioned FDA to require that within six months brewers "demonstrate that their products contain no detectable amounts of nitrosamines."

In addition CSPI asked the agency to notify the public about nitrosamine levels in both imported and domestic beers sold in this country.

Baskin filed more than one Freedom of Information action seeking FDA's test results. She was told the work had not been completed.

After a week of intense publicity, following Baskin's four-part report, FDA released its test results which showed only two beers out of 30 without detectable levels of nitrosamines: Coors and the imported Guiness Stout.

Last month the U.S. Brewers told FDA that after Jan. 1,100 percent of its beers would be "substantially free of nitrosamines." This can be accomplished by altering the method used to dry the barley malt.

"Substantially free" means levels of nitrosamines will not be detectable below 5 parts per billion. Equipment to monitor nitrosamine levels is not reliable below that level according to FDA. As of Jan. 1, FDA has announced it will test domestic and foreign beers "for nitrosamine content. The results of these tests will be made public immediately," according to the new FDA Commissioner Dr. Jere Goyan.Beer which contains more than 5 parts per billion will "be subject to regulatory action." How often the beers will be tested depends on what the agency finds during its first survey, according to FDA spokesman Wayne Pines.

The level of 5 parts per billion is one-half that which is acceptable to the Department of Agriculture in its bacon testing program.Michael Jacobson, director of CSPI, notes that even with these lower levels beer drinkers will still ingest far more nitrosamines than bacon eaters because of the sheer volume of beer which is quaffed.

A 16-ounce can of beer may contain 14 times the level of nitrosamines found in two slices of bacon. What may be equally significant is that the nitrosamines in beer, nitrsodimethylamine, are considered even more potent than those found in bacon, nitrosopyrrolidine.

Yet, FDA spokesman Pines has said that "On the basis of information to date, there is no reason for beer drinkers to alter their consumption habits." In a telephone interview, Pines went on to explain that "on the basis of what we know today, there is no basis for recommending a particular brand of beer, because the number of bottles tested is relatively small."

According to microbiologist Jacobson, "While it is true that we are exposed to nitrosamines from various sources, exposure should be reduced wherever possible. One of the easiest places to reduce exposure is from beer."

One of this country's foremost cancer researchers, Dr. William Lijinsky, says he is going to "continue to drink beer, but I will choose the beers that have the lowest concentrations. At the very lowest levels, 1 or 2 parts per billion, I feel, while you cannot dismiss that as completely unimportant, it is not of great importance."

Lijinsky, directory of the chemical carcinogenisis program at the Frederick (Md.) Cancer Research Center, says he is more concerned about getting nitrites out of food because "the amounts of nitrosamines formed in the stomach are larger than what you get from preformed nitrosamines."

FDA will begin its testing program of all products containing malt by the first of the year. The agency's director of the bureau of foods, Sanford Miller, thinks "malt vinegars might contain rather large amounts (of nitrosamines) amounts like those found in malt beverages." But he also predicted that they "would discover virtually no nitrosamines (in the other products) because the amounts used are so small."

Whether or not it is unwise to eat or drink these malt-containing products remains unknown.