The scientist who concluded that sodium nitrite causes cancer in rats called yesterday for go-slow policy in removing the chemical from the nation's meats.
Dr. Paul Newberne of Massachusetts Institute of Technology said in an interview that his research "definitely" should be confirmed in other animals before any extensive ban goes into effect.
Food and Drug Administration officials said yesterday there are no current plans for more tests, though Newberne's report has been in the agency's hands since June 5 and, according to Newberne, further animal testing will take "three to four years."
The Newberne report and a resulting federal plan to begin removing nitrite from meats sometime next year have aroused huge fears in U.S. agriculture.
"The meat industry, especially the pork sector, is convinced removal of nitrites would result in their economic ruin," a Senate Agriculture Committee staff report says.
It was in a $500,000, four-year study commissioned by FDA that Newberne, professor of nutrition and food science, found that one rat in eight fed sodium nitrite developed a lymphoma or lymph cancer, and another one in nice developed a possibly precancerous condition.
The findings led FDA and the Agriculture Department this month to prepare proposed regulations, to be issued this fall, calling for a gradual phrase-out over "several years" of all nitrites in foods.
A 49-page FDA-USDA "action" plan and summary of the nitrite issue state that the Newberne study "shows that nitrite induces cancer when ingested by laboratory rats."
An examination of the study - made available by the government last Friday - shows that it is more tentative. Newberne calls the effect of nitrite "adverse" under "the conditions of the study."
Later in the report, however, he speaks in a summary of "the somewhat less than compelling case that nitrite is lymphanogenic in Sprague-Dawley rats," the strain be used. And he says: "While these observations require some consideration, the data are only suggestive . . . There are suggestions, however, of sufficient magnitude . . . to raise questions about the widespread use of relatively high concentrations [of nitrite] in our food supply."
The upshot, he said yesterday, is that his report has raised a serious "red flag" about nitrites, but he also thinks more animal tests - in other species of rats and in mice, hamsters or other animals - are needed. It is unlikely "but always possible," he said, that an effect may be seen only in one strain.
At the same time, he said, he agrees with the USDA-FDA phase-out plan so long as it starts with products where nitrites are not needed to prevent botulism and are used only to enhance color and appearance. In some such cases - and in cases where alternative anti-botulism measures are possible - action might be "fairly quick," he said.
But any "precipitous" action is unwarranted, he said, and a "total" phase-out should be regarded as "goal" that can be reached only if other safe preserving methods are perfected for the two-thirds of all pork and one-tenth of all beef that is now treated with nitrite.
He said it may "never" be possible to remove nitrite from some products. This is particularly true, he said, for canned hams and possibly some lunch meats, since without nitrite they would have to be so overcooked that "no one would eat them," and freezing - one possible alternative method of preservation - might prove too expensive.
Assistant Agriculture Secretary Carol Foreman yesterday defended the FDA-USDA phase-out plan as "a rational one" that would be implemenced only in steps, as feasible.
As for more animal tests, FDA toxicologist Hyman Gittes said, "I don't know of any being planned at this stage. I don't know how you would start to plan anything until the (Newberne) study is evaluated in some detail."
"It's too soon to say whether more studies will be needed," but FDA is "eliciting scientific review," to find out, said FDA public affairs officer Nancy Glick.
USDA already has moved to reduce the levels of nitrite and nitrosamines (products of nitrites) in bacon. The evidence that nitrosamines cause some animal cancers is "very strong, in fact, not even debatable," Newberne said, "so we ought to start eliminating nitrite on the basis of that alone."