Meat Gets a Grilling: Is It Safe to Eat? : Health: Chemicals produced during the barbecuing of some meats have damaged genetic material and are carcinogenic in lab tests, some scientists say.

Just when you thought it was safe to go back to the barbecue--bundling your steaks in aluminum foil and keeping fat far from the flames--scientists are surfacing like party poopers with more bad news about grilled meat and cancer.

The latest worry is a class of chemicals produced during the cooking of muscle meats like beef, pork, chicken and fish. In laboratory tests and animal studies, the chemicals have been found to damage genetic material and to be carcinogenic.

Their effects on humans are not well understood, and scientists are undecided on how big a risk they pose. But some suspect that the chemicals in certain cooked meats may be increasing the number of cancers in the United States by up to 7,000 cases a year.

“We don’t know the magnitude of the risk . . . but it is certainly more of a risk than the majority of pesticides which have been banned by the Environmental Protection Agency,” says Richard H. Adamson, director of cancer etiology at the U.S. National Cancer Institute.

There are, however, precautions that meat-eaters can take. The most obvious, and most drastic, is cutting down on cooked meats. Short of that, scientists recommend a range of culinary maneuvers that can limit the chemicals produced.

Adamson, for example, microwaves his meats before grilling. That allows juice and fat to run off, carrying with them certain offending components. It also enables him to minimize grilling time, thus reducing the amount of chemicals produced.

Michael W. Pariza, director of the Food Research Institute at the University of Wisconsin in Madison, is a little more laissez-faire . He avoids cooking steaks directly over flames and prefers meat medium-rare. Beyond that, he does not worry.

“From my own standpoint, if you’re going to a picnic, the risk if you’re having a beer and going to drive . . . is probably a lot greater than the risk from the bratwurst or chicken,” says Pariza, a microbiologist specializing in diet and cancer.

As many as a third of cancer deaths in the United States appear to be related to diet, experts say. That’s at least as many as can be traced to tobacco. But precisely what it is in people’s diets that promotes or deters cancer is not known.

One prime suspect is animal fat. Studies have found high rates of colon cancer among heavy eaters of red meat--an observation that has led some scientists to focus their attention on meat and the various ways it is cooked.

In the late 1960s, researchers discovered the bane of barbecuers, benzopyrene, a carcinogen produced by incomplete combustion. Generated when fat drips into fire, benzopyrene is carried back upward in smoke and deposited on the cooking meat.

To control that problem, nutritionists recommended wrapping meats in foil or grilling them away from direct fire.

As concern about fat in the American diet has increased, experts have promoted lean meats and cuts trimmed of fat.

“We assumed that the major problem was due to fat dripping onto the hot coals and becoming incinerated,” says Pariza, a microbiologist. “So to solve that, you simply find some way of keeping fat from coming directly into contact with the fire.”

But in the mid-1970s, Japanese scientists began testing heavily grilled and blackened food using a new test for mutagenesis, the capacity of certain compounds to cause mutations in cells by altering their genetic structure.

Pariza says the Japanese found levels of mutagenic activity far higher than what could be explained by the presence of benzopyrene. Since then, researchers have identified a new class of so-called mutagens formed from burning protein and amino acids in meat.

The chemicals, called heterocyclic aromatic amines (HAAs), are produced in muscle meats but not in organ meats, during most types of cooking. They form when amino acids in protein and a chemical called creatinine in muscles react at temperatures higher than 212 degrees Fahrenheit.

So far, 17 such chemicals have been identified. About half are in foods commonly eaten in the United States. One of the most worrisome, a compound called PhIP, has been found to cause lymphomas in mice and mammary, and large-intestine tumors in rats.

In monkeys, federal researchers studying the effects of three of the compounds have found that they are absorbed into the monkeys’ bodies from food. Most of what is absorbed becomes carcinogenic; very little is excreted unchanged.

It remains unclear, however, how humans might be affected by HAAs. One study suggests that humans metabolize the compounds the same as monkeys; that is, most of the compounds produced in cooking are absorbed into the body.

For now, researchers are reluctant to offer precise risk estimates. It is possible, extrapolating from animal studies, to estimate roughly how much a diet heavy in HAAs might increase a person’s risk of cancer. Using such calculations, researchers have come up with a range of estimates of the chemicals’ effect on cancer rates.

In general, federal regulators become concerned when a chemical is believed to cause at least one additional cancer per one million people over a lifetime of exposure. The preliminary estimates on HAAs range from one per million to one per thousand.

Adamson, of the National Cancer Institute, estimates the risk at close to 2,000 cases per one million population. If he is correct, the chemicals produced in cooking meat may be responsible for about 7,000 U. S. cancer cases every year.

“This is 1,000 times more of a risk than Alar was,” Adamson says, referring to the controversial growth regulating chemical whose use on apples and other foods began being phased out in 1989 after a public outcry over its links to cancer.

A similar comparison came from James Felton, a biochemist at Lawrence Livermore National Laboratory, who has spent much of the last 12 years studying HAAs and is involved in a study aimed at estimating amounts consumed in the U.S. diet.

“A lot of the pesticides that we regulate at one in a million, I think these are worse than those,” says Felton, section leader for molecular biology in the lab’s biochemical sciences division. “So we’re dealing with a risk worse than most pesticides.”

Felton and others hasten to point out that one can minimize one’s exposure--not only by cutting down on meat but by changing the way one cooks, since the amount of chemicals generated depends on how long and how hot a piece of meat is cooked.