Meaty carcinogens: a risk to the cook?

Grilling meat fosters the formation of potentially cancer-causing heterocyclic amines (HCAs). To date, most investigations of the health risks posed by these compounds have focused on ingestion as the primary route of human exposure. But new research indicates that inhaling the aromatic vapors emitted by grilling steaks, burgers, chicken, and chops could serve as an alternative route of exposure for some people -- even those who don't eat meat.

Herve P. Thiebaud of the University of California, Davis, and his colleagues fried 20 3.5-ounce hamburgers for 6 minutes on each side in nonstick pans. Exhaust systems collected the greasy fumes. Afterward, the researchers analyzed separately samples of the burgers and their trapped vapors for the seven most common HCAs.

A compound known as PhIP accounted for 62 percent (by weight) of the burgers' HCAs, the scientists report in the just-released July JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY. Though PhIP is far from the most potent HCA, calculations by team members at Lawrence Livermore (Calif.) National Laboratory indicate that because the chemistry of cooking meat overwhelmingly favors the production of PhIP, this compound accounts for nearly half the cancer risk to humans posed by HCAs (SN: 4/23/94, p.264).

A less potent HCA predominated in a condensate of the cooking meat's fumes. Known as A[alpha]C, it represented 57 percent of the HCAs present. That very different ratios of the seven HCAs might develop in meat and its smoke extract came as quite a surprise, notes analytical chemist Mark G. Knize, one of Thiebaud's collaborators at Livermore. Because the temperature at which most HCAs form is too low to transform them into a gas, he explains, scientists have assumed that HCAs would "volatilize" by hitching a ride on passing water or fat molecules. But in that case, he says, "You'd expect the ratios to be [comparable]--and they weren't." His group is now focusing more of its attention on resolving why A[alpha]C perferentially escapes.

The data suggest that airborne HCAs, if they pose a risk at all, will be the greatest threat to those who fry a lot of meat, such as many short-order cooks, according to these California-based researchers.

Thiebaud's team found that the quantity of HCAs in a gram of fried meat was about three times as mutagenic (a rough gauge of its carcinogenicity) as the quantity of HCAs in fumes emitted by that gram of meat. As a result, Knize now suspects that for most people, eating meats--not cooking them--will pose the greatest risk from HCAs.