MUTAGENS FROM HEATED CHINESE AND US COOKING OILS

Background: The lung cancer incidence in Chinese women is among the hi ghest in the world, but tobacco smoking accounts for only a minority o f the cancers. Epidemiologic investigations of lung cancer among Chine se women have implicated exposure to indoor air pollution from wok coo king, where the volatile emissions from unrefined cooking oils are mut agenic. Purpose: This study was conducted to identify and quantify the potentially mutagenic substances emitted from a variety of cooking oi ls heated to the temperatures typically used in wok cooking. Methods: Several cooking oils and fatty acids were heated in a wok to boiling, at temperatures (for the cooking oils) that ranged from 240 degrees C to 280 degrees C (typical cooking temperatures in Shanghai, China). Th e oils tested were unrefined Chinese rapeseed, refined U.S. rapeseed ( known as canola). Chinese soybean, and Chinese peanut in addition to l inolenic, linoleic, and erucic fatty acids. Condensates of the emissio ns were collected and tested in the Salmonella mutation assay (using S almonella typhimurium tester strains TA98 and TA104). Volatile decompo sition products also were subjected to gas chromatography and mass spe ctroscopy. Aldehydes were detected using high-performance liquid chrom atography and UV spectroscopy. Results: 1,3-Butadiene, benzene, acrole in, formaldehyde, and other related compounds were qualitatively and q uantitatively detected, with emissions tending to be highest for unref ined Chinese rapeseed oil and lowest for peanut oil. The emission of 1 ,3-butadiene and benzene was approximately 22-fold and 12-fold higher, respectively, from heated unrefined Chinese rapeseed oil than from he ated peanut oil. Lowering the cooking temperatures or adding an antiox idant, such as butylated hydroxyanisole, before cooking decreased the amount of these volatile emissions. Among the individual fatty acids t ested, heated linolenic acid produced the greatest quantities of 1,3-b utadiene, benzene, and acrolein. Separately, the mutagenicity of indiv idual volatile emission condensates was correlated with linolenic acid content (r = .83; P = .0004). Condensates from heated linolenic acid, but not linoleic or erucic acid, were highly mutagenic. Conclusions: These studies, combined with experimental and epidemiologic findings, suggest that high-temperature wok cooking with unrefined Chinese rapes eed oil may increase lung cancer risk. This study indicates methods th at may reduce that risk, Implications: The common use of wok cooking i n China might be an important but controllable risk factor in the etio logy of lung cancer. In the United States, where cooking oils are usua lly refined for purity, additional studies should be conducted to furt her quantify the potential risks of such methods of cooking.