Mutagens from heated Chinese and US cooking oils
BACKGROUND: The lung cancer incidence in Chinese women is among the highest in the world, but tobacco smoking accounts for only a minority of the cancers. Epidemiologic investigations of lung cancer among Chinese women have implicated exposure to indoor air pollution from wok cooking, where the volatile emissions from unrefined cooking oils are mutagenic.
PURPOSE: This study was conducted to identify and quantify the potentially mutagenic substances emitted from a variety of cooking oils 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 °C to 280 °C (typical cooking temperatures in Shanghai, China). The oils tested were unrefined Chinese rapeseed, refined U.S. rapeseed (known as canola), Chinese soybean, and Chinese peanut in addition to linolenic, linoleic, and erucic fatty acids. Condensates of the emissions were collected and tested in the Salmonella mutation assay (using Salmonella typhimurium tester strains TA98 and TA104). Volatile decomposition products also were subjected to gas chromatography and mass spectroscopy. Aldehydes were detected using high-performance liquid chromatography and UV spectroscopy.
RESULTS: 1,3-Butadiene, benzene, acrolein, formaldehyde, and other related compounds were qualitatively and quantitatively detected, with emissions tending to be highest for unrefined 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 heated peanut oil. Lowering the cooking temperatures or adding an antioxidant, such as butylated hydroxyanisole, beforisk.
IMPLICATIONS: The common use of wok cooking in China might be an important but controllable risk factor in the etiology of lung cancer. In the United States, where cooking oils are usually refined for purity, additional studies should be conducted to further quantify the potential risks of such methods of cooking. [J Natl Cancer Inst 87:836–841, 1995]